Package: squashfs-tools
Version: 1:4.3-6
Severity: normal
Tags: patch
User: ubuntu-de...@lists.ubuntu.com
Usertags: origin-ubuntu cosmic ubuntu-patch
Dear Maintainer,
In Ubuntu, the attached patch was applied to achieve the following:
* debian/patches/0010-use-macros-not-raw-octal-with-chmod.patch,
debian/patches/0011-also-set-stickybit-as-non-root.patch: apply stickybit
when run as non-root (LP: #1779914). Patches thanks to Tyler Hicks.
Thanks for considering the patch.
Reference:
* https://sourceforge.net/p/squashfs/mailman/message/36343213/
-- System Information:
Debian Release: buster/sid
APT prefers bionic-updates
APT policy: (500, 'bionic-updates'), (500, 'bionic-security'), (500, 'bionic')
Architecture: amd64 (x86_64)
Foreign Architectures: i386
Kernel: Linux 4.15.0-23-generic (SMP w/2 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8),
LANGUAGE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled
diff -Nru
squashfs-tools-4.3/debian/patches/0010-use-macros-not-raw-octal-with-chmod.patch
squashfs-tools-4.3/debian/patches/0010-use-macros-not-raw-octal-with-chmod.patch
---
squashfs-tools-4.3/debian/patches/0010-use-macros-not-raw-octal-with-chmod.patch
1969-12-31 18:00:00.000000000 -0600
+++
squashfs-tools-4.3/debian/patches/0010-use-macros-not-raw-octal-with-chmod.patch
2018-07-03 12:55:57.000000000 -0500
@@ -0,0 +1,32 @@
+Author: Tyler Hicks <tyhi...@canonical.com>
+Origin: backport, https://sourceforge.net/p/squashfs/mailman/message/36343213/
+Description: Using macros, rather than raw octal values, better conveys the
+ intent of masking off the setuid, setgid, and sticky bits.
+Forwarded: yes
+Bug-Ubuntu: https://launchpad.net/bugs/1779914
+
+Index: squashfs-tools-4.3/squashfs-tools/unsquashfs.c
+===================================================================
+--- squashfs-tools-4.3.orig/squashfs-tools/unsquashfs.c
++++ squashfs-tools-4.3/squashfs-tools/unsquashfs.c
+@@ -820,6 +820,8 @@ int set_attributes(char *pathname, int m
+ unsigned int xattr, unsigned int set_mode)
+ {
+ struct utimbuf times = { time, time };
++ /* Mode bits that are only useful with root privileges */
++ mode_t root_mask = S_ISUID | S_ISGID | S_ISVTX;
+
+ if(utime(pathname, ×) == -1) {
+ ERROR("set_attributes: failed to set time on %s, because %s\n",
+@@ -835,9 +837,9 @@ int set_attributes(char *pathname, int m
+ return FALSE;
+ }
+ } else
+- mode &= ~07000;
++ mode &= ~(root_mask);
+
+- if((set_mode || (mode & 07000)) && chmod(pathname, (mode_t) mode) ==
-1) {
++ if((set_mode || (mode & root_mask)) && chmod(pathname, (mode_t) mode)
== -1) {
+ ERROR("set_attributes: failed to change mode %s, because %s\n",
+ pathname, strerror(errno));
+ return FALSE;
diff -Nru
squashfs-tools-4.3/debian/patches/0011-also-set-stickybit-as-non-root.patch
squashfs-tools-4.3/debian/patches/0011-also-set-stickybit-as-non-root.patch
--- squashfs-tools-4.3/debian/patches/0011-also-set-stickybit-as-non-root.patch
1969-12-31 18:00:00.000000000 -0600
+++ squashfs-tools-4.3/debian/patches/0011-also-set-stickybit-as-non-root.patch
2018-07-03 13:27:23.000000000 -0500
@@ -0,0 +1,77 @@
+Subject: [PATCH 0/2] Preserve the sticky bit
+
+The unsquashfs tool was masking off the sticky bit when running as a
+non-root user. It isn't documented why the bit was being masked off but
+there are at least two possibilities.
