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schnorrsig: allow signing and verification of variable length msgs

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Varlen message support for the default sign function comes from recommending
tagged_sha256. sign_custom on the other hand gets the ability to directly sign
message of any length. This also implies signing and verification support for
the empty message (NULL) with msglen 0.

Tests for variable lengths follow in a later commit.
This commit is contained in:
Jonas Nick
2021-01-15 21:19:34 +00:00
parent 5a8e4991ad
commit a0c3fc177f
5 changed files with 111 additions and 81 deletions
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104
src/modules/schnorrsig/tests_impl.h
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@@ -12,11 +12,11 @@
/* Checks that a bit flip in the n_flip-th argument (that has n_bytes many
* bytes) changes the hash function
*/
void nonce_function_bip340_bitflip(unsigned char **args, size_t n_flip, size_t n_bytes, size_t algolen) {
void nonce_function_bip340_bitflip(unsigned char **args, size_t n_flip, size_t n_bytes, size_t msglen, size_t algolen) {
unsigned char nonces[2][32];
CHECK(nonce_function_bip340(nonces[0], args[0], args[1], args[2], args[3], algolen, args[4]) == 1);
CHECK(nonce_function_bip340(nonces[0], args[0], msglen, args[1], args[2], args[3], algolen, args[4]) == 1);
secp256k1_testrand_flip(args[n_flip], n_bytes);
CHECK(nonce_function_bip340(nonces[1], args[0], args[1], args[2], args[3], algolen, args[4]) == 1);
CHECK(nonce_function_bip340(nonces[1], args[0], msglen, args[1], args[2], args[3], algolen, args[4]) == 1);
CHECK(secp256k1_memcmp_var(nonces[0], nonces[1], 32) != 0);
}
@@ -40,6 +40,7 @@ void run_nonce_function_bip340_tests(void) {
secp256k1_sha256 sha_optimized;
unsigned char nonce[32];
unsigned char msg[32];
size_t msglen = sizeof(msg);
unsigned char key[32];
unsigned char pk[32];
unsigned char aux_rand[32];
@@ -72,34 +73,42 @@ void run_nonce_function_bip340_tests(void) {
args[3] = algo;
args[4] = aux_rand;
for (i = 0; i < count; i++) {
nonce_function_bip340_bitflip(args, 0, 32, algolen);
nonce_function_bip340_bitflip(args, 1, 32, algolen);
nonce_function_bip340_bitflip(args, 2, 32, algolen);
nonce_function_bip340_bitflip(args, 0, 32, msglen, algolen);
nonce_function_bip340_bitflip(args, 1, 32, msglen, algolen);
nonce_function_bip340_bitflip(args, 2, 32, msglen, algolen);
/* Flip algo special case "BIP0340/nonce" */
nonce_function_bip340_bitflip(args, 3, algolen, algolen);
nonce_function_bip340_bitflip(args, 3, algolen, msglen, algolen);
/* Flip algo again */
nonce_function_bip340_bitflip(args, 3, algolen, algolen);
nonce_function_bip340_bitflip(args, 4, 32, algolen);
nonce_function_bip340_bitflip(args, 3, algolen, msglen, algolen);
nonce_function_bip340_bitflip(args, 4, 32, msglen, algolen);
}
/* NULL algo is disallowed */
CHECK(nonce_function_bip340(nonce, msg, key, pk, NULL, 0, NULL) == 0);
CHECK(nonce_function_bip340(nonce, msg, key, pk, algo, algolen, NULL) == 1);
CHECK(nonce_function_bip340(nonce, msg, msglen, key, pk, NULL, 0, NULL) == 0);
CHECK(nonce_function_bip340(nonce, msg, msglen, key, pk, algo, algolen, NULL) == 1);
/* Other algo is fine */
secp256k1_rfc6979_hmac_sha256_generate(&secp256k1_test_rng, algo, algolen);
CHECK(nonce_function_bip340(nonce, msg, key, pk, algo, algolen, NULL) == 1);
