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// Modifier instance is provided to milter handlers to modify email messages
package milter
import (
"bytes"
"encoding/binary"
"fmt"
"net/textproto"
)
// postfix wants LF lines endings. Using CRLF results in double CR sequences.
func crlfToLF(b []byte) []byte {
return bytes.ReplaceAll(b, []byte{'\r', '\n'}, []byte{'\n'})
}
// Modifier provides access to Macros, Headers and Body data to callback handlers. It also defines a
// number of functions that can be used by callback handlers to modify processing of the email message
type Modifier struct {
Macros map[string]string
Headers textproto.MIMEHeader
writePacket func(*Message) error
}
// AddRecipient appends a new envelope recipient for current message
func (m *Modifier) AddRecipient(r string) error {
data := []byte(fmt.Sprintf("<%s>", r) + null)
return m.writePacket(NewResponse('+', data).Response())
}
// DeleteRecipient removes an envelope recipient address from message
func (m *Modifier) DeleteRecipient(r string) error {
data := []byte(fmt.Sprintf("<%s>", r) + null)
return m.writePacket(NewResponse('-', data).Response())
}
// ReplaceBody substitutes message body with provided body
func (m *Modifier) ReplaceBody(body []byte) error {
body = crlfToLF(body)
return m.writePacket(NewResponse('b', body).Response())
}
// AddHeader appends a new email message header the message
func (m *Modifier) AddHeader(name, value string) error {
var buffer bytes.Buffer
buffer.WriteString(name + null)
buffer.Write(crlfToLF([]byte(value)))
buffer.WriteString(null)
return m.writePacket(NewResponse('h', buffer.Bytes()).Response())
}
// Quarantine a message by giving a reason to hold it
func (m *Modifier) Quarantine(reason string) error {
return m.writePacket(NewResponse('q', []byte(reason+null)).Response())
}
// ChangeHeader replaces the header at the specified position with a new one.
// The index is per name.
func (m *Modifier) ChangeHeader(index int, name, value string) error {
var buffer bytes.Buffer
if err := binary.Write(&buffer, binary.BigEndian, uint32(index)); err != nil {
return err
}
buffer.WriteString(name + null)
buffer.Write(crlfToLF([]byte(value)))
buffer.WriteString(null)
return m.writePacket(NewResponse('m', buffer.Bytes()).Response())
}
// InsertHeader inserts the header at the specified position
func (m *Modifier) InsertHeader(index int, name, value string) error {
var buffer bytes.Buffer
if err := binary.Write(&buffer, binary.BigEndian, uint32(index)); err != nil {
return err
}
buffer.WriteString(name + null)
buffer.Write(crlfToLF([]byte(value)))
buffer.WriteString(null)
return m.writePacket(NewResponse('i', buffer.Bytes()).Response())
}
// ChangeFrom replaces the FROM envelope header with a new one
func (m *Modifier) ChangeFrom(value string) error {
data := []byte(value + null)
return m.writePacket(NewResponse('e', data).Response())
}
// newModifier creates a new Modifier instance from milterSession
func newModifier(s *milterSession) *Modifier {
return &Modifier{
Macros: s.macros,
Headers: s.headers,
writePacket: s.WritePacket,
}
}
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