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boringssl/ssl/tls13_server.cc

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/* Copyright (c) 2016, Google Inc.
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
#include <openssl/ssl.h>
#include <assert.h>
#include <string.h>
#include <tuple>
#include <openssl/aead.h>
#include <openssl/bytestring.h>
#include <openssl/digest.h>
#include <openssl/err.h>
#include <openssl/mem.h>
#include <openssl/rand.h>
#include <openssl/stack.h>
#include "../crypto/internal.h"
#include "internal.h"
BSSL_NAMESPACE_BEGIN
static const uint8_t kZeroes[EVP_MAX_MD_SIZE] = {0};
// Allow a minute of ticket age skew in either direction. This covers
// transmission delays in ClientHello and NewSessionTicket, as well as
// drift between client and server clock rate since the ticket was issued.
// See RFC 8446, section 8.3.
static const int32_t kMaxTicketAgeSkewSeconds = 60;
static int resolve_ecdhe_secret(SSL_HANDSHAKE *hs, bool *out_need_retry,
SSL_CLIENT_HELLO *client_hello) {
SSL *const ssl = hs->ssl;
*out_need_retry = false;
// We only support connections that include an ECDHE key exchange.
CBS key_share;
if (!ssl_client_hello_get_extension(client_hello, &key_share,
TLSEXT_TYPE_key_share)) {
OPENSSL_PUT_ERROR(SSL, SSL_R_MISSING_KEY_SHARE);
ssl_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_MISSING_EXTENSION);
return 0;
}
bool found_key_share;
Array<uint8_t> dhe_secret;
uint8_t alert = SSL_AD_DECODE_ERROR;
if (!ssl_ext_key_share_parse_clienthello(hs, &found_key_share, &dhe_secret,
&alert, &key_share)) {
ssl_send_alert(ssl, SSL3_AL_FATAL, alert);
return 0;
}
if (!found_key_share) {
*out_need_retry = true;
return 0;
}
return tls13_advance_key_schedule(hs, dhe_secret);
}
static int ssl_ext_supported_versions_add_serverhello(SSL_HANDSHAKE *hs,
CBB *out) {
CBB contents;
if (!CBB_add_u16(out, TLSEXT_TYPE_supported_versions) ||
!CBB_add_u16_length_prefixed(out, &contents) ||
!CBB_add_u16(&contents, hs->ssl->version) ||
!CBB_flush(out)) {
return 0;
}
return 1;
}
static const SSL_CIPHER *choose_tls13_cipher(
const SSL *ssl, const SSL_CLIENT_HELLO *client_hello, uint16_t group_id) {
CBS cipher_suites;
CBS_init(&cipher_suites, client_hello->cipher_suites,
client_hello->cipher_suites_len);
const uint16_t version = ssl_protocol_version(ssl);
return ssl_choose_tls13_cipher(cipher_suites, version, group_id);
}
static bool add_new_session_tickets(SSL_HANDSHAKE *hs, bool *out_sent_tickets) {
SSL *const ssl = hs->ssl;
if (// If the client doesn't accept resumption with PSK_DHE_KE, don't send a
// session ticket.
!hs->accept_psk_mode ||
// We only implement stateless resumption in TLS 1.3, so skip sending
// tickets if disabled.
(SSL_get_options(ssl) & SSL_OP_NO_TICKET)) {
*out_sent_tickets = false;
return true;
}
// TLS 1.3 recommends single-use tickets, so issue multiple tickets in case
// the client makes several connections before getting a renewal.
static const int kNumTickets = 2;
// Rebase the session timestamp so that it is measured from ticket
// issuance.
ssl_session_rebase_time(ssl, hs->new_session.get());
for (int i = 0; i < kNumTickets; i++) {
UniquePtr<SSL_SESSION> session(
SSL_SESSION_dup(hs->new_session.get(), SSL_SESSION_INCLUDE_NONAUTH));
if (!session) {
return false;
}
if (!RAND_bytes((uint8_t *)&session->ticket_age_add, 4)) {
return false;
}
session->ticket_age_add_valid = true;
bool enable_early_data =
ssl->enable_early_data &&
(!ssl->quic_method || !ssl->config->quic_early_data_context.empty());
if (enable_early_data) {
// QUIC does not use the max_early_data_size parameter and always sets it
// to a fixed value. See draft-ietf-quic-tls-22, section 4.5.
session->ticket_max_early_data =
ssl->quic_method != nullptr ? 0xffffffff : kMaxEarlyDataAccepted;
}
static_assert(kNumTickets < 256, "Too many tickets");
uint8_t nonce[] = {static_cast<uint8_t>(i)};
ScopedCBB cbb;
CBB body, nonce_cbb, ticket, extensions;
if (!ssl->method->init_message(ssl, cbb.get(), &body,
SSL3_MT_NEW_SESSION_TICKET) ||
!CBB_add_u32(&body, session->timeout) ||
!CBB_add_u32(&body, session->ticket_age_add) ||
!CBB_add_u8_length_prefixed(&body, &nonce_cbb) ||
!CBB_add_bytes(&nonce_cbb, nonce, sizeof(nonce)) ||
!CBB_add_u16_length_prefixed(&body, &ticket) ||
!tls13_derive_session_psk(session.get(), nonce) ||
!ssl_encrypt_ticket(hs, &ticket, session.get()) ||
!CBB_add_u16_length_prefixed(&body, &extensions)) {
return false;
}
if (enable_early_data) {
CBB early_data;
if (!CBB_add_u16(&extensions, TLSEXT_TYPE_early_data) ||
!CBB_add_u16_length_prefixed(&extensions, &early_data) ||
!CBB_add_u32(&early_data, session->ticket_max_early_data) ||
!CBB_flush(&extensions)) {
return false;
}
}
// Add a fake extension. See draft-davidben-tls-grease-01.
if (!CBB_add_u16(&extensions,
ssl_get_grease_value(hs, ssl_grease_ticket_extension)) ||
!CBB_add_u16(&extensions, 0 /* empty */)) {
return false;
}
if (!ssl_add_message_cbb(ssl, cbb.get())) {
return false;
}
}
*out_sent_tickets = true;
return true;
}
static enum ssl_hs_wait_t do_select_parameters(SSL_HANDSHAKE *hs) {
// At this point, most ClientHello extensions have already been processed by
// the common handshake logic. Resolve the remaining non-PSK parameters.