CHECK(nonce_function_bip340(nonce, msg, msglen, key, pk, algo, algolen, NULL) == 1);
for (i = 0; i < count; i++) {
unsigned char nonce2[32];
uint32_t offset = secp256k1_testrand_int(msglen - 1);
size_t msglen_tmp = (msglen + offset) % msglen;
size_t algolen_tmp;
/* Different msglen gives different nonce */
CHECK(nonce_function_bip340(nonce2, msg, msglen_tmp, key, pk, algo, algolen, NULL) == 1);
CHECK(secp256k1_memcmp_var(nonce, nonce2, 32) != 0);
/* Different algolen gives different nonce */
uint32_t offset = secp256k1_testrand_int(algolen - 1);
size_t algolen_tmp = (algolen + offset) % algolen;
CHECK(nonce_function_bip340(nonce2, msg, key, pk, algo, algolen_tmp, NULL) == 1);
offset = secp256k1_testrand_int(algolen - 1);
algolen_tmp = (algolen + offset) % algolen;
CHECK(nonce_function_bip340(nonce2, msg, msglen, key, pk, algo, algolen_tmp, NULL) == 1);
CHECK(secp256k1_memcmp_var(nonce, nonce2, 32) != 0);
}
/* NULL aux_rand argument is allowed. */
CHECK(nonce_function_bip340(nonce, msg, key, pk, algo, algolen, NULL) == 1);
CHECK(nonce_function_bip340(nonce, msg, msglen, key, pk, algo, algolen, NULL) == 1);
}
void test_schnorrsig_api(void) {
@@ -160,19 +169,19 @@ void test_schnorrsig_api(void) {
ecount = 0;
CHECK(secp256k1_schnorrsig_sign(sign, sig, msg, &keypairs[0], NULL) == 1);
CHECK(secp256k1_schnorrsig_verify(none, sig, msg, &pk[0]) == 0);
CHECK(secp256k1_schnorrsig_verify(none, sig, msg, sizeof(msg), &pk[0]) == 0);
CHECK(ecount == 1);
CHECK(secp256k1_schnorrsig_verify(sign, sig, msg, &pk[0]) == 0);
CHECK(secp256k1_schnorrsig_verify(sign, sig, msg, sizeof(msg), &pk[0]) == 0);
CHECK(ecount == 2);
CHECK(secp256k1_schnorrsig_verify(vrfy, sig, msg, &pk[0]) == 1);
CHECK(secp256k1_schnorrsig_verify(vrfy, sig, msg, sizeof(msg), &pk[0]) == 1);
CHECK(ecount == 2);
CHECK(secp256k1_schnorrsig_verify(vrfy, NULL, msg, &pk[0]) == 0);
CHECK(secp256k1_schnorrsig_verify(vrfy, NULL, msg, sizeof(msg), &pk[0]) == 0);
CHECK(ecount == 3);
CHECK(secp256k1_schnorrsig_verify(vrfy, sig, NULL, &pk[0]) == 0);
CHECK(secp256k1_schnorrsig_verify(vrfy, sig, NULL, sizeof(msg), &pk[0]) == 0);
CHECK(ecount == 4);
CHECK(secp256k1_schnorrsig_verify(vrfy, sig, msg, NULL) == 0);
CHECK(secp256k1_schnorrsig_verify(vrfy, sig, msg, sizeof(msg), NULL) == 0);
CHECK(ecount == 5);
CHECK(secp256k1_schnorrsig_verify(vrfy, sig, msg, &zero_pk) == 0);
CHECK(secp256k1_schnorrsig_verify(vrfy, sig, msg, sizeof(msg), &zero_pk) == 0);
CHECK(ecount == 6);
secp256k1_context_destroy(none);
@@ -195,19 +204,19 @@ void test_schnorrsig_sha256_tagged(void) {
/* Helper function for schnorrsig_bip_vectors
* Signs the message and checks that it's the same as expected_sig. */
void test_schnorrsig_bip_vectors_check_signing(const unsigned char *sk, const unsigned char *pk_serialized, unsigned char *aux_rand, const unsigned char *msg, const unsigned char *expected_sig) {
void test_schnorrsig_bip_vectors_check_signing(const unsigned char *sk, const unsigned char *pk_serialized, unsigned char *aux_rand, const unsigned char *msg32, const unsigned char *expected_sig) {
unsigned char sig[64];
secp256k1_keypair keypair;
secp256k1_xonly_pubkey pk, pk_expected;
CHECK(secp256k1_keypair_create(ctx, &keypair, sk));
CHECK(secp256k1_schnorrsig_sign(ctx, sig, msg, &keypair, aux_rand));
CHECK(secp256k1_schnorrsig_sign(ctx, sig, msg32, &keypair, aux_rand));
