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Added implementation of keying material export (RFC 5705) (API for PRF implementations changed, to handle chunked seeds).

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This commit is contained in:
Thomas Pornin 2017-07-04 20:43:39 +02:00
parent 2b738493bd
commit ea95d8264c
15 changed files with 256 additions and 77 deletions
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68
inc/bearssl_prf.h
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@ -50,11 +50,32 @@ extern "C" {
* rely on the SHA-256 based PRF, but some use SHA-384.
*
* The PRF always uses as input three parameters: a "secret" (some
* bytes), a "label" (ASCII string), and a "seed" (again some bytes).
* An arbitrary output length can be produced.
* bytes), a "label" (ASCII string), and a "seed" (again some bytes). An
* arbitrary output length can be produced. The "seed" is provided as an
* arbitrary number of binary chunks, that gets internally concatenated.
*/
/** \brief PRF implementation for TLS 1.0 and 1.1.
/**
* \brief Type for a seed chunk.
*
* Each chunk may have an arbitrary length, and may be empty (no byte at
* all). If the chunk length is zero, then the pointer to the chunk data
* may be `NULL`.
*/
typedef struct {
/**
* \brief Pointer to the chunk data.
*/
const void *data;
/**
* \brief Chunk length (in bytes).
*/
size_t len;
} br_tls_prf_seed_chunk;
/**
* \brief PRF implementation for TLS 1.0 and 1.1.
*
* This PRF is the one specified by TLS 1.0 and 1.1. It internally uses
* MD5 and SHA-1.
@ -64,14 +85,15 @@ extern "C" {
* \param secret secret value (key) for this computation.
* \param secret_len length of "secret" (in bytes).
* \param label PRF label (zero-terminated ASCII string).
* \param seed seed for this computation (usually non-secret).
* \param seed_len length of "seed" (in bytes).
* \param seed_num number of seed chunks.
* \param seed seed chnks for this computation (usually non-secret).
*/
void br_tls10_prf(void *dst, size_t len,
const void *secret, size_t secret_len,
const char *label, const void *seed, size_t seed_len);
const void *secret, size_t secret_len, const char *label,
size_t seed_num, const br_tls_prf_seed_chunk *seed);
/** \brief PRF implementation for TLS 1.2, with SHA-256.
/**
* \brief PRF implementation for TLS 1.2, with SHA-256.
*
* This PRF is the one specified by TLS 1.2, when the underlying hash
* function is SHA-256.
@ -81,14 +103,15 @@ void br_tls10_prf(void *dst, size_t len,
* \param secret secret value (key) for this computation.
* \param secret_len length of "secret" (in bytes).
* \param label PRF label (zero-terminated ASCII string).
* \param seed seed for this computation (usually non-secret).
* \param seed_len length of "seed" (in bytes).
* \param seed_num number of seed chunks.
* \param seed seed chnks for this computation (usually non-secret).
*/
void br_tls12_sha256_prf(void *dst, size_t len,
const void *secret, size_t secret_len,
const char *label, const void *seed, size_t seed_len);
const void *secret, size_t secret_len, const char *label,
size_t seed_num, const br_tls_prf_seed_chunk *seed);
/** \brief PRF implementation for TLS 1.2, with SHA-384.
/**
* \brief PRF implementation for TLS 1.2, with SHA-384.
*
* This PRF is the one specified by TLS 1.2, when the underlying hash
* function is SHA-384.
@ -98,26 +121,27 @@ void br_tls12_sha256_prf(void *dst, size_t len,
* \param secret secret value (key) for this computation.
* \param secret_len length of "secret" (in bytes).
* \param label PRF label (zero-terminated ASCII string).
* \param seed seed for this computation (usually non-secret).
* \param seed_len length of "seed" (in bytes).
* \param seed_num number of seed chunks.
* \param seed seed chnks for this computation (usually non-secret).
*/
void br_tls12_sha384_prf(void *dst, size_t len,
const void *secret, size_t secret_len,
const char *label, const void *seed, size_t seed_len);
const void *secret, size_t secret_len, const char *label,
size_t seed_num, const br_tls_prf_seed_chunk *seed);
/** \brief A convenient type name for a PRF implementation.
/**
* brief A convenient type name for a PRF implementation.
*
* \param dst destination buffer.
* \param len output length (in bytes).
* \param secret secret value (key) for this computation.
* \param secret_len length of "secret" (in bytes).
* \param label PRF label (zero-terminated ASCII string).
* \param seed seed for this computation (usually non-secret).
* \param seed_len length of "seed" (in bytes).
* \param seed_num number of seed chunks.
* \param seed seed chnks for this computation (usually non-secret).
*/
typedef void (*br_tls_prf_impl)(void *dst, size_t len,
const void *secret, size_t secret_len,
const char *label, const void *seed, size_t seed_len);
const void *secret, size_t secret_len, const char *label,
size_t seed_num, const br_tls_prf_seed_chunk *seed);
#ifdef __cplusplus
}

