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// SPDX-License-Identifier: BSD-2-Clause
/*
* Copyright (c) 2014, Linaro Limited
*/
#include <crypto/crypto.h>
#include <stdlib.h>
#include <string.h>
#include <tee/tee_cryp_hkdf.h>
#include <tee/tee_cryp_utl.h>
#include <utee_defines.h>
static const uint8_t zero_salt[TEE_MAX_HASH_SIZE];
static TEE_Result hkdf_extract(uint32_t hash_id, const uint8_t *ikm,
size_t ikm_len, const uint8_t *salt,
size_t salt_len, uint8_t *prk, size_t *prk_len)
{
TEE_Result res;
void *ctx = NULL;
uint32_t hash_algo = TEE_ALG_HASH_ALGO(hash_id);
uint32_t hmac_algo = (TEE_OPERATION_MAC << 28) | hash_id;
if (!salt || !salt_len) {
/*
* RFC 5869 section 2.2:
* If not provided, [the salt] is set to a string of HashLen
* zeros
*/
salt = zero_salt;
res = tee_hash_get_digest_size(hash_algo, &salt_len);
if (res != TEE_SUCCESS)
goto out;
}
res = crypto_mac_alloc_ctx(&ctx, hmac_algo);
if (res)
goto out;
/*
* RFC 5869 section 2.1: "Note that in the extract step, 'IKM' is used
* as the HMAC input, not as the HMAC key."
* Therefore, salt is the HMAC key in the formula from section 2.2:
* "PRK = HMAC-Hash(salt, IKM)"
*/
res = crypto_mac_init(ctx, hmac_algo, salt, salt_len);
if (res != TEE_SUCCESS)
goto out;
res = crypto_mac_update(ctx, hmac_algo, ikm, ikm_len);
if (res != TEE_SUCCESS)
goto out;
res = crypto_mac_final(ctx, hmac_algo, prk, *prk_len);
if (res != TEE_SUCCESS)
goto out;
res = tee_hash_get_digest_size(hash_algo, prk_len);
out:
crypto_mac_free_ctx(ctx, hmac_algo);
return res;
}
static TEE_Result hkdf_expand(uint32_t hash_id, const uint8_t *prk,
size_t prk_len, const uint8_t *info,
size_t info_len, uint8_t *okm, size_t okm_len)
{
uint8_t tn[TEE_MAX_HASH_SIZE];
size_t tn_len, hash_len, i, n, where;
TEE_Result res = TEE_SUCCESS;
void *ctx = NULL;
uint32_t hash_algo = TEE_ALG_HASH_ALGO(hash_id);
uint32_t hmac_algo = TEE_ALG_HMAC_ALGO(hash_id);
res = tee_hash_get_digest_size(hash_algo, &hash_len);
if (res != TEE_SUCCESS)
goto out;
if (!okm || prk_len < hash_len) {
res = TEE_ERROR_BAD_STATE;
goto out;
}
if (!info)
info_len = 0;
res = crypto_mac_alloc_ctx(&ctx, hmac_algo);
if (res)
goto out;
/* N = ceil(L/HashLen) */
n = okm_len / hash_len;
if ((okm_len % hash_len) != 0)
n++;
if (n > 255) {
res = TEE_ERROR_BAD_PARAMETERS;
goto out;
}
/*
* RFC 5869 section 2.3
* T = T(1) | T(2) | T(3) | ... | T(N)
* OKM = first L octets of T
* T(0) = empty string (zero length)
* T(1) = HMAC-Hash(PRK, T(0) | info | 0x01)
* T(2) = HMAC-Hash(PRK, T(1) | info | 0x02)
* T(3) = HMAC-Hash(PRK, T(2) | info | 0x03)
* ...
*/
tn_len = 0;
where = 0;
for (i = 1; i <= n; i++) {
uint8_t c = i;
res = crypto_mac_init(ctx, hmac_algo, prk, prk_len);
if (res != TEE_SUCCESS)
goto out;
res = crypto_mac_update(ctx, hmac_algo, tn, tn_len);
if (res != TEE_SUCCESS)
goto out;
res = crypto_mac_update(ctx, hmac_algo, info, info_len);
if (res != TEE_SUCCESS)
goto out;
res = crypto_mac_update(ctx, hmac_algo, &c, 1);
if (res != TEE_SUCCESS)
goto out;
res = crypto_mac_final(ctx, hmac_algo, tn, sizeof(tn));
if (res != TEE_SUCCESS)
goto out;
memcpy(okm + where, tn, (i < n) ? hash_len : (okm_len - where));
where += hash_len;
tn_len = hash_len;
}
out:
crypto_mac_free_ctx(ctx, hmac_algo);
return res;
}
TEE_Result tee_cryp_hkdf(uint32_t hash_id, const uint8_t *ikm, size_t ikm_len,
const uint8_t *salt, size_t salt_len,
const uint8_t *info, size_t info_len, uint8_t *okm,
size_t okm_len)
{
TEE_Result res;
uint8_t prk[TEE_MAX_HASH_SIZE];
size_t prk_len = sizeof(prk);
res = hkdf_extract(hash_id, ikm, ikm_len, salt, salt_len, prk,
&prk_len);
if (res != TEE_SUCCESS)
return res;
res = hkdf_expand(hash_id, prk, prk_len, info, info_len, okm,
okm_len);
return res;
}
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