pax_global_header00006660000000000000000000000064121124340450014506gustar00rootroot0000000000000052 comment=9d4ac4e39c64eaf23f90c28fc97ac426d809c33d linux-user-chroot-2013.1/000077500000000000000000000000001211243404500152035ustar00rootroot00000000000000linux-user-chroot-2013.1/.gitignore000066400000000000000000000005211211243404500171710ustar00rootroot00000000000000# Standard C/Automake goo .deps .libs *.typelib *.la *.lo *.o *.pyc *.stamp *~ Makefile Makefile.in aclocal.m4 autom4te.cache compile config.guess config.h config.h.in config.log config.status config.sub configure depcomp gtk-doc.make INSTALL install-sh libtool ltmain.sh missing stamp-h1 ylwrap py-compile config m4 po ABOUT-NLS _build linux-user-chroot-2013.1/COPYING000066400000000000000000000431101211243404500162350ustar00rootroot00000000000000 GNU GENERAL PUBLIC LICENSE Version 2, June 1991 Copyright (C) 1989, 1991 Free Software Foundation, Inc. 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed. Preamble The licenses for most software are designed to take away your freedom to share and change it. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change free software--to make sure the software is free for all its users. This General Public License applies to most of the Free Software Foundation's software and to any other program whose authors commit to using it. (Some other Free Software Foundation software is covered by the GNU Library General Public License instead.) You can apply it to your programs, too. When we speak of free software, we are referring to freedom, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for this service if you wish), that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs; and that you know you can do these things. To protect your rights, we need to make restrictions that forbid anyone to deny you these rights or to ask you to surrender the rights. These restrictions translate to certain responsibilities for you if you distribute copies of the software, or if you modify it. For example, if you distribute copies of such a program, whether gratis or for a fee, you must give the recipients all the rights that you have. You must make sure that they, too, receive or can get the source code. And you must show them these terms so they know their rights. We protect your rights with two steps: (1) copyright the software, and (2) offer you this license which gives you legal permission to copy, distribute and/or modify the software. Also, for each author's protection and ours, we want to make certain that everyone understands that there is no warranty for this free software. If the software is modified by someone else and passed on, we want its recipients to know that what they have is not the original, so that any problems introduced by others will not reflect on the original authors' reputations. Finally, any free program is threatened constantly by software patents. We wish to avoid the danger that redistributors of a free program will individually obtain patent licenses, in effect making the program proprietary. To prevent this, we have made it clear that any patent must be licensed for everyone's free use or not licensed at all. The precise terms and conditions for copying, distribution and modification follow. GNU GENERAL PUBLIC LICENSE TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION 0. This License applies to any program or other work which contains a notice placed by the copyright holder saying it may be distributed under the terms of this General Public License. The "Program", below, refers to any such program or work, and a "work based on the Program" means either the Program or any derivative work under copyright law: that is to say, a work containing the Program or a portion of it, either verbatim or with modifications and/or translated into another language. (Hereinafter, translation is included without limitation in the term "modification".) Each licensee is addressed as "you". Activities other than copying, distribution and modification are not covered by this License; they are outside its scope. The act of running the Program is not restricted, and the output from the Program is covered only if its contents constitute a work based on the Program (independent of having been made by running the Program). Whether that is true