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/*
* TLS 1.2 and 1.3 client-side functions
*
* Copyright The Mbed TLS Contributors
* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
*/
#include "common.h"
#if defined(MBEDTLS_SSL_CLI_C)
#if defined(MBEDTLS_SSL_PROTO_TLS1_3) || defined(MBEDTLS_SSL_PROTO_TLS1_2)
#include <string.h>
#include "debug_internal.h"
#include "mbedtls/error.h"
#include "mbedtls/platform.h"
#include "ssl_client.h"
#include "ssl_misc.h"
#include "ssl_tls13_keys.h"
#include "ssl_debug_helpers.h"
#if defined(MBEDTLS_SSL_SERVER_NAME_INDICATION)
MBEDTLS_CHECK_RETURN_CRITICAL
static int ssl_write_hostname_ext(mbedtls_ssl_context *ssl,
unsigned char *buf,
const unsigned char *end,
size_t *olen)
{
unsigned char *p = buf;
size_t hostname_len;
*olen = 0;
if (ssl->hostname == NULL) {
return 0;
}
MBEDTLS_SSL_DEBUG_MSG(3,
("client hello, adding server name extension: %s",
ssl->hostname));
hostname_len = strlen(ssl->hostname);
MBEDTLS_SSL_CHK_BUF_PTR(p, end, hostname_len + 9);
/*
* Sect. 3, RFC 6066 (TLS Extensions Definitions)
*
* In order to provide any of the server names, clients MAY include an
* extension of type "server_name" in the (extended) client hello. The
* "extension_data" field of this extension SHALL contain
* "ServerNameList" where:
*
* struct {
* NameType name_type;
* select (name_type) {
* case host_name: HostName;
* } name;
* } ServerName;
*
* enum {
* host_name(0), (255)
* } NameType;
*
* opaque HostName<1..2^16-1>;
*
* struct {
* ServerName server_name_list<1..2^16-1>
* } ServerNameList;
*
*/
MBEDTLS_PUT_UINT16_BE(MBEDTLS_TLS_EXT_SERVERNAME, p, 0);
p += 2;
MBEDTLS_PUT_UINT16_BE(hostname_len + 5, p, 0);
p += 2;
MBEDTLS_PUT_UINT16_BE(hostname_len + 3, p, 0);
p += 2;
*p++ = MBEDTLS_BYTE_0(MBEDTLS_TLS_EXT_SERVERNAME_HOSTNAME);
MBEDTLS_PUT_UINT16_BE(hostname_len, p, 0);
p += 2;
memcpy(p, ssl->hostname, hostname_len);
*olen = hostname_len + 9;
#if defined(MBEDTLS_SSL_PROTO_TLS1_3)
mbedtls_ssl_tls13_set_hs_sent_ext_mask(ssl, MBEDTLS_TLS_EXT_SERVERNAME);
#endif /* MBEDTLS_SSL_PROTO_TLS1_3 */
return 0;
}
#endif /* MBEDTLS_SSL_SERVER_NAME_INDICATION */
#if defined(MBEDTLS_SSL_ALPN)
/*
* ssl_write_alpn_ext()
*
* Structure of the application_layer_protocol_negotiation extension in
* ClientHello:
*
* opaque ProtocolName<1..2^8-1>;
*
* struct {
* ProtocolName protocol_name_list<2..2^16-1>
* } ProtocolNameList;
*
*/
MBEDTLS_CHECK_RETURN_CRITICAL
static int ssl_write_alpn_ext(mbedtls_ssl_context *ssl,
unsigned char *buf,
const unsigned char *end,
size_t *out_len)
{
unsigned char *p = buf;
*out_len = 0;
if (ssl->conf->alpn_list == NULL) {
return 0;
}
MBEDTLS_SSL_DEBUG_MSG(3, ("client hello, adding alpn extension"));
/* Check we have enough space for the extension type (2 bytes), the
* extension length (2 bytes) and the protocol_name_list length (2 bytes).
*/
MBEDTLS_SSL_CHK_BUF_PTR(p, end, 6);
MBEDTLS_PUT_UINT16_BE(MBEDTLS_TLS_EXT_ALPN, p, 0);
/* Skip writing extension and list length for now */
p += 6;
/*
* opaque ProtocolName<1..2^8-1>;
*
* struct {
* ProtocolName protocol_name_list<2..2^16-1>
* } ProtocolNameList;
*/
for (const char **cur = ssl->conf->alpn_list; *cur != NULL; cur++) {
/*
* mbedtls_ssl_conf_set_alpn_protocols() checked that the length of
* protocol names is less than 255.
