Best practices for sugroups for root ? backdoor user access ? Post: 303020452

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Operating Systems AIX Best practices for sugroups for root ? backdoor user access ? Post 303020452 by maraixadm on Thursday 19th of July 2018 06:01:40 PM

07-19-2018

Registered User

Best practices for sugroups for root ? backdoor user access ?

greetings, just ran across a fun situation we had overlooked.

We have a backdoor user, no special privileges, which we put on every server so that anyone in the shop can get in (passwd in vault) if they need to, even if they don't have a local account on that server. The point of course is to be able to administer when there's a problem and the primary owners aren't available, etc. So su or sudo is a requirement.

The culture here places a high value on audit, the backdoor user is anonymous, and so it doesn't get to be in /etc/sudoers by policy. So it must be able to use 'su' (and thus require the local root pw which is also in the password vault).

We just found that on some servers, sugroups=system for root, the backdoor user is not in system group, so it can't su. Thus disabling its reason for existence.

The backdoor user should of course not be in system group; a cursory glance at /usr/sbin shows the variety of commands that are restricted to system, etc. etc.

Anyone want to suggest a good solution for this thought exercise ?

Simplistically, if sugroups=system is desirable for root (where in this shop userIDs corresponding to real humans may be put in system group to allow them to e.g. do NFS mounts on the fly) then one could add a second group with the singular purpose of authorizing access to su to root, and put the backdoor user in it, and put it in sugroups for root, i.e. sugroups=system,rootsu .

Has someone encountered this before and solved it to your satisfaction, or want to try their hand at the security math here to determine how elaborate the solution has to be ?

If best practices here are well-known, pardon my ignorance, pls share.

TIA !

Here's an IBM DevWorks discussion, it addresses some of the above, quite well: Controlling su access with sugroups

Last edited by maraixadm; 07-19-2018 at 07:07 PM..

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ftpusers

ftpusers(4)							   File Formats 						       ftpusers(4)

NAME

       ftpusers - file listing users to be disallowed ftp login privileges

SYNOPSIS

       /etc/ftpd/ftpusers

DESCRIPTION

       The ftpusers file lists users for whom ftp login privileges are disallowed. Each ftpuser entry is a single line of the form:

	 name

       where name is the user's login name.

       The FTP Server, in.ftpd(1M), reads the ftpusers file. If the login name of the user matches one of the entries listed, it rejects the login
       attempt.

       The ftpusers file has the following default configuration entries:

	 root
	 daemon
	 bin
	 sys
	 adm
	 lp
	 uccp
	 nuucp
	 smmsp
	 listen
	 nobody
	 noaccess
	 nobody4

       These entries match the default instantiated entries from passwd(4). The list of default entries typically contains the superuser root  and
       other administrative and system application identities.

       The  root entry is included in the ftpusers file as a security measure since the default policy is to disallow remote logins for this iden-
       tity. This policy is also set in the default value of the CONSOLE entry in the /etc/default/login file. See login(1).  If  you  allow  root
       login  privileges  by  deleting the root entry in ftpusers, you should also modify the security policy in /etc/default/login to reflect the
       site security policy for remote login access by root.

       Other default entries are administrative identities that are typically assumed by system applications but never used for  local	or  remote
       login,  for  example sys and nobody. Since these entries do not have a valid password field instantiated in shadow(4), no login can be per-
       formed.

       If a site adds similar administrative or system application identities in passwd(4) and shadow(4), for example, majordomo, the site  should
       consider including them in the ftpusers file for a consistent security policy.

       Lines that begin with # are treated as comment lines and are ignored.

FILES

       /etc/ftpd/ftpusers    A file that lists users for whom ftp login privileges are disallowed.

       /etc/ftpusers	     See /etc/ftpd/ftpusers. This file is deprecated, although its use is still supported.

       /etc/default/login

       /etc/passwd	     password file

       /etc/shadow	     shadow password file

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWftpr			   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |See below.		   |
       +-----------------------------+-----------------------------+

       The interface stability for /etc/ftpd/ftpusers is Volatile. The interface stability for /etc/ftpusers is (Obsolete).

SEE ALSO

       login(1), in.ftpd(1M), ftpaccess(4), ftphosts(4), passwd(4), shadow(4), attributes(5), environ(5)

SunOS 5.11							    1 May 2003							       ftpusers(4)