feat: implement internal PKI utilities for CA and certificate management

2025-05-16 20:47:57 -04:00 · 2025-05-16 20:47:57 -04:00 · 7adabe8630
commit 7adabe8630
parent 58bdca5703
4 changed files with 586 additions and 0 deletions
--- a/internal/pki/ca.go
+++ b/internal/pki/ca.go
@ -0,0 +1,166 @@
+package pki
+
+import (
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/pem"
+	"fmt"
+	"math/big"
+	"os"
+	"path/filepath"
+	"time"
+)
+
+const (
+	// Default key size for RSA keys
+	DefaultRSAKeySize = 2048
+	// Default CA certificate validity period
+	DefaultCAValidityDays = 3650 // ~10 years
+	// Default certificate validity period
+	DefaultCertValidityDays = 365 // 1 year
+	// Default PKI directory
+	DefaultPKIDir = "/var/lib/kat/pki"
+)
+
+// GenerateCA creates a new Certificate Authority key pair and certificate.
+// It saves the private key and certificate to the specified paths.
+func GenerateCA(pkiDir string, keyPath, certPath string) error {
+	// Create PKI directory if it doesn't exist
+	if err := os.MkdirAll(pkiDir, 0700); err != nil {
+		return fmt.Errorf("failed to create PKI directory: %w", err)
+	}
+
+	// Generate RSA key
+	key, err := rsa.GenerateKey(rand.Reader, DefaultRSAKeySize)
+	if err != nil {
+		return fmt.Errorf("failed to generate CA key: %w", err)
+	}
+
+	// Create self-signed certificate
+	serialNumber, err := generateSerialNumber()
+	if err != nil {
+		return fmt.Errorf("failed to generate serial number: %w", err)
+	}
+
+	// Certificate template
+	notBefore := time.Now()
+	notAfter := notBefore.Add(time.Duration(DefaultCAValidityDays) * 24 * time.Hour)
+
+	template := x509.Certificate{
+		SerialNumber: serialNumber,
+		Subject: pkix.Name{
+			CommonName:   "KAT Root CA",
+			Organization: []string{"KAT System"},
+		},
+		NotBefore:             notBefore,
+		NotAfter:              notAfter,
+		KeyUsage:              x509.KeyUsageCertSign | x509.KeyUsageCRLSign,
+		BasicConstraintsValid: true,
+		IsCA:                  true,
+		MaxPathLen:            1, // Only allow one level of intermediate certs
+	}
+
+	// Create certificate
+	derBytes, err := x509.CreateCertificate(
+		rand.Reader,
+		&template,
+		&template, // Self-signed
+		&key.PublicKey,
+		key,
+	)
+	if err != nil {
+		return fmt.Errorf("failed to create CA certificate: %w", err)
+	}
+
+	// Save private key
+	keyOut, err := os.OpenFile(keyPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
+	if err != nil {
+		return fmt.Errorf("failed to open CA key file for writing: %w", err)
+	}
+	defer keyOut.Close()
+
+	err = pem.Encode(keyOut, &pem.Block{
+		Type:  "RSA PRIVATE KEY",
+		Bytes: x509.MarshalPKCS1PrivateKey(key),
+	})
+	if err != nil {
+		return fmt.Errorf("failed to write CA key to file: %w", err)
+	}
+
+	// Save certificate
+	certOut, err := os.OpenFile(certPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644)
+	if err != nil {
+		return fmt.Errorf("failed to open CA certificate file for writing: %w", err)
+	}
+	defer certOut.Close()
+
+	err = pem.Encode(certOut, &pem.Block{
+		Type:  "CERTIFICATE",
+		Bytes: derBytes,
+	})
+	if err != nil {
+		return fmt.Errorf("failed to write CA certificate to file: %w", err)
+	}
+
+	return nil
+}
+
+// GetPKIPathFromClusterConfig determines the PKI directory from the cluster configuration.
+// If backupPath is provided, it uses the parent directory of backupPath.
+// Otherwise, it uses the default PKI directory.