35
inc/bearssl_ssl.h
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@ -2075,6 +2075,41 @@ void br_ssl_engine_close(br_ssl_engine_context *cc);
*/
int br_ssl_engine_renegotiate(br_ssl_engine_context *cc);
/**
* \brief Export key material from a connected SSL engine (RFC 5705).
*
* This calls compute a secret key of arbitrary length from the master
* secret of a connected SSL engine. If the provided context is not
* currently in "application data" state (initial handshake is not
* finished, another handshake is ongoing, or the connection failed or
* was closed), then this function returns 0. Otherwise, a secret key of
* length `len` bytes is computed and written in the buffer pointed to
* by `dst`, and 1 is returned.
*
* The computed key follows the specification described in RFC 5705.
* That RFC includes two key computations, with and without a "context
* value". If `context` is `NULL`, then the variant without context is
* used; otherwise, the `context_len` bytes located at the address
* pointed to by `context` are used in the computation. Note that it
* is possible to have a "with context" key with a context length of
* zero bytes, by setting `context` to a non-`NULL` value but
* `context_len` to 0.
*
* When context bytes are used, the context length MUST NOT exceed
* 65535 bytes.
*
* \param cc SSL engine context.
* \param dst destination buffer for exported key.
* \param len exported key length (in bytes).
* \param label disambiguation label.
* \param context context value (or `NULL`).
* \param context_len context length (in bytes).
* \return 1 on success, 0 on error.
*/
int br_ssl_key_export(br_ssl_engine_context *cc,
void *dst, size_t len, const char *label,
const void *context, size_t context_len);
/*
* Pre-declaration for the SSL client context.
*/

5
mk/Rules.mk
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File diff suppressed because one or more lines are too long

1
mk/mkrules.sh
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@ -208,6 +208,7 @@ coresrc=" \
src/ssl/ssl_hs_client.c \
src/ssl/ssl_hs_server.c \
src/ssl/ssl_io.c \
src/ssl/ssl_keyexport.c \
src/ssl/ssl_lru.c \
src/ssl/ssl_rec_cbc.c \
src/ssl/ssl_rec_chapol.c \

4
src/inner.h
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@ -509,8 +509,8 @@ void br_sha2small_round(const unsigned char *buf, uint32_t *val);
*/
void br_tls_phash(void *dst, size_t len,
const br_hash_class *dig,
const void *secret, size_t secret_len,
const char *label, const void *seed, size_t seed_len);
const void *secret, size_t secret_len, const char *label,
size_t seed_num, const br_tls_prf_seed_chunk *seed);
/*
* Copy all configured hash implementations from a multihash context

16
src/ssl/prf.c
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@ -28,14 +28,14 @@
void
br_tls_phash(void *dst, size_t len,
const br_hash_class *dig,
const void *secret, size_t secret_len,
const char *label, const void *seed, size_t seed_len)
const void *secret, size_t secret_len, const char *label,
size_t seed_num, const br_tls_prf_seed_chunk *seed)
{
unsigned char *buf;
unsigned char tmp[64], a[64];
br_hmac_key_context kc;
br_hmac_context hc;
size_t label_len, hlen;
size_t label_len, hlen, u;
if (len == 0) {
return;
@ -46,15 +46,17 @@ br_tls_phash(void *dst, size_t len,
br_hmac_key_init(&kc, dig, secret, secret_len);
br_hmac_init(&hc, &kc, 0);
br_hmac_update(&hc, label, label_len);
br_hmac_update(&hc, seed, seed_len);
for (u = 0; u < seed_num; u ++) {
br_hmac_update(&hc, seed[u].data, seed[u].len);
}
br_hmac_out(&hc, a);
for (;;) {
size_t u;
br_hmac_init(&hc, &kc, 0);
br_hmac_update(&hc, a, hlen);
br_hmac_update(&hc, label, label_len);
br_hmac_update(&hc, seed, seed_len);
for (u = 0; u < seed_num; u ++) {
br_hmac_update(&hc, seed[u].data, seed[u].len);
}
br_hmac_out(&hc, tmp);
for (u = 0; u < hlen && u < len; u ++) {
buf[u] ^= tmp[u];

