SSH Piper

SSH Piper works as a proxy-like ware, and route connections by username, src ip , etc.

+---------+                      +------------------+          +-----------------+
|         |                      |                  |          |                 |
|   Bob   +----ssh -l bob----+   |   SSH Piper   +------------->   Bob' machine  |
|         |                  |   |               |  |          |                 |
+---------+                  |   |               |  |          +-----------------+
                             +---> pipe-by-name--+  |                             
+---------+                  |   |               |  |          +-----------------+
|         |                  |   |               |  |          |                 |
|  Alice  +----ssh -l alice--+   |               +------------->  Alice' machine |
|         |                      |                  |          |                 |
+---------+                      +------------------+          +-----------------+


 Downstream                         SSH Piper                       Upstream

Demo

Install

with Go

go get -u github.com/tg123/sshpiper/sshpiperd

with pam module support

go get -u -tags pam github.com/tg123/sshpiper/sshpiperd

with Docker image

docker run farmer1992/sshpiperd

Run with Workding Dir upstream driver

docker run -d -p 2222:2222 \
  -v /etc/ssh/ssh_host_rsa_key:/etc/ssh/ssh_host_rsa_key \
  -v /YOUR_WORKING_DIR:/var/sshpiper \
  farmer1992/sshpiperd

Run with Additional Challenge

use env SSHPIPERD_CHALLENGER to specify which challenger to use

docker run -d -p 2222:2222 \
  -e SSHPIPERD_CHALLENGER=pam \
  -v /YOUR_PAM_CONFIG:/etc/pam.d/sshpiperd \
  -v /etc/ssh/ssh_host_rsa_key:/etc/ssh/ssh_host_rsa_key \
  -v /YOUR_WORKING_DIR:/var/sshpiper \
  farmer1992/sshpiperd

with Snap

sudo snap install sshpiperd

configure with snap

sudo snap set sshpiperd 'port=3333'

sudo snap restart sshpiperd

NOTE:

Default working dir for snap verion is /var/snap/sshpiperd/common
use classic mode if PAM is not working: sudo snap install --classic sshpiperd

Quick start

Just run showme.sh in sshpiperd example directory or Copy paste command below to run

go get github.com/tg123/sshpiper/sshpiperd && `go env GOPATH`/src/github.com/tg123/sshpiper/sshpiperd/example/showme.sh

the example script will setup a sshpiper server using

bitbucket -> bitbucket@bitbucket.org:22 # ssh 127.0.0.1 -p 2222 -l bitbucket
github -> github@github.com:22 # ssh 127.0.0.1 -p 2222 -l github
gitlab -> gitlab@gitlab.com:22 # ssh 127.0.0.1 -p 2222 -l gitlab

connect to gitlab

$ ssh 127.0.0.1 -p 2222 -l gitlab
Permission denied (publickey).

connect to github.com

$ ssh 127.0.0.1 -p 2222 -l github
Permission denied (publickey).

Configuration

sshpiper provides 3 pluginable components to highly customize your piper

Upstream Driver
Additional Challenge
Auditor

sshpiperd daemon -h to learn more

Upstream Driver (`--upstream-driver=`)

Upstream driver helps sshpiper to find which upstream host to connect and how to connect.

For example, you can change the username when connecting to upstream sshd by config upstream driver

Available Upstream Drivers

Workding Directory

Working Dir is a /home-like directory. SSHPiperd read files from workingdir/[username]/ to know upstream's configuration.
Database Driver

Database upstream driver connected to popular databases, such as mysql, pg or sqlite etc to provide upstream's information.

How to do public key authentication when using sshpiper

During SSH publickey auth, RFC 4252 Section 7, ssh client sign session_id and some other data using private key into a signature sig. This is for server to verify that the connection is from the client not the man in the middle.

However, sshpiper actually holds two ssh connection, and it is doing what the man in the middle does. the two ssh connections' session_id will never be the same, because they are hash of the shared secret. RFC 4253 Section 7.2.

To support publickey auth, sshpiper will modify the sig using a private key provided by upstream driver. e.g. (id_rsa) in the workingdir/[username]/.

How this work

+------------+        +------------------------+                       
|            |        |                        |                       
|   client   |        |   SSH Piper            |                       
|   PK_X     +-------->      |                 |                       
|            |        |      v                 |                       
|            |        |   Check PK_X           |                       
+------------+        |   in authorized_keys   |                       
                      |      |                 |                       
                      |      |                 |     +----------------+
                      |      v                 |     |                |
                      |   sign agian           |     |   server       |
                      |   using PK_Y  +-------------->   check PK_Y   |
                      |                        |     |                |
                      |                        |     |                |
                      +------------------------+     +----------------+

e.g.

on client

ssh-copy-id -i PK_X test@sshpiper

on ssh piper server

ln -s ~test/.ssh/authorized_keys workingdir/test/authorized_keys
ssh-keygen -N '' -f workingdir/test/id_rsa  # this is PK_Y
ssh-copy-id -i workingdir/test/id_rsa test@server

now ssh test@sshpiper -i -i PK_X, sshpiper will send PK_Y to server instead of PK_X.

Additional Challenge (`--challenger-driver=`)

sshpiper allows you to add your own challenge before dialing to the upstream. if a client failed in this challenge, connection will be closed. however, the client has to pass the upstream server's auth in order to establish the whole connection. Additional Challenge is required, but not enough.

This is useful when you want use publickey and something like google-authenticator together. OpenSSH do not support use publickey and other auth together.

Available Challengers

pam

Linux-PAM challenger

this module use the pam service called sshpiperd

you can configure the rule at /etc/pam.d/sshpiperd

azdevcode

Support Azure AD device code grant, More info

sshpier will ask user to login using webpage

To sign in, use a web browser to open the page https://microsoft.com/devicelogin and enter the code ****** to authenticate.

authy

Support token and onetouch from https://authy.com/

Auditor for pipes (`--auditor-driver=`)

Auditor provides hook for messages transfered by SSH Piper which cloud log messages onto disks or filter some specific message on the fly.

Available Auditor

SSH Session logging (--auditor-driver=typescript-logger)

When record_typescript is allowed, each piped connection would be recorded into typescript in --auditor-typescriptlogger-outputdir.

The file format is compatible with scriptreplay(1)

Example:

$ ./sshpiperd daemon --auditor-driver=typescript-logger

ssh user_name@127.0.0.1 -p 2222
... do some commands
exit


$ cd workingdir/user_name
$ ls *.timing *.typescript
1472847798.timing 1472847798.typescript

$ scriptreplay -t 1472847798.timing 1472847798.typescript # will replay the ssh session