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# jerboa-mail

Reusable email parsing and MIME helpers for Jerboa.

The initial scope is read-oriented:

- RFC 5322 header/body splitting.
- Header unfolding and lookup.
- RFC 2047 encoded-word decoding for common UTF-8/ASCII cases.
- Base64 and quoted-printable content-transfer decoding.
- Simple MIME parsing for text and multipart messages.
- Best-effort body selection for CLI mail readers.

Sending helpers can be added later, but this first version is intentionally
small and fixture-driven.

## Security posture

`jerboa-mail` parses hostile mail input and remains private/experimental until
the release gates in `SECURITY.md`, `docs/threat-model.md`, and
`docs/release-evidence.md` are complete.

The parser library is capability-free by design: it does not open files, call
the shell, use the network, load dynamic libraries, use FFI, or handle
credentials. The local security gate enforces that parser and test source keep
that shape.

Default parser limits are exported as parameters for callers that need tighter
deployment budgets:

Decoded HTML and MIME metadata are still hostile data. Callers that display
mail must follow `docs/rendering-policy.md`; this library does not sanitize HTML
or make body text safe for browser rendering.

- `mail-max-message-chars`: 25 MiB.
- `mail-max-header-chars`: 256 KiB.
- `mail-max-header-lines`: 4096.
- `mail-max-line-chars`: 64 KiB.
- `mail-max-transfer-encoded-chars`: 25 MiB.
- `mail-max-encoded-word-chars`: 64 KiB.
- `mail-max-mime-depth`: 16.
- `mail-max-mime-parts`: 1024 total nodes across the complete message tree,
  including the root, multipart containers, and leaves.
- `mail-max-mime-header-chars`: 4 MiB total across all MIME nodes.
- `mail-max-mime-decoded-chars`: 25 MiB total retained decoded/body text
  across all MIME leaves.
- `mail-max-boundary-chars`: 200.

## Development

```sh
make test
make corpus-smoke
make fuzz-evidence
make verify
make release-evidence
```

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