httpsig: add RFC 9421 HTTP Message Signatures support

Add support for signing outgoing HTTP requests per RFC 9421 using Ed25519 or HMAC-SHA256 algorithms. New libcurl options: - CURLOPT_HTTPSIG: signing algorithm ("ed25519" or "hmac-sha256") - CURLOPT_HTTPSIG_KEY: path to hex-encoded key file - CURLOPT_HTTPSIG_KEYID: key identifier for Signature-Input - CURLOPT_HTTPSIG_HEADERS: space-separated components to sign New CLI flags: --httpsig, --httpsig-key, --httpsig-keyid, --httpsig-headers The crypto layer follows the sha256.c multi-backend pattern with implementations for OpenSSL (EVP_DigestSign) and wolfSSL (wc_ed25519_sign_msg). HMAC-SHA256 uses the existing Curl_hmacit() infrastructure which works on all backends. Verified by test 5000 to 5021 Assisted-by: Daniel Stenberg Signed-off-by: Sameeh Jubran <sameeh@wolfssl.com> Closes #22386 Closes #21239
2026-07-27 22:43:12 +03:00 · 2026-07-24 22:49:52 +02:00 · 2026-07-24 22:49:52 +02:00 · a55731050e
commit a55731050e
parent ebc5212dac
78 changed files with 3192 additions and 10 deletions
--- a/.github/scripts/pyspelling.words
+++ b/.github/scripts/pyspelling.words
@ -368,6 +368,9 @@ httpget
 HttpGet
 HTTPS
 https
+httpsig
+HTTPSIG
+CURLHTTPSIG
 HTTPSRR
 hyper's
 IANA
@ -428,6 +431,7 @@ KDE
 keepalive
 Keil
 kerberos
+keyid
 Keychain
 keychain
 KiB
@ -996,6 +1000,7 @@ WinIDN
 WinLDAP
 winsock
 Wireshark
+wolfCrypt
 wolfSSH
 wolfSSL
 ws
--- a/.github/workflows/linux.yml
+++ b/.github/workflows/linux.yml
@ -200,7 +200,7 @@ jobs:
            install_steps: wolfssl-opensslextra-arm
            tflags: '--min=815 1 to 1000'
            LDFLAGS: -Wl,-rpath,/home/runner/wolfssl-opensslextra/lib
-            configure: --with-wolfssl=/home/runner/wolfssl-opensslextra --enable-ech --enable-debug
+            configure: --with-wolfssl=/home/runner/wolfssl-opensslextra --enable-ech --enable-debug --enable-httpsig

          - name: 'wolfssl-opensslextra valgrind 2'
            image: ubuntu-26.04-arm
@ -208,7 +208,7 @@ jobs:
            install_steps: wolfssl-opensslextra-arm
            tflags: '--min=835 1001 to 9999'
            LDFLAGS: -Wl,-rpath,/home/runner/wolfssl-opensslextra/lib
-            configure: --with-wolfssl=/home/runner/wolfssl-opensslextra --enable-ech --enable-debug
+            configure: --with-wolfssl=/home/runner/wolfssl-opensslextra --enable-ech --enable-debug --enable-httpsig

          - name: 'openssl default'
            install_steps: pytest
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@ -435,6 +435,8 @@ option(CURL_DISABLE_NEGOTIATE_AUTH "Disable negotiate authentication" OFF)
 mark_as_advanced(CURL_DISABLE_NEGOTIATE_AUTH)
 option(CURL_DISABLE_AWS "Disable aws-sigv4" OFF)
 mark_as_advanced(CURL_DISABLE_AWS)
+option(CURL_DISABLE_HTTPSIG "Disable HTTP Message Signatures (RFC 9421)" ON)
+mark_as_advanced(CURL_DISABLE_HTTPSIG)
 option(CURL_DISABLE_DICT "Disable DICT" OFF)
 mark_as_advanced(CURL_DISABLE_DICT)
 option(CURL_DISABLE_DOH "Disable DNS-over-HTTPS" OFF)
@ -2037,6 +2039,7 @@ curl_add_if("SSPI"          USE_WINDOWS_SSPI)
 curl_add_if("GSS-API"       HAVE_GSSAPI)
 curl_add_if("alt-svc"       NOT CURL_DISABLE_ALTSVC)
 curl_add_if("HSTS"          NOT CURL_DISABLE_HSTS)
+curl_add_if("HTTPSIG"       NOT CURL_DISABLE_HTTPSIG)
 curl_add_if("SPNEGO"        NOT CURL_DISABLE_NEGOTIATE_AUTH AND
                            (HAVE_GSSAPI OR USE_WINDOWS_SSPI))
 curl_add_if("Kerberos"      NOT CURL_DISABLE_KERBEROS_AUTH AND
--- a/configure.ac
+++ b/configure.ac
@ -4566,6 +4566,29 @@ AS_HELP_STRING([--disable-aws],[Disable AWS sig support]),
    AC_MSG_RESULT(yes)
 )

+dnl ************************************************************
+dnl disable httpsig (RFC 9421)
+dnl
+AC_MSG_CHECKING([whether to enable HTTP Message Signatures (RFC 9421)])
+AC_ARG_ENABLE(httpsig,
+AS_HELP_STRING([--enable-httpsig],[Enable HTTP Message Signatures support])
+AS_HELP_STRING([--disable-httpsig],[Disable HTTP Message Signatures support (default)]),
+[ case "$enableval" in
+  no)
+    AC_MSG_RESULT(no)
+    AC_DEFINE(CURL_DISABLE_HTTPSIG, 1, [to disable HTTP Message Signatures support])
+    want_httpsig="no"
+    ;;
+  *)
+    AC_MSG_RESULT(yes)
+    want_httpsig="yes"
+    ;;
+  esac ],
+    AC_MSG_RESULT(no)
+    AC_DEFINE(CURL_DISABLE_HTTPSIG, 1, [to disable HTTP Message Signatures support])
+    want_httpsig="no"
+)
+
 dnl ************************************************************
 dnl disable NTLM support
 dnl
@ -5313,6 +5336,11 @@ if test "$want_httpsrr" != "no"; then
  SUPPORT_FEATURES="$SUPPORT_FEATURES HTTPSRR"
 fi

+if test "$want_httpsig" = "yes"; then
+  SUPPORT_FEATURES="$SUPPORT_FEATURES HTTPSIG"
+  experimental="$experimental HTTPSIG"
+fi
+
 if test "$SSLS_EXPORT_ENABLED" = "1"; then
  SUPPORT_FEATURES="$SUPPORT_FEATURES SSLS-EXPORT"
 fi
--- a/docs/CURL-DISABLE.md
+++ b/docs/CURL-DISABLE.md
@ -42,6 +42,10 @@ Disable support for the negotiate authentication methods.

 Disable **aws-sigv4** support.

+## `CURL_DISABLE_HTTPSIG`
+
+Disable RFC 9421 HTTP Message Signatures support.
+
 ## `CURL_DISABLE_CA_SEARCH`

 Disable unsafe CA bundle search in PATH on Windows.
--- a/docs/EXPERIMENTAL.md
+++ b/docs/EXPERIMENTAL.md
@ -105,3 +105,22 @@ Graduation requirements:
 - HTTPS records can control ALPN and port number, at least

 - There are options to control HTTPS use
+
+## HTTP Message Signatures (RFC 9421)
+
+Sign outgoing HTTP requests according to RFC 9421 using the
+`--httpsig-algo`, `--httpsig-key`, `--httpsig-keyid` and
+`--httpsig-headers` command line options, or the corresponding
+`CURLOPT_HTTPSIG_*` libcurl options. Built only when configured with
+`--enable-httpsig`.
+
+Graduation requirements:
+
+- the option set (names, arguments, defaults) is settled
+
+- interoperability has been verified against at least two independent
+  RFC 9421 implementations
+
+- no test cases are disabled for the feature
+
+- feedback from users saying the API works for their use cases
--- a/docs/cmdline-opts/.gitignore
+++ b/docs/cmdline-opts/.gitignore
@ -3,3 +3,4 @@
 # SPDX-License-Identifier: curl

 curl.txt
+asciipage.tmp.*
--- a/docs/cmdline-opts/Makefile.inc
+++ b/docs/cmdline-opts/Makefile.inc
@ -134,6 +134,10 @@ DPAGES = \
  http2.md \
  http3.md \
  http3-only.md \
+  httpsig-algo.md \
+  httpsig-headers.md \
+  httpsig-key.md \
+  httpsig-keyid.md \
  ignore-content-length.md \
  insecure.md \
  interface.md \
--- a/docs/cmdline-opts/httpsig-algo.md
+++ b/docs/cmdline-opts/httpsig-algo.md
@ -0,0 +1,36 @@
+---
+c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+SPDX-License-Identifier: curl
+Long: httpsig-algo
+Protocols: HTTP
+Arg: <algorithm>
+Help: Algorithm for HTTP Message Signatures
+Category: auth http
+Added: 8.22.0
+Multi: single
+Experimental: yes
+See-also:
+  - httpsig-key
+  - httpsig-keyid
+  - httpsig-headers
+Example:
+  - --httpsig-key key.hex --httpsig-keyid "my-key" $URL
+  - --httpsig-algo hmac-sha256 --httpsig-key secret.hex --httpsig-keyid "shared" $URL
+---
+
+# `--httpsig-algo`
+
+Sign outgoing HTTP requests using RFC 9421 HTTP Message Signatures.
+
+This option specifies which signing algorithm to use. Supported values are
+**ed25519** and **hmac-sha256**. If not specified, **ed25519** is used. Any
+other value causes curl to exit with an error.
+
+HTTP Message Signatures are enabled when any of --httpsig-algo,
+--httpsig-key, --httpsig-keyid or --httpsig-headers is given. When enabled,
+--httpsig-key and --httpsig-keyid are required. Without any of these options
+no signing is performed.
+
+By default, the signed components are `method`, `authority`, `path`, and
+`query` (when a query string is present). Use --httpsig-headers to override
+the set of components included in the signature.
--- a/docs/cmdline-opts/httpsig-headers.md
+++ b/docs/cmdline-opts/httpsig-headers.md
@ -0,0 +1,45 @@
+---
+c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+SPDX-License-Identifier: curl
+Long: httpsig-headers
+Protocols: HTTP
+Arg: <components>
+Help: Components to sign for HTTP Message Signatures
+Category: auth http
+Added: 8.22.0
+Multi: single
+Experimental: yes
+See-also:
+  - httpsig-algo
+  - httpsig-key
+  - httpsig-keyid
+Example:
+  - --httpsig-algo ed25519 --httpsig-key key.hex --httpsig-keyid "my-key" --httpsig-headers "method authority content-type:" $URL
+---
+
+# `--httpsig-headers`
+
+Space-separated list of components to include in the RFC 9421 HTTP Message
+Signature. Derived components are given as bare names: `method`, `authority`,
+`path`, and `query`. HTTP header fields are given with a trailing colon, for
+example `content-type:` and `content-digest:`.
+
+If not specified, the default set is `method authority path` (plus `query`
+when a query string is present in the URL).
+
+## Signing request headers
+
+Header components are taken from `-H` / `--header` options only. Headers curl
+adds by default (such as `User-Agent`) are not signed unless you set them
+explicitly, for example:
+
+    curl --httpsig-algo ed25519 \
+      --httpsig-key k.hex \
+      --httpsig-keyid mykey \
+      -H "User-Agent: MyApp/1.0" \
+      --httpsig-headers \
+      "method authority path user-agent:" \
+      $URL
+
+Each component may appear only once. Duplicate identifiers in
+`--httpsig-headers` cause curl to exit with an error.
--- a/docs/cmdline-opts/httpsig-key.md
+++ b/docs/cmdline-opts/httpsig-key.md
@ -0,0 +1,35 @@
+---
+c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+SPDX-License-Identifier: curl
+Long: httpsig-key
+Protocols: HTTP
+Arg: <file>
+Help: Key file for HTTP Message Signatures
+Category: auth http
+Added: 8.22.0
+Multi: single
+Experimental: yes
+See-also:
+  - httpsig-algo
+  - httpsig-keyid
+Example:
+  - --httpsig-algo ed25519 --httpsig-key key.hex --httpsig-keyid "my-key" $URL
+---
+
+# `--httpsig-key`
+
+Path to the key file used for RFC 9421 HTTP Message Signatures.
+
+The file must contain a hex-encoded key on its first line. For **ed25519**,
+this is the 32-byte private seed (64 hex characters). For **hmac-sha256**,
+this is the shared secret. PEM files are not supported.
+
+## Generating Ed25519 keys
+
+With OpenSSL 3:
+
+    openssl genpkey -algorithm ED25519 -out k.pem
+    openssl pkey -in k.pem -outform RAW -out k.raw
+    xxd -p -c 64 k.raw | tr -d '\n' > k.hex
+
+Use `k.hex` with `--httpsig-key`.
--- a/docs/cmdline-opts/httpsig-keyid.md
+++ b/docs/cmdline-opts/httpsig-keyid.md
@ -0,0 +1,23 @@
+---
+c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+SPDX-License-Identifier: curl
+Long: httpsig-keyid
+Protocols: HTTP
+Arg: <id>
+Help: Key identifier for HTTP Message Signatures
+Category: auth http
+Added: 8.22.0
+Multi: single
+Experimental: yes
+See-also:
+  - httpsig-algo
+  - httpsig-key
+Example:
+  - --httpsig-algo ed25519 --httpsig-key key.hex --httpsig-keyid "my-key" $URL
+---
+
+# `--httpsig-keyid`
+
+The key identifier to include in the `Signature-Input` header when using RFC
+9421 HTTP Message Signatures. This value appears as the `keyid` parameter and
+allows the server to look up the correct verification key.
--- a/docs/libcurl/curl_easy_setopt.md
+++ b/docs/libcurl/curl_easy_setopt.md
@ -474,6 +474,22 @@ See CURLOPT_HTTPPOST(3)

 Tunnel through the HTTP proxy. CURLOPT_HTTPPROXYTUNNEL(3)

+## CURLOPT_HTTPSIG_ALGORITHM
+
+RFC 9421 HTTP Message Signatures algorithm. See CURLOPT_HTTPSIG_ALGORITHM(3)
+
+## CURLOPT_HTTPSIG_HEADERS
+
+Components to sign for HTTP Message Signatures. See CURLOPT_HTTPSIG_HEADERS(3)
+
+## CURLOPT_HTTPSIG_KEY
+
+Hex-encoded key for HTTP Message Signatures. See CURLOPT_HTTPSIG_KEY(3)
+
+## CURLOPT_HTTPSIG_KEYID
+
+Key identifier for HTTP Message Signatures. See CURLOPT_HTTPSIG_KEYID(3)
+
 ## CURLOPT_HTTP_CONTENT_DECODING

 Disable Content decoding. See CURLOPT_HTTP_CONTENT_DECODING(3)
--- a/docs/libcurl/curl_version_info.md
+++ b/docs/libcurl/curl_version_info.md
@ -232,6 +232,13 @@ HTTP/3 and QUIC support are built-in (Added in 7.66.0)

 libcurl was built with support for HTTPS-proxy.

+## `HTTPSIG`
+
+*features* mask bit: non-existent
+
+libcurl was built with support for RFC 9421 HTTP Message Signatures (Added in
+8.22.0)
+
 ## `HTTPSRR`

 *features* mask bit: non-existent
--- a/docs/libcurl/opts/CURLOPT_HTTPAUTH.md
+++ b/docs/libcurl/opts/CURLOPT_HTTPAUTH.md
@ -118,6 +118,11 @@ single auth algorithm is acceptable.
 provides AWS V4 signature authentication on HTTPS header
 see CURLOPT_AWS_SIGV4(3).

