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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 | |
| } |
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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OpenSSL accepts the response: