tls13: Share write ecdh_key_exchange function

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/library/ssl_misc.h b/library/ssl_misc.h
index 46d85d9..fa336e4 100644
--- a/library/ssl_misc.h
+++ b/library/ssl_misc.h
@@ -1781,6 +1781,16 @@
 
 int mbedtls_ssl_reset_transcript_for_hrr( mbedtls_ssl_context *ssl );
 
+#if defined(MBEDTLS_ECDH_C)
+int mbedtls_ssl_tls13_generate_and_write_ecdh_key_exchange(
+                mbedtls_ssl_context *ssl,
+                uint16_t named_group,
+                unsigned char *buf,
+                unsigned char *end,
+                size_t *out_len );
+#endif /* MBEDTLS_ECDH_C */
+
+
 #endif /* MBEDTLS_SSL_PROTO_TLS1_3 */
 
 #if defined(MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED)
diff --git a/library/ssl_tls13_client.c b/library/ssl_tls13_client.c
index cf5b382..d024abf 100644
--- a/library/ssl_tls13_client.c
+++ b/library/ssl_tls13_client.c
@@ -204,65 +204,6 @@
 /*
  * Functions for writing key_share extension.
  */
-#if defined(MBEDTLS_ECDH_C)
-static int ssl_tls13_generate_and_write_ecdh_key_exchange(
-                mbedtls_ssl_context *ssl,
-                uint16_t named_group,
-                unsigned char *buf,
-                unsigned char *end,
-                size_t *out_len )
-{
-    psa_status_t status = PSA_ERROR_GENERIC_ERROR;
-    int ret = MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE;
-    psa_key_attributes_t key_attributes;
-    size_t own_pubkey_len;
-    mbedtls_ssl_handshake_params *handshake = ssl->handshake;
-    size_t ecdh_bits = 0;
-
-    MBEDTLS_SSL_DEBUG_MSG( 1, ( "Perform PSA-based ECDH computation." ) );
-
-    /* Convert EC group to PSA key type. */
-    if( ( handshake->ecdh_psa_type =
-        mbedtls_psa_parse_tls_ecc_group( named_group, &ecdh_bits ) ) == 0 )
-            return( MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE );
-
-    ssl->handshake->ecdh_bits = ecdh_bits;
-
-    key_attributes = psa_key_attributes_init();
-    psa_set_key_usage_flags( &key_attributes, PSA_KEY_USAGE_DERIVE );
-    psa_set_key_algorithm( &key_attributes, PSA_ALG_ECDH );
-    psa_set_key_type( &key_attributes, handshake->ecdh_psa_type );
-    psa_set_key_bits( &key_attributes, handshake->ecdh_bits );
-
-    /* Generate ECDH private key. */
-    status = psa_generate_key( &key_attributes,
-                                &handshake->ecdh_psa_privkey );
-    if( status != PSA_SUCCESS )
-    {
-        ret = psa_ssl_status_to_mbedtls( status );
-        MBEDTLS_SSL_DEBUG_RET( 1, "psa_generate_key", ret );
-        return( ret );
-
-    }
-
-    /* Export the public part of the ECDH private key from PSA. */
-    status = psa_export_public_key( handshake->ecdh_psa_privkey,
-                                    buf, (size_t)( end - buf ),
-                                    &own_pubkey_len );
-    if( status != PSA_SUCCESS )
-    {
-        ret = psa_ssl_status_to_mbedtls( status );
-        MBEDTLS_SSL_DEBUG_RET( 1, "psa_export_public_key", ret );
-        return( ret );
-
-    }
-
-    *out_len = own_pubkey_len;
-
-    return( 0 );
-}
-#endif /* MBEDTLS_ECDH_C */
-
 static int ssl_tls13_get_default_group_id( mbedtls_ssl_context *ssl,
                                            uint16_t *group_id )
 {
@@ -367,8 +308,8 @@
          */
         MBEDTLS_SSL_CHK_BUF_PTR( p, end, 4 );
         p += 4;
-        ret = ssl_tls13_generate_and_write_ecdh_key_exchange( ssl, group_id, p, end,
-                                                              &key_exchange_len );
+        ret = mbedtls_ssl_tls13_generate_and_write_ecdh_key_exchange(
+                                    ssl, group_id, p, end, &key_exchange_len );
         p += key_exchange_len;
         if( ret != 0 )
             return( ret );
diff --git a/library/ssl_tls13_generic.c b/library/ssl_tls13_generic.c
index 4bee319..f5d791f 100644
--- a/library/ssl_tls13_generic.c
+++ b/library/ssl_tls13_generic.c
@@ -1535,6 +1535,63 @@
 
