add offered psks parser
Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/library/ssl_tls13_server.c b/library/ssl_tls13_server.c
index 02a2850..104d5b6 100644
--- a/library/ssl_tls13_server.c
+++ b/library/ssl_tls13_server.c
@@ -24,6 +24,7 @@
#include "mbedtls/debug.h"
#include "mbedtls/error.h"
#include "mbedtls/platform.h"
+#include "mbedtls/constant_time.h"
#include "ssl_misc.h"
#include "ssl_tls13_keys.h"
@@ -97,6 +98,269 @@
ssl->handshake->tls13_kex_modes = ke_modes;
return( 0 );
}
+
+#define SSL_TLS1_3_OFFERED_PSK_NOT_MATCH 0
+#define SSL_TLS1_3_OFFERED_PSK_MATCH 1
+static int ssl_tls13_offered_psks_check_identity_match(
+ mbedtls_ssl_context *ssl,
+ const unsigned char *identity,
+ uint16_t identity_len )
+{
+ /* Check identity with external configured function */
+ if( ssl->conf->f_psk != NULL )
+ {
+ if( ssl->conf->f_psk(
+ ssl->conf->p_psk, ssl, identity, identity_len ) == 0 )
+ {
+ return( SSL_TLS1_3_OFFERED_PSK_MATCH );
+ }
+ return( SSL_TLS1_3_OFFERED_PSK_NOT_MATCH );
+ }
+
+ /* Check identity with pre-configured psk */
+ if( identity_len == ssl->conf->psk_identity_len &&
+ mbedtls_ct_memcmp( ssl->conf->psk_identity,
+ identity, identity_len ) == 0 )
+ {
+ mbedtls_ssl_set_hs_psk( ssl, ssl->conf->psk, ssl->conf->psk_len );
+ return( SSL_TLS1_3_OFFERED_PSK_MATCH );
+ }
+
+ /* Add session ticket here */
+
+ return( SSL_TLS1_3_OFFERED_PSK_NOT_MATCH );
+}
+
+static int ssl_tls13_offered_psks_check_binder_match(
+ mbedtls_ssl_context *ssl,
+ const unsigned char *binder,
+ uint16_t binder_len,
+ const unsigned char *psk,
+ size_t psk_len )
+{
+ int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+ int psk_type;
+ mbedtls_md_type_t md_alg =
+ binder_len == 32 ? MBEDTLS_MD_SHA256 : MBEDTLS_MD_SHA384 ;
+ psa_algorithm_t psa_md_alg = mbedtls_psa_translate_md( md_alg );
+ unsigned char transcript[MBEDTLS_MD_MAX_SIZE];
+ size_t transcript_len;
+ unsigned char server_computed_binder[MBEDTLS_MD_MAX_SIZE];
+
+ if( ssl->handshake->resume == 1 )
+ psk_type = MBEDTLS_SSL_TLS1_3_PSK_RESUMPTION;
+ else
+ psk_type = MBEDTLS_SSL_TLS1_3_PSK_EXTERNAL;
+
+ /* Get current state of handshake transcript. */
+ ret = mbedtls_ssl_get_handshake_transcript( ssl, md_alg,
+ transcript, sizeof( transcript ),
+ &transcript_len );
+ if( ret != 0 )
+ return( ret );
+
+ ret = mbedtls_ssl_tls13_create_psk_binder( ssl, psa_md_alg,
+ psk, psk_len, psk_type,
+ transcript,
+ server_computed_binder );
+ /* We do not check for multiple binders */
+ if( ret != 0 )
+ {
+ MBEDTLS_SSL_DEBUG_MSG( 1, ( "PSK binder calculation failed." ) );
+ return( MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE );
+ }
+
+ MBEDTLS_SSL_DEBUG_BUF( 3, "psk binder ( computed ): ",
+ server_computed_binder, binder_len );
+ MBEDTLS_SSL_DEBUG_BUF( 3, "psk binder ( received ): ", binder, binder_len );
+
+ if( mbedtls_ct_memcmp( server_computed_binder, binder, binder_len ) == 0 )
+ {
+ return( SSL_TLS1_3_OFFERED_PSK_MATCH );
+ }
+
+ return( SSL_TLS1_3_OFFERED_PSK_NOT_MATCH );
+}
+/* Parser for pre_shared_key extension in client hello
+ * struct {
+ * opaque identity<1..2^16-1>;
+ * uint32 obfuscated_ticket_age;
+ * } PskIdentity;
+ *
+ * opaque PskBinderEntry<32..255>;
+ *
+ * struct {
+ * PskIdentity identities<7..2^16-1>;
+ * PskBinderEntry binders<33..2^16-1>;
+ * } OfferedPsks;
+ *
+ * struct {
+ * select (Handshake.msg_type) {
+ * case client_hello: OfferedPsks;
+ * ....
