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Cleaned up tls1_prf and added comments.

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Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/8987)
This commit is contained in:
David Makepeace 2019-05-23 14:36:24 +10:00 committed by Shane Lontis
parent e70185883e
commit 0f52d9ed7e
1 changed files with 117 additions and 35 deletions
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152
crypto/kdf/tls1_prf.c
View file

@ -7,6 +7,44 @@
* https://www.openssl.org/source/license.html * 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))
*/
#include <stdio.h> #include <stdio.h>
#include <stdarg.h> #include <stdarg.h>
#include <string.h> #include <string.h>
@ -82,7 +120,7 @@ static int kdf_tls1_prf_ctrl(EVP_KDF_IMPL *impl, int cmd, va_list args)
if (impl->sec == NULL) if (impl->sec == NULL)
return 0; return 0;
impl->seclen = len; impl->seclen = len;
return 1; return 1;
case EVP_KDF_CTRL_RESET_TLS_SEED: case EVP_KDF_CTRL_RESET_TLS_SEED:
@ -168,25 +206,41 @@ const EVP_KDF tls1_prf_kdf_meth = {
kdf_tls1_prf_derive kdf_tls1_prf_derive
}; };
/*
* 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(const EVP_MD *md, static int tls1_prf_P_hash(const EVP_MD *md,
const unsigned char *sec, size_t sec_len, const unsigned char *sec, size_t sec_len,
const unsigned char *seed, size_t seed_len, const unsigned char *seed, size_t seed_len,
unsigned char *out, size_t olen) unsigned char *out, size_t olen)
{ {
int chunk; size_t chunk;
EVP_MAC_CTX *ctx = NULL, *ctx_tmp = NULL, *ctx_init = NULL; EVP_MAC_CTX *ctx = NULL, *ctx_Ai = NULL, *ctx_init = NULL;
unsigned char A1[EVP_MAX_MD_SIZE]; unsigned char Ai[EVP_MAX_MD_SIZE];
size_t A1_len; size_t Ai_len;
int ret = 0; int ret = 0;
chunk = EVP_MD_size(md);
if (!ossl_assert(chunk > 0))
goto err;
ctx = EVP_MAC_CTX_new_id(EVP_MAC_HMAC); ctx = EVP_MAC_CTX_new_id(EVP_MAC_HMAC);
ctx_tmp = EVP_MAC_CTX_new_id(EVP_MAC_HMAC); ctx_Ai = EVP_MAC_CTX_new_id(EVP_MAC_HMAC);
ctx_init = EVP_MAC_CTX_new_id(EVP_MAC_HMAC); ctx_init = EVP_MAC_CTX_new_id(EVP_MAC_HMAC);
if (ctx == NULL || ctx_tmp == NULL || ctx_init == NULL) if (ctx == NULL || ctx_Ai == NULL || ctx_init == NULL)
goto err; goto err;
if (EVP_MAC_ctrl(ctx_init, EVP_MAC_CTRL_SET_FLAGS, EVP_MD_CTX_FLAG_NON_FIPS_ALLOW) != 1) if (EVP_MAC_ctrl(ctx_init, EVP_MAC_CTRL_SET_FLAGS, EVP_MD_CTX_FLAG_NON_FIPS_ALLOW) != 1)
goto err; goto err;
@ -196,59 +250,85 @@ static int tls1_prf_P_hash(const EVP_MD *md,
goto err; goto err;
if (!EVP_MAC_init(ctx_init)) if (!EVP_MAC_init(ctx_init))
goto err; goto err;
if (!EVP_MAC_CTX_copy(ctx, ctx_init)) chunk = EVP_MAC_size(ctx_init);
if (chunk == 0)
goto err; goto err;
if (seed != NULL && !EVP_MAC_update(ctx, seed, seed_len)) /* A(0) = seed */
if (!EVP_MAC_CTX_copy(ctx_Ai, ctx_init))
goto err; goto err;
if (!EVP_MAC_final(ctx, A1, &A1_len)) if (seed != NULL && !EVP_MAC_update(ctx_Ai, seed, seed_len))
goto err; goto err;
for (;;) { for (;;) {
