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authorFlorian Weimer <fweimer@redhat.com>2015-04-29 14:41:25 +0200
committerFlorian Weimer <fweimer@redhat.com>2015-04-29 14:41:26 +0200
commit03d2730b44cc2236318fd978afa2651753666c55 (patch)
tree8846df11bd7a2d2b8bd0be49dbf9d69654240e05 /nss/tst-nss-getpwent.c
parent7d0b2575416aec2717e8665287d0ab77826a0ade (diff)
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CVE-2014-8121: Do not close NSS files database during iteration [BZ #18007]
Robin Hack discovered Samba would enter an infinite loop processing certain quota-related requests. We eventually tracked this down to a glibc issue. Running a (simplified) test case under strace shows that /etc/passwd is continuously opened and closed: … open("/etc/passwd", O_RDONLY|O_CLOEXEC) = 3 lseek(3, 0, SEEK_CUR) = 0 read(3, "root:x:0:0:root:/root:/bin/bash\n"..., 4096) = 2717 lseek(3, 2717, SEEK_SET) = 2717 close(3) = 0 open("/etc/passwd", O_RDONLY|O_CLOEXEC) = 3 lseek(3, 0, SEEK_CUR) = 0 lseek(3, 0, SEEK_SET) = 0 read(3, "root:x:0:0:root:/root:/bin/bash\n"..., 4096) = 2717 lseek(3, 2717, SEEK_SET) = 2717 close(3) = 0 open("/etc/passwd", O_RDONLY|O_CLOEXEC) = 3 lseek(3, 0, SEEK_CUR) = 0 … The lookup function implementation in nss/nss_files/files-XXX.c:DB_LOOKUP has code to prevent that. It is supposed skip closing the input file if it was already open. /* Reset file pointer to beginning or open file. */ \ status = internal_setent (keep_stream); \ \ if (status == NSS_STATUS_SUCCESS) \ { \ /* Tell getent function that we have repositioned the file pointer. */ \ last_use = getby; \ \ while ((status = internal_getent (result, buffer, buflen, errnop \ H_ERRNO_ARG EXTRA_ARGS_VALUE)) \ == NSS_STATUS_SUCCESS) \ { break_if_match } \ \ if (! keep_stream) \ internal_endent (); \ } \ keep_stream is initialized from the stayopen flag in internal_setent. internal_setent is called from the set*ent implementation as: status = internal_setent (stayopen); However, for non-host database, this flag is always 0, per the STAYOPEN magic in nss/getXXent_r.c. Thus, the fix is this: - status = internal_setent (stayopen); + status = internal_setent (1); This is not a behavioral change even for the hosts database (where the application can specify the stayopen flag) because with a call to sethostent(0), the file handle is still not closed in the implementation of gethostent.
Diffstat (limited to 'nss/tst-nss-getpwent.c')
-rw-r--r--nss/tst-nss-getpwent.c118
1 files changed, 118 insertions, 0 deletions
diff --git a/nss/tst-nss-getpwent.c b/nss/tst-nss-getpwent.c
new file mode 100644
index 0000000..f2e8abc
--- /dev/null
+++ b/nss/tst-nss-getpwent.c
@@ -0,0 +1,118 @@
+/* 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/>. */
+
+#include <pwd.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int
+do_test (void)
+{
+ /* Count the number of entries in the password database, and fetch
+ data from the first and last entries. */
+ size_t count = 0;
+ struct passwd * pw;
+ char *first_name = NULL;
+ uid_t first_uid = 0;
+ char *last_name = NULL;
+ uid_t last_uid = 0;
+ setpwent ();
+ while ((pw = getpwent ()) != NULL)
+ {
+ if (first_name == NULL)
+ {
+ first_name = strdup (pw->pw_name);
+ if (first_name == NULL)
+ {
+ printf ("strdup: %m\n");
+ return 1;
+ }
+ first_uid = pw->pw_uid;
+ }
+
+ free (last_name);
+ last_name = strdup (pw->pw_name);
+ if (last_name == NULL)
+ {
+ printf ("strdup: %m\n");
+ return 1;
+ }
+ last_uid = pw->pw_uid;
+ ++count;
+ }
+ endpwent ();
+
+ if (count == 0)
+ {
+ printf ("No entries in the password database.\n");
+ return 0;
+ }
+
+ /* Try again, this time interleaving with name-based and UID-based
+ lookup operations. The counts do not match if the interleaved
+ lookups affected the enumeration. */
+ size_t new_count = 0;
+ setpwent ();
+ while ((pw = getpwent ()) != NULL)
+ {
+ if (new_count == count)
+ {
+ printf ("Additional entry in the password database.\n");
+ return 1;
+ }
+ ++new_count;
+ struct passwd *pw2 = getpwnam (first_name);
+ if (pw2 == NULL)
+ {
+ printf ("getpwnam (%s) failed: %m\n", first_name);
+ return 1;
+ }
+ pw2 = getpwnam (last_name);
+ if (pw2 == NULL)
+ {
+ printf ("getpwnam (%s) failed: %m\n", last_name);
+ return 1;
+ }
+ pw2 = getpwuid (first_uid);
+ if (pw2 == NULL)
+ {
+ printf ("getpwuid (%llu) failed: %m\n",
+ (unsigned long long) first_uid);
+ return 1;
+ }
+ pw2 = getpwuid (last_uid);
+ if (pw2 == NULL)
+ {
+ printf ("getpwuid (%llu) failed: %m\n",
+ (unsigned long long) last_uid);
+ return 1;
+ }
+ }
+ endpwent ();
+ if (new_count < count)
+ {
+ printf ("Missing entry in the password database.\n");
+ return 1;
+ }
+
+ return 0;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"