SSL *const ssl = hs->ssl;
SSLMessage msg;
if (!ssl->method->get_message(ssl, &msg)) {
return ssl_hs_read_message;
}
SSL_CLIENT_HELLO client_hello;
if (!ssl_client_hello_init(ssl, &client_hello, msg)) {
OPENSSL_PUT_ERROR(SSL, SSL_R_CLIENTHELLO_PARSE_FAILED);
ssl_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
return ssl_hs_error;
}
if (ssl->quic_method != nullptr && client_hello.session_id_len > 0) {
OPENSSL_PUT_ERROR(SSL, SSL_R_UNEXPECTED_COMPATIBILITY_MODE);
ssl_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
return ssl_hs_error;
}
OPENSSL_memcpy(hs->session_id, client_hello.session_id,
client_hello.session_id_len);
hs->session_id_len = client_hello.session_id_len;
uint16_t group_id;
if (!tls1_get_shared_group(hs, &group_id)) {
OPENSSL_PUT_ERROR(SSL, SSL_R_NO_SHARED_GROUP);
ssl_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_HANDSHAKE_FAILURE);
return ssl_hs_error;
}
// Negotiate the cipher suite.
hs->new_cipher = choose_tls13_cipher(ssl, &client_hello, group_id);
if (hs->new_cipher == NULL) {
OPENSSL_PUT_ERROR(SSL, SSL_R_NO_SHARED_CIPHER);
ssl_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_HANDSHAKE_FAILURE);
return ssl_hs_error;
}
// HTTP/2 negotiation depends on the cipher suite, so ALPN negotiation was
// deferred. Complete it now.
uint8_t alert = SSL_AD_DECODE_ERROR;
if (!ssl_negotiate_alpn(hs, &alert, &client_hello)) {
ssl_send_alert(ssl, SSL3_AL_FATAL, alert);
return ssl_hs_error;
}
// The PRF hash is now known. Set up the key schedule and hash the
// ClientHello.
if (!hs->transcript.InitHash(ssl_protocol_version(ssl), hs->new_cipher)) {
return ssl_hs_error;
}
hs->tls13_state = state13_select_session;
return ssl_hs_ok;
}
static enum ssl_ticket_aead_result_t select_session(
SSL_HANDSHAKE *hs, uint8_t *out_alert, UniquePtr<SSL_SESSION> *out_session,
int32_t *out_ticket_age_skew, bool *out_offered_ticket,
const SSLMessage &msg, const SSL_CLIENT_HELLO *client_hello) {
SSL *const ssl = hs->ssl;
*out_session = nullptr;
CBS pre_shared_key;
*out_offered_ticket = ssl_client_hello_get_extension(
client_hello, &pre_shared_key, TLSEXT_TYPE_pre_shared_key);
if (!*out_offered_ticket) {
return ssl_ticket_aead_ignore_ticket;
}
// Per RFC8446, section 4.2.9, servers MUST abort the handshake if the client
// sends pre_shared_key without psk_key_exchange_modes.
CBS unused;
if (!ssl_client_hello_get_extension(client_hello, &unused,
TLSEXT_TYPE_psk_key_exchange_modes)) {
*out_alert = SSL_AD_MISSING_EXTENSION;
OPENSSL_PUT_ERROR(SSL, SSL_R_MISSING_EXTENSION);
return ssl_ticket_aead_error;
}
CBS ticket, binders;
uint32_t client_ticket_age;
if (!ssl_ext_pre_shared_key_parse_clienthello(
hs, &ticket, &binders, &client_ticket_age, out_alert, client_hello,
&pre_shared_key)) {
return ssl_ticket_aead_error;
}
// If the peer did not offer psk_dhe, ignore the resumption.
if (!hs->accept_psk_mode) {
return ssl_ticket_aead_ignore_ticket;
}
// TLS 1.3 session tickets are renewed separately as part of the
// NewSessionTicket.
bool unused_renew;
UniquePtr<SSL_SESSION> session;
enum ssl_ticket_aead_result_t ret =
ssl_process_ticket(hs, &session, &unused_renew, ticket, {});
switch (ret) {
case ssl_ticket_aead_success:
break;
case ssl_ticket_aead_error:
*out_alert = SSL_AD_INTERNAL_ERROR;
return ret;
default:
return ret;
}
if (!ssl_session_is_resumable(hs, session.get()) ||
// Historically, some TLS 1.3 tickets were missing ticket_age_add.
!session->ticket_age_add_valid) {
return ssl_ticket_aead_ignore_ticket;
}
// Recover the client ticket age and convert to seconds.
client_ticket_age -= session->ticket_age_add;
client_ticket_age /= 1000;
struct OPENSSL_timeval now;
ssl_get_current_time(ssl, &now);
// Compute the server ticket age in seconds.
assert(now.tv_sec >= session->time);
uint64_t server_ticket_age = now.tv_sec - session->time;
// To avoid overflowing |hs->ticket_age_skew|, we will not resume
// 68-year-old sessions.
if (server_ticket_age > INT32_MAX) {
return ssl_ticket_aead_ignore_ticket;
}
*out_ticket_age_skew = static_cast<int32_t>(client_ticket_age) -
static_cast<int32_t>(server_ticket_age);
// Check the PSK binder.
