diff options
author | 2019-07-03 22:33:06 +0200 | |
---|---|---|
committer | 2019-07-03 23:05:10 +0200 | |
commit | 72dbcbfd9a32f13c2a4183b04f910e7ae403cba0 (patch) | |
tree | c8d97e9f72ac1922a6713783942cfb980da2e789 | |
parent | become-developers: Remove stale Mentors project link (diff) | |
download | www-72dbcbfd9a32f13c2a4183b04f910e7ae403cba0.tar.gz www-72dbcbfd9a32f13c2a4183b04f910e7ae403cba0.tar.bz2 www-72dbcbfd9a32f13c2a4183b04f910e7ae403cba0.zip |
_posts: Publish a news post about SKS key poisoning
Signed-off-by: Michał Górny <mgorny@gentoo.org>
-rw-r--r-- | _posts/2019-07-03-sks-key-poisoning.md | 71 |
1 files changed, 71 insertions, 0 deletions
diff --git a/_posts/2019-07-03-sks-key-poisoning.md b/_posts/2019-07-03-sks-key-poisoning.md new file mode 100644 index 0000000..7483bf8 --- /dev/null +++ b/_posts/2019-07-03-sks-key-poisoning.md @@ -0,0 +1,71 @@ +--- +title: Impact of SKS keyserver poisoning on Gentoo +--- + +The [SKS keyserver network has been a victim of certificate poisoning +attack](https://gist.github.com/rjhansen/67ab921ffb4084c865b3618d6955275f) +lately. The OpenPGP verification used for repository syncing is protected +against the attack. However, our users can be affected when using GnuPG +directly. In this post, we would like to shortly summarize what the attack is, +what we did to protect Gentoo against it and what can you do to protect your +system. + +<!--more--> + +The certificate poisoning attack abuses three facts: that OpenPGP keys can +contain unlimited number of signatures, that anyone can append signatures +to any key and that there is no way to distinguish a legitimate signature +from garbage. The attackers are appending a large number of garbage signatures +to keys stored on SKS keyservers, causing them to become very large and cause +severe performance issues in GnuPG clients that fetch them. + +The attackers have poisoned the keys of a few high ranking OpenPGP people +on the SKS keyservers, including one Gentoo developer. Furthermore, the +current expectation is that the problem won't be fixed any time soon, so it +seems plausible that more keys may be affected in the future. We recommend +users not to fetch or refresh keys from SKS keyserver network (this includes +aliases such as `keys.gnupg.net`) for the time being. GnuPG upstream is +already working on client-side countermeasures and they can be expected to +enter Gentoo as soon as they are released. + +The Gentoo key infrastructure has not been affected by the attack. Shortly +after it was reported, we have disabled fetching developer key updates from SKS +and today we have disabled public key upload access to prevent the keys stored +on the server from being poisoned by a malicious third party. + +The gemato tool used to verify the Gentoo ebuild repository uses +[WKD](https://wiki.gnupg.org/WKD) by default. During normal operation it should +not be affected by this vulnerability. Gemato has a keyserver fallback that +might be vulnerable if WKD fails, however gemato operates in an isolated +environment that will prevent a poisoned key from causing permanent damage to +your system. In the worst case; Gentoo repository syncs will be slow or hang. + +The webrsync and delta-webrsync methods also support gemato, although it is +not used by default at the moment. In order to use it, you need to remove +`PORTAGE_GPG_DIR` from `/etc/portage/make.conf` (if it present) and put +the following values into `/etc/portage/repos.conf`: + + [gentoo] + sync-type = webrsync + sync-webrsync-delta = true # false to use plain webrsync + sync-webrsync-verify-signature = true + +Afterwards, calling `emerge --sync` or `emaint sync --repo gentoo` will use +gemato key management rather than the vulnerable legacy method. The default is +going to be changed in a future release of Portage. + +When using GnuPG directly, Gentoo developer and service keys can +be securely fetched (and refreshed) via: + +1. Web Key Directory, e.g. `gpg --locate-key developer@gentoo.org` +2. [Gentoo keyserver](https://keys.gentoo.org), + e.g. `gpg --keyserver hkps://keys.gentoo.org ...` +3. Key bundles, e.g.: + [active devs](https://qa-reports.gentoo.org/output/active-devs.gpg), + [service keys](https://qa-reports.gentoo.org/output/service-keys.gpg) + +Please note that the aforementioned services provide only keys specific +to Gentoo. Keys belonging to other people will not be found on our keyserver. +If you are looking for them, you may try [keys.openpgp.org]( +https://keys.openpgp.org/) keyserver that is not vulnerable to the attack, +at the cost of stripping all signatures and unverified UIDs. |