Simplify handshake hash handling.
Rather than support arbitrarily many handshake hashes in the general
case (which the PRF logic assumes is capped at two), special-case the
MD5/SHA1 two-hash combination and otherwise maintain a single rolling
hash.
Change-Id: Ide9475565b158f6839bb10b8b22f324f89399f92
Reviewed-on: https://boringssl-review.googlesource.com/5618
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/ssl/t1_enc.c b/ssl/t1_enc.c
index febd54d..aa6095d 100644
--- a/ssl/t1_enc.c
+++ b/ssl/t1_enc.c
@@ -149,7 +149,7 @@
/* tls1_P_hash computes the TLS P_<hash> function as described in RFC 5246,
- * section 5. It writes |out_len| bytes to |out|, using |md| as the hash and
+ * section 5. It XORs |out_len| bytes to |out|, using |md| as the hash and
* |secret| as the secret. |seed1| through |seed3| are concatenated to form the
* seed parameter. It returns one on success and zero on failure. */
static int tls1_P_hash(uint8_t *out, size_t out_len, const EVP_MD *md,
@@ -188,26 +188,32 @@
goto err;
}
- if (out_len > chunk) {
- unsigned len;
- if (!HMAC_Final(&ctx, out, &len)) {
- goto err;
- }
- assert(len == chunk);
- out += len;
- out_len -= len;
- /* Calculate the next A1 value. */
- if (!HMAC_Final(&ctx_tmp, A1, &A1_len)) {
- goto err;
- }
- } else {
- /* Last chunk. */
- if (!HMAC_Final(&ctx, A1, &A1_len)) {
- goto err;
- }
- memcpy(out, A1, out_len);
+ unsigned len;
+ uint8_t hmac[EVP_MAX_MD_SIZE];
+ if (!HMAC_Final(&ctx, hmac, &len)) {
+ goto err;
+ }
+ assert(len == chunk);
+
+ /* XOR the result into |out|. */
+ if (len > out_len) {
+ len = out_len;
+ }
+ unsigned i;
+ for (i = 0; i < len; i++) {
+ out[i] ^= hmac[i];
+ }
+ out += len;
+ out_len -= len;
+
+ if (out_len == 0) {
break;
}
+
+ /* Calculate the next A1 value. */
+ if (!HMAC_Final(&ctx_tmp, A1, &A1_len)) {
+ goto err;
+ }
}
ret = 1;
@@ -224,62 +230,36 @@
size_t secret_len, const char *label, size_t label_len,
const uint8_t *seed1, size_t seed1_len,
const uint8_t *seed2, size_t seed2_len) {
- size_t idx, len, count, i;
- const uint8_t *S1;
- uint32_t m;
- const EVP_MD *md;
- int ret = 0;
- uint8_t *tmp;
if (out_len == 0) {
return 1;
}
- /* Allocate a temporary buffer. */
- tmp = OPENSSL_malloc(out_len);
- if (tmp == NULL) {
- OPENSSL_PUT_ERROR(SSL, ERR_R_MALLOC_FAILURE);
+ memset(out, 0, out_len);
+
+ uint32_t algorithm_prf = ssl_get_algorithm_prf(s);
+ if (algorithm_prf == SSL_HANDSHAKE_MAC_DEFAULT) {
+ /* If using the MD5/SHA1 PRF, |secret| is partitioned between SHA-1 and
+ * MD5, MD5 first. */
+ size_t secret_half = secret_len - (secret_len / 2);
+ if (!tls1_P_hash(out, out_len, EVP_md5(), secret, secret_half,
+ (const uint8_t *)label, label_len, seed1, seed1_len, seed2,
+ seed2_len)) {
+ return 0;
+ }
+
+ /* Note that, if |secret_len| is odd, the two halves share a byte. */
+ secret = secret + (secret_len - secret_half);
+ secret_len = secret_half;
+ }
+
+ if (!tls1_P_hash(out, out_len, ssl_get_handshake_digest(algorithm_prf),
+ secret, secret_len, (const uint8_t *)label, label_len,
+ seed1, seed1_len, seed2, seed2_len)) {
return 0;
}
- /* Count number of digests and partition |secret| evenly. */
- count = 0;
- for (idx = 0; ssl_get_handshake_digest(&m, &md, idx); idx++) {
- if (m & ssl_get_algorithm_prf(s)) {
- count++;
- }
- }
- /* TODO(davidben): The only case where count isn't 1 is the old MD5/SHA-1
- * combination. The logic around multiple handshake digests can probably be
- * simplified. */
- assert(count == 1 || count == 2);