if (!tls13_verify_psk_binder(hs, session.get(), msg, &binders)) {
*out_alert = SSL_AD_DECRYPT_ERROR;
return ssl_ticket_aead_error;
}
*out_session = std::move(session);
return ssl_ticket_aead_success;
}
static bool quic_ticket_compatible(const SSL_SESSION *session,
const SSL_CONFIG *config) {
if (!session->is_quic) {
return true;
}
if (session->quic_early_data_context.empty() ||
config->quic_early_data_context.size() !=
session->quic_early_data_context.size() ||
CRYPTO_memcmp(config->quic_early_data_context.data(),
session->quic_early_data_context.data(),
session->quic_early_data_context.size()) != 0) {
return false;
}
return true;
}
static enum ssl_hs_wait_t do_select_session(SSL_HANDSHAKE *hs) {
SSL *const ssl = hs->ssl;
SSLMessage msg;
if (!ssl->method->get_message(ssl, &msg)) {
return ssl_hs_read_message;
}
SSL_CLIENT_HELLO client_hello;
if (!ssl_client_hello_init(ssl, &client_hello, msg)) {
OPENSSL_PUT_ERROR(SSL, SSL_R_CLIENTHELLO_PARSE_FAILED);
ssl_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
return ssl_hs_error;
}
uint8_t alert = SSL_AD_DECODE_ERROR;
UniquePtr<SSL_SESSION> session;
bool offered_ticket = false;
switch (select_session(hs, &alert, &session, &ssl->s3->ticket_age_skew,
&offered_ticket, msg, &client_hello)) {
case ssl_ticket_aead_ignore_ticket:
assert(!session);
if (!ssl_get_new_session(hs, 1 /* server */)) {
ssl_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
return ssl_hs_error;
}
break;
case ssl_ticket_aead_success:
// Carry over authentication information from the previous handshake into
// a fresh session.
hs->new_session =
SSL_SESSION_dup(session.get(), SSL_SESSION_DUP_AUTH_ONLY);
if (hs->new_session == nullptr) {
ssl_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
return ssl_hs_error;
}
ssl->s3->session_reused = true;
// Resumption incorporates fresh key material, so refresh the timeout.
ssl_session_renew_timeout(ssl, hs->new_session.get(),
ssl->session_ctx->session_psk_dhe_timeout);
break;
case ssl_ticket_aead_error:
ssl_send_alert(ssl, SSL3_AL_FATAL, alert);
return ssl_hs_error;
case ssl_ticket_aead_retry:
hs->tls13_state = state13_select_session;
return ssl_hs_pending_ticket;
}
// Negotiate ALPS now, after ALPN is negotiated and |hs->new_session| is
// initialized.
if (!ssl_negotiate_alps(hs, &alert, &client_hello)) {
ssl_send_alert(ssl, SSL3_AL_FATAL, alert);
return ssl_hs_error;
}
// Determine if we're negotiating 0-RTT.
if (!ssl->enable_early_data) {
ssl->s3->early_data_reason = ssl_early_data_disabled;
} else if (!offered_ticket) {
ssl->s3->early_data_reason = ssl_early_data_no_session_offered;
} else if (!session) {
ssl->s3->early_data_reason = ssl_early_data_session_not_resumed;
} else if (session->ticket_max_early_data == 0) {
ssl->s3->early_data_reason = ssl_early_data_unsupported_for_session;
} else if (!hs->early_data_offered) {
ssl->s3->early_data_reason = ssl_early_data_peer_declined;
} else if (ssl->s3->channel_id_valid) {
// Channel ID is incompatible with 0-RTT.
ssl->s3->early_data_reason = ssl_early_data_channel_id;
} else if (ssl->s3->token_binding_negotiated) {
// Token Binding is incompatible with 0-RTT.
ssl->s3->early_data_reason = ssl_early_data_token_binding;
} else if (MakeConstSpan(ssl->s3->alpn_selected) != session->early_alpn) {
// The negotiated ALPN must match the one in the ticket.
ssl->s3->early_data_reason = ssl_early_data_alpn_mismatch;
} else if (hs->new_session->has_application_settings !=
session->has_application_settings ||
MakeConstSpan(hs->new_session->local_application_settings) !=
session->local_application_settings) {
ssl->s3->early_data_reason = ssl_early_data_alps_mismatch;
} else if (ssl->s3->ticket_age_skew < -kMaxTicketAgeSkewSeconds ||
kMaxTicketAgeSkewSeconds < ssl->s3->ticket_age_skew) {
ssl->s3->early_data_reason = ssl_early_data_ticket_age_skew;
} else if (!quic_ticket_compatible(session.get(), hs->config)) {
ssl->s3->early_data_reason = ssl_early_data_quic_parameter_mismatch;
} else {
// |ssl_session_is_resumable| forbids cross-cipher resumptions even if the
// PRF hashes match.
assert(hs->new_cipher == session->cipher);
ssl->s3->early_data_reason = ssl_early_data_accepted;
ssl->s3->early_data_accepted = true;
}
// Record connection properties in the new session.
hs->new_session->cipher = hs->new_cipher;
// Store the ALPN and ALPS values in the session for 0-RTT. Note the peer
// applications settings are not generally known until client
// EncryptedExtensions.
if (!hs->new_session->early_alpn.CopyFrom(ssl->s3->alpn_selected)) {
ssl_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
return ssl_hs_error;
}
// The peer applications settings are usually received later, in
// EncryptedExtensions. But, in 0-RTT handshakes, we carry over the
// values from |session|. Do this now, before |session| is discarded.
if (ssl->s3->early_data_accepted &&
hs->new_session->has_application_settings &&
!hs->new_session->peer_application_settings.CopyFrom(
session->peer_application_settings)) {
ssl_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
return ssl_hs_error;
}
// Copy the QUIC early data context to the session.
if (ssl->enable_early_data && ssl->quic_method) {
if (!hs->new_session->quic_early_data_context.CopyFrom(
hs->config->quic_early_data_context)) {
ssl_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
return ssl_hs_error;
}
}
if (ssl->ctx->dos_protection_cb != NULL &&
ssl->ctx->dos_protection_cb(&client_hello) == 0) {
// Connection rejected for DOS reasons.