*/
size_t protocol_name_len = strlen(*cur);
MBEDTLS_SSL_CHK_BUF_PTR(p, end, 1 + protocol_name_len);
*p++ = (unsigned char) protocol_name_len;
memcpy(p, *cur, protocol_name_len);
p += protocol_name_len;
}
*out_len = (size_t) (p - buf);
/* List length = *out_len - 2 (ext_type) - 2 (ext_len) - 2 (list_len) */
MBEDTLS_PUT_UINT16_BE(*out_len - 6, buf, 4);
/* Extension length = *out_len - 2 (ext_type) - 2 (ext_len) */
MBEDTLS_PUT_UINT16_BE(*out_len - 4, buf, 2);
#if defined(MBEDTLS_SSL_PROTO_TLS1_3)
mbedtls_ssl_tls13_set_hs_sent_ext_mask(ssl, MBEDTLS_TLS_EXT_ALPN);
#endif /* MBEDTLS_SSL_PROTO_TLS1_3 */
return 0;
}
#endif /* MBEDTLS_SSL_ALPN */
#if defined(MBEDTLS_SSL_TLS1_2_SOME_ECC) || \
defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_EPHEMERAL_ENABLED)
/*
* Function for writing a supported groups (TLS 1.3) or supported elliptic
* curves (TLS 1.2) extension.
*
* The "extension_data" field of a supported groups extension contains a
* "NamedGroupList" value (TLS 1.3 RFC8446):
* enum {
* secp256r1(0x0017), secp384r1(0x0018), secp521r1(0x0019),
* x25519(0x001D), x448(0x001E),
* ffdhe2048(0x0100), ffdhe3072(0x0101), ffdhe4096(0x0102),
* ffdhe6144(0x0103), ffdhe8192(0x0104),
* ffdhe_private_use(0x01FC..0x01FF),
* ecdhe_private_use(0xFE00..0xFEFF),
* (0xFFFF)
* } NamedGroup;
* struct {
* NamedGroup named_group_list<2..2^16-1>;
* } NamedGroupList;
*
* The "extension_data" field of a supported elliptic curves extension contains
* a "NamedCurveList" value (TLS 1.2 RFC 8422):
* enum {
* deprecated(1..22),
* secp256r1 (23), secp384r1 (24), secp521r1 (25),
* x25519(29), x448(30),
* reserved (0xFE00..0xFEFF),
* deprecated(0xFF01..0xFF02),
* (0xFFFF)
* } NamedCurve;
* struct {
* NamedCurve named_curve_list<2..2^16-1>
* } NamedCurveList;
*
* The TLS 1.3 supported groups extension was defined to be a compatible
* generalization of the TLS 1.2 supported elliptic curves extension. They both
* share the same extension identifier.
*
*/
#define SSL_WRITE_SUPPORTED_GROUPS_EXT_TLS1_2_FLAG 1
#define SSL_WRITE_SUPPORTED_GROUPS_EXT_TLS1_3_FLAG 2
MBEDTLS_CHECK_RETURN_CRITICAL
static int ssl_write_supported_groups_ext(mbedtls_ssl_context *ssl,
unsigned char *buf,
const unsigned char *end,
int flags,
size_t *out_len)
{
unsigned char *p = buf;
unsigned char *named_group_list; /* Start of named_group_list */
size_t named_group_list_len; /* Length of named_group_list */
const uint16_t *group_list = mbedtls_ssl_get_groups(ssl);
*out_len = 0;
MBEDTLS_SSL_DEBUG_MSG(3, ("client hello, adding supported_groups extension"));
/* Check if we have space for header and length fields:
* - extension_type (2 bytes)
* - extension_data_length (2 bytes)
* - named_group_list_length (2 bytes)
*/
MBEDTLS_SSL_CHK_BUF_PTR(p, end, 6);
p += 6;
named_group_list = p;
if (group_list == NULL) {
return MBEDTLS_ERR_SSL_BAD_CONFIG;
}
for (; *group_list != 0; group_list++) {
int propose_group = 0;
MBEDTLS_SSL_DEBUG_MSG(3, ("got supported group(%04x)", *group_list));
#if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_EPHEMERAL_ENABLED)
if (flags & SSL_WRITE_SUPPORTED_GROUPS_EXT_TLS1_3_FLAG) {
#if defined(PSA_WANT_ALG_ECDH)
if (mbedtls_ssl_tls13_named_group_is_ecdhe(*group_list) &&
(mbedtls_ssl_get_ecp_group_id_from_tls_id(*group_list) !=
MBEDTLS_ECP_DP_NONE)) {
propose_group = 1;
}
#endif
#if defined(PSA_WANT_ALG_FFDH)
if (mbedtls_ssl_tls13_named_group_is_ffdh(*group_list)) {
propose_group = 1;
}
#endif
}
#endif /* MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_EPHEMERAL_ENABLED */
