Enable support for psa opaque ECDHE-PSK key exchange on the client side

Signed-off-by: Przemek Stekiel <przemyslaw.stekiel@mobica.com>
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index df6a793..c60a856 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -5093,11 +5093,13 @@
     }
 #endif /* MBEDTLS_SSL_EXTENDED_MS_ENABLED */
 
-#if defined(MBEDTLS_USE_PSA_CRYPTO) &&             \
-    ( defined(MBEDTLS_KEY_EXCHANGE_PSK_ENABLED) || \
-      defined(MBEDTLS_KEY_EXCHANGE_RSA_PSK_ENABLED) )
+#if defined(MBEDTLS_USE_PSA_CRYPTO) &&                 \
+    ( defined(MBEDTLS_KEY_EXCHANGE_PSK_ENABLED) ||     \
+      defined(MBEDTLS_KEY_EXCHANGE_RSA_PSK_ENABLED) || \
+      defined(MBEDTLS_KEY_EXCHANGE_ECDHE_PSK_ENABLED) )
     if( ( handshake->ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_PSK ||
-          handshake->ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_RSA_PSK ) &&
+          handshake->ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_RSA_PSK ||
+          handshake->ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_ECDHE_PSK ) &&
         ssl_use_opaque_psk( ssl ) == 1 )
     {
         /* Perform PSK-to-MS expansion in a single step. */
@@ -5120,15 +5122,23 @@
         size_t other_secret_len = 0;
         unsigned char* other_secret = NULL;
 
-        if ( handshake->ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_RSA_PSK )
+        switch( handshake->ciphersuite_info->key_exchange )
         {
-            /* Provide other key as other secret.
-             * For RSA-PKS other key length is always 48 bytes.
+            /* Provide other secret.
              * Other secret is stored in premaster, where first 2 bytes hold the
-             * length of the other key. Skip them.
+             * length of the other key.
              */
-            other_secret_len = 48;
-            other_secret = handshake->premaster + 2;
+            case MBEDTLS_KEY_EXCHANGE_RSA_PSK:
+                /* For RSA-PKS other key length is always 48 bytes. */
+                other_secret_len = 48;
+                other_secret = handshake->premaster + 2;
+                break;
+            case MBEDTLS_KEY_EXCHANGE_ECDHE_PSK:
+                other_secret_len = MBEDTLS_GET_UINT16_BE(handshake->premaster, 0);
+                other_secret = handshake->premaster + 2;
+                break;
+            default:
+                break;
         }
 
         status = setup_psa_key_derivation( &derivation, psk, alg,
diff --git a/library/ssl_tls12_client.c b/library/ssl_tls12_client.c
index aaffcd3..2868a84 100644
--- a/library/ssl_tls12_client.c
+++ b/library/ssl_tls12_client.c
@@ -2959,10 +2959,6 @@
              * ciphersuites we offered, so this should never happen. */
             return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
 
-        /* Opaque PSKs are currently only supported for PSK-only suites. */
-        if( ssl_conf_has_static_raw_psk( ssl->conf ) == 0 )
-            return( MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE );
-
         /* uint16 to store content length */
         const size_t content_len_size = 2;
 
@@ -3068,30 +3064,40 @@
         MBEDTLS_PUT_UINT16_BE( zlen, pms, 0 );
         pms += zlen_size + zlen;
 
-        const unsigned char *psk = NULL;
-        size_t psk_len = 0;
+        /* In case of opaque psk skip writting psk to pms.
+         * Opaque key will be handled later. */
+        if( ssl_conf_has_static_raw_psk( ssl->conf ) == 1 )
+        {
+            const unsigned char *psk = NULL;
+            size_t psk_len = 0;
 
-        if( mbedtls_ssl_get_psk( ssl, &psk, &psk_len )
-                == MBEDTLS_ERR_SSL_PRIVATE_KEY_REQUIRED )
-            /*
-             * This should never happen because the existence of a PSK is always
-             * checked before calling this function
-             */
-            return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+            if( mbedtls_ssl_get_psk( ssl, &psk, &psk_len )
+                    == MBEDTLS_ERR_SSL_PRIVATE_KEY_REQUIRED )
+                /*
+                * This should never happen because the existence of a PSK is always
+                * checked before calling this function
+                */
+                return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
 
-        /* opaque psk<0..2^16-1>; */
-        if( (size_t)( pms_end - pms ) < ( 2 + psk_len ) )
-            return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+            /* opaque psk<0..2^16-1>; */
+            if( (size_t)( pms_end - pms ) < ( 2 + psk_len ) )
+                return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
 
-        /* Write the PSK length as uint16 */
-        MBEDTLS_PUT_UINT16_BE( psk_len, pms, 0 );
-        pms += 2;
+            /* Write the PSK length as uint16 */
+            MBEDTLS_PUT_UINT16_BE( psk_len, pms, 0 );
+            pms += 2;
 
-        /* Write the PSK itself */
-        memcpy( pms, psk, psk_len );
-        pms += psk_len;
+            /* Write the PSK itself */
+            memcpy( pms, psk, psk_len );
+            pms += psk_len;
 
-        ssl->handshake->pmslen = pms - ssl->handshake->premaster;
+            ssl->handshake->pmslen = pms - ssl->handshake->premaster;
+        }
+        else
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1,
+                ( "skip PMS generation for opaque ECDHE-PSK" ) );
+        }
     }
     else
 #endif /* MBEDTLS_USE_PSA_CRYPTO &&