dhcp6: refuse zero length dhcp user class

This also fixes a memory leak when
sd_dhcp6_client_set_request_user_class() is called multiple times.

1 files changed, 8 insertions, 5 deletions

diff --git a/src/libsystemd-network/dhcp6-option.c b/src/libsystemd-network/dhcp6-option.c
index e2bf4f7e36..8151e66bca 100644
--- a/src/libsystemd-network/dhcp6-option.c
+++ b/src/libsystemd-network/dhcp6-option.c
@@ -200,19 +200,22 @@ int dhcp6_option_append_fqdn(uint8_t **buf, size_t *buflen, const char *fqdn) {
         return r;
 }
 
-int dhcp6_option_append_user_class(uint8_t **buf, size_t *buflen, char **user_class) {
+int dhcp6_option_append_user_class(uint8_t **buf, size_t *buflen, char * const *user_class) {
         _cleanup_free_ uint8_t *p = NULL;
         size_t total = 0, offset = 0;
-        char **s;
+        char * const *s;
 
-        assert_return(buf && *buf && buflen && user_class, -EINVAL);
+        assert(buf);
+        assert(*buf);
+        assert(buflen);
+        assert(!strv_isempty(user_class));
 
         STRV_FOREACH(s, user_class) {
                 size_t len = strlen(*s);
                 uint8_t *q;
 
-                if (len > 0xffff)
-                        return -ENAMETOOLONG;
+                if (len > 0xffff || len == 0)
+                        return -EINVAL;
                 q = realloc(p, total + len + 2);
                 if (!q)
                         return -ENOMEM;