depends on what the Program does. 1. You may copy and distribute verbatim copies of the Program's source code as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice and disclaimer of warranty; keep intact all the notices that refer to this License and to the absence of any warranty; and give any other recipients of the Program a copy of this License along with the Program. You may charge a fee for the physical act of transferring a copy, and you may at your option offer warranty protection in exchange for a fee. 2. You may modify your copy or copies of the Program or any portion of it, thus forming a work based on the Program, and copy and distribute such modifications or work under the terms of Section 1 above, provided that you also meet all of these conditions: a) You must cause the modified files to carry prominent notices stating that you changed the files and the date of any change. b) You must cause any work that you distribute or publish, that in whole or in part contains or is derived from the Program or any part thereof, to be licensed as a whole at no charge to all third parties under the terms of this License. c) If the modified program normally reads commands interactively when run, you must cause it, when started running for such interactive use in the most ordinary way, to print or display an announcement including an appropriate copyright notice and a notice that there is no warranty (or else, saying that you provide a warranty) and that users may redistribute the program under these conditions, and telling the user how to view a copy of this License. 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If the distribution and/or use of the Program is restricted in certain countries either by patents or by copyrighted interfaces, the original copyright holder who places the Program under this License may add an explicit geographical distribution limitation excluding those countries, so that distribution is permitted only in or among countries not thus excluded. In such case, this License incorporates the limitation as if written in the body of this License. 9. The Free Software Foundation may publish revised and/or new versions of the General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. Each version is given a distinguishing version number. If the Program specifies a version number of this License which applies to it and "any later version", you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of this License, you may choose any version ever published by the Free Software Foundation. 10. If you wish to incorporate parts of the Program into other free programs whose distribution conditions are different, write to the author to ask for permission. For software which is copyrighted by the Free Software Foundation, write to the Free Software Foundation; we sometimes make exceptions for this. Our decision will be guided by the two goals of preserving the free status of all derivatives of our free software and of promoting the sharing and reuse of software generally. NO WARRANTY 11. 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IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. END OF TERMS AND CONDITIONS How to Apply These Terms to Your New Programs If you develop a new program, and you want it to be of the greatest possible use to the public, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms. To do so, attach the following notices to the program. It is safest to attach them to the start of each source file to most effectively convey the exclusion of warranty; and each file should have at least the "copyright" line and a pointer to where the full notice is found. Copyright (C) This program 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 2 of the License, or (at your option) any later version. This program 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, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA Also add information on how to contact you by electronic and paper mail. If the program is interactive, make it output a short notice like this when it starts in an interactive mode: Gnomovision version 69, Copyright (C) year name of author Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'. This is free software, and you are welcome to redistribute it under certain conditions; type `show