threads / patch / 64917

patchgpg-interface: Signatures by expired keys are fine

Subject: [PATCH v1] gpg-interface: Signatures by expired keys are fine

## tl;dr

6 messages between Feb 4, 2026 and Feb 5, 2026. Diffs are folded; open one to read it.

replies: 5people: 3as markdown or json

Uwe Kleine-König· Feb 4, 2026, 15:23 UTC · lore

If a signature is done with a valid key and that key later expires, the signature should still be considered good.

GnuPG exmits in this case something like:

	[GNUPG:] NEWSIG
	gpg: Signature made Wed 26 Nov 2014 05:56:50 AM CET
	gpg:                using RSA key FE3958F9067BC667
	[GNUPG:] KEYEXPIRED 1478449622
	[GNUPG:] KEY_CONSIDERED D783920D6D4F0C06AA4C25F3FE3958F9067BC667 0
	[GNUPG:] KEYEXPIRED 1478449622
	[GNUPG:] SIG_ID 8tAN3Fx6XB2NAoH5U8neoguQ9MI 2014-11-26 1416977810
	[GNUPG:] EXPKEYSIG FE3958F9067BC667 Jason Cooper <jason@lakedaemon.net>
	gpg: Good signature from "Jason Cooper <jason@lakedaemon.net>" [expired]
	[GNUPG:] VALIDSIG D783920D6D4F0C06AA4C25F3FE3958F9067BC667 2014-11-26 1416977810 0 4 0 1 2 00 D783920D6D4F0C06AA4C25F3FE3958F9067BC667
	gpg: Note: This key has expired!
	      D783920D6D4F0C06AA4C25F3FE3958F9067BC667

(signature and signed data in this example is taken from Linux commit 756f80cee766574ae282baa97fdcf9cc). So GnuPG is relaxed and the fact that the key is expired is only worth a "Note" which is weaker than e.g.

	gpg: WARNING: The key's User ID is not certified with a trusted signature!
	gpg:          There is no indication that the signature belongs to the owner.

which git still considers ok.

So stop coloring the signature by an expired key red and handle it like any other good signature.

Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>
---
Hello,

the motivation for this patch originates from a mail correspondence with Linus Torvalds, see https://lore.kernel.org/ksummit/CAHC9VhRwMpSCphW_FsHojX1r12D5MOMUBm6MAzpGYD_FDjEVtA@mail.gmail.com/T/#m6cc3cc4b599658cab6012326993a1261fd641046 for the details.

Best regards Uwe

 gpg-interface.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Show changes to gpg-interface.c +2 −2

diff --git a/gpg-interface.c b/gpg-interface.c
index 47222bf31b6e..6635c6c8e16f 100644
--- a/gpg-interface.c
+++ b/gpg-interface.c
@@ -382,7 +382,7 @@ static int verify_gpg_signed_buffer(struct signature_check *sigc,
 
 	delete_tempfile(&temp);
 
-	ret |= !strstr(gpg_stdout.buf, "\n[GNUPG:] GOODSIG ");
+	ret |= !strstr(gpg_stdout.buf, "\n[GNUPG:] GOODSIG ") && !strstr(gpg_stdout.buf, "\n[GNUPG:] EXPKEYSIG ");
 	sigc->output = strbuf_detach(&gpg_stderr, NULL);
 	sigc->gpg_status = strbuf_detach(&gpg_stdout, NULL);
 
@@ -680,7 +680,7 @@ int check_signature(struct signature_check *sigc,
 	if (status && !sigc->output)
 		return !!status;
 
-	status |= sigc->result != 'G';
+	status |= sigc->result != 'G' && sigc->result != 'Y';
 	status |= sigc->trust_level < configured_min_trust_level;
 
 	return !!status;

base-commit: b2826b52eb7caff9f4ed6e85ec45e338bf02ad09

-- 
2.47.3

Neal H. Walfield· Feb 4, 2026, 15:35 UTC · re: Uwe Kleine-König · lore

Re: [PATCH v1] gpg-interface: Signatures by expired keys are fine

Hi,

I think this change is an improvement over the status quo. In my opinion, a signature should be accepted if it was made when the certificate sas not expired. If the signature was made after the certificate expired it should be rejected. That is:

  t_s1: signature 1
  t_e: certificate expires
  t_s2: signature 2

  where: t_s1 < t_e < t_s2

signature 1 should be accepted as t_s1 < t_e.

signature 2 should be rejected as t_s2 > t_e.

