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util.py
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util.py
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# Copyright 2014 ETH Zurich
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""
:mod:`util` --- SCION utilities
===============================
Various utilities for SCION functionality.
"""
# Stdlib
import json
import logging
import os
import shutil
import signal
import sys
import time
from binascii import hexlify
from datetime import datetime, timezone
from socket import MSG_DONTWAIT
# External packages
import yaml
from external.stacktracer import trace_start
# SCION
from lib.errors import (
SCIONIOError,
SCIONIndexError,
SCIONJSONError,
SCIONParseError,
SCIONTypeError,
SCIONYAMLError,
)
CERT_DIR = 'certs'
KEYS_DIR = 'keys'
TRACE_DIR = 'traces'
_SIG_MAP = {
signal.SIGHUP: "SIGHUP",
signal.SIGINT: "SIGINT",
signal.SIGQUIT: "SIGQUIT",
signal.SIGTERM: "SIGTERM",
signal.SIGUSR2: "SIGUSR2"
}
def get_cert_chain_file_path(conf_dir, isd_as, version): # pragma: no cover
"""
Return the certificate chain file path for a given ISD.
"""
return os.path.join(conf_dir, CERT_DIR,
'ISD%s-AS%s-V%s.crt' % (isd_as[0], isd_as[1], version))
def get_trc_file_path(conf_dir, isd, version): # pragma: no cover
"""
Return the TRC file path for a given ISD.
"""
return os.path.join(conf_dir, CERT_DIR, 'ISD%s-V%s.trc' % (isd, version))
def get_sig_key_file_path(conf_dir): # pragma: no cover
"""
Return the signing key file path.
"""
return os.path.join(conf_dir, KEYS_DIR, "as-sig.key")
def get_enc_key_file_path(conf_dir): # pragma: no cover
"""
Return the encryption key file path.
"""
return os.path.join(conf_dir, KEYS_DIR, "as-decrypt.key")
def get_online_key_file_path(conf_dir): # pragma: no cover
"""
Return the online key file path.
"""
return os.path.join(conf_dir, KEYS_DIR, "online-root.key")
def get_offline_key_file_path(conf_dir): # pragma: no cover
"""
Return the offline key file path.
"""
return os.path.join(conf_dir, KEYS_DIR, "offline-root.key")
def get_ca_private_key_file_path(conf_dir, name):
"""
Return the ca private key file path
"""
return os.path.join(conf_dir, "%s.key" % name)
def get_ca_cert_file_path(conf_dir, name):
"""
Return the ca certificate file path
"""
return os.path.join(conf_dir, "%s.cert" % name)
def read_file(file_path):
"""
Read and return contents of a file.
:param str file_path: the path to the file.
:returns: the file's contents.
:rtype: str
:raises:
lib.errors.SCIONIOError: error opening/reading from file.
"""
try:
with open(file_path) as file_handler:
return file_handler.read()
except OSError as e:
raise SCIONIOError("Unable to open '%s': %s" % (
file_path, e.strerror)) from None
def write_file(file_path, text):
"""
Write some text into a temporary file, creating its directory as needed, and
then atomically move to target location.
:param str file_path: the path to the file.
:param str text: the file content.
:raises:
lib.errors.SCIONIOError: IO error occurred
"""
dir_ = os.path.dirname(file_path)
try:
os.makedirs(dir_, exist_ok=True)
except OSError as e:
raise SCIONIOError("Error creating '%s' dir: %s" %
(dir_, e.strerror)) from None
tmp_file = file_path + ".new"
try:
with open(tmp_file, 'w') as f:
f.write(text)
except OSError as e:
raise SCIONIOError("Error creating/writing to temp file '%s': %s" %
(file_path, e.strerror)) from None
try:
os.rename(tmp_file, file_path)
except OSError as e:
raise SCIONIOError("Error moving '%s' to '%s': %s" %
(tmp_file, file_path, e.strerror)) from None
def copy_file(src, dst):
dst_dir = os.path.dirname(dst)
try:
os.makedirs(dst_dir, exist_ok=True)
except OSError as e:
raise SCIONIOError("Error creating dir '%s': %s" %
(dst_dir, e.strerror)) from None
try:
shutil.copyfile(src, dst)
except OSError as e:
raise SCIONIOError("Error copying '%s' to '%s': %s" %
(src, dst, e.strerror)) from None
def load_json_file(file_path):
"""
Read and parse a JSON config file.
:param str file_path: the path to the file.
:returns: JSON data
:rtype: dict
:raises:
lib.errors.SCIONIOError: error opening/reading from file.
lib.errors.SCIONJSONError: error parsing file.
"""
try:
with open(file_path) as f:
return json.load(f)
except OSError as e:
raise SCIONIOError("Error opening '%s': %s" %
(file_path, e.strerror)) from None
except (ValueError, KeyError, TypeError) as e:
raise SCIONJSONError("Error parsing '%s': %s" %
(file_path, e)) from None
def load_yaml_file(file_path):
"""
Read and parse a YAML config file.
:param str file_path: the path to the file.
:returns: YAML data
:rtype: dict
:raises:
lib.errors.SCIONIOError: error opening/reading from file.
lib.errors.SCIONYAMLError: error parsing file.
"""
try:
with open(file_path) as f:
return yaml.load(f)
except OSError as e:
raise SCIONIOError("Error opening '%s': %s" %
(file_path, e.strerror)) from None
except (yaml.scanner.ScannerError) as e:
raise SCIONYAMLError("Error parsing '%s': %s" %
(file_path, e)) from None
def update_dict(dictionary, key, values, elem_num=0):
"""
Update dictionary. Used for managing a temporary paths' cache.
