kex_exchange_identification: Connection closed by remote host

[richardleeps]

Describe the bug
Unable to connect to ssh target through an egress worker. Getting the error message "Connection closed by 127.0.0.1 port 52471"
The SSH target is a managed application. We are able to connect to other ssh targets such as ubuntu VM's through the same egress worker.

Error message when connection with the client

ssh 127.0.0.1 -p 52471 -o NoHostAuthenticationForLocalhost=yes

debug1: Local version string SSH-2.0-OpenSSH_9.6
kex_exchange_identification: Connection closed by remote host
Connection closed by 127.0.0.1 port 52471

When we connect from the egress worker directly to the target its working

ssh admin@10.10.1.1

debug1: Local version string SSH-2.0-OpenSSH_8.9p1 Ubuntu-3ubuntu0.6
debug1: Remote protocol version 2.0, remote software version OpenSSH_8.2p1 Ubuntu-4ubuntu0.11
debug1: compat_banner: match: OpenSSH_8.2p1 Ubuntu-4ubuntu0.11 pat OpenSSH* compat 0x04000000

To Reproduce
Steps to reproduce the behavior:

1. Start Boundary Client
2. Connect the target
3. Error is there
   MacBook-Pro-2 ~ % ssh 127.0.0.1 -p 52471 -o NoHostAuthenticationForLocalhost=yes
   Connection closed by 127.0.0.1 port 52471

Expected behavior
A succesfull connection directly from a boundary client

Additional context
Similar issue was dropped (#765) but was closed due to no response

[AdamBouhmad]

Hey @richardleeps, what version of Boundary are you running(client & controller)? Also curious if you're able to reproduce on 0.16.

[richardleeps]

@AdamBouhmad - All boundary nodes are on v0.16.0+ent
I just tried and still the same result.

If I compare the SSH debug this is what I see

ssh 127.0.0.1 -p 63924 -o NoHostAuthenticationForLocalhost=yes -vv
OpenSSH_9.6p1, LibreSSL 3.3.6
<snip>
debug1: Local version string SSH-2.0-OpenSSH_9.6
kex_exchange_identification: Connection closed by remote host
Connection closed by 127.0.0.1 port 63924

While direct from the egress worker this is wat we get

ssh vmadmin@10.10.1.1 -vvv
OpenSSH_8.9p1 Ubuntu-3ubuntu0.6, OpenSSL 3.0.2 15 Mar 2022
<snip>
debug1: Local version string SSH-2.0-OpenSSH_8.9p1 Ubuntu-3ubuntu0.6
debug1: Remote protocol version 2.0, remote software version OpenSSH_8.2p1 Ubuntu-4ubuntu0.11
debug1: compat_banner: match: OpenSSH_8.2p1 Ubuntu-4ubuntu0.11 pat OpenSSH* compat 0x04000000

[AdamBouhmad]

Thanks for the quick response @richardleeps. Do you mind sharing over your worker logs so we can dig into this further? Feel free to email me at adam.bouhmad@hashicorp.com.