Date:   Thu, 22 Dec 2022 20:02:05 +0700
From:   Bagas Sanjaya <bagasdotme@...il.com>
To:     Konstantin Ryabitsev <konstantin@...uxfoundation.org>
Cc:     Jonathan Corbet <corbet@....net>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] docs: maintainer-pgp-guide: update for latest gnupg
 defaults

On Tue, Dec 20, 2022 at 02:44:17PM -0500, Konstantin Ryabitsev wrote:
> It is finally becoming increasingly rare to find a distribution that
> still ships with gnupg-1.x, so remove the last vestiges of "gpg" vs
> "gpg2" from documentation.
> 
> Similarly, starting with GnuPG 2.2 and above, the default --gen-key
> operation creates ed25519/cv25519 keypairs, so update all example
> command outputs to use that combination instead of rsa2048.
> 
> Lastly, add a few wording tweaks and remove links that lead to stale
> information (e.g. hardware tokens overview from 2017).
> 

Shouldn't "Protecting Code Integrity" doc also be updated with recent
situation?

> Signed-off-by: Konstantin Ryabitsev <konstantin@...uxfoundation.org>
> ---
>  Documentation/process/maintainer-pgp-guide.rst | 102 ++++++++-----------------
>  1 file changed, 30 insertions(+), 72 deletions(-)
> 
> diff --git a/Documentation/process/maintainer-pgp-guide.rst b/Documentation/process/maintainer-pgp-guide.rst
> index 40bfbd3b7648..f5277993b195 100644
> --- a/Documentation/process/maintainer-pgp-guide.rst
> +++ b/Documentation/process/maintainer-pgp-guide.rst
> @@ -60,36 +60,18 @@ establish the integrity of the Linux kernel itself.
>  PGP tools
>  =========
>  
> -Use GnuPG v2
> -------------
> +Use GnuPG 2.2 or later
> +----------------------
>  
>  Your distro should already have GnuPG installed by default, you just
> -need to verify that you are using version 2.x and not the legacy 1.4
> -release -- many distributions still package both, with the default
> -``gpg`` command invoking GnuPG v.1. To check, run::
> +need to verify that you are using a reasonably recent version of it.
> +To check, run::
>  
>      $ gpg --version | head -n1
>  
> -If you see ``gpg (GnuPG) 1.4.x``, then you are using GnuPG v.1. Try the
> -``gpg2`` command (if you don't have it, you may need to install the
> -gnupg2 package)::
> -
> -    $ gpg2 --version | head -n1
> -
> -If you see ``gpg (GnuPG) 2.x.x``, then you are good to go. This guide
> -will assume you have the version 2.2 of GnuPG (or later). If you are
> -using version 2.0 of GnuPG, then some of the commands in this guide will
> -not work, and you should consider installing the latest 2.2 version of
> -GnuPG. Versions of gnupg-2.1.11 and later should be compatible for the
> -purposes of this guide as well.
> -
> -If you have both ``gpg`` and ``gpg2`` commands, you should make sure you
> -are always using GnuPG v2, not the legacy version. You can enforce this
> -by setting the appropriate alias::
> -
> -    $ alias gpg=gpg2
> -
> -You can put that in your ``.bashrc`` to make sure it's always the case.
> +If you have version 2.2 or above, then you are good to go. If you have a
> +version that is prior than 2.2, then some commands from this guide may
> +not work.
>  
>  Configure gpg-agent options
>  ~~~~~~~~~~~~~~~~~~~~~~~~~~~
> @@ -150,9 +132,9 @@ PGP defines four capabilities that a key can have:
>  The key with the **[C]** capability is often called the "master" key,
>  but this terminology is misleading because it implies that the Certify
>  key can be used in place of any of other subkey on the same chain (like
> -a physical "master key" can be used to open the locks made for other
> -keys). Since this is not the case, this guide will refer to it as "the
> -Certify key" to avoid any ambiguity.
> +a physical "master key" can be used to open locks made for other keys).
