From 67e53c2fff6f1a25b3929b998b1fc6ee3cb116a4 Mon Sep 17 00:00:00 2001
From: Erik Ekman <yarrick@kryo.se>
Date: Sun, 5 Nov 2006 11:44:43 +0000
Subject: [PATCH] Fixed hostname encoding, cleanup

---
 dns.c  | 16 +++++++++++-----
 dns.h  |  1 +
 test.c | 28 ++++++++++++++++++++++++++++
 3 files changed, 40 insertions(+), 5 deletions(-)

diff --git a/dns.c b/dns.c
index 96bd5e8..460932f 100644
--- a/dns.c
+++ b/dns.c
@@ -43,7 +43,6 @@
 #endif
 
 
-static int host2dns(const char *, char *, int);
 static int dns_write(int, int, char *, int, char);
 static void dns_query(int, int, char *, int);
 
@@ -207,7 +206,7 @@ dns_query(int fd, int id, char *host, int type)
 	header->arcount = htons(1);
 
 	p = buf + sizeof(HEADER);
-	p += host2dns(host, p, strlen(host));	
+	p += dns_encode_hostname(host, p, strlen(host));	
 
 	putshort(&p, type);
 	putshort(&p, C_IN);
@@ -325,6 +324,7 @@ dns_parse_reply(char *outbuf, int buflen, char *packet, int packetlen)
 		}
 
 		if(type == T_NULL && rv > 2) {
+			rv = MIN(rv, buflen);
 			memcpy(outbuf, rdata, rv);
 		}
 	}
@@ -332,19 +332,25 @@ dns_parse_reply(char *outbuf, int buflen, char *packet, int packetlen)
 	return rv;
 }
 
-static int
-host2dns(const char *host, char *buffer, int size)
+int
+dns_encode_hostname(const char *host, char *buffer, int size)
 {
 	char *h;
 	char *p;
 	char *word;
+	int left;
 
 	h = strdup(host);
 	memset(buffer, 0, size);
 	p = buffer;
+	left = size;
 	
 	word = strtok(h, ".");
 	while(word) {
+		if (strlen(word) > 63 || strlen(word) > left) {
+			return -1;
+		}
+		left -= (strlen(word) + 1);
 		*p++ = (char)strlen(word);
 		memcpy(p, word, strlen(word));
 		p += strlen(word);
@@ -387,7 +393,7 @@ dnsd_send(int fd, struct query *q, char *data, int datalen)
 	p = buf + sizeof(HEADER);
 	
 	name = 0xc000 | ((p - buf) & 0x3fff);
-	p += host2dns(q->name, p, strlen(q->name));
+	p += dns_encode_hostname(q->name, p, strlen(q->name));
 	putshort(&p, q->type);
 	putshort(&p, C_IN);
 
diff --git a/dns.h b/dns.h
index f3807a1..f8da628 100644
--- a/dns.h
+++ b/dns.h
@@ -26,6 +26,7 @@ void dns_handle_tun(int, char *, int);
 void dns_ping(int);
 void dns_handshake(int);
 int dns_read(int, char *, int);
+int dns_encode_hostname(const char *, char *, int);
 
 extern struct sockaddr_in peer;
 
diff --git a/test.c b/test.c
index 4125ebe..19050df 100644
--- a/test.c
+++ b/test.c
@@ -162,6 +162,33 @@ test_readname()
 	printf("OK\n");
 }
 
+static void
+test_encode_hostname() {
+	char buf[256];
+	int len;
+	int ret;
+
+	len = 256;
+	printf(" * Testing hostname encoding... ");
+
+	memset(buf, 0, 256);
+	ret = dns_encode_hostname(	// More than 63 chars between dots
+		"ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ"
+		, buf, len);
+	assert(ret == -1);
+	
+	memset(buf, 0, 256);
+	ret = dns_encode_hostname(	// More chars than fits into array
+		"ABCDEFGHIJKLMNOPQRSTUVWXYZ.ABCDEFGHIJKLMNOPQRSTUVWXYZ.ABCDEFGHIJKLMNOPQRSTUVWXYZ.ABCDEFGHIJKLMNOPQRSTUVWXYZ."
+		"ABCDEFGHIJKLMNOPQRSTUVWXYZ.ABCDEFGHIJKLMNOPQRSTUVWXYZ.ABCDEFGHIJKLMNOPQRSTUVWXYZ.ABCDEFGHIJKLMNOPQRSTUVWXYZ."
+		"ABCDEFGHIJKLMNOPQRSTUVWXYZ.ABCDEFGHIJKLMNOPQRSTUVWXYZ.ABCDEFGHIJKLMNOPQRSTUVWXYZ.ABCDEFGHIJKLMNOPQRSTUVWXYZ."
+		, buf, len);
+	assert(ret == -1);
+	assert(strlen(buf) < len);
+	
+	printf("OK\n");
+}
+
 int
 main()
 {
@@ -170,6 +197,7 @@ main()
 	test_readputshort();
 	test_readputlong();
 	test_readname();
+	test_encode_hostname();
 
 	printf("** All went well :)\n");
 	return 0;