GO - How to convert public key from string to PEM format - go

I am trying to use jwt library to do jwt validation. And i am getting public key from another application by calling its REST endpoint which is returning public key in string format.
So now when trying to send that public key in same string format, i am getting "Invalid key format". Any help on how to convert string formatted key to a valid PEM format would be great.
func (test *TESTStrategy) doJWTValidation(token string, key string, logger *util.Logger) (TESTResponse, error) {
parsedToken, jwtErr := jwt.Parse(token, func(token *jwt.Token) (interface{}, error) {
return decodedJWT.ParsedPubKey, nil
})
Below is the error what i am getting when passing key as a string to jwt.Pasrse() call.
Public Key:
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAsFWkb/eSl6I3DRVhaonW3DFy8EnL0yaPiDzCcOLuYfBjN9zZIR1wXmnMJFle1K89qHGg42wgweVTIwA1XFTfoUKSziwsjF6FscZX5H56ZYyS/wWiO3rWWynlfbSZt+ga71+ndsu+A0Dy7Nn7ZgP8kRsu4UM5vE7QQTRERNiUKpzScN1cgZUFUqSddQmkwTEN8hH1mFX1Mum54NGqWIlmQxQDrOyogmMXIaaakhabcmuIPMULVVDVwUJC9sSDsc/j05qcZn3kkiEBRyiYB6ZLY2W7WfiV+dB7/icPONsYSD0FxHWEGNnbqtiGoNf9WZWtaP+o8WMR9sB3GKGVnbLvbQIDAQAB

That's a PEM encoded key, it's just missing the BEGIN & END headers. The key is simple Base64 encoded, you can decode and unmarshal into a RSA key as follows:
base64Data := []byte(`MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAsFWkb/eSl6I3DRVhaonW3DFy8EnL0yaPiDzCcOLuYfBjN9zZIR1wXmnMJFle1K89qHGg42wgweVTIwA1XFTfoUKSziwsjF6FscZX5H56ZYyS/wWiO3rWWynlfbSZt+ga71+ndsu+A0Dy7Nn7ZgP8kRsu4UM5vE7QQTRERNiUKpzScN1cgZUFUqSddQmkwTEN8hH1mFX1Mum54NGqWIlmQxQDrOyogmMXIaaakhabcmuIPMULVVDVwUJC9sSDsc/j05qcZn3kkiEBRyiYB6ZLY2W7WfiV+dB7/icPONsYSD0FxHWEGNnbqtiGoNf9WZWtaP+o8WMR9sB3GKGVnbLvbQIDAQAB`)
d := make([]byte, base64.StdEncoding.DecodedLen(len(base64Data)))
n, err := base64.StdEncoding.Decode(d, base64Data)
if err != nil {
// Handle error
}
d = d[:n]
key,err:=x509.ParsePKIXPublicKey(d)
if err != nil {
// Handle error
}
fmt.Println(key)
If you need the key in PEM encoded form, simple add the appropriate header and footer, e.g. -----BEGIN PUBLIC KEY----- & -----END PUBLIC KEY-----. Note that the BEGIN header must start on its own line and end in a new line ("\n"). The END header must also be proceeded by a new line.

Related

Invalid signature when signing Coinbase request, why?

According to Coinbase pro API docs:
The CB-ACCESS-SIGN header is generated by creating a sha256 HMAC using the base64-decoded secret key on the prehash string timestamp +
method + requestPath + body (where + represents string concatenation)
and base64-encode the output. The timestamp value is the same as the
CB-ACCESS-TIMESTAMP header.
The body is the request body string or omitted if there is no request
body (typically for GET requests).
The method should be UPPER CASE.
I borrowed a signing function from a better programmer and feed it something like this:
1619383731POST/reports{{"end_date":"2021-01-02T11:59:59Z","start_date":"2020-01-01T00:00:00Z","type":"account"}}
But keep getting invalid signature from Coinbase.
Signing function for reference:
// sign
func (e *exchange) sign(msg string) string {
key, err := base64.StdEncoding.DecodeString(e.http.secret)
if e.checkErr(err) {
return "bad_sig"
}
signature := hmac.New(sha256.New, key)
_, err = signature.Write([]byte(msg))
if e.checkErr(err) {
return "bad_sig"
}
return base64.StdEncoding.EncodeToString(signature.Sum(nil))
}
Where am I screwing up?
Have you checked out the go-coinbase github repo implementing this as:
https://github.com/preichenberger/go-coinbasepro/blob/master/client.go
h := make(map[string]string)
h["CB-ACCESS-KEY"] = c.Key
h["CB-ACCESS-PASSPHRASE"] = c.Passphrase
h["CB-ACCESS-TIMESTAMP"] = timestamp
message := fmt.Sprintf(
"%s%s%s%s",
timestamp,
method,
url,
data,
)
sig, err := generateSig(message, c.Secret)
if err != nil {
return nil, err
}
h["CB-ACCESS-SIGN"] = sig
return h, nil
It turns out using req.Body directly is the culprit. Why I don't know and something I need to find out, but reading into a []byte and then casting to a string solves part of it.

