add cert pkg to implement mtls

Signed-off-by: rksharma95 <ramakant@accuknox.com>

KubeArmor/cert/cert.go

@@ -0,0 +1,211 @@
+// SPDX-License-Identifier: Apache-2.0
+// Copyright 2022 Authors of KubeArmor
+
+// Package cert is responsible for generating certs dynamically and loading the certs from external sources.
+
+package cert
+
+import (
+	"context"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/pem"
+	"fmt"
+	"math/big"
+	"net"
+	"os"
+	"path/filepath"
+	"time"
+
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/client-go/kubernetes"
+)
+
+const (
+	// ORG kubearmor
+	KubeArmor_ORG string = "kubearmor"
+	KubeArmor_CN  string = "kubearmor"
+)
+
+var DefaultKubeArmorServerConfig = CertConfig{
+	CN:           KubeArmor_CN,
+	Organization: KubeArmor_ORG,
+	KeyUsage:     x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
+	ExtKeyUsage:  []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
+}
+
+var DefaultKubeArmorClientConfig = CertConfig{
+	CN:           KubeArmor_CN,
+	Organization: KubeArmor_ORG,
+	KeyUsage:     x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
+	ExtKeyUsage:  []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth},
+}
+
+var DefaultKubeArmorCAConfig = CertConfig{
+	CN:           KubeArmor_CN,
+	Organization: KubeArmor_ORG,
+	KeyUsage:     x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature | x509.KeyUsageCertSign,
+}
+
+type CertConfig struct {
+	CN           string // Common Name
+	Organization string
+	DNS          []string
+	IPs          []string
+	KeyUsage     x509.KeyUsage
+	ExtKeyUsage  []x509.ExtKeyUsage
+	NotAfter     time.Time
+}
+
+// CertKeyPair type
+type CertKeyPair struct {
+	Crt *x509.Certificate
+	Key *rsa.PrivateKey
+}
+
+// CertBytes type
+type CertBytes struct {
+	Crt []byte
+	Key []byte
+}
+
+type CertPath struct {
+	Base     string
+	CertFile string
+	KeyFile  string // Not Required if CertOnly:true
+	CertOnly bool   // if true read certificate only
+}
+
+func GetCertKeyPairFromCertBytes(certBytes *CertBytes) (*CertKeyPair, error) {
+	// Parse CA certificate and key
+	certPem, _ := pem.Decode(certBytes.Crt)
+	keyPem, _ := pem.Decode(certBytes.Key)
+
+	crt, err := x509.ParseCertificate(certPem.Bytes)
+	if err != nil {
+		fmt.Println("Error parsing CA certificate:", err)
+		return nil, err
+	}
+
+	key, err := x509.ParsePKCS1PrivateKey(keyPem.Bytes)
+	if err != nil {
+		fmt.Println("Error parsing CA private key:", err)
+		return nil, err
+	}
+
+	return &CertKeyPair{
+		Crt: crt,
+		Key: key,
+	}, nil
+}
+
+// ReadCertFromFile func reads certificate key pair from the given path
+func ReadCertFromFile(certPath *CertPath) (*CertBytes, error) {
+	var certBytes, keyBytes []byte
+	certFile := filepath.Clean(filepath.Join(certPath.Base, certPath.CertFile))
+	keyFile := filepath.Clean(filepath.Join(certPath.Base, certPath.KeyFile))
+
+	// Check if certificate file exists
+	if _, err := os.Stat(certFile); os.IsNotExist(err) {
+		fmt.Println("certificate file does not exist:", err)
+		return nil, err
+	}
+
+	certBytes, err := os.ReadFile(certFile)
+	if err != nil {
+		fmt.Println("Error reading CA certificate file:", err)
+		return nil, err
+	}
+
+	if !certPath.CertOnly {
+		// Check if key file exists
+		if _, err := os.Stat(keyFile); os.IsNotExist(err) {
+			fmt.Println("CA key file does not exist:", err)
+			return nil, err
+		}
+
+		keyBytes, err = os.ReadFile(keyFile)
+		if err != nil {
+			fmt.Println("Error reading CA key file:", err)
+			return nil, err
+		}
+	}
+
+	return &CertBytes{
+		Crt: certBytes,
+		Key: keyBytes,
+	}, nil
+}
+
+// ReadCertFromK8sSecret func reads cert from the k8s tls secret
+// it assumes the cert and key file exists with tls.crt and tls.key names respectively
+// that is true in case of kubernetes.io/tls secret type,
+// https://kubernetes.io/docs/concepts/configuration/secret/#tls-secrets
+func ReadCertFromK8sSecret(client *kubernetes.Clientset, namespace, secret string) (*CertBytes, error) {
+
+	// get secret
+	cert, err := client.CoreV1().Secrets(namespace).Get(context.Background(), secret, metav1.GetOptions{})
+	if err != nil {
+		return nil, err
+	}
+
+	return &CertBytes{
+		Crt: cert.Data["tls.crt"],
+		Key: cert.Data["tls.key"],
+	}, nil
+}
+
+func GenerateCert(cfg *CertConfig) (*CertKeyPair, error) {
+	// Generate a new RSA private key for the server
+	key, err := rsa.GenerateKey(rand.Reader, 2048)
+	if err != nil {
+		fmt.Println("error generating cert private key:", err)
+		return nil, err
+	}
+
+	// Create a template for the certificate
+	template := x509.Certificate{
+		SerialNumber:          big.NewInt(1),
+		Subject:               pkix.Name{CommonName: cfg.CN, Organization: []string{cfg.Organization}},
+		NotBefore:             time.Now(),
+		NotAfter:              cfg.NotAfter,
+		KeyUsage:              cfg.KeyUsage,
+		ExtKeyUsage:           cfg.ExtKeyUsage,
+		BasicConstraintsValid: true,
+	}
+
+	for _, ip := range cfg.IPs {
+		template.IPAddresses = append(template.IPAddresses, net.ParseIP(ip))
+	}
+
+	return &CertKeyPair{Crt: &template, Key: key}, nil
+}
+
+// GenerateSelfSignedCert func generates cert and key signed by provided CA
+func GenerateSelfSignedCert(ca *CertKeyPair, cfg *CertConfig) (*CertBytes, error) {
+	certKeyPair, err := GenerateCert(cfg)
+	if err != nil {
+		return nil, err
+	}
+
+	// Create the certificate signed by the CA
+	certBytes, err := x509.CreateCertificate(rand.Reader, certKeyPair.Crt, ca.Crt, &certKeyPair.Key.PublicKey, ca.Key)
+	if err != nil {
+		fmt.Println("Error creating certificate:", err)
+		return nil, err
+	}
+
+	certPEM := pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: certBytes})
+	keyPEM := pem.EncodeToMemory(&pem.Block{Type: "RSA PRIVATE KEY", Bytes: x509.MarshalPKCS1PrivateKey(certKeyPair.Key)})
+
+	if certPEM == nil || keyPEM == nil {
+		return nil, fmt.Errorf("error encoding certificate")
+	}
+
+	return &CertBytes{
+		Crt: certPEM,
+		Key: keyPEM,
+	}, nil
+}

