Re: announce-gen and OpenPGP key servers

[Simon Josefsson via Gnulib discussion list <bug-gnulib@gnu.org>]

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Jim Meyering <jim@meyering.net> writes:

> Feel free to make the script generate a full fingerprint and even
> (though it feels a little like giving up) add a checksum or two.

I think checksums still serve a purpose.

Many announcement e-mails are OpenPGP signed (and sometimes with a
different key than the release tarballs, thus creating another way to
verify tarballs).

Checksums also makes it harder to replace the tarball on the server with
a fake (or, after a key compromise, a genuine) signature.

I don't think it is a either-or situation, but rather a
belt-and-suspender case.  Ideally, people downloading a release should
verify both the signature (to know it comes from a trusted origin) and
checksum (to know it is the intended release, in case multiple signed
versions co-exists).

The patches below make the maintainer-makefile announcements contain
SHA1 and B64(SHA256) checksums by default.  The MD5 checksums are
dropped; they are completely insecure now.  The B64(SHA256) output is
inspired by OpenSSH which started this practice with release 6.5 in 2014
and still today prints similar outputs, see:

https://www.openssh.com/txt/release-6.5
https://www.openssh.com/txt/release-8.6

Unfortunately, 'sha256sum' can't verify these outputs, but I recall
earlier discussions around 'sha256sum --base64' so I will resume work on
that.

We could opt to simply use the "standard" sha256sum output instead, if
people here don't like the base64 output format.

/Simon

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From 4adae938b8dbe01750698109bcbf5f1c9eb045b1 Mon Sep 17 00:00:00 2001
From: Simon Josefsson <simon@josefsson.org>
Date: Tue, 3 Aug 2021 17:15:16 +0200
Subject: [PATCH 1/2] announce-gen: Print SHA1/B64(SHA256) instead of MD5/SHA1.

* build-aux/announce-gen (%digest_classes): Removed.
(usage): Doc fix.
(print_checksums): Instead of MD5/SHA1, print SHA1 and
B64(SHA256), inspired by OpenSSH announcements.
---
 ChangeLog              |  8 ++++++++
 build-aux/announce-gen | 33 +++++++++++----------------------
 2 files changed, 19 insertions(+), 22 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 06f139a54..079a5b71c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2021-08-03  Simon Josefsson  <simon@josefsson.org>
+
+	announce-gen: Print SHA1/B64(SHA256) instead of MD5/SHA1.
+	* build-aux/announce-gen (%digest_classes): Removed.
+	(usage): Doc fix.
+	(print_checksums): Instead of MD5/SHA1, print SHA1 and
+	B64(SHA256), inspired by OpenSSH announcements.
+
 2021-08-02  Paul Eggert  <eggert@cs.ucla.edu>
 
 	manywarnings: enable some malloc warnings
diff --git a/build-aux/announce-gen b/build-aux/announce-gen
index daa478c8e..b07cbd742 100755
--- a/build-aux/announce-gen
+++ b/build-aux/announce-gen
@@ -35,7 +35,7 @@
 eval 'exec perl -wSx "$0" "$@"'
      if 0;
 
-my $VERSION = '2021-04-11 8:42'; # UTC
+my $VERSION = '2021-08-03 15:13'; # UTC
 # The definition above must lie within the first 8 lines in order
 # for the Emacs time-stamp write hook (at end) to update it.
 # If you change this file with Emacs, please let the write hook
@@ -51,12 +51,6 @@ use POSIX qw(strftime);
 
 my %valid_release_types = map {$_ => 1} qw (alpha beta stable);
 my @archive_suffixes = qw (tar.gz tar.bz2 tar.lz tar.lzma tar.xz);
-my %digest_classes =
-  (
-   'md5' => (eval { require Digest::MD5; } and 'Digest::MD5'),
-   'sha1' => ((eval { require Digest::SHA; } and 'Digest::SHA')
-              or (eval { require Digest::SHA1; } and 'Digest::SHA1'))
-  );
 my $srcdir = '.';
 
 sub usage ($)
@@ -96,7 +90,7 @@ The following are optional:
                                 VERSION is the result of running git describe
                                 in the gnulib source directory.
                                 required if gnulib is in TOOL_LIST.
-   --no-print-checksums         do not emit MD5 or SHA1 checksums
+   --no-print-checksums         do not emit SHA1 or SHA256 checksums
    --archive-suffix=SUF         add SUF to the list of archive suffixes
    --mail-headers=HEADERS       a space-separated list of mail headers, e.g.,
                                 To: x\@example.com Cc: y-announce\@example.com,...
@@ -163,7 +157,7 @@ sub print_locations ($\@\%@)
 
 =item C<print_checksums (@file)
 
-Print the MD5 and SHA1 signature section for each C<@file>.
+Print the SHA1 and SHA256 signature section for each C<@file>.
 
 =cut
 
@@ -171,23 +165,18 @@ sub print_checksums (@)
 {
   my (@file) = @_;
 
-  print "Here are the MD5 and SHA1 checksums:\n";
+  print "Here are the SHA1 and SHA256 checksums:\n";
   print "\n";
 
-  foreach my $meth (qw (md5 sha1))
+  use Digest::file qw(digest_file_hex digest_file_base64);
+
+  foreach my $f (@file)
     {
-      my $class = $digest_classes{$meth} or next;
-      foreach my $f (@file)
-        {
-          open IN, '<', $f
-            or die "$ME: $f: cannot open for reading: $!\n";
-          binmode IN;
-          my $dig = $class->new->addfile(*IN)->hexdigest;
-          close IN;
-          print "$dig  $f\n";
-        }
+      print digest_file_hex($f, "SHA-1"), "  $f\n";
+      print digest_file_base64($f, "SHA-256"), "  $f\n";
     }
-  print "\n";
+  print "\nPlease note that the SHA256 checksum is base64 encoded and not\n";
+  print "hexadecimal (which is the default for most checksum tools).\n\n";
 }
 
 =item C<print_news_deltas ($news_file, $prev_version, $curr_version)
-- 
2.30.2


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From 3ace7783656f3e38b6db4e44881959116e581a2b Mon Sep 17 00:00:00 2001
From: Simon Josefsson <simon@josefsson.org>
Date: Tue, 3 Aug 2021 17:16:42 +0200
Subject: [PATCH 2/2] maintainer-makefile: Print checksums by default.

* top/maint.mk (announcement): Drop --no-print-checksums.
---
 ChangeLog    | 3 +++
 top/maint.mk | 1 -
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/ChangeLog b/ChangeLog
index 079a5b71c..cb65d202b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -6,6 +6,9 @@
 	(print_checksums): Instead of MD5/SHA1, print SHA1 and
 	B64(SHA256), inspired by OpenSSH announcements.
 
+	maintainer-makefile: Print checksums by default.
+	* top/maint.mk (announcement): Drop --no-print-checksums.
+
 2021-08-02  Paul Eggert  <eggert@cs.ucla.edu>
 
 	manywarnings: enable some malloc warnings
diff --git a/top/maint.mk b/top/maint.mk
index 044254bdc..6a3ea9606 100644
--- a/top/maint.mk
+++ b/top/maint.mk
@@ -1426,7 +1426,6 @@ announcement: NEWS ChangeLog $(rel-files)
 	    --bootstrap-tools=$(bootstrap-tools)			\
 	    $$(case ,$(bootstrap-tools), in (*,gnulib,*)		\
 	       echo --gnulib-version=$(gnulib-version);; esac)		\
-	    --no-print-checksums					\
 	    $(addprefix --url-dir=, $(url_dir_list))
 
 .PHONY: release-commit
-- 
2.30.2


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