fix the domain name length limit checks

A domain name is at most 255 bytes long (RFC 1035), but the string
representation is two bytes smaller so the strlen maximum is 253.

1 files changed, 4 insertions, 4 deletions

diff --git a/src/network/res_querydomain.c b/src/network/res_querydomain.c
index c746dbe6..8ba31f45 100644
--- a/src/network/res_querydomain.c
+++ b/src/network/res_querydomain.c
@@ -3,10 +3,10 @@
 
 int res_querydomain(const char *name, const char *domain, int class, int type, unsigned char *dest, int len)
 {
-	char tmp[256];
-	size_t nl = strnlen(name, 256);
-	size_t dl = strnlen(domain, 256);
-	if (nl+dl+1 > 255) return -1;
+	char tmp[254];
+	size_t nl = strnlen(name, 254);
+	size_t dl = strnlen(domain, 254);
+	if (nl+dl+1 > 253) return -1;
 	memcpy(tmp, name, nl);
 	tmp[nl] = '.';
 	memcpy(tmp+nl+1, domain, dl+1);