+## CURLAUTH_HTTPSIG
+
+provides RFC 9421 HTTP Message Signatures on outgoing requests,
+see CURLOPT_HTTPSIG_ALGORITHM(3).
+
 # DEFAULT

 CURLAUTH_BASIC
@ -158,6 +163,8 @@ CURLAUTH_AWS_SIGV4 was added in 7.74.0

 CURLAUTH_DIGEST_IE does nothing since 8.21.0

+CURLAUTH_HTTPSIG was added in 8.22.0
+
 # %AVAILABILITY%

 # RETURN VALUE
--- a/docs/libcurl/opts/CURLOPT_HTTPSIG_ALGORITHM.md
+++ b/docs/libcurl/opts/CURLOPT_HTTPSIG_ALGORITHM.md
@ -0,0 +1,89 @@
+---
+c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+SPDX-License-Identifier: curl
+Title: CURLOPT_HTTPSIG_ALGORITHM
+Section: 3
+Source: libcurl
+See-also:
+  - CURLOPT_HTTPSIG_HEADERS (3)
+  - CURLOPT_HTTPSIG_KEY (3)
+  - CURLOPT_HTTPSIG_KEYID (3)
+  - CURLOPT_HTTPAUTH (3)
+Protocol:
+  - HTTP
+Added-in: 8.22.0
+---
+
+# NAME
+
+CURLOPT_HTTPSIG_ALGORITHM - RFC 9421 HTTP Message Signatures algorithm
+
+# SYNOPSIS
+
+~~~c
+#include <curl/curl.h>
+
+CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HTTPSIG_ALGORITHM,
+                          long algorithm);
+~~~
+
+# DESCRIPTION
+
+This feature is **experimental** and may change before it is considered
+stable. We advise against using it in production.
+
+Enable RFC 9421 HTTP Message Signatures on outgoing requests. Pass a long
+set to one of the values below to select the signing algorithm.
+
+## CURLHTTPSIG_NONE (0)
+
+Disable HTTP Message Signatures.
+
+## CURLHTTPSIG_ED25519 (1)
+
+Sign with Ed25519 (RFC 8032). Requires a TLS backend with Ed25519 support.
+
+## CURLHTTPSIG_HMAC_SHA256 (2)
+
+Sign with HMAC-SHA256.
+
+##
+
+Setting this option to a non-zero value also sets CURLOPT_HTTPAUTH(3) to
+CURLAUTH_HTTPSIG. The options CURLOPT_HTTPSIG_KEY(3) and
+CURLOPT_HTTPSIG_KEYID(3) must also be set.
+
+# DEFAULT
+
+CURLHTTPSIG_NONE (0)
+
+# %PROTOCOLS%
+
+# EXAMPLE
+
+~~~c
+int main(void)
+{
+  CURL *curl = curl_easy_init();
+
+  if(curl) {
+    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/api");
+    curl_easy_setopt(curl, CURLOPT_HTTPSIG_ALGORITHM,
+                     CURLHTTPSIG_ED25519);
+    curl_easy_setopt(curl, CURLOPT_HTTPSIG_KEY,
+                     "9f8362f87a484a954e6e740c5b4c0e84"
+                     "229139a20aa8ab56ff66586f6a7d29c5");
+    curl_easy_setopt(curl, CURLOPT_HTTPSIG_KEYID, "my-key-id");
+    curl_easy_perform(curl);
+  }
+}
+~~~
+
+# %AVAILABILITY%
+
+# RETURN VALUE
+
+curl_easy_setopt(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).
--- a/docs/libcurl/opts/CURLOPT_HTTPSIG_HEADERS.md
+++ b/docs/libcurl/opts/CURLOPT_HTTPSIG_HEADERS.md
@ -0,0 +1,108 @@
+---
+c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+SPDX-License-Identifier: curl
+Title: CURLOPT_HTTPSIG_HEADERS
+Section: 3
+Source: libcurl
+See-also:
+  - CURLOPT_HTTPSIG_ALGORITHM (3)
+  - CURLOPT_HTTPSIG_KEY (3)
+  - CURLOPT_HTTPSIG_KEYID (3)
+Protocol:
+  - HTTP
+Added-in: 8.22.0
+---
+
+# NAME
+
+CURLOPT_HTTPSIG_HEADERS - components to sign for HTTP Message Signatures
+
+# SYNOPSIS
+
+~~~c
+#include <curl/curl.h>
+
+CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HTTPSIG_HEADERS,
+                          char *components);
+~~~
+
+# DESCRIPTION
+
+This feature is **experimental** and may change before it is considered
+stable. We advise against using it in production.
+
+Pass a space-separated list of component identifiers to include in the
+RFC 9421 HTTP Message Signature.
+
+Derived components are given as bare names:
+
+- **method** - the HTTP method (GET, POST, etc.)
+- **authority** - the host and optional port
+- **path** - the request path
+- **query** - the query string including the leading `?`
+
+HTTP header fields are given with a trailing colon, for example `content-type:`
+or `content-digest:`. This mirrors how a header looks and keeps a leading `@`
+free for its usual curl meaning (read the value from a file).
+
+If this option is not set, the default components are **method**, **authority**,
+**path** (plus **query** when a query string is present).
+
+## Signing request headers
+
+Header components are resolved from the list set with CURLOPT_HTTPHEADER(3)
+only. Headers that libcurl adds later (such as the default `User-Agent`) are
+**not** visible to the signer unless the application supplies them explicitly.
+
+To sign `User-Agent`, supply it via CURLOPT_HTTPHEADER(3) together with this
+option before the transfer; see EXAMPLE.
+
+Each component identifier may appear at most once (RFC 9421 Section 2).
+Listing the same component twice returns `CURLE_BAD_FUNCTION_ARGUMENT`.
+
+At most 16 components are accepted; supplying more returns
+`CURLE_BAD_FUNCTION_ARGUMENT`.
+
+The application does not have to keep the string around after setting this
+option.
+
+# DEFAULT
+
+NULL (uses the default component set)
+
+# %PROTOCOLS%
+
+# EXAMPLE
+
+~~~c
+int main(void)
+{
+  CURL *curl = curl_easy_init();
+  struct curl_slist *headers = NULL;
+
+  if(curl) {
+    headers = curl_slist_append(headers, "User-Agent: MyApp/1.0");
+    curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
+    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/api");
+    curl_easy_setopt(curl, CURLOPT_HTTPSIG_ALGORITHM,
+                     CURLHTTPSIG_ED25519);
+    curl_easy_setopt(curl, CURLOPT_HTTPSIG_KEY,
+                     "9f8362f87a484a954e6e740c5b4c0e84"
+                     "229139a20aa8ab56ff66586f6a7d29c5");
+    curl_easy_setopt(curl, CURLOPT_HTTPSIG_KEYID, "my-key-id");
+    curl_easy_setopt(curl, CURLOPT_HTTPSIG_HEADERS,
+                     "method authority path content-type: user-agent:");
+    curl_easy_perform(curl);
+    curl_slist_free_all(headers);
+  }
+}
+~~~
+
+# %AVAILABILITY%
+
+# RETURN VALUE
+
+curl_easy_setopt(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).
--- a/docs/libcurl/opts/CURLOPT_HTTPSIG_KEY.md
+++ b/docs/libcurl/opts/CURLOPT_HTTPSIG_KEY.md
@ -0,0 +1,90 @@
+---
+c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+SPDX-License-Identifier: curl
+Title: CURLOPT_HTTPSIG_KEY
+Section: 3
+Source: libcurl
+See-also:
+  - CURLOPT_HTTPSIG_ALGORITHM (3)
+  - CURLOPT_HTTPSIG_KEYID (3)
+Protocol:
+  - HTTP
+Added-in: 8.22.0
+---
+
+# NAME
+
+CURLOPT_HTTPSIG_KEY - hex-encoded key for HTTP Message Signatures
+
+# SYNOPSIS
+
+~~~c
+#include <curl/curl.h>
+
+CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HTTPSIG_KEY, char *key);
+~~~
+
+# DESCRIPTION
+
+This feature is **experimental** and may change before it is considered
+stable. We advise against using it in production.
+
+Pass a null-terminated string containing the hex-encoded private key or
+shared secret used for RFC 9421 HTTP Message Signatures.
+
+For **ed25519**, this is the 32-byte private seed (64 hex characters). For
+**hmac-sha256**, this is the shared secret as hex; the decoded length is half
+the number of hex digits, up to `CURL_MAX_INPUT_LENGTH / 2` bytes (the same
+upper bound as other libcurl string options).
+
+PEM and other encodings are not supported; pass the raw key material as hex.
+
+## Generating Ed25519 keys
+
+With OpenSSL 3:
+
+    openssl genpkey -algorithm ED25519 -out ed25519.pem
+    openssl pkey -in ed25519.pem -outform RAW | xxd -p -c 64 | tr -d '\n' > key.hex
+
+The `key.hex` file is one line of 64 hexadecimal digits.
+
+The application does not have to keep the string around after setting this
+option.
+
+Using this option multiple times makes the last set string override the
+previous ones. Set it to NULL to disable its use again.
+
+# DEFAULT
+
+NULL
+
+# %PROTOCOLS%
+
+# EXAMPLE
+
+~~~c
+int main(void)
+{
+  CURL *curl = curl_easy_init();
+
+  if(curl) {
+    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/api");
+    curl_easy_setopt(curl, CURLOPT_HTTPSIG_ALGORITHM,
+                     CURLHTTPSIG_ED25519);
+    curl_easy_setopt(curl, CURLOPT_HTTPSIG_KEY,
+                     "9f8362f87a484a954e6e740c5b4c0e84"
+                     "229139a20aa8ab56ff66586f6a7d29c5");
+    curl_easy_setopt(curl, CURLOPT_HTTPSIG_KEYID, "my-key-id");
+    curl_easy_perform(curl);
+  }
+}
+~~~
+
+# %AVAILABILITY%
+
+# RETURN VALUE
+
+curl_easy_setopt(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).
--- a/docs/libcurl/opts/CURLOPT_HTTPSIG_KEYID.md
+++ b/docs/libcurl/opts/CURLOPT_HTTPSIG_KEYID.md
@ -0,0 +1,76 @@
+---
+c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+SPDX-License-Identifier: curl
+Title: CURLOPT_HTTPSIG_KEYID
+Section: 3
+Source: libcurl
+See-also:
+  - CURLOPT_HTTPSIG_ALGORITHM (3)
+  - CURLOPT_HTTPSIG_KEY (3)
+Protocol:
+  - HTTP
+Added-in: 8.22.0
+---
+
+# NAME
+
+CURLOPT_HTTPSIG_KEYID - key identifier for HTTP Message Signatures
+
+# SYNOPSIS
+
+~~~c
+#include <curl/curl.h>
+
+CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HTTPSIG_KEYID, char *keyid);
+~~~
+
+# DESCRIPTION
+
+This feature is **experimental** and may change before it is considered
+stable. We advise against using it in production.
+
+Pass a null-terminated string that identifies the key used for RFC 9421 HTTP
+Message Signatures. This value is included as the `keyid` parameter in the
+`Signature-Input` header, allowing the server to look up the corresponding
+verification key.
+
+The application does not have to keep the string around after setting this
+option.
+
+Using this option multiple times makes the last set string override the
+previous ones. Set it to NULL to disable its use again.
+
+# DEFAULT
+
+NULL
+
+# %PROTOCOLS%
+
+# EXAMPLE
+
+~~~c
+int main(void)
+{
+  CURL *curl = curl_easy_init();
+
+  if(curl) {
+    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/api");
+    curl_easy_setopt(curl, CURLOPT_HTTPSIG_ALGORITHM,
+                     CURLHTTPSIG_ED25519);
+    curl_easy_setopt(curl, CURLOPT_HTTPSIG_KEY,
+                     "9f8362f87a484a954e6e740c5b4c0e84"
+                     "229139a20aa8ab56ff66586f6a7d29c5");
+    curl_easy_setopt(curl, CURLOPT_HTTPSIG_KEYID, "my-key-id");
+    curl_easy_perform(curl);
+  }
+}
+~~~
+
+# %AVAILABILITY%
+
+# RETURN VALUE
+
+curl_easy_setopt(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).
--- a/docs/libcurl/opts/Makefile.inc
+++ b/docs/libcurl/opts/Makefile.inc
@ -227,6 +227,10 @@ man_MANS =                                      \
  CURLOPT_HTTPHEADER.3                          \
  CURLOPT_HTTPPOST.3                            \
  CURLOPT_HTTPPROXYTUNNEL.3                     \
+  CURLOPT_HTTPSIG_ALGORITHM.3                   \
+  CURLOPT_HTTPSIG_HEADERS.3                     \
+  CURLOPT_HTTPSIG_KEY.3                         \
+  CURLOPT_HTTPSIG_KEYID.3                       \
  CURLOPT_IGNORE_CONTENT_LENGTH.3               \
  CURLOPT_INFILESIZE.3                          \
  CURLOPT_INFILESIZE_LARGE.3                    \
--- a/docs/libcurl/symbols-in-versions
+++ b/docs/libcurl/symbols-in-versions
@ -202,6 +202,7 @@ CURLALTSVC_READONLYFILE         7.64.1
 CURLAUTH_ANY                    7.10.6
 CURLAUTH_ANYSAFE                7.10.6
 CURLAUTH_AWS_SIGV4              7.75.0
+CURLAUTH_HTTPSIG                8.22.0
 CURLAUTH_BASIC                  7.10.6
 CURLAUTH_BEARER                 7.61.0
 CURLAUTH_DIGEST                 7.10.6
@ -420,6 +421,9 @@ CURLHEADER_SEPARATE             7.37.0
 CURLHEADER_UNIFIED              7.37.0
 CURLHSTS_ENABLE                 7.74.0
 CURLHSTS_READONLYFILE           7.74.0
+CURLHTTPSIG_ED25519             8.22.0
+CURLHTTPSIG_HMAC_SHA256         8.22.0
+CURLHTTPSIG_NONE                8.22.0
 CURLINFO_ACTIVESOCKET           7.45.0
 CURLINFO_APPCONNECT_TIME        7.19.0
 CURLINFO_APPCONNECT_TIME_T      7.61.0
@ -697,6 +701,10 @@ CURLOPT_HTTPHEADER              7.1
 CURLOPT_HTTPPOST                7.1           7.56.0
 CURLOPT_HTTPPROXYTUNNEL         7.3
 CURLOPT_HTTPREQUEST             7.1           -           7.15.5
+CURLOPT_HTTPSIG_ALGORITHM       8.22.0
+CURLOPT_HTTPSIG_HEADERS         8.22.0
+CURLOPT_HTTPSIG_KEY             8.22.0
+CURLOPT_HTTPSIG_KEYID           8.22.0
 CURLOPT_IGNORE_CONTENT_LENGTH   7.14.1
 CURLOPT_INFILE                  7.1           7.9.7
 CURLOPT_INFILESIZE              7.1
--- a/docs/options-in-versions
+++ b/docs/options-in-versions
@ -98,6 +98,10 @@
 --http2-prior-knowledge              7.49.0
 --http3                              7.66.0
 --http3-only                         7.88.0
+--httpsig-algo                       8.22.0
+--httpsig-headers                    8.22.0
+--httpsig-key                        8.22.0
+--httpsig-keyid                      8.22.0
 --ignore-content-length              7.14.1
 --ip-tos                             8.9.0
 --ipfs-gateway                       8.4.0
--- a/include/curl/curl.h
+++ b/include/curl/curl.h
@ -843,12 +843,20 @@ typedef enum {
 #endif
 #define CURLAUTH_BEARER       (((unsigned long)1) << 6)
 #define CURLAUTH_AWS_SIGV4    (((unsigned long)1) << 7)
+#define CURLAUTH_HTTPSIG      (((unsigned long)1) << 8)
 #define CURLAUTH_ONLY         (((unsigned long)1) << 31)
-#define CURLAUTH_ANY          ((~CURLAUTH_DIGEST_IE) & \
+#define CURLAUTH_ANY          ((~(CURLAUTH_DIGEST_IE |                  \
+                                  CURLAUTH_HTTPSIG)) &                  \
                               ((unsigned long)0xffffffff))
-#define CURLAUTH_ANYSAFE      ((~(CURLAUTH_BASIC | CURLAUTH_DIGEST_IE)) & \
+#define CURLAUTH_ANYSAFE      ((~(CURLAUTH_BASIC | CURLAUTH_DIGEST_IE | \
+                                  CURLAUTH_HTTPSIG)) &                  \
                               ((unsigned long)0xffffffff))