8
src/ssl/prf_md5sha1.c
View File

@ -27,8 +27,8 @@
/* see bearssl.h */
void
br_tls10_prf(void *dst, size_t len,
const void *secret, size_t secret_len,
const char *label, const void *seed, size_t seed_len)
const void *secret, size_t secret_len, const char *label,
size_t seed_num, const br_tls_prf_seed_chunk *seed)
{
const unsigned char *s1;
size_t slen;
@ -37,7 +37,7 @@ br_tls10_prf(void *dst, size_t len,
slen = (secret_len + 1) >> 1;
memset(dst, 0, len);
br_tls_phash(dst, len, &br_md5_vtable,
s1, slen, label, seed, seed_len);
s1, slen, label, seed_num, seed);
br_tls_phash(dst, len, &br_sha1_vtable,
s1 + secret_len - slen, slen, label, seed, seed_len);
s1 + secret_len - slen, slen, label, seed_num, seed);
}

6
src/ssl/prf_sha256.c
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@ -27,10 +27,10 @@
/* see bearssl.h */
void
br_tls12_sha256_prf(void *dst, size_t len,
const void *secret, size_t secret_len,
const char *label, const void *seed, size_t seed_len)
const void *secret, size_t secret_len, const char *label,
size_t seed_num, const br_tls_prf_seed_chunk *seed)
{
memset(dst, 0, len);
br_tls_phash(dst, len, &br_sha256_vtable,
secret, secret_len, label, seed, seed_len);
secret, secret_len, label, seed_num, seed);
}

6
src/ssl/prf_sha384.c
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@ -27,10 +27,10 @@
/* see bearssl.h */
void
br_tls12_sha384_prf(void *dst, size_t len,
const void *secret, size_t secret_len,
const char *label, const void *seed, size_t seed_len)
const void *secret, size_t secret_len, const char *label,
size_t seed_num, const br_tls_prf_seed_chunk *seed)
{
memset(dst, 0, len);
br_tls_phash(dst, len, &br_sha384_vtable,
secret, secret_len, label, seed, seed_len);
secret, secret_len, label, seed_num, seed);
}

18
src/ssl/ssl_engine.c
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@ -1335,13 +1335,14 @@ br_ssl_engine_compute_master(br_ssl_engine_context *cc,
int prf_id, const void *pms, size_t pms_len)
{
br_tls_prf_impl iprf;
unsigned char seed[64];
br_tls_prf_seed_chunk seed[2] = {
{ cc->client_random, sizeof cc->client_random },
{ cc->server_random, sizeof cc->server_random }
};
iprf = br_ssl_engine_get_PRF(cc, prf_id);
memcpy(seed, cc->client_random, 32);
memcpy(seed + 32, cc->server_random, 32);
iprf(cc->session.master_secret, sizeof cc->session.master_secret,
pms, pms_len, "master secret", seed, sizeof seed);
pms, pms_len, "master secret", 2, seed);
}
/*
@ -1352,14 +1353,15 @@ compute_key_block(br_ssl_engine_context *cc, int prf_id,
size_t half_len, unsigned char *kb)
{
br_tls_prf_impl iprf;
unsigned char seed[64];
br_tls_prf_seed_chunk seed[2] = {
{ cc->server_random, sizeof cc->server_random },
{ cc->client_random, sizeof cc->client_random }
};
iprf = br_ssl_engine_get_PRF(cc, prf_id);
memcpy(seed, cc->server_random, 32);
memcpy(seed + 32, cc->client_random, 32);
iprf(kb, half_len << 1,
cc->session.master_secret, sizeof cc->session.master_secret,
"key expansion", seed, sizeof seed);
"key expansion", 2, seed);
}
/* see inner.h */