+func GetPKIPathFromClusterConfig(backupPath string) string {
+	if backupPath == "" {
+		return DefaultPKIDir
+	}
+	
+	// Use the parent directory of backupPath
+	return filepath.Dir(backupPath) + "/pki"
+}
+
+// generateSerialNumber creates a random serial number for certificates
+func generateSerialNumber() (*big.Int, error) {
+	serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128) // 128 bits
+	return rand.Int(rand.Reader, serialNumberLimit)
+}
+
+// LoadCACertificate loads a CA certificate from a file
+func LoadCACertificate(certPath string) (*x509.Certificate, error) {
+	certPEM, err := os.ReadFile(certPath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read CA certificate file: %w", err)
+	}
+
+	block, _ := pem.Decode(certPEM)
+	if block == nil || block.Type != "CERTIFICATE" {
+		return nil, fmt.Errorf("failed to decode PEM block containing certificate")
+	}
+
+	cert, err := x509.ParseCertificate(block.Bytes)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse CA certificate: %w", err)
+	}
+
+	return cert, nil
+}
+
+// LoadCAPrivateKey loads a CA private key from a file
+func LoadCAPrivateKey(keyPath string) (*rsa.PrivateKey, error) {
+	keyPEM, err := os.ReadFile(keyPath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read CA key file: %w", err)
+	}
+
+	block, _ := pem.Decode(keyPEM)
+	if block == nil || block.Type != "RSA PRIVATE KEY" {
+		return nil, fmt.Errorf("failed to decode PEM block containing private key")
+	}
+
+	key, err := x509.ParsePKCS1PrivateKey(block.Bytes)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse CA private key: %w", err)
+	}
+
+	return key, nil
+}
--- a/internal/pki/ca_test.go
+++ b/internal/pki/ca_test.go
@ -0,0 +1,73 @@
+package pki
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestGenerateCA(t *testing.T) {
+	// Create a temporary directory for the test
+	tempDir, err := os.MkdirTemp("", "kat-pki-test")
+	if err != nil {
+		t.Fatalf("Failed to create temp directory: %v", err)
+	}
+	defer os.RemoveAll(tempDir)
+
+	// Define paths for CA key and certificate
+	keyPath := filepath.Join(tempDir, "ca.key")
+	certPath := filepath.Join(tempDir, "ca.crt")
+
+	// Generate CA
+	err = GenerateCA(tempDir, keyPath, certPath)
+	if err != nil {
+		t.Fatalf("GenerateCA failed: %v", err)
+	}
+
+	// Verify files exist
+	if _, err := os.Stat(keyPath); os.IsNotExist(err) {
+		t.Errorf("CA key file was not created at %s", keyPath)
+	}
+	if _, err := os.Stat(certPath); os.IsNotExist(err) {
+		t.Errorf("CA certificate file was not created at %s", certPath)
+	}
+
+	// Load and verify CA certificate
+	caCert, err := LoadCACertificate(certPath)
+	if err != nil {
+		t.Fatalf("Failed to load CA certificate: %v", err)
+	}
+
+	// Verify CA properties
+	if !caCert.IsCA {
+		t.Errorf("Certificate is not marked as CA")
+	}
+	if caCert.Subject.CommonName != "KAT Root CA" {
+		t.Errorf("Unexpected CA CommonName: got %s, want %s", caCert.Subject.CommonName, "KAT Root CA")
+	}
+	if len(caCert.Subject.Organization) == 0 || caCert.Subject.Organization[0] != "KAT System" {
+		t.Errorf("Unexpected CA Organization: got %v, want [KAT System]", caCert.Subject.Organization)
+	}
+
+	// Load and verify CA key
+	_, err = LoadCAPrivateKey(keyPath)
+	if err != nil {
+		t.Fatalf("Failed to load CA private key: %v", err)
+	}
+}
+
+func TestGetPKIPathFromClusterConfig(t *testing.T) {
+	// Test with empty backup path
+	pkiPath := GetPKIPathFromClusterConfig("")
+	if pkiPath != DefaultPKIDir {
+		t.Errorf("Expected default PKI path %s, got %s", DefaultPKIDir, pkiPath)
+	}
+
+	// Test with backup path
+	backupPath := "/opt/kat/backups"
+	expectedPKIPath := "/opt/kat/pki"
+	pkiPath = GetPKIPathFromClusterConfig(backupPath)
+	if pkiPath != expectedPKIPath {
+		t.Errorf("Expected PKI path %s, got %s", expectedPKIPath, pkiPath)
+	}
+}
--- a/internal/pki/certs.go
+++ b/internal/pki/certs.go
@ -0,0 +1,219 @@
+package pki
+
+import (
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/pem"
+	"fmt"
+	"net"
+	"os"
+	"time"
+)
+
+// GenerateCertificateRequest generates a new RSA key pair and a Certificate Signing Request (CSR).
