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/*
Unix SMB/CIFS implementation.
Wrapper for gnutls key derivation functions
Copyright (C) Stefan Metzmacher 2009
Copyright (C) Catalyst.Net Ltd 2023
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "includes.h"
#include <gnutls/gnutls.h>
#include <gnutls/crypto.h>
#include "gnutls_helpers.h"
static NTSTATUS samba_gnutls_sp800_108_derive_key_part(
const gnutls_hmac_hd_t hmac_hnd,
const uint8_t *FixedData,
const size_t FixedData_len,
const uint8_t *Label,
const size_t Label_len,
const uint8_t *Context,
const size_t Context_len,
const uint32_t L,
const uint32_t i,
uint8_t *digest)
{
uint8_t buf[4];
static const uint8_t zero = 0;
int rc;
PUSH_BE_U32(buf, 0, i);
rc = gnutls_hmac(hmac_hnd, buf, sizeof(buf));
if (rc < 0) {
return gnutls_error_to_ntstatus(rc,
NT_STATUS_HMAC_NOT_SUPPORTED);
}
if (FixedData != NULL) {
rc = gnutls_hmac(hmac_hnd, FixedData, FixedData_len);
if (rc < 0) {
return gnutls_error_to_ntstatus(
rc, NT_STATUS_HMAC_NOT_SUPPORTED);
}
} else {
rc = gnutls_hmac(hmac_hnd, Label, Label_len);
if (rc < 0) {
return gnutls_error_to_ntstatus(
rc, NT_STATUS_HMAC_NOT_SUPPORTED);
}
rc = gnutls_hmac(hmac_hnd, &zero, 1);
if (rc < 0) {
return gnutls_error_to_ntstatus(
rc, NT_STATUS_HMAC_NOT_SUPPORTED);
}
rc = gnutls_hmac(hmac_hnd, Context, Context_len);
if (rc < 0) {
return gnutls_error_to_ntstatus(
rc, NT_STATUS_HMAC_NOT_SUPPORTED);
}
PUSH_BE_U32(buf, 0, L);
rc = gnutls_hmac(hmac_hnd, buf, sizeof(buf));
if (rc < 0) {
return gnutls_error_to_ntstatus(
rc, NT_STATUS_HMAC_NOT_SUPPORTED);
}
}
gnutls_hmac_output(hmac_hnd, digest);
return NT_STATUS_OK;
}
static size_t ceiling_div(const size_t a, const size_t b)
{
return a / b + (a % b != 0);
}
/**
* @brief Derive a key using the NIST SP 800‐108 algorithm.
*
* The details of the algorithm can be found at
* https://csrc.nist.gov/pubs/sp/800/108/r1/final.
*
* @param KI The key‐derivation key used as input.
*
* @param KI_len The length of the key‐derivation key.
*
* @param FixedData If non‐NULL, specifies fixed data to be used in place of
* that constructed from the Label and Context parameters.
*
* @param FixedData_len The length of the fixed data, if it is present.
*
* @param Label A label that identifies the purpose for the derived key.
* Ignored if FixedData is non‐NULL.
*
* @param Label_len The length of the label.
*
* @param Context Information related to the derived key. Ignored if
* FixedData is non‐NULL.
*
* @param Context_len The length of the context data.
*
* @param algorithm The HMAC algorithm to use.
*
* @param KO A buffer to receive the derived key.
*
* @param KO_len The length of the key to be derived.
*
* @return NT_STATUS_OK on success, an NT status error code otherwise.
*/
NTSTATUS samba_gnutls_sp800_108_derive_key(
const uint8_t *KI,
size_t KI_len,
const uint8_t *FixedData,
size_t FixedData_len,
const uint8_t *Label,
size_t Label_len,
const uint8_t *Context,
size_t Context_len,
const gnutls_mac_algorithm_t algorithm,
uint8_t *KO,
size_t KO_len)
{
gnutls_hmac_hd_t hmac_hnd = NULL;
const size_t digest_len = gnutls_hmac_get_len(algorithm);
uint32_t i;
uint32_t L = KO_len * 8;
size_t KO_idx;
NTSTATUS status = NT_STATUS_OK;
int rc;
if (KO_len > UINT32_MAX / 8) {
/* The calculation of L has overflowed. */
return NT_STATUS_INTERNAL_ERROR;
}
if (digest_len == 0) {
return NT_STATUS_HMAC_NOT_SUPPORTED;
}
{
const size_t n_iterations = ceiling_div(KO_len, digest_len);
/*
* To ensure that the counter values are distinct, n shall not
* be larger than 2ʳ−1, where r = 32. We have made sure that
* |KO| × 8 < 2³², and we know that n ≤ |KO| from its
* definition. Thus n ≤ |KO| ≤ |KO| × 8 < 2³², and so the
* requirement n ≤ 2³² − 1 must always hold.
*/
SMB_ASSERT(n_iterations <= UINT32_MAX);
}
/*
* a simplified version of
* "NIST Special Publication 800-108" section 5.1.
*/
rc = gnutls_hmac_init(&hmac_hnd,
algorithm,
KI,
KI_len);
if (rc < 0) {
return gnutls_error_to_ntstatus(rc,
NT_STATUS_HMAC_NOT_SUPPORTED);
}
/* (This loop would make an excellent candidate for parallelization.) */
for (KO_idx = 0, i = 1; KO_len - KO_idx >= digest_len;
KO_idx += digest_len, ++i)
{
status = samba_gnutls_sp800_108_derive_key_part(hmac_hnd,
FixedData,
FixedData_len,
Label,
Label_len,
Context,
Context_len,
L,
i,
KO + KO_idx);
if (!NT_STATUS_IS_OK(status)) {
goto out;
}
}
if (KO_idx < KO_len) {
/* Get the last little bit. */
uint8_t digest[digest_len];
status = samba_gnutls_sp800_108_derive_key_part(hmac_hnd,
FixedData,
FixedData_len,
Label,
Label_len,
Context,
Context_len,
L,
i,
digest);
if (!NT_STATUS_IS_OK(status)) {
goto out;
}
memcpy(KO + KO_idx, digest, KO_len - KO_idx);
ZERO_ARRAY(digest);
}
out:
if (hmac_hnd != NULL) {
gnutls_hmac_deinit(hmac_hnd, NULL);
}
if (!NT_STATUS_IS_OK(status)) {
/* Hide the evidence. */
memset_s(KO, KO_len, 0, KO_idx);
}
return status;
}
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