     return( 0 );
 }
+
+int mbedtls_ssl_tls13_generate_and_write_ecdh_key_exchange(
+                mbedtls_ssl_context *ssl,
+                uint16_t named_group,
+                unsigned char *buf,
+                unsigned char *end,
+                size_t *out_len )
+{
+    psa_status_t status = PSA_ERROR_GENERIC_ERROR;
+    int ret = MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE;
+    psa_key_attributes_t key_attributes;
+    size_t own_pubkey_len;
+    mbedtls_ssl_handshake_params *handshake = ssl->handshake;
+    size_t ecdh_bits = 0;
+
+    MBEDTLS_SSL_DEBUG_MSG( 1, ( "Perform PSA-based ECDH computation." ) );
+
+    /* Convert EC group to PSA key type. */
+    if( ( handshake->ecdh_psa_type =
+        mbedtls_psa_parse_tls_ecc_group( named_group, &ecdh_bits ) ) == 0 )
+            return( MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE );
+
+    ssl->handshake->ecdh_bits = ecdh_bits;
+
+    key_attributes = psa_key_attributes_init();
+    psa_set_key_usage_flags( &key_attributes, PSA_KEY_USAGE_DERIVE );
+    psa_set_key_algorithm( &key_attributes, PSA_ALG_ECDH );
+    psa_set_key_type( &key_attributes, handshake->ecdh_psa_type );
+    psa_set_key_bits( &key_attributes, handshake->ecdh_bits );
+
+    /* Generate ECDH private key. */
+    status = psa_generate_key( &key_attributes,
+                                &handshake->ecdh_psa_privkey );
+    if( status != PSA_SUCCESS )
+    {
+        ret = psa_ssl_status_to_mbedtls( status );
+        MBEDTLS_SSL_DEBUG_RET( 1, "psa_generate_key", ret );
+        return( ret );
+
+    }
+
+    /* Export the public part of the ECDH private key from PSA. */
+    status = psa_export_public_key( handshake->ecdh_psa_privkey,
+                                    buf, (size_t)( end - buf ),
+                                    &own_pubkey_len );
+    if( status != PSA_SUCCESS )
+    {
+        ret = psa_ssl_status_to_mbedtls( status );
+        MBEDTLS_SSL_DEBUG_RET( 1, "psa_export_public_key", ret );
+        return( ret );
+
+    }
+
+    *out_len = own_pubkey_len;
+
+    return( 0 );
+}
 #endif /* MBEDTLS_ECDH_C */
 
 #endif /* MBEDTLS_SSL_TLS_C && MBEDTLS_SSL_PROTO_TLS1_3 */
diff --git a/library/ssl_tls13_server.c b/library/ssl_tls13_server.c
index ae49eff..d6450a5 100644
--- a/library/ssl_tls13_server.c
+++ b/library/ssl_tls13_server.c
@@ -822,20 +822,27 @@
                                             size_t *out_len )
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
-
+    ((void) ssl);
+    ((void) named_group);
+    ((void) buf);
+    ((void) end);
+    ((void) out_len);
+#if defined(MBEDTLS_ECDH_C)
     if( mbedtls_ssl_tls13_named_group_is_ecdhe( named_group ) )
     {
-        ret = mbedtls_ecdh_tls13_make_params( &ssl->handshake->ecdh_ctx,
-                out_len, buf, end - buf, ssl->conf->f_rng, ssl->conf->p_rng );
+        ret = mbedtls_ssl_tls13_generate_and_write_ecdh_key_exchange(
+                                        ssl, named_group, buf, end, out_len );
         if( ret != 0 )
         {
-            MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ecdh_make_tls13_params", ret );
+            MBEDTLS_SSL_DEBUG_RET(
+                1, "mbedtls_ssl_tls13_generate_and_write_ecdh_key_exchange",
+                ret );
             return( ret );
         }
-
-        MBEDTLS_SSL_DEBUG_ECDH( 3, &ssl->handshake->ecdh_ctx, MBEDTLS_DEBUG_ECDH_Q );
     }
-    else if( 0 /* Other kinds of KEMs */ )
+    else
+#endif /* MBEDTLS_ECDH_C */
+    if( 0 /* Other kinds of KEMs */ )
     {
     }
     else