OPENSSL_PUT_ERROR(SSL, SSL_R_CONNECTION_REJECTED);
ssl_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
return ssl_hs_error;
}
size_t hash_len = EVP_MD_size(
ssl_get_handshake_digest(ssl_protocol_version(ssl), hs->new_cipher));
// Set up the key schedule and incorporate the PSK into the running secret.
if (ssl->s3->session_reused) {
if (!tls13_init_key_schedule(
hs, MakeConstSpan(hs->new_session->secret,
hs->new_session->secret_length))) {
return ssl_hs_error;
}
} else if (!tls13_init_key_schedule(hs, MakeConstSpan(kZeroes, hash_len))) {
return ssl_hs_error;
}
if (!ssl_hash_message(hs, msg)) {
return ssl_hs_error;
}
if (ssl->s3->early_data_accepted) {
if (!tls13_derive_early_secret(hs)) {
return ssl_hs_error;
}
} else if (hs->early_data_offered) {
ssl->s3->skip_early_data = true;
}
// Resolve ECDHE and incorporate it into the secret.
bool need_retry;
if (!resolve_ecdhe_secret(hs, &need_retry, &client_hello)) {
if (need_retry) {
if (ssl->s3->early_data_accepted) {
ssl->s3->early_data_reason = ssl_early_data_hello_retry_request;
ssl->s3->early_data_accepted = false;
}
ssl->s3->skip_early_data = true;
ssl->method->next_message(ssl);
if (!hs->transcript.UpdateForHelloRetryRequest()) {
return ssl_hs_error;
}
hs->tls13_state = state13_send_hello_retry_request;
return ssl_hs_ok;
}
return ssl_hs_error;
}
ssl->method->next_message(ssl);
hs->tls13_state = state13_send_server_hello;
return ssl_hs_ok;
}
static enum ssl_hs_wait_t do_send_hello_retry_request(SSL_HANDSHAKE *hs) {
SSL *const ssl = hs->ssl;
ScopedCBB cbb;
CBB body, session_id, extensions;
uint16_t group_id;
if (!ssl->method->init_message(ssl, cbb.get(), &body, SSL3_MT_SERVER_HELLO) ||
!CBB_add_u16(&body, TLS1_2_VERSION) ||
!CBB_add_bytes(&body, kHelloRetryRequest, SSL3_RANDOM_SIZE) ||
!CBB_add_u8_length_prefixed(&body, &session_id) ||
!CBB_add_bytes(&session_id, hs->session_id, hs->session_id_len) ||
!CBB_add_u16(&body, SSL_CIPHER_get_protocol_id(hs->new_cipher)) ||
!CBB_add_u8(&body, 0 /* no compression */) ||
!tls1_get_shared_group(hs, &group_id) ||
!CBB_add_u16_length_prefixed(&body, &extensions) ||
!CBB_add_u16(&extensions, TLSEXT_TYPE_supported_versions) ||
!CBB_add_u16(&extensions, 2 /* length */) ||
!CBB_add_u16(&extensions, ssl->version) ||
!CBB_add_u16(&extensions, TLSEXT_TYPE_key_share) ||
!CBB_add_u16(&extensions, 2 /* length */) ||
!CBB_add_u16(&extensions, group_id) ||
!ssl_add_message_cbb(ssl, cbb.get())) {
return ssl_hs_error;
}
if (!ssl->method->add_change_cipher_spec(ssl)) {
return ssl_hs_error;
}
ssl->s3->used_hello_retry_request = true;
hs->tls13_state = state13_read_second_client_hello;
return ssl_hs_flush;
}
static enum ssl_hs_wait_t do_read_second_client_hello(SSL_HANDSHAKE *hs) {
SSL *const ssl = hs->ssl;
SSLMessage msg;
if (!ssl->method->get_message(ssl, &msg)) {
return ssl_hs_read_message;
}
if (!ssl_check_message_type(ssl, msg, SSL3_MT_CLIENT_HELLO)) {
return ssl_hs_error;
}
SSL_CLIENT_HELLO client_hello;
if (!ssl_client_hello_init(ssl, &client_hello, msg)) {
OPENSSL_PUT_ERROR(SSL, SSL_R_CLIENTHELLO_PARSE_FAILED);
ssl_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
return ssl_hs_error;
}
// We perform all our negotiation based on the first ClientHello (for
// consistency with what |select_certificate_cb| observed), which is in the
// transcript, so we can ignore most of this second one.
//
// We do, however, check the second PSK binder. This covers the client key
// share, in case we ever send half-RTT data (we currently do not). It is also
// a tricky computation, so we enforce the peer handled it correctly.
if (ssl->s3->session_reused) {
CBS pre_shared_key;
if (!ssl_client_hello_get_extension(&client_hello, &pre_shared_key,
TLSEXT_TYPE_pre_shared_key)) {
OPENSSL_PUT_ERROR(SSL, SSL_R_INCONSISTENT_CLIENT_HELLO);
ssl_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
return ssl_hs_error;
}
CBS ticket, binders;
uint32_t client_ticket_age;
uint8_t alert = SSL_AD_DECODE_ERROR;
if (!ssl_ext_pre_shared_key_parse_clienthello(
hs, &ticket, &binders, &client_ticket_age, &alert, &client_hello,
&pre_shared_key)) {
ssl_send_alert(ssl, SSL3_AL_FATAL, alert);
return ssl_hs_error;
}
// Note it is important that we do not obtain a new |SSL_SESSION| from
// |ticket|. We have already selected parameters based on the first
// ClientHello (in the transcript) and must not switch partway through.
if (!tls13_verify_psk_binder(hs, hs->new_session.get(), msg, &binders)) {
ssl_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECRYPT_ERROR);
return ssl_hs_error;
}
}
bool need_retry;
if (!resolve_ecdhe_secret(hs, &need_retry, &client_hello)) {
if (need_retry) {
// Only send one HelloRetryRequest.
