diff options
author | Matt Caswell <matt@openssl.org> | 2016-11-08 10:34:28 +0000 |
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committer | Matt Caswell <matt@openssl.org> | 2016-11-09 14:08:14 +0000 |
commit | 34574f193bf9961256d5b8bdb6950dcc890e0336 (patch) | |
tree | 8fecf61766bcbe05fdcb50607f82985222d30acb /ssl/tls13_enc.c | |
parent | 9b36b7d9bdb33d1edbc2bbfd8a773a0eb8645788 (diff) |
Add support for TLS1.3 secret generation
Nothing is using this yet, it just adds the underlying functions necesary
for generating the TLS1.3 secrets.
Reviewed-by: Rich Salz <rsalz@openssl.org>
Diffstat (limited to 'ssl/tls13_enc.c')
-rw-r--r-- | ssl/tls13_enc.c | 217 |
1 files changed, 217 insertions, 0 deletions
diff --git a/ssl/tls13_enc.c b/ssl/tls13_enc.c new file mode 100644 index 0000000000..0ac54bbfb5 --- /dev/null +++ b/ssl/tls13_enc.c @@ -0,0 +1,217 @@ +/* + * Copyright 2016 The OpenSSL Project Authors. All Rights Reserved. + * + * Licensed under the OpenSSL license (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 + */ + +#include <stdlib.h> +#include "ssl_locl.h" +#include <openssl/evp.h> +#include <openssl/kdf.h> + +#define TLS13_MAX_LABEL_LEN 246 + +/* Always filled with zeros */ +static const unsigned char default_zeros[EVP_MAX_MD_SIZE]; + +const unsigned char keylabel[] = "key"; +const unsigned char ivlabel[] = "iv"; + +/* + * Given a |secret|; a |label| of length |labellen|; and a |hash| of the + * handshake messages, derive a new secret |outlen| bytes long and store it in + * the location pointed to be |out|. The |hash| value may be NULL. + * + * Returns 1 on success 0 on failure. + */ +static int tls13_hkdf_expand(SSL *s, const unsigned char *secret, + const unsigned char *label, size_t labellen, + const unsigned char *hash, + unsigned char *out, size_t outlen) +{ + const unsigned char label_prefix[] = "TLS 1.3, "; + const EVP_MD *md = ssl_handshake_md(s); + EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, NULL); + int ret; + size_t hkdflabellen; + size_t hashlen; + /* + * 2 bytes for length of whole HkdfLabel + 1 byte for length of combined + * prefix and label + bytes for the label itself + bytes for the hash + */ + unsigned char hkdflabel[sizeof(uint16_t) + sizeof(uint8_t) + + + sizeof(label_prefix) + TLS13_MAX_LABEL_LEN + + EVP_MAX_MD_SIZE]; + WPACKET pkt; + + if (pctx == NULL) + return 0; + + hashlen = EVP_MD_size(md); + + if (!WPACKET_init_static_len(&pkt, hkdflabel, sizeof(hkdflabel), 0) + || !WPACKET_put_bytes_u16(&pkt, outlen) + || !WPACKET_start_sub_packet_u8(&pkt) + || !WPACKET_memcpy(&pkt, label_prefix, sizeof(label_prefix) - 1) + || !WPACKET_memcpy(&pkt, label, labellen) + || !WPACKET_close(&pkt) + || !WPACKET_sub_memcpy_u8(&pkt, hash, (hash == NULL) ? 0 : hashlen) + || !WPACKET_get_total_written(&pkt, &hkdflabellen) + || !WPACKET_finish(&pkt)) { + WPACKET_cleanup(&pkt); + return 0; + } + + ret = EVP_PKEY_derive_init(pctx) <= 0 + || EVP_PKEY_CTX_hkdf_mode(pctx, EVP_PKEY_HKDEF_MODE_EXPAND_ONLY) + <= 0 + || EVP_PKEY_CTX_set_hkdf_md(pctx, md) <= 0 + || EVP_PKEY_CTX_set1_hkdf_key(pctx, secret, hashlen) <= 0 + || EVP_PKEY_CTX_add1_hkdf_info(pctx, hkdflabel, hkdflabellen) <= 0 + || EVP_PKEY_derive(pctx, out, &outlen) <= 0; + + EVP_PKEY_CTX_free(pctx); + + return ret == 0; +} + +/* + * Given a input secret |insecret| and a |label| of length |labellen|, derive a + * new |secret|. This will be the length of the current hash output size and + * will be based on the current state of the handshake hashes. + * + * Returns 