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curl/lib/curl_sasl.c
Eldar Zaitov f206d6c055 Curl_sasl_create_digest_md5_message: fix buffer overflow 
When negotiating SASL DIGEST-MD5 authentication, the function
Curl_sasl_create_digest_md5_message() uses the data provided from the
server without doing the proper length checks and that data is then
appended to a local fixed-size buffer on the stack.

This vulnerability can be exploited by someone who is in control of a
server that a libcurl based program is accessing with POP3, SMTP or
IMAP. For applications that accept user provided URLs, it is also
thinkable that a malicious user would feed an application with a URL to
a server hosting code targetting this flaw.

Bug: http://curl.haxx.se/docs/adv_20130206.html
2013-02-06 11:06:33 +01:00

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/***************************************************************************
* _ _ ____ _
* Project ___| | | | _ \| |
* / __| | | | |_) | |
* | (__| |_| | _ <| |___
* \___|\___/|_| \_\_____|
*
* Copyright (C) 2012-2013, 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 http://curl.haxx.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.
*
* RFC2195 CRAM-MD5 authentication
* RFC2831 DIGEST-MD5 authentication
* RFC4422 Simple Authentication and Security Layer (SASL)
* RFC4616 PLAIN authentication
*
***************************************************************************/
#include "curl_setup.h"
#include <curl/curl.h>
#include "urldata.h"
#include "curl_base64.h"
#include "curl_md5.h"
#include "curl_rand.h"
#include "curl_hmac.h"
#include "curl_ntlm_msgs.h"
#include "curl_sasl.h"
#include "warnless.h"
#include "curl_memory.h"
#define _MPRINTF_REPLACE /* use our functions only */
#include <curl/mprintf.h>
/* The last #include file should be: */
#include "memdebug.h"
#ifndef CURL_DISABLE_CRYPTO_AUTH
/* Retrieves the value for a corresponding key from the challenge string
* returns TRUE if the key could be found, FALSE if it does not exists
*/
static bool sasl_digest_get_key_value(const unsigned char *chlg,
const char *key,
char *value,
size_t max_val_len,
char end_char)
{
char *find_pos;
size_t i;
find_pos = strstr((const char *) chlg, key);
if(!find_pos)
return FALSE;
find_pos += strlen(key);
for(i = 0; *find_pos && *find_pos != end_char && i < max_val_len - 1; ++i)
value[i] = *find_pos++;
value[i] = '\0';
return TRUE;
}
#endif
/*
* Curl_sasl_create_plain_message()
*
* This is used to generate an already encoded PLAIN message ready
* for sending to the recipient.
*
* Parameters:
*
* data [in] - The session handle.
* userp [in] - The user name.
* passdwp [in] - The user's password.
* outptr [in/out] - The address where a pointer to newly allocated memory
* holding the result will be stored upon completion.
* outlen [out] - The length of the output message.
*
* Returns CURLE_OK on success.
*/
CURLcode Curl_sasl_create_plain_message(struct SessionHandle *data,
const char* userp,
const char* passwdp,
char **outptr, size_t *outlen)
{
char plainauth[2 * MAX_CURL_USER_LENGTH + MAX_CURL_PASSWORD_LENGTH];
size_t ulen;
size_t plen;
ulen = strlen(userp);
plen = strlen(passwdp);
if(2 * ulen + plen + 2 > sizeof(plainauth)) {
*outlen = 0;
*outptr = NULL;
/* Plainauth too small */
return CURLE_OUT_OF_MEMORY;
}
/* Calculate the reply */
memcpy(plainauth, userp, ulen);
plainauth[ulen] = '\0';
memcpy(plainauth + ulen + 1, userp, ulen);
plainauth[2 * ulen + 1] = '\0';
memcpy(plainauth + 2 * ulen + 2, passwdp, plen);
/* Base64 encode the reply */
return Curl_base64_encode(data, plainauth, 2 * ulen + plen + 2, outptr,
outlen);
}
/*
* Curl_sasl_create_login_message()
*
* This is used to generate an already encoded LOGIN message containing the
* user name or password ready for sending to the recipient.
*
* Parameters:
*
* data [in] - The session handle.
* valuep [in] - The user name or user's password.
* outptr [in/out] - The address where a pointer to newly allocated memory
* holding the result will be stored upon completion.
