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Handle RS512 situations when the modulus isn't base64 encoded. #29

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merged 1 commit into from
Jan 22, 2024
Merged

Handle RS512 situations when the modulus isn't base64 encoded. #29

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30 changes: 14 additions & 16 deletions src/Authress.SDK/Client/TokenVerifier.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -175,6 +175,16 @@ public async Task<VerifiedUserIdentity> VerifyToken(string jwtToken) {
return verifiedUserIdentity;
}

private byte[] ConvertFromBase64Url(string base64String) {
var result = base64String.Replace('_', '/').Replace('-', '+');
switch(result.Length % 4) {
case 2: result += "=="; break;
case 3: result += "="; break;
}

return Convert.FromBase64String(result);
}

private VerifiedUserIdentity VerifySignature(string jwtToken, Jwk key) {

var unverifiedJwtPayload = JsonConvert.DeserializeObject<Client.JWT.JwtPayload>(Base64UrlEncoder.Decode(jwtToken.Split('.')[1]));
Expand All @@ -184,20 +194,8 @@ private VerifiedUserIdentity VerifySignature(string jwtToken, Jwk key) {

var data = Encoding.UTF8.GetBytes($"{jwtToken.Split('.')[0]}.{jwtToken.Split('.')[1]}");

var keyAsString = key.x.Replace('_', '/').Replace('-', '+');
switch(keyAsString.Length % 4) {
case 2: keyAsString += "=="; break;
case 3: keyAsString += "="; break;
}

var jwtTokenSignature = jwtToken.Split('.')[2].Replace('_', '/').Replace('-', '+');
switch(jwtTokenSignature.Length % 4) {
case 2: jwtTokenSignature += "=="; break;
case 3: jwtTokenSignature += "="; break;
}

var edDsaPublicKey = NSec.Cryptography.PublicKey.Import(ed25519alg, Convert.FromBase64String("MCowBQYDK2VwAyEA" + keyAsString), KeyBlobFormat.PkixPublicKey);
var signatureData = Convert.FromBase64String(jwtTokenSignature);
var edDsaPublicKey = NSec.Cryptography.PublicKey.Import(ed25519alg, ConvertFromBase64Url("MCowBQYDK2VwAyEA" + key.x), KeyBlobFormat.PkixPublicKey);
var signatureData = ConvertFromBase64Url(jwtToken.Split('.')[2]);
if (!SignatureAlgorithm.Ed25519.Verify(edDsaPublicKey, data, signatureData)) {
throw new TokenVerificationException($"Unauthorized: Token Signature is not valid.");
}
Expand All @@ -211,8 +209,8 @@ private VerifiedUserIdentity VerifySignature(string jwtToken, Jwk key) {
var rsa = new RSACryptoServiceProvider();
rsa.ImportParameters(new RSAParameters()
{
Modulus = Convert.FromBase64String(key.n),
Exponent = Convert.FromBase64String(key.e)
Modulus = ConvertFromBase64Url(key.n),
Exponent = ConvertFromBase64Url(key.e)
});

var tokenHandler = new JwtSecurityTokenHandler();
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