CHECK(secp256k1_memcmp_var(sig, expected_sig, 64) == 0);
CHECK(secp256k1_xonly_pubkey_parse(ctx, &pk_expected, pk_serialized));
CHECK(secp256k1_keypair_xonly_pub(ctx, &pk, NULL, &keypair));
CHECK(secp256k1_memcmp_var(&pk, &pk_expected, sizeof(pk)) == 0);
CHECK(secp256k1_schnorrsig_verify(ctx, sig, msg, &pk));
CHECK(secp256k1_schnorrsig_verify(ctx, sig, msg32, 32, &pk));
}
/* Helper function for schnorrsig_bip_vectors
@@ -216,7 +225,7 @@ void test_schnorrsig_bip_vectors_check_verify(const unsigned char *pk_serialized
secp256k1_xonly_pubkey pk;
CHECK(secp256k1_xonly_pubkey_parse(ctx, &pk, pk_serialized));
CHECK(expected == secp256k1_schnorrsig_verify(ctx, sig, msg32, &pk));
CHECK(expected == secp256k1_schnorrsig_verify(ctx, sig, msg32, 32, &pk));
}
/* Test vectors according to BIP-340 ("Schnorr Signatures for secp256k1"). See
@@ -639,8 +648,9 @@ void test_schnorrsig_bip_vectors(void) {
}
/* Nonce function that returns constant 0 */
static int nonce_function_failing(unsigned char *nonce32, const unsigned char *msg32, const unsigned char *key32, const unsigned char *xonly_pk32, const unsigned char *algo, size_t algolen, void *data) {
(void) msg32;
static int nonce_function_failing(unsigned char *nonce32, const unsigned char *msg, size_t msglen, const unsigned char *key32, const unsigned char *xonly_pk32, const unsigned char *algo, size_t algolen, void *data) {
(void) msg;
(void) msglen;
(void) key32;
(void) xonly_pk32;
(void) algo;
@@ -651,8 +661,9 @@ static int nonce_function_failing(unsigned char *nonce32, const unsigned char *m
}
/* Nonce function that sets nonce to 0 */
static int nonce_function_0(unsigned char *nonce32, const unsigned char *msg32, const unsigned char *key32, const unsigned char *xonly_pk32, const unsigned char *algo, size_t algolen, void *data) {
(void) msg32;
static int nonce_function_0(unsigned char *nonce32, const unsigned char *msg, size_t msglen, const unsigned char *key32, const unsigned char *xonly_pk32, const unsigned char *algo, size_t algolen, void *data) {
(void) msg;
(void) msglen;
(void) key32;
(void) xonly_pk32;
(void) algo;
@@ -664,8 +675,9 @@ static int nonce_function_0(unsigned char *nonce32, const unsigned char *msg32,
}
/* Nonce function that sets nonce to 0xFF...0xFF */
static int nonce_function_overflowing(unsigned char *nonce32, const unsigned char *msg32, const unsigned char *key32, const unsigned char *xonly_pk32, const unsigned char *algo, size_t algolen, void *data) {
(void) msg32;
static int nonce_function_overflowing(unsigned char *nonce32, const unsigned char *msg, size_t msglen, const unsigned char *key32, const unsigned char *xonly_pk32, const unsigned char *algo, size_t algolen, void *data) {
(void) msg;
(void) msglen;
(void) key32;
(void) xonly_pk32;
(void) algo;
@@ -689,12 +701,12 @@ void test_schnorrsig_sign(void) {
/* Test different nonce functions */
memset(sig, 1, sizeof(sig));
CHECK(secp256k1_schnorrsig_sign_custom(ctx, sig, msg, &keypair, nonce_function_failing, NULL) == 0);
CHECK(secp256k1_schnorrsig_sign_custom(ctx, sig, msg, sizeof(msg), &keypair, nonce_function_failing, NULL) == 0);
CHECK(secp256k1_memcmp_var(sig, zeros64, sizeof(sig)) == 0);
memset(&sig, 1, sizeof(sig));
CHECK(secp256k1_schnorrsig_sign_custom(ctx, sig, msg, &keypair, nonce_function_0, NULL) == 0);
