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nftables.py
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#!/usr/bin/python # Copyright(C) 2018 Phil Sutter <phil@nwl.cc> # This program is free software; you can redistribute it and/or modify # it under the terms of the GNU General Public License as published by # the Free Software Foundation, version 2 of the License. # # This program is distributed in the hope that it will be useful, # but WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the # GNU General Public License for more details. # # You should have received a copy of the GNU General Public License # along with this program; if not, write to the Free Software # Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. import json from ctypes import * import sys import os NFTABLES_VERSION = "0.1" class SchemaValidator: """Libnftables JSON validator using jsonschema""" def __init__(self): schema_path = os.path.join(os.path.dirname(__file__), "schema.json") with open(schema_path, 'r') as schema_file: self.schema = json.load(schema_file) import jsonschema self.jsonschema = jsonschema def validate(self, json): self.jsonschema.validate(instance=json, schema=self.schema) class Nftables: """A class representing libnftables interface""" input_flags = { "no-dns": 0x1, "json": 0x2, } debug_flags = { "scanner": 0x1, "parser": 0x2, "eval": 0x4, "netlink": 0x8, "mnl": 0x10, "proto-ctx": 0x20, "segtree": 0x40, } output_flags = { "reversedns": (1 << 0), "service": (1 << 1), "stateless": (1 << 2), "handle": (1 << 3), "json": (1 << 4), "echo": (1 << 5), "guid": (1 << 6), "numeric_proto": (1 << 7), "numeric_prio": (1 << 8), "numeric_symbol": (1 << 9), "numeric_time": (1 << 10), "terse": (1 << 11), } validator = None def __init__(self, sofile="libnftables.so.1"): """Instantiate a new Nftables class object. Accepts a shared object file to open, by default standard search path is searched for a file named 'libnftables.so'. After loading the library using ctypes module, a new nftables context is requested from the library and buffering of output and error streams is turned on. """ self.__ctx = None lib = cdll.LoadLibrary(sofile) ### API function definitions self.nft_ctx_new = lib.nft_ctx_new self.nft_ctx_new.restype = c_void_p self.nft_ctx_new.argtypes = [c_int] self.nft_ctx_input_get_flags = lib.nft_ctx_input_get_flags self.nft_ctx_input_get_flags.restype = c_uint self.nft_ctx_input_get_flags.argtypes = [c_void_p] self.nft_ctx_input_set_flags = lib.nft_ctx_input_set_flags self.nft_ctx_input_set_flags.restype = c_uint self.nft_ctx_input_set_flags.argtypes = [c_void_p, c_uint] self.nft_ctx_output_get_flags = lib.nft_ctx_output_get_flags self.nft_ctx_output_get_flags.restype = c_uint self.nft_ctx_output_get_flags.argtypes = [c_void_p] self.nft_ctx_output_set_flags = lib.nft_ctx_output_set_flags self.nft_ctx_output_set_flags.argtypes = [c_void_p, c_uint] self.nft_ctx_output_get_debug = lib.nft_ctx_output_get_debug self.nft_ctx_output_get_debug.restype = c_int self.nft_ctx_output_get_debug.argtypes = [c_void_p] self.nft_ctx_output_set_debug = lib.nft_ctx_output_set_debug self.nft_ctx_output_set_debug.argtypes = [c_void_p, c_int] self.nft_ctx_buffer_output = lib.nft_ctx_buffer_output self.nft_ctx_buffer_output.restype = c_int self.nft_ctx_buffer_output.argtypes = [c_void_p] self.nft_ctx_get_output_buffer = lib.nft_ctx_get_output_buffer self.nft_ctx_get_output_buffer.restype = c_char_p self.nft_ctx_get_output_buffer.argtypes = [c_void_p] self.nft_ctx_buffer_error = lib.nft_ctx_buffer_error self.nft_ctx_buffer_error.restype = c_int self.nft_ctx_buffer_error.argtypes = [c_void_p] self.nft_ctx_get_error_buffer = lib.nft_ctx_get_error_buffer self.nft_ctx_get_error_buffer.restype = c_char_p self.nft_ctx_get_error_buffer.argtypes = [c_void_p] self.nft_run_cmd_from_buffer = lib.nft_run_cmd_from_buffer self.nft_run_cmd_from_buffer.restype = c_int self.nft_run_cmd_from_buffer.argtypes = [c_void_p, c_char_p] self.nft_run_cmd_from_filename = lib.nft_run_cmd_from_filename self.nft_run_cmd_from_filename.restype = c_int