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/*
* Elliptic curve Diffie-Hellman
*
* Copyright The Mbed TLS Contributors
* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
*/
/*
* References:
*
* SEC1 https://www.secg.org/sec1-v2.pdf
* RFC 4492
*/
#include "common.h"
#if defined(MBEDTLS_ECDH_C)
#include "mbedtls/ecdh.h"
#include "mbedtls/platform_util.h"
#include "mbedtls/error.h"
#include <string.h>
#if defined(MBEDTLS_ECDH_LEGACY_CONTEXT)
typedef mbedtls_ecdh_context mbedtls_ecdh_context_mbed;
#endif
static mbedtls_ecp_group_id mbedtls_ecdh_grp_id(
const mbedtls_ecdh_context *ctx)
{
#if defined(MBEDTLS_ECDH_LEGACY_CONTEXT)
return ctx->grp.id;
#else
return ctx->grp_id;
#endif
}
int mbedtls_ecdh_can_do(mbedtls_ecp_group_id gid)
{
/* At this time, all groups support ECDH. */
(void) gid;
return 1;
}
#if !defined(MBEDTLS_ECDH_GEN_PUBLIC_ALT)
/*
* Generate public key (restartable version)
*
* Note: this internal function relies on its caller preserving the value of
* the output parameter 'd' across continuation calls. This would not be
* acceptable for a public function but is OK here as we control call sites.
*/
static int ecdh_gen_public_restartable(mbedtls_ecp_group *grp,
mbedtls_mpi *d, mbedtls_ecp_point *Q,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng,
mbedtls_ecp_restart_ctx *rs_ctx)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
int restarting = 0;
#if defined(MBEDTLS_ECP_RESTARTABLE)
restarting = (rs_ctx != NULL && rs_ctx->rsm != NULL);
#endif
/* If multiplication is in progress, we already generated a privkey */
if (!restarting) {
MBEDTLS_MPI_CHK(mbedtls_ecp_gen_privkey(grp, d, f_rng, p_rng));
}
MBEDTLS_MPI_CHK(mbedtls_ecp_mul_restartable(grp, Q, d, &grp->G,
f_rng, p_rng, rs_ctx));
cleanup:
return ret;
}
/*
* Generate public key
*/
int mbedtls_ecdh_gen_public(mbedtls_ecp_group *grp, mbedtls_mpi *d, mbedtls_ecp_point *Q,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng)
{
return ecdh_gen_public_restartable(grp, d, Q, f_rng, p_rng, NULL);
}
#endif /* !MBEDTLS_ECDH_GEN_PUBLIC_ALT */
#if !defined(MBEDTLS_ECDH_COMPUTE_SHARED_ALT)
/*
* Compute shared secret (SEC1 3.3.1)
*/
static int ecdh_compute_shared_restartable(mbedtls_ecp_group *grp,
mbedtls_mpi *z,
const mbedtls_ecp_point *Q, const mbedtls_mpi *d,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng,
mbedtls_ecp_restart_ctx *rs_ctx)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
mbedtls_ecp_point P;
mbedtls_ecp_point_init(&P);
MBEDTLS_MPI_CHK(mbedtls_ecp_mul_restartable(grp, &P, d, Q,
f_rng, p_rng, rs_ctx));
if (mbedtls_ecp_is_zero(&P)) {
ret = MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
goto cleanup;
}
MBEDTLS_MPI_CHK(mbedtls_mpi_copy(z, &P.X));
cleanup:
mbedtls_ecp_point_free(&P);
return ret;
}
/*
* Compute shared secret (SEC1 3.3.1)
*/
int mbedtls_ecdh_compute_shared(mbedtls_ecp_group *grp, mbedtls_mpi *z,
const mbedtls_ecp_point *Q, const mbedtls_mpi *d,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng)
{
return ecdh_compute_shared_restartable(grp, z, Q, d,
f_rng, p_rng, NULL);
}
#endif /* !MBEDTLS_ECDH_COMPUTE_SHARED_ALT */
static void ecdh_init_internal(mbedtls_ecdh_context_mbed *ctx)
{
mbedtls_ecp_group_init(&ctx->grp);
mbedtls_mpi_init(&ctx->d);
mbedtls_ecp_point_init(&ctx->Q);
mbedtls_ecp_point_init(&ctx->Qp);
mbedtls_mpi_init(&ctx->z);
