HTTPSConnection double wrapping IPv6 address during CONNECT

[derekhiggins]

Bug report

when http.client.HTTPSConnection is used with IPv6 addresses and a proxy results in the "Host:" Header being
wrapped in square brackets twice. (e.g. Host: [[fd2e:6f44:5dd8:c956::15]]:5050 )

$ cat /tmp/proxy_test.py
import http.client, ssl
conn = http.client.HTTPSConnection("fd2e:6f44:5dd8:c956::1", 8215, context=ssl._create_unverified_context())
conn.set_tunnel("[fd2e:6f44:5dd8:c956::15]", 5050)
conn.request("GET", "/", "")
response = conn.getresponse()
print(response.status, response.reason)

$ python3 /tmp/proxy_test.py
400 Bad Request


=== tcp dump showing extra squar brackets in "Host:" header ==
CONNECT [fd2e:6f44:5dd8:c956::15]:5050 HTTP/1.0

HTTP/1.1 200 Connection established

GET / HTTP/1.1
Host: [[fd2e:6f44:5dd8:c956::15]]:5050
Accept-Encoding: identity
Content-Length: 0

HTTP/1.1 400 Bad Request
Date: Thu, 12 Jan 2023 11:47:38 GMT
Server: Apache
Content-Length: 226
Connection: close
Content-Type: text/html; charset=iso-8859-1

Your environment

$ cat /etc/redhat-release
Red Hat Enterprise Linux CoreOS release 4.12

$ rpm -qf /usr/bin/python3
python3-3.9.10-4.el9_0.x86_64

Linked PRs

• gh-100985: Consistently wrap IPv6 IP address during CONNECT #100986
• [3.12] gh-100985: Consistently wrap IPv6 IP address during CONNECT (GH-100986) #115591
• [3.11] gh-100985: Consistently wrap IPv6 IP address during CONNECT (GH-100986) #115606