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using System;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;
using IdentityModel;
using Microsoft.IdentityModel.Protocols.OpenIdConnect;
using Microsoft.Owin;
using Microsoft.Owin.Security;
using Microsoft.Owin.Security.Cookies;
using Microsoft.Owin.Security.Notifications;
using Microsoft.Owin.Security.OpenIdConnect;
using Owin;
[assembly: OwinStartup(typeof(ScottBrady91.BlogExampleCode.AspNetPkce.Startup))]
namespace ScottBrady91.BlogExampleCode.AspNetPkce
{
public class Startup
{
public void Configuration(IAppBuilder app)
{
app.UseCookieAuthentication(new CookieAuthenticationOptions
{
AuthenticationType = "cookie"
});
app.UseOpenIdConnectAuthentication(new OpenIdConnectAuthenticationOptions
{
ClientId = "mvc.owin",
Authority = "http://localhost:5000",
RedirectUri = "http://localhost:5001/",
Scope = "openid profile api1",
SignInAsAuthenticationType = "cookie",
RequireHttpsMetadata = false,
UseTokenLifetime = false,
RedeemCode = true,
SaveTokens = true,
ClientSecret = "secret",
ResponseType = "code",
ResponseMode = "query",
Notifications = new OpenIdConnectAuthenticationNotifications
{
RedirectToIdentityProvider = n =>
{
if (n.ProtocolMessage.RequestType == OpenIdConnectRequestType.Authentication)
{
// set PKCE parameters
var codeVerifier = CryptoRandom.CreateUniqueId(32);
string codeChallenge;
using (var sha256 = SHA256.Create())
{
var challengeBytes = sha256.ComputeHash(Encoding.UTF8.GetBytes(codeVerifier));
codeChallenge = Base64Url.Encode(challengeBytes);
}
n.ProtocolMessage.SetParameter("code_challenge", codeChallenge);
n.ProtocolMessage.SetParameter("code_challenge_method", "S256");
// remember code_verifier (adapted from OWIN nonce cookie)
RememberCodeVerifier(n, codeVerifier);
}
return Task.CompletedTask;
},
AuthorizationCodeReceived = n =>
{
// get code_verifier
var codeVerifier = RetrieveCodeVerifier(n);
// attach code_verifier
n.TokenEndpointRequest.SetParameter("code_verifier", codeVerifier);
return Task.CompletedTask;
}
}
});
}
private void RememberCodeVerifier(RedirectToIdentityProviderNotification<OpenIdConnectMessage, OpenIdConnectAuthenticationOptions> n, string codeVerifier)
{
var properties = new AuthenticationProperties();
properties.Dictionary.Add("cv", codeVerifier);
n.Options.CookieManager.AppendResponseCookie(
n.OwinContext,
GetCodeVerifierKey(n.ProtocolMessage.State),
Convert.ToBase64String(Encoding.UTF8.GetBytes(n.Options.StateDataFormat.Protect(properties))),
new CookieOptions
{
SameSite = SameSiteMode.None,
HttpOnly = true,
Secure = n.Request.IsSecure,
Expires = DateTime.UtcNow + n.Options.ProtocolValidator.NonceLifetime
});
}
private string RetrieveCodeVerifier(AuthorizationCodeReceivedNotification n)
{
string key = GetCodeVerifierKey(n.ProtocolMessage.State);
string codeVerifierCookie = n.Options.CookieManager.GetRequestCookie(n.OwinContext, key);
if (codeVerifierCookie != null)
{
var cookieOptions = new CookieOptions
{
SameSite = SameSiteMode.None,
HttpOnly = true,
Secure = n.Request.IsSecure
};
n.Options.CookieManager.DeleteCookie(n.OwinContext, "cv", cookieOptions);
}
var cookieProperties = n.Options.StateDataFormat.Unprotect(Encoding.UTF8.GetString(Convert.FromBase64String(codeVerifierCookie)));
cookieProperties.Dictionary.TryGetValue("cv", out var codeVerifier);
return codeVerifier;
}
private string GetCodeVerifierKey(string state)
{
using (var hash = SHA256.Create())
{
return OpenIdConnectAuthenticationDefaults.CookiePrefix + "cv." + Convert.ToBase64String(hash.ComputeHash(Encoding.UTF8.GetBytes(state)));
}
}
}
}
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