568 lines
14 KiB
Go
568 lines
14 KiB
Go
// Copyright (c) 2022 Proton AG
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//
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// This file is part of Proton Mail Bridge.
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//
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// Proton Mail Bridge is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// Proton Mail Bridge is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with Proton Mail Bridge. If not, see <https://www.gnu.org/licenses/>.
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package message
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import (
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"bytes"
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"encoding/base64"
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"mime"
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"net/mail"
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"strings"
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"time"
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"unicode/utf8"
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"github.com/ProtonMail/gluon/rfc822"
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"github.com/ProtonMail/go-proton-api"
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"github.com/ProtonMail/go-rfc5322"
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"github.com/ProtonMail/gopenpgp/v2/crypto"
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"github.com/ProtonMail/proton-bridge/v2/pkg/algo"
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"github.com/bradenaw/juniper/xslices"
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"github.com/emersion/go-message"
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"github.com/emersion/go-message/textproto"
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"github.com/pkg/errors"
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)
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var (
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ErrDecryptionFailed = errors.New("message could not be decrypted")
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ErrNoSuchKeyRing = errors.New("the keyring to decrypt this message could not be found")
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)
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// InternalIDDomain is used as a placeholder for reference/message ID headers to improve compatibility with various clients.
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const InternalIDDomain = `protonmail.internalid`
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func BuildRFC822(kr *crypto.KeyRing, msg proton.Message, attData [][]byte, opts JobOptions) ([]byte, error) {
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switch {
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case len(msg.Attachments) > 0:
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return buildMultipartRFC822(kr, msg, attData, opts)
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case msg.MIMEType == "multipart/mixed":
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return buildPGPRFC822(kr, msg, opts)
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default:
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return buildSimpleRFC822(kr, msg, opts)
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}
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}
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func buildSimpleRFC822(kr *crypto.KeyRing, msg proton.Message, opts JobOptions) ([]byte, error) {
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dec, err := msg.Decrypt(kr)
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if err != nil {
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if !opts.IgnoreDecryptionErrors {
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return nil, errors.Wrap(ErrDecryptionFailed, err.Error())
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}
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return buildMultipartRFC822(kr, msg, nil, opts)
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}
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hdr := getTextPartHeader(getMessageHeader(msg, opts), dec, msg.MIMEType)
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buf := new(bytes.Buffer)
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w, err := message.CreateWriter(buf, hdr)
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if err != nil {
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return nil, err
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}
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if _, err := w.Write(dec); err != nil {
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return nil, err
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}
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if err := w.Close(); err != nil {
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return nil, err
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}
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return buf.Bytes(), nil
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}
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func buildMultipartRFC822(
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kr *crypto.KeyRing,
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msg proton.Message,
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attData [][]byte,
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opts JobOptions,
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) ([]byte, error) {
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boundary := newBoundary(msg.ID)
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hdr := getMessageHeader(msg, opts)
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hdr.SetContentType("multipart/mixed", map[string]string{"boundary": boundary.gen()})
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buf := new(bytes.Buffer)
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w, err := message.CreateWriter(buf, hdr)
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if err != nil {
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return nil, err
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}
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var (
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inlineAtts []proton.Attachment
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inlineData [][]byte
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attachAtts []proton.Attachment
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attachData [][]byte
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)
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for index, att := range msg.Attachments {
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if att.Disposition == proton.InlineDisposition {
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inlineAtts = append(inlineAtts, att)
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inlineData = append(inlineData, attData[index])
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} else {
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attachAtts = append(attachAtts, att)
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attachData = append(attachData, attData[index])
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}
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}
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if len(inlineAtts) > 0 {
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if err := writeRelatedParts(w, kr, boundary, msg, inlineAtts, inlineData, opts); err != nil {
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return nil, err
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}
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} else if err := writeTextPart(w, kr, msg, opts); err != nil {
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return nil, err
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}
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for i, att := range attachAtts {
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if err := writeAttachmentPart(w, kr, att, attachData[i], opts); err != nil {
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return nil, err
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}
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}
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if err := w.Close(); err != nil {
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return nil, err
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}
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return buf.Bytes(), nil
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}
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func writeTextPart(
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w *message.Writer,
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kr *crypto.KeyRing,
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msg proton.Message,
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opts JobOptions,
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) error {
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dec, err := msg.Decrypt(kr)
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if err != nil {
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if !opts.IgnoreDecryptionErrors {
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return errors.Wrap(ErrDecryptionFailed, err.Error())
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}
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return writeCustomTextPart(w, msg, err)
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}
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return writePart(w, getTextPartHeader(message.Header{}, dec, msg.MIMEType), dec)
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}
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func writeAttachmentPart(
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w *message.Writer,
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kr *crypto.KeyRing,
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att proton.Attachment,
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attData []byte,
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opts JobOptions,
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) error {
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kps, err := base64.StdEncoding.DecodeString(att.KeyPackets)
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if err != nil {
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return err
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}
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msg := crypto.NewPGPSplitMessage(kps, attData).GetPGPMessage()
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dec, err := kr.Decrypt(msg, nil, crypto.GetUnixTime())
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if err != nil {
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if !opts.IgnoreDecryptionErrors {
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return errors.Wrap(ErrDecryptionFailed, err.Error())
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}
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log.
