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Script to create a CA hierarchy with delegated OCSP responder certificates to test the effects on different combinations of OCSP Signing EKU settings
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// certutil -urlcache * delete | |
// certutil -verify -user -urlfetch "Server Certificate.cer" | |
package main | |
import ( | |
"crypto" | |
"crypto/rand" | |
"crypto/rsa" | |
"crypto/tls" | |
"crypto/x509" | |
"crypto/x509/pkix" | |
"encoding/asn1" | |
"encoding/base64" | |
"fmt" | |
"io" | |
"io/ioutil" | |
"log" | |
"math/big" | |
"net/http" | |
"net/url" | |
"path" | |
"time" | |
"golang.org/x/crypto/ocsp" | |
) | |
func main() { | |
// Self signed root CA | |
rootCATemplate := &x509.Certificate{ | |
SerialNumber: big.NewInt(time.Now().UnixNano()), | |
Subject: pkix.Name{ | |
CommonName: "Root", | |
}, | |
NotBefore: time.Now(), | |
NotAfter: time.Now().AddDate(25, 0, 0), | |
IsCA: true, | |
BasicConstraintsValid: true, | |
KeyUsage: x509.KeyUsageCertSign | x509.KeyUsageCRLSign, | |
} | |
rootKey, rootCert, err := createAndIssue(rootCATemplate, nil, nil) | |
if err != nil { | |
panic(err) | |
} | |
// ICA | |
iCATemplate := &x509.Certificate{ | |
SerialNumber: big.NewInt(time.Now().UnixNano()), | |
Subject: pkix.Name{ | |
CommonName: "ICA", | |
}, | |
NotBefore: time.Now(), | |
NotAfter: time.Now().AddDate(10, 0, 0), | |
IsCA: true, | |
BasicConstraintsValid: true, | |
KeyUsage: x509.KeyUsageCertSign | x509.KeyUsageCRLSign, | |
ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth, x509.ExtKeyUsageServerAuth}, | |
OCSPServer: []string{"http://localhost:8080"}, | |
} | |
icaKey, icaCert, err := createAndIssue(iCATemplate, rootCert, rootKey) | |
if err != nil { | |
panic(err) | |
} | |
icaOCSPResponse, err := createOCSP(rootKey, rootCert, icaCert) | |
if err != nil { | |
panic(err) | |
} | |
// ICA2 | |
iCA2Template := &x509.Certificate{ | |
SerialNumber: big.NewInt(time.Now().UnixNano()), | |
Subject: pkix.Name{ | |
CommonName: "ICA 2", | |
}, | |
NotBefore: time.Now(), | |
NotAfter: time.Now().AddDate(10, 0, 0), | |
IsCA: true, | |
BasicConstraintsValid: true, | |
KeyUsage: x509.KeyUsageCertSign | x509.KeyUsageCRLSign, | |
ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth, x509.ExtKeyUsageServerAuth, x509.ExtKeyUsageOCSPSigning}, | |
OCSPServer: []string{"http://localhost:8080"}, | |
} | |
ica2Key, ica2Cert, err := createAndIssue(iCA2Template, rootCert, rootKey) | |
if err != nil { | |
panic(err) | |
} | |
ica2OCSPResponse, err := createOCSP(rootKey, rootCert, ica2Cert) | |
if err != nil { | |
panic(err) | |
} | |
// overrull the OCSP response | |
icaOCSPResponse, err = ocsp.CreateResponse(rootCert, ica2Cert, ocsp.Response{ | |
Status: ocsp.Revoked, | |
SerialNumber: icaCert.SerialNumber, | |
ThisUpdate: time.Now(), | |
NextUpdate: time.Now().AddDate(1, 0, 0), | |
