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Merge remote-tracking branch 'restricted/pr/468' into mbedtls-2.7-restricted-proposed

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* restricted/pr/468:
  Improve comments style
  Remove a redundant test
  Add buffer size check before cert_type_len read
  Update change log
  Add a missing buffer size check
  Correct buffer size check
This commit is contained in:
Manuel Pégourié-Gonnard 2018-04-18 12:21:36 +02:00
parent 4a9236efce affb4f8e90
commit 8bce3685f5
2 changed files with 51 additions and 10 deletions
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9
ChangeLog
View file

@ -9,6 +9,12 @@ Security
a non DER-compliant certificate correctly signed by a trusted CA, or a
trusted CA with a non DER-compliant certificate. Found by luocm on GitHub.
Fixes #825.
* Fix buffer length assertion in the ssl_parse_certificate_request()
function which leads to an arbitrary overread of the message buffer. The
overreads could occur upon receiving a message malformed at the point
where an optional signature algorithms list is expected in the cases of
the signature algorithms section being too short. In the debug builds
the overread data is printed to the standard output.
Bugfix
* Fix spurious uninitialized variable warning in cmac.c. Fix independently
@ -30,6 +36,9 @@ Bugfix
the mbedtls_cipher_update() documentation. Contributed by Andy Leiserson.
* Fix overriding and ignoring return values when parsing and writing to
a file in pk_sign program. Found by kevlut in #1142.
* Fix buffer length assertions in the ssl_parse_certificate_request()
function which leads to a potential one byte overread of the message
buffer.
Changes
* Support cmake build where Mbed TLS is a subproject. Fix

52
library/ssl_cli.c
View file

@ -2672,10 +2672,27 @@ static int ssl_parse_certificate_request( mbedtls_ssl_context *ssl )
buf = ssl->in_msg;
/* certificate_types */
if( ssl->in_hslen <= mbedtls_ssl_hs_hdr_len( ssl ) )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad certificate request message" ) );
mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR );
return( MBEDTLS_ERR_SSL_BAD_HS_CERTIFICATE_REQUEST );
}
cert_type_len = buf[mbedtls_ssl_hs_hdr_len( ssl )];
n = cert_type_len;
if( ssl->in_hslen < mbedtls_ssl_hs_hdr_len( ssl ) + 2 + n )
/*
* In the subsequent code there are two paths that read from buf:
* * the length of the signature algorithms field (if minor version of
* SSL is 3),
* * distinguished name length otherwise.
* Both reach at most the index:
* ...hdr_len + 2 + n,
* therefore the buffer length at this point must be greater than that
* regardless of the actual code path.
*/
if( ssl->in_hslen <= mbedtls_ssl_hs_hdr_len( ssl ) + 2 + n )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad certificate request message" ) );
mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
@ -2690,9 +2707,32 @@ static int ssl_parse_certificate_request( mbedtls_ssl_context *ssl )
size_t sig_alg_len = ( ( buf[mbedtls_ssl_hs_hdr_len( ssl ) + 1 + n] << 8 )
| ( buf[mbedtls_ssl_hs_hdr_len( ssl ) + 2 + n] ) );
#if defined(MBEDTLS_DEBUG_C)
unsigned char* sig_alg = buf + mbedtls_ssl_hs_hdr_len( ssl ) + 3 + n;
unsigned char* sig_alg;
size_t i;
#endif
/*
* The furthest access in buf is in the loop few lines below:
* sig_alg[i + 1],
* where:
* sig_alg = buf + ...hdr_len + 3 + n,
* max(i) = sig_alg_len - 1.
* Therefore the furthest access is:
* buf[...hdr_len + 3 + n + sig_alg_len - 1 + 1],
* which reduces to:
* buf[...hdr_len + 3 + n + sig_alg_len],
* which is one less than we need the buf to be.
*/
if( ssl->in_hslen <= mbedtls_ssl_hs_hdr_len( ssl ) + 3 + n + sig_alg_len )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad certificate request message" ) );
mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR );
return( MBEDTLS_ERR_SSL_BAD_HS_CERTIFICATE_REQUEST );
}
#if defined(MBEDTLS_DEBUG_C)
sig_alg = buf + mbedtls_ssl_hs_hdr_len( ssl ) + 3 + n;
for( i = 0; i < sig_alg_len; i += 2 )
{
MBEDTLS_SSL_DEBUG_MSG( 3, ( "Supported Signature Algorithm found: %d"
@ -2701,14 +2741,6 @@ static int ssl_parse_certificate_request( mbedtls_ssl_context *ssl )
#endif
n += 2 + sig_alg_len;
if( ssl->in_hslen < mbedtls_ssl_hs_hdr_len( ssl ) + 2 + n )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad certificate request message" ) );
mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR );
return( MBEDTLS_ERR_SSL_BAD_HS_CERTIFICATE_REQUEST );
}
}
#endif /* MBEDTLS_SSL_PROTO_TLS1_2 */