RSAUtil

RSAUtil.go

package RSAUtil

import (
	"crypto"
	"crypto/rand"
	"crypto/rsa"
	"crypto/sha256"
	"crypto/x509"
	"encoding/pem"
	"errors"
	"log"
)

func GenerateKeyPair(bits int) (*rsa.PrivateKey, *rsa.PublicKey) {
	privkey, err := rsa.GenerateKey(rand.Reader, bits)
	if err != nil {
		log.Fatal(err)
	}

	return privkey, &privkey.PublicKey
}

func PrivateKeyToBytes(priv *rsa.PrivateKey) []byte {
	privBytes := pem.EncodeToMemory(
		&pem.Block{
			Type:  "RSA PRIVATE KEY",
			Bytes: x509.MarshalPKCS1PrivateKey(priv),
		},
	)

	return privBytes
}

func PublicKeyToBytes(pub *rsa.PublicKey) []byte {
	pubASN1, err := x509.MarshalPKIXPublicKey(pub)
	if err != nil {
		log.Fatal(err)
	}

	pubBytes := pem.EncodeToMemory(&pem.Block{
		Type:  "RSA PUBLIC KEY",
		Bytes: pubASN1,
	})

	return pubBytes
}

func BytesToPrivateKey(priv []byte) *rsa.PrivateKey {
	block, _ := pem.Decode(priv)
	enc := x509.IsEncryptedPEMBlock(block)
	b := block.Bytes
	var err error
	if enc {
		log.Println("is encrypted pem block")
		b, err = x509.DecryptPEMBlock(block, nil)
		if err != nil {
			log.Fatal(err)
		}
	}
	key, err := x509.ParsePKCS1PrivateKey(b)
	if err != nil {
		log.Fatal(err)
	}

	return key
}

func BytesToPublicKey(pub []byte) *rsa.PublicKey {
	block, _ := pem.Decode(pub)
	enc := x509.IsEncryptedPEMBlock(block)
	b := block.Bytes
	var err error
	if enc {
		log.Println("is encrypted pem block")
		b, err = x509.DecryptPEMBlock(block, nil)
		if err != nil {
			log.Fatal(err)
		}
	}
	ifc, err := x509.ParsePKIXPublicKey(b)
	if err != nil {
		log.Fatal(err)
	}
	key, ok := ifc.(*rsa.PublicKey)
	if !ok {
		log.Fatal("not ok")
	}

	return key
}

func EncryptWithPublicKey(origData []byte, pubKey []byte) ([]byte, error) {
	block, _ := pem.Decode(pubKey)
	if block == nil {
		return nil, errors.New("public key error")
	}
	pubInterface, err := x509.ParsePKIXPublicKey(block.Bytes)
	if err != nil {
		return nil, err
	}
	pub := pubInterface.(*rsa.PublicKey)

	return rsa.EncryptPKCS1v15(rand.Reader, pub, origData)
}

func DecryptWithPrivateKey(ciphertext []byte, privKey []byte) ([]byte, error) {
	block, _ := pem.Decode(privKey)
	if block == nil {
		return nil, errors.New("private key error!")
	}
	priv, err := x509.ParsePKCS1PrivateKey(block.Bytes)
	if err != nil {
		return nil, err
	}

	return rsa.DecryptPKCS1v15(rand.Reader, priv, ciphertext)
}

func Sign(origData []byte, privateKey *rsa.PrivateKey) ([]byte, error) {
	h := sha256.New()
	h.Write(origData)
	digest := h.Sum(nil)

	s, err := rsa.SignPKCS1v15(nil, privateKey, crypto.SHA256, digest)
	if err != nil {
		log.Fatal("rsaSign SignPKCS1v15 error")
	}

	return s, nil
}

func SignVerify(origData []byte, signedData []byte, publicKey []byte) error {
	hashed := sha256.Sum256(origData)
	block, _ := pem.Decode(publicKey)
	if block == nil {
		return errors.New("public key error")
	}
	pubInterface, err := x509.ParsePKIXPublicKey(block.Bytes)
	if err != nil {
		return err
	}
	pub := pubInterface.(*rsa.PublicKey)
	return rsa.VerifyPKCS1v15(pub, crypto.SHA256, hashed[:], signedData)
}

func GetPublicKeyFromCrt(crt []byte) *rsa.PublicKey {
	block, _ := pem.Decode(crt)
	var cert *x509.Certificate
	cert, _ = x509.ParseCertificate(block.Bytes)
	rsaPublicKey := cert.PublicKey.(*rsa.PublicKey)

	return rsaPublicKey
}