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https://github.com/sirthias/scala-ssh

Remote shell access via SSH for your Scala applications
https://github.com/sirthias/scala-ssh

Last synced: 30 days ago
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Remote shell access via SSH for your Scala applications

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README 

        
**scala-ssh** is a Scala_ library providing remote shell access via SSH.

It builds on SSHJ_ to provide the following features:



* Remote execution of one or more shell commands

* Access to ``stdin``, ``stdout``, ``stderr`` and exitcode of remote shell commands

* Authentication via password, public key or agent

* Host key verification via ``known_hosts`` file or explicit fingerprint

* Convenient configuration of remote host properties via config file, resource or directly in code

* Scala-idiomatic API



.. image:: https://img.shields.io/maven-central/v/com.decodified/scala-ssh_2.12.svg

   :target: https://maven-badges.herokuapp.com/maven-central/com.decodified/scala-ssh_2.12

   :alt: The latest scala-ssh artifacts on Maven Central



.. image:: https://travis-ci.org/sirthias/scala-ssh.svg?branch=master

   :target: https://travis-ci.org/sirthias/scala-ssh



.. image:: https://img.shields.io/badge/uses-badges-ff69b4.svg

   :target: http://shields.io/

   :alt: uses badges



*****



Installation

------------



The latest release is **0.11.1** and is built against Scala 2.12, 2.13 and 3.

It is available from Maven Central. If you use SBT_ you can pull in the *scala-ssh* artifacts with::



    libraryDependencies += "com.decodified" %% "scala-ssh" % "0.11.1"



SSHJ_ uses SLF4J_ for logging, so you might want to also add logback_ to your dependencies::



    libraryDependencies += "ch.qos.logback" % "logback-classic" % "1.2.3"



Usage

-----



The highest-level API element provided by *scala-ssh* is the ``SSH`` object. You use it like this::



    SSH("example.com") { client =>

      for {

        result <- client.exec("ls -a")

      } println("Result:\n" + result.stdOutAsString())

    }



This establishes an SSH connection to host ``example.com`` and gives you an ``SshClient`` instance that you can use

to execute one or more commands on the host.

``SSH.apply`` has a second (optional) parameter of type ``HostConfigProvider``, which is essentially a function

returning a ``HostConfig`` instance for a given hostname. A ``HostConfig`` looks like this::



    case class HostConfig(

      login: SshLogin,

      hostName: String = "",

      port: Int = 22,

      connectTimeout: Option[Int] = None,

      connectionTimeout: Option[Int] = None,

      commandTimeout: Option[Int] = None,

      enableCompression: Boolean = false,

      hostKeyVerifier: HostKeyVerifier = ...,

      sshjConfig: Config = ...

    )



It provides all the details required for properly establishing an SSH connection.

If you don't provide an explicit ``HostConfigProvider`` the default one will be used. For every hostname you pass to the

``SSH.apply`` method this default ``HostConfigProvider`` expects a file ``~/.scala-ssh/{hostname}``, which contains the

properties of a ``HostConfig`` in a simple config file format (see below for details). The ``HostResourceConfig`` object

gives you alternative ``HostConfigProvider`` implementations that read the host config from classpath resources.



If the file ``~/.scala-ssh/{hostname}`` (or the classpath resource ``{hostname}``) doesn't exist *scala-ssh* looks for

more general files (or resources) in the following way:



1. As long as the first segment of the host name (up to the first ``.``) contains one or more digits replace the

   rightmost of these with ``X`` and look for a respectively named file or resource. Repeat until no digits left.

2. Drop all characters up to (and including) the first ``.`` from the host name and look for a respectively named file

   or resource.

3. Repeat from 1. as long as there are characters left.



This means that for a host with name ``node42.tier1.example.com`` the following locations (either under

``~/.scala-ssh/`` or the classpath, depending on the ``HostConfigProvider``) are tried:



1. ``node42.tier1.example.com``

2. ``node4X.tier1.example.com``

3. ``nodeXX.tier1.example.com``

4. ``tier1.example.com``

5. ``tierX.example.com``

6. ``example.com``

7. ``com``



Host Config File Format

-----------------------



A host config file is a UTF8-encoded text file containing ``key = value`` pairs, one per line.

Blank lines and lines starting with a ``#`` character are ignored. This is an example file::



