From 14d8fc718f0c872274b90991ee634b0cd8e1a6f0 Mon Sep 17 00:00:00 2001
From: Sergey Poznyakoff <gray@gnu.org>
Date: Sat, 8 Feb 2020 13:01:47 +0200
Subject: [PATCH] Fix the --no-overwrite-dir option
Given this option, tar failed to preserve permissions of empty directories
and to create files under directories owned by the current user that did
not have the S_IWUSR bit set.
* src/extract.c (fd_chmod): Rename to fd_i_chmod.
(fd_chmod): New function.
(safe_dir_mode): New function.
(extract_dir): Special handling for existing directories in
--no-overwrite-dir mode.
* tests/extrac23.at: New file.
* tests/Makefile.am: Add new test case.
* tests/testsuite.at: Likewise.
---
src/extract.c | 128 ++++++++++++++++++++++++++++++---------------
tests/Makefile.am | 1 +
tests/extrac23.at | 58 ++++++++++++++++++++
tests/testsuite.at | 1 +
4 files changed, 146 insertions(+), 42 deletions(-)
create mode 100644 tests/extrac23.at
diff --git a/src/extract.c b/src/extract.c
index a4a35a57..5a38ba70 100644
--- a/src/extract.c
+++ b/src/extract.c
@@ -194,7 +194,7 @@ extr_init (void)
/* Use fchmod if possible, fchmodat otherwise. */
static int
-fd_chmod (int fd, char const *file, mode_t mode, int atflag)
+fd_i_chmod (int fd, char const *file, mode_t mode, int atflag)
{
if (0 <= fd)
{
@@ -205,6 +205,42 @@ fd_chmod (int fd, char const *file, mode_t mode, int atflag)
return fchmodat (chdir_fd, file, mode, atflag);
}
+/* A version of fd_i_chmod which gracefully handles several common error
+ conditions. Additional argument TYPEFLAG is the type of file in tar
+ notation.
+ */
+static int
+fd_chmod(int fd, char const *file_name, int mode, int atflag, int typeflag)
+{
+ int chmod_errno = fd_i_chmod (fd, file_name, mode, atflag) == 0 ? 0 : errno;
+
+ /* On Solaris, chmod may fail if we don't have PRIV_ALL, because
+ setuid-root files would otherwise be a backdoor. See
+ http://opensolaris.org/jive/thread.jspa?threadID=95826
+ (2009-09-03). */
+ if (chmod_errno == EPERM && (mode & S_ISUID)
+ && priv_set_restore_linkdir () == 0)
+ {
+ chmod_errno = fd_i_chmod (fd, file_name, mode, atflag) == 0 ? 0 : errno;
+ priv_set_remove_linkdir ();
+ }
+
+ /* Linux fchmodat does not support AT_SYMLINK_NOFOLLOW, and
+ returns ENOTSUP even when operating on non-symlinks, try
+ again with the flag disabled if it does not appear to be
+ supported and if the file is not a symlink. This
+ introduces a race, alas. */
+ if (atflag && typeflag != SYMTYPE && ! implemented (chmod_errno))
+ chmod_errno = fd_i_chmod (fd, file_name, mode, 0) == 0 ? 0 : errno;
+
+ if (chmod_errno && (typeflag != SYMTYPE || implemented (chmod_errno)))
+ {
+ errno = chmod_errno;
+ return -1;
+ }
+ return 0;
+}
+
/* Use fchown if possible, fchownat otherwise. */
static int
fd_chown (int fd, char const *file, uid_t uid, gid_t gid, int atflag)
@@ -259,35 +295,8 @@ set_mode (char const *file_name,
if (current_mode != mode)
{
- int chmod_errno =
- fd_chmod (fd, file_name, mode, atflag) == 0 ? 0 : errno;
-
- /* On Solaris, chmod may fail if we don't have PRIV_ALL, because
- setuid-root files would otherwise be a backdoor. See
- http://opensolaris.org/jive/thread.jspa?threadID=95826
- (2009-09-03). */
- if (chmod_errno == EPERM && (mode & S_ISUID)
- && priv_set_restore_linkdir () == 0)
- {
- chmod_errno =
- fd_chmod (fd, file_name, mode, atflag) == 0 ? 0 : errno;
- priv_set_remove_linkdir ();
- }
-
- /* Linux fchmodat does not support AT_SYMLINK_NOFOLLOW, and
- returns ENOTSUP even when operating on non-symlinks, try
- again with the flag disabled if it does not appear to be
- supported and if the file is not a symlink. This
- introduces a race, alas. */
- if (atflag && typeflag != SYMTYPE && ! implemented (chmod_errno))
- chmod_errno = fd_chmod (fd, file_name, mode, 0) == 0 ? 0 : errno;
-
- if (chmod_errno
- && (typeflag != SYMTYPE || implemented (chmod_errno)))
- {
- errno = chmod_errno;
- chmod_error_details (file_name, mode);
- }
+ if (fd_chmod (fd, file_name, mode, atflag, typeflag))
+ chmod_error_details (file_name, mode);
}
}
}
@@ -975,6 +984,26 @@ is_directory_link (const char *file_name)
return res;
}
+/* Given struct stat of a directory (or directory member) whose ownership
+ or permissions of will be restored later, return the temporary permissions
+ for that directory, sufficiently restrictive so that in the meantime
+ processes owned by other users do not inadvertently create files under this
+ directory that inherit the wrong owner, group, or permissions from the
+ directory.