c' for details. The hypothetical commands `show w' and `show c' should show the appropriate parts of the General Public License. Of course, the commands you use may be called something other than `show w' and `show c'; they could even be mouse-clicks or menu items--whatever suits your program. You should also get your employer (if you work as a programmer) or your school, if any, to sign a "copyright disclaimer" for the program, if necessary. Here is a sample; alter the names: Yoyodyne, Inc., hereby disclaims all copyright interest in the program `Gnomovision' (which makes passes at compilers) written by James Hacker. , 1 April 1989 Ty Coon, President of Vice This General Public License does not permit incorporating your program into proprietary programs. If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library. If this is what you want to do, use the GNU Library General Public License instead of this License. linux-user-chroot-2013.1/Makefile-stub.am000066400000000000000000000022151211243404500202120ustar00rootroot00000000000000# Copyright (C) 2011 Colin Walters # # This 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 of the License, or (at your option) any later version. # # This 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 this library; if not, write to the # Free Software Foundation, Inc., 59 Temple Place - Suite 330, # Boston, MA 02111-1307, USA. ACLOCAL_AMFLAGS = -I m4 ${ACLOCAL_FLAGS} AM_CPPFLAGS = -DDATADIR='"$(datadir)"' -DLIBEXECDIR='"$(libexecdir)"' AM_CFLAGS = $(WARN_CFLAGS) NULL = BUILT_SOURCES = MANPAGES = CLEANFILES = EXTRA_DIST = bin_PROGRAMS = sbin_PROGRAMS = bin_SCRIPTS = sbin_SCRIPTS = dist_man_MANS = libexec_PROGRAMS = noinst_LTLIBRARIES = noinst_PROGRAMS = privlibdir = $(pkglibdir) privlib_LTLIBRARIES = linux-user-chroot-2013.1/Makefile-user-chroot.am000066400000000000000000000022201211243404500215030ustar00rootroot00000000000000# Copyright (C) 2011 Colin Walters # # This 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 of the License, or (at your option) any later version. # # This 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 this library; if not, write to the # Free Software Foundation, Inc., 59 Temple Place - Suite 330, # Boston, MA 02111-1307, USA. bin_PROGRAMS += linux-user-chroot linux_user_chroot_SOURCES = src/linux-user-chroot.c linux_user_chroot_CFLAGS = $(AM_CFLAGS) if BUILD_NEWNET_HELPER bin_PROGRAMS += linux-user-chroot-newnet endif linux_user_chroot_newnet_SOURCES = src/linux-user-chroot-newnet.c linux_user_chroot_newnet_CFLAGS = $(AM_CFLAGS) if BUILD_DOCUMENTATION dist_man_MANS += doc/linux-user-chroot.8 endif linux-user-chroot-2013.1/Makefile.am000066400000000000000000000016031211243404500172370ustar00rootroot00000000000000# Copyright (C) 2011 Colin Walters # # This 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 of the License, or (at your option) any later version. # # This 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 this library; if not, write to the # Free Software Foundation, Inc., 59 Temple Place - Suite 330, # Boston, MA 02111-1307, USA. include Makefile-stub.am include Makefile-user-chroot.am release-tag: git tag -m "Release $(VERSION)" v$(VERSION) linux-user-chroot-2013.1/NEWS000066400000000000000000000002751211243404500157060ustar00rootroot000000000000002012.1 ------ This is the first release with a new version numbering scheme of . No important code changes, but we now include a contributed manual page from Lars Wirzenius. linux-user-chroot-2013.1/README000066400000000000000000000065501211243404500160710ustar00rootroot00000000000000Summary ------- This tool allows regular (non-root) users to call chroot(2), create Linux bind mounts, and use some Linux container features. It's primarily intended for use by build systems. Project information ------------------- There's no web page yet; send patches to Colin Walters Why is this useful? ------------------- For build systems, being inside a chroot ensures that the build isn't picking up files it shouldn't be. This helps avoid the problem of "host contamination", where e.g. we want libfoo.h from inside our root, not the one outside the root. Second, it helps avoid the fragility inherent in having to set up a large set of environment variables pointing to our root (e.g. PATH, LD_LIBRARY_PATH, XDG_DATA_DIRS, etc.). Once