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Merge remote-tracking branch 'upstream-restricted/pr/461' into development-restricted-proposed

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This commit is contained in:
Gilles Peskine 2018-04-19 17:41:39 +02:00
commit f2b76cd45c
2 changed files with 51 additions and 10 deletions
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9
ChangeLog
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@ -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.
Features
* Add option MBEDTLS_AES_FEWER_TABLES to dynamically compute 3/4 of the AES tables
@ -55,6 +61,9 @@ Bugfix
in the internal buffers; these cases lead to deadlocks in case
event-driven I/O was used.
Found and reported by Hubert Mis in #772.
* Fix buffer length assertions in the ssl_parse_certificate_request()
function which leads to a potential one byte overread of the message
buffer.
Changes
* Remove some redundant code in bignum.c. Contributed by Alexey Skalozub.

52
library/ssl_cli.c
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@ -2673,10 +2673,27 @@ 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,
@ -2691,9 +2708,32 @@ 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"
@ -2702,14 +2742,6 @@ 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 */