Sovite.SMTP.DataDecoder (sovite v0.2.0)

Copy Markdown View Source

Streaming decoder for SMTP DATA content (RFC 5321 §4.1.1.4, §4.5.2).

It removes dot-stuffing and finds the end of data without buffering the message: feed it bytes as they arrive and it returns the decoded content as iodata.

Only <CRLF>.<CRLF> ends the data. A bare LF or bare CR (one not part of a CRLF pair) is handled by the policy, so it can never be read as a line ending by one MTA and as content by another (SMTP smuggling):

  • :reject - stop with {:error, :bare_lf | :bare_cr}.

  • :normalize - convert it to CRLF in the output. The line it ends cannot end the data, even if it is a single dot.

The decoded content keeps CRLF line endings, and the final CRLF before the terminating dot is part of the content.

Summary

Types

policy()
t()

Functions

decode(decoder, bytes)

Decodes bytes.

new(policy \\ :reject)

Returns a decoder for content right after the 354 reply.

Types

policy()

@type policy() :: :reject | :normalize

t()

@opaque t()

Functions

decode(decoder, bytes)

@spec decode(t(), binary()) ::
  {:more, iodata(), t()}
  | {:done, iodata(), binary()}
  | {:error, :bare_lf | :bare_cr, iodata()}

Decodes bytes.

  • {:more, content, decoder} - the data has not ended yet.
  • {:done, content, rest} - the data ended; rest is the input after the terminating .<CRLF>, such as pipelined commands.
  • {:error, reason, content} - a bare line ending under :reject. content is what was decoded before it.

new(policy \\ :reject)

@spec new(policy()) :: t()

Returns a decoder for content right after the 354 reply.