subjectpass

Documentation

Overview

Package subjectpass implements a mechanism for reject an incoming message with a challenge to include a token in a next delivery attempt.

An SMTP server can reject a message with instructions to send another message, this time including a special token. The sender will receive a DSN, which will include the error message with instructions. By sending the message again with the token, as instructed, the SMTP server can recognize the token, verify it, and accept the message.

Index

• Variables
• func Generate(elog *slog.Logger, mailFrom smtp.Address, key []byte, tm time.Time) string
• func Verify(elog *slog.Logger, r io.ReaderAt, key []byte, period time.Duration) (rerr error)

Variables

var (
	MetricGenerate stub.Counter    = stub.CounterIgnore{}
	MetricVerify   stub.CounterVec = stub.CounterVecIgnore{}
)

var (
	ErrMessage = errors.New("subjectpass: malformed message")
	ErrAbsent  = errors.New("subjectpass: no token found")
	ErrFrom    = errors.New("subjectpass: bad From")
	ErrInvalid = errors.New("subjectpass: malformed token")
	ErrVerify  = errors.New("subjectpass: verification failed")
	ErrExpired = errors.New("subjectpass: token expired")
)

var Explanation = "" /* 134-byte string literal not displayed */

Functions

func Generate

func Generate(elog *slog.Logger, mailFrom smtp.Address, key []byte, tm time.Time) string

Generate generates a token that is valid for "mailFrom", starting from "tm" and signed with "key".

The token is of the form: (pass:<signeddata>). Instructions to the sender should be to include this token in the Subject header of a new message.

func Verify

func Verify(elog *slog.Logger, r io.ReaderAt, key []byte, period time.Duration) (rerr error)

Verify parses "message" and checks if it includes a subjectpass token in its Subject header that is still valid (within "period") and signed with "key".