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#3885 implement simpler regex for host validation

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This commit is contained in:
Marcus R. Matos 2020-04-05 15:50:28 -05:00
parent 2722f4fd76
commit 901c0f6ede
2 changed files with 7 additions and 32 deletions
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29
mitmproxy/net/check.py
View File

@ -1,24 +1,9 @@
import ipaddress
import re
"""
The rules for host names are different from DNS Names (aka "Label").
DNS Names allow for hyphens and underscores (RFC-2872).
Hostnames DO allow for hyphens, but not underscores. (RFC-952, RFC-1123)
The main issue is the existence of DNS labels that are actually
capable of being resolved to a valid IP, even if the label
isn't a valid hostname (e.g. api-.example.com, @.example.com)
Since the value we're checking could be an IP, a host name, a DNS label, or a FQDN,
and there are cases where DNS or Hostnames are misconfigured despite RFC
we'll go with the least restrictive rules while still providing a sanity check.
"""
# label regex: in total between 4 and 255 chars, tld 2 to 63 chars, each label 1 to 63 chars
_label_valid = re.compile(
br"^(?=.{4,255}$)([A-Z0-9_-]([A-Z0-9_-]{0,61}[A-Z0-9_-])?\.)"
br"{1,126}[A-Z0-9][A-Z0-9-]{0,61}[A-Z0-9]$", re.IGNORECASE)
_host_valid = re.compile(br"[A-Z0-9\-_]{1,63}$", re.IGNORECASE)
# Allow underscore in host name
# Note: This could be a DNS label, a hostname, a FQDN, or an IP
_label_valid = re.compile(br"[A-Z\d\-_]{1,63}$", re.IGNORECASE)
def is_valid_host(host: bytes) -> bool:
@ -32,14 +17,10 @@ def is_valid_host(host: bytes) -> bool:
# RFC1035: 255 bytes or less.
if len(host) > 255:
return False
# Trim trailing period
if host and host[-1:] == b".":
host = host[:-1]
# DNS label
if b"." in host and _label_valid.match(host):
return True
# hostname
if b"." not in host and _host_valid.match(host):
# DNS hostname
if all(_label_valid.match(x) for x in host.split(b".")):
return True
# IPv4/IPv6 address
try:

10
test/mitmproxy/net/test_check.py
View File

@ -13,7 +13,8 @@ def test_is_valid_host():
assert check.is_valid_host(b"one_two")
assert check.is_valid_host(b"::1")
# IPv6 Validations
# IP Address Validations
assert check.is_valid_host(b'127.0.0.1')
assert check.is_valid_host(b'2001:0db8:85a3:0000:0000:8a2e:0370:7334')
assert check.is_valid_host(b'2001:db8:85a3:0:0:8a2e:370:7334')
assert check.is_valid_host(b'2001:db8:85a3::8a2e:370:7334')
@ -21,7 +22,6 @@ def test_is_valid_host():
assert check.is_valid_host(b'2001-db8-85a3-8d3-1319-8a2e-370-7348.ipv6-literal.net')
# TLD must be between 2 and 63 chars
assert not check.is_valid_host(b'example.t')
assert check.is_valid_host(b'example.tl')
assert check.is_valid_host(b'example.tld')
assert check.is_valid_host(b'example.' + b"x" * 63)
@ -51,9 +51,6 @@ def test_is_valid_host():
assert check.is_valid_host(b'_a.example.tld')
assert check.is_valid_host(b'a_.example.tld')
assert check.is_valid_host(b'_a_.example.tld')
assert not check.is_valid_host(b'a._example')
assert not check.is_valid_host(b'a._example_')
assert not check.is_valid_host(b'a.example_')
# Misc Dash/Hyphen/Minus Test Cases
assert check.is_valid_host(b'-example')
@ -62,9 +59,6 @@ def test_is_valid_host():
assert check.is_valid_host(b'-a.example.tld')
assert check.is_valid_host(b'a-.example.tld')
assert check.is_valid_host(b'-a-.example.tld')
assert not check.is_valid_host(b'a.-example')
assert not check.is_valid_host(b'a.-example-')
assert not check.is_valid_host(b'a.example-')
# Misc Combo Test Cases
assert check.is_valid_host(b'api-.example.com')