we chroot, PATH is just the same as it normally is (/bin:/usr/bin). Security -------- **** IMPORTANT NOTE **** Installing this tool accessible to all users significantly increases their ability to perform local, authenticated denial of service attacks. The intended mitigation against this is to ensure the tool is only executable by certain users. **** IMPORTANT NOTE **** The historical reason Unix doesn't allow chroot(2) as non-root is because of setuid binaries. It's trivial to use chroot to create a hostile environment, then execute a setuid binary to subvert it. This tool closes that historical hole by simply disallowing privilege gain by execution of setuid binaries. It creates a "nosuid" bind mount over "/". This restriction is typically irrelevant for build systems. However, this tool also allows creating bind mounts, which currently have no resource controls. This is why this tool is not intended to be installed by default. Abilities granted ----------------- However in order to make a usable system, it's not quite enough to be able to call chroot(2). A lot of Unix software expects e.g. /dev/null, and Linux /proc is also fairly widely used. So this tool also allows creating Linux "bind mounts". This is how one can expose the "host" /dev inside the chroot. Also, this tool allows mounting procfs. In addition, this tool exposes several of the Linux "unshare" capabilities such as: * CLONE_NEWNET - create a new, empty networking stack. Because the child process won't have the privilges to manipulate the network, this will result in no networking (including loopback) which ensures that e.g. the build process isn't downloading more code. * CLONE_NEWPID - create a new PID namespace. For example, if the build script runs some test scripts that start processes, "pidof" won't accidentally pick up a similarly-named process outside of the root. * CLONE_NEWIPC - get a new SysV IPC namespace. This is just further isolation. See "man 2 clone" for more information. Example usage ------------- Note here all files are owned by the user. $ mkdir -p /path/to/my/chroot/usr/src/project $ linux-user-chroot --unshare-pid --unshare-net --unshare-pid \ --mount-proc /proc --mount-bind /dev /dev \ --mount-bind /home/user/source/project /usr/src/project \ /path/to/my/chroot /bin/sh Here we're creating a bind mount inside the chroot to outside. This helps avoid copying files around. Installing ---------- This binary can be installed in two modes: 1) uwsr-xr-x root:root - Executable by everyone 2) uwsr-x--- root:somegroup - Executable only by somegroup linux-user-chroot-2013.1/README.newnet000066400000000000000000000025611211243404500173660ustar00rootroot00000000000000newnet helper ------------- This is an optional helper program that simply allows calling CLONE_NEWNET and executing a child process. The reason this program exists as an option is because on some Linux kernel configurations (e.g. with the netfilter kernel module loaded), it's expensive to create new network namespaces, and it may actually fail. linux-user-chroot is intended to create namespaces quite dynamically, but this conflicts somewhat with the goals of the developers who contributed the functionality for typically more static "containers". If you don't need this helper as a workaround, don't build it. Caveat ------ This helper program does NOT restrict further execution of setuid binaries. Otherwise, you couldn't run linux-user-chroot inside of it, and that would defeat the point. However I don't believe the attack surface exposed by making an empty network namespace is very high - it does mean that e.g. one could make "sudo" fail to look up the username if it's configured to use LDAP. But most setuid programs *should* be carefully checking errors anyways. Building -------- To enable building this helper, pass --enable-newnet-helper to configure. Running ------- $ linux-user-chroot-newnet curl http://google.com curl: (6) Could not resolve host: google.com; Unknown error $ linux-user-chroot-newnet /bin/bash $ # you're now in a shell without networking linux-user-chroot-2013.1/autogen.sh000077500000000000000000000005441211243404500172070ustar00rootroot00000000000000#!