Package: tinysshd
Version: 20190101-1
Severity: normal
This has annoyed me for a while, but I only just today realized it was an
actual bug and not simply a missing feature.
I had to use "screen" to run two SSH clients at once. I tried using "ssh -f"
and could not reproduce the problem.
I am using "-F /dev/null" to disable my ~/.ssh/config.
I have ControlMaster enabled by default on all my SSH connections with
this at the bottom of my .ssh/config:
Host *
ControlMaster auto
ControlPath ~/.ssh/master-%C
ControlPersist 3600
If you do this (like me), a quick workaround that avoids this bug is to simply
do
"ssh -M tinyssh-host" instead of
"ssh tinyssh-host".
This effectively disables ControlMaster for that one connection.
This issue is not discussed in upstream's issue tracker:
https://github.com/janmojzis/tinyssh/issues
I have not yet tested a newer upstream version (currently available in
salsa, but not in sid or experimental yet).
Here is a transcript of me reproducing the problem. I am connecting
to a basic Debian 11 Live VM running in qemu, with its port 22
forwarded to localhost 2022.
bash5$ ssh -F/dev/null -oUserKnownHostsFile=/dev/null
-oStrictHostKeyChecking=no root@localhost -p2022 systemctl status
system-tinysshd.slice
Warning: Permanently added '[localhost]:2022' (ED25519) to the list of
known hosts.
● system-tinysshd.slice
Loaded: loaded
Active: active since Mon 2021-09-27 14:40:45 AEST; 198ms ago
Tasks: 2
Memory: 3.8M
CPU: 178ms
CGroup: /system.slice/system-tinysshd.slice
└─[email protected]:22-10.0.2.2:38146.service
├─405 /usr/sbin/tinysshd -v -- /etc/tinyssh/sshkeydir
└─408 systemctl status system-tinysshd.slice
Sep 27 14:40:45 main.lan systemd[1]: Created slice system-tinysshd.slice.
Sep 27 14:40:46 main.lan tinysshd[405]: tinysshd: BIFzIJ9B: info:
connection from 10.0.2.2:38146 {main_tinysshd.c:106}
Sep 27 14:40:46 main.lan tinysshd[405]: tinysshd: BIFzIJ9B: info: auth:
root: ssh-ed25519
AAAAC3NzaC1lZDI1NTE5AAAAIIapAZ0E0353DaY6xBnasvu/DOvdWdKQ6RQURwq4l6Wu accepted
{packet_auth.c:155}
# Run two ssh clients at once, sharing a control master.
# When the second one starts, tinysshd crashes, so the first one hangs up.
bash5$ screen ssh -F/dev/null -oUserKnownHostsFile=/dev/null
-oStrictHostKeyChecking=no root@localhost -p2022 -oControlMaster=auto
-oControlPath=~/.ssh/master-%C -oControlPersist=3600
bash5$ screen ssh -F/dev/null -oUserKnownHostsFile=/dev/null
-oStrictHostKeyChecking=no root@localhost -p2022 -oControlMaster=auto
-oControlPath=~/.ssh/master-%C -oControlPersist=3600
# Examining the system after the problem happened.
bash5$ ssh -F/dev/null -oUserKnownHostsFile=/dev/null
-oStrictHostKeyChecking=no root@localhost -p2022 systemctl status
system-tinysshd.slice
Warning: Permanently added '[localhost]:2022' (ED25519) to the list of
known hosts.
