Alberto Bertogli 3b0836f811 dkim: When signing, process repeated headers from bottom to top ...

When signing repeated headers, today we hash each instance of a header
from top to bottom.

However, RFC 6376 section 5.4.2 is clear they should be processed bottom
to top, and this is also what our verifier (correctly) expects.

The bug causes our signatures to be (wrongly) invalid for messages that
have repeated signed headers with different values.

Note that repeated headers that are not signed (e.g. Received:) are not
problematic. This only affects headers we sign, like To:, From:,
Subject:.

This patch fixes the problem by adjusting the order in which Sign
processes repeated headers.

This bug was found by fuzzing the sign-verify cycle, which will be added
in a later patch.

2026-10-09 21:34:17 +01:00

..

testdata

dkim: Update .gitignore pattern for private test cases

2024-04-21 11:08:08 +01:00

canonicalize_test.go

dkim: Implement internal dkim signing and verification

2024-03-12 20:43:21 +00:00

canonicalize.go

cleanup: Remove unused/unnecessary code

2024-12-01 22:03:47 +00:00

context_test.go

test: Use modern testing features instead of custom helpers

2026-10-03 10:34:35 +01:00

context.go

Apply go fix to simplify using modern features

2026-10-02 18:34:25 +01:00

dns_test.go

test: Use modern testing features instead of custom helpers

2026-10-03 10:34:35 +01:00

dns.go

Apply go fix to simplify using modern features

2026-10-02 18:34:25 +01:00

file_test.go

test: Use modern testing features instead of custom helpers

2026-10-03 10:34:35 +01:00

header_test.go

dkim: Fix work amplification on h= tag processing

2026-10-09 21:34:10 +01:00

header.go

dkim: Fix work amplification on h= tag processing

2026-10-09 21:34:10 +01:00

message_test.go

dkim: Messages without a blank line should have an empty body

2026-10-09 21:34:17 +01:00

message.go

dkim: Messages without a blank line should have an empty body

2026-10-09 21:34:17 +01:00

sign_test.go

dkim: When signing, process repeated headers from bottom to top

2026-10-09 21:34:17 +01:00

sign.go

dkim: When signing, process repeated headers from bottom to top

2026-10-09 21:34:17 +01:00

verify_test.go

dkim: Fix work amplification on h= tag processing

2026-10-09 21:34:10 +01:00

verify.go

dkim: Fix work amplification on h= tag processing

2026-10-09 21:34:10 +01:00