ssl_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
OPENSSL_PUT_ERROR(SSL, SSL_R_WRONG_CURVE);
}
return ssl_hs_error;
}
if (!ssl_hash_message(hs, msg)) {
return ssl_hs_error;
}
// ClientHello should be the end of the flight.
if (ssl->method->has_unprocessed_handshake_data(ssl)) {
ssl_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_UNEXPECTED_MESSAGE);
OPENSSL_PUT_ERROR(SSL, SSL_R_EXCESS_HANDSHAKE_DATA);
return ssl_hs_error;
}
ssl->method->next_message(ssl);
hs->tls13_state = state13_send_server_hello;
return ssl_hs_ok;
}
static enum ssl_hs_wait_t do_send_server_hello(SSL_HANDSHAKE *hs) {
SSL *const ssl = hs->ssl;
Span<uint8_t> random(ssl->s3->server_random);
RAND_bytes(random.data(), random.size());
// If the ClientHello has an ech_is_inner extension, we must be the ECH
// backend server. In response to ech_is_inner, we will overwrite part of the
// ServerHello.random with the ECH acceptance confirmation.
if (hs->ech_is_inner_present) {
// Construct the ServerHelloECHConf message, which is the same as
// ServerHello, except the last 8 bytes of its random field are zeroed out.
Span<uint8_t> random_suffix = random.subspan(24);
OPENSSL_memset(random_suffix.data(), 0, random_suffix.size());
ScopedCBB cbb;
CBB body, extensions, session_id;
if (!ssl->method->init_message(ssl, cbb.get(), &body,
SSL3_MT_SERVER_HELLO) ||
!CBB_add_u16(&body, TLS1_2_VERSION) ||
!CBB_add_bytes(&body, random.data(), random.size()) ||
!CBB_add_u8_length_prefixed(&body, &session_id) ||
!CBB_add_bytes(&session_id, hs->session_id, hs->session_id_len) ||
!CBB_add_u16(&body, SSL_CIPHER_get_protocol_id(hs->new_cipher)) ||
!CBB_add_u8(&body, 0) ||
!CBB_add_u16_length_prefixed(&body, &extensions) ||
!ssl_ext_pre_shared_key_add_serverhello(hs, &extensions) ||
!ssl_ext_key_share_add_serverhello(hs, &extensions, /*dry_run=*/true) ||
!ssl_ext_supported_versions_add_serverhello(hs, &extensions) ||
!CBB_flush(cbb.get())) {
return ssl_hs_error;
}
// Note that |cbb| includes the message type and length fields, but not the
// record layer header.
if (!tls13_ech_accept_confirmation(
hs, random_suffix,
bssl::MakeConstSpan(CBB_data(cbb.get()), CBB_len(cbb.get())))) {
return ssl_hs_error;
}
}
// Send a ServerHello.
ScopedCBB cbb;
CBB body, extensions, session_id;
if (!ssl->method->init_message(ssl, cbb.get(), &body, SSL3_MT_SERVER_HELLO) ||
!CBB_add_u16(&body, TLS1_2_VERSION) ||
!CBB_add_bytes(&body, random.data(), random.size()) ||
!CBB_add_u8_length_prefixed(&body, &session_id) ||
!CBB_add_bytes(&session_id, hs->session_id, hs->session_id_len) ||
!CBB_add_u16(&body, SSL_CIPHER_get_protocol_id(hs->new_cipher)) ||
!CBB_add_u8(&body, 0) ||
!CBB_add_u16_length_prefixed(&body, &extensions) ||
!ssl_ext_pre_shared_key_add_serverhello(hs, &extensions) ||
!ssl_ext_key_share_add_serverhello(hs, &extensions, /*dry_run=*/false) ||
!ssl_ext_supported_versions_add_serverhello(hs, &extensions) ||
!ssl_add_message_cbb(ssl, cbb.get())) {
return ssl_hs_error;
}
if (!ssl->s3->used_hello_retry_request &&
!ssl->method->add_change_cipher_spec(ssl)) {
return ssl_hs_error;
}
// Derive and enable the handshake traffic secrets.
if (!tls13_derive_handshake_secrets(hs) ||
!tls13_set_traffic_key(ssl, ssl_encryption_handshake, evp_aead_seal,
hs->new_session.get(),
hs->server_handshake_secret())) {
return ssl_hs_error;
}
// Send EncryptedExtensions.
if (!ssl->method->init_message(ssl, cbb.get(), &body,
SSL3_MT_ENCRYPTED_EXTENSIONS) ||
!ssl_add_serverhello_tlsext(hs, &body) ||
!ssl_add_message_cbb(ssl, cbb.get())) {
return ssl_hs_error;
}
if (!ssl->s3->session_reused) {
// Determine whether to request a client certificate.
hs->cert_request = !!(hs->config->verify_mode & SSL_VERIFY_PEER);
// Only request a certificate if Channel ID isn't negotiated.
if ((hs->config->verify_mode & SSL_VERIFY_PEER_IF_NO_OBC) &&
ssl->s3->channel_id_valid) {
hs->cert_request = false;
}
}
// Send a CertificateRequest, if necessary.
if (hs->cert_request) {
CBB cert_request_extensions, sigalg_contents, sigalgs_cbb;
if (!ssl->method->init_message(ssl, cbb.get(), &body,
SSL3_MT_CERTIFICATE_REQUEST) ||
!CBB_add_u8(&body, 0 /* no certificate_request_context. */) ||
!CBB_add_u16_length_prefixed(&body, &cert_request_extensions) ||
!CBB_add_u16(&cert_request_extensions,
TLSEXT_TYPE_signature_algorithms) ||
!CBB_add_u16_length_prefixed(&cert_request_extensions,
&sigalg_contents) ||
!CBB_add_u16_length_prefixed(&sigalg_contents, &sigalgs_cbb) ||
!tls12_add_verify_sigalgs(hs, &sigalgs_cbb)) {
return ssl_hs_error;
}
if (ssl_has_client_CAs(hs->config)) {
CBB ca_contents;
if (!CBB_add_u16(&cert_request_extensions,
TLSEXT_TYPE_certificate_authorities) ||
!CBB_add_u16_length_prefixed(&cert_request_extensions,
&ca_contents) ||
!ssl_add_client_CA_list(hs, &ca_contents) ||
!CBB_flush(&cert_request_extensions)) {
return ssl_hs_error;
}
}
if (!ssl_add_message_cbb(ssl, cbb.get())) {
return ssl_hs_error;
}
}
// Send the server Certificate message, if necessary.
