I have the following code to verify a signature:
#define CONTRACT_LEAF_CERT \
0x30, 0x82, 0x02, 0x31, 0x30, 0x82, 0x01, 0xd7, 0xa0, 0x03, 0x02, 0x01, \
0x02, 0x02, 0x02, 0x30, 0x44, 0x30, 0x0a, 0x06, 0x08, 0x2a, 0x86, 0x48, \
0xce, 0x3d, 0x04, 0x03, 0x02, 0x30, 0x45, 0x31, 0x11, 0x30, 0x0f, 0x06, \
0x03, 0x55, 0x04, 0x03, 0x0c, 0x08, 0x4d, 0x4f, 0x53, 0x75, 0x62, 0x43, \
0x41, 0x32, 0x31, 0x0f, 0x30, 0x0d, 0x06, 0x03, 0x55, 0x04, 0x0a, 0x0c, \
0x06, 0x53, 0x77, 0x69, 0x74, 0x63, 0x68, 0x31, 0x0b, 0x30, 0x09, 0x06, \
0x03, 0x55, 0x04, 0x06, 0x13, 0x02, 0x55, 0x4b, 0x31, 0x12, 0x30, 0x10, \
0x06, 0x0a, 0x09, 0x92, 0x26, 0x89, 0x93, 0xf2, 0x2c, 0x64, 0x01, 0x19, \
0x16, 0x02, 0x4d, 0x4f, 0x30, 0x1e, 0x17, 0x0d, 0x32, 0x32, 0x30, 0x39, \
0x30, 0x39, 0x30, 0x36, 0x33, 0x35, 0x31, 0x33, 0x5a, 0x17, 0x0d, 0x32, \
0x34, 0x30, 0x39, 0x30, 0x38, 0x30, 0x36, 0x33, 0x35, 0x31, 0x33, 0x5a, \
0x30, 0x4c, 0x31, 0x18, 0x30, 0x16, 0x06, 0x03, 0x55, 0x04, 0x03, 0x0c, \
0x0f, 0x55, 0x4b, 0x53, 0x57, 0x49, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, \
0x37, 0x38, 0x39, 0x41, 0x31, 0x0f, 0x30, 0x0d, 0x06, 0x03, 0x55, 0x04, \
0x0a, 0x0c, 0x06, 0x53, 0x77, 0x69, 0x74, 0x63, 0x68, 0x31, 0x0b, 0x30, \
0x09, 0x06, 0x03, 0x55, 0x04, 0x06, 0x13, 0x02, 0x55, 0x4b, 0x31, 0x12, \
0x30, 0x10, 0x06, 0x0a, 0x09, 0x92, 0x26, 0x89, 0x93, 0xf2, 0x2c, 0x64, \
0x01, 0x19, 0x16, 0x02, 0x4d, 0x4f, 0x30, 0x59, 0x30, 0x13, 0x06, 0x07, \
0x2a, 0x86, 0x48, 0xce, 0x3d, 0x02, 0x01, 0x06, 0x08, 0x2a, 0x86, 0x48, \
0xce, 0x3d, 0x03, 0x01, 0x07, 0x03, 0x42, 0x00, 0x04, 0x1a, 0xaa, 0xa8, \
0x09, 0x93, 0x76, 0x49, 0xb7, 0x4f, 0x36, 0x5d, 0xbb, 0x0f, 0x8c, 0xb6, \
0x4d, 0xa3, 0x96, 0x72, 0x63, 0xf5, 0x82, 0xcb, 0x94, 0x5c, 0x24, 0xdd, \
0xea, 0x7b, 0x4e, 0x84, 0xee, 0xfd, 0x3d, 0xfd, 0x0a, 0x81, 0xce, 0xb5, \
0x5f, 0x2c, 0x34, 0xb0, 0xe8, 0x6a, 0xe6, 0x10, 0x65, 0xec, 0xea, 0x12, \
0x9f, 0xcd, 0xc7, 0x42, 0xca, 0x25, 0x62, 0x4f, 0x1d, 0xbc, 0x9a, 0x13, \
0x7e, 0xa3, 0x81, 0xaf, 0x30, 0x81, 0xac, 0x30, 0x0c, 0x06, 0x03, 0x55, \
0x1d, 0x13, 0x01, 0x01, 0xff, 0x04, 0x02, 0x30, 0x00, 0x30, 0x0e, 0x06, \
0x03, 0x55, 0x1d, 0x0f, 0x01, 0x01, 0xff, 0x04, 0x04, 0x03, 0x02, 0x03, \
0xe8, 0x30, 0x1d, 0x06, 0x03, 0x55, 0x1d, 0x0e, 0x04, 0x16, 0x04, 0x14, \
0xab, 0xd6, 0x69, 0x70, 0x04, 0x53, 0x7d, 0x8d, 0x6a, 0x5d, 0xb2, 0xbd, \
0xfe, 0xe6, 0x9d, 0x2a, 0x57, 0xe6, 0x68, 0xe8, 0x30, 0x6d, 0x06, 0x08, \
0x2b, 0x06, 0x01, 0x05, 0x05, 0x07, 0x01, 0x01, 0x04, 0x61, 0x30, 0x5f, \
0x30, 0x24, 0x06, 0x08, 0x2b, 0x06, 0x01, 0x05, 0x05, 0x07, 0x30, 0x01, \
0x86, 0x18, 0x68, 0x74, 0x74, 0x70, 0x73, 0x3a, 0x2f, 0x2f, 0x77, 0x77, \
0x77, 0x2e, 0x65, 0x78, 0x61, 0x6d, 0x70, 0x6c, 0x65, 0x2e, 0x63, 0x6f, \
0x6d, 0x2f, 0x30, 0x37, 0x06, 0x08, 0x2b, 0x06, 0x01, 0x05, 0x05, 0x07, \
0x30, 0x02, 0x86, 0x2b, 0x68, 0x74, 0x74, 0x70, 0x73, 0x3a, 0x2f, 0x2f, \
0x77, 0x77, 0x77, 0x2e, 0x65, 0x78, 0x61, 0x6d, 0x70, 0x6c, 0x65, 0x2e, \
