dns.c: add character range check + test

2 files changed, 20 insertions, 5 deletions

diff --git a/src/dns.c b/src/dns.c
index 9bdcd9b..50db12c 100644
--- a/src/dns.c
+++ b/src/dns.c
@@ -210,8 +210,10 @@ int fqdn_to_qname( char* _source, int _sourcelen, char* _sink ,int _sinklen )
 		_sink[i+1] = _source[i];
 	}
 
-	if( _source[i] ) /* _source not terminated, thus no valid string */
+	if( _source[i] ) {
+		_sink[0] = 0; /* ensure _sink is terminated */
 		return -1;
+	}
 
 	for (o = 0; o < i; o++) {
 		if( _sink[o] == '.') {
@@ -239,6 +241,7 @@ int qname_to_fqdn( char* _source, int _sourcelen, char* _sink, int _sinklen )
 
 	for(i = 1; i < (unsigned)_sourcelen; i++) {
 		if( i > (unsigned)_sinklen){ /* Output too small. Not >= bc sink[i-1] is used */
+			_sink[0] = 0; /* ensure _sink is terminated */
 			return -1;
 		}
 		if ( !_source[i] ) {
@@ -263,9 +266,7 @@ int qname_check( char* _source, int _sourcelen )
 	if (!_sourcelen)
 		return -1;
 
-
 	/* TODO questionable control flow */
-	/* TODO add ASCII prrintable check */
 	for (i = 0; i < _sourcelen; i++) {
 		if ( i == next_dot ) {
 			if (_source[i]) { /* Not last dot */
@@ -275,6 +276,13 @@ int qname_check( char* _source, int _sourcelen )
 			}
 		} else if (!_source[i]) { /* Unexpected \0 */
 			return -1;
+		} else if (
+			!(_source[i]>='0' && _source[i]<='9') &&
+			!(_source[i]>='A' && _source[i]<='Z') &&
+			!(_source[i]>='a' && _source[i]<='z') &&
+			!(_source[i]== '-') && !(_source[i]=='_')
+			) {
+			return -1;
 		}
 	}
 
diff --git a/tests/dns.c b/tests/dns.c
index e75f209..a282b8b 100644
--- a/tests/dns.c
+++ b/tests/dns.c
@@ -11,12 +11,19 @@
 START_TEST (dns_qname) {
 	char in[128];
 	char out[128];
+	char* fqdn = "sub.domain.example.com";
+	char* inval_fqdn = "is!this.domain.invalid?";
 
-	strncpy ( in, "sub.domain.example.com\0", 127);
+	strncpy ( in, fqdn , 127);
 
 	ck_assert_int_gt( fqdn_to_qname (in,128,out,128), 0 );
-	ck_assert_int_ge( qname_check(out,128), 0 );
+	ck_assert_int_ge( qname_check (out,128), 0 );
 	ck_assert_int_gt( qname_to_fqdn (out,128,in,128), 0);
+	ck_assert_str_eq( in, fqdn );
+
+	/* Check for working invalid protection */
+	ck_assert_int_gt( fqdn_to_qname (inval_fqdn,strlen(inval_fqdn),out,128), 0 );
+	ck_assert_int_lt( qname_check(out,128), 0 );
 } END_TEST
 
 START_TEST (dns_qname_fuzz) {