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Less strict ecc_verify_hash_ex (as it was before ecc_recover_key) #443

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Merged
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Oct 5, 2018
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Less strict ecc_verify_hash_ex (as it was before ecc_recover_key) #443

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4 changes: 2 additions & 2 deletions src/pk/ecc/ecc_verify_hash.c
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Original file line number Diff line number Diff line change
Expand Up @@ -76,11 +76,11 @@ int ecc_verify_hash_ex(const unsigned char *sig, unsigned long siglen,
}
else if (sigformat == LTC_ECCSIG_RFC7518) {
/* RFC7518 format - raw (r,s) */
i = mp_unsigned_bin_size(key->dp.order);
if (siglen != (2*i)) {
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@sjaeckel sjaeckel Oct 4, 2018

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I also preferred this version of the check TBH

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@rmw42 rmw42 Oct 4, 2018

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Yeah, I'm not convinced that {0x05, 0x01} should be a valid signature blob for ECDSA, let alone that it should be in a security/proofing library.

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@sjaeckel sjaeckel Oct 4, 2018 •
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I also don't like that it could be a valid signature, but it's a valid edge-case... :/

... and history has proven that there are always implementations who do worse than your implementation so this (0x000..05...) is a good another example of Postel's Law IMO :)

if ((siglen % 2) == 1) {
err = CRYPT_INVALID_PACKET;
goto error;
}
i = siglen / 2;
if ((err = mp_read_unsigned_bin(r, (unsigned char *)sig, i)) != CRYPT_OK) { goto error; }
if ((err = mp_read_unsigned_bin(s, (unsigned char *)sig+i, i)) != CRYPT_OK) { goto error; }
}
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53 changes: 53 additions & 0 deletions tests/ecc_test.c
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Original file line number Diff line number Diff line change
Expand Up @@ -117,6 +117,7 @@ static int _ecc_test_shamir(void)
}
#endif

/* https://github.com/libtom/libtomcrypt/issues/108 */
static int _ecc_issue108(void)
{
void *a, *modulus, *order;
Expand Down Expand Up @@ -151,6 +152,57 @@ static int _ecc_issue108(void)
return err;
}

/* https://github.com/libtom/libtomcrypt/issues/443 */
static int _ecc_issue443(void)
{
const ltc_ecc_curve* cu;
ecc_key key;
int stat = 0;
unsigned char hash[64];
unsigned long hashlen;
const unsigned char msg[] = { 0x54,0x65,0x73,0x74 };
/* msg+pub1+sig1 test vector is from wycheproof - ecdsa_webcrypto_test (incorrect size of signature) */
const unsigned char pub1[] = {
0x04,
0x4a,0x03,0xef,0x9f,0x92,0xeb,0x26,0x8c,0xaf,0xa6,0x01,0x07,0x24,0x89,0xa5,0x63,
0x80,0xfa,0x0d,0xc4,0x31,0x71,0xd7,0x71,0x28,0x13,0xb3,0xa1,0x9a,0x1e,0xb5,0xe5,
0x3e,0x21,0x3e,0x28,0xa6,0x08,0xce,0x9a,0x2f,0x4a,0x17,0xfd,0x83,0x0c,0x66,0x54,
0x01,0x8a,0x79,0xb3,0xe0,0x26,0x3d,0x91,0xa8,0xba,0x90,0x62,0x2d,0xf6,0xf2,0xf0
};
const unsigned char sig1[] = { 0x05, 0x01 };
/* msg+pub2+sig2 test vector is from wycheproof - ecdsa_webcrypto_test (incorrect size of signature) */
const unsigned char pub2[] = {
0x04,
0x00,0x5f,0x50,0x59,0x30,0x83,0x49,0xf9,0xeb,0xbb,0x4d,0x1c,0x55,0xc0,0xaf,0xcc,0xf6,0x21,0x62,0xec,0x1d,0xd1,
0x2e,0xf3,0xed,0x90,0x66,0x56,0x92,0x4f,0xfd,0x99,0xca,0xb9,0xf0,0x6b,0x0e,0xb2,0x18,0xcf,0xf0,0x78,0xa4,0x67,
0x7a,0x5c,0xe1,0xcc,0x07,0x65,0x2b,0xc9,0x76,0xae,0xfc,0x73,0x2c,0x28,0xf6,0x7e,0xf0,0x78,0xa4,0x34,0xe9,0x99,
0x00,0xa5,0xd1,0x4d,0xf3,0x10,0x63,0x0d,0x76,0xec,0x03,0xcb,0x6f,0x9b,0x95,0xbf,0x1a,0x22,0x43,0x81,0x05,0xc8,
0x8c,0xd9,0xfd,0x3d,0xac,0x80,0xf8,0x57,0xad,0xd3,0x82,0x71,0xd8,0xba,0x90,0x16,0x84,0xb2,0x6d,0x43,0x6d,0x4a,
0x85,0x9a,0xd4,0xcd,0xa5,0xe9,0x67,0x7b,0x73,0xca,0xb3,0xf3,0xe5,0xe4,0x1a,0x3d,0x79,0x96,0x60,0x72,0x79,0xab
};
const unsigned char sig2[] = { 0x01, 0x01 };

hashlen = sizeof(hash);
DO(hash_memory(find_hash("sha256"), msg, sizeof(msg), hash, &hashlen));
DO(ecc_find_curve("secp256r1", &cu));
DO(ecc_set_curve(cu, &key));
DO(ecc_set_key(pub1, sizeof(pub1), PK_PUBLIC, &key));
DO(ecc_verify_hash_rfc7518(sig1, sizeof(sig1), hash, hashlen, &stat, &key));
ecc_free(&key);
if (stat != 1) return CRYPT_FAIL_TESTVECTOR;

hashlen = sizeof(hash);
DO(hash_memory(find_hash("sha512"), msg, sizeof(msg), hash, &hashlen));
DO(ecc_find_curve("secp521r1", &cu));
DO(ecc_set_curve(cu, &key));
DO(ecc_set_key(pub2, sizeof(pub2), PK_PUBLIC, &key));
DO(ecc_verify_hash_rfc7518(sig2, sizeof(sig2), hash, hashlen, &stat, &key));
ecc_free(&key);
if (stat != 1) return CRYPT_FAIL_TESTVECTOR;

return CRYPT_OK;
}

static int _ecc_test_mp(void)
{
void *a, *modulus, *order;
Expand Down Expand Up @@ -1113,6 +1165,7 @@ int ecc_tests(void)
DO(_ecc_import_export());
DO(_ecc_test_mp());
DO(_ecc_issue108());
DO(_ecc_issue443());
#ifdef LTC_ECC_SHAMIR
DO(_ecc_test_shamir());
DO(_ecc_test_recovery());
Expand Down