Net::SSH2(3pm) User Contributed Perl Documentation Net::SSH2(3pm)NAMENet::SSH2 - Support for the SSH 2 protocol via libssh2.
SYNOPSIS
use Net::SSH2;
my $ssh2 = Net::SSH2->new();
$ssh2->connect('example.com') or $ssh2->die_with_error;
$ssh->check_hostkey('ask') or $ssh2->die_with_error;
if ($ssh2->auth_keyboard('fizban')) {
my $chan = $ssh2->channel();
$chan->exec('program');
my $sftp = $ssh2->sftp();
my $fh = $sftp->open('/etc/passwd') or $sftp->die_with_error;
print $_ while <$fh>;
}
DESCRIPTIONNet::SSH2 is a Perl interface to the libssh2 (<http://www.libssh2.org>)
library. It supports the SSH2 protocol (there is no support for SSH1)
with all of the key exchanges, ciphers, and compression of libssh2.
Even if the module can be compiled and linked against very old versions
of the library, nothing below 1.5.0 should really be used (older
versions were quite buggy and unreliable) and version 1.7.0 or later is
recommended.
Error handling
Unless otherwise indicated, methods return a true value on success and
"undef" on failure; use the "error" method to get extended error
information.
Important: methods in Net::SSH2 not backed by libssh2 functions (i.e.
"check_hostkey" or SCP related methods) require libssh2 1.7.0 or later
in order to set the error state. That means that after any of those
methods fails, "error" would not return the real code but just some
bogus result when an older version of the library is used.
Typical usage
The typical usage order is as follows:
1. Create the SSH2 object calling "new".
2. Configure the session if required. For instance, enabling
compression or picking some specific encryption methods.
3. Establish the SSH connection calling the method "connect".
4. Check the remote host public key calling "check_hostkey".
5. Authenticate calling the required authentication methods.
6. Call "channel" and related methods to create new bidirectional
communication channels over the SSH connection.
7. Close the connection letting the Net::SSH2 object go out of scope
or calling "disconnect" explicitly.
CONSTANTS
All the constants defined in libssh2 can be imported from Net::SSH2.
For instance:
use Net::SSH2 qw(LIBSSH2_CHANNEL_EXTENDED_DATA_MERGE
LIBSSH2_CHANNEL_FLUSH_ALL
LIBSSH2_HOSTKEY_POLICY_ASK);
Though note that most methods accept the uncommon part of the constant
name as a string. For instance the following two method calls are
equivalent:
$channel->ext_data(LIBSSH2_CHANNEL_EXTENDED_DATA_MERGE);
$channel->ext_data('merge');
Tags can be used to import the following constant subsets:
callback channel error socket trace hash method
disconnect policy fx fxf sftp
The tag "all" can also be used to import all of them.
METHODS
new ( %options )
Create new Net::SSH2 object representing a SSH session.
The accepted options are as follows:
timeout
Sets the default timeout in milliseconds. See "timeout".
trace
Sets tracing. See "trace".
Example:
my $ssh2 = Net::SSH2->new(trace => -1);
Note that tracing requires a version of libssh2 compiled with
debugging support.
debug
Enable debugging. See "debug".
compress
Sets flag "LIBSSH2_FLAG_COMPRESS". See "flag".
sigpipe
Sets flag "LIBSSH2_FLAG_SIGPIPE". See "flag".
banner ( text )
Set the SSH2 banner text sent to the remote host (prepends required
"SSH-2.0-").
version
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").
error
Returns the last error code. 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.
die_with_error ( [message] )
Calls "die" with the given message and the error information from the
object appended.
For instance:
$ssh2->connect("ajhkfhdklfjhklsjhd", 22)
or $ssh2->die_with_error;
# dies as:
# Unable to connect to remote host: Invalid argument (-1 LIBSSH2_ERROR_SOCKET_NONE)
sock
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.
trace
Calls "libssh2_trace" with supplied bitmask. In order to enable all
tracing pass "-1" as follows:
$ssh2->trace(-1);
A version of libssh2 compiled with tracing support is required.
timeout ( timeout_ms )
Enables a global timeout (in milliseconds) which will affect every
action (requires libssh2 1.2.9 or later).
