ish2.c

/*
 * ish2.c: an HTTP/2 support check tool via ALPN.
 */

#include <err.h>
#include <stdio.h>
#include <string.h>

#include <openssl/err.h>
#include <openssl/ssl.h>

#define TARGET_SIZE	1024

const unsigned char protos[] = {2, 'h', '2', 8, 'h', 't', 't', 'p', '/', '1', '.', '1'};

void exit_program(const char* host, const char* msg, SSL_CTX* ctx, BIO* bio) {

	fprintf(stderr, "%s: %s\n", host, msg ? msg : ERR_error_string(ERR_get_error(), NULL));

	BIO_free_all(bio);
	SSL_CTX_free(ctx);
	exit(EXIT_FAILURE);
}

static void __strtrunc(char* str, char c) {
	char* ptr = strchr(str, c);
	if (ptr)
		*ptr = '\0';
}

int parse_args(char* target, size_t target_size, const char* host, const char* port) {
	char* ptr;

	/* Remove protocol scheme if present */	
	ptr = strstr(host, "://");
	if (ptr) {
		if (ptr[3] == '\0')
			return -1;
		strncpy(target, ptr + 3, target_size - 1);
	} else {
		strncpy(target, host, target_size - 1);
	}

	/* Remove web path and port if present */
	__strtrunc(target, '/');
	__strtrunc(target, ':');

	/* Check for overflow and write final target string */
	if ((strlen(target) + strlen(port) + 2) > target_size)
		return -1;
	
	strcat(strcat(target, ":"), port);

	return 0;
}

int main(int argc, char *argv[]) {
	char *port;
	char target[TARGET_SIZE] = {0};
	char hostname[TARGET_SIZE] = {0};
	const unsigned char* alpn_proto;
	unsigned int alpn_length;
	const SSL_METHOD* method;
	SSL_CTX* ctx = NULL;
	BIO* bio = NULL;
	SSL* ssl = NULL;

	if (argc < 2)
		errx(EXIT_SUCCESS, "%s <host> [port]", argv[0]);

	if (argc > 2) {
		port = argv[2];
	} else {
		port = "443";
	}

	if (parse_args(target, TARGET_SIZE, argv[1], port) < 0)
		exit_program(argv[1], "error: input too long or invalid format", ctx, bio);

	/* Copy target without port into hostname */
	strncpy(hostname, target, TARGET_SIZE - 1);
	__strtrunc(hostname, ':');

	/* Set up SSL method and context */
	method = TLS_client_method();
	if (method == NULL)
		exit_program(hostname, NULL, ctx, bio);

	ctx = SSL_CTX_new(method);
	if (ctx == NULL)
		exit_program(hostname, NULL, ctx, bio);

#ifdef NVERIFY
	/* Do not verify certificates */
	SSL_CTX_set_verify(ctx, SSL_VERIFY_NONE, NULL);
#endif

	/* Set ALPN */
	if (SSL_CTX_set_alpn_protos(ctx, protos, sizeof(protos)) != 0)
		exit_program(hostname, NULL, ctx, bio);

	bio = BIO_new_ssl_connect(ctx);
	if (bio == NULL)
		exit_program(hostname, NULL, ctx, bio);

	/* Set hostname */
	if (BIO_set_conn_hostname(bio, target) != 1)
		exit_program(hostname, NULL, ctx, bio);

	/* Set SNI */
	if (BIO_get_ssl(bio, &ssl) <= 0 || SSL_set_tlsext_host_name(ssl, hostname) != 1)
		exit_program(hostname, NULL, ctx, bio);

	/* Connect */
	if (BIO_do_connect(bio) != 1 || BIO_do_handshake(bio) != 1)
		exit_program(hostname, NULL, ctx, bio);

	/* Print result */
	SSL_get0_alpn_selected(ssl, &alpn_proto, &alpn_length);
	if (alpn_proto != NULL) {
		printf("%s %.*s\n", hostname, alpn_length, alpn_proto);
	} else {
		printf("%s http/1.1\n", hostname);
	}

	SSL_CTX_free(ctx);
	BIO_free_all(bio);

	return EXIT_SUCCESS;
}