Conversation
There was an assumption that a certificate would be issued during the validity period of all certificates in its chain. If a certificate was issued such that its NotAfter timestamp was past the NotAfter of another certificate in the chain, that would have not been detected. This is because during verification, we use the leaf certificate's NotBefore timestamp to verify the chain's validity, but check only the leaf certificate's validity against any provided timestamps (either from the Rekor timestamp, a signed timestamp, or the current time). This scenario is not expected with a typical chain since a CA shouldn't issue a certificate that outlives an issuer. This change enforces that the entire chain is valid at any of those provided timestamps. Signed-off-by: Hayden <8418760+Hayden-IO@users.noreply.github.com>
steiza
approved these changes
Jan 23, 2026
steiza
left a comment
Member
There was a problem hiding this comment.
Oof. Nice work. We really need to move everything over to sigstore-go.
Contributor
Author
|
Yep, very much agreed. I verified this doesn't affect sigstore-go because of a more reasonable ordering - gather your timestamps, then verify the chain against those timestamps. |
piceri
pushed a commit
to piceri/cosign
that referenced
this pull request
Jan 29, 2026
There was an assumption that a certificate would be issued during the validity period of all certificates in its chain. If a certificate was issued such that its NotAfter timestamp was past the NotAfter of another certificate in the chain, that would have not been detected. This is because during verification, we use the leaf certificate's NotBefore timestamp to verify the chain's validity, but check only the leaf certificate's validity against any provided timestamps (either from the Rekor timestamp, a signed timestamp, or the current time). This scenario is not expected with a typical chain since a CA shouldn't issue a certificate that outlives an issuer. This change enforces that the entire chain is valid at any of those provided timestamps. Signed-off-by: Hayden <8418760+Hayden-IO@users.noreply.github.com>
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
There was an assumption that a certificate would be issued during the validity period of all certificates in its chain. If a certificate was issued such that its NotAfter timestamp was past the NotAfter of another certificate in the chain, that would have not been detected. This is because during verification, we use the leaf certificate's NotBefore timestamp to verify the chain's validity, but check only the leaf certificate's validity against any provided timestamps (either from the Rekor timestamp, a signed timestamp, or the current time).
This scenario is not expected with a typical chain since a CA shouldn't issue a certificate that outlives an issuer.
This change enforces that the entire chain is valid at any of those provided timestamps.
Summary
Release Note
Documentation