/bin/sh test -n "$srcdir" || srcdir=`dirname "$0"` test -n "$srcdir" || srcdir=. olddir=`pwd` cd $srcdir if ! (autoreconf --version >/dev/null 2>&1); then echo "*** No autoreconf found, please install it ***" exit 1 fi mkdir -p m4 autoreconf --force --install --verbose cd $olddir test -n "$NOCONFIGURE" || "$srcdir/configure" "$@" linux-user-chroot-2013.1/configure.ac000066400000000000000000000023561211243404500174770ustar00rootroot00000000000000AC_PREREQ([2.63]) AC_INIT([linux-user-chroot], [2013.1], [walters@verbum.org]) AC_CONFIG_HEADER([config.h]) AC_CONFIG_MACRO_DIR([m4]) AC_CONFIG_AUX_DIR([build-aux]) AM_INIT_AUTOMAKE([1.11 -Wno-portability foreign no-define tar-ustar no-dist-gzip dist-xz]) AM_MAINTAINER_MODE([enable]) AM_SILENT_RULES([yes]) AC_SYS_LARGEFILE AC_PROG_CC AM_PROG_CC_C_O changequote(,)dnl if test "x$GCC" = "xyes"; then WARN_CFLAGS="-Wall -Werror=missing-prototypes" fi changequote([,])dnl AC_SUBST(WARN_CFLAGS) # Initialize libtool LT_PREREQ([2.2.4]) LT_INIT([disable-static]) AC_CHECK_HEADER([linux/securebits.h], [AC_DEFINE([HAVE_LINUX_SECUREBITS_H], [1], [Define to 1 if we have securebits.h])]) AC_ARG_ENABLE(documentation, AC_HELP_STRING([--enable-documentation], [build documentation]),, enable_documentation=yes) AM_CONDITIONAL(BUILD_DOCUMENTATION, test x$enable_documentation = xyes) AC_ARG_ENABLE(newnet-helper, AC_HELP_STRING([--enable-newnet-helper], [build newnet helper (see README.newnet)]),, enable_newnet_helper=no) AM_CONDITIONAL(BUILD_NEWNET_HELPER, test x$enable_newnet_helper = xyes) AC_CONFIG_FILES([ Makefile ]) AC_OUTPUT linux-user-chroot-2013.1/doc/000077500000000000000000000000001211243404500157505ustar00rootroot00000000000000linux-user-chroot-2013.1/doc/linux-user-chroot.8000066400000000000000000000064531211243404500214600ustar00rootroot00000000000000.\" Copyright 2012 Codethink Limited .\" .\" This program 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 2 of the License, or .\" (at your option) any later version. .\" .\" This program is distributed in the hope that it would 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, write to the Free Software Foundation, .\" Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA .\" .TH LINUX-USER-CHROOT 8 .SH NAME linux\-user\-chroot \- safely allow normal users to chroot .SH SYNOPSIS .B linux\-user\-chroot .RB [ --unshare-ipc ] .RB [ --unshare-pid ] .RB [ --unshare-net ] .RB [ --mount-proc " \fIDIR\fR] .RB [ --mount-readonly " \fIDIR\fR"] .RB [ --mount-bind " \fISOURCE DEST\fR"] .RB [ --chdir " \fIDIR\fR"] .I ROOTDIR .I PROGRAM .IR ARGS... .SH DESCRIPTION .B linux\-user\-chroot is a tool meant for building software in a clean environment. The user needs to create a directory tree with the build dependencies needed, and only those, and then .B linux\-user\-chroot runs the actual build commands such that the commands only see the directory tree. This is useful for ensuring the build gets the right version of its build dependencies, for example. .PP .B linux\-user\-chroot works similary to .BR chroot (8), but does not require the caller to have root privileges. It uses Linux containers to restrict the chroot to make this safe. The command run inside the chroot is run as the calling user, not as root. .PP .B linux\-user\-chroot executes a command, and sets the root directory for the command to the directory specified by the user .RI ( ROOTDIR ). Additionally, it creates a "nosuid" bind mount over the root filesystem, to prevent the build from gaining privileges using setuid binaries. The command can further be restricted from accessing the network, and it can be set up with new process ID and SysV IPC namespaces. .SH OPTIONS .TP .BR \-\-unshare\-ipc Create a new SysV IPC namespace for the command. .TP .BR \-\-unshare\-pid Create a new process ID (PID) namespace for the command. This prevents the command from seeing any other processes in the system, except itself and the processes it itself creates. .TP .BR \-\-unshare\-net Create a new, empty networking stack. This prevents the command from using any networking, including loopback. .TP .BI \-\-mount\-proc " DIR" Mount the proc filesystem at .IR DIR . .TP .BI \-\-mount\-readonly " DIR" Make .I DIR be read-only for the command. .TP .BI \-\-mount\-bind " SOURCE DEST" Add a bind mount while the command is executing. .TP .BI \-\-chdir " DIR" After setting the new root directory for the command, change the current working directory to be .IR