- len = secret_len / count;
- if (count == 1) {
- secret_len = 0;
- }
- S1 = secret;
- memset(out, 0, out_len);
- for (idx = 0; ssl_get_handshake_digest(&m, &md, idx); idx++) {
- if (m & ssl_get_algorithm_prf(s)) {
- /* If |count| is 2 and |secret_len| is odd, |secret| is partitioned into
- * two halves with an overlapping byte. */
- if (!tls1_P_hash(tmp, out_len, md, S1, len + (secret_len & 1),
- (const uint8_t *)label, label_len, seed1, seed1_len,
- seed2, seed2_len)) {
- goto err;
- }
- S1 += len;
- for (i = 0; i < out_len; i++) {
- out[i] ^= tmp[i];
- }
- }
- }
- ret = 1;
-
-err:
- OPENSSL_cleanse(tmp, out_len);
- OPENSSL_free(tmp);
- return ret;
+ return 1;
}
static int tls1_generate_key_block(SSL *s, uint8_t *out, size_t out_len) {
@@ -469,31 +449,50 @@
}
int tls1_cert_verify_mac(SSL *s, int md_nid, uint8_t *out) {
- unsigned int ret;
- EVP_MD_CTX ctx, *d = NULL;
- int i;
-
- for (i = 0; i < SSL_MAX_DIGEST; i++) {
- if (s->s3->handshake_dgst[i] &&
- EVP_MD_CTX_type(s->s3->handshake_dgst[i]) == md_nid) {
- d = s->s3->handshake_dgst[i];
- break;
- }
- }
-
- if (!d) {
+ const EVP_MD_CTX *ctx_template;
+ if (md_nid == NID_md5) {
+ ctx_template = &s->s3->handshake_md5;
+ } else if (md_nid == EVP_MD_CTX_type(&s->s3->handshake_hash)) {
+ ctx_template = &s->s3->handshake_hash;
+ } else {
OPENSSL_PUT_ERROR(SSL, SSL_R_NO_REQUIRED_DIGEST);
return 0;
}
+ EVP_MD_CTX ctx;
EVP_MD_CTX_init(&ctx);
- if (!EVP_MD_CTX_copy_ex(&ctx, d)) {
+ if (!EVP_MD_CTX_copy_ex(&ctx, ctx_template)) {
EVP_MD_CTX_cleanup(&ctx);
return 0;
}
+ unsigned ret;
EVP_DigestFinal_ex(&ctx, out, &ret);
EVP_MD_CTX_cleanup(&ctx);
+ return ret;
+}
+static int append_digest(const EVP_MD_CTX *ctx, uint8_t *out, size_t *out_len,
+ size_t max_out) {
+ int ret = 0;
+ EVP_MD_CTX ctx_copy;
+ EVP_MD_CTX_init(&ctx_copy);
+
+ if (EVP_MD_CTX_size(ctx) > max_out) {
+ OPENSSL_PUT_ERROR(SSL, SSL_R_BUFFER_TOO_SMALL);
+ goto err;
+ }
+ unsigned len;
+ if (!EVP_MD_CTX_copy_ex(&ctx_copy, ctx) ||
+ !EVP_DigestFinal_ex(&ctx_copy, out, &len)) {
+ goto err;
+ }
+ assert(len == EVP_MD_CTX_size(ctx));
+
+ *out_len = len;
+ ret = 1;
+
+err:
+ EVP_MD_CTX_cleanup(&ctx_copy);
return ret;
}
@@ -503,44 +502,19 @@
* underlying digests so can be called multiple times and prior to the final
* update etc. */
int tls1_handshake_digest(SSL *s, uint8_t *out, size_t out_len) {
- const EVP_MD *md;
- EVP_MD_CTX ctx;
- int err = 0, len = 0;
- size_t i;
- uint32_t mask;
-
- EVP_MD_CTX_init(&ctx);
-
- for (i = 0; ssl_get_handshake_digest(&mask, &md, i); i++) {
- size_t hash_size;
- unsigned int digest_len;
- EVP_MD_CTX *hdgst = s->s3->handshake_dgst[i];
-
- if ((mask & ssl_get_algorithm_prf(s)) == 0) {
- continue;
- }
-
- hash_size = EVP_MD_size(md);
- if (!hdgst ||
- hash_size > out_len ||
- !EVP_MD_CTX_copy_ex(&ctx, hdgst) ||
- !EVP_DigestFinal_ex(&ctx, out, &digest_len) ||
- digest_len != hash_size /* internal error */) {
- err = 1;
- break;
- }
-
- out += digest_len;
- out_len -= digest_len;
- len += digest_len;
- }
-
- EVP_MD_CTX_cleanup(&ctx);
-
- if (err != 0) {
+ size_t md5_len = 0;
+ if (EVP_MD_CTX_md(&s->s3->handshake_md5) != NULL &&
+ !append_digest(&s->s3->handshake_md5, out, &md5_len, out_len)) {
return -1;
}
- return len;
+
+ size_t len;
+ if (!append_digest(&s->s3->handshake_hash, out + md5_len, &len,
+ out_len - md5_len)) {
+ return -1;
+ }
+
+ return (int)(md5_len + len);
}
int tls1_final_finish_mac(SSL *s, const char *str, int slen, uint8_t *out) {