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
|
package stfe
import (
"fmt"
"crypto"
"crypto/ecdsa"
"crypto/ed25519"
"crypto/rand"
"crypto/rsa"
"crypto/tls"
"crypto/x509"
"encoding/base64"
"encoding/pem"
"io/ioutil"
)
// LoadTrustAnchors loads a list of PEM-encoded certificates from file
func LoadTrustAnchors(path string) ([]*x509.Certificate, *x509.CertPool, error) {
rest, err := ioutil.ReadFile(path)
if err != nil {
return nil, nil, fmt.Errorf("failed reading trust anchors: %v", err)
}
pool := x509.NewCertPool()
var anchors []*x509.Certificate
for len(rest) > 0 {
var block *pem.Block
block, rest = pem.Decode(rest)
if block == nil {
break
}
if block.Type != "CERTIFICATE" {
return nil, nil, fmt.Errorf("unexpected PEM block type: %s", block.Type)
}
certificate, err := x509.ParseCertificate(block.Bytes)
if err != nil {
return nil, nil, fmt.Errorf("invalid trust anchor before rest(%s): %v", rest, err)
}
anchors = append(anchors, certificate)
pool.AddCert(certificate)
}
if len(anchors) == 0 {
return nil, nil, fmt.Errorf("found no valid trust anchor in: %s", path)
}
return anchors, pool, nil
}
func LoadEd25519SigningKey(path string) (ed25519.PrivateKey, error) {
data, err := ioutil.ReadFile(path)
if err != nil {
return nil, fmt.Errorf("failed reading private key: %v", err)
}
var block *pem.Block
block, data = pem.Decode(data)
if block == nil {
return nil, fmt.Errorf("private key not loaded")
}
if block.Type != "PRIVATE KEY" {
return nil, fmt.Errorf("unexpected PEM block type: %s", block.Type)
}
if len(data) != 0 {
return nil, fmt.Errorf("trailing data found after key: %v", data)
}
key, err := x509.ParsePKCS8PrivateKey(block.Bytes)
if err != nil {
return nil, fmt.Errorf("failed parsing signing key: %v", err)
}
switch t := key.(type) {
case ed25519.PrivateKey:
return key.(ed25519.PrivateKey), nil
default:
return nil, fmt.Errorf("unexpected signing key type: %v", t)
}
}
func VerifyChain(ld *LogParameters, certificate *x509.Certificate) ([]*x509.Certificate, error) {
opts := x509.VerifyOptions{
Roots: ld.AnchorPool,
KeyUsages: []x509.ExtKeyUsage{x509.ExtKeyUsageAny}, // TODO: move to ld
} // TODO: add intermediates
chains, err := certificate.Verify(opts)
if err != nil {
return nil, fmt.Errorf("chain verification failed: %v", err)
}
if len(chains) == 0 {
return nil, fmt.Errorf("chain verification failed: no chain")
}
return chains[0], nil // if we found multiple paths just pick the first one
}
func VerifySignature(leaf, signature []byte, certificate *x509.Certificate) error {
var algo x509.SignatureAlgorithm
switch t := certificate.PublicKey.(type) {
case *rsa.PublicKey:
algo = x509.SHA256WithRSA
case *ecdsa.PublicKey:
algo = x509.ECDSAWithSHA256
default:
return fmt.Errorf("unsupported public key algorithm: %v", t)
}
if err := certificate.CheckSignature(algo, leaf, signature); err != nil {
return fmt.Errorf("invalid signature: %v", err)
}
return nil
}
func GenV1SDI(ld *LogParameters, leaf []byte) (*StItem, error) {
// Note that ed25519 does not use the passed io.Reader
sig, err := ld.Signer.Sign(rand.Reader, leaf, crypto.Hash(0))
if err != nil {
return nil, fmt.Errorf("ed25519 signature failed: %v", err)
}
return NewSignedDebugInfoV1(ld.LogId, []byte("reserved"), sig), nil
}
func GenV1STH(ld *LogParameters, th *TreeHeadV1) (*StItem, error) {
serialized, err := th.Marshal()
if err != nil {
return nil, fmt.Errorf("failed tls marshaling tree head: %v", err)
}
// Note that ed25519 does not use the passed io.Reader
sig, err := ld.Signer.Sign(rand.Reader, serialized, crypto.Hash(0))
if err != nil {
return nil, fmt.Errorf("ed25519 signature failed: %v", err)
}
return NewSignedTreeHeadV1(th, ld.LogId, sig), nil
}
// ParseB64Chain parses a list of base64 DER-encoded X.509 certificates, such
// that the first (zero-index) string is interpretted as an end-entity
// certificate and the remaining ones as the an intermediate CertPool.
func ParseB64Chain(chain []string) (*x509.Certificate, *x509.CertPool, error) {
var certificate *x509.Certificate
intermediatePool := x509.NewCertPool()
for index, cert := range chain {
der, err := base64.StdEncoding.DecodeString(cert)
if err != nil {
return nil, nil, fmt.Errorf("certificate decoding failed: %v", err)
}
c, err := x509.ParseCertificate(der)
if err != nil {
return nil, nil, fmt.Errorf("certificate decoding failed: %v", err)
}
if index == 0 {
certificate = c
} else {
intermediatePool.AddCert(c)
}
}
if certificate == nil {
return nil, nil, fmt.Errorf("certificate chain is empty")
}
return certificate, intermediatePool, nil
}
func buildChainFromB64List(lp *LogParameters, b64chain []string) ([]*x509.Certificate, error) {
certificate, _, err := ParseB64Chain(b64chain) // TODO: use intermediatePool
if err != nil {
return nil, err
}
opts := x509.VerifyOptions{
Roots: lp.AnchorPool,
KeyUsages: []x509.ExtKeyUsage{x509.ExtKeyUsageAny}, // TODO: move to ld
}
chains, err := certificate.Verify(opts)
if err != nil {
return nil, fmt.Errorf("chain verification failed: %v", err)
}
if len(chains) == 0 {
return nil, fmt.Errorf("chain verification failed: no chain")
}
chain := chains[0] // if we found multiple paths just pick the first one
// TODO: check that len(chain) is OK
return chain, nil
}
// verifySignature checks if signature is valid for some serialized data. The
// only supported signature scheme is ecdsa_secp256r1_sha256(0x0403), see ยง4.3.2
// in RFC 8446. TODO: replace ECDSA with ed25519(0x0807)
func verifySignature(_ *LogParameters, certificate *x509.Certificate, scheme tls.SignatureScheme, serialized, signature []byte) error {
if scheme != tls.ECDSAWithP256AndSHA256 {
return fmt.Errorf("unsupported signature scheme: %v", scheme)
}
if err := certificate.CheckSignature(x509.ECDSAWithSHA256, serialized, signature); err != nil {
return fmt.Errorf("invalid signature: %v", err)
}
return nil
}
|
