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Backport 2.7: Fix unsafe bounds check in ssl_load_session() #2132

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merged 4 commits into from
Dec 7, 2018
Merged

Backport 2.7: Fix unsafe bounds check in ssl_load_session() #2132

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e67f7a7
Use brackets around shift operations
Oct 24, 2018
fa95a6a
Fix unsafe bounds checks in ssl_load_session()
Oct 24, 2018
52adf34
Indentation fix
Oct 24, 2018
7cf2857
Adapt ChangeLog
Oct 24, 2018
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3 changes: 3 additions & 0 deletions ChangeLog
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,9 @@ Bugfix
MBEDTLS_THREADING_C is defined. Found by TrinityTonic, #1095
* Fix a bug in the update function for SSL ticket keys which previously
invalidated keys of a lifetime of less than a 1s. Fixes #1968.
* Fix an unsafe bounds check when restoring an SSL session from a ticket.
This could lead to a buffer overflow, but only in case ticket authentication
was broken. Reported and fix suggested by Guido Vranken in #659.

Changes
* Add tests for session resumption in DTLS.
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14 changes: 7 additions & 7 deletions library/ssl_ticket.c
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Original file line number Diff line number Diff line change
Expand Up @@ -192,9 +192,9 @@ static int ssl_save_session( const mbedtls_ssl_session *session,
if( left < 3 + cert_len )
return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );

*p++ = (unsigned char)( cert_len >> 16 & 0xFF );
*p++ = (unsigned char)( cert_len >> 8 & 0xFF );
*p++ = (unsigned char)( cert_len & 0xFF );
*p++ = (unsigned char)( ( cert_len >> 16 ) & 0xFF );
*p++ = (unsigned char)( ( cert_len >> 8 ) & 0xFF );
*p++ = (unsigned char)( ( cert_len ) & 0xFF );

if( session->peer_cert != NULL )
memcpy( p, session->peer_cert->raw.p, cert_len );
Expand All @@ -219,14 +219,14 @@ static int ssl_load_session( mbedtls_ssl_session *session,
size_t cert_len;
#endif /* MBEDTLS_X509_CRT_PARSE_C */

if( p + sizeof( mbedtls_ssl_session ) > end )
if( sizeof( mbedtls_ssl_session ) > (size_t)( end - p ) )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );

memcpy( session, p, sizeof( mbedtls_ssl_session ) );
p += sizeof( mbedtls_ssl_session );

#if defined(MBEDTLS_X509_CRT_PARSE_C)
if( p + 3 > end )
if( 3 > (size_t)( end - p ) )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );

cert_len = ( p[0] << 16 ) | ( p[1] << 8 ) | p[2];
Expand All @@ -240,7 +240,7 @@ static int ssl_load_session( mbedtls_ssl_session *session,
{
int ret;

if( p + cert_len > end )
if( cert_len > (size_t)( end - p ) )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );

session->peer_cert = mbedtls_calloc( 1, sizeof( mbedtls_x509_crt ) );
Expand All @@ -251,7 +251,7 @@ static int ssl_load_session( mbedtls_ssl_session *session,
mbedtls_x509_crt_init( session->peer_cert );

if( ( ret = mbedtls_x509_crt_parse_der( session->peer_cert,
p, cert_len ) ) != 0 )
p, cert_len ) ) != 0 )
{
mbedtls_x509_crt_free( session->peer_cert );
mbedtls_free( session->peer_cert );
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