I have encrypted string and asymmetric RSA key. The string was encrypted by PHP and its function openssl_public_encrypt with public part of the key and PKCS#1 v1.5 padding. I want to decrypt encrypted string with Go lang and private part of the key.

I know how to decrypt it in PHP:

<?php

$encrypted = file_get_contents('./encryptedString.txt');
$privKey = file_get_contents('./private.key');

openssl_private_decrypt(base64_decode($encrypted), $decrypted, $privKey);

print_r($decrypted);

I know how to decrypt it in Bash:

#!/bin/bash

cat encryptedString.txt | base64 -d > encryptedString64.txt
openssl rsautl -decrypt -in ./encryptedString64.txt -inkey ./private.key

I want to decrypt the string in the same way in GO lang. I've already tried some function from crypto/rsa package:

func DecryptString(privKey *rsa.PrivateKey, encryptedString []byte) ([]byte, error) {

    decryptedBytes, err := rsa.DecryptOAEP(sha256.New(), nil, privKey, encryptedString, nil)
    if err != nil {
        return nil, err
    }

    return decryptedBytes, nil
}

func GetPrivateKey() (*rsa.PrivateKey, error) {
    pemString := `******************`

    block, _ := pem.Decode([]byte(pemString))
    parseResult, _ := x509.ParsePKCS8PrivateKey(block.Bytes)
    key := parseResult.(*rsa.PrivateKey)

    return key, nil
}

...but I'm still getting error "crypto/rsa: decryption error" or empty results. What am I missing?

CodePudding user response：

Thank you all for your comments. I have solved it and I am posting the solution below.

func main() {
    privateKeyB, err := ioutil.ReadFile("private.key")
    if err != nil {
        log.Fatal("Failed to read private key - "   err.Error())
    }
    block, _ := pem.Decode(privateKeyB)
    parseResult, err := x509.ParsePKCS8PrivateKey(block.Bytes)
    if err != nil {
        log.Fatal("Failed to parse private key - "   err.Error())
    }
    privateKey := parseResult.(*rsa.PrivateKey)

    encStringB, err := ioutil.ReadFile("encryptedString.txt")
    if err != nil {
        log.Fatal("Failed to read encrypted string - "   err.Error())
    }
    encString64, err := base64.StdEncoding.DecodeString(string(encStringB))
    if err != nil {
        log.Fatal("Failed to decode encrypted string to base64 - "   err.Error())
    }

    decryptedB, err := rsa.DecryptPKCS1v15(rand.Reader, privateKey, encString64)
    if err != nil {
        log.Fatal("Failed to decrypt string - "   err.Error())
    }

    fmt.Println(string(decryptedB))
}