static int verify_server_cert()

in src/streams/openssl.c [484:615]

• 102 lines of code
• 25 McCabe index (conditional complexity)

static int verify_server_cert(SSL *ssl, const char *host)
{
	X509 *cert = NULL;
	X509_NAME *peer_name;
	ASN1_STRING *str;
	unsigned char *peer_cn = NULL;
	int matched = -1, type = GEN_DNS;
	GENERAL_NAMES *alts;
	struct in6_addr addr6;
	struct in_addr addr4;
	void *addr = NULL;
	int i = -1, j, error = 0;

	if (SSL_get_verify_result(ssl) != X509_V_OK) {
		git_error_set(GIT_ERROR_SSL, "the SSL certificate is invalid");
		return GIT_ECERTIFICATE;
	}

	/* Try to parse the host as an IP address to see if it is */
	if (p_inet_pton(AF_INET, host, &addr4)) {
		type = GEN_IPADD;
		addr = &addr4;
	} else {
		if (p_inet_pton(AF_INET6, host, &addr6)) {
			type = GEN_IPADD;
			addr = &addr6;
		}
	}


	cert = SSL_get_peer_certificate(ssl);
	if (!cert) {
		error = -1;
		git_error_set(GIT_ERROR_SSL, "the server did not provide a certificate");
		goto cleanup;
	}

	/* Check the alternative names */
	alts = X509_get_ext_d2i(cert, NID_subject_alt_name, NULL, NULL);
	if (alts) {
		int num;

		num = sk_GENERAL_NAME_num(alts);
		for (i = 0; i < num && matched != 1; i++) {
			const GENERAL_NAME *gn = sk_GENERAL_NAME_value(alts, i);
			const char *name = (char *) ASN1_STRING_get0_data(gn->d.ia5);
			size_t namelen = (size_t) ASN1_STRING_length(gn->d.ia5);

			/* Skip any names of a type we're not looking for */
			if (gn->type != type)
				continue;

			if (type == GEN_DNS) {
				/* If it contains embedded NULs, don't even try */
				if (memchr(name, '\0', namelen))
					continue;

				if (check_host_name(name, host) < 0)
					matched = 0;
				else
					matched = 1;
			} else if (type == GEN_IPADD) {
				/* Here name isn't so much a name but a binary representation of the IP */
				matched = addr && !!memcmp(name, addr, namelen);
			}
		}
	}
	GENERAL_NAMES_free(alts);

	if (matched == 0)
		goto cert_fail_name;

	if (matched == 1) {
		goto cleanup;
	}

	/* If no alternative names are available, check the common name */
	peer_name = X509_get_subject_name(cert);
	if (peer_name == NULL)
		goto on_error;

	if (peer_name) {
		/* Get the index of the last CN entry */
		while ((j = X509_NAME_get_index_by_NID(peer_name, NID_commonName, i)) >= 0)
			i = j;
	}

	if (i < 0)
		goto on_error;

	str = X509_NAME_ENTRY_get_data(X509_NAME_get_entry(peer_name, i));
	if (str == NULL)
		goto on_error;

	/* Work around a bug in OpenSSL whereby ASN1_STRING_to_UTF8 fails if it's already in utf-8 */
	if (ASN1_STRING_type(str) == V_ASN1_UTF8STRING) {
		int size = ASN1_STRING_length(str);

		if (size > 0) {
			peer_cn = OPENSSL_malloc(size + 1);
			GIT_ERROR_CHECK_ALLOC(peer_cn);
			memcpy(peer_cn, ASN1_STRING_get0_data(str), size);
			peer_cn[size] = '\0';
		} else {
			goto cert_fail_name;
		}
	} else {
		int size = ASN1_STRING_to_UTF8(&peer_cn, str);
		GIT_ERROR_CHECK_ALLOC(peer_cn);
		if (memchr(peer_cn, '\0', size))
			goto cert_fail_name;
	}

	if (check_host_name((char *)peer_cn, host) < 0)
		goto cert_fail_name;

	goto cleanup;

cert_fail_name:
	error = GIT_ECERTIFICATE;
	git_error_set(GIT_ERROR_SSL, "hostname does not match certificate");
	goto cleanup;

on_error:
	error = ssl_set_error(ssl, 0);
	goto cleanup;

cleanup:
	X509_free(cert);
	OPENSSL_free(peer_cn);
	return error;
}