#if defined(MBEDTLS_ECP_RESTARTABLE)
mbedtls_ecp_restart_init(&ctx->rs);
#endif
}
mbedtls_ecp_group_id mbedtls_ecdh_get_grp_id(mbedtls_ecdh_context *ctx)
{
#if defined(MBEDTLS_ECDH_LEGACY_CONTEXT)
return ctx->MBEDTLS_PRIVATE(grp).id;
#else
return ctx->MBEDTLS_PRIVATE(grp_id);
#endif
}
/*
* Initialize context
*/
void mbedtls_ecdh_init(mbedtls_ecdh_context *ctx)
{
#if defined(MBEDTLS_ECDH_LEGACY_CONTEXT)
ecdh_init_internal(ctx);
mbedtls_ecp_point_init(&ctx->Vi);
mbedtls_ecp_point_init(&ctx->Vf);
mbedtls_mpi_init(&ctx->_d);
#else
memset(ctx, 0, sizeof(mbedtls_ecdh_context));
ctx->var = MBEDTLS_ECDH_VARIANT_NONE;
#endif
ctx->point_format = MBEDTLS_ECP_PF_UNCOMPRESSED;
#if defined(MBEDTLS_ECP_RESTARTABLE)
ctx->restart_enabled = 0;
#endif
}
static int ecdh_setup_internal(mbedtls_ecdh_context_mbed *ctx,
mbedtls_ecp_group_id grp_id)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
ret = mbedtls_ecp_group_load(&ctx->grp, grp_id);
if (ret != 0) {
return MBEDTLS_ERR_ECP_FEATURE_UNAVAILABLE;
}
return 0;
}
/*
* Setup context
*/
int mbedtls_ecdh_setup(mbedtls_ecdh_context *ctx, mbedtls_ecp_group_id grp_id)
{
#if defined(MBEDTLS_ECDH_LEGACY_CONTEXT)
return ecdh_setup_internal(ctx, grp_id);
#else
switch (grp_id) {
#if defined(MBEDTLS_ECDH_VARIANT_EVEREST_ENABLED)
case MBEDTLS_ECP_DP_CURVE25519:
ctx->point_format = MBEDTLS_ECP_PF_COMPRESSED;
ctx->var = MBEDTLS_ECDH_VARIANT_EVEREST;
ctx->grp_id = grp_id;
return mbedtls_everest_setup(&ctx->ctx.everest_ecdh, grp_id);
#endif
default:
ctx->point_format = MBEDTLS_ECP_PF_UNCOMPRESSED;
ctx->var = MBEDTLS_ECDH_VARIANT_MBEDTLS_2_0;
ctx->grp_id = grp_id;
ecdh_init_internal(&ctx->ctx.mbed_ecdh);
return ecdh_setup_internal(&ctx->ctx.mbed_ecdh, grp_id);
}
#endif
}
static void ecdh_free_internal(mbedtls_ecdh_context_mbed *ctx)
{
mbedtls_ecp_group_free(&ctx->grp);
mbedtls_mpi_free(&ctx->d);
mbedtls_ecp_point_free(&ctx->Q);
mbedtls_ecp_point_free(&ctx->Qp);
mbedtls_mpi_free(&ctx->z);
#if defined(MBEDTLS_ECP_RESTARTABLE)
mbedtls_ecp_restart_free(&ctx->rs);
#endif
}
#if defined(MBEDTLS_ECP_RESTARTABLE)
/*
* Enable restartable operations for context
*/
void mbedtls_ecdh_enable_restart(mbedtls_ecdh_context *ctx)
{
ctx->restart_enabled = 1;
}
#endif
/*
* Free context
*/
void mbedtls_ecdh_free(mbedtls_ecdh_context *ctx)
{
if (ctx == NULL) {
return;
}
#if defined(MBEDTLS_ECDH_LEGACY_CONTEXT)
mbedtls_ecp_point_free(&ctx->Vi);
mbedtls_ecp_point_free(&ctx->Vf);
mbedtls_mpi_free(&ctx->_d);
ecdh_free_internal(ctx);
#else
switch (ctx->var) {
#if defined(MBEDTLS_ECDH_VARIANT_EVEREST_ENABLED)
case MBEDTLS_ECDH_VARIANT_EVEREST:
mbedtls_everest_free(&ctx->ctx.everest_ecdh);
break;
#endif
case MBEDTLS_ECDH_VARIANT_MBEDTLS_2_0:
ecdh_free_internal(&ctx->ctx.mbed_ecdh);
break;
default:
break;
}
ctx->point_format = MBEDTLS_ECP_PF_UNCOMPRESSED;
ctx->var = MBEDTLS_ECDH_VARIANT_NONE;
ctx->grp_id = MBEDTLS_ECP_DP_NONE;
#endif
}
static int ecdh_make_params_internal(mbedtls_ecdh_context_mbed *ctx,
size_t *olen, int point_format,
unsigned char *buf, size_t blen,
int (*f_rng)(void *,
unsigned char *,
size_t),
void *p_rng,
int restart_enabled)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t grp_len, pt_len;
#if defined(MBEDTLS_ECP_RESTARTABLE)
mbedtls_ecp_restart_ctx *rs_ctx = NULL;
#endif
if (ctx->grp.pbits == 0) {
return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
