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4b1df4e50f
monero/src/crypto/crypto.cpp
Sarang Noether 4b1df4e50f Fix for biased signature nonce
2019-08-12 15:58:15 -04:00

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// Copyright (c) 2014-2019, The Monero Project
//
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without modification, are
// permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this list of
// conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice, this list
// of conditions and the following disclaimer in the documentation and/or other
// materials provided with the distribution.
//
// 3. Neither the name of the copyright holder nor the names of its contributors may be
// used to endorse or promote products derived from this software without specific
// prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// Parts of this file are originally copyright (c) 2012-2013 The Cryptonote developers
#include <unistd.h>
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <cstdlib>
#include <cstring>
#include <boost/thread/mutex.hpp>
#include <boost/thread/lock_guard.hpp>
#include <boost/shared_ptr.hpp>
#include "common/varint.h"
#include "warnings.h"
#include "crypto.h"
#include "hash.h"
namespace {
static void local_abort(const char *msg)
{
fprintf(stderr, "%s\n", msg);
#ifdef NDEBUG
_exit(1);
#else
abort();
#endif
}
}
namespace crypto {
using std::abort;
using std::int32_t;
using std::int64_t;
using std::size_t;
using std::uint32_t;
using std::uint64_t;
extern "C" {
#include "crypto-ops.h"
#include "random.h"
}
const crypto::public_key null_pkey = crypto::public_key{};
const crypto::secret_key null_skey = crypto::secret_key{};
static inline unsigned char *operator &(ec_point &point) {
return &reinterpret_cast<unsigned char &>(point);
}
static inline const unsigned char *operator &(const ec_point &point) {
return &reinterpret_cast<const unsigned char &>(point);
}
static inline unsigned char *operator &(ec_scalar &scalar) {
return &reinterpret_cast<unsigned char &>(scalar);
}
static inline const unsigned char *operator &(const ec_scalar &scalar) {
return &reinterpret_cast<const unsigned char &>(scalar);
}
void generate_random_bytes_thread_safe(size_t N, uint8_t *bytes)
{
static boost::mutex random_lock;
boost::lock_guard<boost::mutex> lock(random_lock);
generate_random_bytes_not_thread_safe(N, bytes);
}
static inline bool less32(const unsigned char *k0, const unsigned char *k1)
{
for (int n = 31; n >= 0; --n)
{
if (k0[n] < k1[n])
return true;
if (k0[n] > k1[n])
return false;
}
return false;
}
void random32_unbiased(unsigned char *bytes)
{
// l = 2^252 + 27742317777372353535851937790883648493.
// it fits 15 in 32 bytes
static const unsigned char limit[32] = { 0xe3, 0x6a, 0x67, 0x72, 0x8b, 0xce, 0x13, 0x29, 0x8f, 0x30, 0x82, 0x8c, 0x0b, 0xa4, 0x10, 0x39, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xf0 };
do
{
generate_random_bytes_thread_safe(32, bytes);
} while (!sc_isnonzero(bytes) && !less32(bytes, limit)); // should be good about 15/16 of the time
sc_reduce32(bytes);
}
/* generate a random 32-byte (256-bit) integer and copy it to res */