As GnuPG's interface does not provide enough information to make this distinction, this change is better.

:) Neal

On Wed, 04 Feb 2026 16:23:06 +0100, Uwe Kleine-König wrote:

Show 74 quoted lines

> 
> If a signature is done with a valid key and that key later expires, the
> signature should still be considered good.
> 
> GnuPG exmits in this case something like:
> 
> 	[GNUPG:] NEWSIG
> 	gpg: Signature made Wed 26 Nov 2014 05:56:50 AM CET
> 	gpg:                using RSA key FE3958F9067BC667
> 	[GNUPG:] KEYEXPIRED 1478449622
> 	[GNUPG:] KEY_CONSIDERED D783920D6D4F0C06AA4C25F3FE3958F9067BC667 0
> 	[GNUPG:] KEYEXPIRED 1478449622
> 	[GNUPG:] SIG_ID 8tAN3Fx6XB2NAoH5U8neoguQ9MI 2014-11-26 1416977810
> 	[GNUPG:] EXPKEYSIG FE3958F9067BC667 Jason Cooper <jason@lakedaemon.net>
> 	gpg: Good signature from "Jason Cooper <jason@lakedaemon.net>" [expired]
> 	[GNUPG:] VALIDSIG D783920D6D4F0C06AA4C25F3FE3958F9067BC667 2014-11-26 1416977810 0 4 0 1 2 00 D783920D6D4F0C06AA4C25F3FE3958F9067BC667
> 	gpg: Note: This key has expired!
> 	      D783920D6D4F0C06AA4C25F3FE3958F9067BC667
> 
> (signature and signed data in this example is taken from Linux commit
> 756f80cee766574ae282baa97fdcf9cc). So GnuPG is relaxed and the fact that
> the key is expired is only worth a "Note" which is weaker than e.g.
> 
> 	gpg: WARNING: The key's User ID is not certified with a trusted signature!
> 	gpg:          There is no indication that the signature belongs to the owner.
> 
> which git still considers ok.
> 
> So stop coloring the signature by an expired key red and handle it like
> any other good signature.
> 
> Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>
> ---
> Hello,
> 
> the motivation for this patch originates from a mail correspondence with Linus Torvalds,
> see
> https://lore.kernel.org/ksummit/CAHC9VhRwMpSCphW_FsHojX1r12D5MOMUBm6MAzpGYD_FDjEVtA@mail.gmail.com/T/#m6cc3cc4b599658cab6012326993a1261fd641046
> for the details.
> 
> Best regards
> Uwe
> 
>  gpg-interface.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/gpg-interface.c b/gpg-interface.c
> index 47222bf31b6e..6635c6c8e16f 100644
> --- a/gpg-interface.c
> +++ b/gpg-interface.c
> @@ -382,7 +382,7 @@ static int verify_gpg_signed_buffer(struct signature_check *sigc,
>  
>  	delete_tempfile(&temp);
>  
> -	ret |= !strstr(gpg_stdout.buf, "\n[GNUPG:] GOODSIG ");
> +	ret |= !strstr(gpg_stdout.buf, "\n[GNUPG:] GOODSIG ") && !strstr(gpg_stdout.buf, "\n[GNUPG:] EXPKEYSIG ");
>  	sigc->output = strbuf_detach(&gpg_stderr, NULL);
>  	sigc->gpg_status = strbuf_detach(&gpg_stdout, NULL);
>  
> @@ -680,7 +680,7 @@ int check_signature(struct signature_check *sigc,
>  	if (status && !sigc->output)
>  		return !!status;
>  
> -	status |= sigc->result != 'G';
> +	status |= sigc->result != 'G' && sigc->result != 'Y';
>  	status |= sigc->trust_level < configured_min_trust_level;
>  
>  	return !!status;
> 
> base-commit: b2826b52eb7caff9f4ed6e85ec45e338bf02ad09
> -- 
> 2.47.3
> 
>

Junio C Hamano· Feb 4, 2026, 17:26 UTC · re: Uwe Kleine-König · lore

Re: [PATCH v1] gpg-interface: Signatures by expired keys are fine

Uwe Kleine-König <ukleinek@kernel.org> writes:

> If a signature is done with a valid key and that key later expires, the
> signature should still be considered good.
>
> GnuPG exmits in this case something like:

"emits".

