fido-example.c

/* =============
 * FIDO U2F Test
 * =============
 * Specs: http://fidoalliance.org/specs/fido-u2f-v1.0-ps-20141009/fido-u2f-raw-message-formats-ps-20141009.html
 * Compile: gcc -Wall -Werror -g -o fido-example fido-example.c -lssl */

/* PC-Lint options */
/*lint -efile(537, openssl/ecdsa.h, openssl/sha.h) / no include guard present */
/*lint -e793 / ANSI/ISO limit of 31 'significant characters... */
/*lint -e801 / Use of goto is deprecated */

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sysexits.h>
#include <openssl/x509.h>
#include <openssl/ecdsa.h>
#include <openssl/sha.h>
#include <openssl/err.h>

static const unsigned char const registrationData[] = {
	0x05,0x04,0xb1,0x74,0xbc,0x49,0xc7,0xca,0x25,0x4b,0x70,0xd2,0xe5,0xc2,0x07,0xce,
	0xe9,0xcf,0x17,0x48,0x20,0xeb,0xd7,0x7e,0xa3,0xc6,0x55,0x08,0xc2,0x6d,0xa5,0x1b,
	0x65,0x7c,0x1c,0xc6,0xb9,0x52,0xf8,0x62,0x16,0x97,0x93,0x64,0x82,0xda,0x0a,0x6d,
	0x3d,0x38,0x26,0xa5,0x90,0x95,0xda,0xf6,0xcd,0x7c,0x03,0xe2,0xe6,0x03,0x85,0xd2,
	0xf6,0xd9,0x40,0x2a,0x55,0x2d,0xfd,0xb7,0x47,0x7e,0xd6,0x5f,0xd8,0x41,0x33,0xf8,
	0x61,0x96,0x01,0x0b,0x22,0x15,0xb5,0x7d,0xa7,0x5d,0x31,0x5b,0x7b,0x9e,0x8f,0xe2,
	0xe3,0x92,0x5a,0x60,0x19,0x55,0x1b,0xab,0x61,0xd1,0x65,0x91,0x65,0x9c,0xba,0xf0,
	0x0b,0x49,0x50,0xf7,0xab,0xfe,0x66,0x60,0xe2,0xe0,0x06,0xf7,0x68,0x68,0xb7,0x72,
	0xd7,0x0c,0x25,0x30,0x82,0x01,0x3c,0x30,0x81,0xe4,0xa0,0x03,0x02,0x01,0x02,0x02,
	0x0a,0x47,0x90,0x12,0x80,0x00,0x11,0x55,0x95,0x73,0x52,0x30,0x0a,0x06,0x08,0x2a,
	0x86,0x48,0xce,0x3d,0x04,0x03,0x02,0x30,0x17,0x31,0x15,0x30,0x13,0x06,0x03,0x55,
	0x04,0x03,0x13,0x0c,0x47,0x6e,0x75,0x62,0x62,0x79,0x20,0x50,0x69,0x6c,0x6f,0x74,
	0x30,0x1e,0x17,0x0d,0x31,0x32,0x30,0x38,0x31,0x34,0x31,0x38,0x32,0x39,0x33,0x32,
	0x5a,0x17,0x0d,0x31,0x33,0x30,0x38,0x31,0x34,0x31,0x38,0x32,0x39,0x33,0x32,0x5a,
	0x30,0x31,0x31,0x2f,0x30,0x2d,0x06,0x03,0x55,0x04,0x03,0x13,0x26,0x50,0x69,0x6c,
	0x6f,0x74,0x47,0x6e,0x75,0x62,0x62,0x79,0x2d,0x30,0x2e,0x34,0x2e,0x31,0x2d,0x34,
	0x37,0x39,0x30,0x31,0x32,0x38,0x30,0x30,0x30,0x31,0x31,0x35,0x35,0x39,0x35,0x37,
	0x33,0x35,0x32,0x30,0x59,0x30,0x13,0x06,0x07,0x2a,0x86,0x48,0xce,0x3d,0x02,0x01,
	0x06,0x08,0x2a,0x86,0x48,0xce,0x3d,0x03,0x01,0x07,0x03,0x42,0x00,0x04,0x8d,0x61,
	0x7e,0x65,0xc9,0x50,0x8e,0x64,0xbc,0xc5,0x67,0x3a,0xc8,0x2a,0x67,0x99,0xda,0x3c,
	0x14,0x46,0x68,0x2c,0x25,0x8c,0x46,0x3f,0xff,0xdf,0x58,0xdf,0xd2,0xfa,0x3e,0x6c,
	0x37,0x8b,0x53,0xd7,0x95,0xc4,0xa4,0xdf,0xfb,0x41,0x99,0xed,0xd7,0x86,0x2f,0x23,
	0xab,0xaf,0x02,0x03,0xb4,0xb8,0x91,0x1b,0xa0,0x56,0x99,0x94,0xe1,0x01,0x30,0x0a,
	0x06,0x08,0x2a,0x86,0x48,0xce,0x3d,0x04,0x03,0x02,0x03,0x47,0x00,0x30,0x44,0x02,
	0x20,0x60,0xcd,0xb6,0x06,0x1e,0x9c,0x22,0x26,0x2d,0x1a,0xac,0x1d,0x96,0xd8,0xc7,
	0x08,0x29,0xb2,0x36,0x65,0x31,0xdd,0xa2,0x68,0x83,0x2c,0xb8,0x36,0xbc,0xd3,0x0d,
	0xfa,0x02,0x20,0x63,0x1b,0x14,0x59,0xf0,0x9e,0x63,0x30,0x05,0x57,0x22,0xc8,0xd8,
	0x9b,0x7f,0x48,0x88,0x3b,0x90,0x89,0xb8,0x8d,0x60,0xd1,0xd9,0x79,0x59,0x02,0xb3,
	0x04,0x10,0xdf,0x30,0x45,0x02,0x20,0x14,0x71,0x89,0x9b,0xcc,0x39,0x87,0xe6,0x2e,
	0x82,0x02,0xc9,0xb3,0x9c,0x33,0xc1,0x90,0x33,0xf7,0x34,0x03,0x52,0xdb,0xa8,0x0f,
	0xca,0xb0,0x17,0xdb,0x92,0x30,0xe4,0x02,0x21,0x00,0x82,0x67,0x7d,0x67,0x3d,0x89,
	0x19,0x33,0xad,0xe6,0xf6,0x17,0xe5,0xdb,0xde,0x2e,0x24,0x7e,0x70,0x42,0x3f,0xd5,
	0xad,0x78,0x04,0xa6,0xd3,0xd3,0x96,0x1e,0xf8,0x71 };
static const char* const appId = "http://example.com";
static const char* const clientData =
	"{\"typ\":\"navigator.id.finishEnrollment\","
	"\"challenge\":\"vqrS6WXDe1JUs5_c3i4-LkKIHRr-3XVb3azuA5TifHo\","
	"\"cid_pubkey\":{"
		"\"kty\":\"EC\","
		"\"crv\":\"P-256\","
		"\"x\":\"HzQwlfXX7Q4S5MtCCnZUNBw3RMzPO9tOyWjBqRl4tJ8\","
		"\"y\":\"XVguGFLIZx1fXg3wNqfdbn75hi4-_7-BxhMljw42Ht4\""
		"},"
	"\"origin\":\"http://example.com\""
	"}";