"""
if key in dictionary:
dictionary[key].extend(values)
else:
dictionary[key] = values
dictionary[key] = dictionary[key][-elem_num:]
def calc_padding(length, block_size):
"""
Calculate how much padding is needed to bring `length` to a multiple of
`block_size`.
:param int length: The length of the data that needs padding.
:param int block_size: The block size.
"""
if length % block_size:
return block_size - (length % block_size)
else:
return 0
def trace(id_):
path = os.path.join(TRACE_DIR, "%s.trace.html" % id_)
trace_start(path)
def sleep_interval(start, interval, desc, quiet=False):
"""
Sleep until the `interval` seconds have elapsed since `start`.
If the interval is already over, log a warning with `desc` at the start.
:param float start:
Time (in seconds since the Epoch) the current interval started.
:param float interval: Length (in seconds) of an interval.
:param str desc: Description of the operation.
:param bool quiet: If set, don't log warnings.
"""
now = SCIONTime.get_time()
delay = start + interval - now
if delay < 0:
if not quiet:
logging.warning(
"%s took too long: %.3fs (should have been <= %.3fs)",
desc, now - start, interval)
delay = 0
time.sleep(delay)
def handle_signals():
"""Setup basic signal handler for the most common signals."""
# FIXME(kormat): the SIGUSR1 handler is actually silently overridden by
# pycapnp, so we can't use/catch it.
# https://github.com/jparyani/pycapnp/issues/101
for sig in _SIG_MAP.keys():
signal.signal(sig, _signal_handler)
def _signal_handler(signum, _):
"""Basic signal handler function."""
text = "Received %s" % _SIG_MAP[signum]
if signum in (signal.SIGTERM, signal.SIGINT):
logging.info(text)
sys.exit(0)
else:
logging.error(text)
sys.exit(1)
def iso_timestamp(ts): # pragma: no cover
"""
Format a unix timestamp as a UTC ISO 8601 format string
(YYYY-MM-DD HH:MM:SS.mmmmmm+00:00)
:param float ts: Seconds since the UNIX epoch.
"""
return str(datetime.fromtimestamp(ts, tz=timezone.utc))
def hex_str(raw):
"""Format a byte string as hex characters."""
return hexlify(raw).decode("ascii")
def recv_all(sock, total_len, flags):
barr = bytearray()
while len(barr) < total_len:
# The first recv call must support non-blocking mode to raise an error
# if the socket is not ready. Subsequent calls should be blocking to
# avoid sync problems.
if flags & MSG_DONTWAIT and len(barr) > 0:
flags &= ~MSG_DONTWAIT
try:
buf = sock.recv(total_len - len(barr), flags)
except InterruptedError:
continue
if not buf:
if not barr:
logging.debug("recv returned nil, socket closed")
else:
logging.error("socket connection prematurely terminated")
return None
barr += buf
return bytes(barr)
class SCIONTime(object):
"""A class to return current time."""
# Function which would return time upon calling it
# Can be set using set_time_method
_custom_time = None
@classmethod
def get_time(cls):
"""Get current time."""
if cls._custom_time:
return cls._custom_time()
else:
return time.time()
@classmethod
def set_time_method(cls, method=None):
"""Set the method used to get time."""
cls._custom_time = method
class Raw(object):
"""A class to wrap raw bytes objects."""
def __init__(self, data, desc="", len_=None,
min_=False): # pragma: no cover
self._data = data
self._desc = desc
self._len = len_
self._min = min_
self._offset = 0
self.check_type()
self.check_len()
def check_type(self):
"""
Check that the data is a `bytes` instance. If not, raise an exception.
:raises:
lib.errors.SCIONTypeError: data is the wrong type
"""
if not isinstance(self._data, bytes):
raise SCIONTypeError(
"Error parsing raw %s: Expected %s, got %s" %
(self._desc, bytes, type(self._data)))
def check_len(self):
"""
Check that the data is of the expected length. If not, raise an
exception.
:raises:
lib.errors.SCIONTypeError: data is the wrong length
"""
if self._len is None:
return
if self._min:
if len(self._data) >= self._len:
return
else:
op = ">="
elif len(self._data) == self._len:
return
else:
op = "=="
raise SCIONParseError(
"Error parsing raw %s: Expected len %s %s, got %s" %
(self._desc, op, self._len, len(self._data)))
def get(self, n=None, bounds=True):
"""
Return next elements from data.
If `n` is not specified, return all remaining elements of data.
If `n` is 1, return the next element of data (as an int).
If `n` is > 1, return the next `n` elements of data (as bytes).
:param n: How many elements to return (see above)
:param bool bounds: Perform bounds checking on access if True
"""
dlen = len(self._data)
if n and bounds and (self._offset + n) > dlen:
raise SCIONIndexError("%s: Attempted to access beyond end of raw "
"data (len=%d, offset=%d, request=%d)" %
(self._desc, dlen, self._offset, n))
if n is None:
return self._data[self._offset:]
elif n == 1:
return self._data[self._offset]
else:
return self._data[self._offset:self._offset + n]
def pop(self, n=None, bounds=True):
"""
Return next elements from data, and advance the internal offset.
Arguments have the same meaning as for Raw.get
"""
ret = self.get(n, bounds)
dlen = len(self._data)
if n is None:
self._offset = dlen
elif n == 1:
self._offset += 1
else:
self._offset += n
if self._offset > dlen:
self._offset = dlen
return ret
def offset(self): # pragma: no cover
return self._offset
def __len__(self):
return max(0, len(self._data) - self._offset)