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-rw-r--r--src/shared/dns-domain.c19
1 files changed, 15 insertions, 4 deletions
diff --git a/src/shared/dns-domain.c b/src/shared/dns-domain.c
index ba6eff8f60..03c0107308 100644
--- a/src/shared/dns-domain.c
+++ b/src/shared/dns-domain.c
@@ -864,7 +864,7 @@ bool dns_name_is_single_label(const char *name) {
return dns_name_is_root(name);
}
-/* Encode a domain name according to RFC 1035 Section 3.1 */
+/* Encode a domain name according to RFC 1035 Section 3.1, without compression */
int dns_name_to_wire_format(const char *domain, uint8_t *buffer, size_t len) {
uint8_t *label_length, *out;
int r;
@@ -875,24 +875,35 @@ int dns_name_to_wire_format(const char *domain, uint8_t *buffer, size_t len) {
out = buffer;
do {
- /* reserve a byte for label length */
+ /* Reserve a byte for label length */
if (len <= 0)
return -ENOBUFS;
len--;
label_length = out;
out++;
- /* convert and copy a single label */
+ /* Convert and copy a single label. Note that
+ * dns_label_unescape() returns 0 when it hits the end
+ * of the domain name, which we rely on here to encode
+ * the trailing NUL byte. */
r = dns_label_unescape(&domain, (char *) out, len);
if (r < 0)
return r;
- /* fill label length, move forward */
+ /* Fill label length, move forward */
*label_length = r;
out += r;
len -= r;
+
} while (r != 0);
+ /* Verify the maximum size of the encoded name. The trailing
+ * dot + NUL byte account are included this time, hence
+ * compare against DNS_HOSTNAME_MAX + 2 (which is 255) this
+ * time. */
+ if (out - buffer > DNS_HOSTNAME_MAX + 2)
+ return -EINVAL;
+
return out - buffer;
}