We build too many walls and not enough bridges

pkg/message/body.go

@@ -0,0 +1,75 @@
+// Copyright (c) 2020 Proton Technologies AG
+//
+// This file is part of ProtonMail Bridge.
+//
+// ProtonMail Bridge is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// ProtonMail Bridge is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with ProtonMail Bridge.  If not, see <https://www.gnu.org/licenses/>.
+
+package message
+
+import (
+	"encoding/base64"
+	"fmt"
+	"io"
+	"mime/quotedprintable"
+
+	pmcrypto "github.com/ProtonMail/gopenpgp/crypto"
+	"github.com/ProtonMail/proton-bridge/pkg/pmapi"
+	"github.com/emersion/go-textwrapper"
+	openpgperrors "golang.org/x/crypto/openpgp/errors"
+)
+
+func WriteBody(w io.Writer, kr *pmcrypto.KeyRing, m *pmapi.Message) error {
+	// Decrypt body.
+	if err := m.Decrypt(kr); err != nil && err != openpgperrors.ErrSignatureExpired {
+		return err
+	}
+	if m.MIMEType != pmapi.ContentTypeMultipartMixed {
+		// Encode it.
+		qp := quotedprintable.NewWriter(w)
+		if _, err := io.WriteString(qp, m.Body); err != nil {
+			return err
+		}
+		return qp.Close()
+	}
+	_, err := io.WriteString(w, m.Body)
+	return err
+}
+
+func WriteAttachmentBody(w io.Writer, kr *pmcrypto.KeyRing, m *pmapi.Message, att *pmapi.Attachment, r io.Reader) (err error) {
+	// Decrypt it
+	var dr io.Reader
+	dr, err = att.Decrypt(r, kr)
+	if err == openpgperrors.ErrKeyIncorrect {
+		// Do not fail if attachment is encrypted with a different key.
+		dr = r
+		err = nil
+		att.Name += ".gpg"
+		att.MIMEType = "application/pgp-encrypted"
+	} else if err != nil && err != openpgperrors.ErrSignatureExpired {
+		err = fmt.Errorf("cannot decrypt attachment: %v", err)
+		return
+	}
+
+	// Encode it.
+	ww := textwrapper.NewRFC822(w)
+	bw := base64.NewEncoder(base64.StdEncoding, ww)
+
+	var n int64
+	if n, err = io.Copy(bw, dr); err != nil {
+		err = fmt.Errorf("cannot write attachment: %v (wrote %v bytes)", err, n)
+	}
+
+	_ = bw.Close()
+	return
+}