Update X.509 Path Validation

To be continue ...

src/tlcp.c

@@ -792,6 +792,7 @@ int tlcp_do_accept(TLS_CONNECT *conn)
 			goto end;
 		}
 		if (x509_certs_verify(conn->client_certs, conn->client_certs_len,
+			0, // client
 			conn->ca_certs, conn->ca_certs_len, verify_depth, &verify_result) != 1) {
 			error_print();
 			tls_send_alert(conn, TLS_alert_bad_certificate);

src/tls12.c

@@ -345,6 +345,7 @@ int tls12_do_connect(TLS_CONNECT *conn)
 
 	// verify ServerCertificate
 	if (x509_certs_verify(conn->server_certs, conn->server_certs_len,
+		1, // server
 		conn->ca_certs, conn->ca_certs_len, depth, &verify_result) != 1) {
 		error_print();
 		tls_send_alert(conn, alert);
@@ -883,6 +884,7 @@ int tls12_do_accept(TLS_CONNECT *conn)
 			goto end;
 		}
 		if (x509_certs_verify(conn->client_certs, conn->client_certs_len,
+			0, // client
 			conn->ca_certs, conn->ca_certs_len, verify_depth, &verify_result) != 1) {
 			error_print();
 			tls_send_alert(conn, TLS_alert_bad_certificate);

src/x509_cer.c

@@ -1519,7 +1519,54 @@ int x509_cert_check(const uint8_t *cert, size_t certlen)
 	return 1;
 }
 
+int x509_cert_validate(const uint8_t *cert, size_t certlen, int cert_type,
+	int *path_len_constraints)
+{
+	time_t now;
+	time_t not_before;
+	time_t not_after;
+	const uint8_t *exts;
+	size_t extslen;
+
+	x509_cert_get_details(cert, certlen,
+		NULL, // version
+		NULL, NULL, // serial
+		NULL, // signature_algor
+		NULL, NULL, // issuer
+		&not_before, &not_after, // validity
+		NULL, NULL, // subject
+		NULL, // subject_public_key
+		NULL, NULL, // issuer_unique_id
+		NULL, NULL, // subject_unique_id
+		&exts, &extslen, // extensions
+		NULL, // signature_algor
+		NULL, NULL); // signature
+
+	// not_before < now < not_after
+	time(&now);
+	if (not_before >= not_after) {
+		error_print();
+		return -1;
+	}
+	if (now < not_before) {
+		error_print();
+		return X509_verify_err_cert_not_yet_valid;
+	}
+	if (not_after < now) {
+		error_print();
+		return  X509_verify_err_cert_has_expired;
+	}
+
+	if (x509_exts_validate(exts, extslen, cert_type, path_len_constraints) != 1) {
+		error_print();
+		return -1; //TODO: return X509_verify_err_xxx
+	}
+
+	return 1;
+}
+
 int x509_certs_verify(const uint8_t *certs, size_t certslen,
+	int server,
 	const uint8_t *rootcerts, size_t rootcertslen, int depth, int *verify_result)
 {
 	const uint8_t *cert;
@@ -1530,16 +1577,24 @@ int x509_certs_verify(const uint8_t *certs, size_t certslen,
 	size_t namelen;
 	*verify_result = -1;
 
+	int cert_type = server ? X509_cert_server_auth : X509_cert_client_auth;
+	int path_len_constraints;
+
 	if (x509_cert_from_der(&cert, &certlen, &certs, &certslen) != 1) {
 		error_print();
 		return -1;
 	}
 	while (certslen) {
 
-		if ((*verify_result = x509_cert_check(cert, certlen)) < 0) {
+		if ((*verify_result = x509_cert_validate(cert, certlen, cert_type, &path_len_constraints)) < 0) {
 			error_print();
 			return -1;
 		}
+
+		cert_type = X509_cert_ca;
+
+		// FIXME: check path_len_constraints
+
 		if (x509_cert_from_der(&cacert, &cacertlen, &certs, &certslen) != 1) {
 			error_print();
 			return -1;

src/x509_ext.c

@@ -733,6 +733,70 @@ int x509_key_usage_from_name(int *flag, const char *name)
 	return -1;
 }
 
