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Man Pages

Manual Reference Pages  -  NET::SSH2 (3)

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Net::SSH2 - Support for the SSH 2 protocol via libssh2.



  use Net::SSH2;

  my $ssh2 = Net::SSH2->new();

  $ssh2->connect( or die $!;

  if ($ssh2->auth_keyboard(fizban)) {
      my $chan = $ssh2->channel();

      my $sftp = $ssh2->sftp();
      my $fh = $sftp->open(/etc/passwd) or die;
      print $_ while <$fh>;


Net::SSH2 is a perl interface to the libssh2 (<>) library. It supports the SSH2 protocol (there is no support for SSH1) with all of the key exchanges, ciphers, and compression of libssh2.

Unless otherwise indicated, methods return a true value on success and false on failure; use the error method to get extended error information.

The typical order is to create the SSH2 object, set up the connection methods you want to use, call connect, authenticate with one of the auth methods, then create channels on the connection to perform commands.


Exports the following constant tags:
all All constants.
ssh constants:
trace Tracing constants for use with ->trace and ->new(trace => ...).
hash Key hash constants.
disconnect Disconnect type constants.
SFTP constants:



Create new SSH2 object.

To turn on tracing with a debug build of libssh2 use:

    my $ssh2 = Net::SSH2->new(trace => -1);

    banner ( text )

Set the SSH2 banner text sent to the remote host (prepends required SSH-2.0-).


In scalar context, returns libssh2 version/patch e.g. 0.18 or 0.18.0-20071110. In list context, returns that version plus the numeric version (major, minor, and patch, each encoded as 8 bits, e.g. 0x001200 for version 0.18) and the default banner text (e.g. SSH-2.0-libssh2_0.18.0-20071110).


Returns the last error code; returns false if no error. In list context, returns (code, error name, error string).

Note that the returned error value is only meaningful after some other method indicates an error by returning false.


Returns a reference to the underlying IO::Socket object (usually a derived class as IO::Socket::IP or IO::Socket::INET), or undef if not yet connected.


Calls libssh2_trace with supplied bitmask, to enable all tracing use:


You need a debug build of libssh2 with tracing support.

    timeout ( timeout_ms )

Enables a global timeout (in milliseconds) which will affect every action.

libssh2 version 1.2.9 or higher is required to use this method.

    method ( type [, values... ] )

Sets or returns a method preference; for get, pass in the type only; to set, pass in either a list of values or a comma-separated string. Values can only be queried after the session is connected.

The following methods can be set or queried:
KEX Key exchange method names. Supported values:
diffie-hellman-group1-sha1 Diffie-Hellman key exchange with SHA-1 as hash, and Oakley Group 2 (see RFC 2409).
diffie-hellman-group14-sha1 Diffie-Hellman key exchange with SHA-1 as hash, and Oakley Group 14 (see RFC 3526).
diffie-hellman-group-exchange-sha1 Diffie-Hellman key exchange with SHA-1 as hash, using a safe-prime/generator pair (chosen by server) of arbitrary strength (specified by client) (see IETF draft secsh-dh-group-exchange).
HOSTKEY Public key algorithms. Supported values:
ssh-dss Based on the Digital Signature Standard (FIPS-186-2).
ssh-rsa Based on PKCS#1 (RFC 3447).
CRYPT_CS Encryption algorithm from client to server. Supported algorithms:
aes256-cbc AES in CBC mode, with 256-bit key. Alias for aes256-cbc.
aes192-cbc AES in CBC mode, with 192-bit key.
aes128-cbc AES in CBC mode, with 128-bit key.
blowfish-cbc Blowfish in CBC mode.
arcfour ARCFOUR stream cipher.
cast128-cbc CAST-128 in CBC mode.
3des-cbc Three-key 3DES in CBC mode.
none No encryption.
CRYPT_SC Encryption algorithm from server to client. See CRYPT_CS for supported algorithms.
MAC_CS Message Authentication Code (MAC) algorithms from client to server. Supported values:
hmac-sha1 SHA-1 with 20-byte digest and key length.
hmac-sha1-96 SHA-1 with 20-byte key length and 12-byte digest length.
hmac-md5 MD5 with 16-byte digest and key length.
hmac-md5-96 MD5 with 16-byte key length and 12-byte digest length.
hmac-ripemd160 RIPEMD-160 algorithm with 20-byte digest length. Alias for hmac-ripemd160.
none No encryption.
MAC_SC Message Authentication Code (MAC) algorithms from server to client. See MAC_SC for supported algorithms.
COMP_CS Compression methods from client to server. Supported values:
zlib The zlib compression method as described in RFC 1950 and RFC 1951.
none No compression
COMP_SC Compression methods from server to client. See COMP_CS for supported compression methods.

