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boringssl/crypto/trust_token/voprf.c

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/* Copyright (c) 2020, Google Inc.
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
#include <openssl/trust_token.h>
#include <openssl/bn.h>
#include <openssl/bytestring.h>
#include <openssl/ec.h>
#include <openssl/err.h>
#include <openssl/mem.h>
#include <openssl/nid.h>
#include <openssl/rand.h>
#include "../ec_extra/internal.h"
#include "../fipsmodule/ec/internal.h"
#include "internal.h"
typedef int (*hash_to_group_func_t)(const EC_GROUP *group, EC_RAW_POINT *out,
const uint8_t t[TRUST_TOKEN_NONCE_SIZE]);
typedef int (*hash_to_scalar_func_t)(const EC_GROUP *group, EC_SCALAR *out,
uint8_t *buf, size_t len);
typedef struct {
const EC_GROUP *group;
// hash_to_group implements the HashToGroup operation for VOPRFs. It returns
// one on success and zero on error.
hash_to_group_func_t hash_to_group;
// hash_to_scalar implements the HashToScalar operation for VOPRFs. It returns
// one on success and zero on error.
hash_to_scalar_func_t hash_to_scalar;
} VOPRF_METHOD;
static const uint8_t kDefaultAdditionalData[32] = {0};
static int voprf_init_method(VOPRF_METHOD *method, int curve_nid,
hash_to_group_func_t hash_to_group,
hash_to_scalar_func_t hash_to_scalar) {
method->group = EC_GROUP_new_by_curve_name(curve_nid);
if (method->group == NULL) {
return 0;
}
method->hash_to_group = hash_to_group;
method->hash_to_scalar = hash_to_scalar;
return 1;
}
static int cbb_add_point(CBB *out, const EC_GROUP *group,
const EC_AFFINE *point) {
size_t len =
ec_point_to_bytes(group, point, POINT_CONVERSION_UNCOMPRESSED, NULL, 0);
if (len == 0) {
return 0;
}
uint8_t *p;
return CBB_add_space(out, &p, len) &&
ec_point_to_bytes(group, point, POINT_CONVERSION_UNCOMPRESSED, p,
len) == len &&
CBB_flush(out);
}
static int cbs_get_point(CBS *cbs, const EC_GROUP *group, EC_AFFINE *out) {
CBS child;
size_t plen = 1 + 2 * BN_num_bytes(&group->field);
if (!CBS_get_bytes(cbs, &child, plen) ||
!ec_point_from_uncompressed(group, out, CBS_data(&child),
CBS_len(&child))) {
return 0;
}
return 1;
}
static int scalar_to_cbb(CBB *out, const EC_GROUP *group,
const EC_SCALAR *scalar) {
uint8_t *buf;
size_t scalar_len = BN_num_bytes(&group->order);
if (!CBB_add_space(out, &buf, scalar_len)) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE);
return 0;
}
ec_scalar_to_bytes(group, buf, &scalar_len, scalar);
return 1;
}
static int scalar_from_cbs(CBS *cbs, const EC_GROUP *group, EC_SCALAR *out) {
size_t scalar_len = BN_num_bytes(&group->order);
CBS tmp;
if (!CBS_get_bytes(cbs, &tmp, scalar_len)) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_DECODE_FAILURE);
return 0;
}
ec_scalar_from_bytes(group, out, CBS_data(&tmp), CBS_len(&tmp));
return 1;
}
static int voprf_generate_key(const VOPRF_METHOD *method, CBB *out_private,
CBB *out_public) {
const EC_GROUP *group = method->group;
EC_RAW_POINT pub;
EC_SCALAR priv;
EC_AFFINE pub_affine;
if (!ec_random_nonzero_scalar(group, &priv, kDefaultAdditionalData) ||
!ec_point_mul_scalar_base(group, &pub, &priv) ||
!ec_jacobian_to_affine(group, &pub_affine, &pub)) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_KEYGEN_FAILURE);
return 0;
}
if (!scalar_to_cbb(out_private, group, &priv) ||
!cbb_add_point(out_public, group, &pub_affine)) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_BUFFER_TOO_SMALL);
return 0;
}
return 1;
}
static int voprf_client_key_from_bytes(const VOPRF_METHOD *method,
TRUST_TOKEN_CLIENT_KEY *key,
const uint8_t *in, size_t len) {
const EC_GROUP *group = method->group;
if (!ec_point_from_uncompressed(group, &key->pubs, in, len)) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_DECODE_FAILURE);
return 0;
}
return 1;
}
static int voprf_issuer_key_from_bytes(const VOPRF_METHOD *method,
TRUST_TOKEN_ISSUER_KEY *key,
const uint8_t *in, size_t len) {
const EC_GROUP *group = method->group;
if (!ec_scalar_from_bytes(group, &key->xs, in, len)) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_DECODE_FAILURE);
return 0;
}
// Recompute the public key.