+/* constants for CURLOPT_HTTPSIG_ALGORITHM */
+#define CURLHTTPSIG_NONE          0L
+#define CURLHTTPSIG_ED25519       1L
+#define CURLHTTPSIG_HMAC_SHA256   2L
+
 /* all types supported by server */
 #define CURLSSH_AUTH_ANY       ((unsigned long)0xffffffff)
 #define CURLSSH_AUTH_NONE      0L        /* none allowed, silly but complete */
@ -2266,6 +2274,18 @@ typedef enum {
  /* set TLS supported signature algorithms */
  CURLOPT(CURLOPT_SSL_SIGNATURE_ALGORITHMS, CURLOPTTYPE_STRINGPOINT, 328),

+  /* RFC 9421 HTTP Message Signatures algorithm */
+  CURLOPT(CURLOPT_HTTPSIG_ALGORITHM, CURLOPTTYPE_VALUES, 329),
+
+  /* Hex-encoded key for HTTP Message Signatures */
+  CURLOPT(CURLOPT_HTTPSIG_KEY, CURLOPTTYPE_STRINGPOINT, 330),
+
+  /* Key identifier for HTTP Message Signatures */
+  CURLOPT(CURLOPT_HTTPSIG_KEYID, CURLOPTTYPE_STRINGPOINT, 331),
+
+  /* Space-separated list of components to sign for HTTP Message Signatures */
+  CURLOPT(CURLOPT_HTTPSIG_HEADERS, CURLOPTTYPE_STRINGPOINT, 332),
+
  CURLOPT_LASTENTRY /* the last unused */
 } CURLoption;

--- a/include/curl/typecheck-gcc.h
+++ b/include/curl/typecheck-gcc.h
@ -496,6 +496,9 @@ CURLWARNING(Wcurl_easy_getinfo_err_curl_off_t,
   (option) == CURLOPT_USERAGENT ||                                     \
   (option) == CURLOPT_USERNAME ||                                      \
   (option) == CURLOPT_AWS_SIGV4 ||                                     \
+   (option) == CURLOPT_HTTPSIG_HEADERS ||                               \
+   (option) == CURLOPT_HTTPSIG_KEY ||                                   \
+   (option) == CURLOPT_HTTPSIG_KEYID ||                                 \
   (option) == CURLOPT_USERPWD ||                                       \
   (option) == CURLOPT_XOAUTH2_BEARER ||                                \
   0)
--- a/lib/Makefile.inc
+++ b/lib/Makefile.inc
@ -222,6 +222,8 @@ LIB_CFILES =         \
  http1.c            \
  http2.c            \
  http_aws_sigv4.c   \
+  http_httpsig.c     \
+  curl_ed25519.c     \
  http_chunks.c      \
  http_digest.c      \
  http_negotiate.c   \
@ -363,6 +365,8 @@ LIB_HFILES =         \
  http1.h            \
  http2.h            \
  http_aws_sigv4.h   \
+  http_httpsig.h     \
+  curl_ed25519.h     \
  http_chunks.h      \
  http_digest.h      \
  http_negotiate.h   \
--- a/lib/curl_config-cmake.h.in
+++ b/lib/curl_config-cmake.h.in
@ -61,6 +61,9 @@
 /* disables aws-sigv4 */
 #cmakedefine CURL_DISABLE_AWS 1

+/* disables HTTP Message Signatures (RFC 9421) */
+#cmakedefine CURL_DISABLE_HTTPSIG 1
+
 /* disables DICT */
 #cmakedefine CURL_DISABLE_DICT 1

--- a/lib/curl_ed25519.c
+++ b/lib/curl_ed25519.c
@ -0,0 +1,170 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ * SPDX-License-Identifier: curl
+ *
+ ***************************************************************************/
+#include "curl_setup.h"
+
+#if !defined(CURL_DISABLE_HTTP) && !defined(CURL_DISABLE_HTTPSIG)
+
+/* Please keep the SSL backend-specific #if branches in this order:
+ *
+ * 1. USE_OPENSSL
+ * 2. USE_WOLFSSL
+ * 3. USE_GNUTLS
+ * 4. USE_MBEDTLS
+ */
+
+#include "curl_ed25519.h"
+
+#ifdef USE_OPENSSL
+#include <openssl/evp.h>
+
+CURLcode Curl_ed25519_sign(const unsigned char *key, size_t keylen,
+                           const unsigned char *msg, size_t msglen,
+                           unsigned char *sig, size_t *siglen)
+{
+  EVP_PKEY *pkey;
+  EVP_MD_CTX *mdctx;
+  size_t slen;
+  int rc;
+
+  if(keylen != CURL_ED25519_KEYLEN)
+    return CURLE_BAD_FUNCTION_ARGUMENT;
+
+  pkey = EVP_PKEY_new_raw_private_key(EVP_PKEY_ED25519, NULL, key, keylen);
+  if(!pkey)
+    return CURLE_AUTH_ERROR;
+
+  mdctx = EVP_MD_CTX_new();
+  if(!mdctx) {
+    EVP_PKEY_free(pkey);
+    return CURLE_OUT_OF_MEMORY;
+  }
+
+  rc = EVP_DigestSignInit(mdctx, NULL, NULL, NULL, pkey);
+  if(rc != 1) {
+    EVP_MD_CTX_free(mdctx);
+    EVP_PKEY_free(pkey);
+    return CURLE_AUTH_ERROR;
+  }
+
+  slen = CURL_ED25519_SIGLEN;
+  rc = EVP_DigestSign(mdctx, sig, &slen, msg, msglen);
+
+  EVP_MD_CTX_free(mdctx);
+  EVP_PKEY_free(pkey);
+
+  if(rc != 1)
+    return CURLE_AUTH_ERROR;
+
+  *siglen = slen;
+  return CURLE_OK;
+}
+
+#elif defined(USE_WOLFSSL)
+#include <wolfssl/options.h>
+#include <wolfssl/wolfcrypt/settings.h>
+#if (defined(HAVE_ED25519) || defined(WOLFSSL_CURVE25519_USE_ED25519)) && \
+    defined(HAVE_ED25519_KEY_IMPORT) && defined(HAVE_ED25519_SIGN)
+#include <wolfssl/wolfcrypt/ed25519.h>
+#include <wolfssl/wolfcrypt/error-crypt.h>
+#include <wolfssl/wolfcrypt/random.h>
+
+CURLcode Curl_ed25519_sign(const unsigned char *key, size_t keylen,
+                           const unsigned char *msg, size_t msglen,
+                           unsigned char *sig, size_t *siglen)
+{
+  int ret;
+  WC_RNG rng;
+  ed25519_key edkey;
+  word32 outlen;
+  unsigned char pubkey[ED25519_PUB_KEY_SIZE];
+
+  if(keylen != ED25519_KEY_SIZE)
+    return CURLE_BAD_FUNCTION_ARGUMENT;
+
+  ret = wc_InitRng(&rng);
+  if(ret)
+    return CURLE_AUTH_ERROR;
+
+  ret = wc_ed25519_init(&edkey);
+  if(ret) {
+    wc_FreeRng(&rng);
+    return CURLE_AUTH_ERROR;
+  }
+
+  ret = wc_ed25519_import_private_only(key, ED25519_KEY_SIZE, &edkey);
+  if(ret)
+    goto fail;
+
+  ret = wc_ed25519_make_public(&edkey, pubkey, ED25519_PUB_KEY_SIZE);
+  if(ret)
+    goto fail;
+
+  ret = wc_ed25519_import_private_key(key, ED25519_KEY_SIZE,
+                                      pubkey, ED25519_PUB_KEY_SIZE, &edkey);
+  if(ret)
+    goto fail;
+
+  outlen = ED25519_SIG_SIZE;
+  ret = wc_ed25519_sign_msg(msg, (word32)msglen, sig, &outlen, &edkey);
+  if(ret)
+    goto fail;
+
+  *siglen = (size_t)outlen;
+  wc_ed25519_free(&edkey);
+  wc_FreeRng(&rng);
+  return CURLE_OK;
+
+fail:
+  wc_ed25519_free(&edkey);
+  wc_FreeRng(&rng);
+  return CURLE_AUTH_ERROR;
+}
+
+#else /* USE_WOLFSSL but no Ed25519 sign/import in this wolfSSL build */
+
+CURLcode Curl_ed25519_sign(const unsigned char *key, size_t keylen,
+                           const unsigned char *msg, size_t msglen,
+                           unsigned char *sig, size_t *siglen)
+{
+  (void)key; (void)keylen; (void)msg; (void)msglen;
+  (void)sig; (void)siglen;
+  return CURLE_NOT_BUILT_IN;
+}
+
+#endif /* wolfSSL Ed25519 */
+
+#else /* no Ed25519-capable backend */
+
+CURLcode Curl_ed25519_sign(const unsigned char *key, size_t keylen,
+                           const unsigned char *msg, size_t msglen,
+                           unsigned char *sig, size_t *siglen)
+{
+  (void)key; (void)keylen; (void)msg; (void)msglen;
+  (void)sig; (void)siglen;
+  return CURLE_NOT_BUILT_IN;
+}
+
+#endif /* Ed25519 backends */
+
+#endif /* !CURL_DISABLE_HTTP && !CURL_DISABLE_HTTPSIG */
--- a/lib/curl_ed25519.h
+++ b/lib/curl_ed25519.h
@ -0,0 +1,44 @@
+#ifndef HEADER_CURL_ED25519_H
+#define HEADER_CURL_ED25519_H
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ * SPDX-License-Identifier: curl
+ *
+ ***************************************************************************/
+#include "curl_setup.h"
+
+#if !defined(CURL_DISABLE_HTTP) && !defined(CURL_DISABLE_HTTPSIG)
+
+#define CURL_ED25519_SIGLEN 64
+#define CURL_ED25519_KEYLEN 32
+
+/* Sign with Ed25519 (RFC 8032).
+ * key/keylen: raw 32-byte private seed
+ * msg/msglen: data to sign
+ * sig: output buffer (at least CURL_ED25519_SIGLEN bytes)
+ * siglen: out - actual signature length on success
+ * Returns CURLE_OK or CURLE_NOT_BUILT_IN if no backend supports Ed25519. */
+CURLcode Curl_ed25519_sign(const unsigned char *key, size_t keylen,
+                           const unsigned char *msg, size_t msglen,
+                           unsigned char *sig, size_t *siglen);
+
+#endif /* !CURL_DISABLE_HTTP && !CURL_DISABLE_HTTPSIG */
+#endif /* HEADER_CURL_ED25519_H */
--- a/lib/curl_hmac.h
+++ b/lib/curl_hmac.h
@ -26,6 +26,7 @@

 #if (defined(USE_CURL_NTLM_CORE) && !defined(USE_WINDOWS_SSPI)) ||    \
  !defined(CURL_DISABLE_AWS) || !defined(CURL_DISABLE_DIGEST_AUTH) || \
+  !defined(CURL_DISABLE_HTTPSIG) ||                                   \
  defined(USE_LIBSSH2) || defined(USE_SSL)

 #define HMAC_MD5_LENGTH 16
--- a/lib/curl_setup.h
+++ b/lib/curl_setup.h
@ -298,6 +298,9 @@
 #  ifndef CURL_DISABLE_AWS
 #  define CURL_DISABLE_AWS
 #  endif
+#  ifndef CURL_DISABLE_HTTPSIG
+#  define CURL_DISABLE_HTTPSIG
+#  endif
 #  ifndef CURL_DISABLE_DOH
 #  define CURL_DISABLE_DOH
 #  endif
--- a/lib/curl_sha256.h
+++ b/lib/curl_sha256.h
@ -26,7 +26,8 @@
 ***************************************************************************/
 #include "curl_setup.h"

-#if !defined(CURL_DISABLE_AWS) || !defined(CURL_DISABLE_DIGEST_AUTH) || \
+#if !defined(CURL_DISABLE_AWS) || !defined(CURL_DISABLE_HTTPSIG) ||     \
+  !defined(CURL_DISABLE_DIGEST_AUTH) ||                                 \
  defined(USE_LIBSSH2) || defined(USE_SSL)