+// It saves the private key and CSR to the specified paths.
+func GenerateCertificateRequest(commonName string, keyOutPath, csrOutPath string) error {
+	// Generate RSA key
+	key, err := rsa.GenerateKey(rand.Reader, DefaultRSAKeySize)
+	if err != nil {
+		return fmt.Errorf("failed to generate key: %w", err)
+	}
+
+	// Create CSR template
+	template := x509.CertificateRequest{
+		Subject: pkix.Name{
+			CommonName:   commonName,
+			Organization: []string{"KAT System"},
+		},
+		DNSNames: []string{commonName},
+	}
+
+	// Add IP addresses if commonName is an IP
+	if ip := net.ParseIP(commonName); ip != nil {
+		template.IPAddresses = []net.IP{ip}
+	}
+
+	// Create CSR
+	csrBytes, err := x509.CreateCertificateRequest(rand.Reader, &template, key)
+	if err != nil {
+		return fmt.Errorf("failed to create CSR: %w", err)
+	}
+
+	// Save private key
+	keyOut, err := os.OpenFile(keyOutPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
+	if err != nil {
+		return fmt.Errorf("failed to open key file for writing: %w", err)
+	}
+	defer keyOut.Close()
+
+	err = pem.Encode(keyOut, &pem.Block{
+		Type:  "RSA PRIVATE KEY",
+		Bytes: x509.MarshalPKCS1PrivateKey(key),
+	})
+	if err != nil {
+		return fmt.Errorf("failed to write key to file: %w", err)
+	}
+
+	// Save CSR
+	csrOut, err := os.OpenFile(csrOutPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644)
+	if err != nil {
+		return fmt.Errorf("failed to open CSR file for writing: %w", err)
+	}
+	defer csrOut.Close()
+
+	err = pem.Encode(csrOut, &pem.Block{
+		Type:  "CERTIFICATE REQUEST",
+		Bytes: csrBytes,
+	})
+	if err != nil {
+		return fmt.Errorf("failed to write CSR to file: %w", err)
+	}
+
+	return nil
+}
+
+// SignCertificateRequest signs a CSR using the CA key and certificate.
+// It loads the CA key and certificate from the specified paths,
+// parses the CSR data, and issues a signed certificate.
+func SignCertificateRequest(caKeyPath, caCertPath string, csrData []byte, certOutPath string, durationDays int) error {
+	// Load CA private key
+	caKey, err := LoadCAPrivateKey(caKeyPath)
+	if err != nil {
+		return err
+	}
+
+	// Load CA certificate
+	caCert, err := LoadCACertificate(caCertPath)
+	if err != nil {
+		return err
+	}
+
+	// Parse CSR
+	block, _ := pem.Decode(csrData)
+	if block == nil || block.Type != "CERTIFICATE REQUEST" {
+		return fmt.Errorf("failed to decode PEM block containing CSR")
+	}
+
+	csr, err := x509.ParseCertificateRequest(block.Bytes)
+	if err != nil {
+		return fmt.Errorf("failed to parse CSR: %w", err)
+	}
+
+	// Verify CSR signature
+	if err := csr.CheckSignature(); err != nil {
+		return fmt.Errorf("CSR signature verification failed: %w", err)
+	}
+
+	// Generate serial number
+	serialNumber, err := generateSerialNumber()
+	if err != nil {
+		return fmt.Errorf("failed to generate serial number: %w", err)
+	}
+
+	// Set certificate validity period
+	if durationDays <= 0 {
+		durationDays = DefaultCertValidityDays
+	}
+	notBefore := time.Now()
+	notAfter := notBefore.Add(time.Duration(durationDays) * 24 * time.Hour)
+
+	// Create certificate template
+	template := x509.Certificate{
+		SerialNumber:          serialNumber,
+		Subject:               csr.Subject,
+		NotBefore:             notBefore,
