0011: The report carries signing time and certificate validity

Status: accepted, implemented.

Context

Data\SignatureDetails carried verified, signers, coverageEnd, coversWholeDocument, isTimestamp and error. It answered "do these bytes match this CMS" and nothing about when.

The question a legal or compliance reader actually asks is "was the certificate valid at the moment it signed?", and the report could not answer it. Neither could it answer "when was this signed", which poppler prints from the same document:

- Signing Time: Aug 09 2026 12:01:52

The data was in the document the whole time. It simply was not surfaced.

Decision

SignatureDetails gains signedAt. Data\Signer already carried validFrom and validTo, so only the time was missing. From the two, a derived answer:

$signature->signedAt;                  // ?int, unix timestamp, null when absent
$signature->signerWasValidWhenSigned(); // ?bool, null when either date is unknown

null rather than false when the answer is unknown. A signature with no recorded time is not a signature made outside the validity window, and collapsing the two would report an absence as a violation. The caller decides what to do with not-knowing.

Where the time comes from, and a correction

This record first said the time would be read from the PKCS#9 signing-time signed attribute, OID 1.2.840.113549.1.9.5. That was wrong, and measuring said so: the attribute is absent from the CMS of a freshly signed document, because tc-lib-pdf-sign does not emit it.

The time is read from /M in the signature dictionary instead, which is what this package writes and what poppler reports as the signing time.

That location is better than it sounds. /M sits inside the byte range the signature covers, so altering it breaks the signature, where an unsigned attribute could be edited freely. It is still the signer's own clock.

One practical trap, recorded because it cost a debugging round: /M is written after /Contents, whose placeholder is 16 KB of hex, so it is roughly 16 KB past the /ByteRange rather than just ahead of it. The sibling that reads /SubFilter looks backwards from the same offset and works; a reader for /M that copies that shape finds nothing.

Consequences

• Data\SignatureDetails is a public return type, so adding a property changes the public shape. Minor release. The parameter is optional and last, so positional construction by a consumer keeps working.
• The signing time is not proof. It is the signer's own clock unless the signature carries an RFC 3161 timestamp, which is exactly what pades-b-t and above add. The docblock says so, and signerWasValidWhenSigned() is documented as answering the question the claimed time implies rather than a proven one. Making it provable is 0010.
• No network access is added. Everything here is read from bytes already in the document.