Generate and send token to client if it's not present

mod_webgate.c

@@ -3,12 +3,63 @@ SPDX-License-Identifier: AGPL-3.0-or-later
 Copyright (C) 2026 mrkubax10 <mrkubax10@onet.pl>
 */
 
+#include <apr_base64.h>
 #include <httpd.h>
 #include <http_core.h>
+#include <http_protocol.h>
+#include <http_log.h>
+#include <stdbool.h>
 #include <stdio.h>
+#include <string.h>
+#include <util_cookies.h>
+#include <util_md5.h>
+
+static const char* const TOKEN_COOKIE_NAME = "webgate_token";
+
+// Returns true if user agent of client which performed the request looks like Git
+static bool check_user_agent_exception(request_rec* r) {
+	static const char GIT_USER_AGENT_PREFIX[] = "git/";
+	const char* const user_agent = apr_table_get(r->headers_in, "User-Agent");
+	if(!user_agent || strncmp(user_agent, GIT_USER_AGENT_PREFIX, sizeof(GIT_USER_AGENT_PREFIX))!=0)
+		return false;
+	return apr_table_get(r->headers_in, "Git-Protocol");
+}
+
+static char* generate_token(apr_pool_t* pool) {
+	char rnd[32];
+	apr_generate_random_bytes(rnd, sizeof(rnd));
+	char rnd_md5[APR_MD5_DIGESTSIZE];
+	apr_md5(rnd_md5, rnd, sizeof(rnd));
+
+	const apr_size_t encoded_size = apr_base64_encode_len(sizeof(rnd_md5));
+	char* output = apr_palloc(pool, encoded_size);
+	apr_base64_encode(output, rnd_md5, sizeof(rnd_md5));
+	return output;
+}
+
+// Generates new token and sets HTTP cookie containing it then presents client with challenge
+static void handle_challenge(request_rec* r) {
+	char* generated = generate_token(r->pool);
+	ap_cookie_write(r, TOKEN_COOKIE_NAME, generated, NULL, 0, r->headers_out, NULL);
+	ap_rprintf(r, "Token: %s\n", generated);
+}
+
+static int request_check_handler(request_rec* r) {
+	// Provide exception for requests performed by Git
+	if(check_user_agent_exception(r))
+		return DECLINED;
+	// Check if client already has the token
+	const char* token;
+	if(ap_cookie_read(r, TOKEN_COOKIE_NAME, &token, 0)!=APR_SUCCESS || !token) {
+		handle_challenge(r);
+		return OK;
+	}
+
+	return OK;
+}
 
 static void register_hooks(apr_pool_t* pool) {
-	printf("Registering hooks\n");
+	ap_hook_handler(request_check_handler, NULL, NULL, APR_HOOK_FIRST);
 }
 
 module AP_MODULE_DECLARE_DATA webgate_module = {