static inline void random_scalar(ec_scalar &res) {
random32_unbiased((unsigned char*)res.data);
}
void hash_to_scalar(const void *data, size_t length, ec_scalar &res) {
cn_fast_hash(data, length, reinterpret_cast<hash &>(res));
sc_reduce32(&res);
}
/*
* generate public and secret keys from a random 256-bit integer
* TODO: allow specifying random value (for wallet recovery)
*
*/
secret_key crypto_ops::generate_keys(public_key &pub, secret_key &sec, const secret_key& recovery_key, bool recover) {
ge_p3 point;
secret_key rng;
if (recover)
{
rng = recovery_key;
}
else
{
random_scalar(rng);
}
sec = rng;
sc_reduce32(&unwrap(sec)); // reduce in case second round of keys (sendkeys)
ge_scalarmult_base(&point, &unwrap(sec));
ge_p3_tobytes(&pub, &point);
return rng;
}
bool crypto_ops::check_key(const public_key &key) {
ge_p3 point;
return ge_frombytes_vartime(&point, &key) == 0;
}
bool crypto_ops::secret_key_to_public_key(const secret_key &sec, public_key &pub) {
ge_p3 point;
if (sc_check(&unwrap(sec)) != 0) {
return false;
}
ge_scalarmult_base(&point, &unwrap(sec));
ge_p3_tobytes(&pub, &point);
return true;
}
bool crypto_ops::generate_key_derivation(const public_key &key1, const secret_key &key2, key_derivation &derivation) {
ge_p3 point;
ge_p2 point2;
ge_p1p1 point3;
assert(sc_check(&key2) == 0);
if (ge_frombytes_vartime(&point, &key1) != 0) {
return false;
}
ge_scalarmult(&point2, &unwrap(key2), &point);
ge_mul8(&point3, &point2);
ge_p1p1_to_p2(&point2, &point3);
ge_tobytes(&derivation, &point2);
return true;
}
void crypto_ops::derivation_to_scalar(const key_derivation &derivation, size_t output_index, ec_scalar &res) {
struct {
key_derivation derivation;
char output_index[(sizeof(size_t) * 8 + 6) / 7];
} buf;
char *end = buf.output_index;
buf.derivation = derivation;
tools::write_varint(end, output_index);
assert(end <= buf.output_index + sizeof buf.output_index);
hash_to_scalar(&buf, end - reinterpret_cast<char *>(&buf), res);
}
bool crypto_ops::derive_public_key(const key_derivation &derivation, size_t output_index,
const public_key &base, public_key &derived_key) {
ec_scalar scalar;
ge_p3 point1;
ge_p3 point2;
ge_cached point3;
ge_p1p1 point4;
ge_p2 point5;
if (ge_frombytes_vartime(&point1, &base) != 0) {
return false;
}
derivation_to_scalar(derivation, output_index, scalar);
ge_scalarmult_base(&point2, &scalar);
ge_p3_to_cached(&point3, &point2);
ge_add(&point4, &point1, &point3);
ge_p1p1_to_p2(&point5, &point4);
ge_tobytes(&derived_key, &point5);
return true;
}
void crypto_ops::derive_secret_key(const key_derivation &derivation, size_t output_index,
const secret_key &base, secret_key &derived_key) {
ec_scalar scalar;
assert(sc_check(&base) == 0);
derivation_to_scalar(derivation, output_index, scalar);
sc_add(&unwrap(derived_key), &unwrap(base), &scalar);
}
bool crypto_ops::derive_subaddress_public_key(const public_key &out_key, const key_derivation &derivation, std::size_t output_index, public_key &derived_key) {
ec_scalar scalar;
ge_p3 point1;
ge_p3 point2;
ge_cached point3;
ge_p1p1 point4;
ge_p2 point5;
if (ge_frombytes_vartime(&point1, &out_key) != 0) {
