synapse-product/synapse/util/stringutils.py

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# Copyright 2014-2016 OpenMarket Ltd
# Copyright 2020 The Matrix.org Foundation C.I.C.
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#
# 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.
import itertools
import re
import secrets
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import string
from typing import Any, Iterable, Optional, Tuple
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from netaddr import valid_ipv6
from synapse.api.errors import Codes, SynapseError
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_string_with_symbols = string.digits + string.ascii_letters + ".,;:^&*-_+=#~@"
# https://matrix.org/docs/spec/client_server/r0.6.0#post-matrix-client-r0-register-email-requesttoken
CLIENT_SECRET_REGEX = re.compile(r"^[0-9a-zA-Z\.=_\-]+$")
# https://matrix.org/docs/spec/client_server/r0.6.1#matrix-content-mxc-uris,
# together with https://github.com/matrix-org/matrix-doc/issues/2177 which basically
# says "there is no grammar for media ids"
#
# The server_name part of this is purposely lax: use parse_and_validate_mxc for
# additional validation.
#
MXC_REGEX = re.compile("^mxc://([^/]+)/([^/#?]+)$")
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def random_string(length: int) -> str:
"""Generate a cryptographically secure string of random letters.
Drawn from the characters: `a-z` and `A-Z`
"""
return "".join(secrets.choice(string.ascii_letters) for _ in range(length))
def random_string_with_symbols(length: int) -> str:
"""Generate a cryptographically secure string of random letters/numbers/symbols.
Drawn from the characters: `a-z`, `A-Z`, `0-9`, and `.,;:^&*-_+=#~@`
"""
return "".join(secrets.choice(_string_with_symbols) for _ in range(length))
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def is_ascii(s: bytes) -> bool:
try:
s.decode("ascii").encode("ascii")
except UnicodeError:
return False
return True
def assert_valid_client_secret(client_secret: str) -> None:
"""Validate that a given string matches the client_secret defined by the spec"""
if (
len(client_secret) <= 0
or len(client_secret) > 255
or CLIENT_SECRET_REGEX.match(client_secret) is None
):
raise SynapseError(
400, "Invalid client_secret parameter", errcode=Codes.INVALID_PARAM
)
def parse_server_name(server_name: str) -> Tuple[str, Optional[int]]:
"""Split a server name into host/port parts.
Args:
server_name: server name to parse
Returns:
host/port parts.
Raises:
ValueError if the server name could not be parsed.
"""
try:
if server_name and server_name[-1] == "]":
# ipv6 literal, hopefully
return server_name, None
domain_port = server_name.rsplit(":", 1)
domain = domain_port[0]
port = int(domain_port[1]) if domain_port[1:] else None
return domain, port
except Exception:
raise ValueError("Invalid server name '%s'" % server_name)
# An approximation of the domain name syntax in RFC 1035, section 2.3.1.
# NB: "\Z" is not equivalent to "$".
# The latter will match the position before a "\n" at the end of a string.
VALID_HOST_REGEX = re.compile("\\A[0-9a-zA-Z-]+(?:\\.[0-9a-zA-Z-]+)*\\Z")
def parse_and_validate_server_name(server_name: str) -> Tuple[str, Optional[int]]:
"""Split a server name into host/port parts and do some basic validation.
Args:
server_name: server name to parse
Returns:
host/port parts.
Raises:
ValueError if the server name could not be parsed.
"""
host, port = parse_server_name(server_name)
# these tests don't need to be bulletproof as we'll find out soon enough
# if somebody is giving us invalid data. What we *do* need is to be sure
# that nobody is sneaking IP literals in that look like hostnames, etc.
# look for ipv6 literals
if host and host[0] == "[":
if host[-1] != "]":
raise ValueError("Mismatched [...] in server name '%s'" % (server_name,))
# valid_ipv6 raises when given an empty string
ipv6_address = host[1:-1]
if not ipv6_address or not valid_ipv6(ipv6_address):
raise ValueError(
"Server name '%s' is not a valid IPv6 address" % (server_name,)
)
elif not VALID_HOST_REGEX.match(host):
raise ValueError("Server name '%s' has an invalid format" % (server_name,))
return host, port
def valid_id_server_location(id_server: str) -> bool:
"""Check whether an identity server location, such as the one passed as the
`id_server` parameter to `/_matrix/client/r0/account/3pid/bind`, is valid.
A valid identity server location consists of a valid hostname and optional
port number, optionally followed by any number of `/` delimited path
components, without any fragment or query string parts.
Args:
id_server: identity server location string to validate
Returns:
True if valid, False otherwise.
"""
components = id_server.split("/", 1)
host = components[0]
try:
parse_and_validate_server_name(host)
except ValueError:
return False
if len(components) < 2:
# no path
return True
path = components[1]
return "#" not in path and "?" not in path
def parse_and_validate_mxc_uri(mxc: str) -> Tuple[str, Optional[int], str]:
"""Parse the given string as an MXC URI
Checks that the "server name" part is a valid server name
Args:
mxc: the (alleged) MXC URI to be checked
Returns:
hostname, port, media id
Raises:
ValueError if the URI cannot be parsed
"""
m = MXC_REGEX.match(mxc)
if not m:
raise ValueError("mxc URI %r did not match expected format" % (mxc,))
server_name = m.group(1)
media_id = m.group(2)
host, port = parse_and_validate_server_name(server_name)
return host, port, media_id
def shortstr(iterable: Iterable, maxitems: int = 5) -> str:
"""If iterable has maxitems or fewer, return the stringification of a list
containing those items.
Otherwise, return the stringification of a list with the first maxitems items,
followed by "...".
Args:
iterable: iterable to truncate
maxitems: number of items to return before truncating
"""
items = list(itertools.islice(iterable, maxitems + 1))
if len(items) <= maxitems:
return str(items)
return "[" + ", ".join(repr(r) for r in items[:maxitems]) + ", ...]"
def strtobool(val: str) -> bool:
"""Convert a string representation of truth to True or False
True values are 'y', 'yes', 't', 'true', 'on', and '1'; false values
are 'n', 'no', 'f', 'false', 'off', and '0'. Raises ValueError if
'val' is anything else.
This is lifted from distutils.util.strtobool, with the exception that it actually
returns a bool, rather than an int.
"""
val = val.lower()
if val in ("y", "yes", "t", "true", "on", "1"):
return True
elif val in ("n", "no", "f", "false", "off", "0"):
return False
else:
raise ValueError("invalid truth value %r" % (val,))
_BASE62 = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
def base62_encode(num: int, minwidth: int = 1) -> str:
"""Encode a number using base62
Args:
num: number to be encoded
minwidth: width to pad to, if the number is small
"""
res = ""
while num:
num, rem = divmod(num, 62)
res = _BASE62[rem] + res
# pad to minimum width
pad = "0" * (minwidth - len(res))
return pad + res
def non_null_str_or_none(val: Any) -> Optional[str]:
"""Check that the arg is a string containing no null (U+0000) codepoints.
If so, returns the given string unmodified; otherwise, returns None.
"""
return val if isinstance(val, str) and "\u0000" not in val else None