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|
---
-- Utility functions for libssh2.
--
-- Provides helper class for the libssh2 binding that abstracts away
-- details of running remote commands.
--
-- @copyright Same as Nmap--See https://nmap.org/book/man-legal.html
-- @class module
-- @name libssh2-utility
local stdnse = require "stdnse"
local table = require "table"
local libssh2 = stdnse.silent_require "libssh2"
SSHConnection = {}
---
-- Returns a new connection object.
--
-- @return A connection object.
function SSHConnection:new ()
local o = {}
setmetatable(o, self)
self.__index = self
return o
end
---
-- Sets up a connection with a server.
--
-- @param host A host to connect to.
-- @param port A port to connect to.
-- @return true on success or nil on failure
function SSHConnection:connect (host, port)
self.session = libssh2.session_open(host, port.number)
if self.session then
return true
end
end
---
-- Sets up a connection with a server. Call performed with pcall.
--
-- @param host A host to connect to.
-- @param port A port to connect to.
-- @return true on success or error message on failure
-- @return error code if error was triggered
function SSHConnection:connect_pcall (host, port)
local status, err
status, self.session, err = pcall(libssh2.session_open, host, port.number)
return status, err
end
---
-- Runs a shell command on the remote host.
--
-- @param cmd A command to run.
-- @return The command output.
function SSHConnection:run_remote (cmd)
if not (self.session and self.authenticated) then
return false
end
local channel = libssh2.open_channel(self.session)
libssh2.channel_exec(self.session, channel, cmd)
libssh2.channel_send_eof(self.session, channel)
local buff = {}
local data = ""
while not libssh2.channel_eof(channel) do
data = libssh2.channel_read(self.session, channel)
if data then
table.insert(buff, data)
end
end
return table.concat(buff)
end
---
-- Attempts to authenticate using provided credentials.
--
-- @param username A username to authenticate as.
-- @param password A password to authenticate as.
-- @return true on success or false on failure.
function SSHConnection:password_auth (username, password)
if not self.session then
return false
end
if libssh2.userauth_password(self.session, username, password) then
self.authenticated = true
return true
else
return false
end
end
---
-- Attempts to authenticate using provided private key.
--
-- @param username A username to authenticate as.
-- @param privatekey_file A path to a privatekey.
-- @param passphrase A passphrase for the privatekey.
-- @return true on success or false on failure.
function SSHConnection:publickey_auth (username, privatekey_file, passphrase)
if not self.session then
return false
end
if libssh2.userauth_publickey(self.session, username, privatekey_file, passphrase or "") then
self.authenticated = true
return true
else
return false
end
end
---
-- Closes connection.
function SSHConnection:disconnect ()
if self.session then
libssh2.session_close(self.session)
end
end
---
-- Sends ssh timeout
--
-- @param ssh_timeout Time in miliseconds before considering the situation an error.
function SSHConnection:set_timeout (ssh_timeout)
if self.session then
libssh2.set_timeout(self.session, ssh_timeout)
end
end
---
-- Attempt to retrieve a list of supported authentication methods
--
-- @param username A username to authenticate as.
-- @return A list with the authentication methods on success or false on failure.
function SSHConnection:list (username)
if not self.session then
return false
end
local status, methods = pcall(libssh2.userauth_list, self.session, username)
if status then
return methods
end
return false
end
---
-- Attempts to read public key file
--
-- @param publickey An SSH public key file.
-- @return true on success or false on error.
-- @return public key data on success or error code on error.
function SSHConnection:read_publickey (publickey)
local status, result = pcall(libssh2.read_publickey, publickey)
return status, result
end
---
-- Attempts authentication with public key
--
-- @param username A username to authenticate as.
-- @param key Base64 decrypted public key.
-- @return true if the public key can be used to authenticate as the user, false otherwise
-- @return Error message if an error occurs.
function SSHConnection:publickey_canauth (username, key)
local status, err
if self.session then
status, err = pcall(libssh2.publickey_canauth, self.session, username, key)
if status then
-- no error thrown; return the actual result
status = err
err = nil
end
else
status = false
err = "No session established"
end
return status, err
end
return _ENV
|
