Bug#926719: SFTP ProFTPD terminating (signal 11) after Update to 1.3.5e-0+deb8u1

[Timo Müller]

Hello,

after testing with different working and not working configs of proftpd we think we found a workaround.

The login is working with the following config:

<IfModule mod_sftp.c>
  <VirtualHost X.X.X.X>
    SFTPEngine                  on
    SFTPPAMEngine               off
    SFTPLog                     /var/log/proftpd/sftp.log
    Port                        115
    SFTPHostKey                 /etc/ssh/ssh_host_rsa_key
    SFTPHostKey                 /etc/ssh/ssh_host_dsa_key
    SFTPAuthorizedUserKeys      file:~/.sftp/authorized_keys
    SFTPCompression             delayed
    MaxLoginAttempts            6
    SFTPClientAlive             3 15
    DefaultRoot                 ~
    ListOptions                 -la
    AuthUserFile                /etc/proftpd/proftpd.passwd
    RequireValidShell           off
  </VirtualHost>
</IfModule>

Now if you remove the part "SFTPPAMEngine off" the login doesn't work anymore.
We tried it several times and the login doesn't work if the SFTPPAMEngine is active.

If you login via Shell and you have to enter a password, you can see the difference in the password request.

Normally it is displayed like that: 

$ sftp -P 115 <Username>@172.31.XXX.XXX

> user at server password:

If the SFTPPAMEngine is active only the "password:" part is displayed, so the user at server part is lost. 

Kind regards,
Timo.