sish

An open source serveo/ngrok alternative.

Deploy

Builds are made automatically on Google Cloud Build and Dockerhub. Feel free to either use the automated binaries or to build your own. If you submit a PR and would like access to Google Cloud Build's output (including pre-made PR binaries), feel free to let me know.

1. Pull the Docker image

   • docker pull antoniomika/sish:latest

2. Run the image

   • docker run -itd --name sish \
       -v ~/sish/ssl:/ssl \
       -v ~/sish/keys:/keys \
       -v ~/sish/pubkeys:/pubkeys \
       --net=host antoniomika/sish:latest \
       -sish.addr=:22 \
       -sish.https=:443 \
       -sish.http=:80 \
       -sish.httpsenabled=true \
       -sish.httpspems=/ssl \
       -sish.keysdir=/pubkeys \
       -sish.pkloc=/keys/ssh_key \
       -sish.bindrandom=false

3. SSH to your host to communicate with sish

   • ssh -p 2222 -R 80:localhost:8080 ssi.sh

Docker Compose

You can also use Docker Compose to setup your sish instance. This includes taking care of SSL via Let's Encrypt for you. This uses the adferrand/docker-letsencrypt-dns container to handle issuing wildcard certifications over DNS. For more information on how to use this, head to that link above. Generally, you can deploy your service like so:

DOMAIN=yourdomain.com \
[email protected] \
LEXICON_PROVIDER=cloudflare \
LEXICON_PROVIDER_OPTIONS="[email protected] --auth-token=your-auth-token" \
docker-compose -f deploy/docker-compose.yml up -d

How it works

SSH can normally forward local and remote ports. This service implements an SSH server that only does that and nothing else. The service supports multiplexing connections over HTTP/HTTPS with WebSocket support. Just assign a remote port as port 80 to proxy HTTP traffic and 443 to proxy HTTPS traffic. If you use any other remote port, the server will listen to the port for connections, but only if that port is available.

You can choose your own subdomain instead of relying on a randomly assigned one by setting the -sish.forcerandomsubdomain option to false and then selecting a subdomain by prepending it to the remote port specifier:

ssh -p 2222 -R foo:80:localhost:8080 ssi.sh

If the selected subdomain is not taken, it will be assigned to your connection.

Authentication

If you want to use this service privately, it supports both public key and password authentication. To enable authentication, set -sish.auth=true as one of your CLI options and be sure to configure -sish.password or -sish.keysdir to your liking. The directory provided by -sish.keysdir is watched for changes and will reload the authorized keys automatically. The authorized cert index is regenerated on directory modification, so removed public keys will also automatically be removed. Files in this directory can either be single key per file, or multiple keys per file separated by newlines, similar to authorized_keys. Password auth can be disabled by setting -sish.password="" as a CLI option.

One of my favorite ways of using this for authentication is like so:

sish@sish0:~/sish/pubkeys# curl https://github.com/antoniomika.keys > antoniomika

This will load my public keys from GitHub, place them in the directory that sish is watching, and then load the pubkey. As soon as this command is run, I can SSH normally and it will authorize me.

Whitelisting IPs

Whitelisting IP ranges or countries is also possible. Whole CIDR ranges can be specified with the -sish.whitelistedips option that accepts a comma-separated string like "192.30.252.0/22,185.199.108.0/22". If you want to whitelist a single IP, use the /32 range.

To whitelist countries, use sish.whitelistedcountries with a comma-separated string of countries in ISO format (for example, "pt" for Portugal). You'll also need to set -sish.usegeodb to true.

Demo - At this time, the demo instance has been set to require auth due to abuse

There is a demo service (and my private instance) currently running on ssi.sh that doesn't require any authentication. This service provides default logging (errors, connection IP/username, and pubkey fingerprint). I do not log any of the password authentication data or the data sent within the service/tunnels. My deploy uses the exact deploy steps that are listed above. This instance is for testing and educational purposes only. You can deploy this extremely easily on any host (Google Cloud Platform provides an always-free instance that this should run perfectly on). If the service begins to accrue a lot of traffic, I will enable authentication and then you can reach out to me to get your SSH key whitelisted (make sure it's on GitHub and you provide me with your GitHub username).

Notes

1. This is by no means production ready in any way. This was hacked together and solves a fairly specific use case.
   • You can help it get production ready by submitting PRs/reviewing code/writing tests/etc
2. This is a fairly simple implementation, I've intentionally cut corners in some places to make it easier to write.
3. If you have any questions or comments, feel free to reach out via email [email protected] or on freenode IRC #sish

CLI Flags

sh-3.2# ./sish -h
Usage of ./sish:
  -sish.addr string
        The address to listen for SSH connections (default "localhost:2222")
  -sish.auth
        Whether or not to require auth on the SSH service
  -sish.bannedcountries string
        A comma separated list of banned countries
  -sish.bannedips string
        A comma separated list of banned ips
  -sish.bannedsubdomains string
        A comma separated list of banned subdomains (default "localhost")
  -sish.bindrandom
        Bind ports randomly (OS chooses) (default true)
  -sish.bindrange string
        Ports that are allowed to be bound (default "0,1024-65535")
  -sish.cleanupunbound
        Whether or not to cleanup unbound (forwarded) SSH connections (default true)
  -sish.debug
        Whether or not to print debug information
  -sish.domain string
        The domain for HTTP(S) multiplexing (default "ssi.sh")
  -sish.forcerandomsubdomain
        Whether or not to force a random subdomain (default true)
  -sish.http string
        The address to listen for HTTP connections (default "localhost:80")
  -sish.httpport int
        The port to use for http command output
  -sish.https string
        The address to listen for HTTPS connections (default "localhost:443")
  -sish.httpsenabled
        Whether or not to listen for HTTPS connections
  -sish.httpspems string
        The location of pem files for HTTPS (fullchain.pem and privkey.pem) (default "ssl/")
  -sish.httpsport int
        The port to use for https command output
  -sish.idletimeout int
        Number of seconds to wait for activity before closing a connection (default 5)
  -sish.keysdir string
        Directory for public keys for pubkey auth (default "pubkeys/")
  -sish.logtoclient
        Whether or not to log http requests to the client
  -sish.password string
        Password to use for password auth (default "S3Cr3tP4$$W0rD")
  -sish.pkloc string
        SSH server private key (default "keys/ssh_key")
  -sish.pkpass string
        Passphrase to use for the server private key (default "S3Cr3tP4$$phrAsE")
  -sish.proxyprotoenabled
        Whether or not to enable the use of the proxy protocol
  -sish.proxyprotoversion string
        What version of the proxy protocol to use. Can either be 1, 2, or userdefined. If userdefined, the user needs to add a command to SSH called proxyproto:version (ie proxyproto:1) (default "1")
  -sish.redirectroot
        Whether or not to redirect the root domain (default true)
  -sish.redirectrootlocation string
        Where to redirect the root domain to (default "https://github.com/antoniomika/sish")
  -sish.subdomainlen int
        The length of the random subdomain to generate (default 3)
  -sish.tcpalias
        Whether or not to allow the use of TCP aliasing
  -sish.usegeodb
        Whether or not to use the maxmind geodb
  -sish.verifyorigin
        Whether or not to verify origin on websocket connection (default true)
  -sish.verifyssl
        Whether or not to verify SSL on proxy connection (default true)
  -sish.version
        Print version and exit
  -sish.whitelistedcountries string
        A comma separated list of whitelisted countries
  -sish.whitelistedips string
        A comma separated list of whitelisted ips