Show 10 quoted lines

> diff --git a/gpg-interface.c b/gpg-interface.c
> index 47222bf31b6e..6635c6c8e16f 100644
> --- a/gpg-interface.c
> +++ b/gpg-interface.c
> @@ -382,7 +382,7 @@ static int verify_gpg_signed_buffer(struct signature_check *sigc,
>  
>  	delete_tempfile(&temp);
>  
> -	ret |= !strstr(gpg_stdout.buf, "\n[GNUPG:] GOODSIG ");
> +	ret |= !strstr(gpg_stdout.buf, "\n[GNUPG:] GOODSIG ") && !strstr(gpg_stdout.buf, "\n[GNUPG:] EXPKEYSIG ");

Makes sense; I'll wrap this overlong line while queuing, though.

Show 14 quoted lines

>  	sigc->output = strbuf_detach(&gpg_stderr, NULL);
>  	sigc->gpg_status = strbuf_detach(&gpg_stdout, NULL);
>  
> @@ -680,7 +680,7 @@ int check_signature(struct signature_check *sigc,
>  	if (status && !sigc->output)
>  		return !!status;
>  
> -	status |= sigc->result != 'G';
> +	status |= sigc->result != 'G' && sigc->result != 'Y';
>  	status |= sigc->trust_level < configured_min_trust_level;
>  
>  	return !!status;
>
> base-commit: b2826b52eb7caff9f4ed6e85ec45e338bf02ad09

Uwe Kleine-König· Feb 4, 2026, 21:18 UTC · re: Junio C Hamano · lore

Re: [PATCH v1] gpg-interface: Signatures by expired keys are fine

Hello,

On Wed, Feb 04, 2026 at 09:26:09AM -0800, Junio C Hamano wrote:

Show 21 quoted lines

> Uwe Kleine-König <ukleinek@kernel.org> writes:
> 
> > If a signature is done with a valid key and that key later expires, the
> > signature should still be considered good.
> >
> > GnuPG exmits in this case something like:
> 
> "emits".
> 
> > diff --git a/gpg-interface.c b/gpg-interface.c
> > index 47222bf31b6e..6635c6c8e16f 100644
> > --- a/gpg-interface.c
> > +++ b/gpg-interface.c
> > @@ -382,7 +382,7 @@ static int verify_gpg_signed_buffer(struct signature_check *sigc,
> >  
> >  	delete_tempfile(&temp);
> >  
> > -	ret |= !strstr(gpg_stdout.buf, "\n[GNUPG:] GOODSIG ");
> > +	ret |= !strstr(gpg_stdout.buf, "\n[GNUPG:] GOODSIG ") && !strstr(gpg_stdout.buf, "\n[GNUPG:] EXPKEYSIG ");
> 
> Makes sense; I'll wrap this overlong line while queuing, though.

Just to be sure: That means I don't resent with the typo fixed and an additional line break and you care to apply this patch?

Thanks Uwe

Junio C Hamano· Feb 4, 2026, 21:27 UTC · re: Uwe Kleine-König · lore

Re: [PATCH v1] gpg-interface: Signatures by expired keys are fine

Uwe Kleine-König <ukleinek@kernel.org> writes:

Show 27 quoted lines

> Hello,
>
> On Wed, Feb 04, 2026 at 09:26:09AM -0800, Junio C Hamano wrote:
>> Uwe Kleine-König <ukleinek@kernel.org> writes:
>> 
>> > If a signature is done with a valid key and that key later expires, the
>> > signature should still be considered good.
>> >
>> > GnuPG exmits in this case something like:
>> 
>> "emits".
>> 
>> > diff --git a/gpg-interface.c b/gpg-interface.c
>> > index 47222bf31b6e..6635c6c8e16f 100644
>> > --- a/gpg-interface.c
>> > +++ b/gpg-interface.c
>> > @@ -382,7 +382,7 @@ static int verify_gpg_signed_buffer(struct signature_check *sigc,
>> >  
>> >  	delete_tempfile(&temp);
>> >  
>> > -	ret |= !strstr(gpg_stdout.buf, "\n[GNUPG:] GOODSIG ");
>> > +	ret |= !strstr(gpg_stdout.buf, "\n[GNUPG:] GOODSIG ") && !strstr(gpg_stdout.buf, "\n[GNUPG:] EXPKEYSIG ");
>> 
>> Makes sense; I'll wrap this overlong line while queuing, though.
>
> Just to be sure: That means I don't resent with the typo fixed and an
> additional line break and you care to apply this patch?

