CODEWITHSUNDEEP
goencryptionrsa
Temuujin Oyuntsetseg
Temuujin Oyuntsetseg

Reputation: 41

the function x509.ParsePKCS8PrivateKey return rsa.privateKey. But can't use in the encryptPKCS1v15 function

const strPrivateKey = "30820b82020100300d06092a864886f70d010101050004820b6c30820b680201000282028100acfc585f43ca36ec2dddc518b5c7d1303b658faec58b634aff16ce4b7930b93a23517f8d9c8a260f4e2eb44b01da5b6588fefe63acb68c15677"

decoded, err := hex.DecodeString(strPrivateKey)
if err != nil {
    return ""
}
privateKey, err := x509.ParsePKCS8PrivateKey(decoded)
if err != nil {
    return ""
}

encypt, err := rsa.EncryptPKCS1v15(rand.Reader, &privateKey.PublicKey, data)
if err != nil {
    fmt.Println(err)
    return ""
}


privateKey.PublicKey undefined (type any has no field or method PublicKey)

Upvotes: 2

Views: 2798

Answers (2)

Temuujin Oyuntsetseg
Temuujin Oyuntsetseg

Reputation: 41

*correct answer. I resolved privateKey.(rsa.PrivateKey)

decodedString, err := hex.DecodeString(utility.StrPrivateKey)
if err != nil {
    return err
}
pkcs8PrivateKey, err := x509.ParsePKCS8PrivateKey(decodedString)
if err != nil {
    return err
}
privateKey := pkcs8PrivateKey.(*rsa.PrivateKey)

Upvotes: 0

Zeke Lu
Zeke Lu

Reputation: 7475

According to the doc (https://pkg.go.dev/crypto/[email protected]#ParsePKCS8PrivateKey):

func ParsePKCS8PrivateKey(der []byte) (key any, err error)

... It returns a *rsa.PrivateKey, a *ecdsa.PrivateKey, or a ed25519.PrivateKey. More types might be supported in the future.

You should use type assertion to check the type of the key:

switch privateKey := privateKey.(type) {
case *rsa.PrivateKey:
    // ...
case *ecdsa.PrivateKey:
    // ...
case ed25519.PrivateKey:
    // ...
default:
    panic("unknown key")
}

Since rsa.EncryptPKCS1v15 expects a *rsa.PublicKey, your code can be written like this:

if privateKey, ok := privateKey.(*rsa.PrivateKey); ok {
    encypt, err := rsa.EncryptPKCS1v15(rand.Reader, &privateKey.PublicKey, data)
}

BTW, the provided strPrivateKey is invalid (encoding/hex: odd length hex string). You can get some valid private keys from https://github.com/golang/go/blob/1c05968c9a5d6432fc6f30196528f8f37287dd3d/src/crypto/x509/pkcs8_test.go#L52-L124

Upvotes: 1

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