Merge lp:~xnox/ubuntu-archive-publishing/gnupg2 into lp:ubuntu-archive-publishing

[Dimitri John Ledkov]

continue to use just the 1k DSA key for dist-upgrader tarballs.

From z-series and up, use just the 4k RSA key for both archive signing & dist-upgrader tarballs.

[lp:~xnox/ubuntu-archive-publishing/gnupg2]

89. By Dimitri John Ledkov on 2016-11-03

replace z-series with zesty.

[Lee Trager (ltrager)]

LGTM!

review: Approve

[Steve Langasek (vorlon)]

review: Needs Fixing

[Steve Langasek (vorlon)]

On Fri, Nov 04, 2016 at 09:23:37PM -0000, Adam Conrad wrote:

> We're trusting the 1024 key regardless of what we use to sign. If we sign
> with the 4096, someone can still MITM using a compromised 1024 key.

That's not an argument for continuing to sign with the 1024 key where we
know the 4096 key will work, though.

> If we're concerned about that, we should SRU a violent change to
> everything >= trusty to stop trusting the 1024 key. That could cause
> issues for people behind the curve trying to upgrade through old-releases
> though.

We should prefer *not* having to SRU a violent change, which means we
*should* take these small steps towards deprecating the 1024 key where
possible.

> I suspect this was done just to keep the diff low and reviewable, but I
> agree a second MP to change all the keys to long IDs would be sane (though
> collision attacks on pepo are not actually an issue).

Right, but I want consistency here - all references to a given key should
either be short id or long id, not a mix of both.

=== modified file 'publish-distro.d/10-sign-releases'
--- publish-distro.d/10-sign-releases	2016-06-20 17:40:52 +0000
+++ publish-distro.d/10-sign-releases	2016-11-03 23:00:00 +0000
@@ -33,10 +33,16 @@
 	case $LPCONFIG in
 	    ftpmaster-publish)
 		case "$series:$1" in
-		    warty:*|hoary:*|breezy:*|dapper:*|edgy:*|feisty:*|gutsy:*|hardy:*|intrepid:*|jaunty:*|karmic:*|lucid:*|maverick:*|natty:*|oneiric:*|precise:*|*:*/dist-upgrader*)
-			printf '%s\n' "-u 437D05B5"
-			;;
-		    *)
+		    # Use 1024 key for old releases
+		    warty:*|hoary:*|breezy:*|dapper:*|edgy:*|feisty:*|gutsy:*|hardy:*|intrepid:*|jaunty:*|karmic:*|lucid:*|maverick:*|natty:*|oneiric:*|precise:*)
+			printf '%s\n' "-u 437D05B5"
+			;;
+		    # Use single-signature, old 1024 key, for dist-upgrade tarballs (historical)
+		    quantal:*/dist-upgrader*|raring:*/dist-upgrader*|saucy:*/dist-upgrader*|trusty:*/dist-upgrader*|utopic:*/dist-upgrader*|vivid:*/dist-upgrader*|wily:*/dist-upgrader*|xenial:*/dist-upgrader*|yakkety:*/dist-upgrader*)
+			printf '%s\n' "-u 437D05B5"
+			;;
+		    # Use dual-signatures for the archive, for a transitioning period
+		    quantal:*|raring:*|saucy:*|trusty:*|utopic:*|vivid:*|wily:*|xenial:*|yakkety:*)
 			# 437D05B5 and C0B21F32 have different digest
 			# preferences.  GnuPG refuses to consider multiple
 			# signatures unless they use the same signature
@@ -48,6 +54,10 @@
 			# SHA-512 for both.
 			printf '%s\n' "-u 437D05B5 -u C0B21F32 --digest-algo SHA512"
 			;;
+		    *)
+		    # For zesty and up, including dist-upgrade tarballs, use 2012 4k RSA key only
+			printf '%s\n' "-u 0x790BC7277767219C42C86F933B4FE6ACC0B21F32 --digest-algo SHA512"
+			;;
 		esac
 		;;
 	    derived-distro-publish)