# `Cmsex.PEM`
[🔗](https://github.com/openspb/cmsex/blob/v0.1.0/lib/cmsex/pem.ex#L1)

The textual encoding of CMS messages (RFC 7468): Base64 between
`-----BEGIN CMS-----` and `-----END CMS-----` lines.

RFC 7468 gives two labels: `CMS` (section 9) and `PKCS7` (section 8), the
older one, which more tools expect in a `.p7b` certificate bundle. Both
are read; `encode/2` writes `CMS` unless asked otherwise.

Every function of `Cmsex` that takes a message also takes it in PEM, so
this module is only needed to write PEM, or to read it apart.

    iex> pem = Cmsex.PEM.encode(<<0x30, 0x03, 0x02, 0x01, 0x01>>)
    "-----BEGIN CMS-----\nMAMCAQE=\n-----END CMS-----\n"
    iex> Cmsex.PEM.decode("Text before\n" <> pem)
    {:ok, <<0x30, 0x03, 0x02, 0x01, 0x01>>}

# `decode`

```elixir
@spec decode(binary()) :: {:ok, binary()} | {:error, Cmsex.Error.t()}
```

Decodes the first PEM block labelled `CMS` or `PKCS7`. Text before and
after the block, and blocks with other labels, are skipped; whitespace
inside the block is ignored. The `END` line must carry the same label.

# `encode`

```elixir
@spec encode(binary(), :cms | :pkcs7) :: String.t()
```

Encodes a message in PEM, with the label `:cms` (the default) or
`:pkcs7`, in lines of 64 characters.

---

*Consult [api-reference.md](api-reference.md) for complete listing*