EC_RAW_POINT pub;
if (!ec_point_mul_scalar_base(group, &pub, &key->xs) ||
!ec_jacobian_to_affine(group, &key->pubs, &pub)) {
return 0;
}
return 1;
}
static STACK_OF(TRUST_TOKEN_PRETOKEN) *
voprf_blind(const VOPRF_METHOD *method, CBB *cbb, size_t count) {
const EC_GROUP *group = method->group;
STACK_OF(TRUST_TOKEN_PRETOKEN) *pretokens =
sk_TRUST_TOKEN_PRETOKEN_new_null();
if (pretokens == NULL) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE);
goto err;
}
for (size_t i = 0; i < count; i++) {
// Insert |pretoken| into |pretokens| early to simplify error-handling.
TRUST_TOKEN_PRETOKEN *pretoken =
OPENSSL_malloc(sizeof(TRUST_TOKEN_PRETOKEN));
if (pretoken == NULL ||
!sk_TRUST_TOKEN_PRETOKEN_push(pretokens, pretoken)) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE);
TRUST_TOKEN_PRETOKEN_free(pretoken);
goto err;
}
RAND_bytes(pretoken->t, sizeof(pretoken->t));
// We sample r in Montgomery form to simplify inverting.
EC_SCALAR r;
if (!ec_random_nonzero_scalar(group, &r,
kDefaultAdditionalData)) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE);
goto err;
}
// pretoken->r is rinv.
ec_scalar_inv0_montgomery(group, &pretoken->r, &r);
// Convert both out of Montgomery form.
ec_scalar_from_montgomery(group, &r, &r);
ec_scalar_from_montgomery(group, &pretoken->r, &pretoken->r);
// Tp is the blinded token in the VOPRF protocol.
EC_RAW_POINT P, Tp;
if (!method->hash_to_group(group, &P, pretoken->t) ||
!ec_point_mul_scalar(group, &Tp, &P, &r) ||
!ec_jacobian_to_affine(group, &pretoken->Tp, &Tp)) {
goto err;
}
if (!cbb_add_point(cbb, group, &pretoken->Tp)) {
goto err;
}
}
return pretokens;
err:
sk_TRUST_TOKEN_PRETOKEN_pop_free(pretokens, TRUST_TOKEN_PRETOKEN_free);
return NULL;
}
static int hash_to_scalar_dleq(const VOPRF_METHOD *method, EC_SCALAR *out,
const EC_AFFINE *X, const EC_AFFINE *T,
const EC_AFFINE *W, const EC_AFFINE *K0,
const EC_AFFINE *K1) {
static const uint8_t kDLEQLabel[] = "DLEQ";
int ok = 0;
CBB cbb;
CBB_zero(&cbb);
uint8_t *buf = NULL;
size_t len;
if (!CBB_init(&cbb, 0) ||
!CBB_add_bytes(&cbb, kDLEQLabel, sizeof(kDLEQLabel)) ||
!cbb_add_point(&cbb, method->group, X) ||
!cbb_add_point(&cbb, method->group, T) ||
!cbb_add_point(&cbb, method->group, W) ||
!cbb_add_point(&cbb, method->group, K0) ||
!cbb_add_point(&cbb, method->group, K1) ||
!CBB_finish(&cbb, &buf, &len) ||
!method->hash_to_scalar(method->group, out, buf, len)) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE);
goto err;
}
ok = 1;
err:
CBB_cleanup(&cbb);
OPENSSL_free(buf);
return ok;
}
static int hash_to_scalar_batch(const VOPRF_METHOD *method, EC_SCALAR *out,
const CBB *points, size_t index) {
static const uint8_t kDLEQBatchLabel[] = "DLEQ BATCH";
if (index > 0xffff) {
// The protocol supports only two-byte batches.
OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_OVERFLOW);
return 0;
}
int ok = 0;
CBB cbb;
CBB_zero(&cbb);
uint8_t *buf = NULL;
size_t len;
if (!CBB_init(&cbb, 0) ||
!CBB_add_bytes(&cbb, kDLEQBatchLabel, sizeof(kDLEQBatchLabel)) ||
!CBB_add_bytes(&cbb, CBB_data(points), CBB_len(points)) ||
!CBB_add_u16(&cbb, (uint16_t)index) ||
!CBB_finish(&cbb, &buf, &len) ||
!method->hash_to_scalar(method->group, out, buf, len)) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE);
goto err;
}
ok = 1;
err:
CBB_cleanup(&cbb);
OPENSSL_free(buf);
return ok;
}
static int dleq_generate(const VOPRF_METHOD *method, CBB *cbb,
const TRUST_TOKEN_ISSUER_KEY *priv,
const EC_RAW_POINT *T, const EC_RAW_POINT *W) {
const EC_GROUP *group = method->group;
enum {
idx_T,
idx_W,
idx_k0,
idx_k1,
num_idx,
};
EC_RAW_POINT jacobians[num_idx];
// Setup the DLEQ proof.
EC_SCALAR r;
if (// r <- Zp
!ec_random_nonzero_scalar(group, &r, kDefaultAdditionalData) ||
// k0;k1 = r*(G;T)
!ec_point_mul_scalar_base(group, &jacobians[idx_k0], &r) ||
!ec_point_mul_scalar(group, &jacobians[idx_k1], T, &r)) {
return 0;
}
EC_AFFINE affines[num_idx];
jacobians[idx_T] = *T;
jacobians[idx_W] = *W;
if (!ec_jacobian_to_affine_batch(group, affines, jacobians, num_idx)) {
return 0;
}
// Compute c = Hc(...).
EC_SCALAR c;
if (!hash_to_scalar_dleq(method, &c, &priv->pubs, &affines[idx_T],
&affines[idx_W], &affines[idx_k0],
&affines[idx_k1])) {
return 0;
}
EC_SCALAR c_mont;
ec_scalar_to_montgomery(group, &c_mont, &c);
// u = r + c*xs
EC_SCALAR u;
ec_scalar_mul_montgomery(group, &u, &priv->xs, &c_mont);
ec_scalar_add(group, &u, &r, &u);
// Store DLEQ proof in transcript.
if (!scalar_to_cbb(cbb, group, &c) ||
!scalar_to_cbb(cbb, group, &u)) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE);
return 0;
}
return 1;
}
static int mul_public_2(const EC_GROUP *group, EC_RAW_POINT *out,
const EC_RAW_POINT *p0, const EC_SCALAR *scalar0,
const EC_RAW_POINT *p1, const EC_SCALAR *scalar1) {
EC_RAW_POINT points[2] = {*p0, *p1};
EC_SCALAR scalars[2] = {*scalar0, *scalar1};
return ec_point_mul_scalar_public_batch(group, out, /*g_scalar=*/NULL, points,
scalars, 2);
}
static int dleq_verify(const VOPRF_METHOD *method, CBS *cbs,
const TRUST_TOKEN_CLIENT_KEY *pub, const EC_RAW_POINT *T,
const EC_RAW_POINT *W) {
const EC_GROUP *group = method->group;
enum {
idx_T,
idx_W,
idx_k0,
idx_k1,
num_idx,
};
EC_RAW_POINT jacobians[num_idx];
// Decode the DLEQ proof.
EC_SCALAR c, u;
if (!scalar_from_cbs(cbs, group, &c) ||
!scalar_from_cbs(cbs, group, &u)) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_DECODE_FAILURE);
return 0;
}
// k0;k1 = u*(G;T) - c*(pub;W)
EC_RAW_POINT pubs;
ec_affine_to_jacobian(group, &pubs, &pub->pubs);
EC_SCALAR minus_c;
ec_scalar_neg(group, &minus_c, &c);
if (!ec_point_mul_scalar_public(group, &jacobians[idx_k0], &u, &pubs,
&minus_c) ||
!mul_public_2(group, &jacobians[idx_k1], T, &u, W, &minus_c)) {
return 0;
}
// Check the DLEQ proof.
EC_AFFINE affines[num_idx];
jacobians[idx_T] = *T;
jacobians[idx_W] = *W;
if (!ec_jacobian_to_affine_batch(group, affines, jacobians, num_idx)) {
return 0;
}
// Compute c = Hc(...).
