fix(BRIDGE-351): allow draft creation and import to BYOE addresses in combined mode

internal/services/imapservice/utils.go

@@ -0,0 +1,100 @@
+// Copyright (c) 2025 Proton AG
+//
+// This file is part of Proton Mail Bridge.
+//
+// Proton Mail 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.
+//
+// Proton Mail 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 Proton Mail Bridge.  If not, see <https://www.gnu.org/licenses/>.
+
+package imapservice
+
+import (
+	"errors"
+
+	"github.com/ProtonMail/go-proton-api"
+	"github.com/ProtonMail/proton-bridge/v3/internal/usertypes"
+	"github.com/ProtonMail/proton-bridge/v3/pkg/message/parser"
+)
+
+type connectorInterface interface {
+	getSenderProtonAddress(p *parser.Parser) (proton.Address, error)
+	getAddress(id string) (proton.Address, bool)
+	getPrimaryAddress() (proton.Address, error)
+	getAddressMode() usertypes.AddressMode
+	logError(err error, errMsg string)
+}
+
+func (s *Connector) logError(err error, errMsg string) {
+	s.log.WithError(err).Warn(errMsg)
+}
+
+func (s *Connector) getAddressMode() usertypes.AddressMode {
+	return s.addressMode
+}
+
+func (s *Connector) getPrimaryAddress() (proton.Address, error) {
+	return s.identityState.GetPrimaryAddress()
+}
+
+func (s *Connector) getAddress(id string) (proton.Address, bool) {
+	return s.identityState.GetAddress(id)
+}
+
+func getImportAddress(p *parser.Parser, isDraft bool, id string, conn connectorInterface) (proton.Address, error) {
+	// addr is primary for combined mode or active for split mode
+	address, ok := conn.getAddress(id)
+	if !ok {
+		return proton.Address{}, errors.New("could not find account address")
+	}
+
+	// If the address is external and not BYOE - with sending enabled, then use the primary address as an import target.
+	if address.Type == proton.AddressTypeExternal && !address.Send {
+		var err error
+		address, err = conn.getPrimaryAddress()
+		if err != nil {
+			return proton.Address{}, errors.New("could not get primary account address")
+		}
+	}
+
+	inCombinedMode := conn.getAddressMode() == usertypes.AddressModeCombined
+	if !inCombinedMode {
+		return address, nil
+	}
+
+	senderAddr, err := conn.getSenderProtonAddress(p)
+	if err != nil {
+		if !errors.Is(err, errNoSenderAddressMatch) {
+			conn.logError(err, "Could not get import address")
+		}
+
+		// We did not find a match, so we use the default address.
+		return address, nil
+	}
+
+	if senderAddr.ID == address.ID {
+		return address, nil
+	}
+
+	// GODT-3185 / BRIDGE-120 In combined mode, in certain cases we adapt the address used for encryption.
+	// - draft with non-default address in combined mode: using sender address
+	// - import with non-default address in combined mode: using sender address
+	// - import with non-default disabled address in combined mode: using sender address
+	isSenderAddressDisabled := (!bool(senderAddr.Send)) || (senderAddr.Status != proton.AddressStatusEnabled)
+	isSenderExternalNonBYOE := senderAddr.Type == proton.AddressTypeExternal && !bool(senderAddr.Send)
+
+	// Forbid drafts/imports for external non-BYOE addresses
+	if isSenderExternalNonBYOE || (isDraft && isSenderAddressDisabled) {
+		return address, nil
+	}
+
+	return senderAddr, nil
+}