(parse_reply): verify the lengths (both external and internal) are

consistent and not too long
(dns_lookup_int): be conservative in the length sent in to to
parse_reply


git-svn-id: svn://svn.h5l.se/heimdal/trunk/heimdal@11239 ec53bebd-3082-4978-b11e-865c3cabbd6b

lib/roken/resolve.c

@@ -113,10 +113,10 @@ dns_free_data(struct dns_reply *r)
 static struct dns_reply*
 parse_reply(unsigned char *data, int len)
 {
-    unsigned char *p;
+    const unsigned char *p;
     char host[128];
     int status;
-    
+    const unsigned char *end_data = data + len;
     struct dns_reply *r;
     struct resource_record **rr;
     
@@ -133,7 +133,7 @@ parse_reply(unsigned char *data, int len)
     memcpy(&r->h, p, 12); /* XXX this will probably be mostly garbage */
     p += 12;
 #endif
-    status = dn_expand(data, data + len, p, host, sizeof(host));
+    status = dn_expand(data, end_data, p, host, sizeof(host));
     if(status < 0){
 	dns_free_data(r);
 	return NULL;
@@ -143,19 +143,27 @@ parse_reply(unsigned char *data, int len)
 	dns_free_data(r);
 	return NULL;
     }
+    if (p + status + 4 > end_data) {
+	dns_free_data(r);
+	return NULL;
+    }
     p += status;
     r->q.type = (p[0] << 8 | p[1]);
     p += 2;
     r->q.class = (p[0] << 8 | p[1]);
     p += 2;
     rr = &r->head;
-    while(p < data + len){
+    while(p < end_data){
 	int type, class, ttl, size;
-	status = dn_expand(data, data + len, p, host, sizeof(host));
+	status = dn_expand(data, end_data, p, host, sizeof(host));
 	if(status < 0){
 	    dns_free_data(r);
 	    return NULL;
 	}
+	if (p + status + 10 > end_data) {
+	    dns_free_data(r);
+	    return NULL;
+	}
 	p += status;
 	type = (p[0] << 8) | p[1];
 	p += 2;
@@ -165,6 +173,12 @@ parse_reply(unsigned char *data, int len)
 	p += 4;
 	size = (p[0] << 8) | p[1];
 	p += 2;
+
+	if (p + size > end_data) {
+	    dns_free_data(r);
+	    return NULL;
+	}
+
 	*rr = (struct resource_record*)calloc(1, 
 					      sizeof(struct resource_record));
 	if(*rr == NULL) {
@@ -184,7 +198,7 @@ parse_reply(unsigned char *data, int len)
 	case T_NS:
 	case T_CNAME:
 	case T_PTR:
-	    status = dn_expand(data, data + len, p, host, sizeof(host));
+	    status = dn_expand(data, end_data, p, host, sizeof(host));
 	    if(status < 0){
 		dns_free_data(r);
 		return NULL;
@@ -197,11 +211,16 @@ parse_reply(unsigned char *data, int len)
 	    break;
 	case T_MX:
 	case T_AFSDB:{
-	    status = dn_expand(data, data + len, p + 2, host, sizeof(host));
+	    status = dn_expand(data, end_data, p + 2, host, sizeof(host));
 	    if(status < 0){
 		dns_free_data(r);
 		return NULL;
 	    }
+	    if (status + 2 > size) {
+		dns_free_data(r);
+		return NULL;
+	    }
+
 	    (*rr)->u.mx = (struct mx_record*)malloc(sizeof(struct mx_record) + 
 						    strlen(host));
 	    if((*rr)->u.mx == NULL) {
@@ -213,11 +232,16 @@ parse_reply(unsigned char *data, int len)
 	    break;
 	}
 	case T_SRV:{
-	    status = dn_expand(data, data + len, p + 6, host, sizeof(host));
+	    status = dn_expand(data, end_data, p + 6, host, sizeof(host));
 	    if(status < 0){
 		dns_free_data(r);
 		return NULL;
 	    }
+	    if (status + 6 > size) {
+		dns_free_data(r);
+		return NULL;
+	    }
+
 	    (*rr)->u.srv = 
 		(struct srv_record*)malloc(sizeof(struct srv_record) + 
 					   strlen(host));
@@ -244,6 +268,11 @@ parse_reply(unsigned char *data, int len)
 	case T_KEY : {
 	    size_t key_len;
 
+	    if (size < 4) {
+		dns_free_data (r);
+		return NULL;
+	    }
+
 	    key_len = size - 4;
 	    (*rr)->u.key = malloc (sizeof(*(*rr)->u.key) + key_len - 1);
 	    if ((*rr)->u.key == NULL) {
@@ -261,11 +290,16 @@ parse_reply(unsigned char *data, int len)
 	case T_SIG : {
 	    size_t sig_len;
 
-	    status = dn_expand (data, data + len, p + 18, host, sizeof(host));
+	    status = dn_expand (data, end_data, p + 18, host, sizeof(host));
 	    if (status < 0) {
 		dns_free_data (r);
 		return NULL;
 	    }
+	    if (status + 18 > size) {
+		dns_free_data(r);
+		return NULL;
+	    }
+
 	    sig_len = len - 18 - status;
 	    (*rr)->u.sig = malloc(sizeof(*(*rr)->u.sig)
 				  + strlen(host) + sig_len);
@@ -293,6 +327,11 @@ parse_reply(unsigned char *data, int len)
 	case T_CERT : {
 	    size_t cert_len;
 
+	    if (size < 5) {
+		dns_free_data(r);
+		return NULL;
+	    }
+
 	    cert_len = size - 5;
 	    (*rr)->u.cert = malloc (sizeof(*(*rr)->u.cert) + cert_len - 1);
 	    if ((*rr)->u.cert == NULL) {
@@ -327,7 +366,6 @@ dns_lookup_int(const char *domain, int rr_class, int rr_type)
 {
     unsigned char reply[1024];
     int len;
-    struct dns_reply *r = NULL;
 #ifdef HAVE__RES
     u_long old_options = 0;
 #endif
@@ -348,9 +386,12 @@ dns_lookup_int(const char *domain, int rr_class, int rr_type)
 	fprintf(stderr, "dns_lookup(%s, %d, %s) --> %d\n",
 		domain, rr_class, dns_type_to_string(rr_type), len);
     }
-    if (len >= 0)
-	r = parse_reply(reply, len);
-    return r;
+    if(len < 0) {
+	return NULL;
+    } else {
+	len = min(len, sizeof(reply));
+	return parse_reply(reply, len);
+    }
 }
 
 struct dns_reply *