Send TLS alerts in many more cases
The TLS client and server code was usually closing the connection in
case of a fatal error without sending an alert. This commit adds
alerts in many cases.
Added one test case to detect that we send the alert, where a server
complains that the client's certificate is from an unknown CA (case
tracked internally as IOTSSL-1330).
diff --git a/library/ssl_srv.c b/library/ssl_srv.c
index c9051a4..451370c 100644
--- a/library/ssl_srv.c
+++ b/library/ssl_srv.c
@@ -101,6 +101,8 @@
if( servername_list_size + 2 != len )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
+ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR );
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
}
@@ -111,6 +113,8 @@
if( hostname_len + 3 > servername_list_size )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
+ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR );
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
}
@@ -135,6 +139,8 @@
if( servername_list_size != 0 )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
+ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER );
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
}
@@ -201,6 +207,8 @@
sig_alg_list_size % 2 != 0 )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
+ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR );
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
}
@@ -247,6 +255,8 @@
list_size % 2 != 0 )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
+ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR );
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
}
@@ -254,6 +264,8 @@
if( ssl->handshake->curves != NULL )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
+ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR );
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
}
@@ -264,7 +276,11 @@
our_size = MBEDTLS_ECP_DP_MAX;
if( ( curves = mbedtls_calloc( our_size, sizeof( *curves ) ) ) == NULL )
+ {
+ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_INTERNAL_ERROR );
return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
+ }
ssl->handshake->curves = curves;
@@ -297,6 +313,8 @@
if( list_size + 1 != len )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
+ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR );
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
}
@@ -342,6 +360,8 @@
buf, len ) ) != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ecjpake_read_round_one", ret );
+ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER );
return( ret );
}
@@ -360,6 +380,8 @@
if( len != 1 || buf[0] >= MBEDTLS_SSL_MAX_FRAG_LEN_INVALID )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
+ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER );
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
}
@@ -377,6 +399,8 @@
if( len != 0 )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
+ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR );
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
}
@@ -397,6 +421,8 @@
if( len != 0 )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
+ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR );
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
}
@@ -420,6 +446,8 @@
if( len != 0 )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
+ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR );
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
}
@@ -531,11 +559,19 @@
/* Min length is 2 (list_len) + 1 (name_len) + 1 (name) */
if( len < 4 )
+ {
+ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR );
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
+ }
list_len = ( buf[0] << 8 ) | buf[1];
if( list_len != len - 2 )
+ {
+ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR );
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
+ }
/*
* Use our order of preference
@@ -549,13 +585,21 @@
{
/* If the list is well formed, we should get equality first */
if( theirs > end )
+ {
+ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER );
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
+ }
cur_len = *theirs++;
/* Empty strings MUST NOT be included */
if( cur_len == 0 )
+ {
+ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER );
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
+ }
if( cur_len == ours_len &&
memcmp( theirs, *ours, cur_len ) == 0 )
@@ -1064,6 +1108,9 @@
}
#endif /* MBEDTLS_SSL_SRV_SUPPORT_SSLV2_CLIENT_HELLO */
+/* This function doesn't alert on errors that happen early during
+ ClientHello parsing because they might indicate that the client is
+ not talking SSL/TLS at all and would not understand our alert. */
static int ssl_parse_client_hello( mbedtls_ssl_context *ssl )
{
int ret, got_common_suite;
@@ -1098,6 +1145,7 @@
{
if( ( ret = mbedtls_ssl_fetch_input( ssl, 5 ) ) != 0 )
{
+ /* No alert on a read error. */
MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_fetch_input", ret );
return( ret );
}
@@ -1349,10 +1397,8 @@
" [%d:%d] < [%d:%d]",
ssl->major_ver, ssl->minor_ver,
ssl->conf->min_major_ver, ssl->conf->min_minor_ver ) );
-
mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
MBEDTLS_SSL_ALERT_MSG_PROTOCOL_VERSION );
-
return( MBEDTLS_ERR_SSL_BAD_HS_PROTOCOL_VERSION );
}
@@ -1380,6 +1426,8 @@
sess_len + 34 + 2 > msg_len ) /* 2 for cipherlist length field */
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
+ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR );
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
}
@@ -1403,6 +1451,8 @@
if( cookie_offset + 1 + cookie_len + 2 > msg_len )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
+ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_PROTOCOL_VERSION );
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
}
@@ -1435,6 +1485,7 @@
/* We know we didn't send a cookie, so it should be empty */
if( cookie_len != 0 )
{
+ /* This may be an attacker's probe, so don't send an alert */
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
}
@@ -1459,6 +1510,8 @@
( ciph_len % 2 ) != 0 )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
+ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR );
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
}
@@ -1477,6 +1530,8 @@
comp_len + comp_offset + 1 > msg_len )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
+ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR );
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
}
@@ -1515,6 +1570,8 @@
if( msg_len < ext_offset + 2 )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
+ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR );
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
}
@@ -1525,6 +1582,8 @@
msg_len != ext_offset + 2 + ext_len )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
+ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR );
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
}
}
@@ -1544,6 +1603,8 @@
if( ext_size + 4 > ext_len )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
+ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR );
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
}
switch( ext_id )
@@ -1689,6 +1750,8 @@
if( ext_len > 0 && ext_len < 4 )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
+ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR );
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
}
}
