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/*
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* Copyright (C) 2017-2018 Red Hat, Inc.
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*
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* Author: Nikos Mavrogiannopoulos
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*
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* This file is part of GnuTLS.
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*
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* The GnuTLS is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public License
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* as published by the Free Software Foundation; either version 2.1 of
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* the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>
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*
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*/
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#include "gnutls_int.h"
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#include "hello_ext.h"
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#include "errors.h"
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#include "extv.h"
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/* Iterates through all extensions found, and calls the cb()
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* function with their data */
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int _gnutls_extv_parse(void *ctx,
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gnutls_ext_raw_process_func cb,
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const uint8_t * data, int data_size)
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{
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int next, ret;
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int pos = 0;
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uint16_t tls_id;
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const uint8_t *sdata;
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uint16_t size;
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if (data_size == 0)
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return 0;
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DECR_LENGTH_RET(data_size, 2, GNUTLS_E_UNEXPECTED_EXTENSIONS_LENGTH);
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next = _gnutls_read_uint16(data);
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pos += 2;
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DECR_LENGTH_RET(data_size, next, GNUTLS_E_UNEXPECTED_EXTENSIONS_LENGTH);
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if (next == 0 && data_size == 0) /* field is present, but has zero length? Ignore it. */
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return 0;
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else if (data_size > 0) /* forbid unaccounted data */
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return gnutls_assert_val(GNUTLS_E_UNEXPECTED_EXTENSIONS_LENGTH);
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do {
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DECR_LENGTH_RET(next, 2, GNUTLS_E_UNEXPECTED_EXTENSIONS_LENGTH);
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tls_id = _gnutls_read_uint16(&data[pos]);
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pos += 2;
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DECR_LENGTH_RET(next, 2, GNUTLS_E_UNEXPECTED_EXTENSIONS_LENGTH);
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size = _gnutls_read_uint16(&data[pos]);
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pos += 2;
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DECR_LENGTH_RET(next, size, GNUTLS_E_UNEXPECTED_EXTENSIONS_LENGTH);
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sdata = &data[pos];
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pos += size;
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ret = cb(ctx, tls_id, sdata, size);
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if (ret < 0)
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return gnutls_assert_val(ret);
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}
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while (next > 2);
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/* forbid leftovers */
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if (next > 0)
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return gnutls_assert_val(GNUTLS_E_UNEXPECTED_EXTENSIONS_LENGTH);
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return 0;
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}
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#define HANDSHAKE_SESSION_ID_POS (34)
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/**
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* gnutls_ext_raw_parse:
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* @ctx: a pointer to pass to callback function
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* @cb: callback function to process each extension found
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* @data: TLS extension data
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* @flags: should be zero or %GNUTLS_EXT_RAW_FLAG_TLS_CLIENT_HELLO or %GNUTLS_EXT_RAW_FLAG_DTLS_CLIENT_HELLO
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*
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* This function iterates through the TLS extensions as passed in
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* @data, passing the individual extension data to callback. The
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* @data must conform to Extension extensions<0..2^16-1> format.
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*
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* If flags is %GNUTLS_EXT_RAW_TLS_FLAG_CLIENT_HELLO then this function
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* will parse the extension data from the position, as if the packet in
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* @data is a client hello (without record or handshake headers) -
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* as provided by gnutls_handshake_set_hook_function().
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*
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* The return value of the callback will be propagated.
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*
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* Returns: %GNUTLS_E_SUCCESS on success, or an error code. On unknown
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* flags it returns %GNUTLS_E_INVALID_REQUEST.
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*
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* Since: 3.6.3
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**/
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int gnutls_ext_raw_parse(void *ctx, gnutls_ext_raw_process_func cb,
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const gnutls_datum_t *data, unsigned int flags)
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{
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if (flags & GNUTLS_EXT_RAW_FLAG_TLS_CLIENT_HELLO) {
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size_t size = data->size;
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size_t len;
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uint8_t *p = data->data;
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DECR_LEN(size, HANDSHAKE_SESSION_ID_POS);
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if (p[0] != 0x03)
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return gnutls_assert_val(GNUTLS_E_UNSUPPORTED_VERSION_PACKET);
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p += HANDSHAKE_SESSION_ID_POS;
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/* skip session id */
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DECR_LEN(size, 1);
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len = p[0];
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p++;
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DECR_LEN(size, len);
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p += len;
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/* CipherSuites */
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DECR_LEN(size, 2);
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len = _gnutls_read_uint16(p);
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p += 2;
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DECR_LEN(size, len);
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p += len;
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/* legacy_compression_methods */
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DECR_LEN(size, 1);
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len = p[0];
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p++;
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DECR_LEN(size, len);
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p += len;
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if (size == 0)
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return gnutls_assert_val(GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE);
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return _gnutls_extv_parse(ctx, cb, p, size);
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} else if (flags & GNUTLS_EXT_RAW_FLAG_DTLS_CLIENT_HELLO) {
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size_t size = data->size;
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size_t len;
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uint8_t *p = data->data;
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DECR_LEN(size, HANDSHAKE_SESSION_ID_POS);
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if (p[0] != 254)
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return gnutls_assert_val(GNUTLS_E_UNSUPPORTED_VERSION_PACKET);
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p += HANDSHAKE_SESSION_ID_POS;
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/* skip session id */
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DECR_LEN(size, 1);
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len = p[0];
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p++;
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DECR_LEN(size, len);
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p += len;
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/* skip cookie */
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DECR_LEN(size, 1);
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len = p[0];
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p++;
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DECR_LEN(size, len);
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p += len;
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/* CipherSuites */
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DECR_LEN(size, 2);
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len = _gnutls_read_uint16(p);
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p += 2;
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DECR_LEN(size, len);
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p += len;
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/* legacy_compression_methods */
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DECR_LEN(size, 1);
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len = p[0];
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p++;
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DECR_LEN(size, len);
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p += len;
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if (size == 0)
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return gnutls_assert_val(GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE);
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return _gnutls_extv_parse(ctx, cb, p, size);
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}
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if (flags != 0)
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return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);
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return _gnutls_extv_parse(ctx, cb, data->data, data->size);
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}
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/* Returns:
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* * On success the number of bytes appended (always positive), or zero if not sent
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* * On failure, a negative error code.
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*/
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int _gnutls_extv_append(gnutls_buffer_st *buf,
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uint16_t tls_id,
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void *ctx,
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int (*cb)(void *ctx, gnutls_buffer_st *buf))
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{
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int size_pos, appended, ret;
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size_t size_prev;
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ret = _gnutls_buffer_append_prefix(buf, 16, tls_id);
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if (ret < 0)
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return gnutls_assert_val(ret);
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size_pos = buf->length;
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ret = _gnutls_buffer_append_prefix(buf, 16, 0);
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if (ret < 0)
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return gnutls_assert_val(ret);
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size_prev = buf->length;
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ret = cb(ctx, buf);
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if (ret < 0 && ret != GNUTLS_E_INT_RET_0) {
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return gnutls_assert_val(ret);
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}
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/* returning GNUTLS_E_INT_RET_0 means to send an empty
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* extension of this type.
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*/
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appended = buf->length - size_prev;
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if (appended > 0 || ret == GNUTLS_E_INT_RET_0) {
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if (ret == GNUTLS_E_INT_RET_0)
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appended = 0;
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/* write the real size */
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_gnutls_write_uint16(appended,
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&buf->data[size_pos]);
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} else if (appended == 0) {
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buf->length -= 4; /* reset type and size */
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return 0;
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}
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return appended + 4;
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}
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