● system-tinysshd.slice
Loaded: loaded
Active: active since Mon 2021-09-27 14:40:45 AEST; 14s ago
Tasks: 4
Memory: 6.9M
CPU: 429ms
CGroup: /system.slice/system-tinysshd.slice
├─[email protected]:22-10.0.2.2:38154.service
│ ├─423 /usr/sbin/tinysshd -v -- /etc/tinyssh/sshkeydir
│ └─426 -bash
└─[email protected]:22-10.0.2.2:38158.service
├─433 /usr/sbin/tinysshd -v -- /etc/tinyssh/sshkeydir
└─436 systemctl status system-tinysshd.slice
Sep 27 14:40:46 main.lan tinysshd[405]: tinysshd: BIFzIJ9B: info:
connection from 10.0.2.2:38146 {main_tinysshd.c:106}
Sep 27 14:40:46 main.lan tinysshd[405]: tinysshd: BIFzIJ9B: info: auth:
root: ssh-ed25519
AAAAC3NzaC1lZDI1NTE5AAAAIIapAZ0E0353DaY6xBnasvu/DOvdWdKQ6RQURwq4l6Wu accepted
{packet_auth.c:155}
Sep 27 14:40:46 main.lan tinysshd[405]: tinysshd: BIFzIJ9B: info: finished
{main_tinysshd.c:287}
Sep 27 14:40:55 main.lan tinysshd[412]: tinysshd: W19qgD40: info:
connection from 10.0.2.2:38150 {main_tinysshd.c:106}
Sep 27 14:40:55 main.lan tinysshd[412]: tinysshd: W19qgD40: info: auth:
root: ssh-ed25519
AAAAC3NzaC1lZDI1NTE5AAAAIIapAZ0E0353DaY6xBnasvu/DOvdWdKQ6RQURwq4l6Wu accepted
{packet_auth.c:155}
Sep 27 14:40:57 main.lan tinysshd[412]: tinysshd: W19qgD40: BUG: (protocol
error){channel.c:57}
Sep 27 14:40:57 main.lan tinysshd[423]: tinysshd: j6vr2uNR: info:
connection from 10.0.2.2:38154 {main_tinysshd.c:106}
Sep 27 14:40:57 main.lan tinysshd[423]: tinysshd: j6vr2uNR: info: auth:
root: ssh-ed25519
AAAAC3NzaC1lZDI1NTE5AAAAIIapAZ0E0353DaY6xBnasvu/DOvdWdKQ6RQURwq4l6Wu accepted
{packet_auth.c:155}
Sep 27 14:40:59 main.lan tinysshd[433]: tinysshd: CGtApdsN: info:
connection from 10.0.2.2:38158 {main_tinysshd.c:106}
Sep 27 14:40:59 main.lan tinysshd[433]: tinysshd: CGtApdsN: info: auth:
root: ssh-ed25519
AAAAC3NzaC1lZDI1NTE5AAAAIIapAZ0E0353DaY6xBnasvu/DOvdWdKQ6RQURwq4l6Wu accepted
{packet_auth.c:155}
bash5$ ssh -F/dev/null -oUserKnownHostsFile=/dev/null
-oStrictHostKeyChecking=no root@localhost -p2022 systemctl --state=failed
Warning: Permanently added '[localhost]:2022' (ED25519) to the list of
known hosts.
UNIT LOAD ACTIVE SUB
DESCRIPTION
● [email protected]:22-10.0.2.2:38150.service loaded failed failed Tiny
SSH server (10.0.2.2:38150)
LOAD = Reflects whether the unit definition was properly loaded.
ACTIVE = The high-level unit activation state, i.e. generalization of SUB.
SUB = The low-level unit activation state, values depend on unit type.
1 loaded units listed.
bash5$ ssh -F/dev/null -oUserKnownHostsFile=/dev/null
-oStrictHostKeyChecking=no root@localhost -p2022 journalctl -u
[email protected]:22-10.0.2.2:38150.service
Warning: Permanently added '[localhost]:2022' (ED25519) to the list of
known hosts.
-- Journal begins at Mon 2021-09-27 14:40:36 AEST, ends at Mon 2021-09-27
14:41:55 AEST. --
Sep 27 14:40:55 main.lan systemd[1]: Starting Tiny SSH server
(10.0.2.2:38150)...
Sep 27 14:40:55 main.lan systemd[1]: Started Tiny SSH server
(10.0.2.2:38150).
Sep 27 14:40:55 main.lan tinysshd[412]: tinysshd: W19qgD40: info:
connection from 10.0.2.2:38150 {main_tinysshd.c:106}
Sep 27 14:40:55 main.lan tinysshd[412]: tinysshd: W19qgD40: info: auth:
root: ssh-ed25519
AAAAC3NzaC1lZDI1NTE5AAAAIIapAZ0E0353DaY6xBnasvu/DOvdWdKQ6RQURwq4l6Wu accepted
{packet_auth.c:155}
Sep 27 14:40:57 main.lan tinysshd[412]: tinysshd: W19qgD40: BUG: (protocol
error){channel.c:57}
Sep 27 14:40:57 main.lan systemd[1]:
[email protected]:22-10.0.2.2:38150.service: Main process exited,
code=exited, status=111/n/a
Sep 27 14:40:57 main.lan systemd[1]:
[email protected]:22-10.0.2.2:38150.service: Failed with result 'exit-code'.
Sep 27 14:40:57 main.lan systemd[1]:
[email protected]:22-10.0.2.2:38150.service: Unit process 415 (bash) remains
running after unit stopped.
# Showing what versions of stuff I'm running.
bash5$ ssh -F/dev/null -oUserKnownHostsFile=/dev/null
-oStrictHostKeyChecking=no root@localhost -p2022 dpkg-query -W base-files
tinysshd linux-image-cloud-amd64
Warning: Permanently added '[localhost]:2022' (ED25519) to the list of
known hosts.
base-files 11.1
linux-image-cloud-amd64 5.10.46-5
tinysshd 20190101-1