int main(int argc, char * const argv[]) {
	int ret = EX_DATAERR;
	ssize_t cd_len, reg_len;
	unsigned char kh_len;
	unsigned const char *kh, *sig;
	size_t siglen;
	EVP_PKEY *pkey = NULL;
	unsigned char cp_hash[SHA256_DIGEST_LENGTH];
	unsigned char ap_hash[SHA256_DIGEST_LENGTH];
	EVP_MD_CTX ctx;
	X509 *crt = NULL;
	unsigned const char *ptr;
	int i;

	cd_len = strlen(clientData);
	reg_len = sizeof(registrationData);

	if (registrationData[0] != 0x05) {
		fprintf(stderr, "invalid header byte\n");
		goto DONE;
	}

	/* key handle */
	kh = registrationData+67;
	kh_len = registrationData[66];

	/* parse attestation certificate (X.509) */
	ptr = registrationData + 67 + kh_len;
	crt = d2i_X509(NULL, (const unsigned char**)&ptr, reg_len - (ptr-registrationData));
	if (crt == NULL) {
		fprintf(stderr, "Error while parsing X509\n");
		goto DONE;
	}

	/* check if this is a valid signature */
	sig = ptr;
	ECDSA_SIG *ecsig = d2i_ECDSA_SIG(NULL, (const unsigned char**)&ptr, reg_len - (ptr-registrationData));
	if (ecsig == NULL) {
		fprintf(stderr, "Error while reading signature\n");
		ECDSA_SIG_free(ecsig);
		ecsig = NULL;
		goto DONE;
	}
	siglen = ptr-sig;
	ECDSA_SIG_free(ecsig);
	ecsig = NULL;

	/* extract public key from X509 attestation certificare */
	pkey = X509_get_pubkey(crt);
	if (pkey == NULL) {
		fprintf(stderr, "Can't get public key!\n");
		goto DONE;
	}

	/* generate SHA256 hash on challenge parameter and application parameter */
	(void)SHA256((const unsigned char*)clientData, cd_len, cp_hash);
	(void)SHA256((const unsigned char*)appId, strlen(appId), ap_hash);

	/* verify signature */
	if (EVP_VerifyInit(&ctx, EVP_sha256()) != 1) {
		fprintf(stderr, "EVP_VerifyInit() failed\n");
		goto DONE;
	}

	(void)EVP_VerifyUpdate(&ctx, "\0", 1UL);
	(void)EVP_VerifyUpdate(&ctx, ap_hash, 32UL);
	(void)EVP_VerifyUpdate(&ctx, cp_hash, 32UL);
	(void)EVP_VerifyUpdate(&ctx, kh, (unsigned long)kh_len);
	(void)EVP_VerifyUpdate(&ctx, registrationData+1, 65UL);

	if ((i = EVP_VerifyFinal(&ctx, sig, siglen, pkey)) != 1) {
		fprintf(stderr, "EVP_VerifyFinal failed: err=%i, %s\n", i, ERR_error_string(ERR_get_error(), NULL));
		(void)EVP_MD_CTX_cleanup(&ctx);
		goto DONE;
	}

	(void)EVP_MD_CTX_cleanup(&ctx);


	printf("Valid response.\n");
	ret = EX_OK;

DONE:

	if (crt != NULL) {
		X509_free(crt);
		crt = NULL;
	}

	if (pkey != NULL) {
		EVP_PKEY_free(pkey);
		pkey = NULL;
	}

	return(ret);
}