+		NotAfter:              notAfter,
+		KeyUsage:              x509.KeyUsageDigitalSignature | x509.KeyUsageKeyEncipherment,
+		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth, x509.ExtKeyUsageClientAuth},
+		BasicConstraintsValid: true,
+		IsCA:                  false,
+		DNSNames:              csr.DNSNames,
+		IPAddresses:           csr.IPAddresses,
+	}
+
+	// Create certificate
+	derBytes, err := x509.CreateCertificate(
+		rand.Reader,
+		&template,
+		caCert,
+		csr.PublicKey,
+		caKey,
+	)
+	if err != nil {
+		return fmt.Errorf("failed to create certificate: %w", err)
+	}
+
+	// Save certificate
+	certOut, err := os.OpenFile(certOutPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644)
+	if err != nil {
+		return fmt.Errorf("failed to open certificate file for writing: %w", err)
+	}
+	defer certOut.Close()
+
+	err = pem.Encode(certOut, &pem.Block{
+		Type:  "CERTIFICATE",
+		Bytes: derBytes,
+	})
+	if err != nil {
+		return fmt.Errorf("failed to write certificate to file: %w", err)
+	}
+
+	return nil
+}
+
+// ParseCSRFromBytes parses a PEM-encoded CSR from bytes
+func ParseCSRFromBytes(csrData []byte) (*x509.CertificateRequest, error) {
+	block, _ := pem.Decode(csrData)
+	if block == nil || block.Type != "CERTIFICATE REQUEST" {
+		return nil, fmt.Errorf("failed to decode PEM block containing CSR")
+	}
+
+	csr, err := x509.ParseCertificateRequest(block.Bytes)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse CSR: %w", err)
+	}
+
+	return csr, nil
+}
+
+// LoadCertificate loads an X.509 certificate from a file
+func LoadCertificate(certPath string) (*x509.Certificate, error) {
+	certPEM, err := os.ReadFile(certPath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read certificate file: %w", err)
+	}
+
+	block, _ := pem.Decode(certPEM)
+	if block == nil || block.Type != "CERTIFICATE" {
+		return nil, fmt.Errorf("failed to decode PEM block containing certificate")
+	}
+
+	cert, err := x509.ParseCertificate(block.Bytes)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse certificate: %w", err)
+	}
+
+	return cert, nil
+}
+
+// LoadPrivateKey loads an RSA private key from a file
+func LoadPrivateKey(keyPath string) (*rsa.PrivateKey, error) {
+	keyPEM, err := os.ReadFile(keyPath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read key file: %w", err)
+	}
+
+	block, _ := pem.Decode(keyPEM)
+	if block == nil || block.Type != "RSA PRIVATE KEY" {
+		return nil, fmt.Errorf("failed to decode PEM block containing private key")
+	}
+
+	key, err := x509.ParsePKCS1PrivateKey(block.Bytes)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse private key: %w", err)
+	}
+
+	return key, nil
+}
--- a/internal/pki/certs_test.go
+++ b/internal/pki/certs_test.go
@ -0,0 +1,128 @@
+package pki
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestGenerateCertificateRequest(t *testing.T) {
+	// Create a temporary directory for the test
+	tempDir, err := os.MkdirTemp("", "kat-csr-test")
+	if err != nil {
+		t.Fatalf("Failed to create temp directory: %v", err)
+	}
+	defer os.RemoveAll(tempDir)
+
+	// Define paths for key and CSR
+	keyPath := filepath.Join(tempDir, "node.key")
+	csrPath := filepath.Join(tempDir, "node.csr")
+	commonName := "test-node.kat.cluster.local"
