1 files changed, 72 insertions, 0 deletions
diff --git a/resolv/ns_name_length_uncompressed.c b/resolv/ns_name_length_uncompressed.c
new file mode 100644
index 0000000000..51296b47ef
--- /dev/null
+++ b/resolv/ns_name_length_uncompressed.c
@@ -0,0 +1,72 @@
+/* Skip over an uncompressed name in wire format.
+   Copyright (C) 2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <arpa/nameser.h>
+#include <errno.h>
+#include <stdbool.h>
+
+int
+__ns_name_length_uncompressed (const unsigned char *p,
+                                const unsigned char *eom)
+{
+  const unsigned char *start = p;
+
+  while (true)
+    {
+      if (p == eom)
+        {
+          /* Truncated packet: no room for label length.  */
+          __set_errno (EMSGSIZE);
+          return -1;
+        }
+
+      unsigned char b = *p;
+      ++p;
+      if (b == 0)
+        {
+          /* Root label.  */
+          size_t length = p - start;
+          if (length > NS_MAXCDNAME)
+            {
+              /* Domain name too long.  */
+              __set_errno (EMSGSIZE);
+              return -1;
+            }
+          return length;
+        }
+
+      if (b <= 63)
+        {
+          /* Regular label.  */
+          if (b <= eom - p)
+            p += b;
+          else
+            {
+              /* Truncated packet: label incomplete.  */
+              __set_errno (EMSGSIZE);
+              return -1;
+            }
+        }
+      else
+        {
+          /* Compression reference or corrupted label length.  */
+          __set_errno (EMSGSIZE);
+          return -1;
+        }
+    }
+}