EC_SCALAR calculated;
if (!hash_to_scalar_dleq(method, &calculated, &pub->pubs, &affines[idx_T],
&affines[idx_W], &affines[idx_k0],
&affines[idx_k1])) {
return 0;
}
// c == calculated
if (!ec_scalar_equal_vartime(group, &c, &calculated)) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_INVALID_PROOF);
return 0;
}
return 1;
}
static int voprf_sign(const VOPRF_METHOD *method,
const TRUST_TOKEN_ISSUER_KEY *key, CBB *cbb, CBS *cbs,
size_t num_requested, size_t num_to_issue) {
const EC_GROUP *group = method->group;
if (num_requested < num_to_issue) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_INTERNAL_ERROR);
return 0;
}
if (num_to_issue > ((size_t)-1) / sizeof(EC_RAW_POINT) ||
num_to_issue > ((size_t)-1) / sizeof(EC_SCALAR)) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_OVERFLOW);
return 0;
}
int ret = 0;
EC_RAW_POINT *BTs = OPENSSL_malloc(num_to_issue * sizeof(EC_RAW_POINT));
EC_RAW_POINT *Zs = OPENSSL_malloc(num_to_issue * sizeof(EC_RAW_POINT));
EC_SCALAR *es = OPENSSL_malloc(num_to_issue * sizeof(EC_SCALAR));
CBB batch_cbb;
CBB_zero(&batch_cbb);
if (!BTs ||
!Zs ||
!es ||
!CBB_init(&batch_cbb, 0) ||
!cbb_add_point(&batch_cbb, method->group, &key->pubs)) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE);
goto err;
}
for (size_t i = 0; i < num_to_issue; i++) {
EC_AFFINE BT_affine, Z_affine;
EC_RAW_POINT BT, Z;
if (!cbs_get_point(cbs, group, &BT_affine)) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_DECODE_FAILURE);
goto err;
}
ec_affine_to_jacobian(group, &BT, &BT_affine);
if (!ec_point_mul_scalar(group, &Z, &BT, &key->xs) ||
!ec_jacobian_to_affine(group, &Z_affine, &Z) ||
!cbb_add_point(cbb, group, &Z_affine)) {
goto err;
}
if (!cbb_add_point(&batch_cbb, group, &BT_affine) ||
!cbb_add_point(&batch_cbb, group, &Z_affine)) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE);
goto err;
}
BTs[i] = BT;
Zs[i] = Z;
if (!CBB_flush(cbb)) {
goto err;
}
}
// The DLEQ batching construction is described in appendix B of
// https://eprint.iacr.org/2020/072/20200324:214215. Note the additional
// computations all act on public inputs.
for (size_t i = 0; i < num_to_issue; i++) {
if (!hash_to_scalar_batch(method, &es[i], &batch_cbb, i)) {
goto err;
}
}
EC_RAW_POINT BT_batch, Z_batch;
if (!ec_point_mul_scalar_public_batch(group, &BT_batch,
/*g_scalar=*/NULL, BTs, es,
num_to_issue) ||
!ec_point_mul_scalar_public_batch(group, &Z_batch,
/*g_scalar=*/NULL, Zs, es,
num_to_issue)) {
goto err;
}
CBB proof;
if (!CBB_add_u16_length_prefixed(cbb, &proof) ||
!dleq_generate(method, &proof, key, &BT_batch, &Z_batch) ||
!CBB_flush(cbb)) {
goto err;
}
// Skip over any unused requests.
size_t point_len = 1 + 2 * BN_num_bytes(&group->field);
if (!CBS_skip(cbs, point_len * (num_requested - num_to_issue))) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_DECODE_FAILURE);
goto err;
}
ret = 1;
err:
OPENSSL_free(BTs);
OPENSSL_free(Zs);
OPENSSL_free(es);
CBB_cleanup(&batch_cbb);
return ret;
}
static STACK_OF(TRUST_TOKEN) *
voprf_unblind(const VOPRF_METHOD *method, const TRUST_TOKEN_CLIENT_KEY *key,
const STACK_OF(TRUST_TOKEN_PRETOKEN) * pretokens, CBS *cbs,
size_t count, uint32_t key_id) {
const EC_GROUP *group = method->group;
if (count > sk_TRUST_TOKEN_PRETOKEN_num(pretokens)) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_DECODE_FAILURE);
return NULL;
}
int ok = 0;
STACK_OF(TRUST_TOKEN) *ret = sk_TRUST_TOKEN_new_null();
if (ret == NULL) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE);
return NULL;
}
if (count > ((size_t)-1) / sizeof(EC_RAW_POINT) ||
count > ((size_t)-1) / sizeof(EC_SCALAR)) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_OVERFLOW);
return 0;
}
EC_RAW_POINT *BTs = OPENSSL_malloc(count * sizeof(EC_RAW_POINT));
EC_RAW_POINT *Zs = OPENSSL_malloc(count * sizeof(EC_RAW_POINT));
EC_SCALAR *es = OPENSSL_malloc(count * sizeof(EC_SCALAR));
CBB batch_cbb;
CBB_zero(&batch_cbb);
if (!BTs ||
!Zs ||
!es ||
!CBB_init(&batch_cbb, 0) ||
!cbb_add_point(&batch_cbb, method->group, &key->pubs)) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE);
goto err;
}
for (size_t i = 0; i < count; i++) {
const TRUST_TOKEN_PRETOKEN *pretoken =
sk_TRUST_TOKEN_PRETOKEN_value(pretokens, i);
EC_AFFINE Z_affine;
if (!cbs_get_point(cbs, group, &Z_affine)) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_DECODE_FAILURE);
goto err;
}
ec_affine_to_jacobian(group, &BTs[i], &pretoken->Tp);
ec_affine_to_jacobian(group, &Zs[i], &Z_affine);
if (!cbb_add_point(&batch_cbb, group, &pretoken->Tp) ||
!cbb_add_point(&batch_cbb, group, &Z_affine)) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE);
goto err;
}
// Unblind the token.
