From 95fde8b3eec9835d1c7f1ad7abde1d89eaa25b0e Mon Sep 17 00:00:00 2001
From: Erik Ekman <erik@kryo.se>
Date: Wed, 25 Aug 2021 01:04:31 +0200
Subject: [PATCH] Handle wildcard prefix of allowed tunnel domain names

---
 README.md     |  5 +++++
 man/iodine.8  |  3 ++-
 src/iodined.c | 24 ++++++++++--------------
 3 files changed, 17 insertions(+), 15 deletions(-)

diff --git a/README.md b/README.md
index d867fcf..480ba54 100644
--- a/README.md
+++ b/README.md
@@ -288,6 +288,11 @@ quence, assuming at most one client will be connected at any time. A small
 DNSCACHE_LEN is still advised, preferably 2 or higher, however you can also
 undefine it to save a few more kilobytes.
 
+One iodine server can handle multiple domains. Set up different NS records
+on the same domain all pointing to the same host, and use `\*.mydomain.com`
+as topdomain argument. iodine will accept tunnel traffic for all domains matching that
+pattern.
+
 
 PERFORMANCE
 -----------
diff --git a/man/iodine.8 b/man/iodine.8
index 8b927da..9b0cb81 100644
--- a/man/iodine.8
+++ b/man/iodine.8
@@ -337,7 +337,8 @@ subdomains under 'topdomain'. This is normally a subdomain to a domain you
 own. Use a short domain name to get better throughput. This argument must be
 the same on both the client and the server. Queries for domains other
 than 'topdomain' will be forwarded when the \-b option is given, otherwise
-they will be dropped.
+they will be dropped. The topdomain can start with '*' which will allow all
+domains ending with the same suffix.
 .SH EXAMPLES
 See the README file for both a quick test scenario, and a detailed description
 of real-world deployment.
diff --git a/src/iodined.c b/src/iodined.c
index 0212475..f955516 100644
--- a/src/iodined.c
+++ b/src/iodined.c
@@ -1523,11 +1523,13 @@ handle_null_request(int tun_fd, int dns_fd, struct dnsfd *dns_fds, struct query
 }
 
 static void
-handle_ns_request(int dns_fd, struct query *q)
+handle_ns_request(int dns_fd, struct query *q, int topdomain_offset)
 /* Mostly identical to handle_a_request() below */
 {
 	char buf[64*1024];
 	int len;
+	/* Use possibly dynamic top domain in reply */
+	char *resp_domain = q->name + topdomain_offset;
 
 	if (ns_ip != INADDR_ANY) {
 		/* If ns_ip set, overwrite destination addr with it.
@@ -1538,7 +1540,7 @@ handle_ns_request(int dns_fd, struct query *q)
 		q->dest_len = sizeof(*addr);
 	}
 
-	len = dns_encode_ns_response(buf, sizeof(buf), q, topdomain);
+	len = dns_encode_ns_response(buf, sizeof(buf), q, resp_domain);
 	if (len < 1) {
 		warnx("dns_encode_ns_response doesn't fit");
 		return;
@@ -1683,7 +1685,6 @@ tunnel_dns(int tun_fd, int dns_fd, struct dnsfd *dns_fds, int bind_fd)
 	struct query q;
 	int read;
 	int domain_len;
-	int inside_topdomain = 0;
 
 	if ((read = read_dns(dns_fd, dns_fds, tun_fd, &q)) <= 0)
 		return 0;
@@ -1693,14 +1694,8 @@ tunnel_dns(int tun_fd, int dns_fd, struct dnsfd *dns_fds, int bind_fd)
 			format_addr(&q.from, q.fromlen), q.type, q.name);
 	}
 
-	domain_len = strlen(q.name) - strlen(topdomain);
-	if (domain_len >= 0 && !strcasecmp(q.name + domain_len, topdomain))
-		inside_topdomain = 1;
-	/* require dot before topdomain */
-	if (domain_len >= 1 && q.name[domain_len - 1] != '.')
-		inside_topdomain = 0;
-
-	if (inside_topdomain) {
+	domain_len = query_datalen(q.name, topdomain);
+	if (domain_len >= 0) {
 		/* This is a query we can handle */
 
 		/* Handle A-type query for ns.topdomain, possibly caused
@@ -1736,7 +1731,7 @@ tunnel_dns(int tun_fd, int dns_fd, struct dnsfd *dns_fds, int bind_fd)
 			handle_null_request(tun_fd, dns_fd, dns_fds, &q, domain_len);
 			break;
 		case T_NS:
-			handle_ns_request(dns_fd, &q);
+			handle_ns_request(dns_fd, &q, domain_len);
 			break;
 		default:
 			break;
@@ -2327,7 +2322,8 @@ static void help(FILE *stream)
 		"  -i maximum idle time before shutting down\n\n"
 		"tunnel_ip is the IP number of the local tunnel interface.\n"
 		"   /netmask sets the size of the tunnel network.\n"
-		"topdomain is the FQDN that is delegated to this server.\n");
+		"topdomain is the FQDN that is delegated to this server.\n"
+		"   Initial wildcard is allowed (example: *.tun.com)\n");
 
 	exit(0);
 }
@@ -2543,7 +2539,7 @@ main(int argc, char **argv)
 	}
 
 	topdomain = strdup(argv[1]);
-	if (check_topdomain(topdomain, 0, &errormsg)) {
+	if (check_topdomain(topdomain, 1, &errormsg)) {
 		warnx("Invalid topdomain: %s", errormsg);
 		usage();
 		/* NOTREACHED */