#if defined(MBEDTLS_SSL_TLS1_2_SOME_ECC)
if ((flags & SSL_WRITE_SUPPORTED_GROUPS_EXT_TLS1_2_FLAG) &&
mbedtls_ssl_tls12_named_group_is_ecdhe(*group_list) &&
(mbedtls_ssl_get_ecp_group_id_from_tls_id(*group_list) !=
MBEDTLS_ECP_DP_NONE)) {
propose_group = 1;
}
#endif /* MBEDTLS_SSL_TLS1_2_SOME_ECC */
if (propose_group) {
MBEDTLS_SSL_CHK_BUF_PTR(p, end, 2);
MBEDTLS_PUT_UINT16_BE(*group_list, p, 0);
p += 2;
MBEDTLS_SSL_DEBUG_MSG(3, ("NamedGroup: %s ( %x )",
mbedtls_ssl_named_group_to_str(*group_list),
*group_list));
}
}
/* Length of named_group_list */
named_group_list_len = (size_t) (p - named_group_list);
if (named_group_list_len == 0) {
MBEDTLS_SSL_DEBUG_MSG(1, ("No group available."));
return MBEDTLS_ERR_SSL_INTERNAL_ERROR;
}
/* Write extension_type */
MBEDTLS_PUT_UINT16_BE(MBEDTLS_TLS_EXT_SUPPORTED_GROUPS, buf, 0);
/* Write extension_data_length */
MBEDTLS_PUT_UINT16_BE(named_group_list_len + 2, buf, 2);
/* Write length of named_group_list */
MBEDTLS_PUT_UINT16_BE(named_group_list_len, buf, 4);
MBEDTLS_SSL_DEBUG_BUF(3, "Supported groups extension",
buf + 4, named_group_list_len + 2);
*out_len = (size_t) (p - buf);
#if defined(MBEDTLS_SSL_PROTO_TLS1_3)
mbedtls_ssl_tls13_set_hs_sent_ext_mask(
ssl, MBEDTLS_TLS_EXT_SUPPORTED_GROUPS);
#endif /* MBEDTLS_SSL_PROTO_TLS1_3 */
return 0;
}
#endif /* MBEDTLS_SSL_TLS1_2_SOME_ECC ||
MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_EPHEMERAL_ENABLED */
MBEDTLS_CHECK_RETURN_CRITICAL
static int ssl_write_client_hello_cipher_suites(
mbedtls_ssl_context *ssl,
unsigned char *buf,
unsigned char *end,
int *tls12_uses_ec,
size_t *out_len)
{
unsigned char *p = buf;
const int *ciphersuite_list;
unsigned char *cipher_suites; /* Start of the cipher_suites list */
size_t cipher_suites_len;
*tls12_uses_ec = 0;
*out_len = 0;
/*
* Ciphersuite list
*
* This is a list of the symmetric cipher options supported by
* the client, specifically the record protection algorithm
* ( including secret key length ) and a hash to be used with
* HKDF, in descending order of client preference.
*/
ciphersuite_list = ssl->conf->ciphersuite_list;
/* Check there is space for the cipher suite list length (2 bytes). */
MBEDTLS_SSL_CHK_BUF_PTR(p, end, 2);
p += 2;
/* Write cipher_suites
* CipherSuite cipher_suites<2..2^16-2>;
*/
cipher_suites = p;
for (size_t i = 0; ciphersuite_list[i] != 0; i++) {
int cipher_suite = ciphersuite_list[i];
const mbedtls_ssl_ciphersuite_t *ciphersuite_info;
ciphersuite_info = mbedtls_ssl_ciphersuite_from_id(cipher_suite);
if (mbedtls_ssl_validate_ciphersuite(ssl, ciphersuite_info,
ssl->handshake->min_tls_version,
ssl->tls_version) != 0) {
continue;
}
#if defined(MBEDTLS_SSL_PROTO_TLS1_2) && \
(defined(MBEDTLS_KEY_EXCHANGE_SOME_ECDH_OR_ECDHE_1_2_ENABLED) || \
defined(MBEDTLS_KEY_EXCHANGE_ECDSA_CERT_REQ_ALLOWED_ENABLED) || \
defined(MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED))
*tls12_uses_ec |= mbedtls_ssl_ciphersuite_uses_ec(ciphersuite_info);
#endif
MBEDTLS_SSL_DEBUG_MSG(3, ("client hello, add ciphersuite: %04x, %s",
(unsigned int) cipher_suite,
ciphersuite_info->name));
/* Check there is space for the cipher suite identifier (2 bytes). */
MBEDTLS_SSL_CHK_BUF_PTR(p, end, 2);
MBEDTLS_PUT_UINT16_BE(cipher_suite, p, 0);
p += 2;
}
/*
* Add TLS_EMPTY_RENEGOTIATION_INFO_SCSV
*/
int renegotiating = 0;
#if defined(MBEDTLS_SSL_RENEGOTIATION)
renegotiating = (ssl->renego_status != MBEDTLS_SSL_INITIAL_HANDSHAKE);
#endif
if (!renegotiating) {