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WithField("attID", att.ID).
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WithError(err).
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Warn("Attachment decryption failed")
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return writeCustomAttachmentPart(w, att, msg, err)
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}
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return writePart(w, getAttachmentPartHeader(att), dec.GetBinary())
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}
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func writeRelatedParts(
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w *message.Writer,
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kr *crypto.KeyRing,
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boundary *boundary,
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msg proton.Message,
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atts []proton.Attachment,
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attData [][]byte,
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opts JobOptions,
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) error {
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hdr := message.Header{}
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hdr.SetContentType("multipart/related", map[string]string{"boundary": boundary.gen()})
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return createPart(w, hdr, func(rel *message.Writer) error {
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if err := writeTextPart(rel, kr, msg, opts); err != nil {
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return err
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}
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for i, att := range atts {
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if err := writeAttachmentPart(rel, kr, att, attData[i], opts); err != nil {
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return err
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}
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}
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return nil
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})
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}
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func buildPGPRFC822(kr *crypto.KeyRing, msg proton.Message, opts JobOptions) ([]byte, error) {
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dec, err := msg.Decrypt(kr)
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if err != nil {
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if !opts.IgnoreDecryptionErrors {
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return nil, errors.Wrap(ErrDecryptionFailed, err.Error())
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}
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return buildPGPMIMEFallbackRFC822(msg, opts)
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}
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hdr := getMessageHeader(msg, opts)
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sigs, err := proton.ExtractSignatures(kr, msg.Body)
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if err != nil {
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log.WithError(err).WithField("id", msg.ID).Warn("Extract signature failed")
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}
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if len(sigs) > 0 {
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return writeMultipartSignedRFC822(hdr, dec, sigs[0])
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}
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return writeMultipartEncryptedRFC822(hdr, dec)
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}
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func buildPGPMIMEFallbackRFC822(msg proton.Message, opts JobOptions) ([]byte, error) {
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hdr := getMessageHeader(msg, opts)
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hdr.SetContentType("multipart/encrypted", map[string]string{
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"boundary": newBoundary(msg.ID).gen(),
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"protocol": "application/pgp-encrypted",
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})
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buf := new(bytes.Buffer)
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w, err := message.CreateWriter(buf, hdr)
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if err != nil {
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return nil, err
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}
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var encHdr message.Header
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encHdr.SetContentType("application/pgp-encrypted", nil)
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encHdr.Set("Content-Description", "PGP/MIME version identification")
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if err := writePart(w, encHdr, []byte("Version: 1")); err != nil {
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return nil, err
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}
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var dataHdr message.Header
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dataHdr.SetContentType("application/octet-stream", map[string]string{"name": "encrypted.asc"})
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dataHdr.SetContentDisposition("inline", map[string]string{"filename": "encrypted.asc"})
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dataHdr.Set("Content-Description", "OpenPGP encrypted message")
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if err := writePart(w, dataHdr, []byte(msg.Body)); err != nil {
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return nil, err
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}
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if err := w.Close(); err != nil {
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return nil, err
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}
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return buf.Bytes(), nil
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}
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func writeMultipartSignedRFC822(header message.Header, body []byte, sig proton.Signature) ([]byte, error) { //nolint:funlen
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buf := new(bytes.Buffer)
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boundary := newBoundary("").gen()
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header.SetContentType("multipart/signed", map[string]string{
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"micalg": sig.Hash,
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"protocol": "application/pgp-signature",
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"boundary": boundary,
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})
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if err := textproto.WriteHeader(buf, header.Header); err != nil {
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return nil, err
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}
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mw := textproto.NewMultipartWriter(buf)
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if err := mw.SetBoundary(boundary); err != nil {
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return nil, err
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}
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bodyHeader, bodyData, err := readHeaderBody(body)
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if err != nil {