RevokedAt: time.Now(), | |
RevocationReason: ocsp.KeyCompromise, | |
Certificate: ica2Cert, | |
}, ica2Key) | |
if err != nil { | |
panic(err) | |
} | |
// Server certificate | |
serverTemplate := &x509.Certificate{ | |
SerialNumber: big.NewInt(time.Now().UnixNano()), | |
Subject: pkix.Name{ | |
CommonName: "Server Certificate", | |
}, | |
DNSNames: []string{"localhost"}, | |
NotBefore: time.Now(), | |
NotAfter: time.Now().AddDate(0, 3, 0), | |
KeyUsage: x509.KeyUsageDigitalSignature, | |
ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth, x509.ExtKeyUsageServerAuth}, | |
OCSPServer: []string{"http://localhost:8080"}, | |
} | |
serverKey, serverCert, err := createAndIssue(serverTemplate, icaCert, icaKey) | |
if err != nil { | |
panic(err) | |
} | |
serverOCSPResponse, err := createOCSP(icaKey, icaCert, serverCert) | |
if err != nil { | |
panic(err) | |
} | |
ocspResponses := make(map[string][]byte) | |
ocspResponses[icaCert.SerialNumber.String()] = icaOCSPResponse | |
ocspResponses[ica2Cert.SerialNumber.String()] = ica2OCSPResponse | |
ocspResponses[serverCert.SerialNumber.String()] = serverOCSPResponse | |
// Verify | |
rootPool := x509.NewCertPool() | |
rootPool.AddCert(rootCert) | |
icaPool := x509.NewCertPool() | |
icaPool.AddCert(icaCert) | |
_, err = icaCert.Verify(x509.VerifyOptions{ | |
Roots: rootPool, | |
Intermediates: icaPool, | |
CurrentTime: time.Now(), | |
KeyUsages: []x509.ExtKeyUsage{x509.ExtKeyUsageOCSPSigning}, | |
}) | |
if err != nil { | |
log.Println("Verify error:", err) | |
} else { | |
log.Println("Verify OK") | |
} | |
go startWebserver(serverKey, serverCert, icaCert) | |
startOCSPServer(ocspResponses) | |
} | |
func createOCSP(icaKey crypto.Signer, icaCert, cert *x509.Certificate) ([]byte, error) { | |
// OCSP Signing Certificate | |
ocspTemplate := &x509.Certificate{ | |
SerialNumber: big.NewInt(3), | |
Subject: pkix.Name{ | |
CommonName: "Delegated OCSP signing certificate for " + icaCert.Subject.CommonName, | |
}, | |
NotBefore: time.Now(), | |
NotAfter: time.Now().AddDate(0, 3, 0), | |
KeyUsage: x509.KeyUsageDigitalSignature, | |
ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageOCSPSigning}, | |
} | |
ocspTemplate.ExtraExtensions = append(ocspTemplate.ExtraExtensions, pkix.Extension{ | |
Id: asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 48, 1, 5}, | |
Value: []byte{asn1.TagNull, 0}, | |
Critical: false, | |
}) | |
ocspKey, ocspCert, err := createAndIssue(ocspTemplate, icaCert, icaKey) | |
if err != nil { | |
return nil, err | |
} | |
// Create OCSP response | |
ocspResponse, err := ocsp.CreateResponse(icaCert, ocspCert, ocsp.Response{ | |
Status: ocsp.Good, | |
SerialNumber: cert.SerialNumber, | |
ThisUpdate: time.Now(), | |
NextUpdate: time.Now().AddDate(1, 0, 0), | |
Certificate: ocspCert, | |
}, ocspKey) | |
if err != nil { | |
return nil, err | |
