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Fix heap-buffer overread in ALPN ext parsing

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Manuel Pégourié-Gonnard 2018-01-09 10:43:43 +01:00
parent 47331a72e2
commit 022954f4bd
2 changed files with 20 additions and 9 deletions
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3
ChangeLog
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@ -38,6 +38,9 @@ Security
corrupt 6 bytes on the peer's heap, potentially leading to crash or corrupt 6 bytes on the peer's heap, potentially leading to crash or
remote code execution. This can be triggered remotely from either remote code execution. This can be triggered remotely from either
side in both TLS and DTLS. side in both TLS and DTLS.
* Fix a potential heap buffer overread in ALPN extension parsing
(server-side). Could result in application crash, but only if an ALPN
name larger than 16 bytes had been configured on the server.
Features Features
* Allow comments in test data files. * Allow comments in test data files.

26
library/ssl_srv.c
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@ -539,25 +539,33 @@ static int ssl_parse_alpn_ext( mbedtls_ssl_context *ssl,
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO ); return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
/* /*
* Use our order of preference * Validate peer's list (lengths)
*/ */
start = buf + 2; start = buf + 2;
end = buf + len; end = buf + len;
for( theirs = start; theirs != end; theirs += cur_len )
{
cur_len = *theirs++;
/* Current identifier must fit in list */
if( cur_len > (size_t)( end - theirs ) )
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
/* Empty strings MUST NOT be included */
if( cur_len == 0 )
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
}
/*
* Use our order of preference
*/
for( ours = ssl->conf->alpn_list; *ours != NULL; ours++ ) for( ours = ssl->conf->alpn_list; *ours != NULL; ours++ )
{ {
ours_len = strlen( *ours ); ours_len = strlen( *ours );
for( theirs = start; theirs != end; theirs += cur_len ) for( theirs = start; theirs != end; theirs += cur_len )
{ {
/* If the list is well formed, we should get equality first */
if( theirs > end )
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
cur_len = *theirs++; cur_len = *theirs++;
/* Empty strings MUST NOT be included */
if( cur_len == 0 )
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
if( cur_len == ours_len && if( cur_len == ours_len &&
memcmp( theirs, *ours, cur_len ) == 0 ) memcmp( theirs, *ours, cur_len ) == 0 )
{ {