tls1_prf.c
/*
* Copyright 2016-2023 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the Apache License 2.0 (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
/*
* Refer to "The TLS Protocol Version 1.0" Section 5
* (https://tools.ietf.org/html/rfc2246#section-5) and
* "The Transport Layer Security (TLS) Protocol Version 1.2" Section 5
* (https://tools.ietf.org/html/rfc5246#section-5).
*
* For TLS v1.0 and TLS v1.1 the TLS PRF algorithm is given by:
*
* PRF(secret, label, seed) = P_MD5(S1, label + seed) XOR
* P_SHA-1(S2, label + seed)
*
* where P_MD5 and P_SHA-1 are defined by P_<hash>, below, and S1 and S2 are
* two halves of the secret (with the possibility of one shared byte, in the
* case where the length of the original secret is odd). S1 is taken from the
* first half of the secret, S2 from the second half.
*
* For TLS v1.2 the TLS PRF algorithm is given by:
*
* PRF(secret, label, seed) = P_<hash>(secret, label + seed)
*
* where hash is SHA-256 for all cipher suites defined in RFC 5246 as well as
* those published prior to TLS v1.2 while the TLS v1.2 protocol is in effect,
* unless defined otherwise by the cipher suite.
*
* P_<hash> is an expansion function that uses a single hash function to expand
* a secret and seed into an arbitrary quantity of output:
*
* P_<hash>(secret, seed) = HMAC_<hash>(secret, A(1) + seed) +
* HMAC_<hash>(secret, A(2) + seed) +
* HMAC_<hash>(secret, A(3) + seed) + ...
*
* where + indicates concatenation. P_<hash> can be iterated as many times as
* is necessary to produce the required quantity of data.
*
* A(i) is defined as:
* A(0) = seed
* A(i) = HMAC_<hash>(secret, A(i-1))
*/
/*
* Low level APIs (such as DH) are deprecated for public use, but still ok for
* internal use.
*/
#include "internal/deprecated.h"
#include <stdio.h>
#include <stdarg.h>
#include <string.h>
#include <openssl/evp.h>
#include <openssl/kdf.h>
#include <openssl/core_names.h>
#include <openssl/params.h>
#include <openssl/proverr.h>
#include "internal/cryptlib.h"
#include "internal/numbers.h"
#include "crypto/evp.h"
#include "prov/provider_ctx.h"
#include "prov/providercommon.h"
#include "prov/implementations.h"
#include "prov/provider_util.h"
#include "prov/securitycheck.h"
#include "internal/e_os.h"
static OSSL_FUNC_kdf_newctx_fn kdf_tls1_prf_new;
static OSSL_FUNC_kdf_dupctx_fn kdf_tls1_prf_dup;
static OSSL_FUNC_kdf_freectx_fn kdf_tls1_prf_free;
static OSSL_FUNC_kdf_reset_fn kdf_tls1_prf_reset;
static OSSL_FUNC_kdf_derive_fn kdf_tls1_prf_derive;
static OSSL_FUNC_kdf_settable_ctx_params_fn kdf_tls1_prf_settable_ctx_params;
static OSSL_FUNC_kdf_set_ctx_params_fn kdf_tls1_prf_set_ctx_params;
static OSSL_FUNC_kdf_gettable_ctx_params_fn kdf_tls1_prf_gettable_ctx_params;
static OSSL_FUNC_kdf_get_ctx_params_fn kdf_tls1_prf_get_ctx_params;
static int tls1_prf_alg(EVP_MAC_CTX *mdctx, EVP_MAC_CTX *sha1ctx,
const unsigned char *sec, size_t slen,
const unsigned char *seed, size_t seed_len,
unsigned char *out, size_t olen);
#define TLS1_PRF_MAXBUF 1024
#define TLS_MD_MASTER_SECRET_CONST "\x6d\x61\x73\x74\x65\x72\x20\x73\x65\x63\x72\x65\x74"
#define TLS_MD_MASTER_SECRET_CONST_SIZE 13
/* TLS KDF kdf context structure */
typedef struct {
void *provctx;
