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b9eeace74a81be5f9b8c13446a61aed1d3e600db
mbedtls/library/lmots.c
Minos Galanakis caaffc1e7e Built-in lms/lmots driver: Harden public key import against enum truncation 
Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
2025-06-04 15:54:46 +01:00

790 lines
27 KiB
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/*
* The LM-OTS one-time public-key signature scheme
*
* Copyright The Mbed TLS Contributors
* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
*/
/*
* The following sources were referenced in the design of this implementation
* of the LM-OTS algorithm:
*
* [1] IETF RFC8554
* D. McGrew, M. Curcio, S.Fluhrer
* https://datatracker.ietf.org/doc/html/rfc8554
*
* [2] NIST Special Publication 800-208
* David A. Cooper et. al.
* https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-208.pdf
*/
#include "common.h"
#if defined(MBEDTLS_LMS_C)
#include <string.h>
#include "lmots.h"
#include "mbedtls/lms.h"
#include "mbedtls/platform_util.h"
#include "mbedtls/error.h"
#include "psa_util_internal.h"
#include "psa/crypto.h"
/* Define a local translating function to save code size by not using too many
* arguments in each translating place. */
static int local_err_translation(psa_status_t status)
{
return psa_status_to_mbedtls(status, psa_to_lms_errors,
ARRAY_LENGTH(psa_to_lms_errors),
psa_generic_status_to_mbedtls);
}
#define PSA_TO_MBEDTLS_ERR(status) local_err_translation(status)
#define PUBLIC_KEY_TYPE_OFFSET (0)
#define PUBLIC_KEY_I_KEY_ID_OFFSET (PUBLIC_KEY_TYPE_OFFSET + \
MBEDTLS_LMOTS_TYPE_LEN)
#define PUBLIC_KEY_Q_LEAF_ID_OFFSET (PUBLIC_KEY_I_KEY_ID_OFFSET + \
MBEDTLS_LMOTS_I_KEY_ID_LEN)
#define PUBLIC_KEY_KEY_HASH_OFFSET (PUBLIC_KEY_Q_LEAF_ID_OFFSET + \
MBEDTLS_LMOTS_Q_LEAF_ID_LEN)
/* We only support parameter sets that use 8-bit digits, as it does not require
* translation logic between digits and bytes */
#define W_WINTERNITZ_PARAMETER (8u)
#define CHECKSUM_LEN (2)
#define I_DIGIT_IDX_LEN (2)
#define J_HASH_IDX_LEN (1)
#define D_CONST_LEN (2)
#define DIGIT_MAX_VALUE ((1u << W_WINTERNITZ_PARAMETER) - 1u)
#define D_CONST_LEN (2)
static const unsigned char D_PUBLIC_CONSTANT_BYTES[D_CONST_LEN] = { 0x80, 0x80 };
static const unsigned char D_MESSAGE_CONSTANT_BYTES[D_CONST_LEN] = { 0x81, 0x81 };
#if defined(MBEDTLS_TEST_HOOKS)
int (*mbedtls_lmots_sign_private_key_invalidated_hook)(unsigned char *) = NULL;
#endif /* defined(MBEDTLS_TEST_HOOKS) */
/* Calculate the checksum digits that are appended to the end of the LMOTS digit
* string. See NIST SP800-208 section 3.1 or RFC8554 Algorithm 2 for details of
* the checksum algorithm.
*
* params The LMOTS parameter set, I and q values which
* describe the key being used.
*
* digest The digit string to create the digest from. As
* this does not contain a checksum, it is the same
* size as a hash output.
*/
static unsigned short lmots_checksum_calculate(const mbedtls_lmots_parameters_t *params,
const unsigned char *digest)
{
size_t idx;
unsigned sum = 0;
for (idx = 0; idx < MBEDTLS_LMOTS_N_HASH_LEN(params->type); idx++) {
sum += DIGIT_MAX_VALUE - digest[idx];
}
return sum;
}
/* Create the string of digest digits (in the base determined by the Winternitz
* parameter with the checksum appended to the end (Q || cksm(Q)). See NIST
* SP800-208 section 3.1 or RFC8554 Algorithm 3 step 5 (also used in Algorithm
* 4b step 3) for details.