+
+The first is because all of the files created by unsquashfs, when
+running as a non-root user, will be owned by the same user since
+unsquashfs can't chown() the files.I think it is still good practice to
+attempt to preserve the sticky bit in this situation because it is
+perfectly valid to have a world-writable directory containing files
+owned by a single user. The sticky bit set on the directory inode would
+prevent other users from deleting those files.
+
+Another reason why the sticky bit was being masked off when running as
+non-root could be due to this snippet from the chmod(2) man page:
+
+ On some filesystems, only the superuser can set the sticky bit, which
+ may have a special meaning. For the sticky bit, and for set-user-ID
+ and set-group-ID bits on directories, see stat(2).
+
+However, I'm not seeing any Linux filesystems that require root
+privileges in order to set the sticky bit after a quick search through
+v4.17. In the case that such filesystems do exist, old behavior is
+preserved by retrying a failed chmod() without the sticky bit.
+
+Setting the sticky bit, when non-root, will not cause any problems in
+unsquashfs because all of the created files will by owned by the same
+user. Therefore, unsquashfs will not run into any of the restricted
+deletion protections after setting the sticky bit on a directory inode
+even if unsquashfs needs to remove or rename a file underneath the
+directory.
+
+Signed-off-by: Tyler Hicks <tyhicks@...>
+---
+ squashfs-tools/unsquashfs.c | 17 +++++++++++++----
+ 1 file changed, 13 insertions(+), 4 deletions(-)
+
+Origin: https://sourceforge.net/p/squashfs/mailman/message/36343213/
+Forwarded: yes
+Bug-Ubuntu: https://launchpad.net/bugs/1779914
+
+Index: squashfs-tools-4.3/squashfs-tools/unsquashfs.c
+===================================================================
+--- squashfs-tools-4.3.orig/squashfs-tools/unsquashfs.c
++++ squashfs-tools-4.3/squashfs-tools/unsquashfs.c
+@@ -821,7 +821,7 @@ int set_attributes(char *pathname, int m
+ {
+ struct utimbuf times = { time, time };
+ /* Mode bits that are only useful with root privileges */
+- mode_t root_mask = S_ISUID | S_ISGID | S_ISVTX;
++ mode_t root_mask = S_ISUID | S_ISGID;
+
+ if(utime(pathname, ×) == -1) {
+ ERROR("set_attributes: failed to set time on %s, because %s\n",
+@@ -840,9 +840,18 @@ int set_attributes(char *pathname, int m
+ mode &= ~(root_mask);
+
+ if((set_mode || (mode & root_mask)) && chmod(pathname, (mode_t) mode)
== -1) {
+- ERROR("set_attributes: failed to change mode %s, because %s\n",
+- pathname, strerror(errno));
+- return FALSE;
++ /*
++ * Some filesystems require root privileges to use the sticky
++ * bit. If we're not root and chmod() failed with EPERM when the
++ * sticky bit was included in the mode, try again without the
++ * sticky bit. Otherwise, fail with an error message.
++ */
++ if (root_process || errno != EPERM || !(mode & S_ISVTX) ||
++ chmod(pathname, (mode_t) (mode & ~S_ISVTX)) ==
-1) {
++ ERROR("set_attributes: failed to change mode %s,
because %s\n",
++ pathname, strerror(errno));
++ return FALSE;
++ }
+ }
+
+ write_xattr(pathname, xattr);
diff -Nru squashfs-tools-4.3/debian/patches/series
squashfs-tools-4.3/debian/patches/series
--- squashfs-tools-4.3/debian/patches/series 2018-03-04 13:36:55.000000000
-0600
+++ squashfs-tools-4.3/debian/patches/series 2018-07-03 12:57:10.000000000
-0500
@@ -7,3 +7,5 @@
0007-fix-2GB-limit-in-mksquashfs.patch
0008-preserve_file_capabilities.patch
0009-unsquashfs-preserve-symlink-times.patch
+0010-use-macros-not-raw-octal-with-chmod.patch
+0011-also-set-stickybit-as-non-root.patch
