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41966d74332c965688e07ab4ea6685eae9a13858
mbedtls/library/ecdsa.c
Chien Wong 0118a1d712 Fix a few unchecked return values 
Signed-off-by: Chien Wong <m@xv97.com>
2023-08-17 22:13:11 +08:00

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/*
* Elliptic curve DSA
*
* Copyright The Mbed TLS Contributors
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* References:
*
* SEC1 https://www.secg.org/sec1-v2.pdf
*/
#include "common.h"
#if defined(MBEDTLS_ECDSA_C)
#include "mbedtls/ecdsa.h"
#include "mbedtls/asn1write.h"
#include <string.h>
#if defined(MBEDTLS_ECDSA_DETERMINISTIC)
#include "mbedtls/hmac_drbg.h"
#endif
#include "mbedtls/platform.h"
#include "mbedtls/platform_util.h"
#include "mbedtls/error.h"
/* Parameter validation macros based on platform_util.h */
#define ECDSA_VALIDATE_RET(cond) \
MBEDTLS_INTERNAL_VALIDATE_RET(cond, MBEDTLS_ERR_ECP_BAD_INPUT_DATA)
#define ECDSA_VALIDATE(cond) \
MBEDTLS_INTERNAL_VALIDATE(cond)
#if defined(MBEDTLS_ECP_RESTARTABLE)
/*
* Sub-context for ecdsa_verify()
*/
struct mbedtls_ecdsa_restart_ver {
mbedtls_mpi u1, u2; /* intermediate values */
enum { /* what to do next? */
ecdsa_ver_init = 0, /* getting started */
ecdsa_ver_muladd, /* muladd step */
} state;
};
/*
* Init verify restart sub-context
*/
static void ecdsa_restart_ver_init(mbedtls_ecdsa_restart_ver_ctx *ctx)
{
mbedtls_mpi_init(&ctx->u1);
mbedtls_mpi_init(&ctx->u2);
ctx->state = ecdsa_ver_init;
}
/*
* Free the components of a verify restart sub-context
*/
static void ecdsa_restart_ver_free(mbedtls_ecdsa_restart_ver_ctx *ctx)
{
if (ctx == NULL) {
return;
}
mbedtls_mpi_free(&ctx->u1);
mbedtls_mpi_free(&ctx->u2);
ecdsa_restart_ver_init(ctx);
}
/*
* Sub-context for ecdsa_sign()
*/
struct mbedtls_ecdsa_restart_sig {
int sign_tries;
int key_tries;
mbedtls_mpi k; /* per-signature random */
mbedtls_mpi r; /* r value */
enum { /* what to do next? */
ecdsa_sig_init = 0, /* getting started */
ecdsa_sig_mul, /* doing ecp_mul() */
ecdsa_sig_modn, /* mod N computations */
} state;
};
/*
* Init verify sign sub-context
*/
static void ecdsa_restart_sig_init(mbedtls_ecdsa_restart_sig_ctx *ctx)
{
ctx->sign_tries = 0;
ctx->key_tries = 0;
mbedtls_mpi_init(&ctx->k);
mbedtls_mpi_init(&ctx->r);
ctx->state = ecdsa_sig_init;
}
/*
* Free the components of a sign restart sub-context
*/
static void ecdsa_restart_sig_free(mbedtls_ecdsa_restart_sig_ctx *ctx)
{
if (ctx == NULL) {
return;
}
mbedtls_mpi_free(&ctx->k);
mbedtls_mpi_free(&ctx->r);
}
#if defined(MBEDTLS_ECDSA_DETERMINISTIC)
/*
* Sub-context for ecdsa_sign_det()
*/
struct mbedtls_ecdsa_restart_det {
mbedtls_hmac_drbg_context rng_ctx; /* DRBG state */
enum { /* what to do next? */
ecdsa_det_init = 0, /* getting started */
ecdsa_det_sign, /* make signature */
} state;
};
/*
* Init verify sign_det sub-context
*/
static void ecdsa_restart_det_init(mbedtls_ecdsa_restart_det_ctx *ctx)
{
mbedtls_hmac_drbg_init(&ctx->rng_ctx);
ctx->state = ecdsa_det_init;
}
/*
* Free the components of a sign_det restart sub-context
*/
static void ecdsa_restart_det_free(mbedtls_ecdsa_restart_det_ctx *ctx)
{
if (ctx == NULL) {
return;
}
mbedtls_hmac_drbg_free(&ctx->rng_ctx);
ecdsa_restart_det_init(ctx);
}
#endif /* MBEDTLS_ECDSA_DETERMINISTIC */