* outlen [out] - The length of the output message.
*
* Returns CURLE_OK on success.
*/
CURLcode Curl_sasl_create_login_message(struct SessionHandle *data,
const char* valuep, char **outptr,
size_t *outlen)
{
size_t vlen = strlen(valuep);
if(!vlen) {
/* Calculate an empty reply */
*outptr = strdup("=");
if(*outptr) {
*outlen = (size_t) 1;
return CURLE_OK;
}
*outlen = 0;
return CURLE_OUT_OF_MEMORY;
}
/* Base64 encode the value */
return Curl_base64_encode(data, valuep, vlen, outptr, outlen);
}
#ifndef CURL_DISABLE_CRYPTO_AUTH
/*
* Curl_sasl_create_cram_md5_message()
*
* This is used to generate an already encoded CRAM-MD5 response message ready
* for sending to the recipient.
*
* Parameters:
*
* data [in] - The session handle.
* chlg64 [in] - Pointer to the base64 encoded challenge buffer.
* userp [in] - The user name.
* passdwp [in] - The user's password.
* outptr [in/out] - The address where a pointer to newly allocated memory
* holding the result will be stored upon completion.
* outlen [out] - The length of the output message.
*
* Returns CURLE_OK on success.
*/
CURLcode Curl_sasl_create_cram_md5_message(struct SessionHandle *data,
const char* chlg64,
const char* userp,
const char* passwdp,
char **outptr, size_t *outlen)
{
CURLcode result = CURLE_OK;
size_t chlg64len = strlen(chlg64);
unsigned char *chlg = (unsigned char *) NULL;
size_t chlglen = 0;
HMAC_context *ctxt;
unsigned char digest[MD5_DIGEST_LEN];
char response[MAX_CURL_USER_LENGTH + 2 * MD5_DIGEST_LEN + 1];
/* Decode the challenge if necessary */
if(chlg64len && *chlg64 != '=') {
result = Curl_base64_decode(chlg64, &chlg, &chlglen);
if(result)
return result;
}
/* Compute the digest using the password as the key */
ctxt = Curl_HMAC_init(Curl_HMAC_MD5,
(const unsigned char *) passwdp,
curlx_uztoui(strlen(passwdp)));
if(!ctxt) {
Curl_safefree(chlg);
return CURLE_OUT_OF_MEMORY;
}
/* Update the digest with the given challenge */
if(chlglen > 0)
Curl_HMAC_update(ctxt, chlg, curlx_uztoui(chlglen));
Curl_safefree(chlg);
/* Finalise the digest */
Curl_HMAC_final(ctxt, digest);
/* Prepare the response */
snprintf(response, sizeof(response),
"%s %02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x",
userp, digest[0], digest[1], digest[2], digest[3], digest[4],
digest[5], digest[6], digest[7], digest[8], digest[9], digest[10],
digest[11], digest[12], digest[13], digest[14], digest[15]);
/* Base64 encode the reply */
return Curl_base64_encode(data, response, 0, outptr, outlen);
}
/*
* Curl_sasl_create_digest_md5_message()
*
* This is used to generate an already encoded DIGEST-MD5 response message
* ready for sending to the recipient.
*
* Parameters:
*
* data [in] - The session handle.
* chlg64 [in] - Pointer to the base64 encoded challenge buffer.
* userp [in] - The user name.
* passdwp [in] - The user's password.
* service [in] - The service type such as www, smtp or pop
* outptr [in/out] - The address where a pointer to newly allocated memory
* holding the result will be stored upon completion.
* outlen [out] - The length of the output message.
*
* Returns CURLE_OK on success.
