GODT-35: Finish all details and make tests pass

pkg/pmapi/dialer_pinning.go

@@ -0,0 +1,110 @@
+// Copyright (c) 2021 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 pmapi
+
+import (
+	"crypto/tls"
+	"net"
+
+	"github.com/sirupsen/logrus"
+)
+
+// TrustedAPIPins contains trusted public keys of the protonmail API and proxies.
+// NOTE: the proxy pins are the same for all proxy servers, guaranteed by infra team ;).
+var TrustedAPIPins = []string{ // nolint[gochecknoglobals]
+	// api.protonmail.ch
+	`pin-sha256="drtmcR2kFkM8qJClsuWgUzxgBkePfRCkRpqUesyDmeE="`, // current
+	`pin-sha256="YRGlaY0jyJ4Jw2/4M8FIftwbDIQfh8Sdro96CeEel54="`, // hot backup
+	`pin-sha256="AfMENBVvOS8MnISprtvyPsjKlPooqh8nMB/pvCrpJpw="`, // cold backup
+
+	// protonmail.com
+	`pin-sha256="8joiNBdqaYiQpKskgtkJsqRxF7zN0C0aqfi8DacknnI="`, // current
+	`pin-sha256="JMI8yrbc6jB1FYGyyWRLFTmDNgIszrNEMGlgy972e7w="`, // hot backup
+	`pin-sha256="Iu44zU84EOCZ9vx/vz67/MRVrxF1IO4i4NIa8ETwiIY="`, // cold backup
+
+	// proxies
+	`pin-sha256="EU6TS9MO0L/GsDHvVc9D5fChYLNy5JdGYpJw0ccgetM="`, // main
+	`pin-sha256="iKPIHPnDNqdkvOnTClQ8zQAIKG0XavaPkcEo0LBAABA="`, // backup 1
+	`pin-sha256="MSlVrBCdL0hKyczvgYVSRNm88RicyY04Q2y5qrBt0xA="`, // backup 2
+	`pin-sha256="C2UxW0T1Ckl9s+8cXfjXxlEqwAfPM4HiW2y3UdtBeCw="`, // backup 3
+}
+
+// TLSReportURI is the address where TLS reports should be sent.
+const TLSReportURI = "https://reports.protonmail.ch/reports/tls"
+
+// PinningTLSDialer wraps a TLSDialer to check fingerprints after connecting and
+// to report errors if the fingerprint check fails.
+type PinningTLSDialer struct {
+	dialer TLSDialer
+
+	// pinChecker is used to check TLS keys of connections.
+	pinChecker *pinChecker
+
+	reporter *tlsReporter
+
+	// tlsIssueNotifier is used to notify something when there is a TLS issue.
+	tlsIssueNotifier func()
+
+	// A logger for logging messages.
+	log logrus.FieldLogger
+}
+
+// NewPinningTLSDialer constructs a new dialer which only returns tcp connections to servers
+// which present known certificates.
+// If enabled, it reports any invalid certificates it finds.
+func NewPinningTLSDialer(cfg Config, dialer TLSDialer) *PinningTLSDialer {
+	return &PinningTLSDialer{
+		dialer:           dialer,
+		pinChecker:       newPinChecker(TrustedAPIPins),
+		reporter:         newTLSReporter(cfg, TrustedAPIPins),
+		tlsIssueNotifier: cfg.TLSIssueHandler,
+		log:              logrus.WithField("pkg", "pmapi/tls-pinning"),
+	}
+}
+
+// DialTLS dials the given network/address, returning an error if the certificates don't match the trusted pins.
+func (p *PinningTLSDialer) DialTLS(network, address string) (net.Conn, error) {
+	conn, err := p.dialer.DialTLS(network, address)
+	if err != nil {
+		return nil, err
+	}
+
+	host, port, err := net.SplitHostPort(address)
+	if err != nil {
+		return nil, err
+	}
+
+	if err := p.pinChecker.checkCertificate(conn); err != nil {
+		if p.tlsIssueNotifier != nil {
+			go p.tlsIssueNotifier()
+		}
+
+		if tlsConn, ok := conn.(*tls.Conn); ok && p.reporter != nil {
+			p.reporter.reportCertIssue(
+				TLSReportURI,
+				host,
+				port,
+				tlsConn.ConnectionState(),
+			)
+		}
+
+		return nil, err
+	}
+
+	return conn, nil
+}