How can I change the 'typ' of a token provided by Azure AD? - authentication

Question

I have a project setup like this:
React frontend
-> authenticates against...
Identity Server
-> which redirects to...
A Microsoft login
I'm using a Clients Credential Provider and it works great - the IS4 redirects to MS login, and then gets redirected with the access token back, which is then passed on to the React app.
Now, I've been tasked with creating a feature to change the user's password. I'm trying to do this by sending the old+new password to IS4, and then calling the MSGraphClient, but I couldn't make it work.
I've tried the Username/Password provider, because I have all the info needed, but I need to change stuff on the ActiveDirectory settings to make my app public. But even then, I don't like that solution.
I've also tried with the On-behalf-of provider, this is the code:
var scopes = new[] { "User.Read",
"Directory.AccessAsUser.All" };
// Multi-tenant apps can use "common",
// single-tenant apps must use the tenant ID from the Azure portal
var tenantId = "~~";
// Value from app registration
var clientId = "~~";
var clientSecret = "~~";
var options = new TokenCredentialOptions
{
AuthorityHost = AzureAuthorityHosts.AzurePublicCloud
};
// This is the incoming token to exchange using on-behalf-of flow
var oboToken = HttpContext.Request.Headers.First(h => h.Key == "Authorization").Value.ToString().Replace("Bearer ", "");
var cca = ConfidentialClientApplicationBuilder
.Create(clientId)
.WithTenantId(tenantId)
.WithClientSecret(clientSecret)
.Build();
// DelegateAuthenticationProvider is a simple auth provider implementation
// that allows you to define an async function to retrieve a token
// Alternatively, you can create a class that implements IAuthenticationProvider
// for more complex scenarios
var authProvider = new DelegateAuthenticationProvider(async (request) => {
// Use Microsoft.Identity.Client to retrieve token
var assertion = new UserAssertion(oboToken);
var result = await cca.AcquireTokenOnBehalfOf(scopes, assertion).ExecuteAsync();
request.Headers.Authorization =
new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", result.AccessToken);
});
var graphClient = new GraphServiceClient(authProvider);
And it kinds of work, because the request is made, but the server throws an error:
AADSTS5002727: Invalid JWT header type specified. Allowed types: 'JWT','http://openid.net/specs/jwt/1.0'.
I checked my token on JWT.io, and the typ is at+jwt... Why? Why is MS sending me a type of token that it doesn't support? How can I change it from my side so it's a plain JWT?
Thanks for any advice, and any other possible solution for this.

Answer 1

To resolve the error "AADSTS5002727: Invalid JWT header type specified. Allowed types: JWT,http ://openid.net/specs/jwt/1.0" , please try the below if helpful:
Please check the version of .Net core you are currently using to generate the token. Try using .Net core 2.2 with IS4.
Try setting IdentityServerOptions.AccessTokenJwtType to empty string or JWT on IdentityServerOptions.
In the mentioned code, replace var oboToken variable directly with the value of token.
var oboToken = "JWT_TOKEN_TO_EXCHANGE";
Please note the below point from MsDoc :
Don't attempt to validate or read tokens for any API you don't own,
including the tokens in this example, in your code. Tokens for Microsoft services can use a special format that will not validate as
a JWT, and may also be encrypted for consumer (Microsoft account)
users
If still the error persists, try upgrading clients to a new token validation library that works with the new style tokens.
Please check whether the below links give you any pointer to resolve the issue:
JWT Token always Invalid · Issue #905 · openiddict/openiddict-core · GitHub
IdentityServer .Net Core 3.0 & Owin/Katana Token validation · Issue #3705 · IdentityServer/IdentityServer4 · GitHub