MBEDTLS_SSL_DEBUG_MSG(3, ("adding EMPTY_RENEGOTIATION_INFO_SCSV"));
MBEDTLS_SSL_CHK_BUF_PTR(p, end, 2);
MBEDTLS_PUT_UINT16_BE(MBEDTLS_SSL_EMPTY_RENEGOTIATION_INFO, p, 0);
p += 2;
}
/* Write the cipher_suites length in number of bytes */
cipher_suites_len = (size_t) (p - cipher_suites);
MBEDTLS_PUT_UINT16_BE(cipher_suites_len, buf, 0);
MBEDTLS_SSL_DEBUG_MSG(3,
("client hello, got %" MBEDTLS_PRINTF_SIZET " cipher suites",
cipher_suites_len/2));
/* Output the total length of cipher_suites field. */
*out_len = (size_t) (p - buf);
return 0;
}
/*
* Structure of the TLS 1.3 ClientHello message:
*
* struct {
* ProtocolVersion legacy_version = 0x0303; // TLS v1.2
* Random random;
* opaque legacy_session_id<0..32>;
* CipherSuite cipher_suites<2..2^16-2>;
* opaque legacy_compression_methods<1..2^8-1>;
* Extension extensions<8..2^16-1>;
* } ClientHello;
*
* Structure of the (D)TLS 1.2 ClientHello message:
*
* struct {
* ProtocolVersion client_version;
* Random random;
* SessionID session_id;
* opaque cookie<0..2^8-1>; // DTLS 1.2 ONLY
* CipherSuite cipher_suites<2..2^16-2>;
* CompressionMethod compression_methods<1..2^8-1>;
* select (extensions_present) {
* case false:
* struct {};
* case true:
* Extension extensions<0..2^16-1>;
* };
* } ClientHello;
*/
MBEDTLS_CHECK_RETURN_CRITICAL
static int ssl_write_client_hello_body(mbedtls_ssl_context *ssl,
unsigned char *buf,
unsigned char *end,
size_t *out_len,
size_t *binders_len)
{
int ret;
mbedtls_ssl_handshake_params *handshake = ssl->handshake;
unsigned char *p = buf;
unsigned char *p_extensions_len; /* Pointer to extensions length */
size_t output_len; /* Length of buffer used by function */
size_t extensions_len; /* Length of the list of extensions*/
int tls12_uses_ec = 0;
*out_len = 0;
*binders_len = 0;
#if defined(MBEDTLS_SSL_PROTO_TLS1_2)
unsigned char propose_tls12 =
(handshake->min_tls_version <= MBEDTLS_SSL_VERSION_TLS1_2)
&&
(MBEDTLS_SSL_VERSION_TLS1_2 <= ssl->tls_version);
#endif
#if defined(MBEDTLS_SSL_PROTO_TLS1_3)
unsigned char propose_tls13 =
(handshake->min_tls_version <= MBEDTLS_SSL_VERSION_TLS1_3)
&&
(MBEDTLS_SSL_VERSION_TLS1_3 <= ssl->tls_version);
#endif
/*
* Write client_version (TLS 1.2) or legacy_version (TLS 1.3)
*
* In all cases this is the TLS 1.2 version.
*/
MBEDTLS_SSL_CHK_BUF_PTR(p, end, 2);
mbedtls_ssl_write_version(p, ssl->conf->transport,
MBEDTLS_SSL_VERSION_TLS1_2);
p += 2;
/* ...
* Random random;
* ...
*
* The random bytes have been prepared by ssl_prepare_client_hello() into
* the handshake->randbytes buffer and are copied here into the output
* buffer.
*/
MBEDTLS_SSL_CHK_BUF_PTR(p, end, MBEDTLS_CLIENT_HELLO_RANDOM_LEN);
memcpy(p, handshake->randbytes, MBEDTLS_CLIENT_HELLO_RANDOM_LEN);
MBEDTLS_SSL_DEBUG_BUF(3, "client hello, random bytes",
p, MBEDTLS_CLIENT_HELLO_RANDOM_LEN);
p += MBEDTLS_CLIENT_HELLO_RANDOM_LEN;
/* TLS 1.2:
* ...
* SessionID session_id;
* ...
* with
* opaque SessionID<0..32>;
*
* TLS 1.3:
* ...
* opaque legacy_session_id<0..32>;
* ...
*
* The (legacy) session identifier bytes have been prepared by
* ssl_prepare_client_hello() into the ssl->session_negotiate->id buffer
* and are copied here into the output buffer.
*/
MBEDTLS_SSL_CHK_BUF_PTR(p, end, ssl->session_negotiate->id_len + 1);
*p++ = (unsigned char) ssl->session_negotiate->id_len;
memcpy(p, ssl->session_negotiate->id, ssl->session_negotiate->id_len);
p += ssl->session_negotiate->id_len;
MBEDTLS_SSL_DEBUG_BUF(3, "session id", ssl->session_negotiate->id,
ssl->session_negotiate->id_len);
/* DTLS 1.2 ONLY
* ...