*
* params The LMOTS parameter set, I and q values which
* describe the key being used.
*
* msg The message that will be hashed to create the
* digest.
*
* msg_size The size of the message.
*
* C_random_value The random value that will be combined with the
* message digest. This is always the same size as a
* hash output for whichever hash algorithm is
* determined by the parameter set.
*
* output An output containing the digit string (+
* checksum) of length P digits (in the case of
* MBEDTLS_LMOTS_SHA256_N32_W8, this means it is of
* size P bytes).
*/
static int create_digit_array_with_checksum(const mbedtls_lmots_parameters_t *params,
const unsigned char *msg,
size_t msg_len,
const unsigned char *C_random_value,
unsigned char *out)
{
psa_hash_operation_t op = PSA_HASH_OPERATION_INIT;
psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
size_t output_hash_len;
unsigned short checksum;
status = psa_hash_setup(&op, PSA_ALG_SHA_256);
if (status != PSA_SUCCESS) {
goto exit;
}
status = psa_hash_update(&op, params->I_key_identifier,
MBEDTLS_LMOTS_I_KEY_ID_LEN);
if (status != PSA_SUCCESS) {
goto exit;
}
status = psa_hash_update(&op, params->q_leaf_identifier,
MBEDTLS_LMOTS_Q_LEAF_ID_LEN);
if (status != PSA_SUCCESS) {
goto exit;
}
status = psa_hash_update(&op, D_MESSAGE_CONSTANT_BYTES, D_CONST_LEN);
if (status != PSA_SUCCESS) {
goto exit;
}
status = psa_hash_update(&op, C_random_value,
MBEDTLS_LMOTS_C_RANDOM_VALUE_LEN(params->type));
if (status != PSA_SUCCESS) {
goto exit;
}
status = psa_hash_update(&op, msg, msg_len);
if (status != PSA_SUCCESS) {
goto exit;
}
status = psa_hash_finish(&op, out,
MBEDTLS_LMOTS_N_HASH_LEN(params->type),
&output_hash_len);
if (status != PSA_SUCCESS) {
goto exit;
}
checksum = lmots_checksum_calculate(params, out);
MBEDTLS_PUT_UINT16_BE(checksum, out, MBEDTLS_LMOTS_N_HASH_LEN(params->type));
exit:
psa_hash_abort(&op);
return PSA_TO_MBEDTLS_ERR(status);
}
/* Hash each element of the string of digits (+ checksum), producing a hash
* output for each element. This is used in several places (by varying the
* hash_idx_min/max_values) in order to calculate a public key from a private
* key (RFC8554 Algorithm 1 step 4), in order to sign a message (RFC8554
* Algorithm 3 step 5), and to calculate a public key candidate from a
* signature and message (RFC8554 Algorithm 4b step 3).
*
* params The LMOTS parameter set, I and q values which
* describe the key being used.
*
* x_digit_array The array of digits (of size P, 34 in the case of
* MBEDTLS_LMOTS_SHA256_N32_W8).
*
* hash_idx_min_values An array of the starting values of the j iterator
* for each of the members of the digit array. If
* this value in NULL, then all iterators will start
* at 0.
*
* hash_idx_max_values An array of the upper bound values of the j
* iterator for each of the members of the digit
* array. If this value in NULL, then iterator is
* bounded to be less than 2^w - 1 (255 in the case
* of MBEDTLS_LMOTS_SHA256_N32_W8)
*
* output An array containing a hash output for each member
* of the digit string P. In the case of
* MBEDTLS_LMOTS_SHA256_N32_W8, this is of size 32 *
* 34.
*/
static int hash_digit_array(const mbedtls_lmots_parameters_t *params,
const unsigned char *x_digit_array,
const unsigned char *hash_idx_min_values,
const unsigned char *hash_idx_max_values,
unsigned char *output)
{
unsigned int i_digit_idx;
unsigned char i_digit_idx_bytes[I_DIGIT_IDX_LEN];
unsigned int j_hash_idx;
unsigned char j_hash_idx_bytes[J_HASH_IDX_LEN];
unsigned int j_hash_idx_min;
unsigned int j_hash_idx_max;
psa_hash_operation_t op = PSA_HASH_OPERATION_INIT;
psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
size_t output_hash_len;
unsigned char tmp_hash[MBEDTLS_LMOTS_N_HASH_LEN_MAX];
for (i_digit_idx = 0;
i_digit_idx < MBEDTLS_LMOTS_P_SIG_DIGIT_COUNT(params->type);
i_digit_idx++) {
memcpy(tmp_hash,
&x_digit_array[i_digit_idx * MBEDTLS_LMOTS_N_HASH_LEN(params->type)],
MBEDTLS_LMOTS_N_HASH_LEN(params->type));
j_hash_idx_min = hash_idx_min_values != NULL ?
