17cf2cb1d2
Most C standard library functions are undefined if passed NULL, even when the corresponding length is zero. This gives them (and, in turn, all functions which call them) surprising behavior on empty arrays. Some compilers will miscompile code due to this rule. See also https://www.imperialviolet.org/2016/06/26/nonnull.html Add OPENSSL_memcpy, etc., wrappers which avoid this problem. BUG=23 Change-Id: I95f42b23e92945af0e681264fffaf578e7f8465e Reviewed-on: https://boringssl-review.googlesource.com/12928 Commit-Queue: David Benjamin <davidben@google.com> Reviewed-by: Adam Langley <agl@google.com>
113 lines
3.3 KiB
C
113 lines
3.3 KiB
C
/* Copyright (c) 2014, Google Inc.
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*
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* Permission to use, copy, modify, and/or distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
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* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
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* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
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* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
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#include <openssl/hkdf.h>
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#include <assert.h>
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#include <string.h>
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#include <openssl/err.h>
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#include <openssl/hmac.h>
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#include "../internal.h"
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int HKDF(uint8_t *out_key, size_t out_len, const EVP_MD *digest,
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const uint8_t *secret, size_t secret_len, const uint8_t *salt,
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size_t salt_len, const uint8_t *info, size_t info_len) {
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/* https://tools.ietf.org/html/rfc5869#section-2 */
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uint8_t prk[EVP_MAX_MD_SIZE];
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size_t prk_len;
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if (!HKDF_extract(prk, &prk_len, digest, secret, secret_len, salt,
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salt_len) ||
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!HKDF_expand(out_key, out_len, digest, prk, prk_len, info, info_len)) {
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return 0;
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}
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return 1;
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}
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int HKDF_extract(uint8_t *out_key, size_t *out_len, const EVP_MD *digest,
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const uint8_t *secret, size_t secret_len, const uint8_t *salt,
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size_t salt_len) {
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/* https://tools.ietf.org/html/rfc5869#section-2.2 */
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/* If salt is not given, HashLength zeros are used. However, HMAC does that
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* internally already so we can ignore it.*/
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unsigned len;
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if (HMAC(digest, salt, salt_len, secret, secret_len, out_key, &len) == NULL) {
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OPENSSL_PUT_ERROR(HKDF, ERR_R_HMAC_LIB);
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return 0;
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}
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*out_len = len;
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assert(*out_len == EVP_MD_size(digest));
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return 1;
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}
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int HKDF_expand(uint8_t *out_key, size_t out_len, const EVP_MD *digest,
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const uint8_t *prk, size_t prk_len, const uint8_t *info,
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size_t info_len) {
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/* https://tools.ietf.org/html/rfc5869#section-2.3 */
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const size_t digest_len = EVP_MD_size(digest);
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uint8_t previous[EVP_MAX_MD_SIZE];
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size_t n, done = 0;
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unsigned i;
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int ret = 0;
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HMAC_CTX hmac;
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/* Expand key material to desired length. */
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n = (out_len + digest_len - 1) / digest_len;
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if (out_len + digest_len < out_len || n > 255) {
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OPENSSL_PUT_ERROR(HKDF, HKDF_R_OUTPUT_TOO_LARGE);
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return 0;
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}
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HMAC_CTX_init(&hmac);
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if (!HMAC_Init_ex(&hmac, prk, prk_len, digest, NULL)) {
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goto out;
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}
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for (i = 0; i < n; i++) {
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uint8_t ctr = i + 1;
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size_t todo;
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if (i != 0 && (!HMAC_Init_ex(&hmac, NULL, 0, NULL, NULL) ||
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!HMAC_Update(&hmac, previous, digest_len))) {
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goto out;
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}
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if (!HMAC_Update(&hmac, info, info_len) ||
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!HMAC_Update(&hmac, &ctr, 1) ||
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!HMAC_Final(&hmac, previous, NULL)) {
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goto out;
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}
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todo = digest_len;
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if (done + todo > out_len) {
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todo = out_len - done;
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}
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OPENSSL_memcpy(out_key + done, previous, todo);
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done += todo;
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}
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ret = 1;
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out:
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HMAC_CTX_cleanup(&hmac);
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if (ret != 1) {
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OPENSSL_PUT_ERROR(HKDF, ERR_R_HMAC_LIB);
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}
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return ret;
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}
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