0x63, 0x6f, 0x6d, 0x2f, 0x49, 0x6e, 0x74, 0x65, 0x72, 0x6d, 0x65, 0x64, \
0x69, 0x61, 0x74, 0x65, 0x2d, 0x43, 0x41, 0x2e, 0x63, 0x65, 0x72, 0x30, \
0x0a, 0x06, 0x08, 0x2a, 0x86, 0x48, 0xce, 0x3d, 0x04, 0x03, 0x02, 0x03, \
0x48, 0x00, 0x30, 0x45, 0x02, 0x21, 0x00, 0xa8, 0x20, 0xe2, 0x52, 0xd8, \
0xd0, 0x9f, 0x37, 0xf2, 0x6c, 0xad, 0x1a, 0x85, 0xa0, 0x30, 0xc7, 0x94, \
0xa4, 0x65, 0xf0, 0x1f, 0xdd, 0x78, 0x52, 0xb7, 0x12, 0x89, 0x2c, 0x2a, \
0x0c, 0x3b, 0x33, 0x02, 0x20, 0x3d, 0xa7, 0x3b, 0x2b, 0x83, 0xd2, 0xab, \
0x43, 0x82, 0xb4, 0x5a, 0x33, 0x55, 0x81, 0x47, 0xae, 0x04, 0x0a, 0x72, \
0xb9, 0x45, 0xf5, 0xc6, 0x20, 0xb4, 0xa0, 0x0a, 0x91, 0x23, 0xdf, 0x77, \
0x50
#define SIGNATURE_3 \
0xa9, 0xa5, 0x51, 0x0c, 0x48, 0xee, 0x57, 0x2f, 0x49, 0x80, 0xfe, 0xe4, 0xb9, 0x5f, 0x2b, 0xf0, 0x51, 0x1c, 0x7b, 0x38, 0xe2, 0xc8, 0xc0, 0xb9, 0xbb, 0xb2, 0x26, 0xd3, 0x81, 0x28, 0x55, 0x77, 0x22, 0x72, 0x4f, 0x6c, 0x3b, 0x10, 0xd5, 0x64, 0x88, 0x43, 0x6f, 0x05, 0x6a, 0xae, 0x8b, 0xa6, 0xbd, 0x7d, 0x55, 0xf7, 0x42, 0x38, 0x54, 0xaa, 0x33, 0x2b, 0xfd, 0x8c, 0x50, 0x4e, 0xfa, 0x25
#define hash_sha256 \
0x2a, 0xd5, 0xbb, 0x7d, 0x37, 0x9f, 0x0b, 0x4f, 0x09, 0x49, 0xd0, 0x9d, 0x5a, 0xb3, 0x4a, 0x1b, 0xb6, 0x0a, 0xe1, 0x15, 0xca, 0x30, 0x76, 0xbd, 0x8e, 0xae, 0xe5, 0xb8, 0x78, 0xc2, 0x8f, 0x6c
void verifySignature() {
int ret = 0;
unsigned char cert[] = {CONTRACT_LEAF_CERT};
unsigned char hash[] = {hash_sha256};
unsigned char sign[] = {SIGNATURE_3};
size_t cert_size = sizeof(cert);
size_t hash_size = sizeof(hash);
size_t sign_size = sizeof(sign);
mbedtls_x509_crt crt;
mbedtls_x509_crt_init(&crt);
ret = mbedtls_x509_crt_parse_der(&crt, cert, cert_size);
ERR("ERR mbedtls_x509_crt_parse_der", ret)
mbedtls_mpi r;
mbedtls_mpi s;
mbedtls_mpi_init(&r);
mbedtls_mpi_init(&s);
ret = mbedtls_mpi_read_binary(&r, (const unsigned char*)sign, sign_size / 2);
ERR("mbedtls_mpi_read_binary", ret)
ret = mbedtls_mpi_read_binary(&s, (const unsigned char*)sign + sign_size / 2, sign_size / 2);
ERR("mbedtls_mpi_read_binary II", ret)
mbedtls_ecp_group *grp = &mbedtls_pk_ec(crt.pk)->MBEDTLS_PRIVATE(grp);
mbedtls_ecp_point *Q = &mbedtls_pk_ec(crt.pk)->MBEDTLS_PRIVATE(Q);
ret = mbedtls_ecdsa_verify(grp, hash, sizeof(hash), Q, &r, &s);
ERR("mbedtls_ecdsa_verify", ret)
printf("Success!");
}
It is failing on the last step, mbedtls_ecdsa_verify(), with a result code 0x4E00 (The signature is not valid)
I suspect that the way of calculating R and S is not correct, I don’t understand very well these two values. I do not discard that the input data (cert, sign and hash) are not correct, but I have some certainty that they are valid.
This function is based on a message from this forum, but when loading R and S I don’t know exactly what those variables (signaturePtr and Security_Signature512_t) are.
I have spent a good number of hours on this and would greatly appreciate any help.