MSYS2-packages/gnupg/0015-gpg-emit-RSA-pubkey-algorithm-when-in-compatibility-.patch

From 85619355cd487e392032ac324b8bf17d876792b1 Mon Sep 17 00:00:00 2001
From: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
Date: Tue, 4 Feb 2025 01:22:41 -0500
Subject: [PATCH] gpg: emit RSA pubkey algorithm when in compatibility modes

* doc/gpg.texi (Compliance Options): --gnupg offers LibrePGP behavior,
and prefers LibrePGP where it diverges from OpenPGP; --rfc4880bis is
an alias for --gnupg; Explain that --rfc2440 is ancient; correct
punctuation. (default-new-key-algo): drop incorrect information
about defaults. (default-new-key-algo): Remind the user that this
should come after any compliance modes, like --allow-old-cipher-algos.
* g10/gpg.c (set_compliance_option): default pubkey algorithm for
legacy compliance is 3072-bit RSA.
* common/compliance.c (gnupg_compliance_label) new function,
prototyped...
* common/compliance.h: ...here.
* g10/keygen.c (parse_key_parameter_part): when using a legacy
compliance mode, ensure that new keys are only algorithms known by the
corresponding tools.

--

Before this fix, the following command:

   gpg --rfc4880 --quick-gen-key "$USERID"

would produce an OpenPGP secret key that would not be compatible for
use with an RFC 4880 client.  The generated certificate would be a
problem if the user has a another OpenPGP client that is limited to
RFC 4880, and it would be a problem for any peer who wants
to encrypt to or validate signatures from the corresponding
certificate.

With this fix, default key generation under a compatibility mode will
actually produce compatible, interoperable OpenPGP key.

GnuPG-bug-id: 7511
Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
---
 common/compliance.c |  7 +++++++
 common/compliance.h |  2 ++
 doc/gpg.texi        | 40 ++++++++++++++++++----------------------
 g10/gpg.c           |  3 +++
 g10/keygen.c        |  9 +++++++++
 5 files changed, 39 insertions(+), 22 deletions(-)

diff --git a/common/compliance.c b/common/compliance.c
index 84449af25..5e468a11c 100644
--- a/common/compliance.c
+++ b/common/compliance.c
@@ -696,6 +696,13 @@ gnupg_parse_compliance_option (const char *string,
   return -1;
 }
 
+/* Return label for the given COMPLIANCE mode.  */
+const char *
+gnupg_compliance_label (enum gnupg_compliance_mode compliance)
+{
+  /* just offset by strlen("--compliance=") */
+  return gnupg_compliance_option_string (compliance) + 13;
+}
 
 /* Return the command line option for the given COMPLIANCE mode.  */
 const char *
diff --git a/common/compliance.h b/common/compliance.h
index 111fdc74b..2ddf38f83 100644
--- a/common/compliance.h
+++ b/common/compliance.h
@@ -91,6 +91,8 @@ int gnupg_parse_compliance_option (const char *string,
                                    int quiet);
 const char *gnupg_compliance_option_string (enum gnupg_compliance_mode
                                             compliance);
+const char *gnupg_compliance_label (enum gnupg_compliance_mode
+                                    compliance);
 
 void gnupg_set_compliance_extra_info (unsigned int min_rsa);
 
diff --git a/doc/gpg.texi b/doc/gpg.texi
index 4f44e4530..834c5dda5 100644
--- a/doc/gpg.texi
+++ b/doc/gpg.texi
@@ -3094,12 +3094,11 @@ options.
 
 @item --gnupg
 @opindex gnupg
-Use standard GnuPG behavior. This is essentially OpenPGP behavior (see
-@option{--openpgp}), but with extension from the proposed update to
-OpenPGP and with some additional workarounds for common compatibility
-problems in different versions of PGP.  This is the default option, so
-it is not generally needed, but it may be useful to override a
-different compliance option in the gpg.conf file.
+Use standard GnuPG behavior. This is now LibrePGP behavior, which is a
+different draft protocol that overlaps in some cases with
+OpenPGP. This is the default option, so it is not generally needed,
+but it may be useful to override a different compliance option in the
+gpg.conf file.
 
 @item --openpgp
 @opindex openpgp
@@ -3118,21 +3117,20 @@ Note that this is currently the same thing as @option{--openpgp}.
 
 @item --rfc4880bis
 @opindex rfc4880bis
-Reset all packet, cipher and digest options to strict according to the
-proposed updates of RFC-4880.
+This option is obsolete; it is handled as an alias for @option{--gnupg}.
 