By default, or if you set the timeout to zero, Net::SSH2 has no
timeout.
Note that timeout errors may leave the SSH connection in an
inconsistent state and further operations may fail or behave
incorrectly. Actually, some methods are able to recover after a timeout
error and others are not.
Don't hesitate to report any issue you encounter related to this so
that it can be fixed or at least, documented!
method ( type [, values... ] )
Sets or gets 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:
LIBSSH2_METHOD_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).
LIBSSH2_METHOD_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).
LIBSSH2_METHOD_CRYPT_CS
Encryption algorithm from client to server. Supported algorithms:
aes256-cbc
AES in CBC mode, with 256-bit key.
rijndael-cbc@lysator.liu.se
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.
LIBSSH2_METHOD_CRYPT_SC
Encryption algorithm from server to client. See the
"LIBSSH2_METHOD_CRYPT_CS" entry above for supported algorithms.
LIBSSH2_METHOD_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.
hmac-ripemd160@openssh.com
Alias for hmac-ripemd160.
none
No encryption.
LIBSSH2_METHOD_MAC_SC
Message Authentication Code (MAC) algorithms from server to client.
See LIBSSH2_METHOD_MAC_CS for supported algorithms.
LIBSSH2_METHOD_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
LIBSSH2_METHOD_COMP_SC
Compression methods from server to client. See
LIBSSH2_METHOD_COMP_CS for supported compression methods.
connect ( handle | host [, port])
The argument combinations accepted are as follows:
a glob or "IO::*" object reference
Note that tied file handles are not acceptable. The underlying
libssh2 requires real file handles.
host [, port]
In order to handle IPv6 addresses the optional module
IO::Socket::IP is required.
The port number defaults to 22.
This method used to accept a "Timeout" argument. That feature has been
replaced by the constructor "timeout" option but note that it takes
milliseconds instead of seconds!
disconnect ( [description [, reason [, language]]] )
Sends 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.
hostname
The name of the remote host given at connect time or retrieved from the
TCP layer.
port
The port number of the remote SSH server.
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 as follows:
LIBSSH2_HOSTKEY_HASH_MD5
MD5 hash, 16 bytes long (requires libssh2 compiled with MD5
support).
LIBSSH2_HOSTKEY_HASH_SHA1
SHA1 hash, 20 bytes long.
Note: in previous versions of the module this method was called
"hostkey".
remote_hostkey
Returns the public key from the remote host and its type which is one
of "LIBSSH2_HOSTKEY_TYPE_RSA", "LIBSSH2_HOSTKEY_TYPE_DSS", or
"LIBSSH2_HOSTKEY_TYPE_UNKNOWN".
check_hostkey( [policy, [known_hosts_path [, comment] ] ] )
Looks for the remote host key inside the given known host file
(defaults to "~/.ssh/known_hosts").
On success, this method returns the result of the call done under the
hood to "Net::SSH2::KnownHost::check" (i.e.
"LIBSSH2_KNOWNHOST_CHECK_MATCH", "LIBSSH2_KNOWNHOST_CHECK_FAILURE",
"LIBSSH2_KNOWNHOST_CHECK_NOTFOUND" or
"LIBSSH2_KNOWNHOST_CHECK_MISMATCH").
On failure it returns "undef".
The accepted policies are as follows:
LIBSSH2_HOSTKEY_POLICY_STRICT
Only host keys already present in the known hosts file are
accepted.
This is the default policy.
LIBSSH2_HOSTKEY_POLICY_ASK
If the host key is not present in the known hosts file, the user is
asked if it should be accepted or not.
If accepted, the key is added to the known host file with the given
comment.
LIBSSH2_HOSTKEY_POLICY_TOFU
Trust On First Use: if the host key is not present in the known
hosts file, it is added there and accepted.
LIBSSH2_HOSTKEY_POLICY_ADVISORY
The key is always accepted, but it is never saved into the known
host file.
callback
If a reference to a subroutine is given, it is called when the key
is not present in the known hosts file or a different key is found.
The arguments passed to the callback are the session object, the
matching error ("LIBSSH2_KNOWNHOST_CHECK_FAILURE",
"LIBSSH2_KNOWNHOST_CHECK_NOTFOUND" or
"LIBSSH2_KNOWNHOST_CHECK_MISMATCH") and the comment.
auth_list ( [username] )
Returns the authentication methods accepted by the server. In scalar
context the methods are returned as a comma separated string.