hash_idx_min_values[i_digit_idx] : 0;
j_hash_idx_max = hash_idx_max_values != NULL ?
hash_idx_max_values[i_digit_idx] : DIGIT_MAX_VALUE;
for (j_hash_idx = j_hash_idx_min;
j_hash_idx < j_hash_idx_max;
j_hash_idx++) {
status = psa_hash_setup(&op, PSA_ALG_SHA_256);
if (status != PSA_SUCCESS) {
goto exit;
}
status = psa_hash_update(&op,
params->I_key_identifier,
MBEDTLS_LMOTS_I_KEY_ID_LEN);
if (status != PSA_SUCCESS) {
goto exit;
}
status = psa_hash_update(&op,
params->q_leaf_identifier,
MBEDTLS_LMOTS_Q_LEAF_ID_LEN);
if (status != PSA_SUCCESS) {
goto exit;
}
MBEDTLS_PUT_UINT16_BE(i_digit_idx, i_digit_idx_bytes, 0);
status = psa_hash_update(&op, i_digit_idx_bytes, I_DIGIT_IDX_LEN);
if (status != PSA_SUCCESS) {
goto exit;
}
j_hash_idx_bytes[0] = (uint8_t) j_hash_idx;
status = psa_hash_update(&op, j_hash_idx_bytes, J_HASH_IDX_LEN);
if (status != PSA_SUCCESS) {
goto exit;
}
status = psa_hash_update(&op, tmp_hash,
MBEDTLS_LMOTS_N_HASH_LEN(params->type));
if (status != PSA_SUCCESS) {
goto exit;
}
status = psa_hash_finish(&op, tmp_hash, sizeof(tmp_hash),
&output_hash_len);
if (status != PSA_SUCCESS) {
goto exit;
}
psa_hash_abort(&op);
}
memcpy(&output[i_digit_idx * MBEDTLS_LMOTS_N_HASH_LEN(params->type)],
tmp_hash, MBEDTLS_LMOTS_N_HASH_LEN(params->type));
}
exit:
psa_hash_abort(&op);
mbedtls_platform_zeroize(tmp_hash, sizeof(tmp_hash));
return PSA_TO_MBEDTLS_ERR(status);
}
/* Combine the hashes of the digit array into a public key. This is used in
* in order to calculate a public key from a private key (RFC8554 Algorithm 1
* step 4), and to calculate a public key candidate from a signature and message
* (RFC8554 Algorithm 4b step 3).
*
* params The LMOTS parameter set, I and q values which describe
* the key being used.
* y_hashed_digits The array of hashes, one hash for each digit of the
* symbol array (which is of size P, 34 in the case of
* MBEDTLS_LMOTS_SHA256_N32_W8)
*
* pub_key The output public key (or candidate public key in
* case this is being run as part of signature
* verification), in the form of a hash output.