15
src/ssl/ssl_hs_client.c
View File

@ -1192,21 +1192,22 @@ br_ssl_hs_client_run(void *t0ctx)
int prf_id = T0_POP();
int from_client = T0_POPi();
unsigned char seed[48];
size_t seed_len;
unsigned char tmp[48];
br_tls_prf_seed_chunk seed;
br_tls_prf_impl prf = br_ssl_engine_get_PRF(ENG, prf_id);
seed.data = tmp;
if (ENG->session.version >= BR_TLS12) {
seed_len = br_multihash_out(&ENG->mhash, prf_id, seed);
seed.len = br_multihash_out(&ENG->mhash, prf_id, tmp);
} else {
br_multihash_out(&ENG->mhash, br_md5_ID, seed);
br_multihash_out(&ENG->mhash, br_sha1_ID, seed + 16);
seed_len = 36;
br_multihash_out(&ENG->mhash, br_md5_ID, tmp);
br_multihash_out(&ENG->mhash, br_sha1_ID, tmp + 16);
seed.len = 36;
}
prf(ENG->pad, 12, ENG->session.master_secret,
sizeof ENG->session.master_secret,
from_client ? "client finished" : "server finished",
seed, seed_len);
1, &seed);
}
break;

19
src/ssl/ssl_hs_common.t0
View File

@ -754,6 +754,10 @@ cc: mkrand ( addr len -- ) {
\ -- PRF for TLS-1.2:
\ 4 with SHA-256
\ 5 with SHA-384
\
\ WARNING: if adding a new cipher suite that does not use SHA-256 for the
\ PRF (with TLS 1.2), be sure to check the suites_sha384[] array defined
\ in ssl/ssl_keyexport.c
data: cipher-suite-def
@ -1019,21 +1023,22 @@ cc: switch-chapol-in ( is_client prf_id -- ) {
cc: compute-Finished-inner ( from_client prf_id -- ) {
int prf_id = T0_POP();
int from_client = T0_POPi();
unsigned char seed[48];
size_t seed_len;
unsigned char tmp[48];
br_tls_prf_seed_chunk seed;
br_tls_prf_impl prf = br_ssl_engine_get_PRF(ENG, prf_id);
seed.data = tmp;
if (ENG->session.version >= BR_TLS12) {
seed_len = br_multihash_out(&ENG->mhash, prf_id, seed);
seed.len = br_multihash_out(&ENG->mhash, prf_id, tmp);
} else {
br_multihash_out(&ENG->mhash, br_md5_ID, seed);
br_multihash_out(&ENG->mhash, br_sha1_ID, seed + 16);
seed_len = 36;
br_multihash_out(&ENG->mhash, br_md5_ID, tmp);
br_multihash_out(&ENG->mhash, br_sha1_ID, tmp + 16);
seed.len = 36;
}
prf(ENG->pad, 12, ENG->session.master_secret,
sizeof ENG->session.master_secret,
from_client ? "client finished" : "server finished",
seed, seed_len);
1, &seed);
}
\ Receive ChangeCipherSpec and Finished from the peer.

15
src/ssl/ssl_hs_server.c
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@ -1250,21 +1250,22 @@ br_ssl_hs_server_run(void *t0ctx)
int prf_id = T0_POP();
int from_client = T0_POPi();
unsigned char seed[48];
size_t seed_len;
unsigned char tmp[48];
br_tls_prf_seed_chunk seed;
br_tls_prf_impl prf = br_ssl_engine_get_PRF(ENG, prf_id);
seed.data = tmp;
if (ENG->session.version >= BR_TLS12) {
seed_len = br_multihash_out(&ENG->mhash, prf_id, seed);
seed.len = br_multihash_out(&ENG->mhash, prf_id, tmp);
} else {
br_multihash_out(&ENG->mhash, br_md5_ID, seed);
br_multihash_out(&ENG->mhash, br_sha1_ID, seed + 16);
seed_len = 36;
br_multihash_out(&ENG->mhash, br_md5_ID, tmp);
br_multihash_out(&ENG->mhash, br_sha1_ID, tmp + 16);
seed.len = 36;
}
prf(ENG->pad, 12, ENG->session.master_secret,
sizeof ENG->session.master_secret,
from_client ? "client finished" : "server finished",
seed, seed_len);
1, &seed);
}
break;