self.nft_run_cmd_from_filename.argtypes = [c_void_p, c_char_p] self.nft_ctx_add_include_path = lib.nft_ctx_add_include_path self.nft_ctx_add_include_path.restype = c_int self.nft_ctx_add_include_path.argtypes = [c_void_p, c_char_p] self.nft_ctx_clear_include_paths = lib.nft_ctx_clear_include_paths self.nft_ctx_clear_include_paths.argtypes = [c_void_p] self.nft_ctx_get_dry_run = lib.nft_ctx_get_dry_run self.nft_ctx_get_dry_run.restype = c_bool self.nft_ctx_get_dry_run.argtypes = [c_void_p] self.nft_ctx_set_dry_run = lib.nft_ctx_set_dry_run self.nft_ctx_set_dry_run.argtypes = [c_void_p, c_bool] self.nft_ctx_add_var = lib.nft_ctx_add_var self.nft_ctx_add_var.restype = c_int self.nft_ctx_add_var.argtypes = [c_void_p, c_char_p] self.nft_ctx_clear_vars = lib.nft_ctx_clear_vars self.nft_ctx_clear_vars.argtypes = [c_void_p] self.nft_ctx_free = lib.nft_ctx_free lib.nft_ctx_free.argtypes = [c_void_p] # initialize libnftables context self.__ctx = self.nft_ctx_new(0) self.nft_ctx_buffer_output(self.__ctx) self.nft_ctx_buffer_error(self.__ctx) def __del__(self): if self.__ctx is not None: self.nft_ctx_free(self.__ctx) self.__ctx = None def _flags_from_numeric(self, flags_dict, val): names = [] for n, v in flags_dict.items(): if val & v: names.append(n) val &= ~v if val: names.append(val) return names def _flags_to_numeric(self, flags_dict, values): if isinstance(values, (str, int)): values = (values,) val = 0 for v in values: if isinstance(v, str): v = flags_dict.get(v) if v is None: raise ValueError("Invalid argument") elif isinstance(v, int): if v < 0 or v > 0xFFFFFFFF: raise ValueError("Invalid argument") else: raise TypeError("Not a valid flag") val |= v return val def get_input_flags(self): """Get currently active input flags. Returns a set of flag names. See set_input_flags() for details. """ val = self.nft_ctx_input_get_flags(self.__ctx) return self._flags_from_numeric(self.input_flags, val) def set_input_flags(self, values): """Set input flags. Resets all input flags to values. Accepts either a single flag or a list of flags. Each flag might be given either as string or integer value as shown in the following table: Name | Value (hex) ----------------------- "no-dns" | 0x1 "json" | 0x2 "no-dns" disables blocking address lookup. "json" enables JSON mode for input. Returns a set of previously active input flags, as returned by get_input_flags() method. """ val = self._flags_to_numeric(self.input_flags, values) old = self.nft_ctx_input_set_flags(self.__ctx, val) return self._flags_from_numeric(self.input_flags, old) def __get_output_flag(self, name): flag = self.output_flags[name] return (self.nft_ctx_output_get_flags(self.__ctx) & flag) != 0 def __set_output_flag(self, name, val): flag = self.output_flags[name] flags = self.nft_ctx_output_get_flags(self.__ctx) if val: new_flags = flags | flag else: new_flags = flags & ~flag self.nft_ctx_output_set_flags(self.__ctx, new_flags) return (flags & flag) != 0 def get_reversedns_output(self): """Get the current state of reverse DNS output. Returns a boolean indicating whether reverse DNS lookups are performed for IP addresses in output. """ return self.__get_output_flag("reversedns") def set_reversedns_output(self, val): """Enable or disable reverse DNS output. Accepts a boolean turning reverse DNS lookups in output on or off. Returns the previous value. """ return self.__set_output_flag("reversedns", val) def get_service_output(self): """Get the current state of service name output. Returns a boolean indicating whether service names are used for port numbers in output or not. """ return self.__get_output_flag("service") def set_service_output(self, val): """Enable or disable service name output. Accepts a boolean turning service names for port numbers in output on or off. Returns the previous value. """ return self.__set_output_flag("service", val) def get_stateless_output(self): """Get the current state of stateless output. Returns a boolean indicating whether stateless output is active or not. """ return self.