News for hackers. Stuff that matters.

A comment on Systemd can't handle the process privilege for username startswith number. Parent comment

Re:Systemd can't handle the process privilege for username s... by viraptor on Sunday July 02, 2017 @05:35AM (#14681701)
Strict validation. If some option is not valid, fail loudly. And he still fails to acknowledge this is a security issue. Here's a scenario for you:

You're running a SaaS which spawns restricted demons/containers per customer, separating the users by assigning them local user accounts. One day, user "0zero" registers and their account has access to your whole environment. Would you expect this? Would you not classify this as a security issue?

[ Parent | on HN ]
Re:Systemd can't handle the process privilege for username s... by JdeBP on Sunday July 02, 2017 @06:28AM (#14681857)
I am going with ...

    root # chpst -u 0zero id
    uid=1462(0zero) gid=1481(0zero) groups=1481(0zero)
    root # setuidgid 0zero id
    uid=1462(0zero) gid=1481(0zero) groups=1481(0zero)
    root #
... I would not; I would. Both of these use the getpwnam() library function of course. Their behaviours are ...

    root # chpst -u 0day id
    chpst: fatal: unable to get password/group file entry: file does not exist
    root # setuidgid 0day id
    setuidgid: FATAL: 0day: No such user.
    root #
... to abend when the account name is not found rather than continue on as the superuser without dropping privileges ...

* http://jdebp.eu./Softwares/nosh/guide/setuidgid.html

* http://cr.yp.to/daemontools/setuidgid.html

* http://untroubled.org/daemontools-encore/setuidgid.8.html

... as is documented in their user manuals, resulting in ...

    root # system-control convert-systemd-units ./0day.service
    root # install -d /home/0day
    root # ln -s /etc/service-bundles/services/sysinit-log 0day/log
    root # system-control start 0day 
    root # system-control status 0day
    /var/local/sv/0day: 
            State   : failed since 2017-07-02 11:14:17 +0100; 0s ago
            Main PID: 80083
             Started: exit 0 at 2017-07-02 11:13:35 +0100; 42s ago
                 Ran: exit 111 at 2017-07-02 11:14:17 +0100; 0s ago
            Config  : enabled
    2017-07-02 11:14:17.130870725 setuidgid: FATAL: 0day: No such user.
    2017-07-02 11:14:17.247334398 setuidgid: FATAL: 0day: No such user.
    2017-07-02 11:14:17.363857132 setuidgid: FATAL: 0day: No such user.
    2017-07-02 11:14:17.481175128 setuidgid: FATAL: 0day: No such user.
    2017-07-02 11:14:17.598958702 setuidgid: FATAL: 0day: No such user.
    root #
... the 0day service from the headlined bug report failing to start.
[ Parent | on HN ]
Re:Systemd can't handle the process privilege for username s... by ArneBab on Sunday July 02, 2017 @06:41AM (#14681897)
Or maybe 0pointer → http://0pointer.net/imprint
[ Parent | on HN ]
Re:Systemd can't handle the process privilege for username s... by digi_owl on Sunday July 02, 2017 @11:58AM (#14683053)
He seems to prefer various alcoholic drinks when posting not posting under his own name though...
[ Parent | on HN ]