> +Since this is not the case, this guide will refer to it as "the Certify
> +key" to avoid any ambiguity.
>  
>  It is critical to fully understand the following:
>  
> @@ -186,10 +168,10 @@ If you used the default parameters when generating your key, then that
>  is what you will have. You can verify by running ``gpg --list-secret-keys``,
>  for example::
>  
> -    sec   rsa2048 2018-01-23 [SC] [expires: 2020-01-23]
> +    sec   ed25519 2022-12-20 [SC] [expires: 2024-12-19]
>            000000000000000000000000AAAABBBBCCCCDDDD
>      uid           [ultimate] Alice Dev <adev@...nel.org>
> -    ssb   rsa2048 2018-01-23 [E] [expires: 2020-01-23]
> +    ssb   cv25519 2022-12-20 [E] [expires: 2024-12-19]
>  
>  The long line under the ``sec`` entry is your key fingerprint --
>  whenever you see ``[fpr]`` in the examples below, that 40-character
> @@ -219,18 +201,9 @@ separate signing subkey::
>  
>  .. note:: ECC support in GnuPG
>  
> -    GnuPG 2.1 and later has full support for Elliptic Curve
> -    Cryptography, with ability to combine ECC subkeys with traditional
> -    RSA keys. The main upside of ECC cryptography is that it is much
> -    faster computationally and creates much smaller signatures when
> -    compared byte for byte with 2048+ bit RSA keys. Unless you plan on
> -    using a smartcard device that does not support ECC operations, we
> -    recommend that you create an ECC signing subkey for your kernel
> -    work.
> -
> -    Note, that if you plan to use a hardware device that does not
> +    Note, that if you intend to use a hardware token that does not
>      support ED25519 ECC keys, you should choose "nistp256" instead or
> -    "ed25519."
> +    "ed25519." See the section below on recommended hardware devices.
>  
>  
>  Back up your Certify key for disaster recovery
> @@ -336,13 +309,13 @@ First, identify the keygrip of your Certify key::
>  
>  The output will be something like this::
>  
> -    pub   rsa2048 2018-01-24 [SC] [expires: 2020-01-24]
> +    pub   ed25519 2022-12-20 [SC] [expires: 2022-12-19]
>            000000000000000000000000AAAABBBBCCCCDDDD
>            Keygrip = 1111000000000000000000000000000000000000
>      uid           [ultimate] Alice Dev <adev@...nel.org>
> -    sub   rsa2048 2018-01-24 [E] [expires: 2020-01-24]
> +    sub   cv25519 2022-12-20 [E] [expires: 2022-12-19]
>            Keygrip = 2222000000000000000000000000000000000000
> -    sub   ed25519 2018-01-24 [S]
> +    sub   ed25519 2022-12-20 [S]
>            Keygrip = 3333000000000000000000000000000000000000
>  
>  Find the keygrip entry that is beneath the ``pub`` line (right under the
> @@ -365,14 +338,14 @@ Now, if you issue the ``--list-secret-keys`` command, it will show that
>  the Certify key is missing (the ``#`` indicates it is not available)::
>  
>      $ gpg --list-secret-keys
> -    sec#  rsa2048 2018-01-24 [SC] [expires: 2020-01-24]
> +    sec#  ed25519 2022-12-20 [SC] [expires: 2024-12-19]
>            000000000000000000000000AAAABBBBCCCCDDDD
>      uid           [ultimate] Alice Dev <adev@...nel.org>
> -    ssb   rsa2048 2018-01-24 [E] [expires: 2020-01-24]
> -    ssb   ed25519 2018-01-24 [S]
> +    ssb   cv25519 2022-12-20 [E] [expires: 2024-12-19]
> +    ssb   ed25519 2022-12-20 [S]
>  
>  You should also remove any ``secring.gpg`` files in the ``~/.gnupg``
> -directory, which are left over from earlier versions of GnuPG.
> +directory, which may be left over from previous versions of GnuPG.
>  
>  If you don't have the "private-keys-v1.d" directory
>  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> @@ -437,8 +410,7 @@ functionality. There are several options available:
>    U2F, among others, and now finally supports NISTP and ED25519 ECC
>    keys.
>  
> -`LWN has a good review`_ of some of the above models, as well as several
> -others. Your choice will depend on cost, shipping availability in your
> +Your choice will depend on cost, shipping availability in your
>  geographical region, and open/proprietary hardware considerations.
>  
>  .. note::
> @@ -451,7 +423,6 @@ geographical region, and open/proprietary hardware considerations.
>  .. _`Nitrokey Pro 2`: https://shop.nitrokey.com/shop/product/nkpr2-nitrokey-pro-2-3
>  .. _`Yubikey 5`: https://www.yubico.com/products/yubikey-5-overview/
>  .. _Gnuk: https://www.fsij.org/doc-gnuk/
> -.. _`LWN has a good review`: https://lwn.net/Articles/736231/
>  .. _`qualify for a free Nitrokey Start`: https://www.kernel.org/nitrokey-digital-tokens-for-kernel-developers.html
>  
>  Configure your smartcard device
> @@ -509,11 +480,11 @@ passphrase and the admin PIN of the card for most operations::
>  
>      Secret subkeys are available.
>  
> -    pub  rsa2048/AAAABBBBCCCCDDDD
> -         created: 2018-01-23  expires: 2020-01-23  usage: SC
> +    pub  ed25519/AAAABBBBCCCCDDDD
> +         created: 2022-12-20  expires: 2024-12-19  usage: SC
>           trust: ultimate      validity: ultimate
> -    ssb  rsa2048/1111222233334444
> -         created: 2018-01-23  expires: never       usage: E
> +    ssb  cv25519/1111222233334444
> +         created: 2022-12-20  expires: never       usage: E
>      ssb  ed25519/5555666677778888
>           created: 2017-12-07  expires: never       usage: S
>      [ultimate] (1). Alice Dev <adev@...nel.org>
> @@ -577,11 +548,11 @@ If you perform ``--list-secret-keys`` now, you will see a subtle
>  difference in the output::
>  
>      $ gpg --list-secret-keys
> -    sec#  rsa2048 2018-01-24 [SC] [expires: 2020-01-24]
> +    sec#  ed25519 2022-12-20 [SC] [expires: 2024-12-19]
>            000000000000000000000000AAAABBBBCCCCDDDD
>      uid           [ultimate] Alice Dev <adev@...nel.org>
> -    ssb>  rsa2048 2018-01-24 [E] [expires: 2020-01-24]
> -    ssb>  ed25519 2018-01-24 [S]
> +    ssb>  cv25519 2022-12-20 [E] [expires: 2024-12-19]
> +    ssb>  ed25519 2022-12-20 [S]
>  
>  The ``>`` in the ``ssb>`` output indicates that the subkey is only
>  available on the smartcard. If you go back into your secret keys
> @@ -644,7 +615,7 @@ run::
>  You can also use a specific date if that is easier to remember (e.g.
>  your birthday, January 1st, or Canada Day)::
>  
> -    $ gpg --quick-set-expire [fpr] 2020-07-01
> +    $ gpg --quick-set-expire [fpr] 2025-07-01
>  
>  Remember to send the updated key back to keyservers::
>  
> @@ -707,12 +678,6 @@ should be used (``[fpr]`` is the fingerprint of your key)::
>  
>      $ git config --global user.signingKey [fpr]
>  
> -**IMPORTANT**: If you have a distinct ``gpg2`` command, then you should
> -tell git to always use it instead of the legacy ``gpg`` from version 1::
> -
> -    $ git config --global gpg.program gpg2
> -    $ git config --global gpgv.program gpgv2
> -
>  How to work with signed tags
>  ----------------------------
>  
> @@ -751,13 +716,6 @@ If you are verifying someone else's git tag, then you will need to
>  import their PGP key. Please refer to the
>  ":ref:`verify_identities`" section below.
>  
> -.. note::
> -
> -    If you get "``gpg: Can't check signature: unknown pubkey
> -    algorithm``" error, you need to tell git to use gpgv2 for
> -    verification, so it properly processes signatures made by ECC keys.
> -    See instructions at the start of this section.
> -
>  Configure git to always sign annotated tags
>  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>  
> 

LGTM, thanks.

Reviewed-by: Bagas Sanjaya <bagasdotme@...il.com>

-- 
An old man doll... just what I always wanted! - Clara

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