} | |
return ocspResponse, nil | |
} | |
func startWebserver(key crypto.PrivateKey, cert, issuer *x509.Certificate) { | |
serverHandler := func(w http.ResponseWriter, req *http.Request) { | |
log.Printf("HTTPS | %s [%s] %s\n", req.UserAgent(), req.Method, req.RequestURI) | |
io.WriteString(w, "Hello, world!\n") | |
} | |
mux := http.NewServeMux() | |
mux.HandleFunc("/", serverHandler) | |
cfg := &tls.Config{Certificates: []tls.Certificate{{ | |
Certificate: [][]byte{cert.Raw, issuer.Raw}, | |
PrivateKey: key, | |
}}} | |
srv := &http.Server{ | |
Addr: ":8443", | |
TLSConfig: cfg, | |
ReadTimeout: time.Minute, | |
WriteTimeout: time.Minute, | |
Handler: mux, | |
} | |
log.Println("Starting webserver on port 8443") | |
log.Fatal(srv.ListenAndServeTLS("", "")) | |
} | |
func startOCSPServer(response map[string][]byte) { | |
ocspHandler := func(w http.ResponseWriter, req *http.Request) { | |
log.Printf("OCSP | %s [%s] %s\n", req.UserAgent(), req.Method, req.RequestURI) | |
var err error | |
var request []byte | |
switch req.Method { | |
case http.MethodPost: | |
request, err = ioutil.ReadAll(req.Body) | |
if err != nil { | |
log.Println(err) | |
return | |
} | |
case http.MethodGet: | |
requestBase64, err := url.QueryUnescape(path.Base(req.URL.RawPath)) | |
if err != nil { | |
log.Println(err) | |
return | |
} | |
request, err = base64.StdEncoding.DecodeString(requestBase64) | |
if err != nil { | |
log.Println(err) | |
return | |
} | |
} | |
or, err := ocsp.ParseRequest(request) | |
if err != nil { | |
log.Println(err) | |
return | |
} | |
if _, ok := response[or.SerialNumber.String()]; !ok { | |
log.Println("OCSP | Unkown serial number:", or.SerialNumber) | |
return | |
} | |
w.Header().Set("Content-Type", "application/ocsp-response") | |
w.Write(response[or.SerialNumber.String()]) | |
log.Println("OCSP | Request served for serial number:", or.SerialNumber.String()) | |
} | |
mux := http.NewServeMux() | |
mux.HandleFunc("/", ocspHandler) | |
srv := &http.Server{ | |
Addr: ":8080", | |
ReadTimeout: time.Minute, | |
WriteTimeout: time.Minute, | |
Handler: mux, | |
} | |
log.Fatal(srv.ListenAndServe()) | |
} | |
func createAndIssue(template, issuerCert *x509.Certificate, issuerKey crypto.Signer) (crypto.Signer, *x509.Certificate, error) { | |
private, err := rsa.GenerateKey(rand.Reader, 2048) | |
if err != nil { | |
panic(err) | |
} | |
if issuerKey == nil { | |
issuerKey = private | |
issuerCert = template | |
} | |
rawCert, err := x509.CreateCertificate(rand.Reader, template, issuerCert, private.Public(), issuerKey) | |
if err != nil { | |
fmt.Println(err) | |
return nil, nil, err | |
} | |
cert, err := x509.ParseCertificate(rawCert) | |
if err != nil { | |
return nil, nil, err | |
} | |
ioutil.WriteFile(cert.Subject.CommonName+".cer", rawCert, 0644) | |
fmt.Printf("Issued certificate:\n\tSubject: %s\n\tIssuer: %s\n\n", cert.Subject, cert.Issuer) | |