 #include "curl_hmac.h"
--- a/lib/easyoptions.c
+++ b/lib/easyoptions.c
@ -140,6 +140,10 @@ const struct curl_easyoption Curl_easyopts[] = {
  { "HTTPHEADER", CURLOPT_HTTPHEADER, CURLOT_SLIST, 0 },
  { "HTTPPOST", CURLOPT_HTTPPOST, CURLOT_OBJECT, 0 },
  { "HTTPPROXYTUNNEL", CURLOPT_HTTPPROXYTUNNEL, CURLOT_LONG, 0 },
+  { "HTTPSIG_ALGORITHM", CURLOPT_HTTPSIG_ALGORITHM, CURLOT_VALUES, 0 },
+  { "HTTPSIG_HEADERS", CURLOPT_HTTPSIG_HEADERS, CURLOT_STRING, 0 },
+  { "HTTPSIG_KEY", CURLOPT_HTTPSIG_KEY, CURLOT_STRING, 0 },
+  { "HTTPSIG_KEYID", CURLOPT_HTTPSIG_KEYID, CURLOT_STRING, 0 },
  { "HTTP_CONTENT_DECODING", CURLOPT_HTTP_CONTENT_DECODING, CURLOT_LONG, 0 },
  { "HTTP_TRANSFER_DECODING", CURLOPT_HTTP_TRANSFER_DECODING,
    CURLOT_LONG, 0 },
@ -385,6 +389,6 @@ const struct curl_easyoption Curl_easyopts[] = {
 */
 int Curl_easyopts_check(void)
 {
-  return (CURLOPT_LASTENTRY % 10000) != (328 + 1);
+  return (CURLOPT_LASTENTRY % 10000) != (332 + 1);
 }
 #endif
--- a/lib/http.c
+++ b/lib/http.c
@ -61,6 +61,7 @@
 #include "http_ntlm.h"
 #include "http_negotiate.h"
 #include "http_aws_sigv4.h"
+#include "http_httpsig.h"
 #include "url.h"
 #include "urlapi-int.h"
 #include "curl_share.h"
@ -376,6 +377,10 @@ static bool pickoneauth(struct auth *pick, unsigned long mask,
 #ifndef CURL_DISABLE_AWS
  else if(avail & CURLAUTH_AWS_SIGV4)
    pick->picked = CURLAUTH_AWS_SIGV4;
+#endif
+#ifndef CURL_DISABLE_HTTPSIG
+  else if(avail & CURLAUTH_HTTPSIG)
+    pick->picked = CURLAUTH_HTTPSIG;
 #endif
  else {
    pick->picked = CURLAUTH_PICKNONE; /* we select to use nothing */
@ -665,6 +670,15 @@ static CURLcode output_auth_headers(struct Curl_easy *data,
  }
  else
 #endif
+#ifndef CURL_DISABLE_HTTPSIG
+  if((authstatus->picked == CURLAUTH_HTTPSIG) && !proxy) {
+    auth = "HTTPSIG";
+    result = Curl_output_httpsig(data);
+    if(result)
+      return result;
+  }
+  else
+#endif
 #ifdef USE_SPNEGO
  if(authstatus->picked == CURLAUTH_NEGOTIATE) {
    auth = "Negotiate";
@ -792,6 +806,9 @@ CURLcode Curl_http_output_auth(struct Curl_easy *data,
 #ifdef USE_SPNEGO
    !(authhost->want & CURLAUTH_NEGOTIATE) &&
    !(authproxy->want & CURLAUTH_NEGOTIATE) &&
+#endif
+#ifndef CURL_DISABLE_HTTPSIG
+    !(authhost->want & CURLAUTH_HTTPSIG) &&
 #endif
    !data->state.creds) {
    /* no authentication with no user or password */
--- a/lib/http_httpsig.c
+++ b/lib/http_httpsig.c
@ -0,0 +1,692 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ * SPDX-License-Identifier: curl
+ *
+ ***************************************************************************/
+#include "curl_setup.h"
+
+#if !defined(CURL_DISABLE_HTTP) && !defined(CURL_DISABLE_HTTPSIG)
+
+#include "urldata.h"
+#include "http_httpsig.h"
+#include "curl_ed25519.h"
+#include "curl_hmac.h"
+#include "curl_sha256.h"
+#include "http.h"
+#include "transfer.h"
+#include "curl_trc.h"
+#include "slist.h"
+#include "curlx/dynbuf.h"
+#include "curlx/base64.h"
+#include "curlx/strdup.h"
+#include "curlx/strparse.h"
+#include "strcase.h"
+
+#include <time.h>
+
+#define HTTPSIG_MAX_SIG_BASE   CURL_MAX_HTTP_HEADER
+#define HTTPSIG_MAX_COMPONENTS 16
+#define HTTPSIG_MAX_RAW_SIG    CURL_ED25519_SIGLEN
+#define HTTPSIG_DEFAULT_LABEL  "sig1"
+
+enum httpsig_alg {
+  HTTPSIG_ALG_ED25519,
+  HTTPSIG_ALG_HMAC_SHA256,
+  HTTPSIG_ALG_UNKNOWN
+};
+
+static const char *alg_to_str(enum httpsig_alg alg)
+{
+  switch(alg) {
+  case HTTPSIG_ALG_ED25519:
+    return "ed25519";
+  case HTTPSIG_ALG_HMAC_SHA256:
+    return "hmac-sha256";
+  default:
+    break;
+  }
+  return NULL;
+}
+
+static enum httpsig_alg id_to_alg(uint8_t val)
+{
+  switch(val) {
+  case CURLHTTPSIG_ED25519:
+    return HTTPSIG_ALG_ED25519;
+  case CURLHTTPSIG_HMAC_SHA256:
+    return HTTPSIG_ALG_HMAC_SHA256;
+  default:
+    break;
+  }
+  return HTTPSIG_ALG_UNKNOWN;
+}
+
+static CURLcode decode_hex_key(struct Curl_easy *data,
+                               const char *hexstr,
+                               unsigned char **keyout,
+                               size_t *keylen)
+{
+  size_t len, i;
+  unsigned char *keybuf;
+
+  *keyout = NULL;
+  *keylen = 0;
+
+  len = strlen(hexstr);
+  while(len > 0 && ISNEWLINE(hexstr[len - 1]))
+    len--;
+
+  if(len == 0 || (len & 1) != 0) {
+    failf(data, "httpsig: invalid hex key (length %zu)", len);
+    return CURLE_BAD_FUNCTION_ARGUMENT;
+  }
+
+  if(len > CURL_MAX_INPUT_LENGTH) {
+    failf(data, "httpsig: hex key too long");
+    return CURLE_BAD_FUNCTION_ARGUMENT;
+  }
+
+  keybuf = curlx_malloc(len / 2);
+  if(!keybuf)
+    return CURLE_OUT_OF_MEMORY;
+
+  for(i = 0; i < len; i += 2) {
+    if(!ISXDIGIT(hexstr[i]) || !ISXDIGIT(hexstr[i + 1])) {
+      failf(data, "httpsig: invalid hex at position %zu ('%c%c')",
+            i, hexstr[i], hexstr[i + 1]);
+      curlx_free(keybuf);
+      return CURLE_BAD_FUNCTION_ARGUMENT;
+    }
+    keybuf[i / 2] = (unsigned char)((curlx_hexval(hexstr[i]) << 4) |
+                                     curlx_hexval(hexstr[i + 1]));
+  }
+
+  *keyout = keybuf;
+  *keylen = len / 2;
+  return CURLE_OK;
+}
+
+/* @authority matches the Host header field-value when available (RFC 9421).
+   data->state.aptr.host is produced by http_set_aptr_host() before auth. */
+static CURLcode httpsig_authority(struct Curl_easy *data,
+                                  struct connectdata *conn,
+                                  struct dynbuf *authority_buf)
+{
+  const char *h = data->state.aptr.host;
+
+  if(h && curl_strnequal(h, "host:", 5)) {
+    const char *value = h + 5;
+    const char *end;
+
+    while(ISBLANK(*value))
+      value++;
+    if(*value) {
+      CURLcode result;
+
+      end = value;
+      while(*end && !ISNEWLINE(*end))
+        end++;
+      while(end > value && ISBLANK(end[-1]))
+        end--;
+      result = curlx_dyn_addn(authority_buf, value, (size_t)(end - value));
+      if(result)
+        return result;
+      return CURLE_OK;
+    }
+  }
+
+  {
+    const char *hostname = conn->origin->hostname;
+    uint16_t port = conn->origin->port;
+
+    if((conn->given->defport != port) && port)
+      return curlx_dyn_addf(authority_buf, "%s:%u", hostname, port);
+    return curlx_dyn_add(authority_buf, hostname);
+  }
+}
+
+static CURLcode sf_append_quoted(struct dynbuf *buf, const char *str)
+{
+  CURLcode result = curlx_dyn_addn(buf, "\"", 1);
+  if(result)
+    return result;
+  while(*str) {
+    if(ISCNTRL(*str))
+      return CURLE_BAD_FUNCTION_ARGUMENT;
+    if(*str == '\\' || *str == '"') {
+      result = curlx_dyn_addn(buf, "\\", 1);
+      if(result)
+        return result;
+    }
+    result = curlx_dyn_addn(buf, str, 1);
+    if(result)
+      return result;
+    str++;
+  }
+  return curlx_dyn_addn(buf, "\"", 1);
+}
+
+/* base64-encode raw bytes into an RFC 8941 byte sequence (:base64:) */
+static CURLcode sf_encode_byte_seq(const unsigned char *raw, size_t rawlen,
+                                   struct dynbuf *out)
+{
+  CURLcode result;
+  size_t b64len;
+  char *b64;
+
+  result = curlx_base64_encode(raw, rawlen, &b64, &b64len);
+  if(result)
+    return result;
+
+  result = curlx_dyn_addn(out, ":", 1);
+  if(!result)
+    result = curlx_dyn_addn(out, b64, b64len);
+  if(!result)
+    result = curlx_dyn_addn(out, ":", 1);
+
+  curlx_free(b64);
+  return result;
+}
+
+static CURLcode build_sig_params(struct dynbuf *params,
+                                 const char **components, size_t count,
+                                 time_t created, const char *keyid,
+                                 enum httpsig_alg alg)
+{
+  CURLcode result;
+  size_t i;
+
+  result = curlx_dyn_addn(params, "(", 1);
+  if(result)
+    return result;
+
+  for(i = 0; i < count; i++) {
+    if(i > 0) {
+      result = curlx_dyn_addn(params, " ", 1);
+      if(result)
+        return result;
+    }
+    result = sf_append_quoted(params, components[i]);
+    if(result)
+      return result;
+  }
+
+  result = curlx_dyn_addn(params, ")", 1);
+  if(result)
+    return result;
+
+  result = curlx_dyn_addf(params, ";created=%lld", (long long)created);
+  if(result)
+    return result;
+
+  if(keyid && *keyid) {
+    result = curlx_dyn_add(params, ";keyid=");
+    if(result)
+      return result;
+    result = sf_append_quoted(params, keyid);
+    if(result)
+      return result;
+  }
+
+  result = curlx_dyn_addf(params, ";alg=\"%s\"", alg_to_str(alg));
+  return result;
+}
+
+/* strings defined by RFC 9421 */
+#define SIG_METHOD    "@method"
+#define SIG_AUTHORITY "@authority"
+#define SIG_PATH      "@path"
+#define SIG_QUERY     "@query"
+
+/* Resolve a component identifier to its value.
+ * For headers, we walk the full user-supplied header list to combine
+ * duplicate field values with ", " per RFC 9421 Section 2.1. Each
+ * individual value is trimmed of leading/trailing OWS and the trailing
+ * \r\n. The combined result is written into the caller-provided buffer. */
+static CURLcode resolve_component(const char *name,
+                                  const char *method,
+                                  const char *authority,
+                                  const char *path,
+                                  const char *query,
+                                  struct Curl_easy *data,
+                                  struct dynbuf *valbuf,
+                                  const char **out)
+{
+  *out = NULL;
+
+  if(name[0] == '@') {
+    if(curl_strequal(name, SIG_METHOD))
+      *out = method;
+    else if(curl_strequal(name, SIG_AUTHORITY))
+      *out = authority;
+    else if(curl_strequal(name, SIG_PATH))
+      *out = path;
+    else if(curl_strequal(name, SIG_QUERY))
+      *out = query;
+    else {
+      failf(data, "httpsig: unsupported derived component '%s'", name);
+      return CURLE_BAD_FUNCTION_ARGUMENT;
+    }
+    if(!*out) {
+      failf(data, "httpsig: derived component '%s' has no value", name);
+      return CURLE_BAD_FUNCTION_ARGUMENT;
+    }
+    return CURLE_OK;
+  }
+  else {
+    /* RFC 9421 Section 2.1: walk all user-supplied headers and combine
+       duplicate field values with ", " per HTTP field combination rules. */
+    struct curl_slist *head;
+    size_t namelen = strlen(name);
+    bool found = FALSE;
+
+    curlx_dyn_reset(valbuf);
+
+    for(head = data->set.headers; head; head = head->next) {
+      if(curl_strnequal(head->data, name, namelen) &&
+         Curl_headersep(head->data[namelen])) {
+        const char *p = strchr(head->data, ':');
+        if(p) {
+          CURLcode result;
+          struct Curl_str content;
+          curlx_str_assign(&content, p + 1, strlen(p + 1));
+          curlx_str_trimblanks(&content);
+          if(found) {
+            result = curlx_dyn_addn(valbuf, ", ", 2);
+            if(result)
+              return result;
+          }
+          result = curlx_dyn_addn(valbuf, curlx_str(&content),
+                                  curlx_strlen(&content));
+          if(result)
+            return result;
+          found = TRUE;
+        }
+      }
+    }
+
+    if(found) {
+      *out = curlx_dyn_ptr(valbuf);
+      return CURLE_OK;
+    }
+    failf(data, "httpsig: header '%s' not found in request", name);
+    return CURLE_BAD_FUNCTION_ARGUMENT;
+  }
+}
+
+static CURLcode build_sig_base(struct dynbuf *base,
+                               const char **components, size_t count,
+                               const char *method,
+                               const char *authority,
+                               const char *path,
+                               const char *query,
+                               struct Curl_easy *data,
+                               const char *sig_params)
+{
+  CURLcode result;
+  size_t i;
+  struct dynbuf hdrvalbuf;
+
+  curlx_dyn_init(&hdrvalbuf, CURL_MAX_HTTP_HEADER);
+
+  for(i = 0; i < count; i++) {
+    const char *val = NULL;
+    result = resolve_component(components[i], method,
+                               authority, path, query, data,
+                               &hdrvalbuf, &val);
+    if(result || !val) {
+      failf(data, "httpsig: cannot resolve component '%s'", components[i]);
+      curlx_dyn_free(&hdrvalbuf);
+      return result ? result : CURLE_BAD_FUNCTION_ARGUMENT;
+    }
+
+    result = curlx_dyn_addf(base, "\"%s\": %s\n", components[i], val);
+    if(result) {
+      curlx_dyn_free(&hdrvalbuf);
+      return result;
+    }
+  }
+
+  curlx_dyn_free(&hdrvalbuf);
+  result = curlx_dyn_addf(base, "\"@signature-params\": %s", sig_params);
+  return result;
+}
+
+static CURLcode parse_components(struct Curl_easy *data,
+                                 const char *query,
+                                 const char **components,
+                                 size_t *ncomp_out,
+                                 char **hdrs_copy_out)
+{
+  const char *hdrs = data->set.str[STRING_HTTPSIG_HEADERS];
+  size_t ncomp = 0;
+
+  *hdrs_copy_out = NULL;
+  if(hdrs && *hdrs) {
+    char *p;
+    char *hdrs_copy = curlx_strdup(hdrs);
+    if(!hdrs_copy)
+      return CURLE_OUT_OF_MEMORY;
+    *hdrs_copy_out = hdrs_copy;
+    p = hdrs_copy;
+    while(*p && ncomp < HTTPSIG_MAX_COMPONENTS) {
+      char *start;
+      size_t tlen = 0;
+      const char *p2 = p;
+
+      curlx_str_passblanks(&p2);
+      if(!*p2)
+        break;
+      p = start = CURL_UNCONST(p2);
+      while(*p && !ISBLANK(*p)) {
+        if((*p == '\"') || (*p == '\\'))
+          return CURLE_BAD_FUNCTION_ARGUMENT;