*/
static int public_key_from_hashed_digit_array(const mbedtls_lmots_parameters_t *params,
const unsigned char *y_hashed_digits,
unsigned char *pub_key)
{
psa_hash_operation_t op = PSA_HASH_OPERATION_INIT;
psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
size_t output_hash_len;
status = psa_hash_setup(&op, PSA_ALG_SHA_256);
if (status != PSA_SUCCESS) {
goto exit;
}
status = psa_hash_update(&op,
params->I_key_identifier,
MBEDTLS_LMOTS_I_KEY_ID_LEN);
if (status != PSA_SUCCESS) {
goto exit;
}
status = psa_hash_update(&op, params->q_leaf_identifier,
MBEDTLS_LMOTS_Q_LEAF_ID_LEN);
if (status != PSA_SUCCESS) {
goto exit;
}
status = psa_hash_update(&op, D_PUBLIC_CONSTANT_BYTES, D_CONST_LEN);
if (status != PSA_SUCCESS) {
goto exit;
}
status = psa_hash_update(&op, y_hashed_digits,
MBEDTLS_LMOTS_P_SIG_DIGIT_COUNT(params->type) *
MBEDTLS_LMOTS_N_HASH_LEN(params->type));
if (status != PSA_SUCCESS) {
goto exit;
}
status = psa_hash_finish(&op, pub_key,
MBEDTLS_LMOTS_N_HASH_LEN(params->type),
&output_hash_len);
if (status != PSA_SUCCESS) {
exit:
psa_hash_abort(&op);
}
return PSA_TO_MBEDTLS_ERR(status);
}
#if !defined(MBEDTLS_DEPRECATED_REMOVED)
int mbedtls_lms_error_from_psa(psa_status_t status)
{
switch (status) {
case PSA_SUCCESS:
return 0;
case PSA_ERROR_HARDWARE_FAILURE:
return MBEDTLS_ERR_PLATFORM_HW_ACCEL_FAILED;
case PSA_ERROR_NOT_SUPPORTED:
return MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED;
case PSA_ERROR_BUFFER_TOO_SMALL:
return MBEDTLS_ERR_LMS_BUFFER_TOO_SMALL;
case PSA_ERROR_INVALID_ARGUMENT:
return MBEDTLS_ERR_LMS_BAD_INPUT_DATA;
default:
return MBEDTLS_ERR_ERROR_GENERIC_ERROR;
}
}
#endif /* !MBEDTLS_DEPRECATED_REMOVED */
void mbedtls_lmots_public_init(mbedtls_lmots_public_t *ctx)
{
memset(ctx, 0, sizeof(*ctx));
}
void mbedtls_lmots_public_free(mbedtls_lmots_public_t *ctx)
{
if (ctx == NULL) {
return;
}
mbedtls_platform_zeroize(ctx, sizeof(*ctx));
}
int mbedtls_lmots_import_public_key(mbedtls_lmots_public_t *ctx,
const unsigned char *key, size_t key_len)
{
if (key_len < MBEDTLS_LMOTS_SIG_TYPE_OFFSET + MBEDTLS_LMOTS_TYPE_LEN) {
return MBEDTLS_ERR_LMS_BAD_INPUT_DATA;
}
uint32_t type = MBEDTLS_GET_UINT32_BE(key, MBEDTLS_LMOTS_SIG_TYPE_OFFSET);
if (type != (uint32_t) MBEDTLS_LMOTS_SHA256_N32_W8) {
return MBEDTLS_ERR_LMS_BAD_INPUT_DATA;
}
ctx->params.type = (mbedtls_lmots_algorithm_type_t) type;
if (key_len != MBEDTLS_LMOTS_PUBLIC_KEY_LEN(ctx->params.type)) {
return MBEDTLS_ERR_LMS_BAD_INPUT_DATA;
}
memcpy(ctx->params.I_key_identifier,
key + PUBLIC_KEY_I_KEY_ID_OFFSET,
MBEDTLS_LMOTS_I_KEY_ID_LEN);
memcpy(ctx->params.q_leaf_identifier,
key + PUBLIC_KEY_Q_LEAF_ID_OFFSET,
MBEDTLS_LMOTS_Q_LEAF_ID_LEN);
memcpy(ctx->public_key,
key + PUBLIC_KEY_KEY_HASH_OFFSET,
MBEDTLS_LMOTS_N_HASH_LEN(ctx->params.type));
ctx->have_public_key = 1;
return 0;
}
int mbedtls_lmots_export_public_key(const mbedtls_lmots_public_t *ctx,
unsigned char *key, size_t key_size,
size_t *key_len)
{
if (key_size < MBEDTLS_LMOTS_PUBLIC_KEY_LEN(ctx->params.type)) {
return MBEDTLS_ERR_LMS_BUFFER_TOO_SMALL;
}
if (!ctx->have_public_key) {
return MBEDTLS_ERR_LMS_BAD_INPUT_DATA;
}
MBEDTLS_PUT_UINT32_BE(ctx->params.type, key, MBEDTLS_LMOTS_SIG_TYPE_OFFSET);
memcpy(key + PUBLIC_KEY_I_KEY_ID_OFFSET,