/* MAC context for the main digest */
EVP_MAC_CTX *P_hash;
/* MAC context for SHA1 for the MD5/SHA-1 combined PRF */
EVP_MAC_CTX *P_sha1;
/* Secret value to use for PRF */
unsigned char *sec;
size_t seclen;
/* Buffer of concatenated seed data */
unsigned char seed[TLS1_PRF_MAXBUF];
size_t seedlen;
} TLS1_PRF;
static void *kdf_tls1_prf_new(void *provctx)
{
TLS1_PRF *ctx;
if (!ossl_prov_is_running())
return NULL;
if ((ctx = OPENSSL_zalloc(sizeof(*ctx))) != NULL)
ctx->provctx = provctx;
return ctx;
}
static void kdf_tls1_prf_free(void *vctx)
{
TLS1_PRF *ctx = (TLS1_PRF *)vctx;
if (ctx != NULL) {
kdf_tls1_prf_reset(ctx);
OPENSSL_free(ctx);
}
}
static void kdf_tls1_prf_reset(void *vctx)
{
TLS1_PRF *ctx = (TLS1_PRF *)vctx;
void *provctx = ctx->provctx;
EVP_MAC_CTX_free(ctx->P_hash);
EVP_MAC_CTX_free(ctx->P_sha1);
OPENSSL_clear_free(ctx->sec, ctx->seclen);
OPENSSL_cleanse(ctx->seed, ctx->seedlen);
memset(ctx, 0, sizeof(*ctx));
ctx->provctx = provctx;
}
static void *kdf_tls1_prf_dup(void *vctx)
{
const TLS1_PRF *src = (const TLS1_PRF *)vctx;
TLS1_PRF *dest;
dest = kdf_tls1_prf_new(src->provctx);
if (dest != NULL) {
if (src->P_hash != NULL
&& (dest->P_hash = EVP_MAC_CTX_dup(src->P_hash)) == NULL)
goto err;
if (src->P_sha1 != NULL
&& (dest->P_sha1 = EVP_MAC_CTX_dup(src->P_sha1)) == NULL)
goto err;
if (!ossl_prov_memdup(src->sec, src->seclen, &dest->sec, &dest->seclen))
goto err;
memcpy(dest->seed, src->seed, src->seedlen);
dest->seedlen = src->seedlen;
}
return dest;
err:
kdf_tls1_prf_free(dest);
return NULL;
}
static int kdf_tls1_prf_derive(void *vctx, unsigned char *key, size_t keylen,
const OSSL_PARAM params[])
{
TLS1_PRF *ctx = (TLS1_PRF *)vctx;
OSSL_LIB_CTX *libctx = PROV_LIBCTX_OF(ctx->provctx);
if (!ossl_prov_is_running() || !kdf_tls1_prf_set_ctx_params(ctx, params))
return 0;
if (ctx->P_hash == NULL) {
ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);
return 0;
}
if (ctx->sec == NULL) {
ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_SECRET);
return 0;
}
if (ctx->seedlen == 0) {
ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_SEED);
return 0;
}
if (keylen == 0) {
ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_KEY_LENGTH);
return 0;
}
/*
* The seed buffer is prepended with a label.
* If EMS mode is enforced then the label "master secret" is not allowed,
* We do the check this way since the PRF is used for other purposes, as well
* as "extended master secret".
*/
if (ossl_tls1_prf_ems_check_enabled(libctx)) {
if (ctx->seedlen >= TLS_MD_MASTER_SECRET_CONST_SIZE
&& memcmp(ctx->seed, TLS_MD_MASTER_SECRET_CONST,
TLS_MD_MASTER_SECRET_CONST_SIZE) == 0) {
ERR_raise(ERR_LIB_PROV, PROV_R_EMS_NOT_ENABLED);
return 0;
}
}
return tls1_prf_alg(ctx->P_hash, ctx->P_sha1,
ctx->sec, ctx->seclen,
ctx->seed, ctx->seedlen,
key, keylen);
}
static int kdf_tls1_prf_set_ctx_params(void *vctx, const OSSL_PARAM params[])
{
const OSSL_PARAM *p;
TLS1_PRF *ctx = vctx;
OSSL_LIB_CTX *libctx = PROV_LIBCTX_OF(ctx->provctx);
if (params == NULL)
return 1;
if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_DIGEST)) != NULL) {
if (OPENSSL_strcasecmp(p->data, SN_md5_sha1) == 0) {
if (!ossl_prov_macctx_load_from_params(&ctx->P_hash, params,
OSSL_MAC_NAME_HMAC,
NULL, SN_md5, libctx)
