[Bug-wget] Overly permissive hostname matching

[Jeffrey Walton]

I believe wget has a security flaw in its certificate hostname matching code.

In the attached server certificate, the hostname is provided via a
Subject Alt Name (SAN). The only SAN entry is a DNS name for "*.com".
Also attached is the default CA, which was used to sign the server's
certificate.

Effectively, wget accepts a single certificate for the gTLD of .COM.
That's probably bad. If a CA is compromised, then the compromised CA
could issue a "super certificate" and cover the entire top level
domain space.

I suspect wget also accepts certificates for .COM's friends, like
.NET, .ORG, .MIL, etc.

Its probably not limited to gTLDs. Mozilla maintains a list of
effective TLDs at https://wiki.mozilla.org/Public_Suffix_List. The
1600+ effective TLDs are probably accepted, too.

Attached are the certificates, keys, and commands to set up a test rig
with OpenSSL's s_server. The certificates are issued for example.com,
and require a modification to /etc/hosts to make things work as
(un)expected.

Jeffrey Walton
Baltimore, MD, US

hostname-verification.tar.gz
Description: GNU Zip compressed data