scep_test.go

package scep_test

import (
	"bytes"
	"crypto"
	"crypto/rand"
	"crypto/rsa"
	"crypto/x509"
	"crypto/x509/pkix"
	"encoding/pem"
	"errors"
	"fmt"
	"io"
	"log"
	"math/big"
	"os"
	"path"
	"regexp"
	"strings"
	"testing"
	"time"

	"github.com/smallstep/scep"
	"github.com/smallstep/scep/cryptoutil"
)

type testLogger struct {
	l *log.Logger
}

func (l *testLogger) Log(keyValues ...interface{}) error {
	if len(keyValues)%2 != 0 {
		return fmt.Errorf("uneven number of key-values provided: %d", len(keyValues))
	}

	line := "level=debug"

	for i := 0; i < len(keyValues); i += 2 {
		line += " " + fmt.Sprintf("%s=%s", keyValues[i], keyValues[i+1])
	}

	l.l.Println(line)

	return nil
}

func newTestLogger(w io.Writer) *testLogger {
	return &testLogger{
		l: log.New(w, "", log.LstdFlags),
	}
}

var newLines = regexp.MustCompile("\r?\n")

func testParsePKIMessage(t *testing.T, data []byte) *scep.PKIMessage {
	t.Helper()

	buf := bytes.Buffer{}
	logger := newTestLogger(&buf)
	msg, err := scep.ParsePKIMessage(data, scep.WithLogger(logger))
	if err != nil {
		t.Fatal(err)
	}

	validateParsedPKIMessage(t, msg)

	lines := newLines.Split(strings.TrimSpace(buf.String()), -1)
	if len(lines) != 1 {
		t.Errorf("expected single log line")
	}
	validateLogLevelDebug(t, lines)

	return msg
}

func validateParsedPKIMessage(t *testing.T, msg *scep.PKIMessage) {
	t.Helper()

	if msg.TransactionID == "" {
		t.Errorf("expected TransactionID attribute")
	}
	if msg.MessageType == "" {
		t.Errorf("expected MessageType attribute")
	}
	switch msg.MessageType {
	case scep.CertRep:
		if len(msg.RecipientNonce) == 0 {
			t.Errorf("expected RecipientNonce attribute")
		}
	case scep.PKCSReq, scep.UpdateReq, scep.RenewalReq:
		if len(msg.SenderNonce) == 0 {
			t.Errorf("expected SenderNonce attribute")
		}
	}
}

// textAttrs captures all key=value pairs produced the go-kit logger
var textAttrs = regexp.MustCompile(`(\w+(?:\.\w+)*)=("(?:\\"|[^"])*"|\[.*?\]|[^ ]+)`)

// splitTextAttrs splits the input string into key=value pairs. Every pair is
// returned as a single string.
func splitTextAttrs(input string) []string {
	return textAttrs.FindAllString(input, -1)
}

// validateLogLevelDebug validates the input string has the debug level
// set on each non-empty line.
func validateLogLevelDebug(t *testing.T, lines []string) {
	t.Helper()

	for _, line := range lines {
		if line == "" {
			continue
		}

		attrs := splitTextAttrs(line)
		countLogLevel := 0
		for _, a := range attrs {
			if a == "level=debug" {
				countLogLevel += 1
			}
		}

		if countLogLevel != 1 {
			t.Errorf("expected log level debug to be set once; found %d occurrences", countLogLevel)
		}
	}
}

// Tests the case when servers reply with PKCS #7 signed-data that contains no
// certificates assuming that the client can request CA certificates using
// GetCaCert request.
func TestParsePKIEnvelopeCert_MissingCertificatesForSigners(t *testing.T) {
	certRepMissingCertificates := readTestFile(t, "testca2/CertRep_NoCertificatesForSigners.der")
	caPEM := readTestFile(t, "testca2/ca2.pem")