|| !ossl_prov_macctx_load_from_params(&ctx->P_sha1, params,
OSSL_MAC_NAME_HMAC,
NULL, SN_sha1, libctx))
return 0;
} else {
EVP_MAC_CTX_free(ctx->P_sha1);
if (!ossl_prov_macctx_load_from_params(&ctx->P_hash, params,
OSSL_MAC_NAME_HMAC,
NULL, NULL, libctx))
return 0;
}
}
if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_SECRET)) != NULL) {
OPENSSL_clear_free(ctx->sec, ctx->seclen);
ctx->sec = NULL;
if (!OSSL_PARAM_get_octet_string(p, (void **)&ctx->sec, 0, &ctx->seclen))
return 0;
}
/* The seed fields concatenate, so process them all */
if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_SEED)) != NULL) {
for (; p != NULL; p = OSSL_PARAM_locate_const(p + 1,
OSSL_KDF_PARAM_SEED)) {
const void *q = ctx->seed + ctx->seedlen;
size_t sz = 0;
if (p->data_size != 0
&& p->data != NULL
&& !OSSL_PARAM_get_octet_string(p, (void **)&q,
TLS1_PRF_MAXBUF - ctx->seedlen,
&sz))
return 0;
ctx->seedlen += sz;
}
}
return 1;
}
static const OSSL_PARAM *kdf_tls1_prf_settable_ctx_params(
ossl_unused void *ctx, ossl_unused void *provctx)
{
static const OSSL_PARAM known_settable_ctx_params[] = {
OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_PROPERTIES, NULL, 0),
OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_DIGEST, NULL, 0),
OSSL_PARAM_octet_string(OSSL_KDF_PARAM_SECRET, NULL, 0),
OSSL_PARAM_octet_string(OSSL_KDF_PARAM_SEED, NULL, 0),
OSSL_PARAM_END
};
return known_settable_ctx_params;
}
static int kdf_tls1_prf_get_ctx_params(void *vctx, OSSL_PARAM params[])
{
OSSL_PARAM *p;
if ((p = OSSL_PARAM_locate(params, OSSL_KDF_PARAM_SIZE)) != NULL)
return OSSL_PARAM_set_size_t(p, SIZE_MAX);
return -2;
}
static const OSSL_PARAM *kdf_tls1_prf_gettable_ctx_params(
ossl_unused void *ctx, ossl_unused void *provctx)
{
static const OSSL_PARAM known_gettable_ctx_params[] = {
OSSL_PARAM_size_t(OSSL_KDF_PARAM_SIZE, NULL),
OSSL_PARAM_END
};
return known_gettable_ctx_params;
}
const OSSL_DISPATCH ossl_kdf_tls1_prf_functions[] = {
{ OSSL_FUNC_KDF_NEWCTX, (void(*)(void))kdf_tls1_prf_new },
{ OSSL_FUNC_KDF_DUPCTX, (void(*)(void))kdf_tls1_prf_dup },
{ OSSL_FUNC_KDF_FREECTX, (void(*)(void))kdf_tls1_prf_free },
{ OSSL_FUNC_KDF_RESET, (void(*)(void))kdf_tls1_prf_reset },
{ OSSL_FUNC_KDF_DERIVE, (void(*)(void))kdf_tls1_prf_derive },
{ OSSL_FUNC_KDF_SETTABLE_CTX_PARAMS,
(void(*)(void))kdf_tls1_prf_settable_ctx_params },
{ OSSL_FUNC_KDF_SET_CTX_PARAMS,
(void(*)(void))kdf_tls1_prf_set_ctx_params },
{ OSSL_FUNC_KDF_GETTABLE_CTX_PARAMS,
(void(*)(void))kdf_tls1_prf_gettable_ctx_params },
{ OSSL_FUNC_KDF_GET_CTX_PARAMS,
(void(*)(void))kdf_tls1_prf_get_ctx_params },
OSSL_DISPATCH_END
};
/*
* Refer to "The TLS Protocol Version 1.0" Section 5
* (https://tools.ietf.org/html/rfc2246#section-5) and
* "The Transport Layer Security (TLS) Protocol Version 1.2" Section 5
* (https://tools.ietf.org/html/rfc5246#section-5).
*
* P_<hash> is an expansion function that uses a single hash function to expand
* a secret and seed into an arbitrary quantity of output:
*
* P_<hash>(secret, seed) = HMAC_<hash>(secret, A(1) + seed) +
* HMAC_<hash>(secret, A(2) + seed) +
* HMAC_<hash>(secret, A(3) + seed) + ...
*
* where + indicates concatenation. P_<hash> can be iterated as many times as
* is necessary to produce the required quantity of data.
