Bug 222044 - Verifying published files thanks to PGP key
Summary: Verifying published files thanks to PGP key
Status: Open
Alias: None
Product: Services
Classification: Unclassified
Component: Security Team (show other bugs)
Version: unspecified
Hardware: Any Any
: --- Affects Only Me
Assignee: Glen Barber
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2017-09-04 05:49 UTC by Nat Makarevitch
Modified: 2019-12-28 09:32 UTC (History)
5 users (show)

See Also:


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Description Nat Makarevitch 2017-09-04 05:49:04 UTC
I want to install FreeBSD 11.1.

The announce points towards (https://www.freebsd.org/releases/11.1R/announce.html#availability) a set of PGP-signed files ( https://www.freebsd.org/releases/11.1R/signatures.html )

I want to verify the origin and integrity, thanks to PGP (GPG, gnupg), and downloaded https://www.freebsd.org/releases/11.1R/CHECKSUM.SHA512-FreeBSD-11.1-RELEASE-amd64-vm.asc, which is signed by 8D12403C2E6CAB086CF64DA3031458A5478FE293

I could not easily find this public key.

It wasn't available through the announce, nor keyservers or in "The OpenPGP keys of the FreeBSD.org officers" ( https://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/pgpkeys.html ).

I was able to find this key by asking for help in the Freenode 'freebsd' IRC-channel (thanks to the 'qbsd' user, who published it in a keyring https://pastebin.com/raw/D88Yzxig ).

A serious search lets appear that the key is in https://www.freebsd.org/doc/pgpkeyring.txt (as a subkey of the A0B946A3 key), and this keyring is in the 'OpenPGP keys' article ( https://www.freebsd.org/doc/en_US.ISO8859-1/articles/pgpkeys/ ) pointed in the handbook's Appendix D. ('OpenPGP Keys') but only in the "complete keyring", therefore one has to import this whole keyring or to explore it.

AFAIK this is not a problem for anyone already using FreeBSD, who already has the keyring on his machine.

IMHO this can be made more easy for the newcomer, maybe by having the announce (  https://www.freebsd.org/releases/11.1R/signatures.html ) pointing towards a file containing all signing keys.

Moreover this signing subkey will soon expire (2017-09-25).
I'm not sure that signing with a soon-to-be-expired key is reinsuring for a person who, in the near future, will download the file after the key expiration date.

I also suggest that an OS documentation (Handbook, for the time being in "2.3.1. Prepare the Installation Media") may offer some hint about the usefulness of verifying any downloaded material thanks to a PGP-seal.
Comment 1 Gordon Tetlow freebsd_committer 2017-09-04 07:00:55 UTC
I'll talk to Glen when I see him at vBSDcon about moving from using a personal key to a release engineering team key (which doesn't appear to exist at the moment).
Comment 2 Chris Brannon 2017-10-28 01:25:41 UTC
I just tried to verify a FreeBSD 11.1 download, but the signing key has expired.
Comment 3 Glen Barber freebsd_committer 2017-11-01 16:51:59 UTC
Sorry for the delay, I forgot about this PR.  The expiration has been updated, and the updates committed to the Handbook, which should be visible within a few hours.
Comment 4 commit-hook freebsd_committer 2017-11-01 16:53:02 UTC
A commit references this bug:

Author: gjb
Date: Wed Nov  1 16:51:12 UTC 2017
New revision: 51163
URL: https://svnweb.freebsd.org/changeset/doc/51163

Log:
  Update PGP subkey expiration.

  Reported by:	Nat Makarevitch, Chris Brannon
  PR:		222044
  Sponsored by:	The FreeBSD Foundation

Changes:
  head/share/pgpkeys/gjb.key
Comment 5 Dave Eckhardt 2019-02-17 02:09:44 UTC
I would like to re-open this bug.

The 12.0-RELEASE Checksum Signatures page:

  https://www.freebsd.org/releases/12.0R/signatures.html

has this link for SHA256 signatures of i386:

  https://www.freebsd.org/releases/12.0R/CHECKSUM.SHA256-FreeBSD-12.0-RELEASE-i386.asc

Here is my verification attempt:

% gpg --verify CHECKSUM.SHA256-FreeBSD-12.0-RELEASE-i386.asc
gpg: Signature made Fri Dec  7 14:25:42 2018 EST using RSA key ID 478FE293
gpg: Can't check signature: No public key
% gpg --recv-key 478FE293
gpg: requesting key 478FE293 from hkp server pgpkeys.mit.edu
gpgkeys: key 478FE293 not found on keyserver
gpg: no valid OpenPGP data found.
gpg: Total number processed: 0

The PGP pathfinder (https://pgp.cs.uu.nl) says:

  Can't find key 478fe293 in the strong set; is it on the surfnet.nl keyserver?

Going back to the FreeBSD documentation, Appendix D of the handbook:

  https://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/pgpkeys.html

lists some keys, but not 478FE293.  That page has a link for "the complete keyring":

  https://www.freebsd.org/doc/pgpkeyring.txt

...which does not appear to contain 478FE293 either.  There is another page listing PGP keys, titled "OpenPGP keys":

  https://www.freebsd.org/doc/en_US.ISO8859-1/articles/pgpkeys/

That lists various security role keys (not including 478FE293) and also includes the "complete keyring" link.

I think at this point I am well beyond the steps that a regular user might be expected to take.  Basically I think the release-signing key(s) should be all over any FreeBSD.org page talking about PGP keys, and also on any key server that people might be likely to use.

Since I'm more dogged than the average user, I hunted around online; other people report a similar inability to find the key, including a StackExchange question which isn't really answered:

  https://unix.stackexchange.com/questions/346716/how-to-verify-freebsd-iso-download

and a FreeBSD forum post which led to this PR I am seeking to re-open (what happened with the forum post was that somebody mailed the poster a key):

  https://forums.freebsd.org/threads/verifying-published-files-integrity-and-origin.62297/

Then I got mad and went back to the PGP Pathfinder message.  It turns out that the key in question is *sort* *of* on surfnet.nl: 478FE293 is a sub-key of A0B946A3.  I guess I might have been expected to find that out from pgpkeyring.txt... but while that file does list five sub-keys for A0B946A3 it does not list 478FE293.

So here are my requests:

1. Please update pgpkeyring.txt.

2. Please institute a process for regularly updating pgpkeyring.txt.  For example, the step in the release process that does signing could fail if the relevant sub-key isn't visible in pgpkeyring.txt.

3. Please document how users can validate FreeBSD releases.  For example, the "12.0-RELEASE Checksum Signatures" page could say "These releases are signed by PGP key A0B946A3".  I realize that might not be the right thing to put into the Handbook, since later releases might be signed by somebody else, but the Handbook pages could specify a procedure with more steps that could be applied to any release.

Thanks!
Comment 6 Gordon Tetlow freebsd_committer 2019-02-17 23:19:54 UTC
Over to Glen for him to look at this issue.
Comment 7 Gordon Tetlow freebsd_committer 2019-02-17 23:20:31 UTC
Reopening based on current issue.
Comment 8 greencoppermine 2019-12-28 09:32:05 UTC
I cannot believe this issue is still open and not treated as urgent.

Surely being able to easily verify the integrity is pretty important.

Why haven't some kind of procedure been put in place yet?