+int x509_key_usage_validate(int bits, int cert_type)
+{
+	switch (cert_type) {
+	case X509_cert_server_auth:
+	case X509_cert_client_auth:
+		if (!(bits & X509_KU_DIGITAL_SIGNATURE)
+			//&& !(bits & X509_KU_NON_REPUDIATION) // un-comment for compatibility
+			) {
+			error_print();
+			return -1;
+		}
+		if ((bits & X509_KU_KEY_CERT_SIGN)
+			|| (bits & X509_KU_CRL_SIGN)) {
+			error_print();
+			return -1;
+		}
+		break;
+
+	case X509_cert_server_key_encipher:
+	case X509_cert_client_key_encipher:
+		if (!(bits & X509_KU_KEY_ENCIPHERMENT)
+			//&& !(bits & X509_KU_KEY_AGREEMENT) // un-comment for compatibility
+			) {
+			error_print();
+			return -1;
+		}
+		if ((bits & X509_KU_KEY_CERT_SIGN)
+			|| (bits & X509_KU_CRL_SIGN)) {
+			error_print();
+			return -1;
+		}
+		break;
+
+	case X509_cert_ca:
+		if (!(bits & X509_KU_KEY_CERT_SIGN)) {
+			error_print();
+			return -1;
+		}
+		if ((bits & X509_KU_DIGITAL_SIGNATURE)
+			|| (bits & X509_KU_NON_REPUDIATION)) {
+			error_print();
+			//return -1; // comment to print warning
+		}
+		break;
+	case X509_cert_crl_sign:
+		if (!(bits & X509_KU_CRL_SIGN)) {
+			error_print();
+			return -1;
+		}
+		if ((bits & X509_KU_DIGITAL_SIGNATURE)
+			|| (bits & X509_KU_NON_REPUDIATION)) {
+			error_print();
+			//return -1; // comment to print warning
+		}
+		break;
+
+	default:
+		error_print();
+		return -1;
+	}
+
+	return 1;
+}
+
 int x509_key_usage_print(FILE *fp, int fmt, int ind, const char *label, int bits)
 {
 	return asn1_bits_print(fp, fmt, ind, label, x509_key_usages, x509_key_usages_count, bits);
@@ -1234,6 +1298,26 @@ int x509_basic_constraints_from_der(int *ca, int *path_len_cons, const uint8_t *
 	return 1;
 }
 
+int x509_basic_constraints_validate(int ca, int path_len_cons, int cert_type)
+{
+	if (cert_type == X509_cert_ca) {
+		if (ca != 1) {
+			error_print();
+			return -1;
+		}
+		if (path_len_cons < 0 || path_len_cons > 6) {
+			error_print();
+			return -1;
+		}
+	} else {
+		if (ca == 1 || path_len_cons >= 0) {
+			error_print();
+			return -1; // comment to only warning
+		}
+	}
+	return 1;
+}
+
 int x509_basic_constraints_print(FILE *fp, int fmt, int ind, const char *label, const uint8_t *d, size_t dlen)
 {
 	int ret, val;
@@ -1522,6 +1606,40 @@ int x509_ext_key_usage_from_der(int *oids, size_t *oids_cnt, size_t max_cnt, con
 	return 1;
 }
 
+int x509_ext_key_usage_validate(const int *oids, size_t oids_cnt, int cert_type)
+{
+	int ret = -1;
+	size_t i;
+
+	for (i = 0; i < oids_cnt; i++) {
+		// anyExtendedKeyUsage might not acceptable for strict validation
+		if (oids[i] == OID_any_extended_key_usage) {
+			ret = 0;
+		}
+
+		switch (cert_type) {
+		case X509_cert_server_auth:
+		case X509_cert_server_key_encipher:
+			if (oids[i] == OID_kp_server_auth) {
+				return 1;
+			}
+			break;
+
+		case X509_cert_client_auth:
+		case X509_cert_client_key_encipher:
+			if (oids[i] == OID_kp_client_auth) {
+				return 1;
+			}
+			break;
+
+		default:
+			error_print();
+			return -1;
+		}
+	}
+	return ret;
+}
+
 int x509_ext_key_usage_print(FILE *fp, int fmt, int ind, const char *label, const uint8_t *d, size_t dlen)
 {
 	int oid;
@@ -1791,3 +1909,87 @@ int x509_netscape_cert_type_print(FILE *fp, int fmt, int ind, const char *label,
 		sizeof(netscape_cert_types)/sizeof(netscape_cert_types[0]), bits);
 }
 
