diff --git a/synapse/util/stringutils.py b/synapse/util/stringutils.py
index 61d96a6c28..f8038bf861 100644
--- a/synapse/util/stringutils.py
+++ b/synapse/util/stringutils.py
@@ -18,6 +18,7 @@ import random
import re
import string
from collections.abc import Iterable
+from typing import Optional, Tuple
from synapse.api.errors import Codes, SynapseError
@@ -26,6 +27,15 @@ _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\.\=\_\-]+$")
+# https://matrix.org/docs/spec/client_server/r0.6.1#matrix-content-mxc-uris,
+# together with https://github.com/matrix-org/matrix-doc/issues/2177 which basically
+# says "there is no grammar for media ids"
+#
+# The server_name part of this is purposely lax: use parse_and_validate_mxc for
+# additional validation.
+#
+MXC_REGEX = re.compile("^mxc://([^/]+)/([^/#?]+)$")
+
# random_string and random_string_with_symbols are used for a range of things,
# some cryptographically important, some less so. We use SystemRandom to make sure
# we get cryptographically-secure randoms.
@@ -59,6 +69,88 @@ def assert_valid_client_secret(client_secret):
)
+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[-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)
+
+
+VALID_HOST_REGEX = re.compile("\\A[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[0] == "[":
+ if host[-1] != "]":
+ raise ValueError("Mismatched [...] in server name '%s'" % (server_name,))
+ return host, port
+
+ # otherwise it should only be alphanumerics.
+ if not VALID_HOST_REGEX.match(host):
+ raise ValueError(
+ "Server name '%s' contains invalid characters" % (server_name,)
+ )
+
+ return host, port
+
+
+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.
@@ -75,3 +167,22 @@ def shortstr(iterable: Iterable, maxitems: int = 5) -> str:
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,))
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