When the server accepted an unauthenticated session for the given
username, this method returns "undef" but "auth_ok" returns true.
auth_ok
Returns true when the session is authenticated.
auth_password ( username [, password [, callback ]] )
Authenticates using a password.
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 (requires
Term::ReadKey).
auth_publickey ( username, publickey_path, privatekey_path [, passphrase ]
)
Authenticate using the given private key 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 (OpenSSL
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 (requires libssh2 1.6.0 or
later 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 (requires Term::ReadKey)
auth_agent ( username )
Try to authenticate using an SSH agent (requires libssh2 1.2.3).
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 "undef" 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" which prompts the
user for the password interactively.
username
password
publickey
privatekey
"privatekey" and "publickey" are file paths.
passphrase
hostname
local_username
interact
If this option is set to a true value, interactive methods will be
enabled.
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:
LIBSSH2_FLAG_COMPRESS
If set before the connection negotiation is performed, compression
will be negotiated for this connection.
Compression can also be enabled passing option "compress" to the
constructor new.
LIBSSH2_FLAG_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.
keepalive_send
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.
The usage of this function is discouraged.
channel ( [type, [window size, [packet size]]] )
Creates and returns a new channel object. See Net::SSH2::Channel.
Type, if given, must be "session" (a reminiscence of an old, more
generic, but never working wrapping).
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
127.0.0.1:22.
Note that this method does not 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
0.0.0.0; 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_path [, local_path ] )
Retrieve a file with SCP. Local path defaults to basename of remote.
Alternatively, "local_path" may be an already open file handle or an
IO::Handle object (e.g. IO::File, IO::Scalar).
scp_put ( local_path [, remote_path ] )
Send a file with SCP. Remote path defaults to same as local.
Alternatively, "local_path" may be an already open file handle or a
reference to a IO::Handle object (it must have a valid stat method).
sftp
Return SecureFTP interface object (see Net::SSH2::SFTP).
Note that SFTP support in libssh2 is pretty rudimentary. You should
consider using Net::SFTP::Foreign with the Net::SSH2 backend
Net::SFTP::Foreign::Backend::Net_SSH2 instead.
public_key
Return public key interface object (see Net::SSH2::PublicKey).
known_hosts
Returns known hosts interface object (see Net::SSH2::KnownHosts).
poll ( timeout, arrayref of hashes )
Deprecated: the poll functionality in libssh2 is deprecated and its
usage disregarded. Session methods "sock" and "block_directions" can be
used instead to integrate Net::SSH2 inside an external event loop.
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.
block_directions
Get the blocked direction after some method returns
"LIBSSH2_ERROR_EAGAIN".
Returns "LIBSSH2_SESSION_BLOCK_INBOUND" or/and
"LIBSSH2_SESSION_BLOCK_OUTBOUND".
debug ( state )
Class method (affects all Net::SSH2 objects).
Pass 1 to enable, 0 to disable. Debug output is sent to "STDERR".
blocking ( flag )
Enable or disable blocking.
A good number of the methods in Net::SSH2/libssh2 can not work in non-
blocking mode. Some of them may just forcibly enable blocking during
its execution. A few may even corrupt the SSH session or crash the
program.
The ones that can be safely called are "read" and, with some caveats,
"write". See "write" in Net::SSH2::Channel.
Don't hesitate to report any bug you found in that area!
SEE ALSO
Net::SSH2::Channel, Net::SSH2::Listener, Net::SSH2::SFTP,
Net::SSH2::File, Net::SSH2::Dir.
LibSSH2 documentation at <http://www.libssh2.org>.
IETF Secure Shell (secsh) working group at
<http://www.ietf.org/html.charters/secsh-charter.html>.
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 AND LICENSE
Copyright (C) 2005 - 2010 by David B. Robins (dbrobins@cpan.org).
Copyright (C) 2010 - 2016 by Rafael Kitover (rkitover@cpan.org).
Copyright (C) 2011 - 2017 by Salvador Fandiño (salva@cpan.org).
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.
perl v5.26.1 2017-12-14 Net::SSH2(3pm)