ctx->params.I_key_identifier,
MBEDTLS_LMOTS_I_KEY_ID_LEN);
memcpy(key + PUBLIC_KEY_Q_LEAF_ID_OFFSET,
ctx->params.q_leaf_identifier,
MBEDTLS_LMOTS_Q_LEAF_ID_LEN);
memcpy(key + PUBLIC_KEY_KEY_HASH_OFFSET, ctx->public_key,
MBEDTLS_LMOTS_N_HASH_LEN(ctx->params.type));
if (key_len != NULL) {
*key_len = MBEDTLS_LMOTS_PUBLIC_KEY_LEN(ctx->params.type);
}
return 0;
}
int mbedtls_lmots_calculate_public_key_candidate(const mbedtls_lmots_parameters_t *params,
const unsigned char *msg,
size_t msg_size,
const unsigned char *sig,
size_t sig_size,
unsigned char *out,
size_t out_size,
size_t *out_len)
{
unsigned char tmp_digit_array[MBEDTLS_LMOTS_P_SIG_DIGIT_COUNT_MAX];
unsigned char y_hashed_digits[MBEDTLS_LMOTS_P_SIG_DIGIT_COUNT_MAX][MBEDTLS_LMOTS_N_HASH_LEN_MAX];
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
if (msg == NULL && msg_size != 0) {
return MBEDTLS_ERR_LMS_BAD_INPUT_DATA;
}
if (sig_size != MBEDTLS_LMOTS_SIG_LEN(params->type) ||
out_size < MBEDTLS_LMOTS_N_HASH_LEN(params->type)) {
return MBEDTLS_ERR_LMS_BAD_INPUT_DATA;
}
ret = create_digit_array_with_checksum(params, msg, msg_size,
sig + MBEDTLS_LMOTS_SIG_C_RANDOM_OFFSET,
tmp_digit_array);
if (ret) {
return ret;
}
ret = hash_digit_array(params,
sig + MBEDTLS_LMOTS_SIG_SIGNATURE_OFFSET(params->type),
tmp_digit_array, NULL, (unsigned char *) y_hashed_digits);
if (ret) {
return ret;
}
ret = public_key_from_hashed_digit_array(params,
(unsigned char *) y_hashed_digits,
out);
if (ret) {
return ret;
}
if (out_len != NULL) {
*out_len = MBEDTLS_LMOTS_N_HASH_LEN(params->type);
}
return 0;
}
int mbedtls_lmots_verify(const mbedtls_lmots_public_t *ctx,
const unsigned char *msg, size_t msg_size,
const unsigned char *sig, size_t sig_size)
{
unsigned char Kc_public_key_candidate[MBEDTLS_LMOTS_N_HASH_LEN_MAX];
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
if (msg == NULL && msg_size != 0) {
return MBEDTLS_ERR_LMS_BAD_INPUT_DATA;
}
if (!ctx->have_public_key) {
return MBEDTLS_ERR_LMS_BAD_INPUT_DATA;
}
if (ctx->params.type != MBEDTLS_LMOTS_SHA256_N32_W8) {
return MBEDTLS_ERR_LMS_BAD_INPUT_DATA;
}
if (sig_size < MBEDTLS_LMOTS_SIG_TYPE_OFFSET + MBEDTLS_LMOTS_TYPE_LEN) {
return MBEDTLS_ERR_LMS_VERIFY_FAILED;
}
if (MBEDTLS_GET_UINT32_BE(sig, MBEDTLS_LMOTS_SIG_TYPE_OFFSET) != MBEDTLS_LMOTS_SHA256_N32_W8) {
return MBEDTLS_ERR_LMS_VERIFY_FAILED;
}
ret = mbedtls_lmots_calculate_public_key_candidate(&ctx->params,
msg, msg_size, sig, sig_size,
Kc_public_key_candidate,
MBEDTLS_LMOTS_N_HASH_LEN(ctx->params.type),
NULL);
if (ret) {
return MBEDTLS_ERR_LMS_VERIFY_FAILED;
}
if (memcmp(&Kc_public_key_candidate, ctx->public_key,
sizeof(ctx->public_key))) {
return MBEDTLS_ERR_LMS_VERIFY_FAILED;
}
return 0;
}
#if defined(MBEDTLS_LMS_PRIVATE)
void mbedtls_lmots_private_init(mbedtls_lmots_private_t *ctx)
{
memset(ctx, 0, sizeof(*ctx));
}
void mbedtls_lmots_private_free(mbedtls_lmots_private_t *ctx)
{
if (ctx == NULL) {
return;
}
mbedtls_platform_zeroize(ctx,
sizeof(*ctx));
}
int mbedtls_lmots_generate_private_key(mbedtls_lmots_private_t *ctx,
mbedtls_lmots_algorithm_type_t type,
const unsigned char I_key_identifier[MBEDTLS_LMOTS_I_KEY_ID_LEN],
uint32_t q_leaf_identifier,
const unsigned char *seed,
size_t seed_size)
