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| author | Carlos O'Donell <carlos@redhat.com> | 2013-07-19 02:42:03 -0400 |
|---|---|---|
| committer | Carlos O'Donell <carlos@redhat.com> | 2013-07-21 15:39:55 -0400 |
| commit | e4608715e6e1dd2adc91982fd151d5ba4f761d69 (patch) | |
| tree | 04bc13d3736e14045f0f9fc37e0303a067f943cf /manual/install.texi | |
| parent | da2d62df77de66e5de5755228759f8bc18481871 (diff) | |
CVE-2013-2207, BZ #15755: Disable pt_chown.
The helper binary pt_chown tricked into granting access to another
user's pseudo-terminal.
Pre-conditions for the attack:
* Attacker with local user account
* Kernel with FUSE support
* "user_allow_other" in /etc/fuse.conf
* Victim with allocated slave in /dev/pts
Using the setuid installed pt_chown and a weak check on whether a file
descriptor is a tty, an attacker could fake a pty check using FUSE and
trick pt_chown to grant ownership of a pty descriptor that the current
user does not own. It cannot access /dev/pts/ptmx however.
In most modern distributions pt_chown is not needed because devpts
is enabled by default. The fix for this CVE is to disable building
and using pt_chown by default. We still provide a configure option
to enable hte use of pt_chown but distributions do so at their own
risk.
Diffstat (limited to 'manual/install.texi')
| -rw-r--r-- | manual/install.texi | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/manual/install.texi b/manual/install.texi index 0c05f51bbb..4575d22319 100644 --- a/manual/install.texi +++ b/manual/install.texi @@ -163,6 +163,20 @@ so that they can be invoked directly. @item --enable-lock-elision=yes Enable lock elision for pthread mutexes by default. +@pindex pt_chown +@findex grantpt +@item --enable-pt_chown +The file @file{pt_chown} is a helper binary for @code{grantpt} +(@pxref{Allocation, Pseudo-Terminals}) that is installed setuid root to +fix up pseudo-terminal ownership. It is not built by default because +systems using the Linux kernel are commonly built with the @code{devpts} +filesystem enabled and mounted at @file{/dev/pts}, which manages +pseudo-terminal ownership automatically. By using +@samp{--enable-pt_chown}, you may build @file{pt_chown} and install it +setuid and owned by @code{root}. The use of @file{pt_chown} introduces +additional security risks to the system and you should enable it only if +you understand and accept those risks. + @item --build=@var{build-system} @itemx --host=@var{host-system} These options are for cross-compiling. If you specify both options and |