diff options
Diffstat (limited to 'library/hkdf.c')
| -rw-r--r-- | library/hkdf.c | 161 |
1 files changed, 161 insertions, 0 deletions
diff --git a/library/hkdf.c b/library/hkdf.c new file mode 100644 index 00000000000..631ac24e530 --- /dev/null +++ b/library/hkdf.c @@ -0,0 +1,161 @@ +/* + * HKDF implementation -- RFC 5869 + * + * Copyright The Mbed TLS Contributors + * SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later + */ +#include "common.h" + +#if defined(MBEDTLS_HKDF_C) + +#include <string.h> +#include "mbedtls/hkdf.h" +#include "mbedtls/platform_util.h" +#include "mbedtls/error.h" + +int mbedtls_hkdf(const mbedtls_md_info_t *md, const unsigned char *salt, + size_t salt_len, const unsigned char *ikm, size_t ikm_len, + const unsigned char *info, size_t info_len, + unsigned char *okm, size_t okm_len) +{ + int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; + unsigned char prk[MBEDTLS_MD_MAX_SIZE]; + + ret = mbedtls_hkdf_extract(md, salt, salt_len, ikm, ikm_len, prk); + + if (ret == 0) { + ret = mbedtls_hkdf_expand(md, prk, mbedtls_md_get_size(md), + info, info_len, okm, okm_len); + } + + mbedtls_platform_zeroize(prk, sizeof(prk)); + + return ret; +} + +int mbedtls_hkdf_extract(const mbedtls_md_info_t *md, + const unsigned char *salt, size_t salt_len, + const unsigned char *ikm, size_t ikm_len, + unsigned char *prk) +{ + unsigned char null_salt[MBEDTLS_MD_MAX_SIZE] = { '\0' }; + + if (salt == NULL) { + size_t hash_len; + + if (salt_len != 0) { + return MBEDTLS_ERR_HKDF_BAD_INPUT_DATA; + } + + hash_len = mbedtls_md_get_size(md); + + if (hash_len == 0) { + return MBEDTLS_ERR_HKDF_BAD_INPUT_DATA; + } + + salt = null_salt; + salt_len = hash_len; + } + + return mbedtls_md_hmac(md, salt, salt_len, ikm, ikm_len, prk); +} + +int mbedtls_hkdf_expand(const mbedtls_md_info_t *md, const unsigned char *prk, + size_t prk_len, const unsigned char *info, + size_t info_len, unsigned char *okm, size_t okm_len) +{ + size_t hash_len; + size_t where = 0; + size_t n; + size_t t_len = 0; + size_t i; + int ret = 0; + mbedtls_md_context_t ctx; + unsigned char t[MBEDTLS_MD_MAX_SIZE]; + + if (okm == NULL) { + return MBEDTLS_ERR_HKDF_BAD_INPUT_DATA; + } + + hash_len = mbedtls_md_get_size(md); + + if (prk_len < hash_len || hash_len == 0) { + return MBEDTLS_ERR_HKDF_BAD_INPUT_DATA; + } + + if (info == NULL) { + info = (const unsigned char *) ""; + info_len = 0; + } + + n = okm_len / hash_len; + + if (okm_len % hash_len != 0) { + n++; + } + + /* + * Per RFC 5869 Section 2.3, okm_len must not exceed + * 255 times the hash length + */ + if (n > 255) { + return MBEDTLS_ERR_HKDF_BAD_INPUT_DATA; + } + + mbedtls_md_init(&ctx); + + if ((ret = mbedtls_md_setup(&ctx, md, 1)) != 0) { + goto exit; + } + + memset(t, 0, hash_len); + + /* + * Compute T = T(1) | T(2) | T(3) | ... | T(N) + * Where T(N) is defined in RFC 5869 Section 2.3 + */ + for (i = 1; i <= n; i++) { + size_t num_to_copy; + unsigned char c = i & 0xff; + + ret = mbedtls_md_hmac_starts(&ctx, prk, prk_len); + if (ret != 0) { + goto exit; + } + + ret = mbedtls_md_hmac_update(&ctx, t, t_len); + if (ret != 0) { + goto exit; + } + + ret = mbedtls_md_hmac_update(&ctx, info, info_len); + if (ret != 0) { + goto exit; + } + + /* The constant concatenated to the end of each T(n) is a single octet. + * */ + ret = mbedtls_md_hmac_update(&ctx, &c, 1); + if (ret != 0) { + goto exit; + } + + ret = mbedtls_md_hmac_finish(&ctx, t); + if (ret != 0) { + goto exit; + } + + num_to_copy = i != n ? hash_len : okm_len - where; + memcpy(okm + where, t, num_to_copy); + where += hash_len; + t_len = hash_len; + } + +exit: + mbedtls_md_free(&ctx); + mbedtls_platform_zeroize(t, sizeof(t)); + + return ret; +} + +#endif /* MBEDTLS_HKDF_C */ |