#define ECDSA_RS_ECP (rs_ctx == NULL ? NULL : &rs_ctx->ecp)
/* Utility macro for checking and updating ops budget */
#define ECDSA_BUDGET(ops) \
MBEDTLS_MPI_CHK(mbedtls_ecp_check_budget(grp, ECDSA_RS_ECP, ops));
/* Call this when entering a function that needs its own sub-context */
#define ECDSA_RS_ENTER(SUB) do { \
/* reset ops count for this call if top-level */ \
if (rs_ctx != NULL && rs_ctx->ecp.depth++ == 0) \
rs_ctx->ecp.ops_done = 0; \
\
/* set up our own sub-context if needed */ \
if (mbedtls_ecp_restart_is_enabled() && \
rs_ctx != NULL && rs_ctx->SUB == NULL) \
{ \
rs_ctx->SUB = mbedtls_calloc(1, sizeof(*rs_ctx->SUB)); \
if (rs_ctx->SUB == NULL) \
return MBEDTLS_ERR_ECP_ALLOC_FAILED; \
\
ecdsa_restart_## SUB ##_init(rs_ctx->SUB); \
} \
} while (0)
/* Call this when leaving a function that needs its own sub-context */
#define ECDSA_RS_LEAVE(SUB) do { \
/* clear our sub-context when not in progress (done or error) */ \
if (rs_ctx != NULL && rs_ctx->SUB != NULL && \
ret != MBEDTLS_ERR_ECP_IN_PROGRESS) \
{ \
ecdsa_restart_## SUB ##_free(rs_ctx->SUB); \
mbedtls_free(rs_ctx->SUB); \
rs_ctx->SUB = NULL; \
} \
\
if (rs_ctx != NULL) \
rs_ctx->ecp.depth--; \
} while (0)
#else /* MBEDTLS_ECP_RESTARTABLE */
#define ECDSA_RS_ECP NULL
#define ECDSA_BUDGET(ops) /* no-op; for compatibility */
#define ECDSA_RS_ENTER(SUB) (void) rs_ctx
#define ECDSA_RS_LEAVE(SUB) (void) rs_ctx
#endif /* MBEDTLS_ECP_RESTARTABLE */
#if defined(MBEDTLS_ECDSA_DETERMINISTIC) || \
!defined(MBEDTLS_ECDSA_SIGN_ALT) || \
!defined(MBEDTLS_ECDSA_VERIFY_ALT)
/*
* Derive a suitable integer for group grp from a buffer of length len
* SEC1 4.1.3 step 5 aka SEC1 4.1.4 step 3
*/
static int derive_mpi(const mbedtls_ecp_group *grp, mbedtls_mpi *x,
const unsigned char *buf, size_t blen)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t n_size = (grp->nbits + 7) / 8;
size_t use_size = blen > n_size ? n_size : blen;
MBEDTLS_MPI_CHK(mbedtls_mpi_read_binary(x, buf, use_size));
if (use_size * 8 > grp->nbits) {
MBEDTLS_MPI_CHK(mbedtls_mpi_shift_r(x, use_size * 8 - grp->nbits));
}
/* While at it, reduce modulo N */
if (mbedtls_mpi_cmp_mpi(x, &grp->N) >= 0) {
MBEDTLS_MPI_CHK(mbedtls_mpi_sub_mpi(x, x, &grp->N));
}
cleanup:
return ret;
}
#endif /* ECDSA_DETERMINISTIC || !ECDSA_SIGN_ALT || !ECDSA_VERIFY_ALT */
#if !defined(MBEDTLS_ECDSA_SIGN_ALT)
/*
* Compute ECDSA signature of a hashed message (SEC1 4.1.3)
* Obviously, compared to SEC1 4.1.3, we skip step 4 (hash message)
*/
static int ecdsa_sign_restartable(mbedtls_ecp_group *grp,
mbedtls_mpi *r, mbedtls_mpi *s,
const mbedtls_mpi *d, const unsigned char *buf, size_t blen,
int (*f_rng)(void *, unsigned char *, size_t), void *p_rng,
int (*f_rng_blind)(void *, unsigned char *, size_t),
void *p_rng_blind,
mbedtls_ecdsa_restart_ctx *rs_ctx)
{
int ret, key_tries, sign_tries;
int *p_sign_tries = &sign_tries, *p_key_tries = &key_tries;
mbedtls_ecp_point R;
mbedtls_mpi k, e, t;
mbedtls_mpi *pk = &k, *pr = r;
/* Fail cleanly on curves such as Curve25519 that can't be used for ECDSA */
if (!mbedtls_ecdsa_can_do(grp->id) || grp->N.p == NULL) {
return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
}
/* Make sure d is in range 1..n-1 */
if (mbedtls_mpi_cmp_int(d, 1) < 0 || mbedtls_mpi_cmp_mpi(d, &grp->N) >= 0) {
