From 6a39ff038f5dc8534471b2f96c8341ea1a78508c Mon Sep 17 00:00:00 2001 From: Roberto Hueso Gomez Date: Thu, 30 Oct 2025 13:15:11 +0100 Subject: [PATCH] docs: Signatures expect a single signature packet Clarify that OpenPGP container signatures are expected to contain exactly one signature packet. This clarification is necessary because, according to RFC 4880, a "Signed Message" may contain a sequence of signature packets. This case might not be correctly handled by the existing verification software. Signed-off-by: Roberto Hueso Gomez --- image/docs/containers-signature.5.md | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/image/docs/containers-signature.5.md b/image/docs/containers-signature.5.md index be713c5077..b43c1ec9ce 100644 --- a/image/docs/containers-signature.5.md +++ b/image/docs/containers-signature.5.md @@ -67,10 +67,11 @@ When verifying a cryptographic signature in the OpenPGP format, the consumer MUST verify at least the following aspects of the signature (like the `go.podman.io/image/v5/signature` package does): -- The blob MUST be a “Signed Message” as defined RFC 4880 section 11.3. +- The blob MUST be a “Signed Message” as defined in RFC 4880 section 11.3. (e.g. it MUST NOT be an unsigned “Literal Message”, a “Cleartext Signature” as defined in RFC 4880 section 7, or any other non-signature format). +- The blob MUST NOT contain more than one "Signature Packet" as defined in RFC 4880 section 5.2. - The signature MUST have been made by an expected key trusted for the purpose (and the specific container image). - The signature MUST be correctly formed and pass the cryptographic validation. - The signature MUST correctly authenticate the included JSON payload