}
#if defined(MBEDTLS_ECP_RESTARTABLE)
if (restart_enabled) {
rs_ctx = &ctx->rs;
}
#else
(void) restart_enabled;
#endif
#if defined(MBEDTLS_ECP_RESTARTABLE)
if ((ret = ecdh_gen_public_restartable(&ctx->grp, &ctx->d, &ctx->Q,
f_rng, p_rng, rs_ctx)) != 0) {
return ret;
}
#else
if ((ret = mbedtls_ecdh_gen_public(&ctx->grp, &ctx->d, &ctx->Q,
f_rng, p_rng)) != 0) {
return ret;
}
#endif /* MBEDTLS_ECP_RESTARTABLE */
if ((ret = mbedtls_ecp_tls_write_group(&ctx->grp, &grp_len, buf,
blen)) != 0) {
return ret;
}
buf += grp_len;
blen -= grp_len;
if ((ret = mbedtls_ecp_tls_write_point(&ctx->grp, &ctx->Q, point_format,
&pt_len, buf, blen)) != 0) {
return ret;
}
*olen = grp_len + pt_len;
return 0;
}
/*
* Setup and write the ServerKeyExchange parameters (RFC 4492)
* struct {
* ECParameters curve_params;
* ECPoint public;
* } ServerECDHParams;
*/
int mbedtls_ecdh_make_params(mbedtls_ecdh_context *ctx, size_t *olen,
unsigned char *buf, size_t blen,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng)
{
int restart_enabled = 0;
#if defined(MBEDTLS_ECP_RESTARTABLE)
restart_enabled = ctx->restart_enabled;
#else
(void) restart_enabled;
#endif
#if defined(MBEDTLS_ECDH_LEGACY_CONTEXT)
return ecdh_make_params_internal(ctx, olen, ctx->point_format, buf, blen,
f_rng, p_rng, restart_enabled);
#else
switch (ctx->var) {
#if defined(MBEDTLS_ECDH_VARIANT_EVEREST_ENABLED)
case MBEDTLS_ECDH_VARIANT_EVEREST:
return mbedtls_everest_make_params(&ctx->ctx.everest_ecdh, olen,
buf, blen, f_rng, p_rng);
#endif
case MBEDTLS_ECDH_VARIANT_MBEDTLS_2_0:
return ecdh_make_params_internal(&ctx->ctx.mbed_ecdh, olen,
ctx->point_format, buf, blen,
f_rng, p_rng,
restart_enabled);
default:
return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
}
#endif
}
static int ecdh_read_params_internal(mbedtls_ecdh_context_mbed *ctx,
const unsigned char **buf,
const unsigned char *end)
{
return mbedtls_ecp_tls_read_point(&ctx->grp, &ctx->Qp, buf,
(size_t) (end - *buf));
}
/*
* Read the ServerKeyExchange parameters (RFC 4492)
* struct {
* ECParameters curve_params;
* ECPoint public;
* } ServerECDHParams;
*/
int mbedtls_ecdh_read_params(mbedtls_ecdh_context *ctx,
const unsigned char **buf,
const unsigned char *end)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
mbedtls_ecp_group_id grp_id;
if ((ret = mbedtls_ecp_tls_read_group_id(&grp_id, buf, (size_t) (end - *buf)))
!= 0) {
return ret;
}
if ((ret = mbedtls_ecdh_setup(ctx, grp_id)) != 0) {
return ret;
}
#if defined(MBEDTLS_ECDH_LEGACY_CONTEXT)
return ecdh_read_params_internal(ctx, buf, end);
#else
switch (ctx->var) {
#if defined(MBEDTLS_ECDH_VARIANT_EVEREST_ENABLED)
case MBEDTLS_ECDH_VARIANT_EVEREST:
return mbedtls_everest_read_params(&ctx->ctx.everest_ecdh,
buf, end);
#endif
case MBEDTLS_ECDH_VARIANT_MBEDTLS_2_0:
return ecdh_read_params_internal(&ctx->ctx.mbed_ecdh,
buf, end);
default:
return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
}
#endif
}
static int ecdh_get_params_internal(mbedtls_ecdh_context_mbed *ctx,
const mbedtls_ecp_keypair *key,
mbedtls_ecdh_side side)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
/* If it's not our key, just import the public part as Qp */
if (side == MBEDTLS_ECDH_THEIRS) {
return mbedtls_ecp_copy(&ctx->Qp, &key->Q);
}
/* Our key: import public (as Q) and private parts */
if (side != MBEDTLS_ECDH_OURS) {
