Follow @Openwall on Twitter for new release announcements and other news
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Sat, 27 Oct 2018 16:54:46 +0200
From: Jakub Wilk <>
Subject: Re: Travis CI MITM RCE

Response from Travis CI:

Some clarifications:

* Jakub Wilk <>, 2018-08-25, 23:49:
>On 2018-07-05, --force-yes was replaced with --allow-downgrades 
>--allow-remove-essential --allow-change-held-packages: 
>I'm not sure how could this change possibly work, because APT in the 
>Ubuntu versions Travis CI supports (precise, trusty) doesn't have 
>these options…

It did work, because Travis CI folks installed backported APT 1.2.X, 
with support for these options...

>So a few days later --force-yes was added back: 

...but this fix had an off-by-one bug in version check, which made APT 
1.2.X still use --force-yes. The bug was fixed soon after my advisory:

>2) On 2017-10-12, code was added to refresh an expired signing key: 
>The code used 32-bit key ID to retrieve the key from the keyserver. I 
>reported this on 2017-12-06: 

My proposed fix was to use "gpg --recv-key" with full fingerprint. But I 
now discovered that even this is not resistant against MitM attacks:

"[...] modern gpg automatically applies an import screener that only 
accepts OpenPGP certificates that have the given fingerprint [...]

However, it's possible for someone else to make a new OpenPGP 
certificate that includes the key in question without knowledge of the 
secret key (e.g. as a non-cross-signed subkey).

As a result, an attacker can bypass the import screener and inject new 
primary keys into the keyring. [...]"

Jakub Wilk

Powered by blists - more mailing lists

Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.