+
+	// Generate CSR
+	err = GenerateCertificateRequest(commonName, keyPath, csrPath)
+	if err != nil {
+		t.Fatalf("GenerateCertificateRequest failed: %v", err)
+	}
+
+	// Verify files exist
+	if _, err := os.Stat(keyPath); os.IsNotExist(err) {
+		t.Errorf("Key file was not created at %s", keyPath)
+	}
+	if _, err := os.Stat(csrPath); os.IsNotExist(err) {
+		t.Errorf("CSR file was not created at %s", csrPath)
+	}
+
+	// Read CSR file
+	csrData, err := os.ReadFile(csrPath)
+	if err != nil {
+		t.Fatalf("Failed to read CSR file: %v", err)
+	}
+
+	// Parse CSR
+	csr, err := ParseCSRFromBytes(csrData)
+	if err != nil {
+		t.Fatalf("Failed to parse CSR: %v", err)
+	}
+
+	// Verify CSR properties
+	if csr.Subject.CommonName != commonName {
+		t.Errorf("Unexpected CSR CommonName: got %s, want %s", csr.Subject.CommonName, commonName)
+	}
+	if len(csr.DNSNames) == 0 || csr.DNSNames[0] != commonName {
+		t.Errorf("Unexpected CSR DNSNames: got %v, want [%s]", csr.DNSNames, commonName)
+	}
+}
+
+func TestSignCertificateRequest(t *testing.T) {
+	// Create a temporary directory for the test
+	tempDir, err := os.MkdirTemp("", "kat-cert-test")
+	if err != nil {
+		t.Fatalf("Failed to create temp directory: %v", err)
+	}
+	defer os.RemoveAll(tempDir)
+
+	// Generate CA
+	caKeyPath := filepath.Join(tempDir, "ca.key")
+	caCertPath := filepath.Join(tempDir, "ca.crt")
+	err = GenerateCA(tempDir, caKeyPath, caCertPath)
+	if err != nil {
+		t.Fatalf("GenerateCA failed: %v", err)
+	}
+
+	// Generate CSR
+	nodeKeyPath := filepath.Join(tempDir, "node.key")
+	csrPath := filepath.Join(tempDir, "node.csr")
+	commonName := "test-node.kat.cluster.local"
+	err = GenerateCertificateRequest(commonName, nodeKeyPath, csrPath)
+	if err != nil {
+		t.Fatalf("GenerateCertificateRequest failed: %v", err)
+	}
+
+	// Read CSR file
+	csrData, err := os.ReadFile(csrPath)
+	if err != nil {
+		t.Fatalf("Failed to read CSR file: %v", err)
+	}
+
+	// Sign CSR
+	certPath := filepath.Join(tempDir, "node.crt")
+	err = SignCertificateRequest(caKeyPath, caCertPath, csrData, certPath, 30) // 30 days validity
+	if err != nil {
+		t.Fatalf("SignCertificateRequest failed: %v", err)
+	}
+
+	// Verify certificate file exists
+	if _, err := os.Stat(certPath); os.IsNotExist(err) {
+		t.Errorf("Certificate file was not created at %s", certPath)
+	}
+
+	// Load and verify certificate
+	cert, err := LoadCertificate(certPath)
+	if err != nil {
+		t.Fatalf("Failed to load certificate: %v", err)
+	}
+
+	// Verify certificate properties
+	if cert.Subject.CommonName != commonName {
+		t.Errorf("Unexpected certificate CommonName: got %s, want %s", cert.Subject.CommonName, commonName)
+	}
+	if cert.IsCA {
+		t.Errorf("Certificate should not be a CA")
+	}
+	if len(cert.DNSNames) == 0 || cert.DNSNames[0] != commonName {
+		t.Errorf("Unexpected certificate DNSNames: got %v, want [%s]", cert.DNSNames, commonName)
+	}
+
+	// Load CA certificate to verify chain
+	caCert, err := LoadCACertificate(caCertPath)
+	if err != nil {
+		t.Fatalf("Failed to load CA certificate: %v", err)
+	}
+
+	// Verify certificate is signed by CA
+	err = cert.CheckSignatureFrom(caCert)
+	if err != nil {
+		t.Errorf("Certificate signature verification failed: %v", err)
+	}
+}