sigstore-js has Insufficient Verification of Data Authenticity

Description

sigstore-js derives a transparency-log timestamp from `tlogEntries[].integratedTime` and uses it to validate certificate validity windows and satisfy `timestampThreshold`. For bundle v0.2, a tlog entry can be inclusionProof-only (no signed inclusionPromise/set), and the inclusion proof path does not cryptographically bind `integratedTime`. As a result, an attacker who can supply an untrusted bundle can influence time-based verification decisions by choosing `integratedTime`. ## impact If a consumer accepts attacker-provided bundle v0.2 inputs and relies on tlog-derived timestamps for certificate validity checks, verification can be influenced by an unauthenticated timestamp value. This is a trust gap: `integratedTime` is treated as a trusted observer timestamp under inclusionProof-only mode even though only the signed inclusionPromise/set path binds it. ## affected code - `packages/verify/src/bundle/index.ts` (adds a transparency-log timestamp whenever `integratedTime != 0`) - `packages/verify/src/timestamp/index.ts` (converts `integratedTime` to a `Date`) - `packages/verify/src/verifier.ts` (verifies timestamps before verifying tlog inclusion) - `packages/verify/src/tlog/index.ts` + `packages/verify/src/tlog/set.ts` (only the inclusionPromise/set path binds `integratedTime`) ## proof of concept The attached `poc.zip` contains a self-contained harness that reproduces the behavior on the pinned commit and includes both a canonical test and a negative control. repro: 1) extract `poc.zip` into a fresh directory and run the make targets: ```bash unzip poc.zip -d poc cd poc/poc-F-SIG-JS-TLOGTIME-001 make canonical make control ``` 2) confirm `canonical.log` includes: ``` [CALLSITE_HIT]: [PROOF_MARKER]: ``` 3) confirm `control.log` includes: ``` [NC_MARKER]: ``` ## suggested fix Only treat `integratedTime` as a trusted timestamp when it is cryptographically bound (for example, via a verified signed inclusionPromise/set). For inclusionProof-only entries, do not count `integratedTime` toward `timestampThreshold`, and do not use it for certificate validity decisions unless there is another signed time source (for example, an rfc3161 timestamp). [poc.zip](https://github.com/user-attachments/files/25643656/poc.zip) [PR_DESCRIPTION.md](https://github.com/user-attachments/files/25643660/PR_DESCRIPTION.md) [SUBMISSION.md](https://github.com/user-attachments/files/25643662/SUBMISSION.md)

Affected Packages (1)