+        p++;
+        tlen++;
+      }
+      if(*p)
+        *p++ = '\0';
+
+      if(tlen && start[tlen - 1] == ':') {
+        /* Header field: drop the trailing ':' marker. RFC 9421 field
+           names are canonically lowercase (Section 2.1). */
+        start[--tlen] = '\0';
+        if(!tlen) {
+          failf(data, "httpsig: empty header component name");
+          return CURLE_BAD_FUNCTION_ARGUMENT;
+        }
+        Curl_strntolower(start, start, tlen);
+        components[ncomp++] = start;
+      }
+      else {
+        /* Derived component: map the bare name to its canonical RFC 9421
+           '@'-prefixed identifier (Section 2.2). */
+        Curl_strntolower(start, start, tlen);
+        if(!strcmp(start, "method"))
+          components[ncomp++] = SIG_METHOD;
+        else if(!strcmp(start, "authority"))
+          components[ncomp++] = SIG_AUTHORITY;
+        else if(!strcmp(start, "path"))
+          components[ncomp++] = SIG_PATH;
+        else if(!strcmp(start, "query"))
+          components[ncomp++] = SIG_QUERY;
+        else {
+          failf(data, "httpsig: unknown component '%s'", start);
+          return CURLE_BAD_FUNCTION_ARGUMENT;
+        }
+      }
+    }
+    if(!ncomp) {
+      failf(data, "httpsig: no signature components specified");
+      return CURLE_BAD_FUNCTION_ARGUMENT;
+    }
+    if(*p) {
+      failf(data, "httpsig: too many signature components (max %u)",
+            (unsigned int)HTTPSIG_MAX_COMPONENTS);
+      return CURLE_BAD_FUNCTION_ARGUMENT;
+    }
+
+    /* RFC 9421 Section 2: each covered component MUST occur only once */
+    {
+      size_t i, j;
+
+      for(i = 0; i < ncomp; i++) {
+        for(j = i + 1; j < ncomp; j++) {
+          if(!strcmp(components[i], components[j])) {
+            failf(data, "httpsig: duplicate signature component '%s'",
+                  components[i]);
+            return CURLE_BAD_FUNCTION_ARGUMENT;
+          }
+        }
+      }
+    }
+  }
+  else {
+    components[ncomp++] = SIG_METHOD;
+    components[ncomp++] = SIG_AUTHORITY;
+    components[ncomp++] = SIG_PATH;
+    if(query)
+      components[ncomp++] = SIG_QUERY;
+  }
+
+  *ncomp_out = ncomp;
+  return CURLE_OK;
+}
+
+static time_t httpsig_get_created(void)
+{
+#ifdef DEBUGBUILD
+  char *force = getenv("CURL_FORCETIME");
+  if(force && *force) {
+    char *sigts = getenv("CURL_HTTPSIG_CREATED");
+    if(sigts && *sigts) {
+      const char *p = sigts;
+      curl_off_t num;
+      if(!curlx_str_number(&p, &num, CURL_OFF_T_MAX))
+        return (time_t)num;
+    }
+    return 0;
+  }
+#endif
+  return time(NULL);
+}
+
+static CURLcode httpsig_sign_base(struct Curl_easy *data,
+                                  enum httpsig_alg alg,
+                                  const unsigned char *keybuf,
+                                  size_t keylen,
+                                  const struct dynbuf *sig_base,
+                                  unsigned char *raw_sig,
+                                  size_t *raw_sig_len)
+{
+  CURLcode result;
+
+  switch(alg) {
+  case HTTPSIG_ALG_ED25519:
+    result = Curl_ed25519_sign(
+      keybuf, keylen,
+      (const unsigned char *)curlx_dyn_ptr(sig_base),
+      curlx_dyn_len(sig_base),
+      raw_sig, raw_sig_len);
+    break;
+  case HTTPSIG_ALG_HMAC_SHA256:
+    result = Curl_hmacit(&Curl_HMAC_SHA256, keybuf, keylen,
+                         (const unsigned char *)curlx_dyn_ptr(sig_base),
+                         curlx_dyn_len(sig_base), raw_sig);
+    if(!result)
+      *raw_sig_len = CURL_SHA256_DIGEST_LENGTH;
+    break;
+  default:
+    result = CURLE_BAD_FUNCTION_ARGUMENT;
+    break;
+  }
+
+  if(result && result == CURLE_NOT_BUILT_IN) {
+    failf(data, "httpsig: algorithm '%s' not supported by TLS backend",
+          alg_to_str(alg));
+  }
+  return result;
+}
+
+CURLcode Curl_output_httpsig(struct Curl_easy *data)
+{
+  CURLcode result = CURLE_OUT_OF_MEMORY;
+  struct connectdata *conn = data->conn;
+  const char *path;
+  const char *query;
+  Curl_HttpReq httpreq;
+  const char *method = NULL;
+  const char *hexkey;
+  const char *keyid;
+  enum httpsig_alg alg;
+  time_t created;
+  struct dynbuf sig_params;
+  struct dynbuf sig_base;
+  struct dynbuf sig_hdr;
+  struct dynbuf input_hdr;
+  struct dynbuf authority_buf;
+  const char *authority;
+  const char *components[HTTPSIG_MAX_COMPONENTS];
+  size_t ncomp = 0;
+  unsigned char *keybuf = NULL;
+  size_t keylen = 0;
+  unsigned char raw_sig[HTTPSIG_MAX_RAW_SIG];
+  size_t raw_sig_len = 0;
+  char *auth_headers = NULL;
+  char *hdrs_copy = NULL;
+  struct dynbuf query_dyn;
+
+  alg = id_to_alg(data->set.httpsig_algorithm);
+  if(alg == HTTPSIG_ALG_UNKNOWN) {
+    failf(data, "httpsig: CURLOPT_HTTPSIG_ALGORITHM is required");
+    return CURLE_BAD_FUNCTION_ARGUMENT;
+  }
+
+  hexkey = data->set.str[STRING_HTTPSIG_KEY];
+  keyid = data->set.str[STRING_HTTPSIG_KEYID];
+
+  if(!hexkey || !*hexkey) {
+    failf(data, "httpsig: CURLOPT_HTTPSIG_KEY is required");
+    return CURLE_BAD_FUNCTION_ARGUMENT;
+  }
+  if(!keyid || !*keyid) {
+    failf(data, "httpsig: CURLOPT_HTTPSIG_KEYID is required");
+    return CURLE_BAD_FUNCTION_ARGUMENT;
+  }
+
+  curlx_dyn_init(&sig_params, CURL_MAX_HTTP_HEADER);
+  curlx_dyn_init(&sig_base, HTTPSIG_MAX_SIG_BASE);
+  curlx_dyn_init(&sig_hdr, CURL_MAX_HTTP_HEADER);
+  curlx_dyn_init(&input_hdr, CURL_MAX_HTTP_HEADER);
+  curlx_dyn_init(&authority_buf, CURL_MAX_HTTP_HEADER);
+  curlx_dyn_init(&query_dyn, CURL_MAX_HTTP_HEADER);
+
+  if(Curl_checkheaders(data, STRCONST("Signature")) ||
+     Curl_checkheaders(data, STRCONST("Signature-Input"))) {
+    /* user provides their own Signature / Signature-Input headers, consider
+       this done */
+    goto done;
+  }
+
+  result = decode_hex_key(data, hexkey, &keybuf, &keylen);
+  if(result)
+    goto fail;
+
+  if(alg == HTTPSIG_ALG_ED25519 && keylen != 32) {
+    failf(data, "httpsig: ed25519 requires a 32-byte key (got %zu)", keylen);
+    result = CURLE_BAD_FUNCTION_ARGUMENT;
+    goto fail;
+  }
+
+  Curl_http_method(data, &method, &httpreq);
+
+  path = data->state.up.path;
+  if(!path || !*path)
+    path = "/";
+
+  query = data->state.up.query;
+
+  result = httpsig_authority(data, conn, &authority_buf);
+  if(result)
+    goto fail;
+  authority = curlx_dyn_ptr(&authority_buf);
+
+  /* Build @query value: RFC 9421 Section 2.2.7 - always starts with "?" */
+  if(query && *query)
+    result = curlx_dyn_addf(&query_dyn, "?%s", query);
+  else
+    result = curlx_dyn_add(&query_dyn, "?");
+  if(result)
+    goto fail;
+
+  result = parse_components(data, query, components, &ncomp, &hdrs_copy);
+  if(result)
+    goto fail;
+
+  created = httpsig_get_created();
+
+  result = build_sig_params(&sig_params, components, ncomp,
+                            created, keyid, alg);
+  if(result)
+    goto fail;
+
+  infof(data, "httpsig: Signature-Input params: %s",
+        curlx_dyn_ptr(&sig_params));
+
+  result = build_sig_base(&sig_base, components, ncomp,
+                          method, authority, path,
+                          curlx_dyn_ptr(&query_dyn),
+                          data, curlx_dyn_ptr(&sig_params));
+  if(result)
+    goto fail;
+
+  infof(data, "httpsig: Signature base: [%s]",
+        curlx_dyn_ptr(&sig_base));
+
+  result = httpsig_sign_base(data, alg, keybuf, keylen, &sig_base,
+                             raw_sig, &raw_sig_len);
+  if(result)
+    goto fail;
+
+  result = curlx_dyn_add(&sig_hdr, HTTPSIG_DEFAULT_LABEL "=");
+  if(result)
+    goto fail;
+  result = sf_encode_byte_seq(raw_sig, raw_sig_len, &sig_hdr);
+  if(result)
+    goto fail;
+
+  result = curlx_dyn_addf(&input_hdr, "%s=%s", HTTPSIG_DEFAULT_LABEL,
+                          curlx_dyn_ptr(&sig_params));
+  if(result)
+    goto fail;
+
+  auth_headers = curl_maprintf("Signature-Input: %s\r\n"
+                               "Signature: %s\r\n",
+                               curlx_dyn_ptr(&input_hdr),
+                               curlx_dyn_ptr(&sig_hdr));
+  if(!auth_headers)
+    goto fail;
+
+  infof(data, "httpsig: Signature-Input: %s", curlx_dyn_ptr(&input_hdr));
+  infof(data, "httpsig: Signature: %s", curlx_dyn_ptr(&sig_hdr));
+done:
+  curlx_free(data->req.hd_auth);
+  data->req.hd_auth = auth_headers;
+  data->state.authhost.done = TRUE;
+  result = CURLE_OK;
+
+fail:
+  if(keybuf) {
+    memset(keybuf, 0, keylen);
+    curlx_free(keybuf);
+  }
+  memset(raw_sig, 0, sizeof(raw_sig));
+  curlx_free(hdrs_copy);
+  curlx_dyn_free(&sig_params);
+  curlx_dyn_free(&sig_base);
+  curlx_dyn_free(&sig_hdr);
+  curlx_dyn_free(&input_hdr);
+  curlx_dyn_free(&authority_buf);
+  curlx_dyn_free(&query_dyn);
+  return result;
+}
+
+#endif /* !CURL_DISABLE_HTTP && !CURL_DISABLE_HTTPSIG */
--- a/lib/http_httpsig.h
+++ b/lib/http_httpsig.h
@ -0,0 +1,35 @@
+#ifndef HEADER_CURL_HTTP_HTTPSIG_H
+#define HEADER_CURL_HTTP_HTTPSIG_H
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ * SPDX-License-Identifier: curl
+ *
+ ***************************************************************************/
+#include "curl_setup.h"
+
+#if !defined(CURL_DISABLE_HTTP) && !defined(CURL_DISABLE_HTTPSIG)
+
+#include "urldata.h"
+
+CURLcode Curl_output_httpsig(struct Curl_easy *data);
+
+#endif /* !CURL_DISABLE_HTTP && !CURL_DISABLE_HTTPSIG */
+#endif /* HEADER_CURL_HTTP_HTTPSIG_H */
--- a/lib/setopt.c
+++ b/lib/setopt.c
@ -1103,6 +1103,19 @@ static CURLcode setopt_long_http(struct Curl_easy *data, CURLoption option,
 #else
    result = CURLE_NOT_BUILT_IN;
    break;
+#endif
+#ifndef CURL_DISABLE_HTTPSIG
+  case CURLOPT_HTTPSIG_ALGORITHM:
+    if(arg != CURLHTTPSIG_NONE &&
+       arg != CURLHTTPSIG_ED25519 &&
+       arg != CURLHTTPSIG_HMAC_SHA256)
+      return CURLE_BAD_FUNCTION_ARGUMENT;
+    s->httpsig_algorithm = (uint8_t)arg;
+    if(arg)
+      s->httpauth = (uint32_t)CURLAUTH_HTTPSIG;
+    else
+      s->httpauth &= ~(uint32_t)CURLAUTH_HTTPSIG;
+    break;
 #endif
  default:
    return CURLE_UNKNOWN_OPTION;
@ -2081,6 +2094,17 @@ static CURLcode setopt_cptr_http_mqtt(struct Curl_easy *data,
    if(s->str[STRING_AWS_SIGV4])
      s->httpauth = CURLAUTH_AWS_SIGV4;
    break;
+#endif
+#ifndef CURL_DISABLE_HTTPSIG
+  case CURLOPT_HTTPSIG_KEY:
+    result = Curl_setstropt(&s->str[STRING_HTTPSIG_KEY], ptr);
+    break;
+  case CURLOPT_HTTPSIG_KEYID:
+    result = Curl_setstropt(&s->str[STRING_HTTPSIG_KEYID], ptr);
+    break;
+  case CURLOPT_HTTPSIG_HEADERS:
+    result = Curl_setstropt(&s->str[STRING_HTTPSIG_HEADERS], ptr);
+    break;
 #endif
  case CURLOPT_REFERER:
    /*
--- a/lib/urldata.h
+++ b/lib/urldata.h
@ -849,6 +849,11 @@ enum dupstring {
 #ifndef CURL_DISABLE_AWS
  STRING_AWS_SIGV4, /* Parameters for V4 signature */
 #endif
+#ifndef CURL_DISABLE_HTTPSIG
+  STRING_HTTPSIG_KEY,    /* hex-encoded key data */
+  STRING_HTTPSIG_KEYID,  /* key identifier */
+  STRING_HTTPSIG_HEADERS, /* space-separated components to sign */
+#endif
 #ifndef CURL_DISABLE_PROXY
  STRING_HAPROXY_CLIENT_IP,     /* CURLOPT_HAPROXY_CLIENT_IP */
 #endif
@ -890,6 +895,7 @@ struct UserDefined {
  void *writeheader; /* write the header to this if non-NULL */
  uint32_t httpauth;  /* kind of HTTP authentication to use (bitmask) */
  uint32_t proxyauth; /* kind of proxy authentication to use (bitmask) */
+  uint8_t httpsig_algorithm; /* CURLHTTPSIG_* algorithm for RFC 9421 */
  void *postfields;  /* if POST, set the fields' values here */
  curl_seek_callback seek_func;      /* function that seeks the input */
  curl_off_t postfieldsize; /* if POST, this might have a size to use instead
--- a/lib/version.c
+++ b/lib/version.c
@ -469,6 +469,9 @@ static const struct feat features_table[] = {
  !defined(CURL_DISABLE_HTTP)
  FEATURE("HTTPS-proxy", https_proxy_present, CURL_VERSION_HTTPS_PROXY),
 #endif
+#ifndef CURL_DISABLE_HTTPSIG
+  FEATURE("HTTPSIG",     NULL,                0),
+#endif
 #ifdef USE_HTTPSRR
  FEATURE("HTTPSRR",     NULL,                0),
 #endif
--- a/projects/OS400/README.OS400
+++ b/projects/OS400/README.OS400
@ -71,6 +71,9 @@ options:
        CURLOPT_FTP_ALTERNATIVE_TO_USER
        CURLOPT_HAPROXY_CLIENT_IP
        CURLOPT_HSTS
+        CURLOPT_HTTPSIG_HEADERS
+        CURLOPT_HTTPSIG_KEY
+        CURLOPT_HTTPSIG_KEYID
        CURLOPT_INTERFACE
        CURLOPT_ISSUERCERT
        CURLOPT_KEYPASSWD
--- a/projects/OS400/ccsidcurl.c
+++ b/projects/OS400/ccsidcurl.c
@ -1060,6 +1060,9 @@ CURLcode curl_easy_setopt_ccsid(CURL *easy, CURLoption tag, ...)
  case CURLOPT_FTP_ALTERNATIVE_TO_USER:
  case CURLOPT_HAPROXY_CLIENT_IP:
  case CURLOPT_HSTS:
+  case CURLOPT_HTTPSIG_HEADERS:
+  case CURLOPT_HTTPSIG_KEY:
+  case CURLOPT_HTTPSIG_KEYID:
  case CURLOPT_INTERFACE:
  case CURLOPT_ISSUERCERT:
  case CURLOPT_KEYPASSWD:
--- a/scripts/managen
+++ b/scripts/managen
@ -1143,7 +1143,14 @@ HEAD
        elsif(length($desc) > 78) {
            print STDERR "WARN: the --$long description is too long\n";
        }
-        print $line;
+        my $ifdef = "";
+        my $endif = "";
+
+        if($long =~ /^(ipfs|httpsig)/) {
+            $ifdef = sprintf "#ifndef CURL_DISABLE_%s\n", uc($1);
+            $endif = "#endif\n";
+        }
+        print $ifdef.$line.$endif;
    }
    print <<FOOT
  { NULL, NULL, 0 }
--- a/src/config2setopts.c
+++ b/src/config2setopts.c
@ -38,6 +38,7 @@
 #include "tool_cb_see.h"
 #include "tool_cb_dbg.h"
 #include "tool_helpers.h"
+#include "tool_paramhlp.h"
 #include "tool_version.h"

