[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <CANDc0NLKmtDS=TabWyrPrHwUe=WGP34DnwD6YN0SpA1ghQjyKQ@mail.gmail.com>
Date: Wed, 13 Mar 2013 08:44:47 +0000
From: Eduardo Tongson <propolice@...il.com>
To: oss-security@...ts.openwall.com
Subject: Re: Linux kernel + devtmpfs automount == insecure
/dev/{,u}random mode
On Wed, Mar 13, 2013 at 8:35 AM, <gremlin@...mlin.ru> wrote:
> linux/drivers/char/mem.c contains the following code:
>
> static const struct memdev {
> const char *name;
> umode_t mode;
> const struct file_operations *fops;
> struct backing_dev_info *dev_info;
> } devlist[] = {
> // ...
> [8] = { "random", 0666, &random_fops, NULL },
> [9] = { "urandom", 0666, &urandom_fops, NULL },
> // ...
> };
>
> This allows writing to these devices by an unprivileged user
> resulting in re-initializing the entropy pool (as described
> in `man 4 random`) and thus making the data predictable.
>
> Just boot the kernel with "init=/bin/sh" parameter and issue
> the `ls -l /dev/*random` command - you'll see something like:
>
> crw-rw-rw- 1 root root 1, 8 Mar 13 08:30 /dev/random
> crw-rw-rw- 1 root root 1, 9 Mar 13 08:30 /dev/urandom
>
> The obvious fix is to create these devices with mode 0644,
> so only root will be able to re-initialize the entropy pool.
>
> Possibly, this even deserves a CVE to be assigned...
>
>
> --
> Alexey V. Vissarionov aka Gremlin from Kremlin <gremlin ПРИ gremlin ТЧК ru>
> GPG key ID: 0xEF3B1FA8, keyserver: hkp://subkeys.pgp.net
> GPG key fingerprint: 8832 FE9F A791 F796 8AC9 6E4E 909D AC45 EF3B 1FA8
See http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=81748.
E
Powered by blists - more mailing lists
Please check out the
Open Source Software Security Wiki, which is counterpart to this
mailing list.
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
