extract CRLChecker, OCSPChecker

pkg/apiserver/middlewares/v1/crl.go

@@ -0,0 +1,134 @@
+package v1
+
+import (
+	"crypto/x509"
+	"encoding/pem"
+	"fmt"
+	"os"
+	"sync"
+	"time"
+
+	log "github.com/sirupsen/logrus"
+)
+
+type CRLChecker struct {
+	path        string
+	fileInfo    os.FileInfo
+	crls        []*x509.RevocationList
+	logger      *log.Entry
+	mu          sync.RWMutex
+	lastChecked time.Time
+}
+
+func NewCRLChecker(crlPath string, logger *log.Entry) (*CRLChecker, error) {
+	cc := &CRLChecker{
+		path:   crlPath,
+		logger: logger,
+	}
+
+	err := cc.refresh()
+	if err != nil {
+		return nil, err
+	}
+
+	return cc, nil
+}
+
+func (*CRLChecker) decodeCRLs(content []byte, logger *log.Entry) []*x509.RevocationList {
+	var crls []*x509.RevocationList
+
+	for {
+		block, rest := pem.Decode(content)
+		if block == nil {
+			break // no more PEM blocks
+		}
+
+		content = rest
+
+		crl, err := x509.ParseRevocationList(block.Bytes)
+		if err != nil {
+			logger.Errorf("could not parse a PEM block in CRL file, skipping: %s", err)
+			continue
+		}
+
+		crls = append(crls, crl)
+	}
+
+	return crls
+}
+
+// refresh() reads the CRL file if new or changed since the last time
+func (cc *CRLChecker) refresh() error {
+	// noop if lastChecked is less than 5 seconds ago
+	if time.Since(cc.lastChecked) < 5*time.Second {
+		return nil
+	}
+
+	cc.mu.Lock()
+	defer cc.mu.Unlock()
+
+	cc.logger.Debugf("loading CRL file from %s", cc.path)
+
+	fileInfo, err := os.Stat(cc.path)
+	if err != nil {
+		return fmt.Errorf("could not access CRL file: %w", err)
+	}
+
+	// noop if the file didn't change
+	if cc.fileInfo != nil && fileInfo.ModTime().Equal(cc.fileInfo.ModTime()) && fileInfo.Size() == cc.fileInfo.Size() {
+		return nil
+	}
+
+	// the encoding/pem package wants bytes, not io.Reader
+	crlContent, err := os.ReadFile(cc.path)
+	if err != nil {
+		return fmt.Errorf("could not read CRL file: %w", err)
+	}
+
+	cc.crls = cc.decodeCRLs(crlContent, cc.logger)
+	cc.fileInfo = fileInfo
+	cc.lastChecked = time.Now()
+
+	return nil
+}
+
+// isRevoked checks if the client certificate is revoked by any of the CRL blocks
+// It returns a boolean indicating if the certificate is revoked and a boolean indicating
+// if the CRL check was successful and could be cached.
+func (cc *CRLChecker) isRevoked(cert *x509.Certificate) (bool, bool) {
+	if cc == nil {
+		return false, true
+	}
+
+	err := cc.refresh()
+	if err != nil {
+		// we can't quit obviously, so we just log the error and continue
+		// but we can assume we have loaded a CRL, or it would have quit the first time
+		cc.logger.Errorf("while refreshing CRL: %s - will keep using CRL file read at %s", err,
+			cc.lastChecked.Format(time.RFC3339))
+	}
+
+	now := time.Now().UTC()
+
+	cc.mu.RLock()
+	defer cc.mu.RUnlock()
+
+	for _, crl := range cc.crls {
+		if now.After(crl.NextUpdate) {
+			cc.logger.Warn("CRL has expired, will still validate the cert against it.")
+		}
+
+		if now.Before(crl.ThisUpdate) {
+			cc.logger.Warn("CRL is not yet valid, will still validate the cert against it.")
+		}
+
+		for _, revoked := range crl.RevokedCertificateEntries {
+			if revoked.SerialNumber.Cmp(cert.SerialNumber) == 0 {
+				cc.logger.Warn("client certificate is revoked by CRL")
+				return true, true
+			}
+		}
+	}
+
+	return false, true
+}

