161 lines
3.9 KiB
C
161 lines
3.9 KiB
C
/*
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* HKDF implementation -- RFC 5869
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*
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* Copyright The Mbed TLS Contributors
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* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
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*/
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#include "common.h"
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#if defined(MBEDTLS_HKDF_C)
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#include <string.h>
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#include "mbedtls/hkdf.h"
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#include "mbedtls/platform_util.h"
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#include "mbedtls/error.h"
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int mbedtls_hkdf(const mbedtls_md_info_t *md, const unsigned char *salt,
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size_t salt_len, const unsigned char *ikm, size_t ikm_len,
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const unsigned char *info, size_t info_len,
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unsigned char *okm, size_t okm_len)
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{
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int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
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unsigned char prk[MBEDTLS_MD_MAX_SIZE];
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ret = mbedtls_hkdf_extract(md, salt, salt_len, ikm, ikm_len, prk);
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if (ret == 0) {
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ret = mbedtls_hkdf_expand(md, prk, mbedtls_md_get_size(md),
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info, info_len, okm, okm_len);
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}
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mbedtls_platform_zeroize(prk, sizeof(prk));
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return ret;
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}
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int mbedtls_hkdf_extract(const mbedtls_md_info_t *md,
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const unsigned char *salt, size_t salt_len,
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const unsigned char *ikm, size_t ikm_len,
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unsigned char *prk)
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{
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unsigned char null_salt[MBEDTLS_MD_MAX_SIZE] = { '\0' };
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if (salt == NULL) {
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size_t hash_len;
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if (salt_len != 0) {
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return MBEDTLS_ERR_HKDF_BAD_INPUT_DATA;
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}
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hash_len = mbedtls_md_get_size(md);
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if (hash_len == 0) {
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return MBEDTLS_ERR_HKDF_BAD_INPUT_DATA;
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}
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salt = null_salt;
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salt_len = hash_len;
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}
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return mbedtls_md_hmac(md, salt, salt_len, ikm, ikm_len, prk);
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}
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int mbedtls_hkdf_expand(const mbedtls_md_info_t *md, const unsigned char *prk,
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size_t prk_len, const unsigned char *info,
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size_t info_len, unsigned char *okm, size_t okm_len)
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{
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size_t hash_len;
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size_t where = 0;
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size_t n;
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size_t t_len = 0;
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size_t i;
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int ret = 0;
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mbedtls_md_context_t ctx;
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unsigned char t[MBEDTLS_MD_MAX_SIZE];
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if (okm == NULL) {
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return MBEDTLS_ERR_HKDF_BAD_INPUT_DATA;
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}
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hash_len = mbedtls_md_get_size(md);
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if (prk_len < hash_len || hash_len == 0) {
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return MBEDTLS_ERR_HKDF_BAD_INPUT_DATA;
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}
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if (info == NULL) {
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info = (const unsigned char *) "";
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info_len = 0;
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}
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n = okm_len / hash_len;
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if (okm_len % hash_len != 0) {
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n++;
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}
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/*
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* Per RFC 5869 Section 2.3, okm_len must not exceed
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* 255 times the hash length
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*/
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if (n > 255) {
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return MBEDTLS_ERR_HKDF_BAD_INPUT_DATA;
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}
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mbedtls_md_init(&ctx);
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if ((ret = mbedtls_md_setup(&ctx, md, 1)) != 0) {
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goto exit;
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}
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memset(t, 0, hash_len);
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/*
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* Compute T = T(1) | T(2) | T(3) | ... | T(N)
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* Where T(N) is defined in RFC 5869 Section 2.3
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*/
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for (i = 1; i <= n; i++) {
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size_t num_to_copy;
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unsigned char c = i & 0xff;
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ret = mbedtls_md_hmac_starts(&ctx, prk, prk_len);
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if (ret != 0) {
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goto exit;
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}
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ret = mbedtls_md_hmac_update(&ctx, t, t_len);
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if (ret != 0) {
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goto exit;
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}
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ret = mbedtls_md_hmac_update(&ctx, info, info_len);
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if (ret != 0) {
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goto exit;
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}
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/* The constant concatenated to the end of each T(n) is a single octet.
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* */
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ret = mbedtls_md_hmac_update(&ctx, &c, 1);
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if (ret != 0) {
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goto exit;
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}
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ret = mbedtls_md_hmac_finish(&ctx, t);
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if (ret != 0) {
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goto exit;
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}
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num_to_copy = i != n ? hash_len : okm_len - where;
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memcpy(okm + where, t, num_to_copy);
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where += hash_len;
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t_len = hash_len;
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}
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exit:
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mbedtls_md_free(&ctx);
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mbedtls_platform_zeroize(t, sizeof(t));
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return ret;
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}
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#endif /* MBEDTLS_HKDF_C */
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