[release-branch.go1.17] net/http: preserve nil values in Header.Clone
ReverseProxy makes a distinction between nil and zero-length header values.
Avoid losing nil-ness when cloning a request.
Thanks to Christian Mehlmauer for discovering this.
For #53423
For CVE-2022-32148
Fixes #53620
Change-Id: Ice369cdb4712e2d62e25bb881b080847aa4801f5
Reviewed-on: https://go-review.googlesource.com/c/go/+/412857
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
(cherry picked from commit
b2cc0fecc2ccd80e6d5d16542cc684f97b3a9c8a)
Reviewed-on: https://go-review.googlesource.com/c/go/+/415221
Reviewed-by: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Heschi Kreinick <heschi@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>