-
Notifications
You must be signed in to change notification settings - Fork 15
/
certificate_validation.go
333 lines (286 loc) · 9.73 KB
/
certificate_validation.go
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
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
// SPDX-License-Identifier: Apache-2.0
package services
import (
"bytes"
"context"
"crypto"
"crypto/x509"
"encoding/base64"
"encoding/hex"
"errors"
"fmt"
"github.com/thoughtworks/maeve-csms/manager/ocpp/ocpp201"
"golang.org/x/crypto/ocsp"
"golang.org/x/exp/slog"
"io"
"math/big"
"net/http"
)
// OCSPError is an error returned by the OCSP server in response to a check
type OCSPError int
func (o OCSPError) Error() string {
return fmt.Sprintf("ocsp validation failed: %d", o)
}
type ValidationError int
const (
ValidationErrorCertChain ValidationError = iota
ValidationErrorCertExpired
ValidationErrorCertRevoked
ValidationErrorWrongEmaid
)
func (v ValidationError) Error() string {
switch v {
case ValidationErrorCertChain:
return "certificate chain invalid"
case ValidationErrorCertExpired:
return "certificate expired"
case ValidationErrorCertRevoked:
return "certificate revoked"
case ValidationErrorWrongEmaid:
return "wrong emaid"
default:
return fmt.Sprintf("unknown error: %d", v)
}
}
type CertificateValidationService interface {
ValidatePEMCertificateChain(ctx context.Context, pemChain []byte, eMAID string) (*string, error)
ValidateHashedCertificateChain(ctx context.Context, ocspRequestData []ocpp201.OCSPRequestDataType) (*string, error)
}
type OnlineCertificateValidationService struct {
RootCertificateProvider RootCertificateProviderService
MaxOCSPAttempts int
HttpClient *http.Client
}
func (o *OnlineCertificateValidationService) ValidatePEMCertificateChain(ctx context.Context, pemChain []byte, eMAID string) (*string, error) {
certificateChain, err := ParseCertificates(pemChain)
if err != nil {
return nil, err
}
if len(certificateChain) == 0 {
return nil, fmt.Errorf("empty certificate chain")
}
err = o.validateEMAID(certificateChain[0], eMAID)
if err != nil {
return nil, err
}
rootCerts, err := o.RootCertificateProvider.ProvideCertificates(ctx)
if err != nil {
return nil, err
}
err = o.validatePEMCertificateChain(certificateChain, rootCerts)
if err != nil {
return nil, err
}
ocspResponse, err := o.validatePEMCertificateChainOCSPStatus(ctx, certificateChain, rootCerts, o.MaxOCSPAttempts)
if err != nil {
return ocspResponse, err
}
return ocspResponse, nil
}
func (o *OnlineCertificateValidationService) ValidateHashedCertificateChain(ctx context.Context, ocspRequestData []ocpp201.OCSPRequestDataType) (*string, error) {
var ocspResponse *string
var err error
for _, requestData := range ocspRequestData {
var ocspRequest []byte
ocspRequest, err = o.createOCSPRequestFromHashData(requestData.IssuerNameHash, requestData.IssuerKeyHash,
requestData.SerialNumber, string(requestData.HashAlgorithm))
if err != nil {
return nil, err
}
var ocspResp *string
ocspResp, err = o.performOCSPCheck(ctx, []string{requestData.ResponderURL}, ocspRequest, nil, o.MaxOCSPAttempts)
if err != nil {
return ocspResp, err
}
if ocspResponse == nil {
ocspResponse = ocspResp
}
}
return ocspResponse, err
}
func (o *OnlineCertificateValidationService) validatePEMCertificateChain(certificateChain, rootCertificates []*x509.Certificate) error {
if len(certificateChain) < 1 {
return errors.New("no certificates in chain")
}
intermediates := x509.NewCertPool()
if len(certificateChain) > 1 {
for _, cert := range certificateChain[1:] {
intermediates.AddCert(cert)
}
}
trustedCerts := x509.NewCertPool()
for _, cert := range rootCertificates {
trustedCerts.AddCert(cert)
}
opts := x509.VerifyOptions{
Roots: trustedCerts,
Intermediates: intermediates,
KeyUsages: []x509.ExtKeyUsage{x509.ExtKeyUsageAny},
}
_, err := certificateChain[0].Verify(opts)
var invalidCertErr *x509.CertificateInvalidError
if errors.As(err, &invalidCertErr) && invalidCertErr.Reason == x509.Expired {
return fmt.Errorf("validating certificate chain: %s: %w", invalidCertErr, ValidationErrorCertExpired)
} else if err != nil {
return fmt.Errorf("validating certificate chain: %s: %w", err, ValidationErrorCertChain)
}
return nil
}
func (o *OnlineCertificateValidationService) validateEMAID(certificate *x509.Certificate, eMAID string) error {
if certificate.Subject.CommonName != eMAID {
return fmt.Errorf("leaf certificate CN: %s, not %s: %w", certificate.Subject.CommonName, eMAID, ValidationErrorWrongEmaid)
}
return nil
}
func (o *OnlineCertificateValidationService) validatePEMCertificateChainOCSPStatus(ctx context.Context, certificateChain, rootCertificates []*x509.Certificate, maxRetries int) (ocspResponse *string, err error) {
if len(certificateChain) < 1 {
return nil, fmt.Errorf("no certificates in chain: %w", ValidationErrorCertChain)
}
// validate each certificate with issuer
for i := 1; i < len(certificateChain); i++ {