__get_output_flag("stateless") def set_stateless_output(self, val): """Enable or disable stateless output. Accepts a boolean turning stateless output either on or off. Returns the previous value. """ return self.__set_output_flag("stateless", val) def get_handle_output(self): """Get the current state of handle output. Returns a boolean indicating whether handle output is active or not. """ return self.__get_output_flag("handle") def set_handle_output(self, val): """Enable or disable handle output. Accepts a boolean turning handle output on or off. Returns the previous value. """ return self.__set_output_flag("handle", val) def get_json_output(self): """Get the current state of JSON output. Returns a boolean indicating whether JSON output is active or not. """ return self.__get_output_flag("json") def set_json_output(self, val): """Enable or disable JSON output. Accepts a boolean turning JSON output either on or off. Returns the previous value. """ return self.__set_output_flag("json", val) def get_echo_output(self): """Get the current state of echo output. Returns a boolean indicating whether echo output is active or not. """ return self.__get_output_flag("echo") def set_echo_output(self, val): """Enable or disable echo output. Accepts a boolean turning echo output on or off. Returns the previous value. """ return self.__set_output_flag("echo", val) def get_guid_output(self): """Get the current state of GID/UID output. Returns a boolean indicating whether names for group/user IDs are used in output or not. """ return self.__get_output_flag("guid") def set_guid_output(self, val): """Enable or disable GID/UID output. Accepts a boolean turning names for group/user IDs on or off. Returns the previous value. """ return self.__set_output_flag("guid", val) def get_numeric_proto_output(self): """Get current status of numeric protocol output flag. Returns a boolean value indicating the status. """ return self.__get_output_flag("numeric_proto") def set_numeric_proto_output(self, val): """Set numeric protocol output flag. Accepts a boolean turning numeric protocol output either on or off. Returns the previous value. """ return self.__set_output_flag("numeric_proto", val) def get_numeric_prio_output(self): """Get current status of numeric chain priority output flag. Returns a boolean value indicating the status. """ return self.__get_output_flag("numeric_prio") def set_numeric_prio_output(self, val): """Set numeric chain priority output flag. Accepts a boolean turning numeric chain priority output either on or off. Returns the previous value. """ return self.__set_output_flag("numeric_prio", val) def get_numeric_symbol_output(self): """Get current status of numeric symbols output flag. Returns a boolean value indicating the status. """ return self.__get_output_flag("numeric_symbol") def set_numeric_symbol_output(self, val): """Set numeric symbols output flag. Accepts a boolean turning numeric representation of symbolic constants in output either on or off. Returns the previous value. """ return self.__set_output_flag("numeric_symbol", val) def get_numeric_time_output(self): """Get current status of numeric times output flag. Returns a boolean value indicating the status. """ return self.__get_output_flag("numeric_time") def set_numeric_time_output(self, val): """Set numeric times output flag. Accepts a boolean turning numeric representation of time values in output either on or off. Returns the previous value. """ return self.__set_output_flag("numeric_time", val) def get_terse_output(self): """Get the current state of terse output. Returns a boolean indicating whether terse output is active or not. """ return self.__get_output_flag("terse") def set_terse_output(self, val): """Enable or disable terse output. Accepts a boolean turning terse output either on or off. Returns the previous value. """ return self.__set_output_flag("terse", val) def get_debug(self): """Get currently active debug flags. Returns a set of flag names. See set_debug() for details. """ val = self.nft_ctx_output_get_debug(self.