if (!ssl->s3->session_reused) {
if (!ssl_has_certificate(hs)) {
OPENSSL_PUT_ERROR(SSL, SSL_R_NO_CERTIFICATE_SET);
return ssl_hs_error;
}
if (!tls13_add_certificate(hs)) {
return ssl_hs_error;
}
hs->tls13_state = state13_send_server_certificate_verify;
return ssl_hs_ok;
}
hs->tls13_state = state13_send_server_finished;
return ssl_hs_ok;
}
static enum ssl_hs_wait_t do_send_server_certificate_verify(SSL_HANDSHAKE *hs) {
switch (tls13_add_certificate_verify(hs)) {
case ssl_private_key_success:
hs->tls13_state = state13_send_server_finished;
return ssl_hs_ok;
case ssl_private_key_retry:
hs->tls13_state = state13_send_server_certificate_verify;
return ssl_hs_private_key_operation;
case ssl_private_key_failure:
return ssl_hs_error;
}
assert(0);
return ssl_hs_error;
}
static enum ssl_hs_wait_t do_send_server_finished(SSL_HANDSHAKE *hs) {
SSL *const ssl = hs->ssl;
if (!tls13_add_finished(hs) ||
// Update the secret to the master secret and derive traffic keys.
!tls13_advance_key_schedule(
hs, MakeConstSpan(kZeroes, hs->transcript.DigestLen())) ||
!tls13_derive_application_secrets(hs) ||
!tls13_set_traffic_key(ssl, ssl_encryption_application, evp_aead_seal,
hs->new_session.get(),
hs->server_traffic_secret_0())) {
return ssl_hs_error;
}
hs->tls13_state = state13_send_half_rtt_ticket;
return hs->handback ? ssl_hs_handback : ssl_hs_ok;
}
static enum ssl_hs_wait_t do_send_half_rtt_ticket(SSL_HANDSHAKE *hs) {
SSL *const ssl = hs->ssl;
if (ssl->s3->early_data_accepted) {
// If accepting 0-RTT, we send tickets half-RTT. This gets the tickets on
// the wire sooner and also avoids triggering a write on |SSL_read| when
// processing the client Finished. This requires computing the client
// Finished early. See RFC 8446, section 4.6.1.
static const uint8_t kEndOfEarlyData[4] = {SSL3_MT_END_OF_EARLY_DATA, 0,
0, 0};
if (ssl->quic_method == nullptr &&
!hs->transcript.Update(kEndOfEarlyData)) {
OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
return ssl_hs_error;
}
size_t finished_len;
if (!tls13_finished_mac(hs, hs->expected_client_finished().data(),
&finished_len, false /* client */)) {
return ssl_hs_error;
}
if (finished_len != hs->expected_client_finished().size()) {
OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
return ssl_hs_error;
}
// Feed the predicted Finished into the transcript. This allows us to derive
// the resumption secret early and send half-RTT tickets.
//
// TODO(davidben): This will need to be updated for DTLS 1.3.
assert(!SSL_is_dtls(hs->ssl));
assert(hs->expected_client_finished().size() <= 0xff);
uint8_t header[4] = {
SSL3_MT_FINISHED, 0, 0,
static_cast<uint8_t>(hs->expected_client_finished().size())};
bool unused_sent_tickets;
if (!hs->transcript.Update(header) ||
!hs->transcript.Update(hs->expected_client_finished()) ||
!tls13_derive_resumption_secret(hs) ||
!add_new_session_tickets(hs, &unused_sent_tickets)) {
return ssl_hs_error;
}
}
hs->tls13_state = state13_read_second_client_flight;
return ssl_hs_flush;
}
static enum ssl_hs_wait_t do_read_second_client_flight(SSL_HANDSHAKE *hs) {
SSL *const ssl = hs->ssl;
if (ssl->s3->early_data_accepted) {
if (!tls13_set_traffic_key(ssl, ssl_encryption_early_data, evp_aead_open,
hs->new_session.get(),
hs->early_traffic_secret())) {
return ssl_hs_error;
}
hs->can_early_write = true;
hs->can_early_read = true;
hs->in_early_data = true;
}
// QUIC doesn't use an EndOfEarlyData message (draft-ietf-quic-tls-22,
// section 8.3), so we switch to client_handshake_secret before the early
// return.
if (ssl->quic_method != nullptr) {
if (!tls13_set_traffic_key(ssl, ssl_encryption_handshake, evp_aead_open,
hs->new_session.get(),
hs->client_handshake_secret())) {
return ssl_hs_error;
}
hs->tls13_state = state13_process_end_of_early_data;
return ssl->s3->early_data_accepted ? ssl_hs_early_return : ssl_hs_ok;
}
hs->tls13_state = state13_process_end_of_early_data;
return ssl->s3->early_data_accepted ? ssl_hs_read_end_of_early_data
: ssl_hs_ok;
}
static enum ssl_hs_wait_t do_process_end_of_early_data(SSL_HANDSHAKE *hs) {
SSL *const ssl = hs->ssl;
// In protocols that use EndOfEarlyData, we must consume the extra message and
// switch to client_handshake_secret after the early return.
if (ssl->quic_method == nullptr) {
// If early data was not accepted, the EndOfEarlyData will be in the
// discarded early data.
