GODT-1779: Remove go-imap

internal/dialer/dialer_basic.go

@@ -0,0 +1,77 @@
+// Copyright (c) 2022 Proton AG
+//
+// This file is part of Proton Mail Bridge.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 dialer
+
+import (
+	"context"
+	"crypto/tls"
+	"net"
+	"net/http"
+	"time"
+)
+
+type TLSDialer interface {
+	DialTLSContext(ctx context.Context, network, address string) (conn net.Conn, err error)
+}
+
+// CreateTransportWithDialer creates an http.Transport that uses the given dialer to make TLS connections.
+func CreateTransportWithDialer(dialer TLSDialer) *http.Transport {
+	return &http.Transport{
+		DialTLSContext: dialer.DialTLSContext,
+
+		Proxy:               http.ProxyFromEnvironment,
+		MaxIdleConns:        100,
+		MaxIdleConnsPerHost: 100,
+		IdleConnTimeout:     5 * time.Minute,
+
+		ExpectContinueTimeout: 500 * time.Millisecond,
+
+		// GODT-126: this was initially 10s but logs from users showed a significant number
+		// were hitting this timeout, possibly due to flaky wifi taking >10s to reconnect.
+		// Bumping to 30s for now to avoid this problem.
+		ResponseHeaderTimeout: 30 * time.Second,
+
+		// If we allow up to 30 seconds for response headers, it is reasonable to allow up
+		// to 30 seconds for the TLS handshake to take place.
+		TLSHandshakeTimeout: 30 * time.Second,
+	}
+}
+
+// BasicTLSDialer implements TLSDialer.
+type BasicTLSDialer struct {
+	hostURL string
+}
+
+// NewBasicTLSDialer returns a new BasicTLSDialer.
+func NewBasicTLSDialer(hostURL string) *BasicTLSDialer {
+	return &BasicTLSDialer{
+		hostURL: hostURL,
+	}
+}
+
+// DialTLS returns a connection to the given address using the given network.
+func (d *BasicTLSDialer) DialTLSContext(ctx context.Context, network, address string) (conn net.Conn, err error) {
+	return (&tls.Dialer{
+		NetDialer: &net.Dialer{
+			Timeout: 30 * time.Second,
+		},
+		Config: &tls.Config{
+			InsecureSkipVerify: address != d.hostURL,
+		},
+	}).DialContext(ctx, network, address)
+}