{
psa_hash_operation_t op = PSA_HASH_OPERATION_INIT;
psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
size_t output_hash_len;
unsigned int i_digit_idx;
unsigned char i_digit_idx_bytes[2];
unsigned char const_bytes[1] = { 0xFF };
if (ctx->have_private_key) {
return MBEDTLS_ERR_LMS_BAD_INPUT_DATA;
}
if (type != MBEDTLS_LMOTS_SHA256_N32_W8) {
return MBEDTLS_ERR_LMS_BAD_INPUT_DATA;
}
ctx->params.type = type;
memcpy(ctx->params.I_key_identifier,
I_key_identifier,
sizeof(ctx->params.I_key_identifier));
MBEDTLS_PUT_UINT32_BE(q_leaf_identifier, ctx->params.q_leaf_identifier, 0);
for (i_digit_idx = 0;
i_digit_idx < MBEDTLS_LMOTS_P_SIG_DIGIT_COUNT(ctx->params.type);
i_digit_idx++) {
status = psa_hash_setup(&op, PSA_ALG_SHA_256);
if (status != PSA_SUCCESS) {
goto exit;
}
status = psa_hash_update(&op,
ctx->params.I_key_identifier,
sizeof(ctx->params.I_key_identifier));
if (status != PSA_SUCCESS) {
goto exit;
}
status = psa_hash_update(&op,
ctx->params.q_leaf_identifier,
MBEDTLS_LMOTS_Q_LEAF_ID_LEN);
if (status != PSA_SUCCESS) {
goto exit;
}
MBEDTLS_PUT_UINT16_BE(i_digit_idx, i_digit_idx_bytes, 0);
status = psa_hash_update(&op, i_digit_idx_bytes, I_DIGIT_IDX_LEN);
if (status != PSA_SUCCESS) {
goto exit;
}
status = psa_hash_update(&op, const_bytes, sizeof(const_bytes));
if (status != PSA_SUCCESS) {
goto exit;
}
status = psa_hash_update(&op, seed, seed_size);
if (status != PSA_SUCCESS) {
goto exit;
}
status = psa_hash_finish(&op,
ctx->private_key[i_digit_idx],
MBEDTLS_LMOTS_N_HASH_LEN(ctx->params.type),
&output_hash_len);
if (status != PSA_SUCCESS) {
goto exit;
}
psa_hash_abort(&op);
}
ctx->have_private_key = 1;
exit:
psa_hash_abort(&op);
return PSA_TO_MBEDTLS_ERR(status);
}
int mbedtls_lmots_calculate_public_key(mbedtls_lmots_public_t *ctx,
const mbedtls_lmots_private_t *priv_ctx)
{
unsigned char y_hashed_digits[MBEDTLS_LMOTS_P_SIG_DIGIT_COUNT_MAX][MBEDTLS_LMOTS_N_HASH_LEN_MAX];
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
/* Check that a private key is loaded */
if (!priv_ctx->have_private_key) {
return MBEDTLS_ERR_LMS_BAD_INPUT_DATA;
}
ret = hash_digit_array(&priv_ctx->params,
(unsigned char *) priv_ctx->private_key, NULL,
NULL, (unsigned char *) y_hashed_digits);
if (ret) {
goto exit;
}
ret = public_key_from_hashed_digit_array(&priv_ctx->params,
(unsigned char *) y_hashed_digits,
ctx->public_key);
if (ret) {
goto exit;
}
memcpy(&ctx->params, &priv_ctx->params,
sizeof(ctx->params));
ctx->have_public_key = 1;
exit:
mbedtls_platform_zeroize(y_hashed_digits, sizeof(y_hashed_digits));
return ret;
}
int mbedtls_lmots_sign(mbedtls_lmots_private_t *ctx,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng, const unsigned char *msg, size_t msg_size,
unsigned char *sig, size_t sig_size, size_t *sig_len)
{
unsigned char tmp_digit_array[MBEDTLS_LMOTS_P_SIG_DIGIT_COUNT_MAX];
/* Create a temporary buffer to prepare the signature in. This allows us to
* finish creating a signature (ensuring the process doesn't fail), and then
* erase the private key **before** writing any data into the sig parameter
* buffer. If data were directly written into the sig buffer, it might leak
* a partial signature on failure, which effectively compromises the private
* key.