    connect ( handle | host [, port [, Timeout => secs ] [, Compress => 1]] )

Accepts a handle over which to conduct the SSH 2 protocol. The handle may be:
an IO::* object
a glob reference
an integer file descriptor
a host name and port In order to handle IPv6 addresses the optional module IO::Socket::IP needs to be installed (otherwise the module will use the IPv4 only core module IO::Socket::INET to establish the connection).

    disconnect ( [description [, reason [, language]]] )

Send a clean disconnect message to the remote server. Default values are empty strings for description and language, and SSH_DISCONNECT_BY_APPLICATION for the reason.

    hostkey_hash ( hash type )

Returns a hash of the host key; note that the key is raw data and may contain nulls or control characters. The type may be:
MD5 (16 bytes)
SHA1 (20 bytes)
Note: in previous versions of the module this method was called hostkey.


Returns the public key of the remote host and its type which is one of LIBSSH2_HOSTKEY_TYPE_RSA, LIBSSH2_HOSTKEY_TYPE_DSS, or LIBSSH2_HOSTKEY_TYPE_UNKNOWN.

    auth_list ( [username] )

Get a list (or comma-separated string in scalar context) of authentication methods supported by the server; or returns undef. If undef is returned and auth_ok is true, the server accepted an unauthenticated session for the given username.


Returns true iff the session is authenticated.

    auth_password ( username [, password [, callback ]] )

Authenticate using a password (PasswordAuthentication must be enabled in sshd_config or equivalent for this to work.)

If the password has expired, if a callback code reference was given, it’s called as callback($self, $username) and should return a password. If no callback is provided, LIBSSH2_ERROR_PASSWORD_EXPIRED is returned.

    auth_password_interact ( username [, callback])

Prompts the user for the password interactively using Term::ReadKey.

    auth_publickey ( username, publickey_path, privatekey_path [, passphrase ] )

Note that public key and private key are names of files containing the keys!

Authenticate using keys and an optional passphrase.

When libssh2 is compiled using OpenSSL as the crypto backend, passing this method undef as the public key argument is acceptable (OpenSSH is able to extract the public key from the private one).

    auth_publickey_frommemory ( username, publickey_blob, privatekey_blob [, passphrase ] )

Authenticate using the given public/private key and an optional passphrase. The keys must be PEM encoded.

This method requires libssh2 1.6.0 or later compiled with the OpenSSL backend.

    auth_hostbased ( username, publickey, privatekey, hostname, [, local username [, passphrase ]] )

Host-based authentication using an optional passphrase. The local username defaults to be the same as the remote username.

    auth_keyboard ( username, password | callback )

Authenticate using keyboard-interactive. Takes either a password, or a callback code reference which is invoked as callback->(self, username, name, instruction, prompt...) (where each prompt is a hash with text and echo keys, signifying the prompt text and whether the user input should be echoed, respectively) which should return an array of responses.

If only a username is provided, the default callback will handle standard interactive responses; Term::ReadKey is required.

    auth_agent ( username )

Try to authenticate using ssh-agent. This requires libssh2 version 1.2.3 or later.

    auth ( ... )

This is a general, prioritizing authentication mechanism that can use any of the previous methods. You provide it some parameters and (optionally) a ranked list of methods you want considered (defaults to all). It will remove any unsupported methods or methods for which it doesn’t have parameters (e.g. if you don’t give it a public key, it can’t use publickey or hostkey), and try the rest, returning whichever one succeeded or a false value if they all failed. If a parameter is passed with an undef value, a default value will be supplied if possible.

The parameters are:
rank An optional ranked list of methods to try. The names should be the names of the Net::SSH2 auth methods, e.g. ’keyboard’ or ’publickey’, with the addition of ’keyboard-auto’ for automated ’keyboard-interactive’ and ’password-interact’ that prompts the user for the password interactively.
passphrase As in the methods, publickey and privatekey are filenames.
interact If this is set to a true value, interactive methods will be considered.
fallback If a password is given but authentication using it fails, the module will fall back to ask the user for another password if this parameter is set to a true value.
cb_keyboard auth_keyboard callback.
cb_password auth_password callback.
For historical reasons and in order to maintain backward compatibility with older versions of the module, when the password argument is given, it is also used as the passphrase (and a deprecation warning generated).