 #ifdef HAVE_NETINET_IN_H
@ -564,6 +565,80 @@ static CURLcode cookie_setopts(struct OperationConfig *config, CURL *curl)
  return result;
 }

+/* only --httpsig-* options */
+#ifndef CURL_DISABLE_HTTPSIG
+static CURLcode httpsig_setopts(struct OperationConfig *config, CURL *curl)
+{
+  CURLcode result = CURLE_OK;
+  /* HTTP Message Signatures are enabled when any of the --httpsig-* options
+     is given. --httpsig-key and --httpsig-keyid are then required, while
+     --httpsig-algo is optional and defaults to ed25519. */
+  if(config->httpsig_algorithm || config->httpsig_key ||
+     config->httpsig_keyid || config->httpsig_headers) {
+    long httpsig_alg = CURLHTTPSIG_NONE;
+
+    if(!config->httpsig_key) {
+      errorf("--httpsig-key is required");
+      return CURLE_FAILED_INIT;
+    }
+    if(!config->httpsig_keyid) {
+      errorf("--httpsig-keyid is required");
+      return CURLE_FAILED_INIT;
+    }
+
+    if(!config->httpsig_algorithm ||
+       curl_strequal(config->httpsig_algorithm, "ed25519"))
+      httpsig_alg = CURLHTTPSIG_ED25519;
+    else if(curl_strequal(config->httpsig_algorithm, "hmac-sha256"))
+      httpsig_alg = CURLHTTPSIG_HMAC_SHA256;
+    else {
+      errorf("--httpsig-algo: unsupported algorithm '%s'",
+             config->httpsig_algorithm);
+      return CURLE_FAILED_INIT;
+    }
+    my_setopt_long(curl, CURLOPT_HTTPSIG_ALGORITHM, httpsig_alg);
+    MY_SETOPT_STR(curl, CURLOPT_HTTPSIG_HEADERS, config->httpsig_headers);
+    MY_SETOPT_STR(curl, CURLOPT_HTTPSIG_KEYID, config->httpsig_keyid);
+    {
+      FILE *keyf = curlx_fopen(config->httpsig_key, FOPEN_READTEXT);
+      if(keyf) {
+        char *hexdata = NULL;
+        ParameterError pe = file2string(&hexdata, keyf);
+
+        curlx_fclose(keyf);
+        if(pe == PARAM_NO_MEM) {
+          curlx_safefree(hexdata);
+          return CURLE_OUT_OF_MEMORY;
+        }
+        if(pe == PARAM_READ_ERROR) {
+          curlx_safefree(hexdata);
+          errorf("httpsig: cannot read key file '%s'", config->httpsig_key);
+          return CURLE_READ_ERROR;
+        }
+        if(!hexdata || !*hexdata) {
+          curlx_safefree(hexdata);
+          errorf("httpsig: key file '%s' is empty", config->httpsig_key);
+          return CURLE_BAD_FUNCTION_ARGUMENT;
+        }
+        /* can't use the MY_SETOPT_STR() macro here since it returns on error
+           and we must free the hexdata */
+        result = my_setopt_str(curl, CURLOPT_HTTPSIG_KEY, hexdata);
+        curlx_safefree(hexdata);
+        if(setopt_bad(result))
+          return result;
+      }
+      else {
+        errorf("httpsig: cannot open key file '%s'", config->httpsig_key);
+        return CURLE_READ_ERROR;
+      }
+    }
+  }
+  return CURLE_OK;
+}
+#else
+#define httpsig_setopts(x,y) CURLE_OK
+#endif
+
 /* only for HTTP transfers */
 static CURLcode http_setopts(struct OperationConfig *config, CURL *curl,
                             const char *use_proto)
@ -579,6 +654,9 @@ static CURLcode http_setopts(struct OperationConfig *config, CURL *curl,
 #ifndef CURL_DISABLE_AWS
  MY_SETOPT_STR(curl, CURLOPT_AWS_SIGV4, config->aws_sigv4);
 #endif
+  result = httpsig_setopts(config, curl);
+  if(result)
+    return result;
  my_setopt_long(curl, CURLOPT_AUTOREFERER, config->autoreferer);

  if(config->proxyheaders) {
--- a/src/curlinfo.c
+++ b/src/curlinfo.c
@ -93,6 +93,13 @@ static const char *disabled[] = {
  "OFF"
 #else
  "ON"
+#endif
+  ,
+  "httpsig: "
+#ifdef CURL_DISABLE_HTTPSIG
+  "OFF"
+#else
+  "ON"
 #endif
  ,
  "DoH: "
--- a/src/tool_cfgable.c
+++ b/src/tool_cfgable.c
@ -181,6 +181,10 @@ static void free_config_fields(struct OperationConfig *config)
  curlx_safefree(config->ftp_account);
  curlx_safefree(config->ftp_alternative_to_user);
  curlx_safefree(config->aws_sigv4);
+  curlx_safefree(config->httpsig_algorithm);
+  curlx_safefree(config->httpsig_headers);
+  curlx_safefree(config->httpsig_key);
+  curlx_safefree(config->httpsig_keyid);
  curlx_safefree(config->ech);
  curlx_safefree(config->ech_config);
  curlx_safefree(config->ech_public);
--- a/src/tool_cfgable.h
+++ b/src/tool_cfgable.h
@ -153,6 +153,10 @@ struct OperationConfig {
  char *unix_socket_path;         /* path to Unix domain socket */
  char *haproxy_clientip;         /* client IP for HAProxy protocol */
  char *aws_sigv4;
+  char *httpsig_algorithm;
+  char *httpsig_headers;
+  char *httpsig_key;
+  char *httpsig_keyid;
  char *ech;                      /* Config set by --ech keywords */
  char *ech_config;               /* Config set by "--ech esl:" option */
  char *ech_public;               /* Config set by "--ech pn:" option */
--- a/src/tool_getparam.c
+++ b/src/tool_getparam.c
@ -170,6 +170,12 @@ static const struct LongShort aliases[] = {
  {"http2-prior-knowledge",      ARG_NONE, ' ', C_HTTP2_PRIOR_KNOWLEDGE},
  {"http3",                      ARG_NONE|ARG_TLS, ' ', C_HTTP3},
  {"http3-only",                 ARG_NONE|ARG_TLS, ' ', C_HTTP3_ONLY},
+#ifndef CURL_DISABLE_HTTPSIG
+  {"httpsig-algo",               ARG_STRG, ' ', C_HTTPSIG_ALGORITHM},
+  {"httpsig-headers",            ARG_STRG, ' ', C_HTTPSIG_HEADERS},
+  {"httpsig-key",                ARG_FILE, ' ', C_HTTPSIG_KEY},
+  {"httpsig-keyid",              ARG_STRG, ' ', C_HTTPSIG_KEYID},
+#endif
  {"ignore-content-length",      ARG_BOOL, ' ', C_IGNORE_CONTENT_LENGTH},
  {"include",                    ARG_BOOL, ' ', C_INCLUDE},
  {"insecure",                   ARG_BOOL, 'k', C_INSECURE},
@ -2363,6 +2369,12 @@ static ParameterError opt_file(struct OperationConfig *config,
  case C_UPLOAD_FILE: /* --upload-file */
    err = parse_upload_file(config, nextarg);
    break;
+  case C_HTTPSIG_KEY: /* --httpsig-key */
+    if(!feature_httpsig)
+      err = PARAM_LIBCURL_DOESNT_SUPPORT;
+    else
+      err = getstr(&config->httpsig_key, nextarg, DENY_BLANK);
+    break;
  }
  return err;
 }
@ -2557,6 +2569,26 @@ static ParameterError opt_string(struct OperationConfig *config,
    config->authtype |= CURLAUTH_AWS_SIGV4;
    err = getstr(&config->aws_sigv4, nextarg, ALLOW_BLANK);
    break;
+  case C_HTTPSIG_ALGORITHM: /* --httpsig-algo */
+    if(!feature_httpsig)
+      err = PARAM_LIBCURL_DOESNT_SUPPORT;
+    else {
+      config->authtype |= CURLAUTH_HTTPSIG;
+      err = getstr(&config->httpsig_algorithm, nextarg, DENY_BLANK);
+    }
+    break;
+  case C_HTTPSIG_KEYID: /* --httpsig-keyid */
+    if(!feature_httpsig)
+      err = PARAM_LIBCURL_DOESNT_SUPPORT;
+    else
+      err = getstr(&config->httpsig_keyid, nextarg, DENY_BLANK);
+    break;
+  case C_HTTPSIG_HEADERS: /* --httpsig-headers */
+    if(!feature_httpsig)
+      err = PARAM_LIBCURL_DOESNT_SUPPORT;
+    else
+      err = getstr(&config->httpsig_headers, nextarg, DENY_BLANK);
+    break;
  case C_INTERFACE: /* --interface */
    /* interface */
    err = getstr(&config->iface, nextarg, DENY_BLANK);
--- a/src/tool_getparam.h
+++ b/src/tool_getparam.h
@ -125,6 +125,10 @@ typedef enum {
  C_HTTP2_PRIOR_KNOWLEDGE,
  C_HTTP3,
  C_HTTP3_ONLY,
+  C_HTTPSIG_ALGORITHM,
+  C_HTTPSIG_HEADERS,
+  C_HTTPSIG_KEY,
+  C_HTTPSIG_KEYID,
  C_IGNORE_CONTENT_LENGTH,
  C_INCLUDE,
  C_INSECURE,
--- a/src/tool_libinfo.c
+++ b/src/tool_libinfo.c
@ -69,6 +69,7 @@ bool feature_brotli = FALSE;
 bool feature_hsts = FALSE;
 bool feature_http2 = FALSE;
 bool feature_http3 = FALSE;
+bool feature_httpsig = FALSE;
 bool feature_httpsproxy = FALSE;
 bool feature_libz = FALSE;
 bool feature_ntlm = FALSE;
@ -97,6 +98,7 @@ static struct feature_name_presentp {
  { "HTTP2",          &feature_http2,       CURL_VERSION_HTTP2 },
  { "HTTP3",          &feature_http3,       CURL_VERSION_HTTP3 },
  { "HTTPS-proxy",    &feature_httpsproxy,  CURL_VERSION_HTTPS_PROXY },
+  { "HTTPSIG",        &feature_httpsig,     0 },
  { "IDN",            NULL,                 CURL_VERSION_IDN },
  { "IPv6",           NULL,                 CURL_VERSION_IPV6 },
  { "Kerberos",       NULL,                 CURL_VERSION_KERBEROS5 },
--- a/src/tool_libinfo.h
+++ b/src/tool_libinfo.h
@ -52,6 +52,7 @@ extern bool feature_brotli;
 extern bool feature_hsts;
 extern bool feature_http2;
 extern bool feature_http3;
+extern bool feature_httpsig;
 extern bool feature_httpsproxy;
 extern bool feature_libz;
 extern bool feature_ntlm;
--- a/src/tool_listhelp.c
+++ b/src/tool_listhelp.c
@ -303,6 +303,26 @@ const struct helptxt helptext[] = {
  { "    --http3-only",
    "Use HTTP/3 only",
    CURLHELP_HTTP },
+#ifndef CURL_DISABLE_HTTPSIG
+  { "    --httpsig-algo <algorithm>",
+    "Algorithm for HTTP Message Signatures",
+    CURLHELP_AUTH | CURLHELP_HTTP },
+#endif
+#ifndef CURL_DISABLE_HTTPSIG
+  { "    --httpsig-headers <components>",
+    "Components to sign for HTTP Message Signatures",
+    CURLHELP_AUTH | CURLHELP_HTTP },
+#endif
+#ifndef CURL_DISABLE_HTTPSIG
+  { "    --httpsig-key <file>",
+    "Key file for HTTP Message Signatures",
+    CURLHELP_AUTH | CURLHELP_HTTP },
+#endif
+#ifndef CURL_DISABLE_HTTPSIG
+  { "    --httpsig-keyid <id>",
+    "Key identifier for HTTP Message Signatures",
+    CURLHELP_AUTH | CURLHELP_HTTP },
+#endif
  { "    --ignore-content-length",
    "Ignore the size of the remote resource",
    CURLHELP_HTTP | CURLHELP_FTP },
@ -315,9 +335,11 @@ const struct helptxt helptext[] = {
  { "    --ip-tos <string>",
    "Set IP Type of Service or Traffic Class",
    CURLHELP_CONNECTION },
+#ifndef CURL_DISABLE_IPFS
  { "    --ipfs-gateway <URL>",
    "Gateway for IPFS",
    CURLHELP_CURL },
+#endif
  { "-4, --ipv4",
    "Resolve names to IPv4 addresses",
    CURLHELP_CONNECTION | CURLHELP_DNS },
--- a/tests/data/Makefile.am
+++ b/tests/data/Makefile.am
@ -290,11 +290,16 @@ test3300 test3301 test3302 test3303 test3304 test3305 test3306 \
 \
 test3400 test3401 \
 \
-test4000 test4001
+test4000 test4001 \
+\
+test5000 test5001 test5002 test5003 test5004 test5005 test5006 test5007 \
+test5008 test5009 test5010 test5011 test5012 test5013 test5014 test5015 \
+test5016 test5017 test5018 test5019 test5020 test5021