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return nil, err
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}
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bodyPart, err := mw.CreatePart(*bodyHeader)
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if err != nil {
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return nil, err
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}
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if _, err := bodyPart.Write(bodyData); err != nil {
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return nil, err
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}
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var sigHeader message.Header
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sigHeader.SetContentType("application/pgp-signature", map[string]string{"name": "OpenPGP_signature.asc"})
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sigHeader.SetContentDisposition("attachment", map[string]string{"filename": "OpenPGP_signature"})
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sigHeader.Set("Content-Description", "OpenPGP digital signature")
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sigPart, err := mw.CreatePart(sigHeader.Header)
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if err != nil {
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return nil, err
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}
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sigData, err := sig.Data.GetArmored()
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if err != nil {
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return nil, err
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}
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if _, err := sigPart.Write([]byte(sigData)); err != nil {
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return nil, err
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}
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if err := mw.Close(); err != nil {
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return nil, err
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}
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return buf.Bytes(), nil
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}
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func writeMultipartEncryptedRFC822(header message.Header, body []byte) ([]byte, error) {
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buf := new(bytes.Buffer)
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bodyHeader, bodyData, err := readHeaderBody(body)
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if err != nil {
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return nil, err
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}
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// Remove old content type header as it is non-standard. Ensure that messages
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// without content type header entries don't become invalid.
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header.Del("Content-Type")
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entFields := bodyHeader.Fields()
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for entFields.Next() {
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header.Set(entFields.Key(), entFields.Value())
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}
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if err := textproto.WriteHeader(buf, header.Header); err != nil {
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return nil, err
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}
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if _, err := buf.Write(bodyData); err != nil {
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return nil, err
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}
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return buf.Bytes(), nil
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}
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func getMessageHeader(msg proton.Message, opts JobOptions) message.Header { //nolint:funlen
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hdr := toMessageHeader(msg.ParsedHeaders)
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// SetText will RFC2047-encode.
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if msg.Subject != "" {
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hdr.SetText("Subject", msg.Subject)
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}
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// mail.Address.String() will RFC2047-encode if necessary.
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if msg.Sender != nil {
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hdr.Set("From", msg.Sender.String())
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}
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if len(msg.ReplyTos) > 0 {
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hdr.Set("Reply-To", toAddressList(msg.ReplyTos))
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}
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if len(msg.ToList) > 0 {
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hdr.Set("To", toAddressList(msg.ToList))
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}
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if len(msg.CCList) > 0 {
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hdr.Set("Cc", toAddressList(msg.CCList))
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}
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if len(msg.BCCList) > 0 {
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hdr.Set("Bcc", toAddressList(msg.BCCList))
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}
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setMessageIDIfNeeded(msg, &hdr)
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// Sanitize the date; it needs to have a valid unix timestamp.
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if opts.SanitizeDate {
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if date, err := rfc5322.ParseDateTime(hdr.Get("Date")); err != nil || date.Before(time.Unix(0, 0)) {
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msgDate := SanitizeMessageDate(msg.Time)
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hdr.Set("Date", msgDate.In(time.UTC).Format(time.RFC1123Z))
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// We clobbered the date so we save it under X-Original-Date.
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hdr.Set("X-Original-Date", date.In(time.UTC).Format(time.RFC1123Z))
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}
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}
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// Set our internal ID if requested.
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// This is important for us to detect whether APPENDed things are actually "move like outlook".
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if opts.AddInternalID {
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hdr.Set("X-Pm-Internal-Id", msg.ID)
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}
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// Set our external ID if requested.
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// This was useful during debugging of applemail recovered messages; doesn't help with any behaviour.
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if opts.AddExternalID {
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hdr.Set("X-Pm-External-Id", "<"+msg.ExternalID+">")
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}
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// Set our server date if requested.
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// Can be useful to see how long it took for a message to arrive.