Unless there are other things you want to update, no need to resend.

FYI, here is what I queued.

---- >8 ----
From: Uwe Kleine-König <ukleinek@kernel.org>
Date: Wed, 4 Feb 2026 16:23:06 +0100
Subject: [PATCH] gpg-interface: signatures by expired keys are fine

If a signature is made with a valid key and that key later expires, the signature should still be considered good.

GnuPG emits in this case something like:

	[GNUPG:] NEWSIG
	gpg: Signature made Wed 26 Nov 2014 05:56:50 AM CET
	gpg:                using RSA key FE3958F9067BC667
	[GNUPG:] KEYEXPIRED 1478449622
	[GNUPG:] KEY_CONSIDERED D783920D6D4F0C06AA4C25F3FE3958F9067BC667 0
	[GNUPG:] KEYEXPIRED 1478449622
	[GNUPG:] SIG_ID 8tAN3Fx6XB2NAoH5U8neoguQ9MI 2014-11-26 1416977810
	[GNUPG:] EXPKEYSIG FE3958F9067BC667 Jason Cooper <jason@lakedaemon.net>
	gpg: Good signature from "Jason Cooper <jason@lakedaemon.net>" [expired]
	[GNUPG:] VALIDSIG D783920D6D4F0C06AA4C25F3FE3958F9067BC667 2014-11-26 1416977810 0 4 0 1 2 00 D783920D6D4F0C06AA4C25F3FE3958F9067BC667
	gpg: Note: This key has expired!
	      D783920D6D4F0C06AA4C25F3FE3958F9067BC667

	gpg: WARNING: The key's User ID is not certified with a trusted signature!
	gpg:          There is no indication that the signature belongs to the owner.

which git still considers ok.

So stop coloring the signature by an expired key red and handle it like any other good signature.

Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 gpg-interface.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

Show changes to gpg-interface.c +3 −2

diff --git a/gpg-interface.c b/gpg-interface.c
index 47222bf31b..5a58f333df 100644
--- a/gpg-interface.c
+++ b/gpg-interface.c
@@ -382,7 +382,8 @@ static int verify_gpg_signed_buffer(struct signature_check *sigc,
 
 	delete_tempfile(&temp);
 
-	ret |= !strstr(gpg_stdout.buf, "\n[GNUPG:] GOODSIG ");
+	ret |= !strstr(gpg_stdout.buf, "\n[GNUPG:] GOODSIG ") &&
+	       !strstr(gpg_stdout.buf, "\n[GNUPG:] EXPKEYSIG ");
 	sigc->output = strbuf_detach(&gpg_stderr, NULL);
 	sigc->gpg_status = strbuf_detach(&gpg_stdout, NULL);
 
@@ -680,7 +681,7 @@ int check_signature(struct signature_check *sigc,
 	if (status && !sigc->output)
 		return !!status;
 
-	status |= sigc->result != 'G';
+	status |= sigc->result != 'G' && sigc->result != 'Y';
 	status |= sigc->trust_level < configured_min_trust_level;
 
 	return !!status;

-- 
2.53.0-169-ga09cd4eb64

Uwe Kleine-König· Feb 5, 2026, 09:38 UTC · re: Junio C Hamano · lore

Re: [PATCH v1] gpg-interface: Signatures by expired keys are fine

Hello Junio,

On Wed, Feb 04, 2026 at 01:27:06PM -0800, Junio C Hamano wrote:

Show 17 quoted lines

> Uwe Kleine-König <ukleinek@kernel.org> writes:
> > On Wed, Feb 04, 2026 at 09:26:09AM -0800, Junio C Hamano wrote:
> >> Makes sense; I'll wrap this overlong line while queuing, though.
> >
> > Just to be sure: That means I don't resent with the typo fixed and an
> > additional line break and you care to apply this patch?
> 
> Unless there are other things you want to update, no need to resend.
> 
> FYI, here is what I queued.
> 
> ---- >8 ----
> From: Uwe Kleine-König <ukleinek@kernel.org>
> Date: Wed, 4 Feb 2026 16:23:06 +0100
> Subject: [PATCH] gpg-interface: signatures by expired keys are fine
> 
> [...]

LGTM, thanks!

Best regards Uwe