__ctx) return self._flags_from_numeric(self.debug_flags, val) def set_debug(self, values): """Set debug output flags. Accepts either a single flag or a set of flags. Each flag might be given either as string or integer value as shown in the following table: Name | Value (hex) ----------------------- scanner | 0x1 parser | 0x2 eval | 0x4 netlink | 0x8 mnl | 0x10 proto-ctx | 0x20 segtree | 0x40 Returns a set of previously active debug flags, as returned by get_debug() method. """ val = self._flags_to_numeric(self.debug_flags, values) old = self.get_debug() self.nft_ctx_output_set_debug(self.__ctx, val) return old def cmd(self, cmdline): """Run a simple nftables command via libnftables. Accepts a string containing an nftables command just like what one would enter into an interactive nftables (nft -i) session. Returns a tuple (rc, output, error): rc -- return code as returned by nft_run_cmd_from_buffer() fuction output -- a string containing output written to stdout error -- a string containing output written to stderr """ cmdline_is_unicode = False if not isinstance(cmdline, bytes): cmdline_is_unicode = True cmdline = cmdline.encode("utf-8") rc = self.nft_run_cmd_from_buffer(self.__ctx, cmdline) output = self.nft_ctx_get_output_buffer(self.__ctx) error = self.nft_ctx_get_error_buffer(self.__ctx) if cmdline_is_unicode: output = output.decode("utf-8") error = error.decode("utf-8") return (rc, output, error) def json_cmd(self, json_root): """Run an nftables command in JSON syntax via libnftables. Accepts a hash object as input. Returns a tuple (rc, output, error): rc -- return code as returned by nft_run_cmd_from_buffer() function output -- a hash object containing library standard output error -- a string containing output written to stderr """ json_out_old = self.set_json_output(True) rc, output, error = self.cmd(json.dumps(json_root)) if not json_out_old: self.set_json_output(json_out_old) if len(output): output = json.loads(output) return (rc, output, error) def json_validate(self, json_root): """Validate JSON object against libnftables schema. Accepts a hash object as input. Returns True if JSON is valid, raises an exception otherwise. """ if not self.validator: self.validator = SchemaValidator() self.validator.validate(json_root) return True def cmd_from_file(self, filename): """Run a nftables command set from a file filename can be a str or a Path Returns a tuple (rc, output, error): rc -- return code as returned by nft_run_cmd_from_filename() function output -- a string containing output written to stdout error -- a string containing output written to stderr """ filename_is_unicode = False if not isinstance(filename, bytes): filename_is_unicode = True filename = str(filename) filename= filename.encode("utf-8") rc = self.nft_run_cmd_from_filename(self.__ctx, filename) output = self.nft_ctx_get_output_buffer(self.__ctx) error = self.nft_ctx_get_error_buffer(self.__ctx) if filename_is_unicode: output = output.decode("utf-8") error = error.decode("utf-8") return (rc, output, error) def add_include_path(self, filename): """Add a path to the include file list The default list includes the built-in default one Returns True on success, False if memory allocation fails """ if not isinstance(filename, bytes): filename = str(filename) filename= filename.encode("utf-8") rc = self.nft_ctx_add_include_path(self.__ctx, filename) return rc == 0 def clear_include_paths(self): """Clear include path list Will also remove the built-in default one """ self.nft_ctx_clear_include_paths(self.__ctx) def get_dry_run(self): """Get dry run state Returns True if set, False otherwise """ return self.nft_ctx_get_dry_run(self.__ctx) def set_dry_run(self, onoff): """ Set dry run state Returns the previous dry run state """ old = self.get_dry_run() self.nft_ctx_set_dry_run(self.__ctx, onoff) return old def add_var(self, var): """Add a variable to the variable list Returns True if added, False otherwise """ if not isinstance(var, bytes): var = var.encode("utf-8") rc = self.nft_ctx_add_var(self.__ctx, var) return rc == 0 def clear_vars(self): """Clear variable list """ self.nft_ctx_clear_vars(self.__ctx)
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