+
+ If not root, though, make the directory writeable and searchable at first,
+ so that files can be created under it.
+*/
+static inline int
+safe_dir_mode (struct stat const *st)
+{
+ return ((st->st_mode
+ & (0 < same_owner_option || 0 < same_permissions_option
+ ? S_IRWXU
+ : MODE_RWX))
+ | (we_are_root ? 0 : MODE_WXUSR));
+}
+
/* Extractor functions for various member types */
static int
@@ -1004,18 +1033,7 @@ extract_dir (char *file_name, int typeflag)
else if (typeflag == GNUTYPE_DUMPDIR)
skip_member ();
- /* If ownership or permissions will be restored later, create the
- directory with restrictive permissions at first, so that in the
- meantime processes owned by other users do not inadvertently
- create files under this directory that inherit the wrong owner,
- group, or permissions from the directory. If not root, though,
- make the directory writeable and searchable at first, so that
- files can be created under it. */
- mode = ((current_stat_info.stat.st_mode
- & (0 < same_owner_option || 0 < same_permissions_option
- ? S_IRWXU
- : MODE_RWX))
- | (we_are_root ? 0 : MODE_WXUSR));
+ mode = safe_dir_mode (¤t_stat_info.stat);
for (;;)
{
@@ -1031,6 +1049,7 @@ extract_dir (char *file_name, int typeflag)
if (errno == EEXIST
&& (interdir_made
|| keep_directory_symlink_option
+ || old_files_option == NO_OVERWRITE_DIR_OLD_FILES
|| old_files_option == DEFAULT_OLD_FILES
|| old_files_option == OVERWRITE_OLD_FILES))
{
@@ -1051,6 +1070,31 @@ extract_dir (char *file_name, int typeflag)
repair_delayed_set_stat (file_name, &st);
return 0;
}
+ else if (old_files_option == NO_OVERWRITE_DIR_OLD_FILES)
+ {
+ /* Temporarily change the directory mode to a safe
+ value, to be able to create files in it, should
+ the need be.
+ */
+ mode = safe_dir_mode (&st);
+ status = fd_chmod(-1, file_name, mode,
+ AT_SYMLINK_NOFOLLOW, DIRTYPE);
+ if (status == 0)
+ {
+ /* Store the actual directory mode, to be restored
+ later.
+ */
+ current_stat_info.stat = st;
+ current_mode = mode & ~ current_umask;
+ current_mode_mask = MODE_RWX;
+ atflag = AT_SYMLINK_NOFOLLOW;
+ break;
+ }
+ else
+ {
+ chmod_error_details (file_name, mode);
+ }
+ }
break;
}
}
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 0369a950..31ae3460 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -121,6 +121,7 @@ TESTSUITE_AT = \
extrac19.at\
extrac20.at\
extrac21.at\
+ extrac23.at\
filerem01.at\
filerem02.at\
dirrem01.at\
diff --git a/tests/extrac23.at b/tests/extrac23.at
new file mode 100644
index 00000000..669d18b6
--- /dev/null
+++ b/tests/extrac23.at
@@ -0,0 +1,58 @@
+# Test suite for GNU tar. -*- Autotest -*-
+# Copyright 2020 Free Software Foundation, Inc.
+#
+# This file is part of GNU tar.
+#
+# GNU tar is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# GNU tar 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 General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+AT_SETUP([--no-overwrite-dir])
+AT_KEYWORDS([extract extrac23 no-overwrite-dir])
+
+# Description: Implementation of the --no-overwrite-dir option was flawed in
+# tar versions up to 1.32.90. This option is intended to preserve metadata
+# of existing directories. In fact it worked only for non-empty directories.
+# Moreover, if the actual directory was owned by the user tar runs as and the
+# S_IWUSR bit was not set in its actual permissions, tar failed to create files
+# in it.
+#
+# Reported by: Michael Kaufmann <mail@michael-kaufmann.ch>
+# References: <20200207112934.Horde.anXzYhAj2CHiwUrw5CuT0G-@webmail.michael-kaufmann.ch>,
+# https://lists.gnu.org/archive/html/bug-tar/2020-02/msg00003.html
+
+AT_TAR_CHECK([
+# Test if the directory permissions are restored properly.
+mkdir dir
+chmod 755 dir
+tar cf a.tar dir
+chmod 777 dir
+tar -xf a.tar --no-overwrite-dir
+genfile --stat=mode.777 dir
+
+# Test if temprorary permissions are set correctly to allow the owner
+# to write to the directory.
+genfile --file dir/file
+tar cf a.tar dir
+rm dir/file
+chmod 400 dir
+tar -xf a.tar --no-overwrite-dir
+genfile --stat=mode.777 dir
+chmod 700 dir
+find dir
+],
+[0],
+[777
+400
+dir
+dir/file
+])
+AT_CLEANUP
diff --git a/tests/testsuite.at b/tests/testsuite.at
index 2cc43a19..0620a3c7 100644
--- a/tests/testsuite.at
+++ b/tests/testsuite.at
@@ -343,6 +343,7 @@ m4_include([extrac19.at])
m4_include([extrac19.at])
m4_include([extrac20.at])
m4_include([extrac21.at])
+m4_include([extrac23.at])
m4_include([backup01.at])
--
2.37.3