| /* |
| * CDDL HEADER START |
| * |
| * This file and its contents are supplied under the terms of the |
| * Common Development and Distribution License ("CDDL"), version 1.0. |
| * You may only use this file in accordance with the terms of version |
| * 1.0 of the CDDL. |
| * |
| * A full copy of the text of the CDDL should have accompanied this |
| * source. A copy of the CDDL is also available via the Internet at |
| * http://www.illumos.org/license/CDDL. |
| * |
| * CDDL HEADER END |
| */ |
| |
| /* |
| * Copyright (c) 2017, Datto, Inc. All rights reserved. |
| */ |
| |
| #include <sys/dmu.h> |
| #include <sys/hkdf.h> |
| #include <sys/freebsd_crypto.h> |
| #include <sys/hkdf.h> |
| |
| static int |
| hkdf_sha512_extract(uint8_t *salt, uint_t salt_len, uint8_t *key_material, |
| uint_t km_len, uint8_t *out_buf) |
| { |
| crypto_key_t key; |
| |
| /* initialize the salt as a crypto key */ |
| key.ck_format = CRYPTO_KEY_RAW; |
| key.ck_length = CRYPTO_BYTES2BITS(salt_len); |
| key.ck_data = salt; |
| |
| crypto_mac(&key, key_material, km_len, out_buf, SHA512_DIGEST_LENGTH); |
| |
| return (0); |
| } |
| |
| static int |
| hkdf_sha512_expand(uint8_t *extract_key, uint8_t *info, uint_t info_len, |
| uint8_t *out_buf, uint_t out_len) |
| { |
| struct hmac_ctx ctx; |
| crypto_key_t key; |
| uint_t i, T_len = 0, pos = 0; |
| uint8_t c; |
| uint_t N = (out_len + SHA512_DIGEST_LENGTH) / SHA512_DIGEST_LENGTH; |
| uint8_t T[SHA512_DIGEST_LENGTH]; |
| |
| if (N > 255) |
| return (SET_ERROR(EINVAL)); |
| |
| /* initialize the salt as a crypto key */ |
| key.ck_format = CRYPTO_KEY_RAW; |
| key.ck_length = CRYPTO_BYTES2BITS(SHA512_DIGEST_LENGTH); |
| key.ck_data = extract_key; |
| |
| for (i = 1; i <= N; i++) { |
| c = i; |
| |
| crypto_mac_init(&ctx, &key); |
| crypto_mac_update(&ctx, T, T_len); |
| crypto_mac_update(&ctx, info, info_len); |
| crypto_mac_update(&ctx, &c, 1); |
| crypto_mac_final(&ctx, T, SHA512_DIGEST_LENGTH); |
| bcopy(T, out_buf + pos, |
| (i != N) ? SHA512_DIGEST_LENGTH : (out_len - pos)); |
| pos += SHA512_DIGEST_LENGTH; |
| } |
| |
| return (0); |
| } |
| |
| /* |
| * HKDF is designed to be a relatively fast function for deriving keys from a |
| * master key + a salt. We use this function to generate new encryption keys |
| * so as to avoid hitting the cryptographic limits of the underlying |
| * encryption modes. Note that, for the sake of deriving encryption keys, the |
| * info parameter is called the "salt" everywhere else in the code. |
| */ |
| int |
| hkdf_sha512(uint8_t *key_material, uint_t km_len, uint8_t *salt, |
| uint_t salt_len, uint8_t *info, uint_t info_len, uint8_t *output_key, |
| uint_t out_len) |
| { |
| int ret; |
| uint8_t extract_key[SHA512_DIGEST_LENGTH]; |
| |
| ret = hkdf_sha512_extract(salt, salt_len, key_material, km_len, |
| extract_key); |
| if (ret != 0) |
| return (ret); |
| |
| ret = hkdf_sha512_expand(extract_key, info, info_len, output_key, |
| out_len); |
| if (ret != 0) |
| return (ret); |
| |
| return (0); |
| } |