DIR . .SH "EXIT STATUS" The exit status is the exit status of the executed command, or 1 if .B linux\-user\-chroot failed to execute the command. .SH EXAMPLE To build software in the real system, but without networking: .IP .nf linux\-user\-chroot \-\-unshare\-net \-\-chdir "$(pwd)" make clean all check .fi .SH "SEE ALSO" .BR chroot (8). linux-user-chroot-2013.1/linux-user-chroot.doap000066400000000000000000000015361211243404500214640ustar00rootroot00000000000000 linux-user-chroot setuid helper for making bind mounts and chrooting C Colin Walters walters linux-user-chroot-2013.1/src/000077500000000000000000000000001211243404500157725ustar00rootroot00000000000000linux-user-chroot-2013.1/src/linux-user-chroot-newnet.c000066400000000000000000000063051211243404500230470ustar00rootroot00000000000000/* -*- mode: c; tab-width: 2; indent-tabs-mode: nil -*- * * newnet-suid: Allow allocating a new empty network namespace as * non-root. This program is just a workaround for the kernel * requiring large-order allocations (e.g. 4 pages) per network * namespace. * * Copyright 2012 Colin Walters * * This program 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 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it would 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, write to the Free Software Foundation, * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ #define _GNU_SOURCE #include #include #include #include #include #include #include #include #include #include #include #include #include static void fatal (const char *message, ...) __attribute__ ((noreturn)) __attribute__ ((format (printf, 1, 2))); static void fatal_errno (const char *message) __attribute__ ((noreturn)); static void fatal (const char *fmt, ...) { va_list args; va_start (args, fmt); vfprintf (stderr, fmt, args); putc ('\n', stderr); va_end (args); exit (1); } static void fatal_errno (const char *message) { perror (message); exit (1); } int main (int argc, char **argv) { const char *program; uid_t ruid, euid, suid; gid_t rgid, egid, sgid; char **program_argv; int child_status = 0; pid_t child; if (argc <= 0) return 1; argc--; argv++; if (argc < 1) fatal ("PROGRAM [ARGS]... Run PROGRAM in an isolated network namespace"); program = argv[0]; program_argv = argv; if (getresgid (&rgid, &egid, &sgid) < 0) fatal_errno ("getresgid"); if (getresuid (&ruid, &euid, &suid) < 0) fatal_errno ("getresuid"); if (rgid == 0) rgid = ruid; if ((child = syscall (__NR_clone, SIGCHLD | CLONE_NEWNET, NULL)) < 0) perror ("clone"); if (child == 0) { /* Switch back to the uid of our invoking process. These calls are * irrevocable - see setuid(2) */ if (setgid (rgid) < 0) fatal_errno ("setgid"); if (setuid (ruid) < 0) fatal_errno ("setuid"); if (execvp (program, program_argv) < 0) fatal_errno ("execv"); } /* Let's also setuid back in the parent - there's no reason to stay uid 0, and * it's just better to drop privileges. */ if (setgid (rgid) < 0) fatal_errno ("setgid"); if (setuid (ruid) < 0) fatal_errno ("setuid"); /* Kind of lame to sit around blocked in waitpid, but oh well. */ if (waitpid (child, &child_status, 0) < 0) fatal_errno ("waitpid"); if (WIFEXITED (child_status)) return WEXITSTATUS (child_status); else return 1; } linux-user-chroot-2013.1/src/linux-user-chroot.c000066400000000000000000000300711211243404500215460ustar00rootroot00000000000000/* -*- mode: c; tab-width: 2; indent-tabs-mode: nil -*- * * linux-user-chroot: A setuid program that allows non-root users to safely chroot(2) * * "safely": I believe that this program, when deployed as setuid on a * typical "distribution" such as RHEL or Debian, does not, even when * used in combination with typical software installed on that * distribution, allow privilege escalation. See the README for more * details. * * Copyright 2011,2012 Colin Walters * * This program 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 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it would 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, write to the Free Software Foundation, * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ #include "config.h" #define _GNU_SOURCE #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #ifdef HAVE_LINUX_SECUREBITS_H #include #else #define SECBIT_NOROOT (1 << 0) #define SECBIT_NOROOT_LOCKED (1 << 1) #endif #ifndef