blob: 88fe8f07bacb9a068a0a2927c0662d4f1d4a7fec [file] [log] [blame]
/* 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 <openssl/aead.h>
#include <openssl/bytestring.h>
#include <openssl/digest.h>
#include <openssl/hmac.h>
#include <openssl/hkdf.h>
#include <openssl/mem.h>
#include "internal.h"
int tls13_init_key_schedule(SSL *ssl, const uint8_t *resumption_ctx,
size_t resumption_ctx_len) {
SSL_HANDSHAKE *hs = ssl->s3->hs;
const EVP_MD *digest = ssl_get_handshake_digest(ssl_get_algorithm_prf(ssl));
hs->hash_len = EVP_MD_size(digest);
/* Save the hash of the resumption context. */
unsigned resumption_hash_len;
if (!EVP_Digest(resumption_ctx, resumption_ctx_len, hs->resumption_hash,
&resumption_hash_len, digest, NULL)) {
return 0;
}
/* Initialize the secret to the zero key. */
memset(hs->secret, 0, hs->hash_len);
/* Initialize the rolling hashes and release the handshake buffer. */
if (!ssl3_init_handshake_hash(ssl)) {
return 0;
}
ssl3_free_handshake_buffer(ssl);
return 1;
}
int tls13_advance_key_schedule(SSL *ssl, const uint8_t *in, size_t len) {
SSL_HANDSHAKE *hs = ssl->s3->hs;
const EVP_MD *digest = ssl_get_handshake_digest(ssl_get_algorithm_prf(ssl));
return HKDF_extract(hs->secret, &hs->hash_len, digest, in, len, hs->secret,
hs->hash_len);
}
static int hkdf_expand_label(uint8_t *out, const EVP_MD *digest,
const uint8_t *secret, size_t secret_len,
const uint8_t *label, size_t label_len,
const uint8_t *hash, size_t hash_len, size_t len) {
static const char kTLS13LabelVersion[] = "TLS 1.3, ";
CBB cbb, child;
uint8_t *hkdf_label;
size_t hkdf_label_len;
if (!CBB_init(&cbb, 2 + 1 + strlen(kTLS13LabelVersion) + label_len + 1 +
hash_len) ||
!CBB_add_u16(&cbb, len) ||
!CBB_add_u8_length_prefixed(&cbb, &child) ||
!CBB_add_bytes(&child, (const uint8_t *)kTLS13LabelVersion,
strlen(kTLS13LabelVersion)) ||
!CBB_add_bytes(&child, label, label_len) ||
!CBB_add_u8_length_prefixed(&cbb, &child) ||
!CBB_add_bytes(&child, hash, hash_len) ||
!CBB_finish(&cbb, &hkdf_label, &hkdf_label_len)) {
CBB_cleanup(&cbb);
return 0;
}
int ret = HKDF_expand(out, len, digest, secret, secret_len, hkdf_label,
hkdf_label_len);
OPENSSL_free(hkdf_label);
return ret;
}
int tls13_get_context_hashes(SSL *ssl, uint8_t *out, size_t *out_len) {
SSL_HANDSHAKE *hs = ssl->s3->hs;
EVP_MD_CTX ctx;
EVP_MD_CTX_init(&ctx);
unsigned handshake_len = 0;
int ok = EVP_MD_CTX_copy_ex(&ctx, &ssl->s3->handshake_hash) &&
EVP_DigestFinal_ex(&ctx, out, &handshake_len);
EVP_MD_CTX_cleanup(&ctx);
if (!ok) {
return 0;
}
memcpy(out + handshake_len, hs->resumption_hash, hs->hash_len);
*out_len = handshake_len + hs->hash_len;
return 1;
}
/* derive_secret derives a secret of length |len| and writes the result in |out|
* with the given label and the current base secret and most recently-saved
* handshake context. It returns one on success and zero on error. */
static int derive_secret(SSL *ssl, uint8_t *out, size_t len,
const uint8_t *label, size_t label_len) {
SSL_HANDSHAKE *hs = ssl->s3->hs;
const EVP_MD *digest = ssl_get_handshake_digest(ssl_get_algorithm_prf(ssl));
uint8_t context_hashes[2 * EVP_MAX_MD_SIZE];
size_t context_hashes_len;
if (!tls13_get_context_hashes(ssl, context_hashes, &context_hashes_len)) {
return 0;
}
return hkdf_expand_label(out, digest, hs->secret, hs->hash_len, label,
label_len, context_hashes, context_hashes_len, len);
}
int tls13_set_traffic_key(SSL *ssl, enum tls_record_type_t type,
enum evp_aead_direction_t direction,
const uint8_t *traffic_secret,
size_t traffic_secret_len) {
if (traffic_secret_len > 0xff) {
OPENSSL_PUT_ERROR(SSL, ERR_R_OVERFLOW);
return 0;
}
const char *phase;
switch (type) {
