mirror of
https://github.com/tailscale/tailscale.git
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77 lines
2.2 KiB
Go
77 lines
2.2 KiB
Go
// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package tlsdial originally existed to set up a tls.Config for x509
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// validation, using a memory-optimized path for iOS, but then we
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// moved that to the tailscale/go tree instead, so now this package
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// does very little. But for now we keep it as a unified point where
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// we might want to add shared policy on outgoing TLS connections from
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// the 3 places in the client that connect to Tailscale (logs,
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// control, DERP).
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package tlsdial
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import (
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"crypto/tls"
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"crypto/x509"
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"errors"
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"time"
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)
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// Config returns a tls.Config for connecting to a server.
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// If base is non-nil, it's cloned as the base config before
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// being configured and returned.
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func Config(host string, base *tls.Config) *tls.Config {
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var conf *tls.Config
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if base == nil {
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conf = new(tls.Config)
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} else {
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conf = base.Clone()
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}
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conf.ServerName = host
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return conf
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}
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// SetConfigExpectedCert modifies c to expect and verify that the server returns
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// a certificate for the provided certDNSName.
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func SetConfigExpectedCert(c *tls.Config, certDNSName string) {
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if c.ServerName == certDNSName {
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return
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}
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if c.ServerName == "" {
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c.ServerName = certDNSName
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return
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}
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if c.VerifyPeerCertificate != nil {
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panic("refusing to override tls.Config.VerifyPeerCertificate")
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}
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// Set InsecureSkipVerify to prevent crypto/tls from doing its
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// own cert verification, but do the same work that it'd do
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// (but using certDNSName) in the VerifyPeerCertificate hook.
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c.InsecureSkipVerify = true
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c.VerifyPeerCertificate = func(rawCerts [][]byte, _ [][]*x509.Certificate) error {
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if len(rawCerts) == 0 {
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return errors.New("no certs presented")
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}
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certs := make([]*x509.Certificate, len(rawCerts))
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for i, asn1Data := range rawCerts {
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cert, err := x509.ParseCertificate(asn1Data)
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if err != nil {
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return err
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}
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certs[i] = cert
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}
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opts := x509.VerifyOptions{
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CurrentTime: time.Now(),
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DNSName: certDNSName,
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Intermediates: x509.NewCertPool(),
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}
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for _, cert := range certs[1:] {
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opts.Intermediates.AddCert(cert)
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}
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_, err := certs[0].Verify(opts)
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return err
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}
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}
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