if (hs->ssl->s3->early_data_accepted) {
SSLMessage msg;
if (!ssl->method->get_message(ssl, &msg)) {
return ssl_hs_read_message;
}
if (!ssl_check_message_type(ssl, msg, SSL3_MT_END_OF_EARLY_DATA)) {
return ssl_hs_error;
}
if (CBS_len(&msg.body) != 0) {
ssl_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
OPENSSL_PUT_ERROR(SSL, SSL_R_DECODE_ERROR);
return ssl_hs_error;
}
ssl->method->next_message(ssl);
}
if (!tls13_set_traffic_key(ssl, ssl_encryption_handshake, evp_aead_open,
hs->new_session.get(),
hs->client_handshake_secret())) {
return ssl_hs_error;
}
}
hs->tls13_state = state13_read_client_encrypted_extensions;
return ssl_hs_ok;
}
static enum ssl_hs_wait_t do_read_client_encrypted_extensions(
SSL_HANDSHAKE *hs) {
SSL *const ssl = hs->ssl;
// For now, only one extension uses client EncryptedExtensions. This function
// may be generalized if others use it in the future.
if (hs->new_session->has_application_settings &&
!ssl->s3->early_data_accepted) {
SSLMessage msg;
if (!ssl->method->get_message(ssl, &msg)) {
return ssl_hs_read_message;
}
if (!ssl_check_message_type(ssl, msg, SSL3_MT_ENCRYPTED_EXTENSIONS)) {
return ssl_hs_error;
}
CBS body = msg.body, extensions;
if (!CBS_get_u16_length_prefixed(&body, &extensions) ||
CBS_len(&body) != 0) {
OPENSSL_PUT_ERROR(SSL, SSL_R_DECODE_ERROR);
ssl_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
return ssl_hs_error;
}
// Parse out the extensions.
bool have_application_settings = false;
CBS application_settings;
SSL_EXTENSION_TYPE ext_types[] = {{TLSEXT_TYPE_application_settings,
&have_application_settings,
&application_settings}};
uint8_t alert = SSL_AD_DECODE_ERROR;
if (!ssl_parse_extensions(&extensions, &alert, ext_types,
/*ignore_unknown=*/false)) {
ssl_send_alert(ssl, SSL3_AL_FATAL, alert);
return ssl_hs_error;
}
if (!have_application_settings) {
OPENSSL_PUT_ERROR(SSL, SSL_R_MISSING_EXTENSION);
ssl_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_MISSING_EXTENSION);
return ssl_hs_error;
}
// Note that, if 0-RTT was accepted, these values will already have been
// initialized earlier.
if (!hs->new_session->peer_application_settings.CopyFrom(
application_settings) ||
!ssl_hash_message(hs, msg)) {
ssl_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
return ssl_hs_error;
}
ssl->method->next_message(ssl);
}
hs->tls13_state = state13_read_client_certificate;
return ssl_hs_ok;
}
static enum ssl_hs_wait_t do_read_client_certificate(SSL_HANDSHAKE *hs) {
SSL *const ssl = hs->ssl;
if (!hs->cert_request) {
if (!ssl->s3->session_reused) {
// OpenSSL returns X509_V_OK when no certificates are requested. This is
// classed by them as a bug, but it's assumed by at least NGINX. (Only do
// this in full handshakes as resumptions should carry over the previous
// |verify_result|, though this is a no-op because servers do not
// implement the client's odd soft-fail mode.)
hs->new_session->verify_result = X509_V_OK;
}
// Skip this state.
hs->tls13_state = state13_read_channel_id;
return ssl_hs_ok;
}
const bool allow_anonymous =
(hs->config->verify_mode & SSL_VERIFY_FAIL_IF_NO_PEER_CERT) == 0;
SSLMessage msg;
if (!ssl->method->get_message(ssl, &msg)) {
return ssl_hs_read_message;
}
if (!ssl_check_message_type(ssl, msg, SSL3_MT_CERTIFICATE) ||
!tls13_process_certificate(hs, msg, allow_anonymous) ||
!ssl_hash_message(hs, msg)) {
return ssl_hs_error;
}
ssl->method->next_message(ssl);
hs->tls13_state = state13_read_client_certificate_verify;
return ssl_hs_ok;
}
static enum ssl_hs_wait_t do_read_client_certificate_verify(SSL_HANDSHAKE *hs) {
SSL *const ssl = hs->ssl;
if (sk_CRYPTO_BUFFER_num(hs->new_session->certs.get()) == 0) {
// Skip this state.
hs->tls13_state = state13_read_channel_id;
return ssl_hs_ok;
}
SSLMessage msg;
if (!ssl->method->get_message(ssl, &msg)) {
return ssl_hs_read_message;
}
switch (ssl_verify_peer_cert(hs)) {
case ssl_verify_ok:
break;
case ssl_verify_invalid:
return ssl_hs_error;
case ssl_verify_retry:
hs->tls13_state = state13_read_client_certificate_verify;
return ssl_hs_certificate_verify;
}
if (!ssl_check_message_type(ssl, msg, SSL3_MT_CERTIFICATE_VERIFY) ||
!tls13_process_certificate_verify(hs, msg) ||
!ssl_hash_message(hs, msg)) {
return ssl_hs_error;
}
ssl->method->next_message(ssl);
hs->tls13_state = state13_read_channel_id;
return ssl_hs_ok;
}
static enum ssl_hs_wait_t do_read_channel_id(SSL_HANDSHAKE *hs) {
SSL *const ssl = hs->ssl;
if (!ssl->s3->channel_id_valid) {
hs->tls13_state = state13_read_client_finished;
return ssl_hs_ok;
}
SSLMessage msg;
if (!ssl->method->get_message(ssl, &msg)) {
return ssl_hs_read_message;
}
if (!ssl_check_message_type(ssl, msg, SSL3_MT_CHANNEL_ID) ||
!tls1_verify_channel_id(hs, msg) ||
!ssl_hash_message(hs, msg)) {
return ssl_hs_error;
}
ssl->method->next_message(ssl);
hs->tls13_state = state13_read_client_finished;
return ssl_hs_ok;
}
static enum ssl_hs_wait_t do_read_client_finished(SSL_HANDSHAKE *hs) {
SSL *const ssl = hs->ssl;
SSLMessage msg;
if (!ssl->method->get_message(ssl, &msg)) {
return ssl_hs_read_message;
}
if (!ssl_check_message_type(ssl, msg, SSL3_MT_FINISHED) ||
// If early data was accepted, we've already computed the client Finished
// and derived the resumption secret.