invalid argument: no armored data found

When I try to load an armored GPG public key to verify a signature, I get the error openpgp: invalid argument: no armored data found
My code (some data shortened to fit better):
pubKey := `-----BEGIN PGP PUBLIC KEY BLOCK-----
xsFNBF/9Xn [...] =Yo8+
-----END PGP PUBLIC KEY BLOCK-----`
content := "Hello World"
signature := `-----BEGIN PGP SIGNATURE-----
wsFcBAE [...] =z3nL
-----END PGP SIGNATURE-----`
keyring, err := openpgp.ReadArmoredKeyRing(strings.NewReader(pubKey))
if err != nil {
// Errors out here with: openpgp: invalid argument: no armored data found
// ...
}
// Code never gets this far but I'm including this in case I'm using it all wrong...
_, err = openpgp.CheckArmoredDetachedSignature(keyring, strings.NewReader(content), strings.NewReader(signature))
if err != nil {
return false, err
}
Entire public key, entire signature.
edit: i think its something to do with your public key armor not being valid. below is a link to a working function with an example const e2ePublicKey public key.
instead of using strings.NewReader(pubKey), they use:
keyring, err := openpgp.ReadArmoredKeyRing(bytes.NewBufferString(pubKey))
maybe another bytes.NewBufferString for the signature.
(from src)

How to sign JWT with ECDSA method using jwt golang package - Sign in with Apple

When integrating Sign in with Apple you generate a key in your apple developer account.
It's a file that is named like AuthKey_3JMD5K6.p8 and looks like
-----BEGIN PRIVATE KEY-----
MasdfjalskdasdflaASDFAadsflkjaADSFAewfljasdfljkasefasdflkjasdf
asdfljkasdfASDFASDFoiqretasdoiyjlfsbgREtaREGSDFBREtafsrgAREGfdsgaregR
LKJIOEWFNLasdflkawefjoiasdflk
-----END PRIVATE KEY-----
so I made a var appleKey := MasdfjalskdasdflaASDFAadsflkjaADSFAewfljasdfljkasefasdflkjasdf asdfljkasdfASDFASDFoiqretasdoiyjlfsbgREtaREGSDFBREtafsrgAREGfdsgaregRLKJIOEWFNLasdflkawefjoiasdflk
I've signed jwt with the HMAC-SHA method before which is fairly straightforward but I don't know how to sign a jwt with the ECDSA method.
I wrote my code the same way I did for the HMAC-SHA method but get an error key is of invalid type
So using the the jwt library for golang how can I sign my jwt with ECDSA method?
My code
// generate client secret jwt using apple key
expirationTime := time.Now().Add(5 * time.Minute)
claims := &Claims{
StandardClaims: jwt.StandardClaims {
Audience: "https://appleid.apple.com",
Subject: "com.app.ios",
Issuer: string(appleTeamId),
ExpiresAt: expirationTime.Unix(),
IssuedAt: time.Now().Unix(),
},
}
appleToken := jwt.NewWithClaims(jwt.SigningMethodES256, claims)
appleToken.Header["kid"] = appleKid
signedAppleToken, err := appleToken.SignedString(appleKey)
I now know this isn't how you do it and it's a little bit more complex than that but what is the way to do it?
I found this article that tells you how to manually do it:
http://p.agnihotry.com/post/validating_sign_in_with_apple_authorization_code/
But I'm already using the jwt library for golang for the other part of the token:
https://godoc.org/github.com/dgrijalva/jwt-go
In the github.com/dgrijalva/jwt-go's SigningMethodECDSA.Sign docs you can find:
[...] For this signing method, key must be an ecdsa.PrivateKey struct
So, to put together an example:
p8bytes, err := ioutil.ReadFile("SomeAppleKey.p8")
if err != nil {
log.Println(err)
return
}
// Here you need to decode the Apple private key, which is in pem format
block, _ := pem.Decode(p8bytes)
// Check if it's a private key
if block == nil || block.Type != "PRIVATE KEY" {
log.Println("Failed to decode PEM block containing private key")
return
}
// Get the encoded bytes
x509Encoded := block.Bytes
token := jwt.NewWithClaims(
jwt.SigningMethodES256, // specific instance of `*SigningMethodECDSA`
jwt.StandardClaims{
// ...
},
)
// Now you need an instance of *ecdsa.PrivateKey
parsedKey, err := x509.ParsePKCS8PrivateKey(x509Encoded) // EDIT to x509Encoded from p8bytes
if err != nil {
panic(err)
}
ecdsaPrivateKey, ok := parsedKey.(*ecdsa.PrivateKey)
if !ok {
panic("not ecdsa private key")
}
// Finally sign the token with the value of type *ecdsa.PrivateKey
signed, err := token.SignedString(ecdsaPrivateKey)
if err != nil {
panic(err)
}
fmt.Println(signed) // the signed JWT
Note: as shown in the code snippet, because the key file from Apple is in PEM format, it needs to be decoded first
Warning!
Please be aware that github.com/dgrijalva/jwt-go has been unmaintained for a long time and has critical unfixed bugs. And doesn't support Go modules, before the version 4 (which is just a preview anyway). I strongly recommend to choose an different library for dealing with JWT.
Update June 2021
There is now an official community fork of the library: golang-jwt/jwt blessed by the owner of the original project.

