Shellinabox

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shellinabox allows access to the command-line from web based terminal emulator. It is useful for web-based administrator access to a system. It is accessible to any JavaScript and CSS enabled web browser and does not require any additional browser plugins.[1].

Important
Connections to shellinaboxd are not secure unless SSL/TLS certificates have been installed or generated.

Installation

USE flags

USE flags for www-misc/shellinabox Export command line tools to a web based terminal emulator

pam Enable PAM support. local

Emerge

root #emerge --ask www-misc/shellinabox

Configuration

Securing the connection

The default configuration exposes a login shell with SSL disabled on the localhost interface only.

Information about the procedure for generating self-signed SSL certificates is explained here.

To generate an SSH certification for use shellinabox the following commands can be issued:

root #cd /etc/shellinabox/cert
root #openssl genrsa -des3 -out server.key 1024
root #openssl req -new -key server.key -out server.csr
root #cp server.key server.key.org
root #openssl rsa -in server.key.org -out server.key
root #openssl x509 -req -days 365 -in server.csr -signkey server.key -out server.crt
root #cat server.crt server.key > certificate.pem

For Gentoo user convenience, the ebuild maintainer has provided the above commands in a file located here: /etc/shellinabox/cert/gen_ssl_cert.bash

This script can simply be executed in order to generate the SSL certificate:

root #cd /etc/shellinabox/cert
root #bash gen_ssl_cert.bash

Service

OpenRC

Add the service to the default runlevel:

root #rc-update add shellinaboxd default

Start the service now:

root #rc-service shellinaboxd start

systemd

To start the service at boot:

root #systemctl enable shellinaboxd

Start the service now:

root #systemctl start shellinaboxd

Usage

After the service is running, open a web browser to the IP address of the system and port 4200:

user $firefox http://localhost:4200

Invocation

root #shellinaboxd --help
Usage: shellinaboxd [OPTIONS]...
Starts an HTTP server that serves terminal emulators to AJAX enabled browsers.

List of command line options:
  -b, --background[=PIDFILE]  run in background
  -c, --cert=CERTDIR          set certificate dir (default: $PWD)
      --cert-fd=FD            set certificate file from fd
      --css=FILE              attach contents to CSS style sheet
      --cgi[=PORTMIN-PORTMAX] run as CGI
  -d, --debug                 enable debug mode
  -f, --static-file=URL:FILE  serve static file from URL path
  -g, --group=GID             switch to this group (default: nogroup)
  -h, --help                  print this message
      --linkify=[none|normal|aggressive] default is "normal"
      --localhost-only        only listen on 127.0.0.1
      --no-beep               suppress all audio output
  -n, --numeric               do not resolve hostnames
  -m, --messages-origin=ORIGIN allow iframe message passing from origin
      --pidfile=PIDFILE       publish pid of daemon process
  -p, --port=PORT             select a port (default: 4200)
  -s, --service=SERVICE       define one or more services
  -t, --disable-ssl           disable transparent SSL support
      --disable-ssl-menu      disallow changing transport mode
      --disable-utmp-logging  disable logging to utmp and wtmp
  -q, --quiet                 turn off all messages
      --unixdomain-only=PATH:USER:GROUP:CHMOD listen on unix socket
  -u, --user=UID              switch to this user (default: nobody)
      --user-css=STYLES       defines user-selectable CSS options
  -v, --verbose               enable logging messages
      --version               prints version information
      --disable-peer-check    disable peer check on a session

Debug, quiet, and verbose are mutually exclusive.

One or more --service arguments define services that should be made available
through the web interface:
  SERVICE := <url-path> ':' APP
  APP     := 'LOGIN' | 'SSH' [ : <host> ] | USER ':' CWD ':' CMD
  USER    := 'AUTH' | <username> ':' <groupname>
  CWD     := 'HOME' | <dir>
  CMD     := 'SHELL' | <cmdline>

<cmdline> supports variable expansion:
  ${columns} - number of columns
  ${gid}     - gid id
  ${group}   - group name
  ${home}    - home directory
  ${lines}   - number of rows
  ${peer}    - name of remote peer
  ${realip}  - value of HTTP header field 'X-Real-IP'
  ${uid}     - user id
  ${url}     - the URL that serves the terminal session
  ${user}    - user name

One or more --user-css arguments define optional user-selectable CSS options.
These options show up in the right-click context menu:
  STYLES  := GROUP { ';' GROUP }*
  GROUP   := OPTION { ',' OPTION }*
  OPTION  := <label> ':' [ '-' | '+' ] <css-file>

OPTIONs that make up a GROUP are mutually exclusive. But individual GROUPs are
independent of each other.

Removal

Unmerge

root #emerge --ask --depclean www-misc/shellinabox

See also

  • bash — the default shell on Gentoo systems and a popular shell program found on many Linux systems.
  • ssh — an encrypted terminal program that replaces the classic telnet tool on Unix-like operating systems.

External resources

https://www.unixmen.com/shellinabox-a-web-based-ajax-terminal-emulator/ - A guide on setting up shellinabox.

References