1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
|
// Package tlsconfig provides primitives to retrieve secure-enough TLS configurations for both clients and servers.
//
// As a reminder from https://golang.org/pkg/crypto/tls/#Config:
// 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.
// A Config may be reused; the tls package will also not modify it.
package tlsconfig
import (
"crypto/tls"
"crypto/x509"
"encoding/pem"
"fmt"
"io/ioutil"
"os"
"github.com/pkg/errors"
)
// Options represents the information needed to create client and server TLS configurations.
type Options struct {
CAFile string
// If either CertFile or KeyFile is empty, Client() will not load them
// preventing the client from authenticating to the server.
// However, Server() requires them and will error out if they are empty.
CertFile string
KeyFile string
// client-only option
InsecureSkipVerify bool
// server-only option
ClientAuth tls.ClientAuthType
// If ExclusiveRootPools is set, then if a CA file is provided, the root pool used for TLS
// creds will include exclusively the roots in that CA file. If no CA file is provided,
// the system pool will be used.
ExclusiveRootPools bool
MinVersion uint16
// If Passphrase is set, it will be used to decrypt a TLS private key
// if the key is encrypted
Passphrase string
}
// Extra (server-side) accepted CBC cipher suites - will phase out in the future
var acceptedCBCCiphers = []uint16{
tls.TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA,
tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA,
tls.TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA,
tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA,
tls.TLS_RSA_WITH_AES_256_CBC_SHA,
tls.TLS_RSA_WITH_AES_128_CBC_SHA,
}
// DefaultServerAcceptedCiphers should be uses by code which already has a crypto/tls
// options struct but wants to use a commonly accepted set of TLS cipher suites, with
// known weak algorithms removed.
var DefaultServerAcceptedCiphers = append(clientCipherSuites, acceptedCBCCiphers...)
// allTLSVersions lists all the TLS versions and is used by the code that validates
// a uint16 value as a TLS version.
var allTLSVersions = map[uint16]struct{}{
tls.VersionSSL30: {},
tls.VersionTLS10: {},
tls.VersionTLS11: {},
tls.VersionTLS12: {},
}
// ServerDefault returns a secure-enough TLS configuration for the server TLS configuration.
func ServerDefault() *tls.Config {
return &tls.Config{
// Avoid fallback to SSL protocols < TLS1.0
MinVersion: tls.VersionTLS10,
PreferServerCipherSuites: true,
CipherSuites: DefaultServerAcceptedCiphers,
}
}
// ClientDefault returns a secure-enough TLS configuration for the client TLS configuration.
func ClientDefault() *tls.Config {
return &tls.Config{
// Prefer TLS1.2 as the client minimum
MinVersion: tls.VersionTLS12,
CipherSuites: clientCipherSuites,
}
}
// certPool returns an X.509 certificate pool from `caFile`, the certificate file.
func certPool(caFile string, exclusivePool bool) (*x509.CertPool, error) {
// If we should verify the server, we need to load a trusted ca
var (
certPool *x509.CertPool
err error
)
if exclusivePool {
certPool = x509.NewCertPool()
} else {
certPool, err = SystemCertPool()
if err != nil {
return nil, fmt.Errorf("failed to read system certificates: %v", err)
}
}
pem, err := ioutil.ReadFile(caFile)
if err != nil {
return nil, fmt.Errorf("could not read CA certificate %q: %v", caFile, err)
}
if !certPool.AppendCertsFromPEM(pem) {
return nil, fmt.Errorf("failed to append certificates from PEM file: %q", caFile)
}
return certPool, nil
}
// isValidMinVersion checks that the input value is a valid tls minimum version
func isValidMinVersion(version uint16) bool {
_, ok := allTLSVersions[version]
return ok
}
// adjustMinVersion sets the MinVersion on `config`, the input configuration.
// It assumes the current MinVersion on the `config` is the lowest allowed.
func adjustMinVersion(options Options, config *tls.Config) error {
if options.MinVersion > 0 {
if !isValidMinVersion(options.MinVersion) {
return fmt.Errorf("Invalid minimum TLS version: %x", options.MinVersion)
}
if options.MinVersion < config.MinVersion {
return fmt.Errorf("Requested minimum TLS version is too low. Should be at-least: %x", config.MinVersion)
}
config.MinVersion = options.MinVersion
}
return nil
}
// IsErrEncryptedKey returns true if the 'err' is an error of incorrect
// password when tryin to decrypt a TLS private key
func IsErrEncryptedKey(err error) bool {
return errors.Cause(err) == x509.IncorrectPasswordError
}
// getPrivateKey returns the private key in 'keyBytes', in PEM-encoded format.
// If the private key is encrypted, 'passphrase' is used to decrypted the
// private key.
func getPrivateKey(keyBytes []byte, passphrase string) ([]byte, error) {
// this section makes some small changes to code from notary/tuf/utils/x509.go
pemBlock, _ := pem.Decode(keyBytes)
if pemBlock == nil {
return nil, fmt.Errorf("no valid private key found")
}
var err error
if x509.IsEncryptedPEMBlock(pemBlock) {
keyBytes, err = x509.DecryptPEMBlock(pemBlock, []byte(passphrase))
if err != nil {
return nil, errors.Wrap(err, "private key is encrypted, but could not decrypt it")
}
keyBytes = pem.EncodeToMemory(&pem.Block{Type: pemBlock.Type, Bytes: keyBytes})
}
return keyBytes, nil
}
// getCert returns a Certificate from the CertFile and KeyFile in 'options',
// if the key is encrypted, the Passphrase in 'options' will be used to
// decrypt it.
func getCert(options Options) ([]tls.Certificate, error) {
if options.CertFile == "" && options.KeyFile == "" {
return nil, nil
}
errMessage := "Could not load X509 key pair"
cert, err := ioutil.ReadFile(options.CertFile)
if err != nil {
return nil, errors.Wrap(err, errMessage)
}
prKeyBytes, err := ioutil.ReadFile(options.KeyFile)
if err != nil {
return nil, errors.Wrap(err, errMessage)
}
prKeyBytes, err = getPrivateKey(prKeyBytes, options.Passphrase)
if err != nil {
return nil, errors.Wrap(err, errMessage)
}
tlsCert, err := tls.X509KeyPair(cert, prKeyBytes)
if err != nil {
return nil, errors.Wrap(err, errMessage)
}
return []tls.Certificate{tlsCert}, nil
}
// Client returns a TLS configuration meant to be used by a client.
func Client(options Options) (*tls.Config, error) {
tlsConfig := ClientDefault()
tlsConfig.InsecureSkipVerify = options.InsecureSkipVerify
if !options.InsecureSkipVerify && options.CAFile != "" {
CAs, err := certPool(options.CAFile, options.ExclusiveRootPools)
if err != nil {
return nil, err
}
tlsConfig.RootCAs = CAs
}
tlsCerts, err := getCert(options)
if err != nil {
return nil, err
}
tlsConfig.Certificates = tlsCerts
if err := adjustMinVersion(options, tlsConfig); err != nil {
return nil, err
}
return tlsConfig, nil
}
// Server returns a TLS configuration meant to be used by a server.
func Server(options Options) (*tls.Config, error) {
tlsConfig := ServerDefault()
tlsConfig.ClientAuth = options.ClientAuth
tlsCert, err := tls.LoadX509KeyPair(options.CertFile, options.KeyFile)
if err != nil {
if os.IsNotExist(err) {
return nil, fmt.Errorf("Could not load X509 key pair (cert: %q, key: %q): %v", options.CertFile, options.KeyFile, err)
}
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)
}
tlsConfig.Certificates = []tls.Certificate{tlsCert}
if options.ClientAuth >= tls.VerifyClientCertIfGiven && options.CAFile != "" {
CAs, err := certPool(options.CAFile, options.ExclusiveRootPools)
if err != nil {
return nil, err
}
tlsConfig.ClientCAs = CAs
}
if err := adjustMinVersion(options, tlsConfig); err != nil {
return nil, err
}
return tlsConfig, nil
}
|