return false;
}
derivation_to_scalar(derivation, output_index, scalar);
ge_scalarmult_base(&point2, &scalar);
ge_p3_to_cached(&point3, &point2);
ge_sub(&point4, &point1, &point3);
ge_p1p1_to_p2(&point5, &point4);
ge_tobytes(&derived_key, &point5);
return true;
}
struct s_comm {
hash h;
ec_point key;
ec_point comm;
};
struct s_comm_2 {
hash msg;
ec_point D;
ec_point X;
ec_point Y;
};
void crypto_ops::generate_signature(const hash &prefix_hash, const public_key &pub, const secret_key &sec, signature &sig) {
ge_p3 tmp3;
ec_scalar k;
s_comm buf;
#if !defined(NDEBUG)
{
ge_p3 t;
public_key t2;
assert(sc_check(&sec) == 0);
ge_scalarmult_base(&t, &sec);
ge_p3_tobytes(&t2, &t);
assert(pub == t2);
}
#endif
buf.h = prefix_hash;
buf.key = pub;
try_again:
random_scalar(k);
ge_scalarmult_base(&tmp3, &k);
ge_p3_tobytes(&buf.comm, &tmp3);
hash_to_scalar(&buf, sizeof(s_comm), sig.c);
if (!sc_isnonzero((const unsigned char*)sig.c.data))
goto try_again;
sc_mulsub(&sig.r, &sig.c, &unwrap(sec), &k);
if (!sc_isnonzero((const unsigned char*)sig.r.data))
goto try_again;
}
bool crypto_ops::check_signature(const hash &prefix_hash, const public_key &pub, const signature &sig) {
ge_p2 tmp2;
ge_p3 tmp3;
ec_scalar c;
s_comm buf;
assert(check_key(pub));
buf.h = prefix_hash;
buf.key = pub;
if (ge_frombytes_vartime(&tmp3, &pub) != 0) {
return false;
}
if (sc_check(&sig.c) != 0 || sc_check(&sig.r) != 0 || !sc_isnonzero(&sig.c)) {
return false;
}
ge_double_scalarmult_base_vartime(&tmp2, &sig.c, &tmp3, &sig.r);
ge_tobytes(&buf.comm, &tmp2);
static const ec_point infinity = {{ 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}};
if (memcmp(&buf.comm, &infinity, 32) == 0)
return false;
hash_to_scalar(&buf, sizeof(s_comm), c);
sc_sub(&c, &c, &sig.c);
return sc_isnonzero(&c) == 0;
}
void crypto_ops::generate_tx_proof(const hash &prefix_hash, const public_key &R, const public_key &A, const boost::optional<public_key> &B, const public_key &D, const secret_key &r, signature &sig) {
// sanity check
ge_p3 R_p3;
ge_p3 A_p3;
ge_p3 B_p3;
ge_p3 D_p3;
if (ge_frombytes_vartime(&R_p3, &R) != 0) throw std::runtime_error("tx pubkey is invalid");
if (ge_frombytes_vartime(&A_p3, &A) != 0) throw std::runtime_error("recipient view pubkey is invalid");
if (B && ge_frombytes_vartime(&B_p3, &*B) != 0) throw std::runtime_error("recipient spend pubkey is invalid");
if (ge_frombytes_vartime(&D_p3, &D) != 0) throw std::runtime_error("key derivation is invalid");
#if !defined(NDEBUG)
{
assert(sc_check(&r) == 0);
// check R == r*G or R == r*B
public_key dbg_R;
if (B)
{
ge_p2 dbg_R_p2;
ge_scalarmult(&dbg_R_p2, &r, &B_p3);
ge_tobytes(&dbg_R, &dbg_R_p2);
}
else
{
ge_p3 dbg_R_p3;
ge_scalarmult_base(&dbg_R_p3, &r);
ge_p3_tobytes(&dbg_R, &dbg_R_p3);
}
assert(R == dbg_R);
// check D == r*A
ge_p2 dbg_D_p2;
ge_scalarmult(&dbg_D_p2, &r, &A_p3);
public_key dbg_D;
ge_tobytes(&dbg_D, &dbg_D_p2);
assert(D == dbg_D);
}
#endif
// pick random k
ec_scalar k;
random_scalar(k);
s_comm_2 buf;
buf.msg = prefix_hash;
buf.D = D;
if (B)
{
// compute X = k*B
ge_p2 X_p2;
ge_scalarmult(&X_p2, &k, &B_p3);
ge_tobytes(&buf.X, &X_p2);
}
else
{
// compute X = k*G
