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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"""
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.1.1.0"):
"""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.
"""
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_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_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):
self.nft_ctx_free(self.__ctx)
def __get_output_flag(self, name):
flag = self.output_flags[name]
return self.nft_ctx_output_get_flags(self.__ctx) & flag
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
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)
names = []
for n,v in self.debug_flags.items():
if val & v:
names.append(n)
val &= ~v
if val:
names.append(val)
return names
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.
"""
old = self.get_debug()
if type(values) in [str, int]:
values = [values]
val = 0
for v in values:
if type(v) is str:
v = self.debug_flags[v]
val |= v
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