* opaque cookie<0..2^8-1>;
* ...
*/
#if defined(MBEDTLS_SSL_PROTO_TLS1_2) && defined(MBEDTLS_SSL_PROTO_DTLS)
if (ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM) {
#if !defined(MBEDTLS_SSL_PROTO_TLS1_3)
uint8_t cookie_len = 0;
#else
uint16_t cookie_len = 0;
#endif /* !MBEDTLS_SSL_PROTO_TLS1_3 */
if (handshake->cookie != NULL) {
MBEDTLS_SSL_DEBUG_BUF(3, "client hello, cookie",
handshake->cookie,
handshake->cookie_len);
cookie_len = handshake->cookie_len;
}
MBEDTLS_SSL_CHK_BUF_PTR(p, end, cookie_len + 1);
*p++ = (unsigned char) cookie_len;
if (cookie_len > 0) {
memcpy(p, handshake->cookie, cookie_len);
p += cookie_len;
}
}
#endif /* MBEDTLS_SSL_PROTO_TLS1_2 && MBEDTLS_SSL_PROTO_DTLS */
/* Write cipher_suites */
ret = ssl_write_client_hello_cipher_suites(ssl, p, end,
&tls12_uses_ec,
&output_len);
if (ret != 0) {
return ret;
}
p += output_len;
/* Write legacy_compression_methods (TLS 1.3) or
* compression_methods (TLS 1.2)
*
* For every TLS 1.3 ClientHello, this vector MUST contain exactly
* one byte set to zero, which corresponds to the 'null' compression
* method in prior versions of TLS.
*
* For TLS 1.2 ClientHello, for security reasons we do not support
* compression anymore, thus also just the 'null' compression method.
*/
MBEDTLS_SSL_CHK_BUF_PTR(p, end, 2);
*p++ = 1;
*p++ = MBEDTLS_SSL_COMPRESS_NULL;
/* Write extensions */
#if defined(MBEDTLS_SSL_PROTO_TLS1_3)
/* Keeping track of the included extensions */
handshake->sent_extensions = MBEDTLS_SSL_EXT_MASK_NONE;
#endif
/* First write extensions, then the total length */
MBEDTLS_SSL_CHK_BUF_PTR(p, end, 2);
p_extensions_len = p;
p += 2;
#if defined(MBEDTLS_SSL_SERVER_NAME_INDICATION)
/* Write server name extension */
ret = ssl_write_hostname_ext(ssl, p, end, &output_len);
if (ret != 0) {
return ret;
}
p += output_len;
#endif /* MBEDTLS_SSL_SERVER_NAME_INDICATION */
#if defined(MBEDTLS_SSL_ALPN)
ret = ssl_write_alpn_ext(ssl, p, end, &output_len);
if (ret != 0) {
return ret;
}
p += output_len;
#endif /* MBEDTLS_SSL_ALPN */
#if defined(MBEDTLS_SSL_PROTO_TLS1_3)
if (propose_tls13) {
ret = mbedtls_ssl_tls13_write_client_hello_exts(ssl, p, end,
&output_len);
if (ret != 0) {
return ret;
}
p += output_len;
}
#endif
#if defined(MBEDTLS_SSL_TLS1_2_SOME_ECC) || \
defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_EPHEMERAL_ENABLED)
{
int ssl_write_supported_groups_ext_flags = 0;
#if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_EPHEMERAL_ENABLED)
if (propose_tls13 && mbedtls_ssl_conf_tls13_is_some_ephemeral_enabled(ssl)) {
ssl_write_supported_groups_ext_flags |=
SSL_WRITE_SUPPORTED_GROUPS_EXT_TLS1_3_FLAG;
}
#endif
#if defined(MBEDTLS_SSL_TLS1_2_SOME_ECC)
if (propose_tls12 && tls12_uses_ec) {
ssl_write_supported_groups_ext_flags |=
SSL_WRITE_SUPPORTED_GROUPS_EXT_TLS1_2_FLAG;
}
#endif
if (ssl_write_supported_groups_ext_flags != 0) {
ret = ssl_write_supported_groups_ext(ssl, p, end,
ssl_write_supported_groups_ext_flags,
&output_len);
if (ret != 0) {
return ret;
}
p += output_len;
}
}
#endif /* MBEDTLS_SSL_TLS1_2_SOME_ECC ||
MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_EPHEMERAL_ENABLED */
#if defined(MBEDTLS_SSL_HANDSHAKE_WITH_CERT_ENABLED)
int write_sig_alg_ext = 0;
#if defined(MBEDTLS_SSL_PROTO_TLS1_3)
write_sig_alg_ext = write_sig_alg_ext ||
(propose_tls13 && mbedtls_ssl_conf_tls13_is_ephemeral_enabled(ssl));
#endif
#if defined(MBEDTLS_SSL_PROTO_TLS1_2)
write_sig_alg_ext = write_sig_alg_ext || propose_tls12;
#endif
if (write_sig_alg_ext) {
ret = mbedtls_ssl_write_sig_alg_ext(ssl, p, end, &output_len);
if (ret != 0) {
return ret;
}
p += output_len;
}
#endif /* MBEDTLS_SSL_HANDSHAKE_WITH_CERT_ENABLED */
#if defined(MBEDTLS_SSL_PROTO_TLS1_2)
if (propose_tls12) {
ret = mbedtls_ssl_tls12_write_client_hello_exts(ssl, p, end,
tls12_uses_ec,
&output_len);
if (ret != 0) {
return ret;
}
p += output_len;
}
#endif /* MBEDTLS_SSL_PROTO_TLS1_2 */
#if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_PSK_ENABLED)
/* The "pre_shared_key" extension (RFC 8446 Section 4.2.11)
* MUST be the last extension in the ClientHello.