	// Try to parse the PKIMessage without providing certificates for signers.
	_, err := scep.ParsePKIMessage(certRepMissingCertificates)
	if err == nil {
		t.Fatal("parsed PKIMessage without providing signer certificates")
	}

	signerCert := decodePEMCert(t, caPEM)
	msg, err := scep.ParsePKIMessage(certRepMissingCertificates, scep.WithCACerts([]*x509.Certificate{signerCert}))
	if err != nil {
		t.Fatalf("failed to parse PKIMessage: %v", err)
	}

	validateParsedPKIMessage(t, msg)
}

func TestDecryptPKIEnvelopeCSR(t *testing.T) {
	pkcsReq := readTestFile(t, "PKCSReq.der")
	msg := testParsePKIMessage(t, pkcsReq)
	cacert, cakey := loadCACredentials(t)
	err := msg.DecryptPKIEnvelope(cacert, cakey)
	if err != nil {
		t.Fatal(err)
	}
	if msg.CSRReqMessage.CSR == nil {
		t.Errorf("expected non-nil CSR field")
	}
}

func TestDecryptPKIEnvelopeDecrypter(t *testing.T) {
	pkcsReq := readTestFile(t, "PKCSReq.der")
	msg := testParsePKIMessage(t, pkcsReq)
	cacert, cakey := loadCACredentials(t)
	if err := msg.DecryptPKIEnvelope(nil, cakey); err == nil {
		t.Fatal("expected error on nil cert")
	}

	if err := msg.DecryptPKIEnvelope(cacert, nil); err == nil {
		t.Fatal("expected error on nil key")
	}

	if err := msg.DecryptPKIEnvelope(cacert, &notADecrypter{}); err == nil {
		t.Fatal("expected error on invalid decrypter")
	}

	if err := msg.DecryptPKIEnvelope(cacert, &nonRSADecrypter{}); err == nil {
		t.Fatal("expected error on non-RSA decrypter")
	}
}

type notADecrypter struct{}

type nonRSADecrypter struct{}

func (d *nonRSADecrypter) Public() crypto.PublicKey {
	return struct{}{}
}

func (d *nonRSADecrypter) Decrypt(_ io.Reader, _ []byte, _ crypto.DecrypterOpts) (plaintext []byte, err error) {
	return nil, errors.New("not implemented")
}

func TestDecryptPKIEnvelopeCert(t *testing.T) {
	certRep := readTestFile(t, "CertRep.der")
	testParsePKIMessage(t, certRep)
	// clientcert, clientkey := loadClientCredentials(t)
	// err = msg.DecryptPKIEnvelope(clientcert, clientkey)
	// if err != nil {
	// 	t.Fatal(err)
	// }
}

func TestSignCSR(t *testing.T) {
	pkcsReq := readTestFile(t, "PKCSReq.der")
	msg := testParsePKIMessage(t, pkcsReq)
	cacert, cakey := loadCACredentials(t)
	err := msg.DecryptPKIEnvelope(cacert, cakey)
	if err != nil {
		t.Fatal(err)
	}

	csr := msg.CSRReqMessage.CSR
	id, err := cryptoutil.GenerateSubjectKeyID(csr.PublicKey)
	if err != nil {
		t.Fatal(err)
	}
	tmpl := &x509.Certificate{
		SerialNumber: big.NewInt(4),
		Subject:      csr.Subject,
		NotBefore:    time.Now().Add(-600).UTC(),
		NotAfter:     time.Now().AddDate(1, 0, 0).UTC(),
		SubjectKeyId: id,
		ExtKeyUsage: []x509.ExtKeyUsage{
			x509.ExtKeyUsageAny,
			x509.ExtKeyUsageClientAuth,
		},
	}
	// sign the CSR creating a DER encoded cert
	crtBytes, err := x509.CreateCertificate(rand.Reader, tmpl, cacert, csr.PublicKey, cakey)
	if err != nil {
		t.Fatal(err)
	}
	crt, err := x509.ParseCertificate(crtBytes)
	if err != nil {
		t.Fatal(err)
	}
	certRep, err := msg.Success(cacert, cakey, crt)
	if err != nil {
		t.Fatal(err)
	}

	testParsePKIMessage(t, certRep.Raw)
}

func TestNewCSRRequest(t *testing.T) {
	t.Parallel()