return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
}
if ((ret = mbedtls_ecp_copy(&ctx->Q, &key->Q)) != 0 ||
(ret = mbedtls_mpi_copy(&ctx->d, &key->d)) != 0) {
return ret;
}
return 0;
}
/*
* Get parameters from a keypair
*/
int mbedtls_ecdh_get_params(mbedtls_ecdh_context *ctx,
const mbedtls_ecp_keypair *key,
mbedtls_ecdh_side side)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
if (side != MBEDTLS_ECDH_OURS && side != MBEDTLS_ECDH_THEIRS) {
return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
}
if (mbedtls_ecdh_grp_id(ctx) == MBEDTLS_ECP_DP_NONE) {
/* This is the first call to get_params(). Set up the context
* for use with the group. */
if ((ret = mbedtls_ecdh_setup(ctx, key->grp.id)) != 0) {
return ret;
}
} else {
/* This is not the first call to get_params(). Check that the
* current key's group is the same as the context's, which was set
* from the first key's group. */
if (mbedtls_ecdh_grp_id(ctx) != key->grp.id) {
return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
}
}
#if defined(MBEDTLS_ECDH_LEGACY_CONTEXT)
return ecdh_get_params_internal(ctx, key, side);
#else
switch (ctx->var) {
#if defined(MBEDTLS_ECDH_VARIANT_EVEREST_ENABLED)
case MBEDTLS_ECDH_VARIANT_EVEREST:
{
mbedtls_everest_ecdh_side s = side == MBEDTLS_ECDH_OURS ?
MBEDTLS_EVEREST_ECDH_OURS :
MBEDTLS_EVEREST_ECDH_THEIRS;
return mbedtls_everest_get_params(&ctx->ctx.everest_ecdh,
key, s);
}
#endif
case MBEDTLS_ECDH_VARIANT_MBEDTLS_2_0:
return ecdh_get_params_internal(&ctx->ctx.mbed_ecdh,
key, side);
default:
return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
}
#endif
}
static int ecdh_make_public_internal(mbedtls_ecdh_context_mbed *ctx,
size_t *olen, int point_format,
unsigned char *buf, size_t blen,
int (*f_rng)(void *,
unsigned char *,
size_t),
void *p_rng,
int restart_enabled)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
#if defined(MBEDTLS_ECP_RESTARTABLE)
mbedtls_ecp_restart_ctx *rs_ctx = NULL;
#endif
if (ctx->grp.pbits == 0) {
return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
}
#if defined(MBEDTLS_ECP_RESTARTABLE)
if (restart_enabled) {
rs_ctx = &ctx->rs;
}
#else
(void) restart_enabled;
#endif
#if defined(MBEDTLS_ECP_RESTARTABLE)
if ((ret = ecdh_gen_public_restartable(&ctx->grp, &ctx->d, &ctx->Q,
f_rng, p_rng, rs_ctx)) != 0) {
return ret;
}
#else
if ((ret = mbedtls_ecdh_gen_public(&ctx->grp, &ctx->d, &ctx->Q,
f_rng, p_rng)) != 0) {
return ret;
}
#endif /* MBEDTLS_ECP_RESTARTABLE */
return mbedtls_ecp_tls_write_point(&ctx->grp, &ctx->Q, point_format, olen,
buf, blen);
}
/*
* Setup and export the client public value
*/
int mbedtls_ecdh_make_public(mbedtls_ecdh_context *ctx, size_t *olen,
unsigned char *buf, size_t blen,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng)
{
int restart_enabled = 0;
#if defined(MBEDTLS_ECP_RESTARTABLE)
restart_enabled = ctx->restart_enabled;
#endif
#if defined(MBEDTLS_ECDH_LEGACY_CONTEXT)
return ecdh_make_public_internal(ctx, olen, ctx->point_format, buf, blen,
f_rng, p_rng, restart_enabled);
#else
switch (ctx->var) {
#if defined(MBEDTLS_ECDH_VARIANT_EVEREST_ENABLED)
case MBEDTLS_ECDH_VARIANT_EVEREST:
return mbedtls_everest_make_public(&ctx->ctx.everest_ecdh, olen,
buf, blen, f_rng, p_rng);
#endif
case MBEDTLS_ECDH_VARIANT_MBEDTLS_2_0:
return ecdh_make_public_internal(&ctx->ctx.mbed_ecdh, olen,
