Golang rsa 验证

一下代码用于rsa 签名的验签，

签名可以用其他语言产生。也可以用golang生成。

package main

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

func ParseRsaPublicKeyFromPemStr(pubPEM string) (*rsa.PublicKey, error) {
	block, _ := pem.Decode([]byte(pubPEM))
	if block == nil {
		return nil, errors.New("failed to parse PEM block containing the key")
	}

	pub, err := x509.ParsePKCS1PublicKey(block.Bytes)
	if err != nil {
		return nil, err
	}
	return pub, nil

	// switch pub := pub.(type) {
	// case *rsa.PublicKey:
	// 	return pub, nil
	// default:
	// 	break // fall through
	// }
	// return nil, errors.New("Key type is not RSA")
}

func main() {
	// The GenerateKey method takes in a reader that returns random bits, and
	// the number of bits
	// privateKey, err := rsa.GenerateKey(rand.Reader, 2048)
	// if err != nil {
	// 	panic(err)
	// }

	// The public key is a part of the *rsa.PrivateKey struct
	// publicKey := privateKey.PublicKey

	publicKey, err := ParseRsaPublicKeyFromPemStr(`-----BEGIN RSA PUBLIC KEY-----
MIIBxxxxxx
-----END RSA PUBLIC KEY-----`)
	if err != nil {
		panic(err)
	}
	// // use the public and private keys
	// // ...
	// // https://play.golang.org/p/tldFUt2c4nx
	// modulusBytes := base64.StdEncoding.EncodeToString(privateKey.N.Bytes())
	// privateExponentBytes := base64.StdEncoding.EncodeToString(privateKey.D.Bytes())
	// fmt.Println(modulusBytes)
	// fmt.Println(privateExponentBytes)
	// fmt.Println(publicKey.E)

	// encryptedBytes, err := rsa.EncryptOAEP(
	// 	sha256.New(),
	// 	rand.Reader,
	// 	&publicKey,
	// 	[]byte("super secret message111"),
	// 	nil)
	// if err != nil {
	// 	panic(err)
	// }

	// fmt.Println("encrypted bytes: ", encryptedBytes)

	// // The first argument is an optional random data generator (the rand.Reader we used before)
	// // we can set this value as nil
	// // The OEAPOptions in the end signify that we encrypted the data using OEAP, and that we used
	// // SHA256 to hash the input.
	// decryptedBytes, err := privateKey.Decrypt(nil, encryptedBytes, &rsa.OAEPOptions{Hash: crypto.SHA256})
	// if err != nil {
	// 	panic(err)
	// }

	// // We get back the original information in the form of bytes, which we
	// // the cast to a string and print
	// fmt.Println("decrypted message: ", string(decryptedBytes))

	msg := []byte(`{"user_agent":"test"}`)

	// // Before signing, we need to hash our message
	// // The hash is what we actually sign
	msgHash := sha256.New()
	_, err = msgHash.Write(msg)
	if err != nil {
		panic(err)
	}
	msgHashSum := msgHash.Sum(nil)

	// // In order to generate the signature, we provide a random number generator,
	// // our private key, the hashing algorithm that we used, and the hash sum
	// // of our message
	// signature, err := rsa.SignPSS(rand.Reader, privateKey, crypto.SHA256, msgHashSum, nil)
	// if err != nil {
	// 	panic(err)
	// }

	signature := []byte{27, 79, , 8}

	// To verify the signature, we provide the public key, the hashing algorithm
	// the hash sum of our message and the signature we generated previously
	// there is an optional "options" parameter which can omit for now
	err = rsa.VerifyPSS(publicKey, crypto.SHA256, msgHashSum, signature, nil)
	if err != nil {
		fmt.Println("could not verify signature: ", err)
		return
	}
	// If we don't get any error from the `VerifyPSS` method, that means our
	// signature is valid
	fmt.Println("signature verified")
}

参考：
https://gist.github.com/sohamkamani/08377222d5e3e6bc130827f83b0c073e