 EXTRA_DIST = $(TESTCASES) DISABLED data-xml1 \
 data1461.txt data1463.txt  \
 data1400.c data1401.c data1402.c data1403.c data1404.c data1405.c data1406.c \
 data1407.c data1420.c data1465.c data1481.c \
 data1705-1.md data1705-2.md data1705-3.md data1705-4.md data1705-stdout.1 \
-data1706-1.md data1706-2.md data1706-3.md data1706-4.md data1706-stdout.txt
+data1706-1.md data1706-2.md data1706-3.md data1706-4.md data1706-stdout.txt \
+data-httpsig-ed25519.key data-httpsig-hmac-sha256.key
--- a/tests/data/data-httpsig-ed25519.key
+++ b/tests/data/data-httpsig-ed25519.key
@ -0,0 +1 @@
+9f8362f87a484a954e6e740c5b4c0e84229139a20aa8ab56ff66586f6a7d29c5
--- a/tests/data/data-httpsig-hmac-sha256.key
+++ b/tests/data/data-httpsig-hmac-sha256.key
@ -0,0 +1 @@
+0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef
--- a/tests/data/test5000
+++ b/tests/data/test5000
@ -0,0 +1,57 @@
+<?xml version="1.0" encoding="US-ASCII"?>
+<testcase>
+<info>
+<keywords>
+HTTP
+CURLOPT_HTTPSIG_ALGORITHM
+RFC9421
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data nocheck="yes">
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+Content-Type: text/html
+Content-Length: 0
+
+</data>
+</reply>
+
+# Client-side
+<client>
+<server>
+http
+</server>
+# this relies on the Debug feature which allows tests to set the time
+<features>
+Debug
+httpsig
+</features>
+
+<name>
+HTTP RFC 9421 Message Signatures: basic GET with Ed25519
+</name>
+<tool>
+lib%TESTNUMBER
+</tool>
+
+<command>
+http://example.com:9000/%TESTNUMBER/resource example.com:9000:%HOSTIP:%HTTPPORT
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+<protocol crlf="headers">
+GET /%TESTNUMBER/resource HTTP/1.1
+Host: example.com:9000
+Signature-Input: sig1=("@method" "@authority" "@path");created=0;keyid="test-key-ed25519";alg="ed25519"
+Signature: sig1=:Olp3ugYSVwc47PTNBMrkV2P+8p5w2VPFzURxNaG44UA2On6OFG2FzFLEl8QEN1khiOdRNlFDouZsOwpJoPHvBA==:
+Accept: */*
+
+</protocol>
+</verify>
+</testcase>
--- a/tests/data/test5001
+++ b/tests/data/test5001
@ -0,0 +1,55 @@
+<?xml version="1.0" encoding="US-ASCII"?>
+<testcase>
+<info>
+<keywords>
+HTTP
+httpsig
+RFC9421
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data crlf="headers">
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+Last-Modified: Tue, 13 Jun 2000 12:10:00 GMT
+Content-Length: 6
+Connection: close
+Content-Type: text/html
+
+-foo-
+</data>
+</reply>
+
+# Client-side
+<client>
+<server>
+http
+</server>
+<features>
+Debug
+httpsig
+</features>
+<name>
+HTTP RFC 9421 Message Signatures: CLI GET with query
+</name>
+<command>
+"http://example.com:8000/%TESTNUMBER/resource?action=read" --httpsig-algo "ed25519" --httpsig-key %SRCDIR/data/data-httpsig-ed25519.key --httpsig-keyid "my-key-1" --connect-to example.com:8000:%HOSTIP:%HTTPPORT
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+<protocol crlf="headers">
+GET /%TESTNUMBER/resource?action=read HTTP/1.1
+Host: example.com:8000
+Signature-Input: sig1=("@method" "@authority" "@path" "@query");created=0;keyid="my-key-1";alg="ed25519"
+Signature: sig1=:RQniOeqmwdRzGvoDIMJ8XJha75evJWgqo5/66EeuJeEGczZtnP2U/F52Lzd/y7Vd1DCb8oUcCKHrKi2VJI7lBA==:
+User-Agent: curl/%VERSION
+Accept: */*
+
+</protocol>
+</verify>
+</testcase>
--- a/tests/data/test5002
+++ b/tests/data/test5002
@ -0,0 +1,55 @@
+<?xml version="1.0" encoding="US-ASCII"?>
+<testcase>
+<info>
+<keywords>
+HTTP
+httpsig
+RFC9421
+hmac-sha256
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data crlf="headers">
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+Content-Length: 6
+Connection: close
+Content-Type: text/html
+
+-foo-
+</data>
+</reply>
+
+# Client-side
+<client>
+<server>
+http
+</server>
+<features>
+Debug
+httpsig
+</features>
+<name>
+HTTP RFC 9421 Message Signatures: CLI GET with HMAC-SHA256
+</name>
+<command>
+"http://example.com:7000/%TESTNUMBER/resource" --httpsig-algo "hmac-sha256" --httpsig-key %SRCDIR/data/data-httpsig-hmac-sha256.key --httpsig-keyid "shared-key-1" --connect-to example.com:7000:%HOSTIP:%HTTPPORT
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+<protocol crlf="headers">
+GET /%TESTNUMBER/resource HTTP/1.1
+Host: example.com:7000
+Signature-Input: sig1=("@method" "@authority" "@path");created=0;keyid="shared-key-1";alg="hmac-sha256"
+Signature: sig1=:jvajJheXE4H/TqWfAn8m0d0Rx0XWYKADN/1P0qn+FLw=:
+User-Agent: curl/%VERSION
+Accept: */*
+
+</protocol>
+</verify>
+</testcase>
--- a/tests/data/test5003
+++ b/tests/data/test5003
@ -0,0 +1,55 @@
+<?xml version="1.0" encoding="US-ASCII"?>
+<testcase>
+<info>
+<keywords>
+HTTP
+httpsig
+RFC9421
+httpsig-headers
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data crlf="headers">
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+Content-Length: 6
+Connection: close
+Content-Type: text/html
+
+-foo-
+</data>
+</reply>
+
+# Client-side
+<client>
+<server>
+http
+</server>
+<features>
+Debug
+httpsig
+</features>
+<name>
+HTTP RFC 9421 Message Signatures: custom --httpsig-headers
+</name>
+<command>
+"http://example.com:6000/%TESTNUMBER/resource" --httpsig-algo "ed25519" --httpsig-key %SRCDIR/data/data-httpsig-ed25519.key --httpsig-keyid "test-key-ed25519" --httpsig-headers "method authority" --connect-to example.com:6000:%HOSTIP:%HTTPPORT
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+<protocol crlf="headers">
+GET /%TESTNUMBER/resource HTTP/1.1
+Host: example.com:6000
+Signature-Input: sig1=("@method" "@authority");created=0;keyid="test-key-ed25519";alg="ed25519"
+Signature: sig1=:q+8VHrGBOhkJm9d9dxKv3BfhyVWKIFiYXqdLZVx8yGrTzZO6Q6zJicFFuLvwJex6DS+Pw6YEMQzmtyj7dKOCCw==:
+User-Agent: curl/%VERSION
+Accept: */*
+
+</protocol>
+</verify>
+</testcase>
--- a/tests/data/test5004
+++ b/tests/data/test5004
@ -0,0 +1,66 @@
+<?xml version="1.0" encoding="US-ASCII"?>
+<testcase>
+<info>
+<keywords>
+HTTP
+CURLOPT_HTTPSIG_ALGORITHM
+RFC9421
+ed25519
+B.2.6
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data nocheck="yes">
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+Content-Type: text/html
+Content-Length: 0
+
+</data>
+</reply>
+
+# Client-side
+<client>
+<server>
+http
+</server>
+<features>
+Debug
+httpsig
+</features>
+
+<name>
+HTTP RFC 9421 B.2.6: Ed25519 POST with headers (RFC test vector)
+</name>
+<tool>
+lib%TESTNUMBER
+</tool>
+
+<setenv>
+CURL_HTTPSIG_CREATED=1618884473
+</setenv>
+
+<command>
+http://example.com/%TESTNUMBER/foo example.com:80:%HOSTIP:%HTTPPORT
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+<protocol crlf="headers" nonewline="yes">
+POST /%TESTNUMBER/foo HTTP/1.1
+Host: example.com
+Signature-Input: sig1=("date" "@method" "@path" "@authority" "content-type" "content-length");created=1618884473;keyid="test-key-ed25519";alg="ed25519"
+Signature: sig1=:6QriGerNuao/A02UMre01lQOwlVQ0L9Cx3WJPQonQpUdKxSNg/XXXqjKdcC9PELzmAKJ10loLIq10yYLTzmzCA==:
+Accept: */*
+Date: Tue, 20 Apr 2021 02:07:55 GMT
+Content-Type: application/json
+Content-Length: 18
+
+{"hello": "world"}
+</protocol>
+</verify>
+</testcase>
--- a/tests/data/test5005
+++ b/tests/data/test5005
@ -0,0 +1,56 @@
+<?xml version="1.0" encoding="US-ASCII"?>
+<testcase>
+<info>
+<keywords>
+HTTP
+httpsig
+RFC9421
+header-signing
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data crlf="headers">
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+Content-Length: 6
+Connection: close
+Content-Type: text/html
+
+-foo-
+</data>
+</reply>
+
+# Client-side
+<client>
+<server>
+http
+</server>
+<features>
+Debug
+httpsig
+</features>
+<name>
+HTTP RFC 9421 Message Signatures: sign with a regular HTTP header
+</name>
+<command>
+"http://example.com:5000/%TESTNUMBER/resource" --httpsig-algo "ed25519" --httpsig-key %SRCDIR/data/data-httpsig-ed25519.key --httpsig-keyid "test-key-ed25519" --httpsig-headers "method authority content-type:" -H "Content-Type: application/json" --connect-to example.com:5000:%HOSTIP:%HTTPPORT
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+<protocol crlf="headers">
+GET /%TESTNUMBER/resource HTTP/1.1
+Host: example.com:5000
+Signature-Input: sig1=("@method" "@authority" "content-type");created=0;keyid="test-key-ed25519";alg="ed25519"
+Signature: sig1=:lyo8O1BjxYmPJchwmIO6ZwOEycijlfsLsqVpVVMiuPFAWrZ7zm0eoIF0X0wET8bsO9jiDRWjDx0b0dPK7FHPCA==:
+User-Agent: curl/%VERSION
+Accept: */*
+Content-Type: application/json
+
+</protocol>
+</verify>
+</testcase>
--- a/tests/data/test5006
+++ b/tests/data/test5006
@ -0,0 +1,56 @@
+<?xml version="1.0" encoding="US-ASCII"?>
+<testcase>
+<info>
+<keywords>
+HTTP
+httpsig
+RFC9421
+case-normalization
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data crlf="headers">
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+Content-Length: 6
+Connection: close
+Content-Type: text/html
+
+-foo-
+</data>
+</reply>
+
+# Client-side
+<client>
+<server>
+http
+</server>
+<features>
+Debug
+httpsig
+</features>
+<name>
+HTTP RFC 9421 Message Signatures: component name lowercasing
+</name>
+<command>
+"http://example.com:5100/%TESTNUMBER/resource" --httpsig-algo "ed25519" --httpsig-key %SRCDIR/data/data-httpsig-ed25519.key --httpsig-keyid "test-key-ed25519" --httpsig-headers "method Content-Type:" -H "Content-Type: text/plain" --connect-to example.com:5100:%HOSTIP:%HTTPPORT
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+<protocol crlf="headers">
+GET /%TESTNUMBER/resource HTTP/1.1
+Host: example.com:5100
+Signature-Input: sig1=("@method" "content-type");created=0;keyid="test-key-ed25519";alg="ed25519"
+Signature: sig1=:tu3WEN25K59evFpiHY5GZurVRtbaex5QM1W9b+P1rPCgNDsEEOepNZap/+nm48QZSensuc4tOpy1gbvAj25gAg==:
+User-Agent: curl/%VERSION
+Accept: */*
+Content-Type: text/plain
+
+</protocol>
+</verify>
+</testcase>
--- a/tests/data/test5007
+++ b/tests/data/test5007
@ -0,0 +1,58 @@
+<?xml version="1.0" encoding="US-ASCII"?>
+<testcase>
+<info>
+<keywords>
+HTTP
+HTTP POST
+httpsig
+RFC9421
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data crlf="headers">
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+Content-Length: 6
+Connection: close
+Content-Type: text/html
+
+-foo-
+</data>
+</reply>
+
+# Client-side
+<client>
+<server>
+http
+</server>
+<features>
+Debug
+httpsig
+</features>
+<name>
+HTTP RFC 9421 Message Signatures: POST method
+</name>
+<command>
+"http://example.com:5200/%TESTNUMBER/resource" --httpsig-algo "ed25519" --httpsig-key %SRCDIR/data/data-httpsig-ed25519.key --httpsig-keyid "test-key-ed25519" -d "postbody" --connect-to example.com:5200:%HOSTIP:%HTTPPORT
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+<protocol crlf="headers" nonewline="yes">
+POST /%TESTNUMBER/resource HTTP/1.1
+Host: example.com:5200
+Signature-Input: sig1=("@method" "@authority" "@path");created=0;keyid="test-key-ed25519";alg="ed25519"
+Signature: sig1=:fqvzBFSBFu9oys7DawypZIrt2VS+nOnN1TQ7aTLcPUbEv7Zqm4leYd0q5r9FwW+kvabAjMj8J8N8F7FmPpIWCA==:
+User-Agent: curl/%VERSION
+Accept: */*
+Content-Length: 8
+Content-Type: application/x-www-form-urlencoded
+
+postbody
+</protocol>
+</verify>
+</testcase>
--- a/tests/data/test5008
+++ b/tests/data/test5008
@ -0,0 +1,46 @@
+<?xml version="1.0" encoding="US-ASCII"?>
+<testcase>
+<info>
+<keywords>
+HTTP
+httpsig
+RFC9421
+error
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data nocheck="yes">
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+Content-Length: 0
+
+</data>
+</reply>
+
+# Client-side
+<client>
+<server>
+http
+</server>
+<features>
+Debug
+httpsig
+</features>
+<name>
+HTTP RFC 9421 Message Signatures: error - missing --httpsig-key
+</name>
+<command>
+"http://example.com/%TESTNUMBER/resource" --httpsig-algo "ed25519" --httpsig-keyid "my-key" --connect-to example.com::%HOSTIP:%HTTPPORT
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+<errorcode>
+2
+</errorcode>
+</verify>
+</testcase>
--- a/tests/data/test5009
+++ b/tests/data/test5009
@ -0,0 +1,46 @@
+<?xml version="1.0" encoding="US-ASCII"?>
+<testcase>
+<info>
+<keywords>
+HTTP
+httpsig
+RFC9421
+error
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data nocheck="yes">
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+Content-Length: 0
+
+</data>
+</reply>
+
+# Client-side
+<client>
+<server>
+http
+</server>
+<features>
+Debug
+httpsig
+</features>
+<name>
+HTTP RFC 9421 Message Signatures: error - unsupported algorithm
+</name>
+<command>
+"http://example.com/%TESTNUMBER/resource" --httpsig-algo "rsa-pss-sha512" --httpsig-key %SRCDIR/data/data-httpsig-ed25519.key --httpsig-keyid "my-key" --connect-to example.com::%HOSTIP:%HTTPPORT
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+<errorcode>
+2
+</errorcode>
+</verify>
+</testcase>
--- a/tests/data/test5010
+++ b/tests/data/test5010
@ -0,0 +1,46 @@
+<?xml version="1.0" encoding="US-ASCII"?>
+<testcase>
+<info>
+<keywords>
+HTTP
+httpsig
+RFC9421
+error
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data nocheck="yes">
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+Content-Length: 0
+
+</data>
+</reply>
+
+# Client-side
+<client>
+<server>
+http
+</server>
+<features>
+Debug
+httpsig
+</features>
+<name>
+HTTP RFC 9421 Message Signatures: error - non-existent key file
+</name>
+<command>
+"http://example.com/%TESTNUMBER/resource" --httpsig-algo "ed25519" --httpsig-key /nonexistent/key.hex --httpsig-keyid "my-key" --connect-to example.com::%HOSTIP:%HTTPPORT
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+<errorcode>
+26
+</errorcode>
+</verify>
+</testcase>
--- a/tests/data/test5011
+++ b/tests/data/test5011
@ -0,0 +1,55 @@
+<?xml version="1.0" encoding="US-ASCII"?>
+<testcase>
+<info>
+<keywords>
+HTTP
+httpsig
+RFC9421
+query-special-chars
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data crlf="headers">
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+Content-Length: 6
+Connection: close
+Content-Type: text/html
+
+-foo-
+</data>
+</reply>
+
+# Client-side
+<client>
+<server>
+http
+</server>
+<features>
+Debug
+httpsig
+</features>
+<name>
+HTTP RFC 9421 Message Signatures: query string with special characters
+</name>
+<command>
+"http://example.com:5300/%TESTNUMBER/resource?name=me%AMPnoval%AMPaim=b%25ad" --httpsig-algo "ed25519" --httpsig-key %SRCDIR/data/data-httpsig-ed25519.key --httpsig-keyid "test-key-ed25519" --connect-to example.com:5300:%HOSTIP:%HTTPPORT
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+<protocol crlf="headers">
+GET /%TESTNUMBER/resource?name=me%AMPnoval%AMPaim=b%25ad HTTP/1.1
+Host: example.com:5300
+Signature-Input: sig1=("@method" "@authority" "@path" "@query");created=0;keyid="test-key-ed25519";alg="ed25519"
+Signature: sig1=:ZFaJcDMTJEBbr90c0FaqupdJYDhNSz1i/eVCpMTDJ+1phLql2U4ROLiO26SGL6D0Nd5rr/3VXbDcWJ2vnV6IBA==:
+User-Agent: curl/%VERSION
+Accept: */*
+
+</protocol>
+</verify>
+</testcase>
--- a/tests/data/test5012
+++ b/tests/data/test5012
@ -0,0 +1,58 @@
+<?xml version="1.0" encoding="US-ASCII"?>
+<testcase>
+<info>
+<keywords>
+HTTP
+httpsig
+RFC9421
+default-port
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data crlf="headers">
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+Content-Length: 6
+Connection: close
+Content-Type: text/html
+
+-foo-
+</data>
+</reply>
+
+# Client-side
+<client>
+<server>
+http
+</server>
+<features>
+Debug
+httpsig
+</features>
+<name>
+HTTP RFC 9421 Message Signatures: default port omitted from @authority
+</name>
+<command>