Encrypt client-private-key with RSA-2048 server-public-key

I need to encrypt client-private-key with RSA-2048 server-public-key.
I know that private key is obviously longer than the public key and I'm not sure if it's possible... but I saw a similar task was done in Python, so I want to know your opinion.
/* main */
clientPrivateKey, _ := generateRsaPair(2048)
_, serverPublicKey := generateRsaPair(2048)
clientPrivateKeyAsByte := privateKeyToBytes(clientPrivateKey)
encryptWithPublicKey(clientPrivateKeyAsByte, serverPublicKey)
Fatal error crypto/rsa: message too long for RSA public key size
/* Functions */
func generateRsaPair(bits int) (*rsa.PrivateKey, *rsa.PublicKey) {
privkey, err := rsa.GenerateKey(rand.Reader, bits)
if err != nil {
log.Error(err)
}
return privkey, &privkey.PublicKey
}
func encryptWithPublicKey(msg []byte, pub *rsa.PublicKey) []byte {
hash := sha512.New()
ciphertext, err := rsa.EncryptOAEP(hash, rand.Reader, pub, msg, nil)
checkError(err)
return ciphertext
}
func privateKeyToBytes(priv *rsa.PrivateKey) []byte {
privBytes := pem.EncodeToMemory(
&pem.Block{
Type: "RSA PRIVATE KEY",
Bytes: x509.MarshalPKCS1PrivateKey(priv),
},
)
return privBytes
}
If you want to encrypt something larger than the key size then you can simply use hybrid encryption. You first encrypt (or wrap, if a specific wrapping operation is available) the encoding of the private key using a random AES key, e.g. using AES-CBC or AES-CTR (with an all zero IV). Then you encrypt that AES key using the private key. The ciphertext consists of the encrypted AES key followed by the encrypted data - in this case an RSA private key.
Note however that a private key should really be managed by one entity. It is not called a private key for nothing. Distributing private keys is generally considered bad key management practice.

Golang package jwt-go with rsa key. How to put the public key and how to get it from the token?

I'm trying to generate a token with a rsa key using the jwt-go package in golang.
Here there is a blog explaining how to do it but that code will always be validating all tokens because is using the public key stored in the server and is not obtaining it from the token. How do you put the complete public key in the token? I was trying this:
var secretKey, _ = rsa.GenerateKey(rand.Reader, 1024)
token := jwt.New(jwt.SigningMethodRS256)
token.Claims["username"] = "victorsamuelmd"
token.Claims["N"] = secretKey.PublicKey.N
token.Claims["E"] = secretKey.PublicKey.E
tokenString, err := token.SignedString(secretKey)
nt, err := jwt.Parse(tokenString, func(t *jwt.Token) (interface{}, error) {
// here I need to recover the public key from the token
// but N is a big.Int and the token stores N as int64
})
Sorry about my english. Thanks.
I think storing the public key in the claims is not good idea because we can verify the JWT with that key technically, but it means it is not a signed JWT anymore. If anyone can generate the JWT with their own private key and storing the public key in JWT, we cannot sure who is signer.
Anyway, you can convert the public key into PEM format which is just a string, and store it in claims. In client side, you can also simply parse it again into public key format. The sample code is below:
privateKey, _ := rsa.GenerateKey(rand.Reader, 1024)
bytes, _ := x509.MarshalPKIXPublicKey(&privateKey.PublicKey)
pem := pem.EncodeToMemory(&pem.Block{
Type: "RSA PUBLIC KEY",
Bytes: bytes,
})
claim["publickey"] = string(pem)
and
pem := []byte(claims["publickey"].(string))
return jwt.ParseRSAPublicKeyFromPEM(pem)
jwt is dgrijalva's jwt-go.

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