keyeddigest

Documentation

Overview

Package keyeddigest computes one thing: HMAC-SHA256 of a message under a caller-supplied key.

It exists because four sites derived the same construction independently — the repository id, the project-table match digest and the derived-name subkey (all in internal/config), plus the persisted scope digest (internal/record) — so a correction to it had to be applied and re-verified in four places, and nothing caught a site that drifted (ADR-0022).

It is deliberately domain-blind: it has no concept of a repository id, a scope or a salt, it reads and writes nothing, and it holds no state across calls. That is the whole basis on which ADR-0022 narrows ADR-0019 ("all access ... stays inside internal/config") and ADR-0020 ("record ... imports nothing from the repo") to admit it — a function that computes a digest and forgets its input is not a second place that can hold key material. A package variable, a pooled MAC state or a log line here would remove that justification.

It does not hex-encode and it does not truncate. Its callers disagree about both: one uses the raw bytes as a key, one hex-encodes without truncating, and two truncate to different widths. Encoding is the caller's decision.

Index

• func Sum(key, data []byte) []byte

Functions

func Sum

func Sum(key, data []byte) []byte

Sum returns the HMAC-SHA256 of data under key, as raw digest bytes.

hash.Hash's contract is that Write never returns an error. It is checked anyway — errcheck runs with check-blank, and there is no honest way to discard it — and a violation is the one outcome worth stopping the process for: it would return a digest over a prefix of data, so every id, table entry and persisted name written afterwards would be keyed to a value nothing else agrees with. The panic names the operation and nothing else: neither the key nor the data may reach a message (plan §3.4, §4.2).