+"http://example.com/%TESTNUMBER/resource" --httpsig-algo "ed25519" --httpsig-key %SRCDIR/data/data-httpsig-ed25519.key --httpsig-keyid "test-key-ed25519" --connect-to example.com::%HOSTIP:%HTTPPORT
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+<strippart>
+s/Signature: sig1=:.*:/Signature: sig1=:STRIPPED:/
+</strippart>
+<protocol crlf="headers">
+GET /%TESTNUMBER/resource HTTP/1.1
+Host: example.com
+Signature-Input: sig1=("@method" "@authority" "@path");created=0;keyid="test-key-ed25519";alg="ed25519"
+Signature: sig1=:STRIPPED:
+User-Agent: curl/%VERSION
+Accept: */*
+
+</protocol>
+</verify>
+</testcase>
--- a/tests/data/test5013
+++ b/tests/data/test5013
@ -0,0 +1,58 @@
+<?xml version="1.0" encoding="US-ASCII"?>
+<testcase>
+<info>
+<keywords>
+HTTP
+httpsig
+RFC9421
+non-default-port
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data crlf="headers">
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+Content-Length: 6
+Connection: close
+Content-Type: text/html
+
+-foo-
+</data>
+</reply>
+
+# Client-side
+<client>
+<server>
+http
+</server>
+<features>
+Debug
+httpsig
+</features>
+<name>
+HTTP RFC 9421 Message Signatures: non-default port in @authority
+</name>
+<command>
+"http://example.com:9000/%TESTNUMBER/resource" --httpsig-algo "ed25519" --httpsig-key %SRCDIR/data/data-httpsig-ed25519.key --httpsig-keyid "test-key-ed25519" --connect-to example.com:9000:%HOSTIP:%HTTPPORT
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+<strippart>
+s/Signature: sig1=:.*:/Signature: sig1=:STRIPPED:/
+</strippart>
+<protocol crlf="headers">
+GET /%TESTNUMBER/resource HTTP/1.1
+Host: example.com:9000
+Signature-Input: sig1=("@method" "@authority" "@path");created=0;keyid="test-key-ed25519";alg="ed25519"
+Signature: sig1=:STRIPPED:
+User-Agent: curl/%VERSION
+Accept: */*
+
+</protocol>
+</verify>
+</testcase>
--- a/tests/data/test5014
+++ b/tests/data/test5014
@ -0,0 +1,58 @@
+<?xml version="1.0" encoding="US-ASCII"?>
+<testcase>
+<info>
+<keywords>
+HTTP
+httpsig
+RFC9421
+empty-query
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data crlf="headers">
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+Content-Length: 6
+Connection: close
+Content-Type: text/html
+
+-foo-
+</data>
+</reply>
+
+# Client-side
+<client>
+<server>
+http
+</server>
+<features>
+Debug
+httpsig
+</features>
+<name>
+HTTP RFC 9421 Message Signatures: @query explicitly requested, no query in URL
+</name>
+<command>
+"http://example.com:5400/%TESTNUMBER/resource" --httpsig-algo "ed25519" --httpsig-key %SRCDIR/data/data-httpsig-ed25519.key --httpsig-keyid "test-key-ed25519" --httpsig-headers "method authority query" --connect-to example.com:5400:%HOSTIP:%HTTPPORT
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+<strippart>
+s/Signature: sig1=:.*:/Signature: sig1=:STRIPPED:/
+</strippart>
+<protocol crlf="headers">
+GET /%TESTNUMBER/resource HTTP/1.1
+Host: example.com:5400
+Signature-Input: sig1=("@method" "@authority" "@query");created=0;keyid="test-key-ed25519";alg="ed25519"
+Signature: sig1=:STRIPPED:
+User-Agent: curl/%VERSION
+Accept: */*
+
+</protocol>
+</verify>
+</testcase>
--- a/tests/data/test5015
+++ b/tests/data/test5015
@ -0,0 +1,62 @@
+<?xml version="1.0" encoding="US-ASCII"?>
+<testcase>
+<info>
+<keywords>
+HTTP
+HTTP POST
+httpsig
+RFC9421
+hmac-sha256
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data crlf="headers">
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+Content-Length: 6
+Connection: close
+Content-Type: text/html
+
+-foo-
+</data>
+</reply>
+
+# Client-side
+<client>
+<server>
+http
+</server>
+<features>
+Debug
+httpsig
+</features>
+<name>
+HTTP RFC 9421 Message Signatures: POST with HMAC-SHA256
+</name>
+<command>
+"http://example.com:5500/%TESTNUMBER/resource" --httpsig-algo "hmac-sha256" --httpsig-key %SRCDIR/data/data-httpsig-hmac-sha256.key --httpsig-keyid "shared-key-1" -d "postbody" --connect-to example.com:5500:%HOSTIP:%HTTPPORT
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+<strippart>
+s/Signature: sig1=:.*:/Signature: sig1=:STRIPPED:/
+</strippart>
+<protocol crlf="headers" nonewline="yes">
+POST /%TESTNUMBER/resource HTTP/1.1
+Host: example.com:5500
+Signature-Input: sig1=("@method" "@authority" "@path");created=0;keyid="shared-key-1";alg="hmac-sha256"
+Signature: sig1=:STRIPPED:
+User-Agent: curl/%VERSION
+Accept: */*
+Content-Length: 8
+Content-Type: application/x-www-form-urlencoded
+
+postbody
+</protocol>
+</verify>
+</testcase>
--- a/tests/data/test5016
+++ b/tests/data/test5016
@ -0,0 +1,60 @@
+<?xml version="1.0" encoding="US-ASCII"?>
+<testcase>
+<info>
+<keywords>
+HTTP
+httpsig
+RFC9421
+hmac-sha256
+header-signing
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data crlf="headers">
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+Content-Length: 6
+Connection: close
+Content-Type: text/html
+
+-foo-
+</data>
+</reply>
+
+# Client-side
+<client>
+<server>
+http
+</server>
+<features>
+Debug
+httpsig
+</features>
+<name>
+HTTP RFC 9421 Message Signatures: HMAC-SHA256 with custom headers
+</name>
+<command>
+"http://example.com:5600/%TESTNUMBER/resource" --httpsig-algo "hmac-sha256" --httpsig-key %SRCDIR/data/data-httpsig-hmac-sha256.key --httpsig-keyid "shared-key-1" --httpsig-headers "method authority content-type:" -H "Content-Type: application/json" --connect-to example.com:5600:%HOSTIP:%HTTPPORT
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+<strippart>
+s/Signature: sig1=:.*:/Signature: sig1=:STRIPPED:/
+</strippart>
+<protocol crlf="headers">
+GET /%TESTNUMBER/resource HTTP/1.1
+Host: example.com:5600
+Signature-Input: sig1=("@method" "@authority" "content-type");created=0;keyid="shared-key-1";alg="hmac-sha256"
+Signature: sig1=:STRIPPED:
+User-Agent: curl/%VERSION
+Accept: */*
+Content-Type: application/json
+
+</protocol>
+</verify>
+</testcase>
--- a/tests/data/test5017
+++ b/tests/data/test5017
@ -0,0 +1,55 @@
+<?xml version="1.0" encoding="US-ASCII"?>
+<testcase>
+<info>
+<keywords>
+HTTP
+httpsig
+RFC9421
+preexisting-signature
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data crlf="headers">
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+Content-Length: 6
+Connection: close
+Content-Type: text/html
+
+-foo-
+</data>
+</reply>
+
+# Client-side
+<client>
+<server>
+http
+</server>
+<features>
+Debug
+httpsig
+</features>
+<name>
+HTTP RFC 9421 Message Signatures: user-supplied Signature header skips signing
+</name>
+<command>
+"http://example.com:5700/%TESTNUMBER/resource" --httpsig-algo "ed25519" --httpsig-key %SRCDIR/data/data-httpsig-ed25519.key --httpsig-keyid "test-key-ed25519" -H "Signature: preexisting" -H "Signature-Input: preexisting" --connect-to example.com:5700:%HOSTIP:%HTTPPORT
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+<protocol crlf="headers">
+GET /%TESTNUMBER/resource HTTP/1.1
+Host: example.com:5700
+User-Agent: curl/%VERSION
+Accept: */*
+Signature: preexisting
+Signature-Input: preexisting
+
+</protocol>
+</verify>
+</testcase>
--- a/tests/data/test5018
+++ b/tests/data/test5018
@ -0,0 +1,63 @@
+<?xml version="1.0" encoding="US-ASCII"?>
+<testcase>
+<info>
+<keywords>
+HTTP
+HTTP PUT
+httpsig
+RFC9421
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data crlf="headers">
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+Content-Length: 6
+Connection: close
+Content-Type: text/html
+
+-foo-
+</data>
+</reply>
+
+# Client-side
+<client>
+<server>
+http
+</server>
+<features>
+Debug
+httpsig
+</features>
+<file name="log/upload5018">
+putdata
+</file>
+<name>
+HTTP RFC 9421 Message Signatures: PUT upload
+</name>
+<command>
+"http://example.com:5800/%TESTNUMBER/resource" --httpsig-algo "ed25519" --httpsig-key %SRCDIR/data/data-httpsig-ed25519.key --httpsig-keyid "test-key-ed25519" -T log/upload5018 --connect-to example.com:5800:%HOSTIP:%HTTPPORT
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+<strippart>
+s/Signature: sig1=:.*:/Signature: sig1=:STRIPPED:/
+</strippart>
+<protocol crlf="headers">
+PUT /%TESTNUMBER/resource HTTP/1.1
+Host: example.com:5800
+Signature-Input: sig1=("@method" "@authority" "@path");created=0;keyid="test-key-ed25519";alg="ed25519"
+Signature: sig1=:STRIPPED:
+User-Agent: curl/%VERSION
+Accept: */*
+Content-Length: 8
+
+putdata
+</protocol>
+</verify>
+</testcase>
--- a/tests/data/test5019
+++ b/tests/data/test5019
@ -0,0 +1,46 @@
+<?xml version="1.0" encoding="US-ASCII"?>
+<testcase>
+<info>
+<keywords>
+HTTP
+httpsig
+RFC9421
+error
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data nocheck="yes">
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+Content-Length: 0
+
+</data>
+</reply>
+
+# Client-side
+<client>
+<server>
+http
+</server>
+<features>
+Debug
+httpsig
+</features>
+<name>
+HTTP RFC 9421 Message Signatures: error - duplicate component
+</name>
+<command>
+"http://example.com/%TESTNUMBER/resource" --httpsig-algo "ed25519" --httpsig-key %SRCDIR/data/data-httpsig-ed25519.key --httpsig-keyid "my-key" --httpsig-headers "method method" --connect-to example.com::%HOSTIP:%HTTPPORT
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+<errorcode>
+43
+</errorcode>
+</verify>
+</testcase>
--- a/tests/data/test5020
+++ b/tests/data/test5020
@ -0,0 +1,46 @@
+<?xml version="1.0" encoding="US-ASCII"?>
+<testcase>
+<info>
+<keywords>
+HTTP
+httpsig
+RFC9421
+error
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data nocheck="yes">
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+Content-Length: 0
+
+</data>
+</reply>
+
+# Client-side
+<client>
+<server>
+http
+</server>
+<features>
+Debug
+httpsig
+</features>
+<name>
+HTTP RFC 9421 Message Signatures: error - rejects legacy '@' component syntax
+</name>
+<command>
+"http://example.com/%TESTNUMBER/resource" --httpsig-algo "ed25519" --httpsig-key %SRCDIR/data/data-httpsig-ed25519.key --httpsig-keyid "my-key" --httpsig-headers "@method authority" --connect-to example.com::%HOSTIP:%HTTPPORT
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+<errorcode>
+43
+</errorcode>
+</verify>
+</testcase>
--- a/tests/data/test5021
+++ b/tests/data/test5021
@ -0,0 +1,57 @@
+<?xml version="1.0" encoding="US-ASCII"?>
+<testcase>
+<info>
+<keywords>
+HTTP
+httpsig
+RFC9421
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data crlf="headers">
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+Content-Length: 6
+Connection: close
+Content-Type: text/html
+
+-foo-
+</data>
+</reply>
+
+# Client-side
+<client>
+<server>
+http
+</server>
+<features>
+Debug
+httpsig
+</features>
+<name>
+HTTP RFC 9421 Message Signatures: default algorithm (ed25519) when --httpsig-algo omitted
+</name>
+<command>
+"http://example.com:6100/%TESTNUMBER/resource" --httpsig-key %SRCDIR/data/data-httpsig-ed25519.key --httpsig-keyid "test-key-ed25519" --connect-to example.com:6100:%HOSTIP:%HTTPPORT
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+<strippart>
+s/Signature: sig1=:.*:/Signature: sig1=:STRIPPED:/
+</strippart>
+<protocol crlf="headers">
+GET /%TESTNUMBER/resource HTTP/1.1
+Host: example.com:6100
+Signature-Input: sig1=("@method" "@authority" "@path");created=0;keyid="test-key-ed25519";alg="ed25519"
+Signature: sig1=:STRIPPED:
+User-Agent: curl/%VERSION
+Accept: */*
+
+</protocol>
+</verify>
+</testcase>
--- a/tests/libtest/Makefile.inc
+++ b/tests/libtest/Makefile.inc
@ -124,4 +124,5 @@ TESTS_C = \
  lib2700.c \
  lib3010.c lib3025.c lib3026.c lib3027.c lib3033.c lib3034.c \
  lib3100.c lib3101.c lib3102.c lib3103.c lib3104.c lib3105.c \
-  lib3207.c lib3208.c
+  lib3207.c lib3208.c \
+  lib5000.c lib5004.c
--- a/tests/libtest/lib5000.c
+++ b/tests/libtest/lib5000.c
@ -0,0 +1,66 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ * SPDX-License-Identifier: curl
+ *
+ ***************************************************************************/
+#include "first.h"
+
+static CURLcode test_lib5000(const char *URL)
+{
+  CURL *curl;
+  CURLcode result = TEST_ERR_MAJOR_BAD;
+  struct curl_slist *connect_to = NULL;
+
+  if(curl_global_init(CURL_GLOBAL_ALL) != CURLE_OK) {
+    curl_mfprintf(stderr, "curl_global_init() failed\n");
+    return TEST_ERR_MAJOR_BAD;
+  }
+
+  curl = curl_easy_init();
+  if(!curl) {
+    curl_mfprintf(stderr, "curl_easy_init() failed\n");
+    curl_global_cleanup();
+    return TEST_ERR_MAJOR_BAD;
+  }
+
+  easy_setopt(curl, CURLOPT_VERBOSE, 1L);
+  easy_setopt(curl, CURLOPT_HTTPSIG_ALGORITHM, (long)CURLHTTPSIG_ED25519);
+  easy_setopt(curl, CURLOPT_HTTPSIG_KEY,
+              "9f8362f87a484a954e6e740c5b4c0e84"
+              "229139a20aa8ab56ff66586f6a7d29c5");
+  easy_setopt(curl, CURLOPT_HTTPSIG_KEYID, "test-key-ed25519");
+  easy_setopt(curl, CURLOPT_HEADER, 0L);
+  easy_setopt(curl, CURLOPT_URL, URL);
+  if(libtest_arg2) {
+    connect_to = curl_slist_append(connect_to, libtest_arg2);
+  }
+  easy_setopt(curl, CURLOPT_CONNECT_TO, connect_to);
+
+  result = curl_easy_perform(curl);
+
+test_cleanup:
+
+  curl_slist_free_all(connect_to);
+  curl_easy_cleanup(curl);
+  curl_global_cleanup();
+
+  return result;
+}
--- a/tests/libtest/lib5004.c
+++ b/tests/libtest/lib5004.c
@ -0,0 +1,85 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ * SPDX-License-Identifier: curl
+ *
+ ***************************************************************************/
+
+/* RFC 9421 Appendix B.2.6 test vector: Ed25519 signing of a POST request
+ * with headers. Uses CURL_HTTPSIG_CREATED=1618884473 to match the RFC
+ * expected timestamp. */
+
+#include "first.h"
+
+static CURLcode test_lib5004(const char *URL)
+{
+  CURL *curl;
+  CURLcode result = TEST_ERR_MAJOR_BAD;
+  struct curl_slist *connect_to = NULL;
+  struct curl_slist *headers = NULL;
+
+  if(curl_global_init(CURL_GLOBAL_ALL) != CURLE_OK) {
+    curl_mfprintf(stderr, "curl_global_init() failed\n");
+    return TEST_ERR_MAJOR_BAD;
+  }
+
+  curl = curl_easy_init();
+  if(!curl) {
+    curl_mfprintf(stderr, "curl_easy_init() failed\n");
+    curl_global_cleanup();
+    return TEST_ERR_MAJOR_BAD;
+  }
+
+  easy_setopt(curl, CURLOPT_VERBOSE, 1L);
+  easy_setopt(curl, CURLOPT_HTTPSIG_ALGORITHM, (long)CURLHTTPSIG_ED25519);
+  easy_setopt(curl, CURLOPT_HTTPSIG_KEY,
+              "9f8362f87a484a954e6e740c5b4c0e84"
+              "229139a20aa8ab56ff66586f6a7d29c5");
+  easy_setopt(curl, CURLOPT_HTTPSIG_KEYID, "test-key-ed25519");
+  easy_setopt(curl, CURLOPT_HTTPSIG_HEADERS,
+              "date: method path authority content-type: content-length:");
+  easy_setopt(curl, CURLOPT_POSTFIELDS, "{\"hello\": \"world\"}");
+
+  headers = curl_slist_append(headers,
+                              "Date: Tue, 20 Apr 2021 02:07:55 GMT");
+  headers = curl_slist_append(headers,
+                              "Content-Type: application/json");
+  headers = curl_slist_append(headers,
+                              "Content-Length: 18");
+  easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
+
+  easy_setopt(curl, CURLOPT_HEADER, 0L);
+  easy_setopt(curl, CURLOPT_URL, URL);
+  if(libtest_arg2) {
+    connect_to = curl_slist_append(connect_to, libtest_arg2);
+  }
+  easy_setopt(curl, CURLOPT_CONNECT_TO, connect_to);
+
+  result = curl_easy_perform(curl);
+
+test_cleanup:
+
+  curl_slist_free_all(headers);
+  curl_slist_free_all(connect_to);
+  curl_easy_cleanup(curl);
+  curl_global_cleanup();
+
+  return result;
+}
				`@ -0,0 +1 @@`
				`9f8362f87a484a954e6e740c5b4c0e84229139a20aa8ab56ff66586f6a7d29c5`
				`@ -0,0 +1 @@`
				`0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef`