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Safe, parallel access to Unix shells from Ruby

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Octocat-spinner-32 bin
Octocat-spinner-32 lib
Octocat-spinner-32 try
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Octocat-spinner-32 CHANGES.txt
Octocat-spinner-32 LICENSE.txt First public release April 04, 2009
Octocat-spinner-32 README.rdoc
Octocat-spinner-32 Rakefile
Octocat-spinner-32 rye.gemspec
README.rdoc

Rye - v0.5

Safely run SSH commands on a bunch of machines at the same time (from Ruby).

Rye is similar to Rush but everything happens over SSH (no HTTP daemon) and the default settings are less powerful (for safety). For example, file globs and the “rm” command are disabled so unless otherwise specified, you can't do this: rbox.rm('-rf', '/etc/*/').

See the examples below (which are taken from bin/try).

Installation

One of:

$ sudo gem install rye
$ sudo gem install delano-rye --source http://gems.github.com/
$ git clone git://github.com/delano/rye.git

EXAMPLE 1 – Basic Usage

rbox = Rye::Box.new('localhost')

# Commands are run as methods on the Rye::Box object
puts rbox.uptime                   # => 11:02  up 16:01, 3 users

# The response value for all commands is a Rye::Rap object. The rap is a
# subclass of Array so you can treat it as an Array, but it can also act 
# like a String if there's only one element. 
puts rbox.ls('rye.test')           # => ""
puts rbox.ls('rye.test').stderr    # => ls: rye.test: No such file or directory

puts rbox.touch('rye.test')        # => ""
puts rbox.rm('rye.test')           # => ""

# You can change directories
puts rbox.pwd                      # => /home/rye
puts rbox['/usr/bin'].pwd          # => /usr/bin
puts rbox.pwd                      # => /usr/bin
puts rbox.cd('/home/rye').pwd      # => /home/rye

# You can specify environment variables
rbox.add_env(:RYE, "Forty Creek")
rbox.env                           # => ['HOME=/home/rye', 'RYE=Forty Creek', ...]

# The commands method returns an Array of available commands:                        
puts rbox.commands.join(', ')      # => pwd, touch, echo, wc, ...

# When you're done you can disconnect explicitly. 
# (Although Rye does this automatically at exit.)
rbox.disconnect

EXAMPLE 2 – Disabling Safe-Mode

rbox_safe = Rye::Box.new('localhost')
rbox_wild = Rye::Box.new('localhost', :safe => false)

# Safe-mode is enabled by default. In safe-mode, all command 
# arguments are thoroughly escaped. This prevents access to
# environment variables and file globs (among other things).
p rbox_safe.echo('$HOME')                                    # => "$HOME"
p rbox_safe['/etc'].ls('host*')  rescue Rye::CommandError    # Doesn't exist
p rbox_safe.ls('-l | wc -l')     rescue Rye::CommandError    # => '|' is not a valid ls arg

# Here's the same commands with safe-mode disabled:
p rbox_wild.echo('$HOME')                   # => "/home/rye"
p rbox_wild['/etc'].ls('host*')             # => ["hostconfig", "hosts"]
p rbox_wild.ls('-l | wc -l')                # => 110
p rbox_wild.echo('$HOME > /tmp/rye-home')   # => 
p rbox_wild.cat('/tmp/rye-home')            # => "/home/rye"

EXAMPLE 3 – Custom Commands

rbox = Rye::Box.new('localhost')
rbox.add_keys('/private/key/path')   # Specify additional private keys

# There's currently no rye900 command
p rbox.commands.member?('rye9000')   # => false

# But we can add our own commands to the Rye::Cmd class. They 
# automatically become available to all Rye::Box objects.
module Rye::Cmd
  def rye9000(*args)
    run_command("ls", args)
  end
  def somescript(*args)
    run_command("/path/to/my/script", args)
  end
end

# We can now run rye9000 (with arguments)
p rbox.rye9000('-a')                 # => [".", "..", ".bashrc", ...]
p rbox.commands.member?('rye9000')   # => true

EXAMPLE 4 – Accessing Multiple Machines

rset = Rye::Set.new
rbox = Rye::Box.new

rset.add_keys('/private/key/path')     # For passwordless logins 
rset.add_boxes(rbox, 'localhost')      # Add boxes as hostnames or objects

# Calling methods on Rye::Set objects is very similar to calling them on
# Rye::Box objects. In fact, it's identical:
p rset.uptime        # => [[14:19:02 up 32 days, 19:35 ...], [14:19:02 up 30 days, 01:35]]
p rset['/etc'].ls    # => [['file1', 'file2', ...], ['life1', 'life2', ...]]

# Like Rye::Box, the response value is a Rye::Rap object containing the
# responses from each box. Each response is itself a Rye::Rap object.
unames = rset.uname
p unames                               # => [["Darwin"], ["Darwin"]]
puts unames.class                      # => Rye::Rap

# The Rye::Rap object also keeps a reference to the object that called the 
# command. In this case, it will keep a reference to Rye::Set:
puts unames.set.class                  # => Rye::Set
puts unames.set == rset                # => true
puts unames.size                       # => 2
puts unames.first                      # => Darwin
puts unames.first.class                # => Rye::Rap
puts unames.first.box.class            # => Rye::Box
puts unames.first.box == rbox          # => true

# Envrionment variables can be set the same way as with Rye::Box
rset.add_env(:RYE, "Forty Creek")
p rset.env.first.select { |env| env =~ /RYE/ }  # => ["RYE=Forty Creek"]

EXAMPLE 5 – ERROR HANDLING

rbox = Rye::Box.new('localhost', :safe => false)

# Rye follows the standard convention of taking exception to a non-zero 
# exit code by raising a Rye::CommandError. In this case, rye9000.test
# is not found by the ls command. 
begin
  rbox.ls('rye9000.test')
rescue Rye::CommandError => ex
  puts ex.exit_code                # => 1
  puts ex.stderr                   # => ls: rye.test: No such file or directory
end

# The Rye:Rap response objects also give you the STDOUT and STDERR
# content separately. Here we redirect STDOUT to STDERR, so this
# will return nothing:
puts rbox.uname('-a 1>&2').stdout    # =>

# It all went to STDERR:
puts rbox.uname('-a 1>&2').stderr    # => Darwin ryehost 9.6.0 ...

# There were no actual error so the exit code should be 0.
puts rbox.uname('-a 1>&2').exit_code # => 0

EXAMPLE 6 – rye

Rye comes with a command-line utility called rye.

# Prints the paths to your private keys
$ rye keys

# Prints the server host keys (suitable for ~/.ssh/known_hosts)
$ rye hostkey HOST1 HOST2

# Add your public keys to authorized_keys and authorized_keys2 
# on a remote machine
$ rye authorize HOST1 HOST2

More info:

$ rye -h
$ rye COMMAND -h
$ rye show-commands

About Safe-Mode

In safe-mode:

  • You can't use file globs. This means you can't do this: rbox.ls('*.rb'). ~ also doesn't work!

  • Command arguments cannot contain environment variables (however, environment variables are available to the commands you run). This means you can't do this: rbox.echo('$HOME').

  • Pipes and operators don't work: |, &&, >, <, ||, ~, etc…

  • Backticks don't work either: procs=`ps aux`

Why? In safe-mode, all command arguments are escaped which turns all arguments into their literal values.

Using a Ruby interface to execute shell commands is pretty awesome, particularly to run them on several machines simultaneously. That's a lot of power and it's potentially very dangerous. That's why Rye disables this stuff by default. There's probably a way to do it safely but it's not obvious yet (to me). If you have any ideas, I'd love to hear them!

Command Whitelist

Rye permits only a limited number of system commands to be run. This default whitelist is defined in Rye::Cmd but you can add your own commands as you please (see Example 3).

Dependencies

  • OpenSSL (The C library)

  • Ruby Gems:

    • net-ssh

    • net-scp

    • highline

    • drydock

Known Issues

This list will grow. If you find one let me know!

  • Rye doesn't read the ~/.ssh/config file yet

  • Highline 1.5 not working in Ruby 1.9 (password prompts hang)

  • Rye uses OpenSSL's ssh-agent (if it exists). Rye starts it up as a child process and shuts it down using at_exit. If you have code in an at_exit that rely's on Rye, make sure your code runs before Rye's at_exit block is called. For example, Drydock uses at_exit too which is why in bin/rye you can see that Drydock is called explicitly so that Rye's at_exit is executed after Drydock executes a command.

Thanks

More Info

Credits

  • Delano Mandelbaum (delano@solutious.com)

  • Escape, Copyright (C) 2006,2007 Tanaka Akira <akr@fsij.org>

License

See: LICENSE.txt

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