KubeArmor/cert/certloader.go

@@ -0,0 +1,108 @@
+// SPDX-License-Identifier: Apache-2.0
+// Copyright 2022 Authors of KubeArmor
+
+// Package cert is responsible for generating certs dynamically and loading the certs from external sources.
+package cert
+
+import (
+	"crypto/tls"
+	"crypto/x509"
+
+	"k8s.io/client-go/kubernetes"
+)
+
+type CertLoader interface {
+	GetCertificateAndCaPool() (*tls.Certificate, *x509.CertPool, error)
+}
+
+// generate self sign certificate dynamically
+type SelfSignedCertLoader struct {
+	CaCertPath CertPath
+	CertConfig CertConfig
+}
+
+func (loader *SelfSignedCertLoader) GetCertificateAndCaPool() (*tls.Certificate, *x509.CertPool, error) {
+	// load ca certificate and ca key from given path
+	caCertBytes, err := ReadCertFromFile(&loader.CaCertPath)
+	if err != nil {
+		return nil, nil, err
+	}
+	caCert, err := GetCertKeyPairFromCertBytes(caCertBytes)
+	if err != nil {
+		return nil, nil, err
+	}
+	caCertPool := x509.NewCertPool()
+	caCertPool.AddCert(caCert.Crt)
+	// create certificate signed with provided ca certificate
+	certBytes, err := GenerateSelfSignedCert(caCert, &loader.CertConfig)
+	if err != nil {
+		return nil, nil, err
+	}
+	cert, err := tls.X509KeyPair(certBytes.Crt, certBytes.Key)
+	if err != nil {
+		return nil, nil, err
+	}
+	return &cert, caCertPool, nil
+}
+
+// load certificates provided by external source using file
+type ExternalCertLoader struct {
+	CaCertPath CertPath
+	CertPath   CertPath
+}
+
+func (loader *ExternalCertLoader) GetCertificateAndCaPool() (*tls.Certificate, *x509.CertPool, error) {
+	// load ca certificate from cert path, assuming only ca.crt is present
+	loader.CaCertPath.CertOnly = true
+	caCertBytes, err := ReadCertFromFile(&loader.CaCertPath)
+	if err != nil {
+		return nil, nil, err
+	}
+	caCert, err := GetCertKeyPairFromCertBytes(caCertBytes)
+	if err != nil {
+		return nil, nil, err
+	}
+	caCertPool := x509.NewCertPool()
+	caCertPool.AddCert(caCert.Crt)
+	// load server/client certificate from cert path
+	certBytes, err := ReadCertFromFile(&loader.CertPath)
+	if err != nil {
+		return nil, nil, err
+	}
+	cert, err := tls.X509KeyPair(certBytes.Crt, certBytes.Key)
+	if err != nil {
+		return nil, nil, err
+	}
+	return &cert, caCertPool, nil
+}
+
+type K8sCertLoader struct {
+	CertConfig CertConfig
+	K8sClient  *kubernetes.Clientset
+	Namespace  string
+	Secret     string
+}
+
+func (loader *K8sCertLoader) GetCertificateAndCaPool() (*tls.Certificate, *x509.CertPool, error) {
+	// load certificate from k8s secret
+	caCertBytes, err := ReadCertFromK8sSecret(loader.K8sClient, loader.Namespace, loader.Secret)
+	if err != nil {
+		return nil, nil, err
+	}
+	caCert, err := GetCertKeyPairFromCertBytes(caCertBytes)
+	if err != nil {
+		return nil, nil, err
+	}
+	caCertPool := x509.NewCertPool()
+	caCertPool.AddCert(caCert.Crt)
+	// create certificate signed with provided ca certificate
+	certBytes, err := GenerateSelfSignedCert(caCert, &loader.CertConfig)
+	if err != nil {
+		return nil, nil, err
+	}
+	cert, err := tls.X509KeyPair(certBytes.Crt, certBytes.Key)
+	if err != nil {
+		return nil, nil, err
+	}
+	return &cert, caCertPool, nil
+}