return MBEDTLS_ERR_ECP_INVALID_KEY;
}
mbedtls_ecp_point_init(&R);
mbedtls_mpi_init(&k); mbedtls_mpi_init(&e); mbedtls_mpi_init(&t);
ECDSA_RS_ENTER(sig);
#if defined(MBEDTLS_ECP_RESTARTABLE)
if (rs_ctx != NULL && rs_ctx->sig != NULL) {
/* redirect to our context */
p_sign_tries = &rs_ctx->sig->sign_tries;
p_key_tries = &rs_ctx->sig->key_tries;
pk = &rs_ctx->sig->k;
pr = &rs_ctx->sig->r;
/* jump to current step */
if (rs_ctx->sig->state == ecdsa_sig_mul) {
goto mul;
}
if (rs_ctx->sig->state == ecdsa_sig_modn) {
goto modn;
}
}
#endif /* MBEDTLS_ECP_RESTARTABLE */
*p_sign_tries = 0;
do {
if ((*p_sign_tries)++ > 10) {
ret = MBEDTLS_ERR_ECP_RANDOM_FAILED;
goto cleanup;
}
/*
* Steps 1-3: generate a suitable ephemeral keypair
* and set r = xR mod n
*/
*p_key_tries = 0;
do {
if ((*p_key_tries)++ > 10) {
ret = MBEDTLS_ERR_ECP_RANDOM_FAILED;
goto cleanup;
}
MBEDTLS_MPI_CHK(mbedtls_ecp_gen_privkey(grp, pk, f_rng, p_rng));
#if defined(MBEDTLS_ECP_RESTARTABLE)
if (rs_ctx != NULL && rs_ctx->sig != NULL) {
rs_ctx->sig->state = ecdsa_sig_mul;
}
mul:
#endif
MBEDTLS_MPI_CHK(mbedtls_ecp_mul_restartable(grp, &R, pk, &grp->G,
f_rng_blind,
p_rng_blind,
ECDSA_RS_ECP));
MBEDTLS_MPI_CHK(mbedtls_mpi_mod_mpi(pr, &R.X, &grp->N));
} while (mbedtls_mpi_cmp_int(pr, 0) == 0);
#if defined(MBEDTLS_ECP_RESTARTABLE)
if (rs_ctx != NULL && rs_ctx->sig != NULL) {
rs_ctx->sig->state = ecdsa_sig_modn;
}
modn:
#endif
/*
* Accounting for everything up to the end of the loop
* (step 6, but checking now avoids saving e and t)
*/
ECDSA_BUDGET(MBEDTLS_ECP_OPS_INV + 4);
/*
* Step 5: derive MPI from hashed message
*/
MBEDTLS_MPI_CHK(derive_mpi(grp, &e, buf, blen));
/*
* Generate a random value to blind inv_mod in next step,
* avoiding a potential timing leak.
*/
MBEDTLS_MPI_CHK(mbedtls_ecp_gen_privkey(grp, &t, f_rng_blind,
p_rng_blind));
/*
* Step 6: compute s = (e + r * d) / k = t (e + rd) / (kt) mod n
*/
MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(s, pr, d));
MBEDTLS_MPI_CHK(mbedtls_mpi_add_mpi(&e, &e, s));
MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(&e, &e, &t));
MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(pk, pk, &t));
MBEDTLS_MPI_CHK(mbedtls_mpi_mod_mpi(pk, pk, &grp->N));
MBEDTLS_MPI_CHK(mbedtls_mpi_inv_mod(s, pk, &grp->N));
MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(s, s, &e));
MBEDTLS_MPI_CHK(mbedtls_mpi_mod_mpi(s, s, &grp->N));
} while (mbedtls_mpi_cmp_int(s, 0) == 0);
#if defined(MBEDTLS_ECP_RESTARTABLE)
if (rs_ctx != NULL && rs_ctx->sig != NULL) {
MBEDTLS_MPI_CHK(mbedtls_mpi_copy(r, pr));
}
#endif
cleanup:
mbedtls_ecp_point_free(&R);
mbedtls_mpi_free(&k); mbedtls_mpi_free(&e); mbedtls_mpi_free(&t);
ECDSA_RS_LEAVE(sig);
return ret;
}
int mbedtls_ecdsa_can_do(mbedtls_ecp_group_id gid)
{
switch (gid) {
#ifdef MBEDTLS_ECP_DP_CURVE25519_ENABLED
case MBEDTLS_ECP_DP_CURVE25519: return 0;
#endif
#ifdef MBEDTLS_ECP_DP_CURVE448_ENABLED
case MBEDTLS_ECP_DP_CURVE448: return 0;
#endif
default: return 1;
}
}
/*
* Compute ECDSA signature of a hashed message
*/
int mbedtls_ecdsa_sign(mbedtls_ecp_group *grp, mbedtls_mpi *r, mbedtls_mpi *s,
const mbedtls_mpi *d, const unsigned char *buf, size_t blen,
int (*f_rng)(void *, unsigned char *, size_t), void *p_rng)
{
ECDSA_VALIDATE_RET(grp != NULL);
ECDSA_VALIDATE_RET(r != NULL);
ECDSA_VALIDATE_RET(s != NULL);