ctx->point_format, buf, blen,
f_rng, p_rng,
restart_enabled);
default:
return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
}
#endif
}
static int ecdh_read_public_internal(mbedtls_ecdh_context_mbed *ctx,
const unsigned char *buf, size_t blen)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
const unsigned char *p = buf;
if ((ret = mbedtls_ecp_tls_read_point(&ctx->grp, &ctx->Qp, &p,
blen)) != 0) {
return ret;
}
if ((size_t) (p - buf) != blen) {
return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
}
return 0;
}
/*
* Parse and import the client's public value
*/
int mbedtls_ecdh_read_public(mbedtls_ecdh_context *ctx,
const unsigned char *buf, size_t blen)
{
#if defined(MBEDTLS_ECDH_LEGACY_CONTEXT)
return ecdh_read_public_internal(ctx, buf, blen);
#else
switch (ctx->var) {
#if defined(MBEDTLS_ECDH_VARIANT_EVEREST_ENABLED)
case MBEDTLS_ECDH_VARIANT_EVEREST:
return mbedtls_everest_read_public(&ctx->ctx.everest_ecdh,
buf, blen);
#endif
case MBEDTLS_ECDH_VARIANT_MBEDTLS_2_0:
return ecdh_read_public_internal(&ctx->ctx.mbed_ecdh,
buf, blen);
default:
return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
}
#endif
}
static int ecdh_calc_secret_internal(mbedtls_ecdh_context_mbed *ctx,
size_t *olen, unsigned char *buf,
size_t blen,
int (*f_rng)(void *,
unsigned char *,
size_t),
void *p_rng,
int restart_enabled)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
#if defined(MBEDTLS_ECP_RESTARTABLE)
mbedtls_ecp_restart_ctx *rs_ctx = NULL;
#endif
if (ctx == NULL || ctx->grp.pbits == 0) {
return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
}
#if defined(MBEDTLS_ECP_RESTARTABLE)
if (restart_enabled) {
rs_ctx = &ctx->rs;
}
#else
(void) restart_enabled;
#endif
#if defined(MBEDTLS_ECP_RESTARTABLE)
if ((ret = ecdh_compute_shared_restartable(&ctx->grp, &ctx->z, &ctx->Qp,
&ctx->d, f_rng, p_rng,
rs_ctx)) != 0) {
return ret;
}
#else
if ((ret = mbedtls_ecdh_compute_shared(&ctx->grp, &ctx->z, &ctx->Qp,
&ctx->d, f_rng, p_rng)) != 0) {
return ret;
}
#endif /* MBEDTLS_ECP_RESTARTABLE */
if (mbedtls_mpi_size(&ctx->z) > blen) {
return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
}
*olen = ctx->grp.pbits / 8 + ((ctx->grp.pbits % 8) != 0);
if (mbedtls_ecp_get_type(&ctx->grp) == MBEDTLS_ECP_TYPE_MONTGOMERY) {
return mbedtls_mpi_write_binary_le(&ctx->z, buf, *olen);
}
return mbedtls_mpi_write_binary(&ctx->z, buf, *olen);
}
/*
* Derive and export the shared secret
*/
int mbedtls_ecdh_calc_secret(mbedtls_ecdh_context *ctx, size_t *olen,
unsigned char *buf, size_t blen,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng)
{
int restart_enabled = 0;
#if defined(MBEDTLS_ECP_RESTARTABLE)
restart_enabled = ctx->restart_enabled;
#endif
#if defined(MBEDTLS_ECDH_LEGACY_CONTEXT)
return ecdh_calc_secret_internal(ctx, olen, buf, blen, f_rng, p_rng,
restart_enabled);
#else
switch (ctx->var) {
#if defined(MBEDTLS_ECDH_VARIANT_EVEREST_ENABLED)
case MBEDTLS_ECDH_VARIANT_EVEREST:
return mbedtls_everest_calc_secret(&ctx->ctx.everest_ecdh, olen,
buf, blen, f_rng, p_rng);
#endif
case MBEDTLS_ECDH_VARIANT_MBEDTLS_2_0:
return ecdh_calc_secret_internal(&ctx->ctx.mbed_ecdh, olen, buf,
blen, f_rng, p_rng,
restart_enabled);
default:
return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
}
#endif
}
#endif /* MBEDTLS_ECDH_C */
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