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curl/lib/vauth/krb5_sspi.c
Daniel Stenberg 8d3c4fe344
sspi: free libcurl allocated memory with curlx_free 
DecryptMessage() decrypts the buffer in place, overwriting the original
contents. It does not allocate any new buffer so the single original
buffer should be freed using the same memory "system" that allocated it.

Reported-by: Trail of Bits
Closes #21990
2026-06-13 23:18:59 +02:00

456 lines
15 KiB
C
Raw Blame History

/***************************************************************************
* _ _ ____ _
* Project ___| | | | _ \| |
* / __| | | | |_) | |
* | (__| |_| | _ <| |___
* \___|\___/|_| \_\_____|
*
* Copyright (C) Steve Holme, <steve_holme@hotmail.com>.
*
* 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
*
* RFC4752 The Kerberos V5 ("GSSAPI") SASL Mechanism
*
***************************************************************************/
#include "curl_setup.h"
#if defined(USE_WINDOWS_SSPI) && defined(USE_KERBEROS5)
#include "vauth/vauth.h"
#include "curl_trc.h"
/*
* Curl_auth_is_gssapi_supported()
*
* This is used to evaluate if GSSAPI (Kerberos V5) is supported.
*
* Parameters: None
*
* Returns TRUE if Kerberos V5 is supported by Windows SSPI.
*/
bool Curl_auth_is_gssapi_supported(void)
{
PSecPkgInfo SecurityPackage;
SECURITY_STATUS status;
/* Query the security package for Kerberos */
status = Curl_pSecFn->QuerySecurityPackageInfo(
(TCHAR *)CURL_UNCONST(TEXT(SP_NAME_KERBEROS)),
&SecurityPackage);
/* Release the package buffer as it is not required anymore */
if(status == SEC_E_OK) {
Curl_pSecFn->FreeContextBuffer(SecurityPackage);
}
return status == SEC_E_OK;
}
/*
* Curl_auth_create_gssapi_user_message()
*
* This is used to generate an already encoded GSSAPI (Kerberos V5) user token
* message ready for sending to the recipient.
*
* Parameters:
*
* data [in] - The session handle.
* userp [in] - The username in the format User or Domain\User.
* passwdp [in] - The user's password.
* service [in] - The service type such as http, smtp, pop or imap.
* host [in] - The hostname.
* mutual_auth [in] - Flag specifying whether or not mutual authentication
* is enabled.
* chlg [in] - Optional challenge message.
* krb5 [in/out] - The Kerberos 5 data struct being used and modified.
* out [out] - The result storage.
*
* Returns CURLE_OK on success.
*/
CURLcode Curl_auth_create_gssapi_user_message(struct Curl_easy *data,
struct Curl_creds *creds,
const char *default_service,
const char *host,
const bool mutual_auth,
const struct bufref *chlg,
struct kerberos5data *krb5,
struct bufref *out)
{
CURLcode result = CURLE_OK;
CtxtHandle context;
PSecPkgInfo SecurityPackage;
SecBuffer chlg_buf;
SecBuffer resp_buf;
SecBufferDesc chlg_desc;
SecBufferDesc resp_desc;
SECURITY_STATUS status;
unsigned long attrs;
const char *service = Curl_creds_has_sasl_service(creds) ?
