Teleport truncates motd with PAM

[vad]

What happened:

I enabled PAM to get the MOTD. The MOTD is fine with ssh but is truncated with teleport (tsh ssh).

MOTD with tsh ssh:

Welcome to Ubuntu 18.04.1 LTS (GNU/Linux 4.15.0-1031-aws x86_64)

 * Documentation:  https://help.ubuntu.com
 * Management:     https://landscape.canonical.com
 * Support:        https://ubuntu.com/advantage

  System information as of Thu Jan 10 10:35:45 UTC 2019

  System load:  0.07               Processes:              130
  Usage of /:   30.4% of 19.32GB   Users logged in:        1
  Memory usage: 35%                IP address for eth0:    <IP>
  Swap usage:   0%                 IP address for ubuntu@myhost:~$ 

What you expected to happen:

This is MOTD with ssh:

$ ssh ubuntu@myhost
Welcome to Ubuntu 18.04.1 LTS (GNU/Linux 4.15.0-1031-aws x86_64)

 * Documentation:  https://help.ubuntu.com
 * Management:     https://landscape.canonical.com
 * Support:        https://ubuntu.com/advantage

  System information as of Thu Jan 10 10:31:34 UTC 2019

  System load:  0.56               Processes:              132
  Usage of /:   30.4% of 19.32GB   Users logged in:        1
  Memory usage: 35%                IP address for eth0:    <IP>
  Swap usage:   0%                 IP address for docker0: 172.17.0.1

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 * Canonical Livepatch is available for installation.
   - Reduce system reboots and improve kernel security. Activate at:
     https://ubuntu.com/livepatch

2 packages can be updated.
0 updates are security updates.


Last login: Thu Jan 10 10:05:34 2019 from <IP>
ubuntu@myhost:~$ 

How to reproduce it (as minimally and precisely as possible):

Enable PAM:

ssh_service:
  enabled: "yes"
  listen_addr: 0.0.0.0:3022
  pam:
    enabled: "yes"
    service_name: "teleport"

# diff /etc/pam.d/sshd /etc/pam.d/teleport 
22c22
< session    required     pam_loginuid.so
---
> #session    required     pam_loginuid.so

Due to issue #2476 .

Environment:

• Teleport version (use teleport version): Teleport v3.0.1 git:v3.0.1-0-g4ff9a7b0
• Tsh version (use tsh version): Teleport v3.0.1 git:v3.0.1-0-g4ff9a7b0
• OS (e.g. from /etc/os-release): Ubuntu 18.04.1 LTS

Relevant Debug Logs If Applicable

Logs are fine:

Jan 10 10:35:45 ip-172-31-42-53 teleport[3303]: pam_unix(teleport:session): session opened for user ubuntu by (uid=0)