Bug 1778424

Description of problem:

I was surprised (on Debian) that OpenSMTPD lost a cron mail that cron managed to submit while smtpd was not running (stopped temporarily for maintenance). I expected smtpd to send it later, when I start it, but the message just kept sitting in /var/spool/smtpd/offline. Then I retested this on Fedora 31, and found that it is also affected.

Version-Release number of selected component (if applicable): opensmtpd-6.0.3p1-8

# ls -l /etc/alternatives/mta
lrwxrwxrwx 1 root root 28 Nov 29 13:59 /etc/alternatives/mta -> /usr/sbin/sendmail.opensmtpd

How reproducible: always

Steps to Reproduce:

1. dnf install opensmtpd
2. systemctl start opensmtpd  # so that it creates the hierarchy under /var/spool/smtpd
3. systemctl stop opensmtpd  # let's pretend it was stopped and forgotten by accident
4. Use a text editor co create a "mail.txt" file, containing some valid mail headers, a blank line, and a body, suitable for submission to sendmail
5. sendmail -f you -t < mail.txt
6. As a user, it says "cannot create temporary file /var/spool/smtpd/offline/1575154903.XXXXMn5Om8: Permission denied". As root, it returns error code 75 and puts the email into /var/spool/smtpd/offline, as expected
7. systemctl start opensmtpd

Actual results: the offline message sits in /var/spool/smtpd/offline forever.

Expected results: smtpd should pick up the offline message and send it out.

Additional info:

This has been traced to the fact that the package installs /usr/sbin/smtpctl (pointed to by /usr/sbin/sendmail.opensmtpd) with the wrong permissions. Upstream expects /usr/sbin/smtpctl to be setgid to the same group that owns /var/spool/smtpd/offline, while Fedora's package installs it setgid root.

See:

# ls -ld /var/spool/smtpd/offline/
drwxrwx--- 2 root smtpq 6 Nov 29 14:04 /var/spool/smtpd/offline/

Upstream code that checks permissions on offline queue files: https://github.com/OpenSMTPD/OpenSMTPD/blob/c139eb1610e931739d6cde4194c9560124b08165/smtpd/smtpd.c#L1604

Upstream fix: https://github.com/OpenSMTPD/OpenSMTPD/commit/e02d05d2ec470899363de4be658aca26de5a2466