resolv: Move ns_name_ntop to its own file and into libc

Reformat to GNU style.  Avoid out-of-bounds pointer arithmetic
(e.g., use eom - dn < 2 instead of dn + 1 >= eom).  Inline the
labellen function and fold the compression pointer check into
the length check (l >= 64).  Assume ASCII encoding.

The symbol was moved using scripts/move-symbol-to-libc.py.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>

1 files changed, 145 insertions, 0 deletions

diff --git a/resolv/ns_name_ntop.c b/resolv/ns_name_ntop.c
new file mode 100644
index 0000000000..4dab3a3ce0
--- /dev/null
+++ b/resolv/ns_name_ntop.c
@@ -0,0 +1,145 @@
+/* Convert DNS domain names from network format to textual presentation format.
+ * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
+ * Copyright (c) 1996,1999 by Internet Software Consortium.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
+ * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <arpa/nameser.h>
+#include <errno.h>
+#include <shlib-compat.h>
+#include <stdbool.h>
+
+/* Thinking in noninternationalized US-ASCII (per the DNS spec), is
+   this character special ("in need of quoting")?  */
+static inline bool
+special (int ch)
+{
+  switch (ch)
+    {
+    case '"':
+    case '.':
+    case ';':
+    case '\\':
+    case '(':
+    case ')':
+      /* Special modifiers in zone files.  */
+    case '@':
+    case '$':
+      return true;
+    default:
+      return false;
+    }
+}
+
+/* Thinking in noninternationalized US-ASCII (per the DNS spec), is
+   this character visible and not a space when printed?  */
+static inline bool
+printable (int ch)
+{
+  return ch > 0x20 && ch < 0x7f;
+}
+
+/* Converts an uncompressed, encoded domain name to printable ASCII as
+   per RFC1035.  Returns the number of bytes written to buffer, or -1
+   (with errno set).  The root is returned as "."  All other domains
+   are returned in non absolute form.  */
+int
+___ns_name_ntop (const unsigned char *src, char *dst, size_t dstsiz)
+{
+  const unsigned char *cp;
+  char *dn, *eom;
+  unsigned char c;
+  int l;
+
+  cp = src;
+  dn = dst;
+  eom = dst + dstsiz;
+
+  while ((l = *cp++) != 0)
+    {
+      if (l >= 64)
+        {
+          /* Some kind of compression pointer.  */
+          __set_errno (EMSGSIZE);
+          return -1;
+        }
+      if (dn != dst)
+        {
+          if (dn >= eom)
+            {
+              __set_errno (EMSGSIZE);
+              return -1;
+            }
+          *dn++ = '.';
+        }
+      for (; l > 0; l--)
+        {
+          c = *cp++;
+          if (special (c))
+            {
+              if (eom - dn < 2)
+                {
+                  __set_errno (EMSGSIZE);
+                  return -1;
+                }
+              *dn++ = '\\';
+              *dn++ = c;
+            }
+          else if (!printable (c))
+            {
+              if (eom - dn < 4)
+                {
+                  __set_errno (EMSGSIZE);
+                  return -1;
+                }
+              *dn++ = '\\';
+              *dn++ = '0' + (c / 100);
+              *dn++ = '0' + ((c % 100) / 10);
+              *dn++ = '0' + (c % 10);
+            }
+          else
+            {
+              if (eom - dn < 2)
+                {
+                  __set_errno (EMSGSIZE);
+                  return -1;
+                }
+              *dn++ = c;
+            }
+        }
+    }
+  if (dn == dst)
+    {
+      if (dn >= eom)
+        {
+          __set_errno (EMSGSIZE);
+          return -1;
+        }
+      *dn++ = '.';
+    }
+  if (dn >= eom)
+    {
+      __set_errno (EMSGSIZE);
+      return -1;
+    }
+  *dn++ = '\0';
+  return dn - dst;
+}
+versioned_symbol (libc, ___ns_name_ntop, ns_name_ntop, GLIBC_2_34);
+versioned_symbol (libc, ___ns_name_ntop, __ns_name_ntop, GLIBC_PRIVATE);
+libc_hidden_ver (___ns_name_ntop, __ns_name_ntop)
+
+#if OTHER_SHLIB_COMPAT (libresolv, GLIBC_2_9, GLIBC_2_34)
+compat_symbol (libresolv, ___ns_name_ntop, ns_name_ntop, GLIBC_2_9);
+#endif