83
src/ssl/ssl_keyexport.c Normal file
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@ -0,0 +1,83 @@
/*
* Copyright (c) 2017 Thomas Pornin <pornin@bolet.org>
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#include "inner.h"
/*
* Supported cipher suites that use SHA-384 for the PRF when selected
* for TLS 1.2. All other cipher suites are deemed to use SHA-256.
*/
static const uint16_t suites_sha384[] = {
BR_TLS_RSA_WITH_AES_256_GCM_SHA384,
BR_TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384,
BR_TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA384,
BR_TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384,
BR_TLS_ECDH_RSA_WITH_AES_256_CBC_SHA384,
BR_TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
BR_TLS_ECDH_ECDSA_WITH_AES_256_GCM_SHA384,
BR_TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
BR_TLS_ECDH_RSA_WITH_AES_256_GCM_SHA384
};
/* see bearssl_ssl.h */
int
br_ssl_key_export(br_ssl_engine_context *cc,
void *dst, size_t len, const char *label,
const void *context, size_t context_len)
{
br_tls_prf_seed_chunk chunks[4];
br_tls_prf_impl iprf;
size_t num_chunks, u;
unsigned char tmp[2];
int prf_id;
if (cc->application_data != 1) {
return 0;
}
chunks[0].data = cc->client_random;
chunks[0].len = sizeof cc->client_random;
chunks[1].data = cc->server_random;
chunks[1].len = sizeof cc->server_random;
if (context != NULL) {
br_enc16be(tmp, (unsigned)context_len);
chunks[2].data = tmp;
chunks[2].len = 2;
chunks[3].data = context;
chunks[3].len = context_len;
num_chunks = 4;
} else {
num_chunks = 2;
}
prf_id = BR_SSLPRF_SHA256;
for (u = 0; u < (sizeof suites_sha384) / sizeof(uint16_t); u ++) {
if (suites_sha384[u] == cc->session.cipher_suite) {
prf_id = BR_SSLPRF_SHA384;
}
}
iprf = br_ssl_engine_get_PRF(cc, prf_id);
iprf(dst, len,
cc->session.master_secret, sizeof cc->session.master_secret,
label, num_chunks, chunks);
return 1;
}

34
test/test_crypto.c
View File

@ -1075,21 +1075,43 @@ test_HMAC_DRBG(void)
}
static void
do_KAT_PRF(
void (*prf)(void *dst, size_t len,
const void *secret, size_t secret_len,
const char *label, const void *seed, size_t seed_len),
do_KAT_PRF(br_tls_prf_impl prf,
const char *ssecret, const char *label, const char *sseed,
const char *sref)
{
unsigned char secret[100], seed[100], ref[500], out[500];
size_t secret_len, seed_len, ref_len;
br_tls_prf_seed_chunk chunks[2];
secret_len = hextobin(secret, ssecret);
seed_len = hextobin(seed, sseed);
ref_len = hextobin(ref, sref);
prf(out, ref_len, secret, secret_len, label, seed, seed_len);
check_equals("TLS PRF KAT", out, ref, ref_len);
chunks[0].data = seed;
chunks[0].len = seed_len;
prf(out, ref_len, secret, secret_len, label, 1, chunks);
check_equals("TLS PRF KAT 1", out, ref, ref_len);
chunks[0].data = seed;
chunks[0].len = seed_len;
chunks[1].data = NULL;
chunks[1].len = 0;
prf(out, ref_len, secret, secret_len, label, 2, chunks);
check_equals("TLS PRF KAT 2", out, ref, ref_len);
chunks[0].data = NULL;
chunks[0].len = 0;
chunks[1].data = seed;
chunks[1].len = seed_len;
prf(out, ref_len, secret, secret_len, label, 2, chunks);
check_equals("TLS PRF KAT 3", out, ref, ref_len);
chunks[0].data = seed;
chunks[0].len = seed_len >> 1;
chunks[1].data = seed + chunks[0].len;
chunks[1].len = seed_len - chunks[0].len;
prf(out, ref_len, secret, secret_len, label, 2, chunks);
check_equals("TLS PRF KAT 4", out, ref, ref_len);
}
static void