    # simple password-based config

    login-type = password

    username = bob

    password = 123

    command-timeout = 5000

    enable-compression = yes



These key are defined:



login-type

  required, can be either ``password`` or ``keyfile``



host-name

  optional, if not given the name of the config file is assumed to be the hostname



port

  optional, the default value is ``22``



username

  required



password

  required for login-type ``password``, ignored otherwise



keyfile

  optionally specifies the location of the user keyfile to use with login-type ``keyfile``,

  if not given the default files ``~/.ssh/id_ed25519``, ``~/.ssh/id_rsa`` and ``~/.ssh/id_dsa`` are tried,

  if the filename starts with a ``+`` the file is searched in addition to the default

  locations, if the filename starts with ``classpath:`` it is interpreted as the name of a classpath resource holding

  the private key,

  ignored for login-type ``password``



passphrase

  optionally specifies the passphrase for the keyfile, if not given the keyfile is assumed to be unencrypted,

  ignored for login-type ``password``



connect-timeout

  optionally specifies the number of milli-seconds that a connection request has to succeed in before triggering a

  timeout error, default value is 'no timeout'



connection-timeout

  optionally specifies the number of milli-seconds that an idle connection is held open before being closed due due to

  idleness, default value is 'no timeout'



command-timeout

  optionally specifies the number of milli-seconds that a pending response to an issued command is waited for before

  triggering a timeout error, default value is 'no timeout'



enable-compression

  optionally adds ``zlib`` compression to preferred compression algorithms, there is no guarantee that it will be

  successfully negotiatied, requires ``jzlib`` on the classpath (see 'installation' chapter) above, default is 'no'



fingerprint

  optionally specifies the fingerprint of the public host key to verify in standard SSH format

  (e.g. ``4b:69:6c:72:6f:79:20:77:61:73:20:68:65:72:65:21``), if not given the standard ``~/.ssh/known_hosts`` or

  ``~/.ssh/known_hosts2`` files will be searched for a matching entry, fingerprint verification can be entirely disabled

  by setting ``fingerprint = any``



Troubleshooting

--------------



Java Cryptography Extension Policy Files

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~



To use this library it might be necessary that you install the Java Cryptography Extension Policy

Files from the JDK additional downloads section. Make sure they are installed, especially if you

encounter exceptions like this:



    net.schmizz.sshj.common.SSHRuntimeException: null

            at net.schmizz.sshj.common.Buffer.readPublicKey(Buffer.java:432) ~[sshj-0.12.0.jar:na]

            at net.schmizz.sshj.transport.kex.AbstractDHG.next(AbstractDHG.java:108) ~[sshj-0.12.0.jar:na]

            at net.schmizz.sshj.transport.KeyExchanger.handle(KeyExchanger.java:352) ~[sshj-0.12.0.jar:na]

            at net.schmizz.sshj.transport.TransportImpl.handle(TransportImpl.java:487) ~[sshj-0.12.0.jar:na]

            at net.schmizz.sshj.transport.Decoder.decode(Decoder.java:107) ~[sshj-0.12.0.jar:na]

            at net.schmizz.sshj.transport.Decoder.received(Decoder.java:175) ~[sshj-0.12.0.jar:na]

            at net.schmizz.sshj.transport.Reader.run(Reader.java:61) ~[sshj-0.12.0.jar:na]

    Caused by: java.security.GeneralSecurityException: java.security.spec.InvalidKeySpecException: key spec not recognised

            at net.schmizz.sshj.common.KeyType$3.readPubKeyFromBuffer(KeyType.java:146) ~[sshj-0.12.0.jar:na]

            at net.schmizz.sshj.common.Buffer.readPublicKey(Buffer.java:430) ~[sshj-0.12.0.jar:na]

            ... 6 common frames omitted

    Caused by: java.security.spec.InvalidKeySpecException: key spec not recognised

            at org.bouncycastle.jcajce.provider.asymmetric.util.BaseKeyFactorySpi.engineGeneratePublic(Unknown Source) ~[bcprov-jdk15on-1.52.jar:1.52.0]

            at org.bouncycastle.jcajce.provider.asymmetric.ec.KeyFactorySpi.engineGeneratePublic(Unknown Source) ~[bcprov-jdk15on-1.52.jar:1.52.0]

            at java.security.KeyFactory.generatePublic(KeyFactory.java:334) ~[na:1.8.0_05]

            at net.schmizz.sshj.common.KeyType$3.readPubKeyFromBuffer(KeyType.java:144) ~[sshj-0.12.0.jar:na]

            ... 7 common frames omitted



Running tests locally

---------------------



Some of the tests needs a running SSH daemon and expects particular structure of `~/.scala-ssh`. In case you want to run

those tests locally there is prepared structure to run dockerized sbt and sshd. Running dockerized structure should

work just by itself:



```

scripts/local/dockerized-sbt.sh

# and then in sbt:

test

```



Having sbt as a separate step make it easier to run changes iteratively in dockerized sbt.



License

-------



*scala-ssh* is licensed under `APL 2.0`_.



Patch Policy

------------



Feedback and contributions to the project, no matter what kind, are always very welcome.

However, patches can only be accepted from their original author.

Along with any patches, please state that the patch is your original work and that you license the work to the

*scala-ssh* project under the project’s open source license.



.. _Scala: http://www.scala-lang.org/

.. _sshj: https://github.com/hierynomus/sshj

.. _SBT: https://github.com/harrah/xsbt/wiki

.. _SLF4J: http://www.slf4j.org/

.. _logback: http://logback.qos.ch/

.. _APL 2.0: http://www.apache.org/licenses/LICENSE-2.0