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authorDmitry V. Levin <ldv@altlinux.org>2018-01-07 02:03:41 +0000
committerDmitry V. Levin <ldv@altlinux.org>2018-01-12 14:49:49 +0000
commit52a713fdd0a30e1bd79818e2e3c4ab44ddca1a94 (patch)
tree54015de9e9109423e62967df2f6b0eb2b9a4284c /io
parent249a5895f120b13290a372a49bb4b499e749806f (diff)
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linux: make getcwd(3) fail if it cannot obtain an absolute path [BZ #22679]
Currently getcwd(3) can succeed without returning an absolute path because the underlying getcwd syscall, starting with linux commit v2.6.36-rc1~96^2~2, may succeed without returning an absolute path. This is a conformance issue because "The getcwd() function shall place an absolute pathname of the current working directory in the array pointed to by buf, and return buf". This is also a security issue because a non-absolute path returned by getcwd(3) causes a buffer underflow in realpath(3). Fix this by checking the path returned by getcwd syscall and falling back to generic_getcwd if the path is not absolute, effectively making getcwd(3) fail with ENOENT. The error code is chosen for consistency with the case when the current directory is unlinked. [BZ #22679] CVE-2018-1000001 * sysdeps/unix/sysv/linux/getcwd.c (__getcwd): Fall back to generic_getcwd if the path returned by getcwd syscall is not absolute. * io/tst-getcwd-abspath.c: New test. * io/Makefile (tests): Add tst-getcwd-abspath.
Diffstat (limited to 'io')
-rw-r--r--io/Makefile2
-rw-r--r--io/tst-getcwd-abspath.c66
2 files changed, 67 insertions, 1 deletions
diff --git a/io/Makefile b/io/Makefile
index 09b4f46..2117cb6 100644
--- a/io/Makefile
+++ b/io/Makefile
@@ -71,7 +71,7 @@ tests := test-utime test-stat test-stat2 test-lfs tst-getcwd \
tst-mknodat tst-mkfifoat tst-ttyname_r bug-ftw5 \
tst-posix_fallocate tst-posix_fallocate64 \
tst-fts tst-fts-lfs tst-open-tmpfile \
- tst-copy_file_range \
+ tst-copy_file_range tst-getcwd-abspath \
# This test includes the compat implementation of copy_file_range,
# which uses internal, unexported libc functions.
diff --git a/io/tst-getcwd-abspath.c b/io/tst-getcwd-abspath.c
new file mode 100644
index 0000000..3a3636f
--- /dev/null
+++ b/io/tst-getcwd-abspath.c
@@ -0,0 +1,66 @@
+/* BZ #22679 getcwd(3) should not succeed without returning an absolute path.
+
+ Copyright (C) 2018 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 <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/check.h>
+#include <support/namespace.h>
+#include <support/support.h>
+#include <support/temp_file.h>
+#include <support/test-driver.h>
+#include <support/xunistd.h>
+#include <unistd.h>
+
+static char *chroot_dir;
+
+/* The actual test. Run it in a subprocess, so that the test harness
+ can remove the temporary directory in --direct mode. */
+static void
+getcwd_callback (void *closure)
+{
+ xchroot (chroot_dir);
+
+ errno = 0;
+ char *cwd = getcwd (NULL, 0);
+ TEST_COMPARE (errno, ENOENT);
+ TEST_VERIFY (cwd == NULL);
+
+ errno = 0;
+ cwd = realpath (".", NULL);
+ TEST_COMPARE (errno, ENOENT);
+ TEST_VERIFY (cwd == NULL);
+
+ _exit (0);
+}
+
+static int
+do_test (void)
+{
+ support_become_root ();
+ if (!support_can_chroot ())
+ return EXIT_UNSUPPORTED;
+
+ chroot_dir = support_create_temp_directory ("tst-getcwd-abspath-");
+ support_isolate_in_subprocess (getcwd_callback, NULL);
+
+ return 0;
+}
+
+#include <support/test-driver.c>