120 lines
3.2 KiB
C
Executable file
120 lines
3.2 KiB
C
Executable file
/* $OpenBSD: hkdf.c,v 1.7 2021/12/12 21:30:14 tb Exp $ */
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/* 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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*/
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#include <openssl/hkdf.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 "evp_locl.h"
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#include "hmac_local.h"
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/* https://tools.ietf.org/html/rfc5869#section-2 */
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int
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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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{
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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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return 0;
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if (!HKDF_expand(out_key, out_len, digest, prk, prk_len, info,
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info_len))
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return 0;
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return 1;
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}
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/* https://tools.ietf.org/html/rfc5869#section-2.2 */
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int
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HKDF_extract(uint8_t *out_key, size_t *out_len,
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const EVP_MD *digest, const uint8_t *secret, size_t secret_len,
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const uint8_t *salt, size_t salt_len)
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{
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unsigned int len;
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/*
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* If salt is not given, HashLength zeros are used. However, HMAC does
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* that internally already so we can ignore it.
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*/
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if (HMAC(digest, salt, salt_len, secret, secret_len, out_key, &len) ==
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NULL) {
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CRYPTOerror(ERR_R_CRYPTO_LIB);
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return 0;
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}
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*out_len = len;
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return 1;
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}
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/* https://tools.ietf.org/html/rfc5869#section-2.3 */
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int
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HKDF_expand(uint8_t *out_key, size_t out_len,
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const EVP_MD *digest, const uint8_t *prk, size_t prk_len,
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const uint8_t *info, size_t info_len)
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{
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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 int 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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CRYPTOerror(EVP_R_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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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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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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todo = digest_len;
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if (done + todo > out_len)
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todo = out_len - done;
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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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explicit_bzero(previous, sizeof(previous));
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if (ret != 1)
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CRYPTOerror(ERR_R_CRYPTO_LIB);
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return ret;
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}
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