ECDSA_VALIDATE_RET(d != NULL);
ECDSA_VALIDATE_RET(f_rng != NULL);
ECDSA_VALIDATE_RET(buf != NULL || blen == 0);
/* Use the same RNG for both blinding and ephemeral key generation */
return ecdsa_sign_restartable(grp, r, s, d, buf, blen,
f_rng, p_rng, f_rng, p_rng, NULL);
}
#endif /* !MBEDTLS_ECDSA_SIGN_ALT */
#if defined(MBEDTLS_ECDSA_DETERMINISTIC)
/*
* Deterministic signature wrapper
*/
static int ecdsa_sign_det_restartable(mbedtls_ecp_group *grp,
mbedtls_mpi *r, mbedtls_mpi *s,
const mbedtls_mpi *d, const unsigned char *buf, size_t blen,
mbedtls_md_type_t md_alg,
int (*f_rng_blind)(void *, unsigned char *, size_t),
void *p_rng_blind,
mbedtls_ecdsa_restart_ctx *rs_ctx)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
mbedtls_hmac_drbg_context rng_ctx;
mbedtls_hmac_drbg_context *p_rng = &rng_ctx;
unsigned char data[2 * MBEDTLS_ECP_MAX_BYTES];
size_t grp_len = (grp->nbits + 7) / 8;
const mbedtls_md_info_t *md_info;
mbedtls_mpi h;
if ((md_info = mbedtls_md_info_from_type(md_alg)) == NULL) {
return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
}
mbedtls_mpi_init(&h);
mbedtls_hmac_drbg_init(&rng_ctx);
ECDSA_RS_ENTER(det);
#if defined(MBEDTLS_ECP_RESTARTABLE)
if (rs_ctx != NULL && rs_ctx->det != NULL) {
/* redirect to our context */
p_rng = &rs_ctx->det->rng_ctx;
/* jump to current step */
if (rs_ctx->det->state == ecdsa_det_sign) {
goto sign;
}
}
#endif /* MBEDTLS_ECP_RESTARTABLE */
/* Use private key and message hash (reduced) to initialize HMAC_DRBG */
MBEDTLS_MPI_CHK(mbedtls_mpi_write_binary(d, data, grp_len));
MBEDTLS_MPI_CHK(derive_mpi(grp, &h, buf, blen));
MBEDTLS_MPI_CHK(mbedtls_mpi_write_binary(&h, data + grp_len, grp_len));
MBEDTLS_MPI_CHK(mbedtls_hmac_drbg_seed_buf(p_rng, md_info, data, 2 * grp_len));
#if defined(MBEDTLS_ECP_RESTARTABLE)
if (rs_ctx != NULL && rs_ctx->det != NULL) {
rs_ctx->det->state = ecdsa_det_sign;
}
sign:
#endif
#if defined(MBEDTLS_ECDSA_SIGN_ALT)
(void) f_rng_blind;
(void) p_rng_blind;
ret = mbedtls_ecdsa_sign(grp, r, s, d, buf, blen,
mbedtls_hmac_drbg_random, p_rng);
#else
if (f_rng_blind != NULL) {
ret = ecdsa_sign_restartable(grp, r, s, d, buf, blen,
mbedtls_hmac_drbg_random, p_rng,
f_rng_blind, p_rng_blind, rs_ctx);
} else {
mbedtls_hmac_drbg_context *p_rng_blind_det;
#if !defined(MBEDTLS_ECP_RESTARTABLE)
/*
* To avoid reusing rng_ctx and risking incorrect behavior we seed a
* second HMAC-DRBG with the same seed. We also apply a label to avoid
* reusing the bits of the ephemeral key for blinding and eliminate the
* risk that they leak this way.
*/
const char *blind_label = "BLINDING CONTEXT";
mbedtls_hmac_drbg_context rng_ctx_blind;
mbedtls_hmac_drbg_init(&rng_ctx_blind);
p_rng_blind_det = &rng_ctx_blind;
mbedtls_hmac_drbg_seed_buf(p_rng_blind_det, md_info,
data, 2 * grp_len);
ret = mbedtls_hmac_drbg_update_ret(p_rng_blind_det,
(const unsigned char *) blind_label,
strlen(blind_label));
if (ret != 0) {
mbedtls_hmac_drbg_free(&rng_ctx_blind);
goto cleanup;
}
#else
/*
* In the case of restartable computations we would either need to store
* the second RNG in the restart context too or set it up at every
* restart. The first option would penalize the correct application of
* the function and the second would defeat the purpose of the
* restartable feature.