	for _, test := range []struct {
		testName          string
		keyUsage          x509.KeyUsage
		certsSelectorFunc scep.CertsSelectorFunc
		shouldCreateCSR   bool
	}{
		{
			"KeyEncipherment not set with NOP certificates selector",
			x509.KeyUsageCertSign,
			scep.NopCertsSelector(),
			true,
		},
		{
			"KeyEncipherment is set with NOP certificates selector",
			x509.KeyUsageCertSign | x509.KeyUsageKeyEncipherment,
			scep.NopCertsSelector(),
			true,
		},
		{
			"KeyEncipherment not set with Encipherment certificates selector",
			x509.KeyUsageCertSign,
			scep.EnciphermentCertsSelector(),
			false,
		},
		{
			"KeyEncipherment is set with Encipherment certificates selector",
			x509.KeyUsageCertSign | x509.KeyUsageKeyEncipherment,
			scep.EnciphermentCertsSelector(),
			true,
		},
	} {
		test := test
		t.Run(test.testName, func(t *testing.T) {
			t.Parallel()

			key := newRSAKey(t, 2048)
			derBytes := newCSR(t, key, "john.doe@example.com", "US", "com.apple.2379B935-294B-4AF1-A213-9BD44A2C6688")
			csr, err := x509.ParseCertificateRequest(derBytes)
			if err != nil {
				t.Fatal(err)
			}
			clientcert, clientkey := loadClientCredentials(t)
			cacert, cakey := createCaCertWithKeyUsage(t, test.keyUsage)
			tmpl := &scep.PKIMessage{
				MessageType: scep.PKCSReq,
				Recipients:  []*x509.Certificate{cacert},
				SignerCert:  clientcert,
				SignerKey:   clientkey,
			}

			buf := bytes.Buffer{}
			logger := newTestLogger(&buf)
			pkcsreq, err := scep.NewCSRRequest(csr, tmpl, scep.WithCertsSelector(test.certsSelectorFunc), scep.WithLogger(logger))
			if test.shouldCreateCSR && err != nil {
				t.Fatalf("keyUsage: %d, failed creating a CSR request: %v", test.keyUsage, err)
			}
			if !test.shouldCreateCSR && err == nil {
				t.Fatalf("keyUsage: %d, shouldn't have created a CSR: %v", test.keyUsage, err)
			}
			if !test.shouldCreateCSR {
				return
			}

			lines := newLines.Split(strings.TrimSpace(buf.String()), -1)
			if len(lines) != 1 {
				t.Errorf("expected single log line")
			}
			validateLogLevelDebug(t, lines)

			msg := testParsePKIMessage(t, pkcsreq.Raw)
			err = msg.DecryptPKIEnvelope(cacert, cakey)
			if err != nil {
				t.Fatal(err)
			}
		})
	}
}

// create a new RSA private key
func newRSAKey(t *testing.T, bits int) *rsa.PrivateKey {
	t.Helper()

	private, err := rsa.GenerateKey(rand.Reader, bits)
	if err != nil {
		t.Fatal(err)
	}
	return private
}

// create a CSR using the same parameters as Keychain Access would produce
func newCSR(t *testing.T, priv *rsa.PrivateKey, email, country, cname string) []byte {
	t.Helper()

	template := &x509.CertificateRequest{
		Subject: pkix.Name{
			Country:    []string{country},
			CommonName: cname,
			ExtraNames: []pkix.AttributeTypeAndValue{{
				Type:  []int{1, 2, 840, 113549, 1, 9, 1},
				Value: email,
			}},
		},
	}
	der, err := x509.CreateCertificateRequest(rand.Reader, template, priv)
	if err != nil {
		t.Fatal(err)
	}
	return der
}

func readTestFile(t *testing.T, filepath string) []byte {
	t.Helper()

	data, err := os.ReadFile(path.Join("testdata", filepath))
	if err != nil {
		t.Fatal(err)
	}
	return data
}

// createCaCertWithKeyUsage generates a CA key and certificate with keyUsage.
func createCaCertWithKeyUsage(t *testing.T, keyUsage x509.KeyUsage) (*x509.Certificate, *rsa.PrivateKey) {
	t.Helper()

	key, err := rsa.GenerateKey(rand.Reader, 2048)
	if err != nil {
		t.Fatal(err)
	}

