7 ms·
1. Start with root to bind the port below 1024. 2. give up root because you don't need it any further. 3. Only accept non-root logins 4. when a user creates
by dragonfax 7mo ago
1. Start with root to bind the port below 1024.
2. give up root because you don't need it any further.
3. Only accept non-root logins
4. when a user creates a session, if they need root within the session they can obtain it via sudo or su.
- deleted 7mo ago[deleted]
- deleted 7mo ago[deleted]
- acdha 7mo agoThat still needs a way to change users, and OpenSSH already has privilege separation. That hardens the process somewhat to reduce the amount of code running in the process which can change the uid for a session but fundamentally something needs permission to call setuid() or the equivalent.
- accrual 7mo agoYes, but changing users is a function of the shell (or maybe more specifically /usr/bin/login), not the SSH daemon.
- acdha 7mo agoYea, but then we’ve recreated this CVE which is caused by calling login(1) unsafely. The point was that the person I was replying to misunderstood the problem and largely seemed to be conflating telnetd with OpenSSH.
- Aloha 7mo agoI'm not sure that you need root because of the port - I think login itself needs to run as root, otherwise it cant login to anything other than the account its running under.
- wiml 7mo agoYou still need to have privileges to become the userid of the user logging in. Openssh does do privsep, but you still need a privileged daemon.
- klempner 7mo agoCongratulations, you've created a server that lets people have shells running as the user running telnetd. You presumably want them to run as any (non root) user. The capability you need for that, to impersonate arbitrary (non-root) users on the system, is pretty damn close to being root.
- samlinnfer 7mo agoWell obviously each user just needs to run their own telnet daemon, on their own port of course.
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