*/
CURLcode Curl_sasl_create_digest_md5_message(struct SessionHandle *data,
const char* chlg64,
const char* userp,
const char* passwdp,
const char* service,
char **outptr, size_t *outlen)
{
static const char table16[] = "0123456789abcdef";
CURLcode result = CURLE_OK;
unsigned char *chlg = (unsigned char *) NULL;
size_t chlglen = 0;
size_t i;
MD5_context *ctxt;
unsigned char digest[MD5_DIGEST_LEN];
char HA1_hex[2 * MD5_DIGEST_LEN + 1];
char HA2_hex[2 * MD5_DIGEST_LEN + 1];
char resp_hash_hex[2 * MD5_DIGEST_LEN + 1];
char nonce[64];
char realm[128];
char alg[64];
char nonceCount[] = "00000001";
char cnonce[] = "12345678"; /* will be changed */
char method[] = "AUTHENTICATE";
char qop[] = "auth";
char uri[128];
char response[512];
result = Curl_base64_decode(chlg64, &chlg, &chlglen);
if(result)
return result;
/* Retrieve nonce string from the challenge */
if(!sasl_digest_get_key_value(chlg, "nonce=\"", nonce,
sizeof(nonce), '\"')) {
Curl_safefree(chlg);
return CURLE_LOGIN_DENIED;
}
/* Retrieve realm string from the challenge */
if(!sasl_digest_get_key_value(chlg, "realm=\"", realm,
sizeof(realm), '\"')) {
/* Challenge does not have a realm, set empty string [RFC2831] page 6 */
strcpy(realm, "");
}
/* Retrieve algorithm string from the challenge */
if(!sasl_digest_get_key_value(chlg, "algorithm=", alg, sizeof(alg), ',')) {
Curl_safefree(chlg);
return CURLE_LOGIN_DENIED;
}
Curl_safefree(chlg);
/* We do not support other algorithms */
if(strcmp(alg, "md5-sess") != 0)
return CURLE_LOGIN_DENIED;
/* Generate 64 bits of random data */
for(i = 0; i < 8; i++)
cnonce[i] = table16[Curl_rand()%16];
/* So far so good, now calculate A1 and H(A1) according to RFC 2831 */
ctxt = Curl_MD5_init(Curl_DIGEST_MD5);
if(!ctxt)
return CURLE_OUT_OF_MEMORY;
Curl_MD5_update(ctxt, (const unsigned char *) userp,
curlx_uztoui(strlen(userp)));
Curl_MD5_update(ctxt, (const unsigned char *) ":", 1);
Curl_MD5_update(ctxt, (const unsigned char *) realm,
curlx_uztoui(strlen(realm)));
Curl_MD5_update(ctxt, (const unsigned char *) ":", 1);
Curl_MD5_update(ctxt, (const unsigned char *) passwdp,
curlx_uztoui(strlen(passwdp)));
Curl_MD5_final(ctxt, digest);
ctxt = Curl_MD5_init(Curl_DIGEST_MD5);
if(!ctxt)
return CURLE_OUT_OF_MEMORY;
Curl_MD5_update(ctxt, (const unsigned char *) digest, MD5_DIGEST_LEN);
Curl_MD5_update(ctxt, (const unsigned char *) ":", 1);
Curl_MD5_update(ctxt, (const unsigned char *) nonce,
curlx_uztoui(strlen(nonce)));
Curl_MD5_update(ctxt, (const unsigned char *) ":", 1);
Curl_MD5_update(ctxt, (const unsigned char *) cnonce,
curlx_uztoui(strlen(cnonce)));
Curl_MD5_final(ctxt, digest);
/* Convert calculated 16 octet hex into 32 bytes string */
for(i = 0; i < MD5_DIGEST_LEN; i++)
snprintf(&HA1_hex[2 * i], 3, "%02x", digest[i]);
/* Prepare the URL string */
snprintf(uri, sizeof(uri), "%s/%s", service, realm);
/* Calculate H(A2) */
ctxt = Curl_MD5_init(Curl_DIGEST_MD5);
if(!ctxt)
return CURLE_OUT_OF_MEMORY;
Curl_MD5_update(ctxt, (const unsigned char *) method,
curlx_uztoui(strlen(method)));
Curl_MD5_update(ctxt, (const unsigned char *) ":", 1);
Curl_MD5_update(ctxt, (const unsigned char *) uri,
curlx_uztoui(strlen(uri)));
Curl_MD5_final(ctxt, digest);
for(i = 0; i < MD5_DIGEST_LEN; i++)
snprintf(&HA2_hex[2 * i], 3, "%02x", digest[i]);
/* Now calculate the response hash */
ctxt = Curl_MD5_init(Curl_DIGEST_MD5);
if(!ctxt)
return CURLE_OUT_OF_MEMORY;
Curl_MD5_update(ctxt, (const unsigned char *) HA1_hex, 2 * MD5_DIGEST_LEN);
Curl_MD5_update(ctxt, (const unsigned char *) ":", 1);
Curl_MD5_update(ctxt, (const unsigned char *) nonce,