Curl_creds_sasl_service(creds) : default_service;
if(!krb5->spn) {
/* Generate our SPN */
krb5->spn = Curl_auth_build_spn(service, host, NULL);
if(!krb5->spn)
return CURLE_OUT_OF_MEMORY;
}
if(!krb5->output_token) {
/* Query the security package for Kerberos */
status = Curl_pSecFn->QuerySecurityPackageInfo(
(TCHAR *)CURL_UNCONST(TEXT(SP_NAME_KERBEROS)),
&SecurityPackage);
if(status != SEC_E_OK) {
failf(data, "SSPI: could not get auth info");
return CURLE_AUTH_ERROR;
}
krb5->token_max = SecurityPackage->cbMaxToken;
/* Release the package buffer as it is not required anymore */
Curl_pSecFn->FreeContextBuffer(SecurityPackage);
/* Allocate our response buffer */
krb5->output_token = curlx_malloc(krb5->token_max);
if(!krb5->output_token)
return CURLE_OUT_OF_MEMORY;
}
if(!krb5->credentials) {
/* Do we have credentials to use or are we using single sign-on? */
if(Curl_creds_has_user(creds)) {
/* Populate our identity structure */
result = Curl_create_sspi_identity(
creds->user, creds->passwd, &krb5->identity);
if(result)
return result;
/* Allow proper cleanup of the identity structure */
krb5->p_identity = &krb5->identity;
}
else
/* Use the current Windows user */
krb5->p_identity = NULL;
/* Allocate our credentials handle */
krb5->credentials = curlx_calloc(1, sizeof(CredHandle));
if(!krb5->credentials)
return CURLE_OUT_OF_MEMORY;
/* Acquire our credentials handle */
status = Curl_pSecFn->AcquireCredentialsHandle(NULL,
(TCHAR *)CURL_UNCONST(TEXT(SP_NAME_KERBEROS)),
SECPKG_CRED_OUTBOUND, NULL,
krb5->p_identity, NULL, NULL,
krb5->credentials, NULL);
if(status != SEC_E_OK) {
curlx_safefree(krb5->credentials);
return CURLE_LOGIN_DENIED;
}
/* Allocate our new context handle */
krb5->context = curlx_calloc(1, sizeof(CtxtHandle));
if(!krb5->context)
return CURLE_OUT_OF_MEMORY;
}
if(chlg) {
if(!Curl_bufref_len(chlg)) {
infof(data, "GSSAPI handshake failure (empty challenge message)");
return CURLE_BAD_CONTENT_ENCODING;
}
/* Setup the challenge "input" security buffer */
chlg_desc.ulVersion = SECBUFFER_VERSION;
chlg_desc.cBuffers = 1;
chlg_desc.pBuffers = &chlg_buf;
chlg_buf.BufferType = SECBUFFER_TOKEN;
chlg_buf.pvBuffer = CURL_UNCONST(Curl_bufref_ptr(chlg));
chlg_buf.cbBuffer = curlx_uztoul(Curl_bufref_len(chlg));
}
/* Setup the response "output" security buffer */
resp_desc.ulVersion = SECBUFFER_VERSION;
resp_desc.cBuffers = 1;
resp_desc.pBuffers = &resp_buf;
resp_buf.BufferType = SECBUFFER_TOKEN;
resp_buf.pvBuffer = krb5->output_token;
resp_buf.cbBuffer = curlx_uztoul(krb5->token_max);
/* Generate our challenge-response message */
status = Curl_pSecFn->InitializeSecurityContext(krb5->credentials,
chlg ? krb5->context : NULL,
krb5->spn,
(mutual_auth ?
ISC_REQ_MUTUAL_AUTH : 0),
0, SECURITY_NATIVE_DREP,
chlg ? &chlg_desc : NULL, 0,
&context,
&resp_desc, &attrs, NULL);
if(status == SEC_E_INSUFFICIENT_MEMORY)
return CURLE_OUT_OF_MEMORY;
if(status != SEC_E_OK && status != SEC_I_CONTINUE_NEEDED)
return CURLE_AUTH_ERROR;
if(memcmp(&context, krb5->context, sizeof(context))) {
Curl_pSecFn->DeleteSecurityContext(krb5->context);
memcpy(krb5->context, &context, sizeof(context));
}
if(resp_buf.cbBuffer) {
result = Curl_bufref_memdup0(out, resp_buf.pvBuffer, resp_buf.cbBuffer);
}
else if(mutual_auth)
Curl_bufref_set(out, "", 0, NULL);
else
Curl_bufref_set(out, NULL, 0, NULL);
return result;
}
/*
* Curl_auth_create_gssapi_security_message()
*
* This is used to generate an already encoded GSSAPI (Kerberos V5) security
* token message ready for sending to the recipient.
*
* Parameters:
*
* data [in] - The session handle.
* authzid [in] - The authorization identity if some.
* chlg [in] - The challenge message.
* krb5 [in/out] - The Kerberos 5 data struct being used and modified.
* out [out] - The result storage.
*
* Returns CURLE_OK on success.
*/
CURLcode Curl_auth_create_gssapi_security_message(struct Curl_easy *data,
const char *authzid,
const struct bufref *chlg,
struct kerberos5data *krb5,
struct bufref *out)
{
CURLcode result = CURLE_OK;
size_t offset = 0;
size_t messagelen = 0;
size_t appdatalen = 0;
unsigned char *trailer = NULL;
unsigned char *message = NULL;
unsigned char *padding = NULL;
unsigned char *appdata = NULL;
SecBuffer input_buf[2];
SecBuffer wrap_buf[3];
SecBufferDesc input_desc;
SecBufferDesc wrap_desc;
unsigned char *indata;
unsigned long qop = 0;
unsigned long sec_layer = 0;
unsigned long max_size = 0;
SecPkgContext_Sizes sizes;
SECURITY_STATUS status;
/* Ensure we have a valid challenge message */
DEBUGASSERT(chlg);
if(!Curl_bufref_len(chlg)) {
infof(data, "GSSAPI handshake failure (empty security message)");
return CURLE_BAD_CONTENT_ENCODING;
}
/* Get our response size information */
status = Curl_pSecFn->QueryContextAttributes(krb5->context,
SECPKG_ATTR_SIZES, &sizes);
if(status == SEC_E_INSUFFICIENT_MEMORY)
return CURLE_OUT_OF_MEMORY;
if(status != SEC_E_OK)
return CURLE_AUTH_ERROR;
/* Setup the "input" security buffer */
input_desc.ulVersion = SECBUFFER_VERSION;
input_desc.cBuffers = 2;
input_desc.pBuffers = input_buf;
input_buf[0].BufferType = SECBUFFER_STREAM;
input_buf[0].pvBuffer = CURL_UNCONST(Curl_bufref_ptr(chlg));
input_buf[0].cbBuffer = curlx_uztoul(Curl_bufref_len(chlg));
input_buf[1].BufferType = SECBUFFER_DATA;
input_buf[1].pvBuffer = NULL;
input_buf[1].cbBuffer = 0;
/* Decrypt the inbound challenge and obtain the qop. The encrypted message
is decrypted in place, overwriting the original contents of its buffer.
The SECBUFFER_DATA receives a pointer to the message in
SECBUFFER_STREAM. */
status = Curl_pSecFn->DecryptMessage(krb5->context, &input_desc, 0, &qop);
if(status != SEC_E_OK) {
infof(data, "GSSAPI handshake failure (empty security message)");
return CURLE_BAD_CONTENT_ENCODING;
}
/* Not 4 octets long so fail as per RFC4752 Section 3.1 */
if(input_buf[1].cbBuffer != 4) {
infof(data, "GSSAPI handshake failure (invalid security data)");
return CURLE_BAD_CONTENT_ENCODING;
}
/* Extract the security layer and the maximum message size */
indata = input_buf[1].pvBuffer;
sec_layer = indata[0];
max_size = ((unsigned long)indata[1] << 16) |
((unsigned long)indata[2] << 8) | indata[3];
/* Process the security layer */
if(!(sec_layer & KERB_WRAP_NO_ENCRYPT)) {
infof(data, "GSSAPI handshake failure (invalid security layer)");
return CURLE_BAD_CONTENT_ENCODING;
}
sec_layer &= KERB_WRAP_NO_ENCRYPT; /* We do not support a security layer */
/* Process the maximum message size the server can receive */
if(max_size > 0) {
/* The server has told us it supports a maximum receive buffer, but as we
do not require one unless we are encrypting data, we tell the server
our receive buffer is zero. */
max_size = 0;
}
/* Allocate the trailer */
trailer = curlx_malloc(sizes.cbSecurityTrailer);
if(!trailer)
return CURLE_OUT_OF_MEMORY;
/* Allocate our message */
messagelen = 4;
if(authzid)
messagelen += strlen(authzid);
message = curlx_malloc(messagelen);
if(!message) {
result = CURLE_OUT_OF_MEMORY;
goto out;
}
/* Populate the message with the security layer and client supported receive
message size. */
message[0] = sec_layer & 0xFF;
message[1] = (max_size >> 16) & 0xFF;
message[2] = (max_size >> 8) & 0xFF;
message[3] = max_size & 0xFF;
/* If given, append the authorization identity. */
if(authzid && *authzid)
memcpy(message + 4, authzid, messagelen - 4);
/* Allocate the padding */
padding = curlx_malloc(sizes.cbBlockSize);
if(!padding) {
result = CURLE_OUT_OF_MEMORY;
goto out;
}
/* Setup the "authentication data" security buffer */
wrap_desc.ulVersion = SECBUFFER_VERSION;
wrap_desc.cBuffers = 3;
wrap_desc.pBuffers = wrap_buf;
wrap_buf[0].BufferType = SECBUFFER_TOKEN;
wrap_buf[0].pvBuffer = trailer;
wrap_buf[0].cbBuffer = sizes.cbSecurityTrailer;
wrap_buf[1].BufferType = SECBUFFER_DATA;
wrap_buf[1].pvBuffer = message;
wrap_buf[1].cbBuffer = curlx_uztoul(messagelen);
wrap_buf[2].BufferType = SECBUFFER_PADDING;
wrap_buf[2].pvBuffer = padding;
wrap_buf[2].cbBuffer = sizes.cbBlockSize;
/* Encrypt the data */
status = Curl_pSecFn->EncryptMessage(krb5->context, KERB_WRAP_NO_ENCRYPT,
&wrap_desc, 0);
if(status != SEC_E_OK) {
if(status == SEC_E_INSUFFICIENT_MEMORY)
result = CURLE_OUT_OF_MEMORY;
else
result = CURLE_AUTH_ERROR;
goto out;
}
/* Allocate the encryption (wrap) buffer */
appdatalen = wrap_buf[0].cbBuffer + wrap_buf[1].cbBuffer +
wrap_buf[2].cbBuffer;
appdata = curlx_malloc(appdatalen);
if(!appdata) {
result = CURLE_OUT_OF_MEMORY;
goto out;
}
/* Populate the encryption buffer */
memcpy(appdata, wrap_buf[0].pvBuffer, wrap_buf[0].cbBuffer);
offset += wrap_buf[0].cbBuffer;
memcpy(appdata + offset, wrap_buf[1].pvBuffer, wrap_buf[1].cbBuffer);
offset += wrap_buf[1].cbBuffer;
memcpy(appdata + offset, wrap_buf[2].pvBuffer, wrap_buf[2].cbBuffer);
out:
/* Free all of our local buffers */
curlx_free(padding);
curlx_free(message);
curlx_free(trailer);
if(result)
return result;
/* Return the response. */
Curl_bufref_set(out, appdata, appdatalen, curl_free);
return CURLE_OK;
}
/*
* Curl_auth_cleanup_gssapi()
*
* This is used to clean up the GSSAPI (Kerberos V5) specific data.
*
* Parameters:
*
* krb5 [in/out] - The Kerberos 5 data struct being cleaned up.
*
*/
void Curl_auth_cleanup_gssapi(struct kerberos5data *krb5)
{
/* Free our security context */
if(krb5->context) {
Curl_pSecFn->DeleteSecurityContext(krb5->context);
curlx_safefree(krb5->context);
}
/* Free our credentials handle */
if(krb5->credentials) {
Curl_pSecFn->FreeCredentialsHandle(krb5->credentials);
curlx_safefree(krb5->credentials);
}
/* Free our identity */
Curl_sspi_free_identity(krb5->p_identity);
krb5->p_identity = NULL;
/* Free the SPN and output token */
curlx_safefree(krb5->spn);
curlx_safefree(krb5->output_token);
/* Reset any variables */
krb5->token_max = 0;
}
#endif /* USE_WINDOWS_SSPI && USE_KERBEROS5 */
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