Changes for version 0.22 - 2026-10-18
- Message hashes (every Message-Instance's header and body hashes) go through the new Mail::DKIM2::Digest: OpenSSL's SHA-2, through Net::SSLeay, when that is installed (recommended, not required), else CryptX's as before. The digests are the same; OpenSSL uses the CPU's SHA instructions where there are some -- about 7 times CryptX's speed on an Apple M-series, 1.8 times on an older x86.
- The body is hashed where it lies, in whole runs, with fewer copies: load() normalises line endings only when there is a bare LF and never changes the caller's string; PRINT hands body chunks straight to the Verifier's body plan.
- The Verifier checks the Message-Instance chain without rebuilding any previous version of the message. New: Mail::DKIM2::BodyPlan composes the body Recipes into, for each instance, the runs of current body lines and Recipe literals its body was, and hashes every instance's body in one pass as the body arrives; the body is not kept. New: Mail::DKIM2::HeaderPlan does the same for header fields, canonicalizing each hashed value once. Same verdicts, in the same words; about 40% less time on list mail, all of it in the chain check. Verifier option StreamBody (on by default); 0 is the undo walk.
- DKIM2Verify keeps a copy of the body only when it builds something from it (a snapshot, or a first Message-Instance).
- The Verifier sends for every signature's public key, all at once and in the background (Net::DNS bgsend), as soon as it has the header fields, and reads the answers when it checks the signatures; an answer that settles nothing (none within 5 seconds, SERVFAIL) is asked again with query(). Each key name is looked up once per message. A chain of five signing domains verified about four times faster against live DNS.
- dkim2-milter verifies as the message arrives (headers at end of headers, then each body chunk), so the key lookups overlap the body's transfer.
- MessageInstance->verify takes BodyHashes, body hashes computed elsewhere.
- Behaviour change: a body Recipe may copy the body's trailing blank lines. They are not hashed (spec-06 section 6.1), but they are lines, as C, Go, Python and the browser verifier already number them; undo used to stop counting at the last non-blank line and refuse such a copy.
Documentation
Standalone DKIM2 milter for Postfix
Modules
DKIM2 signing and verification for email
every Message-Instance's body hash in one pass
Canonicalization, hashing, folding and key handling for DKIM2
DKIM2-signed Delivery Status Notifications
SHA-2 over message content, by OpenSSL where it can
decide whether a front end may sign a message
Streaming message parser base for Signer and Verifier
every Message-Instance's header hash without undo
Compute, verify and undo Message-Instance headers
Keep message snapshots keyed by Message-Instance
verify-and-reflect DKIM2 demonstration logic for dkim2.com
One DKIM2-Signature header, parsed or under construction
Sign a message with a DKIM2-Signature header
Bcc-safe recipient grouping before DKIM2 signing
The tag=value list a DKIM2 header is made of
structured per-level DKIM2 and Message-Instance report
Verify the DKIM2-Signature chain on a message
wrap a single-part message in a one-part multipart/mixed
Handler class for DKIM2 signing
Handler class for DKIM2 signature verification