pkg/apiserver/middlewares/v1/ocsp.go

@@ -0,0 +1,100 @@
+package v1
+
+import (
+	"bytes"
+	"crypto"
+	"crypto/x509"
+	"io"
+	"net/http"
+	"net/url"
+
+	log "github.com/sirupsen/logrus"
+	"golang.org/x/crypto/ocsp"
+)
+
+type OCSPChecker struct {
+	logger *log.Entry
+}
+
+func NewOCSPChecker(logger *log.Entry) *OCSPChecker {
+	return &OCSPChecker{
+		logger: logger,
+	}
+}
+
+func (oc *OCSPChecker) query(server string, cert *x509.Certificate, issuer *x509.Certificate) (*ocsp.Response, error) {
+	req, err := ocsp.CreateRequest(cert, issuer, &ocsp.RequestOptions{Hash: crypto.SHA256})
+	if err != nil {
+		oc.logger.Errorf("TLSAuth: error creating OCSP request: %s", err)
+		return nil, err
+	}
+
+	httpRequest, err := http.NewRequest(http.MethodPost, server, bytes.NewBuffer(req))
+	if err != nil {
+		oc.logger.Error("TLSAuth: cannot create HTTP request for OCSP")
+		return nil, err
+	}
+
+	ocspURL, err := url.Parse(server)
+	if err != nil {
+		oc.logger.Error("TLSAuth: cannot parse OCSP URL")
+		return nil, err
+	}
+
+	httpRequest.Header.Add("Content-Type", "application/ocsp-request")
+	httpRequest.Header.Add("Accept", "application/ocsp-response")
+	httpRequest.Header.Add("host", ocspURL.Host)
+
+	httpClient := &http.Client{}
+
+	// XXX: timeout, context?
+	httpResponse, err := httpClient.Do(httpRequest)
+	if err != nil {
+		oc.logger.Error("TLSAuth: cannot send HTTP request to OCSP")
+		return nil, err
+	}
+	defer httpResponse.Body.Close()
+
+	output, err := io.ReadAll(httpResponse.Body)
+	if err != nil {
+		oc.logger.Error("TLSAuth: cannot read HTTP response from OCSP")
+		return nil, err
+	}
+
+	ocspResponse, err := ocsp.ParseResponseForCert(output, cert, issuer)
+
+	return ocspResponse, err
+}
+
+// isRevoked checks if the client certificate is revoked by any of the OCSP servers present in the certificate.
+// It returns a boolean indicating if the certificate is revoked and a boolean indicating
+// if the OCSP check was successful and could be cached.
+func (oc *OCSPChecker) isRevoked(cert *x509.Certificate, issuer *x509.Certificate) (bool, bool) {
+	if cert.OCSPServer == nil || len(cert.OCSPServer) == 0 {
+		oc.logger.Infof("TLSAuth: no OCSP Server present in client certificate, skipping OCSP verification")
+		return false, true
+	}
+
+	for _, server := range cert.OCSPServer {
+		ocspResponse, err := oc.query(server, cert, issuer)
+		if err != nil {
+			oc.logger.Errorf("TLSAuth: error querying OCSP server %s: %s", server, err)
+			continue
+		}
+
+		switch ocspResponse.Status {
+		case ocsp.Good:
+			return false, true
+		case ocsp.Revoked:
+			oc.logger.Errorf("TLSAuth: client certificate is revoked by server %s", server)
+			return true, true
+		case ocsp.Unknown:
+			log.Debugf("unknown OCSP status for server %s", server)
+			continue
+		}
+	}
+
+	log.Infof("Could not get any valid OCSP response, assuming the cert is revoked")
+
+	return true, false
+}