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if opts.AddMessageDate {
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hdr.Set("X-Pm-Date", time.Unix(msg.Time, 0).In(time.UTC).Format(time.RFC1123Z))
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}
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// Include the message ID in the references (supposedly this somehow improves outlook support...).
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if opts.AddMessageIDReference {
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if refs := hdr.Values("References"); xslices.IndexFunc(refs, func(ref string) bool {
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return strings.Contains(ref, msg.ID)
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}) < 0 {
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hdr.Set("References", strings.Join(append(refs, "<"+msg.ID+"@"+InternalIDDomain+">"), " "))
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}
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}
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return hdr
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}
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// SanitizeMessageDate will return time from msgTime timestamp. If timestamp is
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// not after epoch the RFC822 publish day will be used. No message should
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// realistically be older than RFC822 itself.
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func SanitizeMessageDate(msgTime int64) time.Time {
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if msgTime := time.Unix(msgTime, 0); msgTime.After(time.Unix(0, 0)) {
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return msgTime
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}
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return time.Date(1982, 8, 13, 0, 0, 0, 0, time.UTC)
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}
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// setMessageIDIfNeeded sets Message-Id from ExternalID or ID if it's not
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// already set.
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func setMessageIDIfNeeded(msg proton.Message, hdr *message.Header) {
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if hdr.Get("Message-Id") == "" {
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if msg.ExternalID != "" {
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hdr.Set("Message-Id", "<"+msg.ExternalID+">")
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} else {
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hdr.Set("Message-Id", "<"+msg.ID+"@"+InternalIDDomain+">")
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}
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}
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}
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func getTextPartHeader(hdr message.Header, body []byte, mimeType rfc822.MIMEType) message.Header {
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params := make(map[string]string)
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if utf8.Valid(body) {
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params["charset"] = "utf-8"
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}
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hdr.SetContentType(string(mimeType), params)
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// Use quoted-printable for all text/... parts
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hdr.Set("Content-Transfer-Encoding", "quoted-printable")
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return hdr
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}
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func getAttachmentPartHeader(att proton.Attachment) message.Header {
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hdr := toMessageHeader(att.Headers)
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// All attachments have a content type.
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hdr.SetContentType(string(att.MIMEType), map[string]string{"name": mime.QEncoding.Encode("utf-8", att.Name)})
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// All attachments have a content disposition.
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hdr.SetContentDisposition(string(att.Disposition), map[string]string{"filename": mime.QEncoding.Encode("utf-8", att.Name)})
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// Use base64 for all attachments except embedded RFC822 messages.
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if att.MIMEType != rfc822.MessageRFC822 {
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hdr.Set("Content-Transfer-Encoding", "base64")
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} else {
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hdr.Del("Content-Transfer-Encoding")
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}
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return hdr
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}
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func toMessageHeader(hdr proton.Headers) message.Header {
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var res message.Header
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for key, val := range hdr {
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for _, val := range val {
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// Using AddRaw instead of Add to save key-value pair as byte buffer within Header.
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// This buffer is used latter on in message writer to construct message and avoid crash
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// when key length is more than 76 characters long.
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res.AddRaw([]byte(key + ": " + val + "\r\n"))
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}
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}
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return res
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}
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func toAddressList(addrs []*mail.Address) string {
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res := make([]string, len(addrs))
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for i, addr := range addrs {
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res[i] = addr.String()
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}
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return strings.Join(res, ", ")
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}
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func createPart(w *message.Writer, hdr message.Header, fn func(*message.Writer) error) error {
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part, err := w.CreatePart(hdr)
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if err != nil {
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return err
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}
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if err := fn(part); err != nil {
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return err
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}
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return part.Close()
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}
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func writePart(w *message.Writer, hdr message.Header, body []byte) error {
|
|
return createPart(w, hdr, func(part *message.Writer) error {
|
|
if _, err := part.Write(body); err != nil {
|
|
return errors.Wrap(err, "failed to write part body")
|
|
}
|
|
|
|
return nil
|
|
})
|
|
}
|
|
|
|
type boundary struct {
|
|
val string
|
|
}
|
|
|
|
func newBoundary(seed string) *boundary {
|
|
return &boundary{val: seed}
|
|
}
|
|
|
|
func (bw *boundary) gen() string {
|
|
bw.val = algo.HashHexSHA256(bw.val)
|
|
return bw.val
|
|
}
|