return private, cert, nil | |
} |
OpenSSL accepts the response:
openssl ocsp -CAfile root.pem -issuer root.pem -cert ca.pem -no_nonce -text -url http://localhost:8080
OCSP Request Data:
Version: 1 (0x0)
Requestor List:
Certificate ID:
Hash Algorithm: sha1
Issuer Name Hash: BB14FA9683082119DC1C1FBE0D6D312AD95A7D65
Issuer Key Hash: 99334693D848FE1E0F93B80EB31A15068A388874
Serial Number: 161F21532EA4BEDB
OCSP Response Data:
OCSP Response Status: successful (0x0)
Response Type: Basic OCSP Response
Version: 1 (0x0)
Responder Id: CN = ICA 2
Produced At: Jul 6 09:57:00 2020 GMT
Responses:
Certificate ID:
Hash Algorithm: sha1
Issuer Name Hash: BB14FA9683082119DC1C1FBE0D6D312AD95A7D65
Issuer Key Hash: 99334693D848FE1E0F93B80EB31A15068A388874
Serial Number: 161F21532EA4BEDB
Cert Status: revoked
Revocation Time: Jul 6 09:57:15 2020 GMT
Revocation Reason: keyCompromise (0x1)
This Update: Jul 6 09:57:15 2020 GMT
Next Update: Jul 6 09:57:15 2021 GMT
Signature Algorithm: sha256WithRSAEncryption
72:91:eb:d0:4b:1b:82:34:b9:8b:23:e1:0f:38:b4:ea:4b:3c:
68:6a:ac:08:08:1b:6e:9b:ff:46:c2:9d:98:42:43:d0:16:b4:
a6:04:57:02:6d:d7:c5:38:4c:d2:4b:07:89:25:18:11:84:01:
ad:f9:ff:05:9a:cc:91:ce:f0:03:bc:8f:ec:b7:09:fd:b6:d5:
8a:a8:bd:07:5d:df:24:ae:0f:2e:05:1d:4a:ab:de:62:14:b0:
98:a7:8b:06:17:c9:5b:a7:79:2a:57:ce:f1:8c:90:df:54:82:
46:24:22:8d:94:ac:ce:03:e2:08:d5:58:de:b9:68:ca:ed:d1:
74:21:35:eb:8a:4f:d0:54:9f:c7:7e:32:e9:97:9e:54:01:9a:
e3:cc:06:a2:4b:55:84:93:74:5c:c8:bf:3f:12:e2:b8:08:46:
11:6b:86:90:87:e8:41:fe:44:3e:13:6f:2a:f9:4f:f5:ca:7a:
54:56:8a:77:75:c6:fc:c1:5c:84:95:c2:0e:d6:a8:56:af:1a:
bc:91:73:67:b9:97:61:2e:59:df:41:61:9f:5e:2e:25:d2:95:
2b:1a:3d:0f:13:1f:58:27:e5:68:15:ff:bc:f6:ea:08:49:e8:
cb:e7:3f:5d:e0:ef:25:3b:36:c0:e7:31:ca:79:13:f8:e8:38:
6e:af:1a:0e
Certificate:
Data:
Version: 3 (0x2)
Serial Number: 1594029434537339075 (0x161f21533f1d68c3)
Signature Algorithm: sha256WithRSAEncryption
Issuer: CN=Root
Validity
Not Before: Jul 6 09:57:14 2020 GMT
Not After : Jul 6 09:57:14 2030 GMT
Subject: CN=ICA 2
Subject Public Key Info:
Public Key Algorithm: rsaEncryption
RSA Public-Key: (2048 bit)
Modulus:
00:98:c1:2c:70:a8:70:0b:5b:dd:5d:45:d3:9a:de:
c8:b3:11:b2:5d:7a:69:0e:c9:44:58:5d:64:9f:c0:
6a:23:64:e9:f4:ce:11:db:4e:0f:02:5f:f7:35:90:
e2:96:31:ce:5b:c4:d9:b7:b2:5c:57:2e:91:19:00:
af:f5:17:e5:27:1c:80:98:46:20:ee:5b:3d:82:3d:
f9:e5:50:ce:91:45:45:ae:25:1d:0f:ef:8e:d8:14:
7d:6d:cd:95:56:1f:d9:9b:98:17:29:b2:17:2d:36:
95:d3:dd:2f:21:a8:b5:be:ec:70:a4:09:31:cb:f1:
16:a3:62:84:4c:c0:90:37:6b:af:14:15:cd:45:2e:
26:63:2a:2c:53:72:af:a1:c6:b9:00:b3:99:61:bb:
26:25:aa:b8:d8:78:fe:89:d8:53:65:0f:02:66:87:
89:2a:03:31:e6:99:24:ed:c4:d7:04:11:f8:60:d1:
31:18:96:3f:a0:ad:fa:f1:a5:bb:16:5c:5f:e2:3f:
6a:e0:58:4a:d4:45:d2:a4:88:ff:f3:32:7e:85:84:
73:7a:ca:cd:22:bc:4d:33:4c:6d:08:01:18:df:8f:
b3:1a:3e:f0:e0:d2:bd:45:03:62:98:7f:99:fe:be:
eb:3d:88:2c:f3:36:8f:86:0b:e3:b3:d7:83:52:fa:
b2:49
Exponent: 65537 (0x10001)
X509v3 extensions:
X509v3 Key Usage: critical
Certificate Sign, CRL Sign
X509v3 Extended Key Usage:
TLS Web Client Authentication, TLS Web Server Authentication, OCSP Signing
X509v3 Basic Constraints: critical
CA:TRUE
Authority Information Access:
OCSP - URI:http://localhost:8080
Signature Algorithm: sha256WithRSAEncryption
2f:f7:4b:ed:38:0f:64:c0:34:87:88:a0:9c:55:98:9d:26:67:
5b:1d:1c:f6:ba:9c:2c:85:95:4d:81:9d:74:aa:50:d4:55:e9:
5e:90:c5:55:dc:63:e9:d0:56:56:22:b2:54:83:95:b8:5e:f5:
f6:00:5f:80:db:fd:b7:d0:d5:e4:1e:ff:81:f9:55:ee:3c:71:
12:c1:d7:4d:aa:c6:4d:59:56:38:76:8b:08:0b:cf:60:2c:3d:
c4:38:ba:f8:b1:66:99:36:d6:b9:26:f7:0f:4e:de:1a:eb:e2:
1e:98:38:9b:e4:d4:c9:c6:37:79:f8:50:ea:0d:17:e1:e9:f5:
da:d7:1f:79:c4:c0:22:9f:eb:74:71:de:5b:82:83:7b:7e:43:
98:fc:f9:65:b2:7f:fe:fe:47:0c:d4:b8:05:73:7a:c1:6b:4a:
60:35:de:56:41:8b:f6:be:0c:a4:98:af:50:be:7f:da:1b:e2:
2a:9f:4f:10:10:64:cf:83:92:21:65:5c:0b:d5:bd:24:35:e1:
9b:0d:7b:de:98:91:35:c4:7c:fb:04:aa:f2:ae:01:57:1f:62:
67:6f:92:7a:88:95:73:76:c3:a7:d9:17:b2:6c:26:b5:a4:43:
18:56:51:12:fe:4f:b4:ad:86:be:85:da:76:91:4c:2d:f9:dd:
20:f1:c2:0c
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
Response verify OK
ca.pem: revoked
This Update: Jul 6 09:57:15 2020 GMT
Next Update: Jul 6 09:57:15 2021 GMT
Reason: keyCompromise
Revocation Time: Jul 6 09:57:15 2020 GMT
Like OpenSSL, ocspcheck
on MacOS accepts the OCSP response issued by the ICA 2
sibling CA.
ocspcheck -vvvvvvvv -N -C root.pem chain.pem ; echo $?
Built an 75 byte ocsp request
Using http to host localhost, port 80, path /
DNS returns ::1 for localhost
Server at localhost returns:
[Body]=[1289 bytes]
OCSP response signature validated from localhost
OCSP response status 0 from host localhost
ocspcheck: Invalid OCSP reply: certificate is revoked
ocspcheck: Certificate revoked at: Mon Jul 6 13:02:49 2020
1
Using your Digitorus TLS Connection online tester, I just noticed that LetsEncrypt R3 OSCP Responder is not responding (in a positive way) to the third unknown HTTP method (in 5-byte DER format, as opposed to HTTP GET or POST method).
Digitorus reported to that OSCP Responder unknown HTTP method as “unauthorized”.
Is this more a legacy issue and can be safely ignored, or not?
unauthorized is a server status that is used instead of unknown, mostly for pre-produced responses as an unknown response is signed and an unauthorized status not.
This is good to know. Thank you and keep up the good work.
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To check the abuse case of this scenario I have added a second issuing CA
ICA 2
with the EKU OCSP signing and used that to sign arevoked
OCSP response for a certificate underICA
In this case
certutil
fails to validate the OCSP response as the server would be offline?