*
* Therefore in this case we reuse the original RNG. This comes with the
* price that the resulting signature might not be a valid deterministic
* ECDSA signature with a very low probability (same magnitude as
* successfully guessing the private key). However even then it is still
* a valid ECDSA signature.
*/
p_rng_blind_det = p_rng;
#endif /* MBEDTLS_ECP_RESTARTABLE */
/*
* Since the output of the RNGs is always the same for the same key and
* message, this limits the efficiency of blinding and leaks information
* through side channels. After mbedtls_ecdsa_sign_det() is removed NULL
* won't be a valid value for f_rng_blind anymore. Therefore it should
* be checked by the caller and this branch and check can be removed.
*/
ret = ecdsa_sign_restartable(grp, r, s, d, buf, blen,
mbedtls_hmac_drbg_random, p_rng,
mbedtls_hmac_drbg_random, p_rng_blind_det,
rs_ctx);
#if !defined(MBEDTLS_ECP_RESTARTABLE)
mbedtls_hmac_drbg_free(&rng_ctx_blind);
#endif
}
#endif /* MBEDTLS_ECDSA_SIGN_ALT */
cleanup:
mbedtls_hmac_drbg_free(&rng_ctx);
mbedtls_mpi_free(&h);
ECDSA_RS_LEAVE(det);
return ret;
}
/*
* Deterministic signature wrappers
*/
#if !defined(MBEDTLS_DEPRECATED_REMOVED)
int mbedtls_ecdsa_sign_det(mbedtls_ecp_group *grp, mbedtls_mpi *r,
mbedtls_mpi *s, const mbedtls_mpi *d,
const unsigned char *buf, size_t blen,
mbedtls_md_type_t md_alg)
{
ECDSA_VALIDATE_RET(grp != NULL);
ECDSA_VALIDATE_RET(r != NULL);
ECDSA_VALIDATE_RET(s != NULL);
ECDSA_VALIDATE_RET(d != NULL);
ECDSA_VALIDATE_RET(buf != NULL || blen == 0);
return ecdsa_sign_det_restartable(grp, r, s, d, buf, blen, md_alg,
NULL, NULL, NULL);
}
#endif /* MBEDTLS_DEPRECATED_REMOVED */
int mbedtls_ecdsa_sign_det_ext(mbedtls_ecp_group *grp, mbedtls_mpi *r,
mbedtls_mpi *s, const mbedtls_mpi *d,
const unsigned char *buf, size_t blen,
mbedtls_md_type_t md_alg,
int (*f_rng_blind)(void *, unsigned char *,
size_t),
void *p_rng_blind)
{
ECDSA_VALIDATE_RET(grp != NULL);
ECDSA_VALIDATE_RET(r != NULL);
ECDSA_VALIDATE_RET(s != NULL);
ECDSA_VALIDATE_RET(d != NULL);
ECDSA_VALIDATE_RET(buf != NULL || blen == 0);
ECDSA_VALIDATE_RET(f_rng_blind != NULL);
return ecdsa_sign_det_restartable(grp, r, s, d, buf, blen, md_alg,
f_rng_blind, p_rng_blind, NULL);
}
#endif /* MBEDTLS_ECDSA_DETERMINISTIC */
#if !defined(MBEDTLS_ECDSA_VERIFY_ALT)
/*
* Verify ECDSA signature of hashed message (SEC1 4.1.4)
* Obviously, compared to SEC1 4.1.3, we skip step 2 (hash message)
*/
static int ecdsa_verify_restartable(mbedtls_ecp_group *grp,
const unsigned char *buf, size_t blen,
const mbedtls_ecp_point *Q,
const mbedtls_mpi *r, const mbedtls_mpi *s,
mbedtls_ecdsa_restart_ctx *rs_ctx)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
mbedtls_mpi e, s_inv, u1, u2;
mbedtls_ecp_point R;
mbedtls_mpi *pu1 = &u1, *pu2 = &u2;
mbedtls_ecp_point_init(&R);
mbedtls_mpi_init(&e); mbedtls_mpi_init(&s_inv);
mbedtls_mpi_init(&u1); mbedtls_mpi_init(&u2);
/* Fail cleanly on curves such as Curve25519 that can't be used for ECDSA */
if (!mbedtls_ecdsa_can_do(grp->id) || grp->N.p == NULL) {
return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
}
ECDSA_RS_ENTER(ver);
#if defined(MBEDTLS_ECP_RESTARTABLE)
if (rs_ctx != NULL && rs_ctx->ver != NULL) {
/* redirect to our context */
pu1 = &rs_ctx->ver->u1;
pu2 = &rs_ctx->ver->u2;
/* jump to current step */
if (rs_ctx->ver->state == ecdsa_ver_muladd) {
goto muladd;
}
}
#endif /* MBEDTLS_ECP_RESTARTABLE */
/*
