shizunge/endlessh-go repository overview

⁠endlessh-go

A golang implementation of endlessh⁠ exporting Prometheus metrics, visualized by a Grafana dashboard.

⁠Introduction

Endlessh⁠ is a great idea that not only blocks the brute force SSH attacks, but also wastes attackers time as a kind of counter-attack. Besides trapping the attackers, I also want to visualize the Geolocations and other statistics of the sources of attacks. Unfortunately the wonderful original C implementation of endlessh⁠ only provides text based log, but I do not like the solution that writes extra scripts to parse the log outputs, then exports the results to a dashboard, because it would introduce extra layers in my current setup and it would depend on the format of the text log file rather than some structured data. Thus I create this golang implementation of endlessh to export Prometheus⁠ metrics and a Grafana⁠ dashboard to visualize them.

If you want a dashboard of sources of attacks and do not mind the endlessh server, besides trapping the attackers, does extra things including: translating IP to Geohash, exporting Prometheus metrics, and using more memory (about 10MB), this is the solution for you.

⁠Getting Started

Clone the repo then build from source:

go build .
./endlessh-go &

Alternatively, you can use the docker image⁠:

docker run -d -p 2222:2222 shizunge/endlessh-go -logtostderr -v=1

It listens to port 2222 by default.

Then you can try to connect to the endlessh server. Your SSH client should hang there.

ssh -p 2222 localhost

If you want log like the C implementation⁠, you need to set both CLI arguments -logtostderr and -v=1, then the log will go to stderr. You can set different log destinations via CLI arguments.

Also check out examples⁠ for the setup of the full stack.

⁠Usage

./endlessh-go --help

Usage of ./endlessh-go
  -alsologtostderr
        log to standard error as well as files
  -conn_type string
        Connection type. Possible values are tcp, tcp4, tcp6 (default "tcp")
  -enable_prometheus
        Enable prometheus (deprecated, use prometheus_enabled)
  -geoip_supplier string
        Supplier to obtain Geohash of IPs. Possible values are "off", "ip-api", "max-mind-db" (default "off")
  -healthcheck
        Perform healthcheck and exit. GET healthcheck_host:healthcheck_port/health and exit 1 if status is not ok or timeout is exceeded.
  -healthcheck_enabled
        Enable healthcheck
  -healthcheck_host string
        The address for healthcheck. (default "127.0.0.1")
  -healthcheck_port string
        HTTP port for healthcheck; Serves JSON with status and uptime at /health. (default "51000")
  -host string
        SSH listening address (default "0.0.0.0")
  -interval_ms int
        Message millisecond delay (default 1000)
  -line_length int
        Maximum banner line length (default 32)
  -log_backtrace_at value
        when logging hits line file:N, emit a stack trace
  -log_dir string
        If non-empty, write log files in this directory
  -log_link string
        If non-empty, add symbolic links in this directory to the log files
  -logbuflevel int
        Buffer log messages logged at this level or lower (-1 means don't buffer; 0 means buffer INFO only; ...). Has limited applicability on non-prod platforms.
  -logtostderr
        log to standard error instead of files
  -max_clients int
        Maximum number of clients (default 4096)
  -max_mind_db string
        Path to the MaxMind DB file.
  -port value
        SSH listening port. You may provide multiple -port flags to listen to multiple ports. (default "2222")
  -prometheus_clean_unseen_seconds int
        Remove series if the IP is not seen for the given time. Set to 0 to disable. (default 0)
  -prometheus_enabled
        Enable prometheus
  -prometheus_entry string
        Entry point for prometheus (default "metrics")
  -prometheus_host string
        The address for prometheus (default "0.0.0.0")
  -prometheus_port string
        The port for prometheus (default "2112")
  -proxy_protocol_enabled
        Enable PROXY protocol support. This causes the server to expect PROXY protocol headers on incoming connections.
  -proxy_protocol_read_header_timeout_ms int
        Timeout for reading the PROXY protocol header in milliseconds. If the connection does not send a valid PROXY protocol header in this time, the header is ignored. (default 200)
  -stderrthreshold value
        logs at or above this threshold go to stderr (default 2)
  -v value
        log level for V logs
  -vmodule value
        comma-separated list of pattern=N settings for file-filtered logging

⁠Metrics

Endlessh-go exports the following Prometheus metrics.

The metrics is off by default, you can turn it via the CLI argument -prometheus_enabled.

It listens to port 2112 and entry point is /metrics by default. The port and entry point can be changed via CLI arguments.

The endlessh-go server stores the geohash of attackers as a label on endlessh_client_open_count, which is also off by default. You can turn it on via the CLI argument -geoip_supplier. The endlessh-go uses service from ip-api⁠, which may enforce a query rate and limit commercial use. Visit their website for their terms and policies.

You could also use an offline GeoIP database from MaxMind⁠ by setting -geoip_supplier to max-mind-db and -max_mind_db to the path of the database file.

⁠Healthcheck

The endlessh-go server exposes an HTTP health endpoint when the -healthcheck_enabled flag is set. By default it listens on 127.0.0.1:51000 at /health and returns a JSON like this:

{
      "status": "ok",
      "uptime": 123.456789012
}

status is always "ok".

uptime is the number of seconds since the server started. The host and port can be changed via -healthcheck_host and -healthcheck_port.

The docker image⁠ includes a built-in HEALTHCHECK that runs every 30 seconds.

⁠Dashboard

The dashboard requires Grafana 8.2.

You can import the dashboard from Grafana.com using ID 15156⁠

The dashboard visualizes data for the selected time range.

The IP addresses are clickable and link you to the ARIN⁠ database.

⁠Contacts

If you have any problems or questions, please contact me through a GitHub issue⁠