	// NOTE: this uses SHA256 instead of the SHA1 specified in RFC5280
	subjKeyID, err := cryptoutil.GenerateSubjectKeyID(key.Public())
	if err != nil {
		t.Fatal(err)
	}

	template := &x509.Certificate{
		Subject: pkix.Name{
			CommonName:   "MICROMDM SCEP CA",
			Country:      []string{"US"},
			Organization: []string{"MICROMDM"},
		},
		SerialNumber:          big.NewInt(1),
		KeyUsage:              keyUsage,
		NotBefore:             time.Now().Add(-600).UTC(),
		NotAfter:              time.Now().AddDate(1, 0, 0).UTC(), // + 1 year
		IsCA:                  true,
		BasicConstraintsValid: true,
		MaxPathLen:            0,
		SubjectKeyId:          subjKeyID,
	}

	crtBytes, err := x509.CreateCertificate(rand.Reader, template, template, key.Public(), key)
	if err != nil {
		t.Fatal(err)
	}
	cert, err := x509.ParseCertificate(crtBytes)
	if err != nil {
		t.Fatal(err)
	}
	return cert, key
}

func loadCACredentials(t *testing.T) (*x509.Certificate, *rsa.PrivateKey) {
	t.Helper()

	cert := loadCertFromFile(t, "testca/ca.crt")
	key := loadKeyFromFile(t, "testca/ca.key")
	return cert, key
}

func loadClientCredentials(t *testing.T) (*x509.Certificate, *rsa.PrivateKey) {
	t.Helper()

	cert := loadCertFromFile(t, "testclient/client.pem")
	key := loadKeyFromFile(t, "testclient/client.key")
	return cert, key
}

const (
	rsaPrivateKeyPEMBlockType = "RSA PRIVATE KEY"
	certificatePEMBlockType   = "CERTIFICATE"
)

func loadCertFromFile(t *testing.T, filepath string) *x509.Certificate {
	t.Helper()

	data := readTestFile(t, filepath)
	pemBlock, _ := pem.Decode(data)
	if pemBlock == nil {
		t.Fatal(fmt.Errorf("PEM decode failed for %q", filepath))
	}
	if pemBlock.Type != certificatePEMBlockType {
		t.Fatal(fmt.Errorf("unmatched type or headers in %q", filepath))
	}
	der, err := x509.ParseCertificate(pemBlock.Bytes)
	if err != nil {
		t.Fatal(err)
	}
	return der
}

// load an encrypted private key from disk
func loadKeyFromFile(t *testing.T, filepath string) *rsa.PrivateKey {
	t.Helper()

	data := readTestFile(t, filepath)
	pemBlock, _ := pem.Decode(data)
	if pemBlock == nil {
		t.Fatal(fmt.Errorf("PEM decode failed for %q", filepath))
	}
	if pemBlock.Type != rsaPrivateKeyPEMBlockType {
		t.Fatal(fmt.Errorf("unmatched type or headers in %q", filepath))
	}

	// testca key has a password
	if len(pemBlock.Headers) > 0 {
		password := []byte("")
		//nolint:staticcheck // required for legacy compatibility; can be replaced with pemutil.DecryptPEMBlock() from our crypto lib
		b, err := x509.DecryptPEMBlock(pemBlock, password)
		if err != nil {
			t.Fatal(err)
		}
		private, err := x509.ParsePKCS1PrivateKey(b)
		if err != nil {
			t.Fatal(err)
		}
		return private
	}

	private, err := x509.ParsePKCS1PrivateKey(pemBlock.Bytes)
	if err != nil {
		t.Fatal(err)
	}

	return private
}

func decodePEMCert(t *testing.T, data []byte) *x509.Certificate {
	t.Helper()

	pemBlock, _ := pem.Decode(data)
	if pemBlock == nil {
		t.Fatal(errors.New("PEM decode failed"))
	}
	if pemBlock.Type != certificatePEMBlockType {
		t.Fatal(errors.New("unmatched type or headers"))
	}

	cert, err := x509.ParseCertificate(pemBlock.Bytes)
	if err != nil {
		t.Fatal(err)
	}
	return cert
}