PR_SET_NO_NEW_PRIVS #define PR_SET_NO_NEW_PRIVS 38 #endif static void fatal (const char *message, ...) __attribute__ ((noreturn)) __attribute__ ((format (printf, 1, 2))); static void fatal_errno (const char *message) __attribute__ ((noreturn)); static void fatal (const char *fmt, ...) { va_list args; va_start (args, fmt); vfprintf (stderr, fmt, args); putc ('\n', stderr); va_end (args); exit (1); } static void fatal_errno (const char *message) { perror (message); exit (1); } typedef enum { MOUNT_SPEC_BIND, MOUNT_SPEC_READONLY, MOUNT_SPEC_PROCFS } MountSpecType; typedef struct _MountSpec MountSpec; struct _MountSpec { MountSpecType type; const char *source; const char *dest; MountSpec *next; }; static MountSpec * reverse_mount_list (MountSpec *mount) { MountSpec *prev = NULL; while (mount) { MountSpec *next = mount->next; mount->next = prev; prev = mount; mount = next; } return prev; } /** * fsuid_chdir: * @uid: User id we should use * @path: Path string * * Like chdir() except we use the filesystem privileges of @uid. */ static int fsuid_chdir (uid_t uid, const char *path) { int errsv; int ret; /* Note we don't check errors here because we can't, basically */ (void) setfsuid (uid); ret = chdir (path); errsv = errno; (void) setfsuid (0); errno = errsv; return ret; } int main (int argc, char **argv) { const char *argv0; const char *chroot_dir; const char *chdir_target = "/"; const char *program; uid_t ruid, euid, suid; gid_t rgid, egid, sgid; int after_mount_arg_index; unsigned int n_mounts = 0; const unsigned int max_mounts = 50; /* Totally arbitrary... */ char **program_argv; MountSpec *bind_mounts = NULL; MountSpec *bind_mount_iter; int unshare_ipc = 0; int unshare_net = 0; int unshare_pid = 0; int clone_flags = 0; int child_status = 0; pid_t child; if (argc <= 0) return 1; argv0 = argv[0]; argc--; argv++; if (argc < 1) fatal ("ROOTDIR argument must be specified"); after_mount_arg_index = 0; while (after_mount_arg_index < argc) { const char *arg = argv[after_mount_arg_index]; MountSpec *mount = NULL; if (n_mounts >= max_mounts) fatal ("Too many mounts (maximum of %u)", n_mounts); n_mounts++; if (strcmp (arg, "--help") == 0) { printf ("%s\n", "See \"man linux-user-chroot\""); exit (0); } else if (strcmp (arg, "--version") == 0) { printf ("%s\n", PACKAGE_STRING); exit (0); } else if (strcmp (arg, "--mount-bind") == 0) { if ((argc - after_mount_arg_index) < 3) fatal ("--mount-bind takes two arguments"); mount = malloc (sizeof (MountSpec)); mount->type = MOUNT_SPEC_BIND; mount->source = argv[after_mount_arg_index+1]; mount->dest = argv[after_mount_arg_index+2]; mount->next = bind_mounts; bind_mounts = mount; after_mount_arg_index += 3; } else if (strcmp (arg, "--mount-readonly") == 0) { MountSpec *mount; if ((argc - after_mount_arg_index) < 2) fatal ("--mount-readonly takes one argument"); mount = malloc (sizeof (MountSpec)); mount->type = MOUNT_SPEC_READONLY; mount->source = NULL; mount->dest = argv[after_mount_arg_index+1]; mount->next = bind_mounts; bind_mounts = mount; after_mount_arg_index += 2; } else if (strcmp (arg, "--mount-proc") == 0) { MountSpec *mount; if ((argc - after_mount_arg_index) < 2) fatal ("--mount-proc takes one argument"); mount = malloc (sizeof (MountSpec)); mount->type = MOUNT_SPEC_PROCFS; mount->source = NULL; mount->dest = argv[after_mount_arg_index+1]; mount->next = bind_mounts; bind_mounts = mount; after_mount_arg_index += 2; } else if (strcmp (arg, "--unshare-ipc") == 0) { unshare_ipc = 1; after_mount_arg_index += 1; } else if (strcmp (arg, "--unshare-pid") == 0) { unshare_pid = 1; after_mount_arg_index += 1; } else if (strcmp (arg, "--unshare-net") == 0) { unshare_net = 1; after_mount_arg_index += 1; } else if (strcmp (arg, "--chdir") == 0) { if ((argc - after_mount_arg_index) < 2) fatal ("--chdir takes one argument"); chdir_target = argv[after_mount_arg_index+1]; after_mount_arg_index += 2; } else break; } bind_mounts = reverse_mount_list (bind_mounts); if ((argc - after_mount_arg_index) < 2) fatal ("usage: %s [--unshare-ipc] [--unshare-pid] [--unshare-net] [--mount-proc DIR] [--mount-readonly DIR] [--mount-bind SOURCE DEST] [--chdir DIR] ROOTDIR PROGRAM ARGS...", argv0); chroot_dir = argv[after_mount_arg_index]; program = argv[after_mount_arg_index+1]; program_argv = argv + after_mount_arg_index + 1; if (getresgid (&rgid, &egid, &sgid) < 0) fatal_errno ("getresgid"); if (getresuid (&ruid, &euid, &suid) < 0) fatal_errno ("getresuid"); if (rgid == 0) rgid = ruid; /* CLONE_NEWNS makes it so that when we create bind mounts below, * we're only affecting our children, not the entire system. This * way it's harmless to bind mount e.g. /proc over an arbitrary * directory. */ clone_flags = SIGCHLD | CLONE_NEWNS; /* CLONE_NEWIPC and CLONE_NEWUTS are avenues of communication that * might leak outside the container; any IPC can be done by setting * up a bind mount and using files or sockets there, if desired. */ if (unshare_ipc) clone_flags |= (CLONE_NEWIPC | CLONE_NEWUTS); /* CLONE_NEWPID helps ensure random build or test scripts don't kill * processes outside of the container. */ if (unshare_pid) clone_flags |= CLONE_NEWPID; /* Isolated networking */ if (unshare_net) clone_flags |= CLONE_NEWNET; if ((child = syscall (__NR_clone, clone_flags, NULL)) < 0) fatal_errno ("clone"); if (child == 0) { /* * First, we attempt to use PR_SET_NO_NEW_PRIVS, since it does * exactly what we want - ensures the child can not gain any * privileges, even attempting to execute setuid binaries. * * http://lwn.net/Articles/504879/ * * If that's not available, we fall back to using SECBIT_NOROOT. * * Following the belt-and-suspenders model, we also make a * MS_NOSUID bind mount below. */ if (prctl (PR_SET_NO_NEW_PRIVS, 1) < 0 && errno != EINVAL) fatal_errno ("prctl (PR_SET_NO_NEW_PRIVS)"); else if (prctl (PR_SET_SECUREBITS, SECBIT_NOROOT | SECBIT_NOROOT_LOCKED) < 0) fatal_errno ("prctl (SECBIT_NOROOT)"); /* This is necessary to undo the damage "sandbox" creates on Fedora * by making / a shared mount instead of private. This isn't * totally correct because the targets for our bind mounts may still * be shared, but really, Fedora's sandbox is broken. */ if (mount (NULL, "/", "none", MS_PRIVATE | MS_REC, NULL) < 0) fatal_errno ("mount(/, MS_PRIVATE | MS_REC)"); /* I had thought that SECBIT_NOROOT was enough to be safe, but Serge E. Hallyn * pointed out that setuid binaries still change uid to 0. So let's just * disallow them at the rootfs level. */ if (mount (NULL, "/", "none", MS_PRIVATE | MS_REMOUNT | MS_NOSUID, NULL) < 0) fatal_errno ("mount(/, MS_PRIVATE | MS_REC | MS_NOSUID)"); /* Now let's set up our bind mounts */ for (bind_mount_iter = bind_mounts; bind_mount_iter; bind_mount_iter = bind_mount_iter->next) { char *dest; asprintf (&dest, "%s%s", chroot_dir, bind_mount_iter->dest); if (bind_mount_iter->type == MOUNT_SPEC_READONLY) { if (mount (dest, dest, NULL, MS_BIND | MS_PRIVATE, NULL) < 0) fatal_errno ("mount (MS_BIND)"); if (mount (dest, dest, NULL, MS_BIND | MS_PRIVATE | MS_REMOUNT | MS_RDONLY, NULL) < 0) fatal_errno ("mount (MS_BIND | MS_RDONLY)"); } else if (bind_mount_iter->type == MOUNT_SPEC_BIND) { if (fsuid_chdir (ruid, bind_mount_iter->source) < 0) fatal ("Couldn't chdir to bind mount source"); if (mount (".", dest, NULL, MS_BIND | MS_PRIVATE, NULL) < 0) fatal_errno ("mount (MS_BIND)"); } else if (bind_mount_iter->type == MOUNT_SPEC_PROCFS) { if (mount ("proc", dest, "proc", MS_MGC_VAL | MS_PRIVATE, NULL) < 0) fatal_errno ("mount (\"proc\")"); } else assert (0); free (dest); } if (fsuid_chdir (ruid, chroot_dir) < 0) fatal_errno ("chdir"); if (mount (".", ".", NULL, MS_BIND | MS_PRIVATE, NULL) < 0) fatal_errno ("mount (MS_BIND)"); /* Only move if we're not actually just using / */ if (strcmp (chroot_dir, "/") != 0) { if (mount (chroot_dir, "/", NULL, MS_MOVE, NULL) < 0) fatal_errno ("mount (MS_MOVE)"); if (chroot (".") < 0) fatal_errno ("chroot"); } /* Switch back to the uid of our invoking process. These calls are * irrevocable - see setuid(2) */ if (setgid (rgid) < 0) fatal_errno ("setgid"); if (setuid (ruid) < 0) fatal_errno ("setuid"); if (chdir (chdir_target) < 0) fatal_errno ("chdir"); if (execvp (program, program_argv) < 0) fatal_errno ("execv"); } /* Let's also setuid back in the parent - there's no reason to stay uid 0, and * it's just better to drop privileges. */ if (setgid (rgid) < 0) fatal_errno ("setgid"); if (setuid (ruid) < 0) fatal_errno ("setuid"); /* Kind of lame to sit around blocked in waitpid, but oh well. */ if (waitpid (child, &child_status, 0) < 0) fatal_errno ("waitpid"); if (WIFEXITED (child_status)) return WEXITSTATUS (child_status); else return 1; }