parse stun attributes

daemon/str.h

@@ -47,6 +47,8 @@ static inline void str_init(str *out, char *s);
 static inline str *str_dup(const str *s);
 /* returns new str object allocated from chunk, including buffer */
 static inline str *str_chunk_insert(GStringChunk *c, const str *s);
+/* shifts pointer by len chars and decrements len. returns -1 if buffer too short, 0 otherwise */
+static inline int str_shift(str *s, int len);
 
 /* asprintf() analogs */
 #define str_sprintf(fmt, a...) __str_sprintf(STR_MALLOC_PADDING fmt, a)
@@ -74,6 +76,13 @@ static inline str *str_chunk_insert(GStringChunk *c, const str *s) {
 static inline char *str_end(const str *s) {
 	return s->s + s->len;
 }
+static inline int str_shift(str *s, int len) {
+	if (s->len < len)
+		return -1;
+	s->s += len;
+	s->len -= len;
+	return 0;
+}
 static inline char *str_chr(const str *s, int c) {
 	return memchr(s->s, c, s->len);
 }

daemon/stun.c

@@ -1,6 +1,10 @@
 #include "stun.h"
+
 #include <sys/types.h>
 
+#include "str.h"
+#include "aux.h"
+
 struct stun {
 	u_int16_t msg_type;
 	u_int16_t msg_len;
@@ -8,17 +12,96 @@ struct stun {
 	unsigned char transaction[12];
 } __attribute__ ((packed));
 
+struct tlv {
+	u_int16_t type;
+	u_int16_t len;
+	char value[0];
+} __attribute__ ((packed));
+
+struct stun_attrs {
+	str username;
+	str msg_integrity;
+	u_int32_t priority;
+	int use:1,
+	    controlled:1,
+	    controlling:1;
+};
+
+
+
+static int stun_attributes(struct stun_attrs *out, str *s) {
+	struct tlv *tlv;
+	int len;
+	str attr;
+
+	ZERO(*out);
+
+	while (1) {
+		if (!s->len)
+			return 0;
+
+		tlv = (void *) s->s;
+		if (str_shift(s, sizeof(*tlv)))
+			return -1;
+
+		len = ntohs(tlv->len);
+		attr = *s;
+		attr.len = len;
 
-int stun(const char *buf, int len) {
-	const struct stun *s = (const void *) buf;
+		len = (len + 3) & 0xfffc;
+		if (str_shift(s, len))
+			return -1;
+
+		switch (ntohs(tlv->type)) {
+			case 0x0006: /* username */
+				out->username = attr;
+				break;
+			case 0x0008: /* message-integrity */
+				out->msg_integrity = attr;
+				break;
+
+			case 0x0025: /* use-candidate */
+				out->use = 1;
+				break;
+			case 0x8029: /* ice-controlled */
+				out->controlled = 1;
+				break;
+			case 0x802a: /* ice-controlling */
+				out->controlling = 1;
+				break;
+
+			case 0x0024: /* priority */
+				if (attr.len != 4)
+					return -1;
+				out->priority = ntohl(*((u_int32_t *) attr.s));
+				break;
+		}
+	}
+
+	return 0;
+}
+
+/* XXX add error reporting */
+int stun(char *buf, int len) {
+	struct stun *s = (void *) buf;
 	int msglen, method, class;
+	str attr_str;
+	struct stun_attrs attrs;
 
 	msglen = ntohs(s->msg_len);
+	if (msglen + 20 > len || msglen < 0)
+		return -1;
+
 	class = method = ntohl(s->msg_type);
 	class = ((class & 0x10) >> 4) | ((class & 0x100) >> 7);
 	method = (method & 0xf) | ((method & 0xe0) >> 1) | ((method & 0x3e00) >> 2);
 	if (method != 0x1) /* binding */
 		return -1;
 
+	attr_str.s = &buf[20];
+	attr_str.len = len;
+	if (stun_attributes(&attrs, &attr_str))
+		return -1;
+
 	return 0;
 }

daemon/stun.h

@@ -24,7 +24,7 @@ static inline int is_stun(const char *bx, int len) {
 }
 
 
-int stun(const char *buf, int len);
+int stun(char *buf, int len);
 
 
 #endif