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

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

[Uwe Kleine-König]

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

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

[Neal H. Walfield]

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:
> 
> 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
> 
> 

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

[Junio C Hamano]

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.

>  	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

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

[Uwe Kleine-König]

[-- Attachment #1: Type: text/plain, Size: 1006 bytes --]

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?

Thanks
Uwe

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

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

[Junio C Hamano]

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

> 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

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

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

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

[Uwe Kleine-König]

[-- Attachment #1: Type: text/plain, Size: 753 bytes --]

Hello Junio,

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

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]