curlx_uztoui(strlen(nonce)));
Curl_MD5_update(ctxt, (const unsigned char *) ":", 1);
Curl_MD5_update(ctxt, (const unsigned char *) nonceCount,
curlx_uztoui(strlen(nonceCount)));
Curl_MD5_update(ctxt, (const unsigned char *) ":", 1);
Curl_MD5_update(ctxt, (const unsigned char *) cnonce,
curlx_uztoui(strlen(cnonce)));
Curl_MD5_update(ctxt, (const unsigned char *) ":", 1);
Curl_MD5_update(ctxt, (const unsigned char *) qop,
curlx_uztoui(strlen(qop)));
Curl_MD5_update(ctxt, (const unsigned char *) ":", 1);
Curl_MD5_update(ctxt, (const unsigned char *) HA2_hex, 2 * MD5_DIGEST_LEN);
Curl_MD5_final(ctxt, digest);
for(i = 0; i < MD5_DIGEST_LEN; i++)
snprintf(&resp_hash_hex[2 * i], 3, "%02x", digest[i]);
snprintf(response, sizeof(response),
"username=\"%s\",realm=\"%s\",nonce=\"%s\","
"cnonce=\"%s\",nc=\"%s\",digest-uri=\"%s\",response=%s",
userp, realm, nonce,
cnonce, nonceCount, uri, resp_hash_hex);
/* Base64 encode the reply */
return Curl_base64_encode(data, response, 0, outptr, outlen);
}
#endif
#ifdef USE_NTLM
/*
* Curl_sasl_create_ntlm_type1_message()
*
* This is used to generate an already encoded NTLM type-1 message ready for
* sending to the recipient.
*
* Note: This is a simple wrapper of the NTLM function which means that any
* SASL based protocols don't have to include the NTLM functions directly.
*
* Parameters:
*
* userp [in] - The user name in the format User or Domain\User.
* passdwp [in] - The user's password.
* ntlm [in/out] - The ntlm data struct being used and modified.
* outptr [in/out] - The address where a pointer to newly allocated memory
* holding the result will be stored upon completion.
* outlen [out] - The length of the output message.
*
* Returns CURLE_OK on success.
*/
CURLcode Curl_sasl_create_ntlm_type1_message(const char *userp,
const char *passwdp,
struct ntlmdata *ntlm,
char **outptr, size_t *outlen)
{
return Curl_ntlm_create_type1_message(userp, passwdp, ntlm, outptr,
outlen);
}
/*
* Curl_sasl_create_ntlm_type3_message()
*
* This is used to generate an already encoded NTLM type-3 message ready for
* sending to the recipient.
*
* Parameters:
*
* data [in] - Pointer to session handle.
* header [in] - Pointer to the base64 encoded type-2 message buffer.
* userp [in] - The user name in the format User or Domain\User.
* passdwp [in] - The user's password.
* ntlm [in/out] - The ntlm data struct being used and modified.
* outptr [in/out] - The address where a pointer to newly allocated memory
* holding the result will be stored upon completion.
* outlen [out] - The length of the output message.
*
* Returns CURLE_OK on success.
*/
CURLcode Curl_sasl_create_ntlm_type3_message(struct SessionHandle *data,
const char *header,
const char *userp,
const char *passwdp,
struct ntlmdata *ntlm,
char **outptr, size_t *outlen)
{
CURLcode result = Curl_ntlm_decode_type2_message(data, header, ntlm);
if(!result)
result = Curl_ntlm_create_type3_message(data, userp, passwdp, ntlm,
outptr, outlen);
return result;
}
#endif /* USE_NTLM */
/*
* Curl_sasl_cleanup()
*
* This is used to cleanup any libraries or curl modules used by the sasl
* functions.
*
* Parameters:
*
* conn [in] - Pointer to the connection data.
* authused [in] - The authentication mechanism used.
*/
void Curl_sasl_cleanup(struct connectdata *conn, unsigned int authused)
{
#ifdef USE_NTLM
/* Cleanup the ntlm structure */
if(authused == SASL_MECH_NTLM) {
Curl_ntlm_sspi_cleanup(&conn->ntlm);
}
(void)conn;
#else
/* Reserved for future use */
(void)conn;
(void)authused;
#endif
}
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