* Step 1: make sure r and s are in range 1..n-1
*/
if (mbedtls_mpi_cmp_int(r, 1) < 0 || mbedtls_mpi_cmp_mpi(r, &grp->N) >= 0 ||
mbedtls_mpi_cmp_int(s, 1) < 0 || mbedtls_mpi_cmp_mpi(s, &grp->N) >= 0) {
ret = MBEDTLS_ERR_ECP_VERIFY_FAILED;
goto cleanup;
}
/*
* Step 3: derive MPI from hashed message
*/
MBEDTLS_MPI_CHK(derive_mpi(grp, &e, buf, blen));
/*
* Step 4: u1 = e / s mod n, u2 = r / s mod n
*/
ECDSA_BUDGET(MBEDTLS_ECP_OPS_CHK + MBEDTLS_ECP_OPS_INV + 2);
MBEDTLS_MPI_CHK(mbedtls_mpi_inv_mod(&s_inv, s, &grp->N));
MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(pu1, &e, &s_inv));
MBEDTLS_MPI_CHK(mbedtls_mpi_mod_mpi(pu1, pu1, &grp->N));
MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(pu2, r, &s_inv));
MBEDTLS_MPI_CHK(mbedtls_mpi_mod_mpi(pu2, pu2, &grp->N));
#if defined(MBEDTLS_ECP_RESTARTABLE)
if (rs_ctx != NULL && rs_ctx->ver != NULL) {
rs_ctx->ver->state = ecdsa_ver_muladd;
}
muladd:
#endif
/*
* Step 5: R = u1 G + u2 Q
*/
MBEDTLS_MPI_CHK(mbedtls_ecp_muladd_restartable(grp,
&R, pu1, &grp->G, pu2, Q, ECDSA_RS_ECP));
if (mbedtls_ecp_is_zero(&R)) {
ret = MBEDTLS_ERR_ECP_VERIFY_FAILED;
goto cleanup;
}
/*
* Step 6: convert xR to an integer (no-op)
* Step 7: reduce xR mod n (gives v)
*/
MBEDTLS_MPI_CHK(mbedtls_mpi_mod_mpi(&R.X, &R.X, &grp->N));
/*
* Step 8: check if v (that is, R.X) is equal to r
*/
if (mbedtls_mpi_cmp_mpi(&R.X, r) != 0) {
ret = MBEDTLS_ERR_ECP_VERIFY_FAILED;
goto cleanup;
}
cleanup:
mbedtls_ecp_point_free(&R);
mbedtls_mpi_free(&e); mbedtls_mpi_free(&s_inv);
mbedtls_mpi_free(&u1); mbedtls_mpi_free(&u2);
ECDSA_RS_LEAVE(ver);
return ret;
}
/*
* Verify ECDSA signature of hashed message
*/
int mbedtls_ecdsa_verify(mbedtls_ecp_group *grp,
const unsigned char *buf, size_t blen,
const mbedtls_ecp_point *Q,
const mbedtls_mpi *r,
const mbedtls_mpi *s)
{
ECDSA_VALIDATE_RET(grp != NULL);
ECDSA_VALIDATE_RET(Q != NULL);
ECDSA_VALIDATE_RET(r != NULL);
ECDSA_VALIDATE_RET(s != NULL);
ECDSA_VALIDATE_RET(buf != NULL || blen == 0);
return ecdsa_verify_restartable(grp, buf, blen, Q, r, s, NULL);
}
#endif /* !MBEDTLS_ECDSA_VERIFY_ALT */
/*
* Convert a signature (given by context) to ASN.1
*/
static int ecdsa_signature_to_asn1(const mbedtls_mpi *r, const mbedtls_mpi *s,
unsigned char *sig, size_t *slen)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
unsigned char buf[MBEDTLS_ECDSA_MAX_LEN] = { 0 };
unsigned char *p = buf + sizeof(buf);
size_t len = 0;
MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_mpi(&p, buf, s));
MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_mpi(&p, buf, r));
MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&p, buf, len));
MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(&p, buf,
MBEDTLS_ASN1_CONSTRUCTED |
MBEDTLS_ASN1_SEQUENCE));
memcpy(sig, p, len);
*slen = len;
return 0;
}
/*
* Compute and write signature
*/
int mbedtls_ecdsa_write_signature_restartable(mbedtls_ecdsa_context *ctx,
mbedtls_md_type_t md_alg,
const unsigned char *hash, size_t hlen,
unsigned char *sig, size_t *slen,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng,
mbedtls_ecdsa_restart_ctx *rs_ctx)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
mbedtls_mpi r, s;
ECDSA_VALIDATE_RET(ctx != NULL);
ECDSA_VALIDATE_RET(hash != NULL);
ECDSA_VALIDATE_RET(sig != NULL);
ECDSA_VALIDATE_RET(slen != NULL);
mbedtls_mpi_init(&r);
mbedtls_mpi_init(&s);
#if defined(MBEDTLS_ECDSA_DETERMINISTIC)
MBEDTLS_MPI_CHK(ecdsa_sign_det_restartable(&ctx->grp, &r, &s, &ctx->d,