 @item --rfc2440
 @opindex rfc2440
-Reset all packet, cipher and digest options to strict RFC-2440
-behavior.  Note that by using this option encryption packets are
-created in a legacy mode without MDC protection.  This is dangerous
-and should thus only be used for experiments.  This option implies
-@option{--allow-old-cipher-algos}.  See also option
-@option{--ignore-mdc-error}.
+Set all packet, cipher and digest options to strict RFC-2440 behavior.
+RFC-2440 is a very old version of OpenPGP.  Note that by using this
+option encryption packets are created in a legacy mode without MDC
+protection.  This is dangerous and should thus only be used for
+experiments.  This option implies @option{--allow-old-cipher-algos}.
+See also option @option{--ignore-mdc-error}.
 
 @item --pgp6
 @opindex pgp6
-This option is obsolete; it is handled as an alias for @option{--pgp7}
+This option is obsolete; it is handled as an alias for @option{--pgp7}.
 
 @item --pgp7
 @opindex pgp7
@@ -3848,13 +3846,11 @@ absolute date in the form YYYY-MM-DD. Defaults to "0".
 @opindex default-new-key-algo @var{string}
 This option can be used to change the default algorithms for key
 generation. The @var{string} is similar to the arguments required for
-the command @option{--quick-add-key} but slightly different.  For
-example the current default of @code{"rsa2048/cert,sign+rsa2048/encr"}
-(or @code{"rsa3072"}) can be changed to the value of what we currently
-call future default, which is @code{"ed25519/cert,sign+cv25519/encr"}.
-You need to consult the source code to learn the details.  Note that
-the advanced key generation commands can always be used to specify a
-key algorithm directly.
+the command @option{--quick-add-key} but slightly different.  You need
+to consult the source code to learn the details.  Note that the
+advanced key generation commands can always be used to specify a key
+algorithm directly.  Setting a compliance mode will set or clear this
+flag, so it should only be used after a compliance mode setting.
 
 @item --no-auto-trust-new-key
 @opindex no-auto-trust-new-key
diff --git a/g10/gpg.c b/g10/gpg.c
index b5928963f..b64a65b5a 100644
--- a/g10/gpg.c
+++ b/g10/gpg.c
@@ -2284,6 +2284,7 @@ set_compliance_option (enum cmd_and_opt_values option)
       opt.s2k_digest_algo = 0;
       opt.s2k_cipher_algo = DEFAULT_CIPHER_ALGO;
       opt.flags.allow_old_cipher_algos = 0;
+      opt.def_new_key_algo = NULL;
       break;
     case oOpenPGP:
     case oRFC4880:
@@ -2298,6 +2299,7 @@ set_compliance_option (enum cmd_and_opt_values option)
       opt.s2k_digest_algo = DIGEST_ALGO_SHA1;
       opt.s2k_cipher_algo = CIPHER_ALGO_3DES;
       opt.flags.allow_old_cipher_algos = 1;
+      opt.def_new_key_algo = "rsa3072/cert,sign+rsa3072/encr";
       break;
     case oRFC2440:
       set_compliance_option (oGnuPG);
@@ -2310,6 +2312,7 @@ set_compliance_option (enum cmd_and_opt_values option)
       opt.s2k_digest_algo = DIGEST_ALGO_SHA1;
       opt.s2k_cipher_algo = CIPHER_ALGO_3DES;
       opt.flags.allow_old_cipher_algos = 1;
+      opt.def_new_key_algo = "rsa3072/cert,sign+rsa3072/encr";
       break;
     case oPGP7:
       set_compliance_option (oGnuPG);
diff --git a/g10/keygen.c b/g10/keygen.c
index 9b547ad23..0eacd610d 100644
--- a/g10/keygen.c
+++ b/g10/keygen.c
@@ -3577,6 +3577,15 @@ parse_key_parameter_part (ctrl_t ctrl,
   else
     return gpg_error (GPG_ERR_UNKNOWN_CURVE);
 
+  if ((RFC4880||RFC2440||PGP8||PGP7) &&
+      (algo != PUBKEY_ALGO_RSA) &&
+      (algo != PUBKEY_ALGO_DSA) &&
+      (algo != PUBKEY_ALGO_ELGAMAL_E)) {
+    log_error (_("Cannot generate pubkey algorithm \"%s\" in compliance mode: %s\n"),
+               string, gnupg_compliance_label (opt.compliance));
+    return gpg_error (GPG_ERR_UNKNOWN_ALGORITHM);
+  }
+
   /* Parse the flags.  */
   keyuse = 0;
   if (flags)