*/
if (propose_tls13 && mbedtls_ssl_conf_tls13_is_some_psk_enabled(ssl)) {
ret = mbedtls_ssl_tls13_write_identities_of_pre_shared_key_ext(
ssl, p, end, &output_len, binders_len);
if (ret != 0) {
return ret;
}
p += output_len;
}
#endif /* MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_PSK_ENABLED */
/* Write the length of the list of extensions. */
extensions_len = (size_t) (p - p_extensions_len) - 2;
if (extensions_len == 0) {
p = p_extensions_len;
} else {
MBEDTLS_PUT_UINT16_BE(extensions_len, p_extensions_len, 0);
MBEDTLS_SSL_DEBUG_MSG(3, ("client hello, total extension length: %" \
MBEDTLS_PRINTF_SIZET, extensions_len));
MBEDTLS_SSL_DEBUG_BUF(3, "client hello extensions",
p_extensions_len, extensions_len);
}
*out_len = (size_t) (p - buf);
return 0;
}
MBEDTLS_CHECK_RETURN_CRITICAL
static int ssl_generate_random(mbedtls_ssl_context *ssl)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
unsigned char *randbytes = ssl->handshake->randbytes;
size_t gmt_unix_time_len = 0;
/*
* Generate the random bytes
*
* TLS 1.2 case:
* struct {
* uint32 gmt_unix_time;
* opaque random_bytes[28];
* } Random;
*
* TLS 1.3 case:
* opaque Random[32];
*/
if (ssl->tls_version == MBEDTLS_SSL_VERSION_TLS1_2) {
#if defined(MBEDTLS_HAVE_TIME)
mbedtls_time_t gmt_unix_time = mbedtls_time(NULL);
MBEDTLS_PUT_UINT32_BE(gmt_unix_time, randbytes, 0);
gmt_unix_time_len = 4;
MBEDTLS_SSL_DEBUG_MSG(3,
("client hello, current time: %" MBEDTLS_PRINTF_LONGLONG,
(long long) gmt_unix_time));
#endif /* MBEDTLS_HAVE_TIME */
}
ret = ssl->conf->f_rng(ssl->conf->p_rng,
randbytes + gmt_unix_time_len,
MBEDTLS_CLIENT_HELLO_RANDOM_LEN - gmt_unix_time_len);
return ret;
}
MBEDTLS_CHECK_RETURN_CRITICAL
static int ssl_prepare_client_hello(mbedtls_ssl_context *ssl)
{
int ret;
size_t session_id_len;
mbedtls_ssl_session *session_negotiate = ssl->session_negotiate;
if (session_negotiate == NULL) {
return MBEDTLS_ERR_SSL_INTERNAL_ERROR;
}
#if defined(MBEDTLS_SSL_PROTO_TLS1_3) && \
defined(MBEDTLS_SSL_SESSION_TICKETS) && \
defined(MBEDTLS_HAVE_TIME)
/* Check if a tls13 ticket has been configured. */
if (ssl->handshake->resume != 0 &&
session_negotiate->tls_version == MBEDTLS_SSL_VERSION_TLS1_3 &&
session_negotiate->ticket != NULL) {
mbedtls_ms_time_t now = mbedtls_ms_time();
mbedtls_ms_time_t age = now - session_negotiate->ticket_reception_time;
if (age < 0 ||
age > (mbedtls_ms_time_t) session_negotiate->ticket_lifetime * 1000) {
/* Without valid ticket, disable session resumption.*/
MBEDTLS_SSL_DEBUG_MSG(
3, ("Ticket expired, disable session resumption"));
ssl->handshake->resume = 0;
}
}
#endif /* MBEDTLS_SSL_PROTO_TLS1_3 &&
MBEDTLS_SSL_SESSION_TICKETS &&
MBEDTLS_HAVE_TIME */
/* Bet on the highest configured version if we are not in a TLS 1.2
* renegotiation or session resumption.