!tls13_process_finished(hs, msg, ssl->s3->early_data_accepted) ||
// evp_aead_seal keys have already been switched.
!tls13_set_traffic_key(ssl, ssl_encryption_application, evp_aead_open,
hs->new_session.get(),
hs->client_traffic_secret_0())) {
return ssl_hs_error;
}
if (!ssl->s3->early_data_accepted) {
if (!ssl_hash_message(hs, msg) ||
!tls13_derive_resumption_secret(hs)) {
return ssl_hs_error;
}
// We send post-handshake tickets as part of the handshake in 1-RTT.
hs->tls13_state = state13_send_new_session_ticket;
} else {
// We already sent half-RTT tickets.
hs->tls13_state = state13_done;
}
ssl->method->next_message(ssl);
return ssl_hs_ok;
}
static enum ssl_hs_wait_t do_send_new_session_ticket(SSL_HANDSHAKE *hs) {
bool sent_tickets;
if (!add_new_session_tickets(hs, &sent_tickets)) {
return ssl_hs_error;
}
hs->tls13_state = state13_done;
// In TLS 1.3, the NewSessionTicket isn't flushed until the server performs a
// write, to prevent a non-reading client from causing the server to hang in
// the case of a small server write buffer. Consumers which don't write data
// to the client will need to do a zero-byte write if they wish to flush the
// tickets.
if (hs->ssl->quic_method != nullptr && sent_tickets) {
return ssl_hs_flush;
}
return ssl_hs_ok;
}
enum ssl_hs_wait_t tls13_server_handshake(SSL_HANDSHAKE *hs) {
while (hs->tls13_state != state13_done) {
enum ssl_hs_wait_t ret = ssl_hs_error;
enum tls13_server_hs_state_t state =
static_cast<enum tls13_server_hs_state_t>(hs->tls13_state);
switch (state) {
case state13_select_parameters:
ret = do_select_parameters(hs);
break;
case state13_select_session:
ret = do_select_session(hs);
break;
case state13_send_hello_retry_request:
ret = do_send_hello_retry_request(hs);
break;
case state13_read_second_client_hello:
ret = do_read_second_client_hello(hs);
break;
case state13_send_server_hello:
ret = do_send_server_hello(hs);
break;
case state13_send_server_certificate_verify:
ret = do_send_server_certificate_verify(hs);
break;
case state13_send_server_finished:
ret = do_send_server_finished(hs);
break;
case state13_send_half_rtt_ticket:
ret = do_send_half_rtt_ticket(hs);
break;
case state13_read_second_client_flight:
ret = do_read_second_client_flight(hs);
break;
case state13_process_end_of_early_data:
ret = do_process_end_of_early_data(hs);
break;
case state13_read_client_encrypted_extensions:
ret = do_read_client_encrypted_extensions(hs);
break;
case state13_read_client_certificate:
ret = do_read_client_certificate(hs);
break;
case state13_read_client_certificate_verify:
ret = do_read_client_certificate_verify(hs);
break;
case state13_read_channel_id:
ret = do_read_channel_id(hs);
break;
case state13_read_client_finished:
ret = do_read_client_finished(hs);
break;
case state13_send_new_session_ticket:
ret = do_send_new_session_ticket(hs);
break;
case state13_done:
ret = ssl_hs_ok;
break;
}
if (hs->tls13_state != state) {
ssl_do_info_callback(hs->ssl, SSL_CB_ACCEPT_LOOP, 1);
}
if (ret != ssl_hs_ok) {
return ret;
}
}
return ssl_hs_ok;
}
const char *tls13_server_handshake_state(SSL_HANDSHAKE *hs) {
enum tls13_server_hs_state_t state =
static_cast<enum tls13_server_hs_state_t>(hs->tls13_state);
switch (state) {
case state13_select_parameters:
return "TLS 1.3 server select_parameters";
case state13_select_session:
return "TLS 1.3 server select_session";
case state13_send_hello_retry_request:
return "TLS 1.3 server send_hello_retry_request";
case state13_read_second_client_hello:
return "TLS 1.3 server read_second_client_hello";
case state13_send_server_hello:
return "TLS 1.3 server send_server_hello";
case state13_send_server_certificate_verify:
return "TLS 1.3 server send_server_certificate_verify";
case state13_send_half_rtt_ticket:
return "TLS 1.3 server send_half_rtt_ticket";
case state13_send_server_finished:
return "TLS 1.3 server send_server_finished";
case state13_read_second_client_flight:
return "TLS 1.3 server read_second_client_flight";
case state13_process_end_of_early_data:
return "TLS 1.3 server process_end_of_early_data";
case state13_read_client_encrypted_extensions:
return "TLS 1.3 server read_client_encrypted_extensions";
case state13_read_client_certificate:
return "TLS 1.3 server read_client_certificate";
case state13_read_client_certificate_verify:
return "TLS 1.3 server read_client_certificate_verify";
case state13_read_channel_id:
return "TLS 1.3 server read_channel_id";
case state13_read_client_finished:
return "TLS 1.3 server read_client_finished";
case state13_send_new_session_ticket:
return "TLS 1.3 server send_new_session_ticket";
case state13_done:
return "TLS 1.3 server done";
}
return "TLS 1.3 server unknown";
}
BSSL_NAMESPACE_END