+ * };
+ * } PreSharedKeyExtension;
+ */
+static int ssl_tls13_parse_offered_psks_ext( mbedtls_ssl_context *ssl,
+ const unsigned char *buf,
+ const unsigned char *end )
+{
+ int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+ const unsigned char *p = buf;
+ uint16_t identities_len;
+ const unsigned char *identities_end;
+ uint32_t identity_matched = SSL_TLS1_3_OFFERED_PSK_NOT_MATCH;
+ uint16_t binders_len;
+ const unsigned char *binders_end;
+ unsigned char *psk = NULL;
+ size_t psk_len = 0;
+ int binder_matched = 0;
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
+ psa_key_attributes_t key_attributes = PSA_KEY_ATTRIBUTES_INIT;
+ psa_status_t status;
+#endif /* MBEDTLS_USE_PSA_CRYPTO */
+
+ MBEDTLS_SSL_DEBUG_BUF( 3, "pre_shared_key extesion", buf, end - buf );
+
+ /* identities >= 7 bytes */
+ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 7 );
+
+ identities_len = MBEDTLS_GET_UINT16_BE( p, 0 );
+ p += 2;
+ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, identities_len );
+ identities_end = p + identities_len;
+
+ while( p < identities_end )
+ {
+ uint16_t identity_len;
+ const unsigned char *identity;
+ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, identities_end, 2 );
+ identity_len = MBEDTLS_GET_UINT16_BE( p, 0 );
+ p += 2;
+ identity = p;
+ p += identity_len;
+ p += 4; // skip obfuscated_ticket_age
+ MBEDTLS_SSL_CHK_BUF_READ_PTR( identity, identities_end, identity_len );
+
+ if( identity_matched == SSL_TLS1_3_OFFERED_PSK_MATCH )
+ continue;
+
+ MBEDTLS_SSL_DEBUG_BUF( 3, "received psk identity",
+ identity, identity_len );
+ identity_matched = ssl_tls13_offered_psks_check_identity_match(
+ ssl, identity, identity_len );
+ }
+
+ if( identity_matched != SSL_TLS1_3_OFFERED_PSK_MATCH )
+ {
+ MBEDTLS_SSL_PEND_FATAL_ALERT(
+ MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_UNKNOWN_PSK_IDENTITY );
+ return( MBEDTLS_ERR_SSL_UNKNOWN_IDENTITY );
+ }
+
+ if( p != identities_end )
+ {
+ MBEDTLS_SSL_DEBUG_MSG( 3, ( "pre_shared_key extesion decode error" ) );
+ MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR,
+ MBEDTLS_ERR_SSL_DECODE_ERROR );
+ return( MBEDTLS_ERR_SSL_DECODE_ERROR );
+ }
+
+ ssl->handshake->update_checksum( ssl, buf, p - buf );
+
+ /* binders >= 33 bytes */
+ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 33 );
+ binders_len = MBEDTLS_GET_UINT16_BE( p, 0 );
+ p += 2;
+ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, binders_len );
+ binders_end = p + binders_len;
+
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
+ status = psa_get_key_attributes( ssl->handshake->psk_opaque,
+ &key_attributes );
+ if( status != PSA_SUCCESS)
+ {
+ return( psa_ssl_status_to_mbedtls( status ) );
+ }
+
+ psk_len = PSA_BITS_TO_BYTES(psa_get_key_bits( &key_attributes ) );
+ psk = mbedtls_calloc( 1, psk_len );
+ if( psk == NULL )
+ {
+ return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
+ }
+ status = psa_export_key(ssl->handshake->psk_opaque, psk, psk_len, &psk_len );
+ if( status != PSA_SUCCESS)
+ {
+ ret = psa_ssl_status_to_mbedtls( status );
+ goto exit_failue;
+ }
+#else
+ psk = ssl->handshake->psk;
+ psk_len = ssl->handshake->psk_len;
+#endif /* !MBEDTLS_USE_PSA_CRYPTO */
+
+ while( p < binders_end )
+ {
+ uint8_t binder_len;
+ const unsigned char *binder;
+
+ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 1 );
+ binder_len = *p++;
+ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, binder_len );
+ binder = p;
+ p += binder_len;
+
+ if( binder_matched == SSL_TLS1_3_OFFERED_PSK_MATCH)
+ continue;
+
+ binder_matched = ssl_tls13_offered_psks_check_binder_match(
+ ssl, binder, binder_len, psk, psk_len );
+ if( binder_matched < 0 )
+ {
+ MBEDTLS_SSL_DEBUG_RET( 1,
+ "ssl_tls13_offered_psks_check_binder_match" , binder_matched );
+ MBEDTLS_SSL_PEND_FATAL_ALERT(
+ MBEDTLS_SSL_ALERT_MSG_HANDSHAKE_FAILURE,
+ MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE );
+ ret = binder_matched;
+ goto exit_failue;
+ }
+ }
+
+ if( binder_matched != SSL_TLS1_3_OFFERED_PSK_MATCH )
+ {
+ MBEDTLS_SSL_DEBUG_MSG( 1,
+ ( "Received psk binder does not match computed psk binder." ) );
+ MBEDTLS_SSL_PEND_FATAL_ALERT(
+ MBEDTLS_SSL_ALERT_MSG_HANDSHAKE_FAILURE,
+ MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE );
+ ret = MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE;
+ goto exit_failue;
+ }
+
+ if( p != binders_end )
+ {
+ MBEDTLS_SSL_DEBUG_MSG( 3, ( "pre_shared_key extesion decode error" ) );
+ MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR,
+ MBEDTLS_ERR_SSL_DECODE_ERROR );
+ ret = MBEDTLS_ERR_SSL_DECODE_ERROR;
+ goto exit_failue;
+ }
+
+ /* Update the handshake transcript with the binder list. */
+ ssl->handshake->update_checksum( ssl,
+ identities_end,
+ (size_t)( p - identities_end ) );
+ ret = 0;
+
+exit_failue:
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
+ mbedtls_free( (void *)psk );
+#endif
+ return( ret );
+}
#endif /* MBEDTLS_KEY_EXCHANGE_SOME_PSK_ENABLED */
/* From RFC 8446:
@@ -540,6 +804,10 @@
int hrr_required = 0;
const mbedtls_ssl_ciphersuite_t* ciphersuite_info;
+#if defined(MBEDTLS_KEY_EXCHANGE_SOME_PSK_ENABLED)
+ const unsigned char *pre_shared_key_ext_start = NULL;
+ const unsigned char *pre_shared_key_ext_end = NULL;
+#endif /* MBEDTLS_KEY_EXCHANGE_SOME_PSK_ENABLED */
ssl->handshake->extensions_present = MBEDTLS_SSL_EXT_NONE;
@@ -825,6 +1093,20 @@
break;
#endif /* MBEDTLS_KEY_EXCHANGE_SOME_PSK_ENABLED */
+#if defined(MBEDTLS_KEY_EXCHANGE_SOME_PSK_ENABLED)
+ case MBEDTLS_TLS_EXT_PRE_SHARED_KEY:
+ MBEDTLS_SSL_DEBUG_MSG( 3, ( "found pre_shared_key extension" ) );
+ /* Delay processing of the PSK identity once we have
+ * found out which algorithms to use. We keep a pointer
+ * to the buffer and the size for later processing.
+ */
+ pre_shared_key_ext_start = p;
+ pre_shared_key_ext_end = extension_data_end;
+
+ ssl->handshake->extensions_present |= MBEDTLS_SSL_EXT_PRE_SHARED_KEY;
+ break;
+#endif /* MBEDTLS_KEY_EXCHANGE_SOME_PSK_ENABLED */
+
#if defined(MBEDTLS_SSL_ALPN)
case MBEDTLS_TLS_EXT_ALPN:
MBEDTLS_SSL_DEBUG_MSG( 3, ( "found alpn extension" ) );
@@ -866,17 +1148,48 @@
p += extension_data_len;
}
+
+#if defined(MBEDTLS_DEBUG_C)
+ /* List all the extensions we have received */
+ ssl_tls13_debug_print_client_hello_exts( ssl );
+#endif /* MBEDTLS_DEBUG_C */
+
+ mbedtls_ssl_add_hs_hdr_to_checksum( ssl,
+ MBEDTLS_SSL_HS_CLIENT_HELLO,
+ p - buf );
+#if defined(MBEDTLS_KEY_EXCHANGE_SOME_PSK_ENABLED)
/* Update checksum with either
* - The entire content of the CH message, if no PSK extension is present
* - The content up to but excluding the PSK extension, if present.
*/
- mbedtls_ssl_add_hs_msg_to_checksum( ssl, MBEDTLS_SSL_HS_CLIENT_HELLO,
- buf, p - buf );
-
- /* List all the extensions we have received */
-#if defined(MBEDTLS_DEBUG_C)
- ssl_tls13_debug_print_client_hello_exts( ssl );
-#endif /* MBEDTLS_DEBUG_C */
+ /* If we've settled on a PSK-based exchange, parse PSK identity ext */
+ if( mbedtls_ssl_conf_tls13_some_psk_enabled( ssl ) &&
+ ( ssl->handshake->extensions_present & MBEDTLS_SSL_EXT_PRE_SHARED_KEY ) )
+ {
+ ssl->handshake->update_checksum( ssl, buf,
+ pre_shared_key_ext_start - buf );
+ ret = ssl_tls13_parse_offered_psks_ext( ssl,
+ pre_shared_key_ext_start,
+ pre_shared_key_ext_end );
+ if( ret != 0 )
+ {
+ MBEDTLS_SSL_DEBUG_RET( 1, ( "ssl_tls13_parse_offered_psks_ext" ),
+ ret );
+ return( ret );
+ }
+ /* If pre_shared_key is not last extension */
+ if( p - pre_shared_key_ext_end )
+ {
+ ssl->handshake->update_checksum( ssl,
+ pre_shared_key_ext_end,
+ p - pre_shared_key_ext_end );
+ }
+ }
+ else
+#endif /* MBEDTLS_KEY_EXCHANGE_SOME_PSK_ENABLED */
+ {
+ ssl->handshake->update_checksum( ssl, buf, p - buf );
+ }
return( hrr_required ? SSL_CLIENT_HELLO_HRR_REQUIRED : SSL_CLIENT_HELLO_OK );
}