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161 lines
4.1 KiB
Markdown
161 lines
4.1 KiB
Markdown
---
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c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
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SPDX-License-Identifier: curl
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Title: CURLOPT_PINNEDPUBLICKEY
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Section: 3
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Source: libcurl
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See-also:
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- CURLOPT_CAINFO (3)
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- CURLOPT_CAPATH (3)
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- CURLOPT_SSL_VERIFYHOST (3)
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- CURLOPT_SSL_VERIFYPEER (3)
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Protocol:
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- TLS
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TLS-backend:
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- OpenSSL
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- GnuTLS
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- wolfSSL
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- mbedTLS
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- Schannel
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Added-in: 7.39.0
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---
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# NAME
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CURLOPT_PINNEDPUBLICKEY - pinned public key
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# SYNOPSIS
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~~~c
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#include <curl/curl.h>
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CURLcode curl_easy_setopt(CURL *handle, CURLOPT_PINNEDPUBLICKEY,
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char *pinnedpubkey);
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~~~
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# DESCRIPTION
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Pass a pointer to a null-terminated string as parameter. The string can be the
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filename of your pinned public key. The file format expected is `PEM` or
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`DER`. The string can also be any number of base64 encoded sha256 hashes
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preceded by `sha256//` and separated by `;`.
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When negotiating a TLS or SSL connection, the server sends a certificate
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indicating its identity. A public key is extracted from this certificate and
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if it does not exactly match the public key provided to this option, curl
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aborts the connection before sending or receiving any data.
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This option is independent of option CURLOPT_SSL_VERIFYPEER(3). If you turn
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off that option then the peer is still verified by public key.
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On mismatch, *CURLE_SSL_PINNEDPUBKEYNOTMATCH* is returned.
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The application does not have to keep the string around after setting this
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option.
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The pinned public key is used to verify the initial origin used in a transfer.
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If the transfer is set to follow redirects to other origins, they are *not*
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checked against this key.
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This option has no effect on LDAP connections when libcurl uses the legacy LDAP
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backend. That backend manages TLS independently of curl's TLS layer. When
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libcurl is built with USE_OPENLDAP, the OpenLDAP backend routes TLS through
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curl's layer and this option is honored.
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# DEFAULT
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NULL
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# %PROTOCOLS%
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# EXAMPLE
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~~~c
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int main(void)
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{
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CURL *curl = curl_easy_init();
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if(curl) {
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CURLcode result;
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curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
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curl_easy_setopt(curl, CURLOPT_PINNEDPUBLICKEY, "/etc/publickey.der");
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/* OR
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curl_easy_setopt(curl, CURLOPT_PINNEDPUBLICKEY,
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"sha256//YhKJKSzoTt2b5FP18fvpHo7fJYqQCjAa3HWY3"
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"tvRMwE=;sha256//t62CeU2tQiqkexU74Gxa2eg7fRbEg"
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"oChTociMee9wno=");
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*/
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/* Perform the request */
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result = curl_easy_perform(curl);
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curl_easy_cleanup(curl);
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}
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}
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~~~
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# PUBLIC KEY EXTRACTION
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If you do not have the server's public key file you can extract it from the
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server's certificate.
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~~~
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# retrieve the server's certificate if you do not already have it
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#
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# be sure to examine the certificate to see if it is what you expected
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#
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# Windows-specific:
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# - Use NUL instead of /dev/null.
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# - OpenSSL may wait for input instead of disconnecting. Hit enter.
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# - If you do not have sed, then copy the certificate into a file:
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# Lines from -----BEGIN CERTIFICATE----- to -----END CERTIFICATE-----.
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#
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openssl s_client -servername www.example.com -connect www.example.com:443 \
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< /dev/null | sed -n "/-----BEGIN/,/-----END/p" > www.example.com.pem
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# extract public key in pem format from certificate
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openssl x509 -in www.example.com.pem -pubkey -noout > www.example.com.pubkey.pem
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# convert public key from pem to der
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openssl asn1parse -noout -inform pem -in www.example.com.pubkey.pem \
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-out www.example.com.pubkey.der
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# sha256 hash and base64 encode der to string for use
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openssl dgst -sha256 -binary www.example.com.pubkey.der | openssl base64
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~~~
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The public key in PEM format contains a header, base64 data and a
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footer:
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~~~
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-----BEGIN PUBLIC KEY-----
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[BASE 64 DATA]
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-----END PUBLIC KEY-----
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~~~
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# HISTORY
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## PEM/DER support
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7.39.0: OpenSSL, GnuTLS
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7.43.0: wolfSSL
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7.47.0: mbedTLS
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7.58.1: Schannel
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## sha256 support
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7.44.0: OpenSSL, GnuTLS and wolfSSL
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7.47.0: mbedTLS
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7.58.1: Schannel
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Other SSL backends not supported.
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# %AVAILABILITY%
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# RETURN VALUE
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curl_easy_setopt(3) returns a CURLcode indicating success or error.
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CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
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libcurl-errors(3).
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