// pretoken->r is rinv.
EC_RAW_POINT N;
EC_AFFINE N_affine;
if (!ec_point_mul_scalar(group, &N, &Zs[i], &pretoken->r) ||
!ec_jacobian_to_affine(group, &N_affine, &N)) {
goto err;
}
// Serialize the token. Include |key_id| to avoid an extra copy in the layer
// above.
CBB token_cbb;
size_t point_len = 1 + 2 * BN_num_bytes(&group->field);
if (!CBB_init(&token_cbb, 4 + TRUST_TOKEN_NONCE_SIZE + (2 + point_len)) ||
!CBB_add_u32(&token_cbb, key_id) ||
!CBB_add_bytes(&token_cbb, pretoken->t, TRUST_TOKEN_NONCE_SIZE) ||
!cbb_add_point(&token_cbb, group, &N_affine) ||
!CBB_flush(&token_cbb)) {
CBB_cleanup(&token_cbb);
goto err;
}
TRUST_TOKEN *token =
TRUST_TOKEN_new(CBB_data(&token_cbb), CBB_len(&token_cbb));
CBB_cleanup(&token_cbb);
if (token == NULL ||
!sk_TRUST_TOKEN_push(ret, token)) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_MALLOC_FAILURE);
TRUST_TOKEN_free(token);
goto err;
}
}
// The DLEQ batching construction is described in appendix B of
// https://eprint.iacr.org/2020/072/20200324:214215. Note the additional
// computations all act on public inputs.
for (size_t i = 0; i < count; i++) {
if (!hash_to_scalar_batch(method, &es[i], &batch_cbb, i)) {
goto err;
}
}
EC_RAW_POINT BT_batch, Z_batch;
if (!ec_point_mul_scalar_public_batch(group, &BT_batch,
/*g_scalar=*/NULL, BTs, es, count) ||
!ec_point_mul_scalar_public_batch(group, &Z_batch,
/*g_scalar=*/NULL, Zs, es, count)) {
goto err;
}
CBS proof;
if (!CBS_get_u16_length_prefixed(cbs, &proof) ||
!dleq_verify(method, &proof, key, &BT_batch, &Z_batch) ||
CBS_len(&proof) != 0) {
goto err;
}
ok = 1;
err:
OPENSSL_free(BTs);
OPENSSL_free(Zs);
OPENSSL_free(es);
CBB_cleanup(&batch_cbb);
if (!ok) {
sk_TRUST_TOKEN_pop_free(ret, TRUST_TOKEN_free);
ret = NULL;
}
return ret;
}
static int voprf_read(const VOPRF_METHOD *method,
const TRUST_TOKEN_ISSUER_KEY *key,
uint8_t out_nonce[TRUST_TOKEN_NONCE_SIZE],
const uint8_t *token, size_t token_len) {
const EC_GROUP *group = method->group;
CBS cbs;
CBS_init(&cbs, token, token_len);
EC_AFFINE Ws;
if (!CBS_copy_bytes(&cbs, out_nonce, TRUST_TOKEN_NONCE_SIZE) ||
!cbs_get_point(&cbs, group, &Ws) ||
CBS_len(&cbs) != 0) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_INVALID_TOKEN);
return 0;
}
EC_RAW_POINT T;
if (!method->hash_to_group(group, &T, out_nonce)) {
return 0;
}
EC_RAW_POINT Ws_calculated;
if (!ec_point_mul_scalar(group, &Ws_calculated, &T, &key->xs) ||
!ec_affine_jacobian_equal(group, &Ws, &Ws_calculated)) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, TRUST_TOKEN_R_BAD_VALIDITY_CHECK);
return 0;
}
return 1;
}
// VOPRF experiment v2.