+int x509_exts_validate(const uint8_t *exts, size_t extslen, int cert_type,
+	int *path_len_constraints)
+{
+	int oid;
+	uint32_t nodes[32];
+	size_t nodes_cnt;
+	int critical;
+	const uint8_t *val;
+	size_t vlen;
+
+	int ca = -1;
+	int path_len = -1;
+	int key_usage;
+	int ext_key_usages[X509_MAX_KEY_PURPOSES];
+	size_t ext_key_usages_cnt;
+
+	*path_len_constraints = -1;
+
+	while (extslen) {
+		if (x509_ext_from_der(&oid, nodes, &nodes_cnt, &critical, &val, &vlen, &exts, &extslen) != 1) {
+			error_print();
+			return -1;
+		}
+
+		switch (oid) {
+		case OID_ce_basic_constraints:
+			if (x509_basic_constraints_from_der(&ca, &path_len, &val, &vlen) != 1
+				|| x509_basic_constraints_validate(ca, path_len, cert_type) != 1) {
+				error_print();
+				return -1;
+			}
+			break;
+
+		case OID_ce_key_usage:
+			if (asn1_bits_from_der(&key_usage, &val, &vlen) != 1
+				|| x509_key_usage_validate(key_usage, cert_type) != 1) {
+				error_print();
+				return -1;
+			}
+			break;
+
+		case OID_ce_ext_key_usage:
+			if (x509_ext_key_usage_from_der(ext_key_usages, &ext_key_usages_cnt,
+					sizeof(ext_key_usages)/sizeof(ext_key_usages[0]), &val, &vlen) != 1
+				|| x509_ext_key_usage_validate(ext_key_usages, ext_key_usages_cnt, cert_type) != 1) {
+				error_print();
+				return -1;
+			}
+			break;
+
+		case OID_ce_authority_key_identifier:
+		case OID_ce_subject_key_identifier:
+		case OID_ce_certificate_policies:
+		case OID_ce_policy_mappings:
+		case OID_ce_subject_alt_name:
+		case OID_ce_issuer_alt_name:
+		case OID_ce_subject_directory_attributes:
+		case OID_ce_name_constraints:
+		case OID_ce_policy_constraints:
+		case OID_ce_crl_distribution_points:
+		case OID_ce_inhibit_any_policy:
+		case OID_ce_freshest_crl:
+		default:
+			if (critical) {
+				error_print();
+				return -1;
+			}
+		}
+	}
+
+	switch (cert_type) {
+	case X509_cert_ca:
+		if (ca != 1 || path_len < 0) {
+			error_print();
+			return -1;
+		}
+		*path_len_constraints = path_len;
+		break;
+	}
+
+	return 1;
+}
+
+

src/x509_oid.c

@@ -332,6 +332,8 @@ int x509_cert_policy_id_from_der(int *oid, uint32_t *nodes, size_t *nodes_cnt, c
 }
 
 
+static uint32_t oid_any_extended_key_usage[] = { oid_ce,37,0 };
+
 #define oid_kp oid_pkix,3
 
 static uint32_t oid_kp_server_auth[] = { oid_kp,1 };
@@ -343,6 +345,7 @@ static uint32_t oid_kp_ocsp_signing[] = { oid_kp,9 };
 #define OID_KP_CNT sizeof(oid_kp_server_auth)/sizeof(int)
 
 static const ASN1_OID_INFO x509_key_purposes[] = {
+	{ OID_any_extended_key_usage, "anyExtendedKeyUsage", oid_any_extended_key_usage, sizeof(oid_any_extended_key_usage)/sizeof(uint32_t), 0, "Any Extended Key Usage" },
 	{ OID_kp_server_auth, "serverAuth", oid_kp_server_auth, OID_KP_CNT, 0, "TLS WWW server authentication" },
 	{ OID_kp_client_auth, "clientAuth", oid_kp_client_auth, OID_KP_CNT, 0, "TLS WWW client authentication" },
 	{ OID_kp_code_signing, "codeSigning", oid_kp_code_signing, OID_KP_CNT, 0, "Signing of downloadable executable code" },