if len(certificateChain[i-1].OCSPServer) > 0 {
var ocspRequest []byte
ocspRequest, err = o.createOCSPRequestFromCertificate(certificateChain[i-1], certificateChain[i])
if err != nil {
return
}
ocspResponse, err = o.performOCSPCheck(ctx, certificateChain[i-1].OCSPServer, ocspRequest, certificateChain[i], maxRetries)
if err != nil {
return
}
}
}
// validate last certificate in chain with configured root CA
subjectCert := certificateChain[len(certificateChain)-1]
if len(subjectCert.OCSPServer) > 0 {
for _, rootCert := range rootCertificates {
if bytes.Equal(subjectCert.AuthorityKeyId, rootCert.SubjectKeyId) {
var ocspRequest []byte
ocspRequest, err = o.createOCSPRequestFromCertificate(subjectCert, rootCert)
if err != nil {
return
}
return o.performOCSPCheck(ctx, subjectCert.OCSPServer, ocspRequest, rootCert, maxRetries)
}
}
}
if ocspResponse != nil {
return
}
return nil, fmt.Errorf("no OCSP response available: %w", ValidationErrorCertChain)
}
func (o *OnlineCertificateValidationService) performOCSPCheck(ctx context.Context, ocspResponderUrls []string, ocspRequest []byte, issuerCert *x509.Certificate, maxAttempts int) (*string, error) {
var ocspResponderUrlCount int
if ocspResponderUrls != nil {
var ocspResponderUrlsCopy []string
for _, url := range ocspResponderUrls {
if url != "" {
ocspResponderUrlsCopy = append(ocspResponderUrlsCopy, url)
}
}
ocspResponderUrls = ocspResponderUrlsCopy
ocspResponderUrlCount = len(ocspResponderUrls)
} else {
return nil, errors.New("no OCSP servers specified")
}
if len(ocspResponderUrls) == 0 {
return nil, nil
}
for attempt := 1; attempt <= maxAttempts; attempt++ {
responderUrl := ocspResponderUrls[attempt%ocspResponderUrlCount]
ocspResponse, err := o.attemptOCSPCheck(ctx, responderUrl, ocspRequest, issuerCert)
if err == nil {
return ocspResponse, nil
}
var ocspError *OCSPError
if errors.As(err, &ocspError) {
return ocspResponse, fmt.Errorf("ocsp check status: %d: %w", ocspError, ValidationErrorCertRevoked)
}
slog.Warn("ocsp check", slog.Int("attempt", attempt), slog.Int("maxAttempts", maxAttempts), "error", err)
}
return nil, fmt.Errorf("failed to perform ocsp check after %d attempts", maxAttempts)
}
func (o *OnlineCertificateValidationService) createOCSPRequestFromCertificate(subjectCert, issuerCert *x509.Certificate) ([]byte, error) {
return ocsp.CreateRequest(subjectCert, issuerCert, nil)
}
func (o *OnlineCertificateValidationService) createOCSPRequestFromHashData(issuerNameHashHex, issuerKeyHashHex, serialNumber, hashAlg string) ([]byte, error) {
n := new(big.Int)
serial, ok := n.SetString(serialNumber, 16)
if !ok {
return nil, fmt.Errorf("unable to parse serial number %s as base 16 string", serial)
}
issuerNameHash, err := hex.DecodeString(issuerNameHashHex)
if err != nil {
return nil, fmt.Errorf("parsing issuer name hash %s: %w", issuerNameHashHex, err)
}
issuerKeyHash, err := hex.DecodeString(issuerKeyHashHex)
if err != nil {
return nil, fmt.Errorf("parsing issuer key hash %s: %w", issuerKeyHash, err)
}
req := ocsp.Request{
HashAlgorithm: hashAlgorithm(hashAlg),
IssuerNameHash: issuerNameHash,
IssuerKeyHash: issuerKeyHash,
SerialNumber: serial,
}
return req.Marshal()
}
func (o *OnlineCertificateValidationService) attemptOCSPCheck(ctx context.Context, ocspResponderUrl string, ocspRequest []byte, issuerCert *x509.Certificate) (*string, error) {
//#nosec G107 - need to use OCSP URL specified in the certificate
req, err := http.NewRequestWithContext(ctx, http.MethodPost, ocspResponderUrl, bytes.NewReader(ocspRequest))
if err != nil {
return nil, fmt.Errorf("new request: %w", err)
}
req.Header.Add("Content-Type", "application/ocsp-request")
req.Header.Add("Accept", "application/ocsp-response")
resp, err := o.HttpClient.Do(req)
if err != nil {
return nil, fmt.Errorf("post %s: %w", ocspResponderUrl, err)
}
if resp.StatusCode != http.StatusOK {
return nil, fmt.Errorf("post %s status %s", ocspResponderUrl, resp.Status)
}
defer func() {
_ = resp.Body.Close()
}()
respBytes, err := io.ReadAll(resp.Body)
if err != nil {
return nil, fmt.Errorf("reading body: %w", err)
}
base64Response := base64.StdEncoding.EncodeToString(respBytes)
ocspResp, err := ocsp.ParseResponse(respBytes, issuerCert)
if err != nil {
return &base64Response, fmt.Errorf("parsing ocsp response: %w", err)
}
if ocspResp.Status != ocsp.Good {
return &base64Response, OCSPError(ocspResp.Status)
}
return &base64Response, nil
}
func ParseCertificates(pemData []byte) ([]*x509.Certificate, error) {
var certs []*x509.Certificate
for {
cert, rest, err := parseCertificate(pemData)
if err != nil {
return nil, err
}
if cert == nil {
break
}
certs = append(certs, cert)
pemData = rest
}
return certs, nil
}
func hashAlgorithm(hash string) crypto.Hash {
switch hash {
case "SHA256":
return crypto.SHA256
case "SHA384":
return crypto.SHA384
case "SHA512":
return crypto.SHA512
default:
return crypto.SHA256
}
}