*/
#if defined(MBEDTLS_SSL_RENEGOTIATION)
if (ssl->renego_status != MBEDTLS_SSL_INITIAL_HANDSHAKE) {
ssl->handshake->min_tls_version = ssl->tls_version;
} else
#endif
{
if (ssl->handshake->resume) {
ssl->tls_version = session_negotiate->tls_version;
ssl->handshake->min_tls_version = ssl->tls_version;
} else {
ssl->handshake->min_tls_version = ssl->conf->min_tls_version;
}
}
/*
* Generate the random bytes, except when responding to a verify request
* where we MUST reuse the previously generated random bytes
* (RFC 6347 4.2.1).
*/
#if defined(MBEDTLS_SSL_PROTO_DTLS)
if ((ssl->conf->transport != MBEDTLS_SSL_TRANSPORT_DATAGRAM) ||
(ssl->handshake->cookie == NULL))
#endif
{
#if defined(MBEDTLS_SSL_PROTO_TLS1_3)
if (!ssl->handshake->hello_retry_request_flag)
#endif
{
ret = ssl_generate_random(ssl);
if (ret != 0) {
MBEDTLS_SSL_DEBUG_RET(1, "Random bytes generation failed", ret);
return ret;
}
}
}
/*
* Prepare session identifier. At that point, the length of the session
* identifier in the SSL context `ssl->session_negotiate->id_len` is equal
* to zero, except in the case of a TLS 1.2 session renegotiation or
* session resumption.
*/
session_id_len = session_negotiate->id_len;
#if defined(MBEDTLS_SSL_PROTO_TLS1_2)
if (ssl->tls_version == MBEDTLS_SSL_VERSION_TLS1_2) {
if (session_id_len < 16 || session_id_len > 32 ||
#if defined(MBEDTLS_SSL_RENEGOTIATION)
ssl->renego_status != MBEDTLS_SSL_INITIAL_HANDSHAKE ||
#endif
ssl->handshake->resume == 0) {
session_id_len = 0;
}
#if defined(MBEDTLS_SSL_SESSION_TICKETS)
/*
* RFC 5077 section 3.4: "When presenting a ticket, the client MAY
* generate and include a Session ID in the TLS ClientHello."
*/
int renegotiating = 0;
#if defined(MBEDTLS_SSL_RENEGOTIATION)
if (ssl->renego_status != MBEDTLS_SSL_INITIAL_HANDSHAKE) {
renegotiating = 1;
}
#endif
if (!renegotiating) {
if ((session_negotiate->ticket != NULL) &&
(session_negotiate->ticket_len != 0)) {
session_id_len = 32;
}
}
#endif /* MBEDTLS_SSL_SESSION_TICKETS */
}
#endif /* MBEDTLS_SSL_PROTO_TLS1_2 */
#if defined(MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE)
if (ssl->tls_version == MBEDTLS_SSL_VERSION_TLS1_3) {
/*
* Create a legacy session identifier for the purpose of middlebox
* compatibility only if one has not been created already, which is
* the case if we are here for the TLS 1.3 second ClientHello.
*
* Versions of TLS before TLS 1.3 supported a "session resumption"
* feature which has been merged with pre-shared keys in TLS 1.3
* version. A client which has a cached session ID set by a pre-TLS 1.3
* server SHOULD set this field to that value. In compatibility mode,
* this field MUST be non-empty, so a client not offering a pre-TLS 1.3
* session MUST generate a new 32-byte value. This value need not be
* random but SHOULD be unpredictable to avoid implementations fixating
* on a specific value (also known as ossification). Otherwise, it MUST
* be set as a zero-length vector ( i.e., a zero-valued single byte
* length field ).
*/
session_id_len = 32;
}
#endif /* MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE */
if (session_id_len != session_negotiate->id_len) {
session_negotiate->id_len = session_id_len;
if (session_id_len > 0) {
ret = ssl->conf->f_rng(ssl->conf->p_rng,
session_negotiate->id,
session_id_len);
if (ret != 0) {
MBEDTLS_SSL_DEBUG_RET(1, "creating session id failed", ret);
return ret;
}
}
}
#if defined(MBEDTLS_SSL_PROTO_TLS1_3) && \
defined(MBEDTLS_SSL_SESSION_TICKETS) && \
defined(MBEDTLS_SSL_SERVER_NAME_INDICATION)
if (ssl->tls_version == MBEDTLS_SSL_VERSION_TLS1_3 &&
ssl->handshake->resume) {
int hostname_mismatch = ssl->hostname != NULL ||
session_negotiate->hostname != NULL;
if (ssl->hostname != NULL && session_negotiate->hostname != NULL) {
hostname_mismatch = strcmp(
ssl->hostname, session_negotiate->hostname) != 0;
}
if (hostname_mismatch) {
MBEDTLS_SSL_DEBUG_MSG(
1, ("Hostname mismatch the session ticket, "
"disable session resumption."));
return MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
}
} else {
return mbedtls_ssl_session_set_hostname(session_negotiate,
ssl->hostname);
}
#endif /* MBEDTLS_SSL_PROTO_TLS1_3 &&
MBEDTLS_SSL_SESSION_TICKETS &&
MBEDTLS_SSL_SERVER_NAME_INDICATION */
return 0;
}
/*
* Write ClientHello handshake message.
* Handler for MBEDTLS_SSL_CLIENT_HELLO
*/
int mbedtls_ssl_write_client_hello(mbedtls_ssl_context *ssl)
{
int ret = 0;
unsigned char *buf;
size_t buf_len, msg_len, binders_len;
MBEDTLS_SSL_DEBUG_MSG(2, ("=> write client hello"));
MBEDTLS_SSL_PROC_CHK(ssl_prepare_client_hello(ssl));
MBEDTLS_SSL_PROC_CHK(mbedtls_ssl_start_handshake_msg(
ssl, MBEDTLS_SSL_HS_CLIENT_HELLO,
&buf, &buf_len));
MBEDTLS_SSL_PROC_CHK(ssl_write_client_hello_body(ssl, buf,
buf + buf_len,
&msg_len,
&binders_len));
#if defined(MBEDTLS_SSL_PROTO_TLS1_2) && defined(MBEDTLS_SSL_PROTO_DTLS)
if (ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM) {
ssl->out_msglen = msg_len + 4;
mbedtls_ssl_send_flight_completed(ssl);
/*
* The two functions below may try to send data on the network and
* can return with the MBEDTLS_ERR_SSL_WANT_READ error code when they
* fail to do so and the transmission has to be retried later. In that
* case as in fatal error cases, we return immediately. But we must have
* set the handshake state to the next state at that point to ensure
* that we will not write and send again a ClientHello when we
* eventually succeed in sending the pending data.
*/
mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_SERVER_HELLO);
if ((ret = mbedtls_ssl_write_handshake_msg(ssl)) != 0) {
MBEDTLS_SSL_DEBUG_RET(1, "mbedtls_ssl_write_handshake_msg", ret);
return ret;
}
if ((ret = mbedtls_ssl_flight_transmit(ssl)) != 0) {
MBEDTLS_SSL_DEBUG_RET(1, "mbedtls_ssl_flight_transmit", ret);
return ret;
}
} else
#endif /* MBEDTLS_SSL_PROTO_TLS1_2 && MBEDTLS_SSL_PROTO_DTLS */
{
ret = mbedtls_ssl_add_hs_hdr_to_checksum(ssl,
MBEDTLS_SSL_HS_CLIENT_HELLO,
msg_len);
if (ret != 0) {
MBEDTLS_SSL_DEBUG_RET(1, "mbedtls_ssl_add_hs_hdr_to_checksum", ret);
return ret;
}
ret = ssl->handshake->update_checksum(ssl, buf, msg_len - binders_len);
if (ret != 0) {
MBEDTLS_SSL_DEBUG_RET(1, "update_checksum", ret);
return ret;
}
#if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_PSK_ENABLED)
if (binders_len > 0) {
MBEDTLS_SSL_PROC_CHK(
mbedtls_ssl_tls13_write_binders_of_pre_shared_key_ext(
ssl, buf + msg_len - binders_len, buf + msg_len));
ret = ssl->handshake->update_checksum(ssl, buf + msg_len - binders_len,
binders_len);
if (ret != 0) {
MBEDTLS_SSL_DEBUG_RET(1, "update_checksum", ret);
return ret;
}
}
#endif /* MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_PSK_ENABLED */
MBEDTLS_SSL_PROC_CHK(mbedtls_ssl_finish_handshake_msg(ssl,
buf_len,
msg_len));
/*
* Set next state. Note that if TLS 1.3 is proposed, this may be
* overwritten by mbedtls_ssl_tls13_finalize_client_hello().
*/
mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_SERVER_HELLO);
#if defined(MBEDTLS_SSL_PROTO_TLS1_3)
if (ssl->handshake->min_tls_version <= MBEDTLS_SSL_VERSION_TLS1_3 &&
MBEDTLS_SSL_VERSION_TLS1_3 <= ssl->tls_version) {
ret = mbedtls_ssl_tls13_finalize_client_hello(ssl);
}
#endif
}
#if defined(MBEDTLS_SSL_PROTO_TLS1_3)
MBEDTLS_SSL_PRINT_EXTS(
3, MBEDTLS_SSL_HS_CLIENT_HELLO, ssl->handshake->sent_extensions);
#endif
cleanup:
MBEDTLS_SSL_DEBUG_MSG(2, ("<= write client hello"));
return ret;
}
#endif /* MBEDTLS_SSL_PROTO_TLS1_3 || MBEDTLS_SSL_PROTO_TLS1_2 */
#endif /* MBEDTLS_SSL_CLI_C */
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