CHECK(secp256k1_schnorrsig_sign_custom(ctx, sig, msg, sizeof(msg), &keypair, nonce_function_0, NULL) == 0);
CHECK(secp256k1_memcmp_var(sig, zeros64, sizeof(sig)) == 0);
CHECK(secp256k1_schnorrsig_sign_custom(ctx, sig, msg, &keypair, nonce_function_overflowing, NULL) == 1);
CHECK(secp256k1_schnorrsig_sign_custom(ctx, sig, msg, sizeof(msg), &keypair, nonce_function_overflowing, NULL) == 1);
CHECK(secp256k1_memcmp_var(sig, zeros64, sizeof(sig)) != 0);
}
@@ -718,7 +730,7 @@ void test_schnorrsig_sign_verify(void) {
for (i = 0; i < N_SIGS; i++) {
secp256k1_testrand256(msg[i]);
CHECK(secp256k1_schnorrsig_sign(ctx, sig[i], msg[i], &keypair, NULL));
CHECK(secp256k1_schnorrsig_verify(ctx, sig[i], msg[i], &pk));
CHECK(secp256k1_schnorrsig_verify(ctx, sig[i], msg[i], sizeof(msg[i]), &pk));
}
{
@@ -728,36 +740,36 @@ void test_schnorrsig_sign_verify(void) {
size_t byte_idx = secp256k1_testrand_int(32);
unsigned char xorbyte = secp256k1_testrand_int(254)+1;
sig[sig_idx][byte_idx] ^= xorbyte;
CHECK(!secp256k1_schnorrsig_verify(ctx, sig[sig_idx], msg[sig_idx], &pk));
CHECK(!secp256k1_schnorrsig_verify(ctx, sig[sig_idx], msg[sig_idx], sizeof(msg[sig_idx]), &pk));
sig[sig_idx][byte_idx] ^= xorbyte;
byte_idx = secp256k1_testrand_int(32);
sig[sig_idx][32+byte_idx] ^= xorbyte;
CHECK(!secp256k1_schnorrsig_verify(ctx, sig[sig_idx], msg[sig_idx], &pk));
CHECK(!secp256k1_schnorrsig_verify(ctx, sig[sig_idx], msg[sig_idx], sizeof(msg[sig_idx]), &pk));
sig[sig_idx][32+byte_idx] ^= xorbyte;
byte_idx = secp256k1_testrand_int(32);
msg[sig_idx][byte_idx] ^= xorbyte;
CHECK(!secp256k1_schnorrsig_verify(ctx, sig[sig_idx], msg[sig_idx], &pk));
CHECK(!secp256k1_schnorrsig_verify(ctx, sig[sig_idx], msg[sig_idx], sizeof(msg[sig_idx]), &pk));
msg[sig_idx][byte_idx] ^= xorbyte;
/* Check that above bitflips have been reversed correctly */
CHECK(secp256k1_schnorrsig_verify(ctx, sig[sig_idx], msg[sig_idx], &pk));
CHECK(secp256k1_schnorrsig_verify(ctx, sig[sig_idx], msg[sig_idx], sizeof(msg[sig_idx]), &pk));
}
/* Test overflowing s */
CHECK(secp256k1_schnorrsig_sign(ctx, sig[0], msg[0], &keypair, NULL));
CHECK(secp256k1_schnorrsig_verify(ctx, sig[0], msg[0], &pk));
CHECK(secp256k1_schnorrsig_verify(ctx, sig[0], msg[0], sizeof(msg[0]), &pk));
memset(&sig[0][32], 0xFF, 32);
CHECK(!secp256k1_schnorrsig_verify(ctx, sig[0], msg[0], &pk));
CHECK(!secp256k1_schnorrsig_verify(ctx, sig[0], msg[0], sizeof(msg[0]), &pk));
/* Test negative s */
CHECK(secp256k1_schnorrsig_sign(ctx, sig[0], msg[0], &keypair, NULL));
CHECK(secp256k1_schnorrsig_verify(ctx, sig[0], msg[0], &pk));
CHECK(secp256k1_schnorrsig_verify(ctx, sig[0], msg[0], sizeof(msg[0]), &pk));
secp256k1_scalar_set_b32(&s, &sig[0][32], NULL);
secp256k1_scalar_negate(&s, &s);
secp256k1_scalar_get_b32(&sig[0][32], &s);
CHECK(!secp256k1_schnorrsig_verify(ctx, sig[0], msg[0], &pk));
CHECK(!secp256k1_schnorrsig_verify(ctx, sig[0], msg[0], sizeof(msg[0]), &pk));
}
#undef N_SIGS
@@ -788,7 +800,7 @@ void test_schnorrsig_taproot(void) {
CHECK(secp256k1_schnorrsig_sign(ctx, sig, msg, &keypair, NULL) == 1);
/* Verify key spend */
CHECK(secp256k1_xonly_pubkey_parse(ctx, &output_pk, output_pk_bytes) == 1);
CHECK(secp256k1_schnorrsig_verify(ctx, sig, msg, &output_pk) == 1);
CHECK(secp256k1_schnorrsig_verify(ctx, sig, msg, sizeof(msg), &output_pk) == 1);
/* Script spend */
CHECK(secp256k1_xonly_pubkey_serialize(ctx, internal_pk_bytes, &internal_pk) == 1);