From d20a8ca7338e8054db6189c15efca20b8afb2fdb Mon Sep 17 00:00:00 2001
From: Hanno Becker <hanno.becker@arm.com>
Date: Mon, 22 Oct 2018 15:31:26 +0100
Subject: [PATCH] Implement API for configuration of opaque PSKs

This commit adds implementations of the two new API functions

mbedtls_ssl_conf_psk_opaque()
mbedtls_ssl_set_hs_psk_opaque().
---
 library/ssl_tls.c | 116 +++++++++++++++++++++++++++++++++++++---------
 1 file changed, 95 insertions(+), 21 deletions(-)

diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 82e65251f..2150c03d1 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -7326,6 +7326,37 @@ int mbedtls_ssl_set_hs_ecjpake_password( mbedtls_ssl_context *ssl,
 #endif /* MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED */
 
 #if defined(MBEDTLS_KEY_EXCHANGE__SOME__PSK_ENABLED)
+
+static void ssl_conf_remove_psk( mbedtls_ssl_config *conf )
+{
+    /* Remove reference to existing PSK, if any. */
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
+    if( conf->psk_opaque != 0 )
+    {
+        /* The maintenance of the PSK key slot is the
+         * user's responsibility. */
+        conf->psk_opaque = 0;
+    }
+    else
+#endif /* MBEDTLS_USE_PSA_CRYPTO */
+    if( conf->psk != NULL )
+    {
+        mbedtls_platform_zeroize( conf->psk, conf->psk_len );
+
+        mbedtls_free( conf->psk );
+        conf->psk = NULL;
+        conf->psk_len = 0;
+    }
+
+    /* Remove reference to PSK identity, if any. */
+    if( conf->psk_identity != NULL )
+    {
+        mbedtls_free( conf->psk_identity );
+        conf->psk_identity = NULL;
+        conf->psk_identity_len = 0;
+    }
+}
+
 int mbedtls_ssl_conf_psk( mbedtls_ssl_config *conf,
                 const unsigned char *psk, size_t psk_len,
                 const unsigned char *psk_identity, size_t psk_identity_len )
@@ -7343,20 +7374,7 @@ int mbedtls_ssl_conf_psk( mbedtls_ssl_config *conf,
         return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
     }
 
-    if( conf->psk != NULL )
-    {
-        mbedtls_platform_zeroize( conf->psk, conf->psk_len );
-
-        mbedtls_free( conf->psk );
-        conf->psk = NULL;
-        conf->psk_len = 0;
-    }
-    if( conf->psk_identity != NULL )
-    {
-        mbedtls_free( conf->psk_identity );
-        conf->psk_identity = NULL;
-        conf->psk_identity_len = 0;
-    }
+    ssl_conf_remove_psk( conf );
 
     if( ( conf->psk = mbedtls_calloc( 1, psk_len ) ) == NULL ||
         ( conf->psk_identity = mbedtls_calloc( 1, psk_identity_len ) ) == NULL )
@@ -7377,6 +7395,24 @@ int mbedtls_ssl_conf_psk( mbedtls_ssl_config *conf,
     return( 0 );
 }
 
+static void ssl_remove_psk( mbedtls_ssl_context *ssl )
+{
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
+    if( ssl->handshake->psk_opaque != 0 )
+    {
+        ssl->handshake->psk_opaque = 0;
+    }
+    else
+#endif /* MBEDTLS_USE_PSA_CRYPTO */
+    if( ssl->handshake->psk != NULL )
+    {
+        mbedtls_platform_zeroize( ssl->handshake->psk,
+                                  ssl->handshake->psk_len );
+        mbedtls_free( ssl->handshake->psk );
+        ssl->handshake->psk_len = 0;
+    }
+}
+
 int mbedtls_ssl_set_hs_psk( mbedtls_ssl_context *ssl,
                             const unsigned char *psk, size_t psk_len )
 {
@@ -7386,13 +7422,7 @@ int mbedtls_ssl_set_hs_psk( mbedtls_ssl_context *ssl,
     if( psk_len > MBEDTLS_PSK_MAX_LEN )
         return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
 
-    if( ssl->handshake->psk != NULL )
-    {
-        mbedtls_platform_zeroize( ssl->handshake->psk,
-                                  ssl->handshake->psk_len );
-        mbedtls_free( ssl->handshake->psk );
-        ssl->handshake->psk_len = 0;
-    }
+    ssl_remove_psk( ssl );
 
     if( ( ssl->handshake->psk = mbedtls_calloc( 1, psk_len ) ) == NULL )
         return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
@@ -7403,6 +7433,50 @@ int mbedtls_ssl_set_hs_psk( mbedtls_ssl_context *ssl,
     return( 0 );
 }
 
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
+int mbedtls_ssl_conf_psk_opaque( mbedtls_ssl_config *conf,
+                                 psa_key_slot_t psk_slot,
+                                 const unsigned char *psk_identity,
+                                 size_t psk_identity_len )
+{
+    if( psk_slot == 0 || psk_identity == NULL )
+        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+
+    /* Identity len will be encoded on two bytes */
+    if( ( psk_identity_len >> 16 ) != 0 ||
+        psk_identity_len > MBEDTLS_SSL_OUT_CONTENT_LEN )
+    {
+        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+    }
+
+    ssl_conf_remove_psk( conf );
+
+    if( ( conf->psk_identity = mbedtls_calloc( 1, psk_identity_len ) ) == NULL )
+    {
+        mbedtls_free( conf->psk_identity );
+        conf->psk_identity = NULL;
+        return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
+    }
+
+    conf->psk_identity_len = psk_identity_len;
+    memcpy( conf->psk_identity, psk_identity, conf->psk_identity_len );
+
+    conf->psk_opaque = psk_slot;
+    return( 0 );
+}
+
+int mbedtls_ssl_set_hs_psk_opaque( mbedtls_ssl_context *ssl,
+                                   psa_key_slot_t psk_slot )
+{
+    if( psk_slot == 0 || ssl->handshake == NULL )
+        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+
+    ssl_remove_psk( ssl );
+    ssl->handshake->psk_opaque = psk_slot;
+    return( 0 );
+}
+#endif /* MBEDTLS_USE_PSA_CRYPTO */
+
 void mbedtls_ssl_conf_psk_cb( mbedtls_ssl_config *conf,
                      int (*f_psk)(void *, mbedtls_ssl_context *, const unsigned char *,
                      size_t),