case type_early_handshake:
phase = "early handshake key expansion, ";
break;
case type_early_data:
phase = "early application data key expansion, ";
break;
case type_handshake:
phase = "handshake key expansion, ";
break;
case type_data:
phase = "application data key expansion, ";
break;
default:
return 0;
}
size_t phase_len = strlen(phase);
const char *purpose = "client write key";
if ((ssl->server && direction == evp_aead_seal) ||
(!ssl->server && direction == evp_aead_open)) {
purpose = "server write key";
}
size_t purpose_len = strlen(purpose);
/* The longest label has length 38 (type_early_data) + 16 (either purpose
* value). */
uint8_t label[38 + 16];
size_t label_len = phase_len + purpose_len;
if (label_len > sizeof(label)) {
assert(0);
return 0;
}
memcpy(label, phase, phase_len);
memcpy(label + phase_len, purpose, purpose_len);
/* Look up cipher suite properties. */
const EVP_AEAD *aead;
const EVP_MD *digest = ssl_get_handshake_digest(ssl_get_algorithm_prf(ssl));
size_t mac_secret_len, fixed_iv_len;
if (!ssl_cipher_get_evp_aead(&aead, &mac_secret_len, &fixed_iv_len,
SSL_get_session(ssl)->cipher,
ssl3_protocol_version(ssl))) {
return 0;
}
/* Derive the key. */
size_t key_len = EVP_AEAD_key_length(aead);
uint8_t key[EVP_AEAD_MAX_KEY_LENGTH];
if (!hkdf_expand_label(key, digest, traffic_secret, traffic_secret_len, label,
label_len, NULL, 0, key_len)) {
return 0;
}
/* The IV's label ends in "iv" instead of "key". */
if (label_len < 3) {
assert(0);
return 0;
}
label_len--;
label[label_len - 2] = 'i';
label[label_len - 1] = 'v';
/* Derive the IV. */
size_t iv_len = EVP_AEAD_nonce_length(aead);
uint8_t iv[EVP_AEAD_MAX_NONCE_LENGTH];
if (!hkdf_expand_label(iv, digest, traffic_secret, traffic_secret_len, label,
label_len, NULL, 0, iv_len)) {
return 0;
}
SSL_AEAD_CTX *traffic_aead = SSL_AEAD_CTX_new(
direction, ssl3_protocol_version(ssl), SSL_get_session(ssl)->cipher, key,
key_len, NULL, 0, iv, iv_len);
if (traffic_aead == NULL) {
return 0;
}
if (direction == evp_aead_open) {
if (!ssl->method->set_read_state(ssl, traffic_aead)) {
return 0;
}
} else {
if (!ssl->method->set_write_state(ssl, traffic_aead)) {
return 0;
}
}
/* Save the traffic secret. */
if (direction == evp_aead_open) {
memmove(ssl->s3->read_traffic_secret, traffic_secret, traffic_secret_len);
ssl->s3->read_traffic_secret_len = traffic_secret_len;
} else {
memmove(ssl->s3->write_traffic_secret, traffic_secret, traffic_secret_len);
ssl->s3->write_traffic_secret_len = traffic_secret_len;
}
return 1;
}
static const char kTLS13LabelHandshakeTraffic[] = "handshake traffic secret";
static const char kTLS13LabelApplicationTraffic[] =
"application traffic secret";
int tls13_set_handshake_traffic(SSL *ssl) {
SSL_HANDSHAKE *hs = ssl->s3->hs;
uint8_t traffic_secret[EVP_MAX_MD_SIZE];
if (!derive_secret(ssl, traffic_secret, hs->hash_len,
(const uint8_t *)kTLS13LabelHandshakeTraffic,
strlen(kTLS13LabelHandshakeTraffic)) ||
!ssl_log_secret(ssl, "HANDSHAKE_TRAFFIC_SECRET", traffic_secret,
hs->hash_len) ||
!tls13_set_traffic_key(ssl, type_handshake, evp_aead_open, traffic_secret,
hs->hash_len) ||
!tls13_set_traffic_key(ssl, type_handshake, evp_aead_seal, traffic_secret,
hs->hash_len)) {
return 0;
}
return 1;
}
int tls13_derive_traffic_secret_0(SSL *ssl) {
SSL_HANDSHAKE *hs = ssl->s3->hs;
return derive_secret(ssl, hs->traffic_secret_0, hs->hash_len,
(const uint8_t *)kTLS13LabelApplicationTraffic,
strlen(kTLS13LabelApplicationTraffic)) &&
ssl_log_secret(ssl, "TRAFFIC_SECRET_0", hs->traffic_secret_0,
hs->hash_len);
}
int tls13_rotate_traffic_key(SSL *ssl, enum evp_aead_direction_t direction) {
const EVP_MD *digest = ssl_get_handshake_digest(ssl_get_algorithm_prf(ssl));