In order to avoid that behaviour the passphrase argument must be also passed (it could be undef). For instance:

  $ssh2->auth(username => $user,
              privatekey => $privatekey_path,
              publickey => $publickey_path,
              password => $password,
              passphrase => undef);

This work around will be removed in a not too distant future version of the module.

    flag (key, value)

Sets the given session flag.

The currently supported flag values are:
COMPRESS If set before the connection negotiation is performed, compression will be negotiated for this connection.

Compression can also be enabled passing the Compress option connect.

SIGPIPE if set, Net::SSH2/libssh2 will not attempt to block SIGPIPEs but will let them trigger from the underlying socket layer.

    keepalive_config(want_reply, interval)

Set how often keepalive messages should be sent.

want_reply indicates whether the keepalive messages should request a response from the server. interval is number of seconds that can pass without any I/O.


Send a keepalive message if needed.

On failure returns undef. On success returns how many seconds you can sleep after this call before you need to call it again.

Note that the underlying libssh2 function libssh2_keepalive_send can not recover from EAGAIN errors. If this method fails with such error, the SSH connection may become corrupted.

    channel ( [type, [window size, [packet size]]] )

Creates and returns a new channel object. The default type is session. See Net::SSH2::Channel.

    tcpip ( host, port [, shost, sport ] )

Creates a TCP connection from the remote host to the given host:port, returning a new channel.

The shost and sport arguments are merely informative and passed to the remote SSH server as the origin of the connection. They default to

Note that this method does <B>notB> open a new port on the local machine and forwards incoming connections to the remote side.

    listen ( port [, host [, bound port [, queue size ]]] )

Sets up a TCP listening port on the remote host. Host defaults to; if bound port is provided, it should be a scalar reference in which the bound port is returned. Queue size specifies the maximum number of queued connections allowed before the server refuses new connections.

Returns a new Net::SSH2::Listener object.

    scp_get ( remote [, local ] )

Retrieve a file with scp; local path defaults to basename of remote. local may be an IO object (e.g. IO::File, IO::Scalar).

    scp_put ( local [, remote ] )

Send a file with scp; remote path defaults to same as local. local may be an IO object instead of a filename (but it must have a valid stat method).


Return SecureFTP interface object (see Net::SSH2::SFTP).


Return public key interface object (see Net::SSH2::PublicKey).


Returns known hosts interface object (see Net::SSH2::KnownHosts).

    poll ( timeout, arrayref of hashes )

Pass in a timeout in milliseconds and an arrayref of hashes with the following keys:
handle May be a Net::SSH2::Channel or Net::SSH2::Listener object, integer file descriptor, or perl file handle.
events Requested events. Combination of LIBSSH2_POLLFD_* constants (with the POLL prefix stripped if present), or an arrayref of the names (’in’, ’hup’ etc.).
revents Returned events. Returns a hash with the (lowercased) names of the received events (’in’, ’hup’, etc.) as keys with true values, and a value key with the integer value.
Returns undef on error, or the number of active objects.


Get the blocked direction when a function returns LIBSSH2_ERROR_EAGAIN, returns LIBSSH2_SOCKET_BLOCK_INBOUND or LIBSSH2_SOCKET_BLOCK_OUTBOUND from the socket export group.

    debug ( state )

Class method (affects all Net::SSH2 objects). Pass 1 to enable, 0 to disable. Debug output is sent to stderr via warn.

    blocking ( flag )

Enable or disable blocking. Note that if blocking is disabled, methods that create channels may fail, e.g. channel, SFTP, scp_*.


Net::SSH2::Channel, Net::SSH2::Listener, Net::SSH2::SFTP, Net::SSH2::File, Net::SSH2::Dir.

LibSSH2 documentation at <>.

IETF Secure Shell (secsh) working group at <>.

Net::SSH::Any and Net::SFTP::Foreign integrate nicely with Net::SSH2.

Other Perl modules related to SSH you may find interesting: Net::OpenSSH, Net::SSH::Perl, Net::OpenSSH::Parallel, Net::OpenSSH::Compat.


Copyright (C) 2005 - 2010 by David B. Robins (

Copyright (C) 2010 - 2015 by Rafael Kitover (

Copyright (C) 2011 - 2015 by Salvador Fandinõ (

All rights reserved.

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.0 or, at your option, any later version of Perl 5 you may have available.

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