*
* A(i) is defined as:
* A(0) = seed
* A(i) = HMAC_<hash>(secret, A(i-1))
*/
static int tls1_prf_P_hash(EVP_MAC_CTX *ctx_init,
const unsigned char *sec, size_t sec_len,
const unsigned char *seed, size_t seed_len,
unsigned char *out, size_t olen)
{
size_t chunk;
EVP_MAC_CTX *ctx = NULL, *ctx_Ai = NULL;
unsigned char Ai[EVP_MAX_MD_SIZE];
size_t Ai_len;
int ret = 0;
if (!EVP_MAC_init(ctx_init, sec, sec_len, NULL))
goto err;
chunk = EVP_MAC_CTX_get_mac_size(ctx_init);
if (chunk == 0)
goto err;
/* A(0) = seed */
ctx_Ai = EVP_MAC_CTX_dup(ctx_init);
if (ctx_Ai == NULL)
goto err;
if (seed != NULL && !EVP_MAC_update(ctx_Ai, seed, seed_len))
goto err;
for (;;) {
/* calc: A(i) = HMAC_<hash>(secret, A(i-1)) */
if (!EVP_MAC_final(ctx_Ai, Ai, &Ai_len, sizeof(Ai)))
goto err;
EVP_MAC_CTX_free(ctx_Ai);
ctx_Ai = NULL;
/* calc next chunk: HMAC_<hash>(secret, A(i) + seed) */
ctx = EVP_MAC_CTX_dup(ctx_init);
if (ctx == NULL)
goto err;
if (!EVP_MAC_update(ctx, Ai, Ai_len))
goto err;
/* save state for calculating next A(i) value */
if (olen > chunk) {
ctx_Ai = EVP_MAC_CTX_dup(ctx);
if (ctx_Ai == NULL)
goto err;
}
if (seed != NULL && !EVP_MAC_update(ctx, seed, seed_len))
goto err;
if (olen <= chunk) {
/* last chunk - use Ai as temp bounce buffer */
if (!EVP_MAC_final(ctx, Ai, &Ai_len, sizeof(Ai)))
goto err;
memcpy(out, Ai, olen);
break;
}
if (!EVP_MAC_final(ctx, out, NULL, olen))
goto err;
EVP_MAC_CTX_free(ctx);
ctx = NULL;
out += chunk;
olen -= chunk;
}
ret = 1;
err:
EVP_MAC_CTX_free(ctx);
EVP_MAC_CTX_free(ctx_Ai);
OPENSSL_cleanse(Ai, sizeof(Ai));
return ret;
}
/*
* Refer to "The TLS Protocol Version 1.0" Section 5
* (https://tools.ietf.org/html/rfc2246#section-5) and
* "The Transport Layer Security (TLS) Protocol Version 1.2" Section 5
* (https://tools.ietf.org/html/rfc5246#section-5).
*
* For TLS v1.0 and TLS v1.1:
*
* PRF(secret, label, seed) = P_MD5(S1, label + seed) XOR
* P_SHA-1(S2, label + seed)
*
* S1 is taken from the first half of the secret, S2 from the second half.
*
* L_S = length in bytes of secret;
* L_S1 = L_S2 = ceil(L_S / 2);
*
* For TLS v1.2:
*
* PRF(secret, label, seed) = P_<hash>(secret, label + seed)
*/
static int tls1_prf_alg(EVP_MAC_CTX *mdctx, EVP_MAC_CTX *sha1ctx,
const unsigned char *sec, size_t slen,
const unsigned char *seed, size_t seed_len,
unsigned char *out, size_t olen)
{
if (sha1ctx != NULL) {
/* TLS v1.0 and TLS v1.1 */
size_t i;
unsigned char *tmp;
/* calc: L_S1 = L_S2 = ceil(L_S / 2) */
size_t L_S1 = (slen + 1) / 2;
size_t L_S2 = L_S1;
if (!tls1_prf_P_hash(mdctx, sec, L_S1,
seed, seed_len, out, olen))
return 0;
if ((tmp = OPENSSL_malloc(olen)) == NULL)
return 0;
if (!tls1_prf_P_hash(sha1ctx, sec + slen - L_S2, L_S2,
seed, seed_len, tmp, olen)) {
OPENSSL_clear_free(tmp, olen);
return 0;
}
for (i = 0; i < olen; i++)
out[i] ^= tmp[i];
OPENSSL_clear_free(tmp, olen);
return 1;
}
/* TLS v1.2 */
if (!tls1_prf_P_hash(mdctx, sec, slen, seed, seed_len, out, olen))
return 0;
return 1;
}