uint8_t *secret;
size_t secret_len;
if (direction == evp_aead_open) {
secret = ssl->s3->read_traffic_secret;
secret_len = ssl->s3->read_traffic_secret_len;
} else {
secret = ssl->s3->write_traffic_secret;
secret_len = ssl->s3->write_traffic_secret_len;
}
if (!hkdf_expand_label(secret, digest, secret, secret_len,
(const uint8_t *)kTLS13LabelApplicationTraffic,
strlen(kTLS13LabelApplicationTraffic), NULL, 0,
secret_len)) {
return 0;
}
return tls13_set_traffic_key(ssl, type_data, direction, secret, secret_len);
}
static const char kTLS13LabelExporter[] = "exporter master secret";
static const char kTLS13LabelResumption[] = "resumption master secret";
int tls13_finalize_keys(SSL *ssl) {
SSL_HANDSHAKE *hs = ssl->s3->hs;
ssl->s3->exporter_secret_len = hs->hash_len;
ssl->s3->new_session->master_key_length = hs->hash_len;
if (!derive_secret(
ssl, ssl->s3->exporter_secret, ssl->s3->exporter_secret_len,
(const uint8_t *)kTLS13LabelExporter, strlen(kTLS13LabelExporter)) ||
!derive_secret(ssl, ssl->s3->new_session->master_key,
ssl->s3->new_session->master_key_length,
(const uint8_t *)kTLS13LabelResumption,
strlen(kTLS13LabelResumption))) {
return 0;
}
return 1;
}
int tls13_finished_mac(SSL *ssl, uint8_t *out, size_t *out_len, int is_server) {
SSL_HANDSHAKE *hs = ssl->s3->hs;
const EVP_MD *digest = ssl_get_handshake_digest(ssl_get_algorithm_prf(ssl));
uint8_t key[EVP_MAX_MD_SIZE];
size_t key_len = EVP_MD_size(digest);
const uint8_t *traffic_secret;
const char *label;
if (is_server) {
label = "server finished";
if (ssl->server) {
traffic_secret = ssl->s3->write_traffic_secret;
} else {
traffic_secret = ssl->s3->read_traffic_secret;
}
} else {
label = "client finished";
if (!ssl->server) {
traffic_secret = ssl->s3->write_traffic_secret;
} else {
traffic_secret = ssl->s3->read_traffic_secret;
}
}
uint8_t context_hashes[2 * EVP_MAX_MD_SIZE];
size_t context_hashes_len;
unsigned len;
if (!hkdf_expand_label(key, digest, traffic_secret, hs->hash_len,
(const uint8_t *)label, strlen(label), NULL, 0,
hs->hash_len) ||
!tls13_get_context_hashes(ssl, context_hashes, &context_hashes_len) ||
HMAC(digest, key, key_len, context_hashes, context_hashes_len, out,
&len) == NULL) {
return 0;
}
*out_len = len;
return 1;
}
static const char kTLS13LabelResumptionPSK[] = "resumption psk";
static const char kTLS13LabelResumptionContext[] = "resumption context";
int tls13_resumption_psk(SSL *ssl, uint8_t *out, size_t out_len,
const SSL_SESSION *session) {
const EVP_MD *digest = ssl_get_handshake_digest(ssl_get_algorithm_prf(ssl));
return hkdf_expand_label(out, digest, session->master_key,
session->master_key_length,
(const uint8_t *)kTLS13LabelResumptionPSK,
strlen(kTLS13LabelResumptionPSK), NULL, 0, out_len);
}
int tls13_resumption_context(SSL *ssl, uint8_t *out, size_t out_len,
const SSL_SESSION *session) {
const EVP_MD *digest = ssl_get_handshake_digest(ssl_get_algorithm_prf(ssl));
return hkdf_expand_label(out, digest, session->master_key,
session->master_key_length,
(const uint8_t *)kTLS13LabelResumptionContext,
strlen(kTLS13LabelResumptionContext), NULL, 0,
out_len);
}
int tls13_export_keying_material(SSL *ssl, uint8_t *out, size_t out_len,
const char *label, size_t label_len,
const uint8_t *context, size_t context_len,
int use_context) {
const EVP_MD *digest = ssl_get_handshake_digest(ssl_get_algorithm_prf(ssl));
const uint8_t *hash = NULL;
size_t hash_len = 0;
if (use_context) {
hash = context;
hash_len = context_len;
}
return hkdf_expand_label(out, digest, ssl->s3->exporter_secret,
ssl->s3->exporter_secret_len, (const uint8_t *)label,
label_len, hash, hash_len, out_len);
}