From 901c0f6ede67b419e263eb1876f8720c791ed07f Mon Sep 17 00:00:00 2001 From: "Marcus R. Matos" Date: Sun, 5 Apr 2020 15:50:28 -0500 Subject: #3885 implement simpler regex for host validation --- mitmproxy/net/check.py | 29 +++++------------------------ test/mitmproxy/net/test_check.py | 10 ++-------- 2 files changed, 7 insertions(+), 32 deletions(-) diff --git a/mitmproxy/net/check.py b/mitmproxy/net/check.py index 32e733af..ffb5e163 100644 --- a/mitmproxy/net/check.py +++ b/mitmproxy/net/check.py @@ -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: diff --git a/test/mitmproxy/net/test_check.py b/test/mitmproxy/net/test_check.py index 7def75fd..649e71da 100644 --- a/test/mitmproxy/net/test_check.py +++ b/test/mitmproxy/net/test_check.py @@ -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') -- cgit v1.2.3