[Snort-devel] Problems with umask on Snort 3

Carter Waxman (cwaxman) cwaxman at cisco.com
Fri Jan 4 13:18:54 EST 2019


Snort default if not explicitly set:

        umask(077);    /* set default to be sane */

Adding -m0x1f (000 011 111) on top of user / group settings will give you a max of rwx-r---- instead of the default rwx------

From: Noah Dietrich <noah_dietrich at 86penny.org>
Date: Friday, January 4, 2019 at 1:09 PM
To: "Carter Waxman (cwaxman)" <cwaxman at cisco.com>
Cc: "snort-devel at lists.snort.org" <snort-devel at lists.snort.org>
Subject: Re: [Snort-devel] Problems with umask on Snort 3

I'm still getting this problem when i run snort with the 'snort' user and group.  I can't seem to get snort3 to output log files with any permissions beyond rw for the owner.  I've tried creating new log directories, verified the default umask on the system, and i can't seem to get snort to grant read rights to the group or other sets.  Snort doesn't seem to follow the system mask when creating files.

for example, when i (as a regular user) go to create a file:
noah at snort3:~$ touch abc
noah at snort3:~$ ls -l
-rw-rw-r--  1 noah noah     0 Jan  4 12:37 abc

Verify my umask:
noah at snort3:~$ umask
0002

if then (as a regular user) i try to run snort and create logs:
snort -c /usr/local/etc/snort/snort.lua -r ~/pcaps/maccdc2012_00000.pcap -l /home/noah/snort-logs/
i can then check the permissions on those log files:
noah at snort3:~$ ls -l snort-logs/
-rw------- 1 noah noah 1045217 Jan  4 12:56 alert_csv.txt.1546624609

you can see that snort creates files with 600 for the file permissions, when the system default is 644.  I can't get snort in any way (root, different user account, working with the -m option) to create files with 644 mode.

if i run snort with the snort user and group:
sudo mkdir /var/log/snort
sudo chown snort:snort /var/log/snort
sudo snort -c /usr/local/etc/snort/snort.lua -r ~/pcaps/maccdc2012_00000.pcap -l /var/log/snort -u snort -g snort

then check the output, You can see snort switching user and group id's:
Commencing packet processing
++ [0] /home/noah/pcaps/maccdc2012_00000.pcap
Set GID to 1002
Set UID to 999

and in the output file, the user and group are correct (snort:snort), but the permissions are again 600, not 644 as you'd expect
noah at snort3:~$ ls -l /var/log/snort
-rw------- 1 snort snort 514546 Jan  4 13:06 alert_csv.txt.1546625184

 Is this a bug with snort, or am i doing something wrong?

thanks for your help.



On Fri, Jan 4, 2019 at 5:39 PM Carter Waxman (cwaxman) <cwaxman at cisco.com<mailto:cwaxman at cisco.com>> wrote:
*lowercase u and g

From: Snort-devel <snort-devel-bounces at lists.snort.org<mailto:snort-devel-bounces at lists.snort.org>> on behalf of "Carter Waxman (cwaxman) via Snort-devel" <snort-devel at lists.snort.org<mailto:snort-devel at lists.snort.org>>
Reply-To: "Carter Waxman (cwaxman)" <cwaxman at cisco.com<mailto:cwaxman at cisco.com>>
Date: Friday, January 4, 2019 at 11:38 AM
To: Noah Dietrich <noah_dietrich at 86penny.org<mailto:noah_dietrich at 86penny.org>>, "snort-devel at lists.snort.org<mailto:snort-devel at lists.snort.org>" <snort-devel at lists.snort.org<mailto:snort-devel at lists.snort.org>>
Subject: Re: [Snort-devel] Problems with umask on Snort 3

Setting umask places limits on newly created files, it doesn’t set the actual permissions. Also, the permissions in umask are inverted, so umask of 0x01FF will actually not allow any permission bits to be set. It sounds like what you actually want is to create a user for your Snort process (for writing, leaving it root isn’t a good idea…), a group for Snort readers, and set the process user / group with -U / -G.

-Carter

From: Snort-devel <snort-devel-bounces at lists.snort.org<mailto:snort-devel-bounces at lists.snort.org>> on behalf of Noah Dietrich <noah_dietrich at 86penny.org<mailto:noah_dietrich at 86penny.org>>
Date: Thursday, January 3, 2019 at 1:09 PM
To: "snort-devel at lists.snort.org<mailto:snort-devel at lists.snort.org>" <snort-devel at lists.snort.org<mailto:snort-devel at lists.snort.org>>
Subject: [Snort-devel] Problems with umask on Snort 3

Hello,

I am trying to get the umask option (-m) working with snort 3, and i'm not sure what is going wrong.  I'm trying to have Snort generate logs that users and other can read (644), but when I use the -m option with snort, I don't get the results i expect.  I can only seem to affect the read and write owner portion of the permissions. For example:

-m 0x000   leads to -rw-------
-m 0x01FF leads to ----------
-m 0x00FF leads to -r--------

without using the -m flag, the default permissions are -rw-------

The command i'm running is
sudo snort -c /usr/local/etc/snort/snort.lua -r ~/pcaps/maccdc2012_00000.pcap -l /var/log/test -s 65535 -k none -q -m 0x00FF

Version of snort:
noah at snort3:~$ snort -V
   ,,_     -*> Snort++ <*-
  o"  )~   Version 3.0.0 (Build 250) from 2.9.11
   ''''    By Martin Roesch & The Snort Team
           http://snort.org/contact#team
           Copyright (C) 2014-2018 Cisco and/or its affiliates. All rights reserved.
           Copyright (C) 1998-2013 Sourcefire, Inc., et al.
           Using DAQ version 2.2.2
           Using LuaJIT version 2.1.0-beta3
           Using OpenSSL 1.1.0g  2 Nov 2017
           Using libpcap version 1.8.1
           Using PCRE version 8.39 2016-06-14
           Using ZLIB version 1.2.11
           Using FlatBuffers 1.10.0
           Using Hyperscan version 5.0.0 2018-12-08
           Using LZMA version 5.2.2


I'm not sure if i'm doing something wrong, or if this is a bug.

thanks
Noah


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