1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
|
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}$)([A-Z0-9_-]([A-Z0-9_-]{0,61}[A-Z0-9_-])?\.){1,126}[A-Z0-9][A-Z0-9-]{0,61}[A-Z0-9]$", re.IGNORECASE)
_host_valid = re.compile(br"[A-Z0-9\-_]{1,63}$", re.IGNORECASE)
def is_valid_host(host: bytes) -> bool:
"""
Checks if the passed bytes are a valid DNS hostname or an IPv4/IPv6 address.
"""
try:
host.decode("idna")
except ValueError:
return False
# 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):
return True
# IPv4/IPv6 address
try:
ipaddress.ip_address(host.decode('idna'))
return True
except ValueError:
return False
def is_valid_port(port: int) -> bool:
return 0 <= port <= 65535
|
