Harden putpwent, putgrent, putspent, putspent against injection [BZ #18724]

This prevents injection of ':' and '\n' into output functions which
use the NSS files database syntax.  Critical fields (user/group names
and file system paths) are checked strictly.  For backwards
compatibility, the GECOS field is rewritten instead.

The getent program is adjusted to use the put*ent functions in libc,
instead of local copies.  This changes the behavior of getent if user
names start with '-' or '+'.

1 files changed, 101 insertions, 0 deletions

diff --git a/nss/tst-field.c b/nss/tst-field.c
new file mode 100644
index 0000000..f97d3ae
--- /dev/null
+++ b/nss/tst-field.c
@@ -0,0 +1,101 @@
+/* Test for invalid field handling in file-style NSS databases.  [BZ #18724]
+   Copyright (C) 2015 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
+   <http://www.gnu.org/licenses/>.  */
+
+/* This test needs to be statically linked because it access hidden
+   functions.  */
+
+#include <nss.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+static bool errors;
+
+static void
+check (const char *what, bool expr)
+{
+  if (!expr)
+    {
+      printf ("FAIL: %s\n", what);
+      errors = true;
+    }
+}
+
+#define CHECK(expr) check (#expr, (expr))
+
+static void
+check_rewrite (const char *input, const char *expected)
+{
+  char *to_free;
+  const char *result = __nss_rewrite_field (input, &to_free);
+  CHECK (result != NULL);
+  if (result != NULL && strcmp (result, expected) != 0)
+    {
+      printf ("FAIL: rewrite \"%s\" -> \"%s\", expected \"%s\"\n",
+	      input, result, expected);
+      errors = true;
+    }
+  free (to_free);
+}
+
+static int
+do_test (void)
+{
+  CHECK (__nss_valid_field (NULL));
+  CHECK (__nss_valid_field (""));
+  CHECK (__nss_valid_field ("+"));
+  CHECK (__nss_valid_field ("-"));
+  CHECK (__nss_valid_field (" "));
+  CHECK (__nss_valid_field ("abcdef"));
+  CHECK (__nss_valid_field ("abc def"));
+  CHECK (__nss_valid_field ("abc\tdef"));
+  CHECK (!__nss_valid_field ("abcdef:"));
+  CHECK (!__nss_valid_field ("abcde:f"));
+  CHECK (!__nss_valid_field (":abcdef"));
+  CHECK (!__nss_valid_field ("abcdef\n"));
+  CHECK (!__nss_valid_field ("\nabcdef"));
+  CHECK (!__nss_valid_field (":"));
+  CHECK (!__nss_valid_field ("\n"));
+
+  CHECK (__nss_valid_list_field (NULL));
+  CHECK (__nss_valid_list_field ((char *[]) {(char *) "good", NULL}));
+  CHECK (!__nss_valid_list_field ((char *[]) {(char *) "g,ood", NULL}));
+  CHECK (!__nss_valid_list_field ((char *[]) {(char *) "g\nood", NULL}));
+  CHECK (!__nss_valid_list_field ((char *[]) {(char *) "g:ood", NULL}));
+
+  check_rewrite (NULL, "");
+  check_rewrite ("", "");
+  check_rewrite ("abc", "abc");
+  check_rewrite ("abc\n", "abc ");
+  check_rewrite ("abc:", "abc ");
+  check_rewrite ("\nabc", " abc");
+  check_rewrite (":abc", " abc");
+  check_rewrite (":", " ");
+  check_rewrite ("\n", " ");
+  check_rewrite ("a:b:c", "a b c");
+  check_rewrite ("a\nb\nc", "a b c");
+  check_rewrite ("a\nb:c", "a b c");
+  check_rewrite ("aa\nbb\ncc", "aa bb cc");
+  check_rewrite ("aa\nbb:cc", "aa bb cc");
+
+  return errors;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"