ge_p3 X_p3;
ge_scalarmult_base(&X_p3, &k);
ge_p3_tobytes(&buf.X, &X_p3);
}
// compute Y = k*A
ge_p2 Y_p2;
ge_scalarmult(&Y_p2, &k, &A_p3);
ge_tobytes(&buf.Y, &Y_p2);
// sig.c = Hs(Msg || D || X || Y)
hash_to_scalar(&buf, sizeof(buf), sig.c);
// sig.r = k - sig.c*r
sc_mulsub(&sig.r, &sig.c, &unwrap(r), &k);
}
bool crypto_ops::check_tx_proof(const hash &prefix_hash, const public_key &R, const public_key &A, const boost::optional<public_key> &B, const public_key &D, const signature &sig) {
// sanity check
ge_p3 R_p3;
ge_p3 A_p3;
ge_p3 B_p3;
ge_p3 D_p3;
if (ge_frombytes_vartime(&R_p3, &R) != 0) return false;
if (ge_frombytes_vartime(&A_p3, &A) != 0) return false;
if (B && ge_frombytes_vartime(&B_p3, &*B) != 0) return false;
if (ge_frombytes_vartime(&D_p3, &D) != 0) return false;
if (sc_check(&sig.c) != 0 || sc_check(&sig.r) != 0) return false;
// compute sig.c*R
ge_p3 cR_p3;
{
ge_p2 cR_p2;
ge_scalarmult(&cR_p2, &sig.c, &R_p3);
public_key cR;
ge_tobytes(&cR, &cR_p2);
if (ge_frombytes_vartime(&cR_p3, &cR) != 0) return false;
}
ge_p1p1 X_p1p1;
if (B)
{
// compute X = sig.c*R + sig.r*B
ge_p2 rB_p2;
ge_scalarmult(&rB_p2, &sig.r, &B_p3);
public_key rB;
ge_tobytes(&rB, &rB_p2);
ge_p3 rB_p3;
if (ge_frombytes_vartime(&rB_p3, &rB) != 0) return false;
ge_cached rB_cached;
ge_p3_to_cached(&rB_cached, &rB_p3);
ge_add(&X_p1p1, &cR_p3, &rB_cached);
}
else
{
// compute X = sig.c*R + sig.r*G
ge_p3 rG_p3;
ge_scalarmult_base(&rG_p3, &sig.r);
ge_cached rG_cached;
ge_p3_to_cached(&rG_cached, &rG_p3);
ge_add(&X_p1p1, &cR_p3, &rG_cached);
}
ge_p2 X_p2;
ge_p1p1_to_p2(&X_p2, &X_p1p1);
// compute sig.c*D
ge_p2 cD_p2;
ge_scalarmult(&cD_p2, &sig.c, &D_p3);
// compute sig.r*A
ge_p2 rA_p2;
ge_scalarmult(&rA_p2, &sig.r, &A_p3);
// compute Y = sig.c*D + sig.r*A
public_key cD;
public_key rA;
ge_tobytes(&cD, &cD_p2);
ge_tobytes(&rA, &rA_p2);
ge_p3 cD_p3;
ge_p3 rA_p3;
if (ge_frombytes_vartime(&cD_p3, &cD) != 0) return false;
if (ge_frombytes_vartime(&rA_p3, &rA) != 0) return false;
ge_cached rA_cached;
ge_p3_to_cached(&rA_cached, &rA_p3);
ge_p1p1 Y_p1p1;
ge_add(&Y_p1p1, &cD_p3, &rA_cached);
ge_p2 Y_p2;
ge_p1p1_to_p2(&Y_p2, &Y_p1p1);
// compute c2 = Hs(Msg || D || X || Y)
s_comm_2 buf;
buf.msg = prefix_hash;
buf.D = D;
ge_tobytes(&buf.X, &X_p2);
ge_tobytes(&buf.Y, &Y_p2);
ec_scalar c2;
hash_to_scalar(&buf, sizeof(s_comm_2), c2);
// test if c2 == sig.c
sc_sub(&c2, &c2, &sig.c);
return sc_isnonzero(&c2) == 0;
}
static void hash_to_ec(const public_key &key, ge_p3 &res) {
hash h;
ge_p2 point;
ge_p1p1 point2;
cn_fast_hash(std::addressof(key), sizeof(public_key), h);
ge_fromfe_frombytes_vartime(&point, reinterpret_cast<const unsigned char *>(&h));
ge_mul8(&point2, &point);
ge_p1p1_to_p3(&res, &point2);
}
void crypto_ops::generate_key_image(const public_key &pub, const secret_key &sec, key_image &image) {
ge_p3 point;
ge_p2 point2;
assert(sc_check(&sec) == 0);
hash_to_ec(pub, point);
ge_scalarmult(&point2, &unwrap(sec), &point);
ge_tobytes(&image, &point2);
}
PUSH_WARNINGS
DISABLE_VS_WARNINGS(4200)
struct ec_point_pair {
ec_point a, b;
};
struct rs_comm {
hash h;
struct ec_point_pair ab[];
};
POP_WARNINGS
static inline size_t rs_comm_size(size_t pubs_count) {
return sizeof(rs_comm) + pubs_count * sizeof(ec_point_pair);
}
void crypto_ops::generate_ring_signature(const hash &prefix_hash, const key_image &image,
const public_key *const *pubs, size_t pubs_count,
const secret_key &sec, size_t sec_index,
signature *sig) {
size_t i;
ge_p3 image_unp;
ge_dsmp image_pre;
ec_scalar sum, k, h;
boost::shared_ptr<rs_comm> buf(reinterpret_cast<rs_comm *>(malloc(rs_comm_size(pubs_count))), free);
if (!buf)
local_abort("malloc failure");
assert(sec_index < pubs_count);
#if !defined(NDEBUG)
{
ge_p3 t;
public_key t2;
key_image t3;
assert(sc_check(&sec) == 0);
ge_scalarmult_base(&t, &sec);
ge_p3_tobytes(&t2, &t);
assert(*pubs[sec_index] == t2);
generate_key_image(*pubs[sec_index], sec, t3);
assert(image == t3);
for (i = 0; i < pubs_count; i++) {
assert(check_key(*pubs[i]));
}
}
#endif
if (ge_frombytes_vartime(&image_unp, &image) != 0) {
local_abort("invalid key image");
}
ge_dsm_precomp(image_pre, &image_unp);
sc_0(&sum);
buf->h = prefix_hash;
for (i = 0; i < pubs_count; i++) {
ge_p2 tmp2;
ge_p3 tmp3;
if (i == sec_index) {
random_scalar(k);
ge_scalarmult_base(&tmp3, &k);
ge_p3_tobytes(&buf->ab[i].a, &tmp3);
hash_to_ec(*pubs[i], tmp3);
ge_scalarmult(&tmp2, &k, &tmp3);
ge_tobytes(&buf->ab[i].b, &tmp2);
} else {
random_scalar(sig[i].c);
random_scalar(sig[i].r);
if (ge_frombytes_vartime(&tmp3, &*pubs[i]) != 0) {
local_abort("invalid pubkey");
}
ge_double_scalarmult_base_vartime(&tmp2, &sig[i].c, &tmp3, &sig[i].r);
ge_tobytes(&buf->ab[i].a, &tmp2);
hash_to_ec(*pubs[i], tmp3);
ge_double_scalarmult_precomp_vartime(&tmp2, &sig[i].r, &tmp3, &sig[i].c, image_pre);
ge_tobytes(&buf->ab[i].b, &tmp2);
sc_add(&sum, &sum, &sig[i].c);
}
}
hash_to_scalar(buf.get(), rs_comm_size(pubs_count), h);
sc_sub(&sig[sec_index].c, &h, &sum);
sc_mulsub(&sig[sec_index].r, &sig[sec_index].c, &unwrap(sec), &k);
}
bool crypto_ops::check_ring_signature(const hash &prefix_hash, const key_image &image,
const public_key *const *pubs, size_t pubs_count,
const signature *sig) {
size_t i;
ge_p3 image_unp;
ge_dsmp image_pre;
ec_scalar sum, h;
boost::shared_ptr<rs_comm> buf(reinterpret_cast<rs_comm *>(malloc(rs_comm_size(pubs_count))), free);
if (!buf)
return false;
#if !defined(NDEBUG)
for (i = 0; i < pubs_count; i++) {
assert(check_key(*pubs[i]));
}
#endif
if (ge_frombytes_vartime(&image_unp, &image) != 0) {
return false;
}
ge_dsm_precomp(image_pre, &image_unp);
sc_0(&sum);
buf->h = prefix_hash;
for (i = 0; i < pubs_count; i++) {
ge_p2 tmp2;
ge_p3 tmp3;
if (sc_check(&sig[i].c) != 0 || sc_check(&sig[i].r) != 0) {
return false;
}
if (ge_frombytes_vartime(&tmp3, &*pubs[i]) != 0) {
return false;
}
ge_double_scalarmult_base_vartime(&tmp2, &sig[i].c, &tmp3, &sig[i].r);
ge_tobytes(&buf->ab[i].a, &tmp2);
hash_to_ec(*pubs[i], tmp3);
ge_double_scalarmult_precomp_vartime(&tmp2, &sig[i].r, &tmp3, &sig[i].c, image_pre);
ge_tobytes(&buf->ab[i].b, &tmp2);
sc_add(&sum, &sum, &sig[i].c);
}
hash_to_scalar(buf.get(), rs_comm_size(pubs_count), h);
sc_sub(&h, &h, &sum);
return sc_isnonzero(&h) == 0;
}
}
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