Merge remote-tracking branch 'upstream-restricted/pr/461' into development-restricted-proposed
diff --git a/ChangeLog b/ChangeLog
index ae8d86f..3e5dd68 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -9,6 +9,12 @@
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 @@
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.
diff --git a/library/ssl_cli.c b/library/ssl_cli.c
index 738014e..7cde5b1 100644
--- a/library/ssl_cli.c
+++ b/library/ssl_cli.c
@@ -2673,10 +2673,27 @@
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 @@
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 @@
#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 */