*/
unsigned char tmp_sig[MBEDTLS_LMOTS_P_SIG_DIGIT_COUNT_MAX][MBEDTLS_LMOTS_N_HASH_LEN_MAX];
unsigned char tmp_c_random[MBEDTLS_LMOTS_N_HASH_LEN_MAX];
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
if (msg == NULL && msg_size != 0) {
return MBEDTLS_ERR_LMS_BAD_INPUT_DATA;
}
if (sig_size < MBEDTLS_LMOTS_SIG_LEN(ctx->params.type)) {
return MBEDTLS_ERR_LMS_BUFFER_TOO_SMALL;
}
/* Check that a private key is loaded */
if (!ctx->have_private_key) {
return MBEDTLS_ERR_LMS_BAD_INPUT_DATA;
}
ret = f_rng(p_rng, tmp_c_random,
MBEDTLS_LMOTS_N_HASH_LEN(ctx->params.type));
if (ret) {
return ret;
}
ret = create_digit_array_with_checksum(&ctx->params,
msg, msg_size,
tmp_c_random,
tmp_digit_array);
if (ret) {
goto exit;
}
ret = hash_digit_array(&ctx->params, (unsigned char *) ctx->private_key,
NULL, tmp_digit_array, (unsigned char *) tmp_sig);
if (ret) {
goto exit;
}
MBEDTLS_PUT_UINT32_BE(ctx->params.type, sig, MBEDTLS_LMOTS_SIG_TYPE_OFFSET);
/* Test hook to check if sig is being written to before we invalidate the
* private key.
*/
#if defined(MBEDTLS_TEST_HOOKS)
if (mbedtls_lmots_sign_private_key_invalidated_hook != NULL) {
ret = (*mbedtls_lmots_sign_private_key_invalidated_hook)(sig);
if (ret != 0) {
return ret;
}
}
#endif /* defined(MBEDTLS_TEST_HOOKS) */
/* We've got a valid signature now, so it's time to make sure the private
* key can't be reused.
*/
ctx->have_private_key = 0;
mbedtls_platform_zeroize(ctx->private_key,
sizeof(ctx->private_key));
memcpy(sig + MBEDTLS_LMOTS_SIG_C_RANDOM_OFFSET, tmp_c_random,
MBEDTLS_LMOTS_C_RANDOM_VALUE_LEN(ctx->params.type));
memcpy(sig + MBEDTLS_LMOTS_SIG_SIGNATURE_OFFSET(ctx->params.type), tmp_sig,
MBEDTLS_LMOTS_P_SIG_DIGIT_COUNT(ctx->params.type)
* MBEDTLS_LMOTS_N_HASH_LEN(ctx->params.type));
if (sig_len != NULL) {
*sig_len = MBEDTLS_LMOTS_SIG_LEN(ctx->params.type);
}
ret = 0;
exit:
mbedtls_platform_zeroize(tmp_digit_array, sizeof(tmp_digit_array));
mbedtls_platform_zeroize(tmp_sig, sizeof(tmp_sig));
return ret;
}
#endif /* defined(MBEDTLS_LMS_PRIVATE) */
#endif /* defined(MBEDTLS_LMS_C) */
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