1 on success 0 on failure. + */ +int tls13_derive_secret(SSL *s, const unsigned char *insecret, + const unsigned char *label, size_t labellen, + unsigned char *secret) +{ + unsigned char hash[EVP_MAX_MD_SIZE]; + size_t hashlen; + + if (!ssl3_digest_cached_records(s, 1)) + return 0; + + if (!ssl_handshake_hash(s, hash, sizeof(hash), &hashlen)) + return 0; + + return tls13_hkdf_expand(s, insecret, label, labellen, hash, secret, + hashlen); +} + +/* + * Given a |secret| generate a |key| of length |keylen| bytes. + * + * Returns 1 on success 0 on failure. + */ +int tls13_derive_key(SSL *s, const unsigned char *secret, unsigned char *key, + size_t keylen) +{ + return tls13_hkdf_expand(s, secret, keylabel, sizeof(keylabel) - 1, NULL, + key, keylen); +} + +/* + * Given a |secret| generate an |iv| of length |ivlen| bytes. + * + * Returns 1 on success 0 on failure. + */ +int tls13_derive_iv(SSL *s, const unsigned char *secret, unsigned char *iv, + size_t ivlen) +{ + return tls13_hkdf_expand(s, secret, ivlabel, sizeof(ivlabel) - 1, NULL, + iv, ivlen); +} + +/* + * Given the previous secret |prevsecret| and a new input secret |insecret| of + * length |insecretlen|, generate a new secret and store it in the location + * pointed to by |outsecret|. + * + * Returns 1 on success 0 on failure. + */ +static int tls13_generate_secret(SSL *s, const unsigned char *prevsecret, + const unsigned char *insecret, + size_t insecretlen, + unsigned char *outsecret) +{ + const EVP_MD *md = ssl_handshake_md(s); + size_t mdlen, prevsecretlen; + int ret; + EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, NULL); + + if (pctx == NULL) + return 0; + + mdlen = EVP_MD_size(md); + + if (insecret == NULL) { + insecret = default_zeros; + insecretlen = mdlen; + } + if (prevsecret == NULL) { + prevsecret = default_zeros; + prevsecretlen = 0; + } else { + prevsecretlen = mdlen; + } + + ret = EVP_PKEY_derive_init(pctx) <= 0 + || EVP_PKEY_CTX_hkdf_mode(pctx, EVP_PKEY_HKDEF_MODE_EXTRACT_ONLY) + <= 0 + || EVP_PKEY_CTX_set_hkdf_md(pctx, md) <= 0 + || EVP_PKEY_CTX_set1_hkdf_key(pctx, insecret, insecretlen) <= 0 + || EVP_PKEY_CTX_set1_hkdf_salt(pctx, prevsecret, prevsecretlen) + <= 0 + || EVP_PKEY_derive(pctx, outsecret, &mdlen) + <= 0; + + EVP_PKEY_CTX_free(pctx); + return ret == 0; +} + +/* + * Given an input secret |insecret| of length |insecretlen| generate the early + * secret. + * + * Returns 1 on success 0 on failure. + */ +int tls13_generate_early_secret(SSL *s, const unsigned char *insecret, + size_t insecretlen) +{ + return tls13_generate_secret(s, NULL, insecret, insecretlen, + (unsigned char *)&s->early_secret); +} + +/* + * Given an input secret |insecret| of length |insecretlen| generate the + * handshake secret. This requires the early secret to already have been + * generated. + * + * Returns 1 on success 0 on failure. + */ +int tls13_generate_handshake_secret(SSL *s, const unsigned char *insecret, + size_t insecretlen) +{ + return tls13_generate_secret(s, s->early_secret, insecret, insecretlen, + (unsigned char *)&s->handshake_secret); +} + +/* + * Given the handshake secret |prev| of length |prevlen| generate the master + * secret and store its length in |*secret_size| + * + * Returns 1 on success 0 on failure. + */ +int tls13_generate_master_secret(SSL *s, unsigned char *out, + unsigned char *prev, size_t prevlen, + size_t *secret_size) +{ + *secret_size = EVP_MD_size(ssl_handshake_md(s)); + return tls13_generate_secret(s, prev, NULL, 0, out); +} + + |