1 files changed, 184 insertions, 0 deletions
diff --git a/nselib/libssh2-utility.lua b/nselib/libssh2-utility.lua
new file mode 100644
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+++ b/nselib/libssh2-utility.lua
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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