static int voprf_exp2_hash_to_group(const EC_GROUP *group, EC_RAW_POINT *out,
const uint8_t t[TRUST_TOKEN_NONCE_SIZE]) {
const uint8_t kHashTLabel[] = "TrustToken VOPRF Experiment V2 HashToGroup";
return ec_hash_to_curve_p384_xmd_sha512_sswu_draft07(
group, out, kHashTLabel, sizeof(kHashTLabel), t, TRUST_TOKEN_NONCE_SIZE);
}
static int voprf_exp2_hash_to_scalar(const EC_GROUP *group, EC_SCALAR *out,
uint8_t *buf, size_t len) {
const uint8_t kHashCLabel[] = "TrustToken VOPRF Experiment V2 HashToScalar";
return ec_hash_to_scalar_p384_xmd_sha512_draft07(
group, out, kHashCLabel, sizeof(kHashCLabel), buf, len);
}
static int voprf_exp2_ok = 0;
static VOPRF_METHOD voprf_exp2_method;
static CRYPTO_once_t voprf_exp2_method_once = CRYPTO_ONCE_INIT;
static void voprf_exp2_init_method_impl(void) {
voprf_exp2_ok =
voprf_init_method(&voprf_exp2_method, NID_secp384r1,
voprf_exp2_hash_to_group, voprf_exp2_hash_to_scalar);
}
static int voprf_exp2_init_method(void) {
CRYPTO_once(&voprf_exp2_method_once, voprf_exp2_init_method_impl);
if (!voprf_exp2_ok) {
OPENSSL_PUT_ERROR(TRUST_TOKEN, ERR_R_INTERNAL_ERROR);
return 0;
}
return 1;
}
int voprf_exp2_generate_key(CBB *out_private, CBB *out_public) {
if (!voprf_exp2_init_method()) {
return 0;
}
return voprf_generate_key(&voprf_exp2_method, out_private, out_public);
}
int voprf_exp2_client_key_from_bytes(TRUST_TOKEN_CLIENT_KEY *key,
const uint8_t *in, size_t len) {
if (!voprf_exp2_init_method()) {
return 0;
}
return voprf_client_key_from_bytes(&voprf_exp2_method, key, in, len);
}
int voprf_exp2_issuer_key_from_bytes(TRUST_TOKEN_ISSUER_KEY *key,
const uint8_t *in, size_t len) {
if (!voprf_exp2_init_method()) {
return 0;
}
return voprf_issuer_key_from_bytes(&voprf_exp2_method, key, in, len);
}
STACK_OF(TRUST_TOKEN_PRETOKEN) * voprf_exp2_blind(CBB *cbb, size_t count) {
if (!voprf_exp2_init_method()) {
return NULL;
}
return voprf_blind(&voprf_exp2_method, cbb, count);
}
int voprf_exp2_sign(const TRUST_TOKEN_ISSUER_KEY *key, CBB *cbb, CBS *cbs,
size_t num_requested, size_t num_to_issue,
uint8_t private_metadata) {
if (!voprf_exp2_init_method() || private_metadata != 0) {
return 0;
}
return voprf_sign(&voprf_exp2_method, key, cbb, cbs, num_requested,
num_to_issue);
}
STACK_OF(TRUST_TOKEN) *
voprf_exp2_unblind(const TRUST_TOKEN_CLIENT_KEY *key,
const STACK_OF(TRUST_TOKEN_PRETOKEN) * pretokens,
CBS *cbs, size_t count, uint32_t key_id) {
if (!voprf_exp2_init_method()) {
return NULL;
}
return voprf_unblind(&voprf_exp2_method, key, pretokens, cbs, count,
key_id);
}
int voprf_exp2_read(const TRUST_TOKEN_ISSUER_KEY *key,
uint8_t out_nonce[TRUST_TOKEN_NONCE_SIZE],
uint8_t *out_private_metadata, const uint8_t *token,
size_t token_len) {
if (!voprf_exp2_init_method()) {
return 0;
}
return voprf_read(&voprf_exp2_method, key, out_nonce, token, token_len);
}