133 lines
4.5 KiB
Go
133 lines
4.5 KiB
Go
// Package tlsconfig provides primitives to retrieve secure-enough TLS configurations for both clients and servers.
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//
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// As a reminder from https://golang.org/pkg/crypto/tls/#Config:
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// A Config structure is used to configure a TLS client or server. After one has been passed to a TLS function it must not be modified.
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// A Config may be reused; the tls package will also not modify it.
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package tlsconfig
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import (
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"crypto/tls"
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"crypto/x509"
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"fmt"
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"io/ioutil"
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"os"
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"github.com/Sirupsen/logrus"
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)
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// Options represents the information needed to create client and server TLS configurations.
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type Options struct {
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CAFile string
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// If either CertFile or KeyFile is empty, Client() will not load them
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// preventing the client from authenticating to the server.
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// However, Server() requires them and will error out if they are empty.
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CertFile string
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KeyFile string
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// client-only option
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InsecureSkipVerify bool
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// server-only option
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ClientAuth tls.ClientAuthType
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}
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// Extra (server-side) accepted CBC cipher suites - will phase out in the future
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var acceptedCBCCiphers = []uint16{
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tls.TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA,
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tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA,
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tls.TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA,
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tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA,
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tls.TLS_RSA_WITH_AES_256_CBC_SHA,
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tls.TLS_RSA_WITH_AES_128_CBC_SHA,
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}
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// Client TLS cipher suites (dropping CBC ciphers for client preferred suite set)
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var clientCipherSuites = []uint16{
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tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
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tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
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}
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// DefaultServerAcceptedCiphers should be uses by code which already has a crypto/tls
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// options struct but wants to use a commonly accepted set of TLS cipher suites, with
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// known weak algorithms removed.
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var DefaultServerAcceptedCiphers = append(clientCipherSuites, acceptedCBCCiphers...)
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// ServerDefault is a secure-enough TLS configuration for the server TLS configuration.
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var ServerDefault = tls.Config{
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// Avoid fallback to SSL protocols < TLS1.0
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MinVersion: tls.VersionTLS10,
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PreferServerCipherSuites: true,
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CipherSuites: DefaultServerAcceptedCiphers,
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}
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// ClientDefault is a secure-enough TLS configuration for the client TLS configuration.
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var ClientDefault = tls.Config{
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// Prefer TLS1.2 as the client minimum
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MinVersion: tls.VersionTLS12,
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CipherSuites: clientCipherSuites,
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}
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// certPool returns an X.509 certificate pool from `caFile`, the certificate file.
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func certPool(caFile string) (*x509.CertPool, error) {
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// If we should verify the server, we need to load a trusted ca
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certPool := x509.NewCertPool()
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pem, err := ioutil.ReadFile(caFile)
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if err != nil {
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return nil, fmt.Errorf("Could not read CA certificate %q: %v", caFile, err)
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}
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if !certPool.AppendCertsFromPEM(pem) {
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return nil, fmt.Errorf("failed to append certificates from PEM file: %q", caFile)
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}
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s := certPool.Subjects()
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subjects := make([]string, len(s))
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for i, subject := range s {
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subjects[i] = string(subject)
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}
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logrus.Debugf("Trusting certs with subjects: %v", subjects)
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return certPool, nil
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}
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// Client returns a TLS configuration meant to be used by a client.
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func Client(options Options) (*tls.Config, error) {
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tlsConfig := ClientDefault
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tlsConfig.InsecureSkipVerify = options.InsecureSkipVerify
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if !options.InsecureSkipVerify {
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CAs, err := certPool(options.CAFile)
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if err != nil {
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return nil, err
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}
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tlsConfig.RootCAs = CAs
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}
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if options.CertFile != "" && options.KeyFile != "" {
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tlsCert, err := tls.LoadX509KeyPair(options.CertFile, options.KeyFile)
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if err != nil {
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return nil, fmt.Errorf("Could not load X509 key pair: %v. Make sure the key is not encrypted", err)
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}
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tlsConfig.Certificates = []tls.Certificate{tlsCert}
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}
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return &tlsConfig, nil
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}
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// Server returns a TLS configuration meant to be used by a server.
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func Server(options Options) (*tls.Config, error) {
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tlsConfig := ServerDefault
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tlsConfig.ClientAuth = options.ClientAuth
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tlsCert, err := tls.LoadX509KeyPair(options.CertFile, options.KeyFile)
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if err != nil {
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if os.IsNotExist(err) {
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return nil, fmt.Errorf("Could not load X509 key pair (cert: %q, key: %q): %v", options.CertFile, options.KeyFile, err)
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}
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return nil, fmt.Errorf("Error reading X509 key pair (cert: %q, key: %q): %v. Make sure the key is not encrypted.", options.CertFile, options.KeyFile, err)
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}
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tlsConfig.Certificates = []tls.Certificate{tlsCert}
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if options.ClientAuth >= tls.VerifyClientCertIfGiven {
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CAs, err := certPool(options.CAFile)
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if err != nil {
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return nil, err
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}
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tlsConfig.ClientCAs = CAs
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}
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return &tlsConfig, nil
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}
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