/* Reinit mac contexts */ /* calc: A(i) = HMAC_<hash>(secret, A(i-1)) */
if (!EVP_MAC_final(ctx_Ai, Ai, &Ai_len))
goto err;
/* calc next chunk: HMAC_<hash>(secret, A(i) + seed) */
if (!EVP_MAC_CTX_copy(ctx, ctx_init)) if (!EVP_MAC_CTX_copy(ctx, ctx_init))
goto err; goto err;
if (!EVP_MAC_update(ctx, A1, A1_len)) if (!EVP_MAC_update(ctx, Ai, Ai_len))
goto err; goto err;
if (olen > (size_t)chunk && !EVP_MAC_CTX_copy(ctx_tmp, ctx)) /* save state for calculating next A(i) value */
if (olen > chunk && !EVP_MAC_CTX_copy(ctx_Ai, ctx))
goto err; goto err;
if (seed != NULL && !EVP_MAC_update(ctx, seed, seed_len)) if (seed != NULL && !EVP_MAC_update(ctx, seed, seed_len))
goto err; goto err;
if (olen <= chunk) {
if (olen > (size_t)chunk) { /* last chunk - use Ai as temp bounce buffer */
size_t mac_len; if (!EVP_MAC_final(ctx, Ai, &Ai_len))
if (!EVP_MAC_final(ctx, out, &mac_len))
goto err; goto err;
out += mac_len; memcpy(out, Ai, olen);
olen -= mac_len;
/* calc the next A1 value */
if (!EVP_MAC_final(ctx_tmp, A1, &A1_len))
goto err;
} else { /* last one */
if (!EVP_MAC_final(ctx, A1, &A1_len))
goto err;
memcpy(out, A1, olen);
break; break;
} }
if (!EVP_MAC_final(ctx, out, NULL))
goto err;
out += chunk;
olen -= chunk;
} }
ret = 1; ret = 1;
err: err:
EVP_MAC_CTX_free(ctx); EVP_MAC_CTX_free(ctx);
EVP_MAC_CTX_free(ctx_tmp); EVP_MAC_CTX_free(ctx_Ai);
EVP_MAC_CTX_free(ctx_init); EVP_MAC_CTX_free(ctx_init);
OPENSSL_cleanse(A1, sizeof(A1)); OPENSSL_cleanse(Ai, sizeof(Ai));
return ret; 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(const EVP_MD *md, static int tls1_prf_alg(const EVP_MD *md,
const unsigned char *sec, size_t slen, const unsigned char *sec, size_t slen,
const unsigned char *seed, size_t seed_len, const unsigned char *seed, size_t seed_len,
unsigned char *out, size_t olen) unsigned char *out, size_t olen)
{ {
if (EVP_MD_type(md) == NID_md5_sha1) { if (EVP_MD_type(md) == NID_md5_sha1) {
/* TLS v1.0 and TLS v1.1 */
size_t i; size_t i;
unsigned char *tmp; unsigned char *tmp;
if (!tls1_prf_P_hash(EVP_md5(), sec, slen/2 + (slen & 1), /* 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(EVP_md5(), sec, L_S1,
seed, seed_len, out, olen)) seed, seed_len, out, olen))
return 0; return 0;
@ -256,7 +336,7 @@ static int tls1_prf_alg(const EVP_MD *md,
KDFerr(KDF_F_TLS1_PRF_ALG, ERR_R_MALLOC_FAILURE); KDFerr(KDF_F_TLS1_PRF_ALG, ERR_R_MALLOC_FAILURE);
return 0; return 0;
} }
if (!tls1_prf_P_hash(EVP_sha1(), sec + slen/2, slen/2 + (slen & 1), if (!tls1_prf_P_hash(EVP_sha1(), sec + slen - L_S2, L_S2,
seed, seed_len, tmp, olen)) { seed, seed_len, tmp, olen)) {
OPENSSL_clear_free(tmp, olen); OPENSSL_clear_free(tmp, olen);
return 0; return 0;
@ -266,6 +346,8 @@ static int tls1_prf_alg(const EVP_MD *md,
OPENSSL_clear_free(tmp, olen); OPENSSL_clear_free(tmp, olen);
return 1; return 1;
} }
/* TLS v1.2 */
if (!tls1_prf_P_hash(md, sec, slen, seed, seed_len, out, olen)) if (!tls1_prf_P_hash(md, sec, slen, seed, seed_len, out, olen))
return 0; return 0;