hash, hlen, md_alg, f_rng,
p_rng, rs_ctx));
#else
(void) md_alg;
#if defined(MBEDTLS_ECDSA_SIGN_ALT)
(void) rs_ctx;
MBEDTLS_MPI_CHK(mbedtls_ecdsa_sign(&ctx->grp, &r, &s, &ctx->d,
hash, hlen, f_rng, p_rng));
#else
/* Use the same RNG for both blinding and ephemeral key generation */
MBEDTLS_MPI_CHK(ecdsa_sign_restartable(&ctx->grp, &r, &s, &ctx->d,
hash, hlen, f_rng, p_rng, f_rng,
p_rng, rs_ctx));
#endif /* MBEDTLS_ECDSA_SIGN_ALT */
#endif /* MBEDTLS_ECDSA_DETERMINISTIC */
MBEDTLS_MPI_CHK(ecdsa_signature_to_asn1(&r, &s, sig, slen));
cleanup:
mbedtls_mpi_free(&r);
mbedtls_mpi_free(&s);
return ret;
}
/*
* Compute and write signature
*/
int mbedtls_ecdsa_write_signature(mbedtls_ecdsa_context *ctx,
mbedtls_md_type_t md_alg,
const unsigned char *hash, size_t hlen,
unsigned char *sig, size_t *slen,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng)
{
ECDSA_VALIDATE_RET(ctx != NULL);
ECDSA_VALIDATE_RET(hash != NULL);
ECDSA_VALIDATE_RET(sig != NULL);
ECDSA_VALIDATE_RET(slen != NULL);
return mbedtls_ecdsa_write_signature_restartable(
ctx, md_alg, hash, hlen, sig, slen, f_rng, p_rng, NULL);
}
#if !defined(MBEDTLS_DEPRECATED_REMOVED) && \
defined(MBEDTLS_ECDSA_DETERMINISTIC)
int mbedtls_ecdsa_write_signature_det(mbedtls_ecdsa_context *ctx,
const unsigned char *hash, size_t hlen,
unsigned char *sig, size_t *slen,
mbedtls_md_type_t md_alg)
{
ECDSA_VALIDATE_RET(ctx != NULL);
ECDSA_VALIDATE_RET(hash != NULL);
ECDSA_VALIDATE_RET(sig != NULL);
ECDSA_VALIDATE_RET(slen != NULL);
return mbedtls_ecdsa_write_signature(ctx, md_alg, hash, hlen, sig, slen,
NULL, NULL);
}
#endif
/*
* Read and check signature
*/
int mbedtls_ecdsa_read_signature(mbedtls_ecdsa_context *ctx,
const unsigned char *hash, size_t hlen,
const unsigned char *sig, size_t slen)
{
ECDSA_VALIDATE_RET(ctx != NULL);
ECDSA_VALIDATE_RET(hash != NULL);
ECDSA_VALIDATE_RET(sig != NULL);
return mbedtls_ecdsa_read_signature_restartable(
ctx, hash, hlen, sig, slen, NULL);
}
/*
* Restartable read and check signature
*/
int mbedtls_ecdsa_read_signature_restartable(mbedtls_ecdsa_context *ctx,
const unsigned char *hash, size_t hlen,
const unsigned char *sig, size_t slen,
mbedtls_ecdsa_restart_ctx *rs_ctx)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
unsigned char *p = (unsigned char *) sig;
const unsigned char *end = sig + slen;
size_t len;
mbedtls_mpi r, s;
ECDSA_VALIDATE_RET(ctx != NULL);
ECDSA_VALIDATE_RET(hash != NULL);
ECDSA_VALIDATE_RET(sig != NULL);
mbedtls_mpi_init(&r);
mbedtls_mpi_init(&s);
if ((ret = mbedtls_asn1_get_tag(&p, end, &len,
MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE)) != 0) {
ret += MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
goto cleanup;
}
if (p + len != end) {
ret = MBEDTLS_ERROR_ADD(MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
MBEDTLS_ERR_ASN1_LENGTH_MISMATCH);
goto cleanup;
}
if ((ret = mbedtls_asn1_get_mpi(&p, end, &r)) != 0 ||
(ret = mbedtls_asn1_get_mpi(&p, end, &s)) != 0) {
ret += MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
goto cleanup;
}
#if defined(MBEDTLS_ECDSA_VERIFY_ALT)
(void) rs_ctx;
if ((ret = mbedtls_ecdsa_verify(&ctx->grp, hash, hlen,
&ctx->Q, &r, &s)) != 0) {
goto cleanup;
}
#else
if ((ret = ecdsa_verify_restartable(&ctx->grp, hash, hlen,
&ctx->Q, &r, &s, rs_ctx)) != 0) {
goto cleanup;
}
#endif /* MBEDTLS_ECDSA_VERIFY_ALT */
/* At this point we know that the buffer starts with a valid signature.
* Return 0 if the buffer just contains the signature, and a specific
* error code if the valid signature is followed by more data. */
if (p != end) {
ret = MBEDTLS_ERR_ECP_SIG_LEN_MISMATCH;
}
cleanup:
mbedtls_mpi_free(&r);
mbedtls_mpi_free(&s);
return ret;
}
#if !defined(MBEDTLS_ECDSA_GENKEY_ALT)
/*
* Generate key pair
*/
int mbedtls_ecdsa_genkey(mbedtls_ecdsa_context *ctx, mbedtls_ecp_group_id gid,
int (*f_rng)(void *, unsigned char *, size_t), void *p_rng)
{
int ret = 0;
ECDSA_VALIDATE_RET(ctx != NULL);
ECDSA_VALIDATE_RET(f_rng != NULL);
ret = mbedtls_ecp_group_load(&ctx->grp, gid);
if (ret != 0) {
return ret;
}
return mbedtls_ecp_gen_keypair(&ctx->grp, &ctx->d,
&ctx->Q, f_rng, p_rng);
}
#endif /* !MBEDTLS_ECDSA_GENKEY_ALT */
/*
* Set context from an mbedtls_ecp_keypair
*/
int mbedtls_ecdsa_from_keypair(mbedtls_ecdsa_context *ctx, const mbedtls_ecp_keypair *key)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
ECDSA_VALIDATE_RET(ctx != NULL);
ECDSA_VALIDATE_RET(key != NULL);
if ((ret = mbedtls_ecp_group_copy(&ctx->grp, &key->grp)) != 0 ||
(ret = mbedtls_mpi_copy(&ctx->d, &key->d)) != 0 ||
(ret = mbedtls_ecp_copy(&ctx->Q, &key->Q)) != 0) {
mbedtls_ecdsa_free(ctx);
}
return ret;
}
/*
* Initialize context
*/
void mbedtls_ecdsa_init(mbedtls_ecdsa_context *ctx)
{
ECDSA_VALIDATE(ctx != NULL);
mbedtls_ecp_keypair_init(ctx);
}
/*
* Free context
*/
void mbedtls_ecdsa_free(mbedtls_ecdsa_context *ctx)
{
if (ctx == NULL) {
return;
}
mbedtls_ecp_keypair_free(ctx);
}
#if defined(MBEDTLS_ECP_RESTARTABLE)
/*
* Initialize a restart context
*/
void mbedtls_ecdsa_restart_init(mbedtls_ecdsa_restart_ctx *ctx)
{
ECDSA_VALIDATE(ctx != NULL);
mbedtls_ecp_restart_init(&ctx->ecp);
ctx->ver = NULL;
ctx->sig = NULL;
#if defined(MBEDTLS_ECDSA_DETERMINISTIC)
ctx->det = NULL;
#endif
}
/*
* Free the components of a restart context
*/
void mbedtls_ecdsa_restart_free(mbedtls_ecdsa_restart_ctx *ctx)
{
if (ctx == NULL) {
return;
}
mbedtls_ecp_restart_free(&ctx->ecp);
ecdsa_restart_ver_free(ctx->ver);
mbedtls_free(ctx->ver);
ctx->ver = NULL;
ecdsa_restart_sig_free(ctx->sig);
mbedtls_free(ctx->sig);
ctx->sig = NULL;
#if defined(MBEDTLS_ECDSA_DETERMINISTIC)
ecdsa_restart_det_free(ctx->det);
mbedtls_free(ctx->det);
ctx->det = NULL;
#endif
}
#endif /* MBEDTLS_ECP_RESTARTABLE */
#endif /* MBEDTLS_ECDSA_C */
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