public void VerifyToken(DotvvmRequestContext context, string token)
{
if (context == null) throw new ArgumentNullException("context");
if (string.IsNullOrWhiteSpace(token)) throw new SecurityException("CSRF protection token is missing.");
// Get application key helper
var keyHelper = new ApplicationKeyHelper(context.Configuration.Security);
// Get token
var userIdentity = ProtectionHelpers.GetUserIdentity(context);
var requestIdentity = ProtectionHelpers.GetRequestIdentity(context);
byte[] tokenSid;
try
{
var tokenData = Convert.FromBase64String(token);
tokenSid = keyHelper.UnprotectData(tokenData, KDF_LABEL_TOKEN, userIdentity, requestIdentity);
}
catch (Exception ex)
{
// Incorrect Base64 formatting of crypto protection error
throw new SecurityException("CSRF protection token is invalid.", ex);
}
// Get SID from cookie and compare with token one
var cookieSid = this.GetOrCreateSessionId(context);
if (!cookieSid.SequenceEqual(tokenSid)) throw new SecurityException("CSRF protection token is invalid.");
}
private byte[] GetOrCreateSessionId(DotvvmRequestContext context)
{
if (context == null) throw new ArgumentNullException("context");
if (string.IsNullOrWhiteSpace(context.Configuration.Security.SessionIdCookieName)) throw new FormatException("Configured SessionIdCookieName is missing or empty.");
// Get cookie manager
var mgr = new ChunkingCookieManager(); // TODO: Make this configurable
// Get application key helper
var keyHelper = new ApplicationKeyHelper(context.Configuration.Security);
// Get cookie value
var sidCookieValue = mgr.GetRequestCookie(context.OwinContext, context.Configuration.Security.SessionIdCookieName);
if (string.IsNullOrWhiteSpace(sidCookieValue))
{
// No SID - generate and protect new one
var rng = new System.Security.Cryptography.RNGCryptoServiceProvider();
var sid = new byte[SID_LENGTH];
rng.GetBytes(sid);
var protectedSid = keyHelper.ProtectData(sid, KDF_LABEL_SID);
// Save to cookie
sidCookieValue = Convert.ToBase64String(protectedSid);
mgr.AppendResponseCookie(
context.OwinContext,
context.Configuration.Security.SessionIdCookieName, // Configured cookie name
sidCookieValue, // Base64-encoded SID value
new Microsoft.Owin.CookieOptions
{
HttpOnly = true, // Don't allow client script access
Secure = context.OwinContext.Request.IsSecure // If request goes trough HTTPS, mark as secure only
});
// Return newly generated SID
return sid;
}
else
{
// Try to read from cookie
try
{
var protectedSid = Convert.FromBase64String(sidCookieValue);
var sid = keyHelper.UnprotectData(protectedSid, KDF_LABEL_SID);
return sid;
}
catch (Exception ex)
{
// Incorrect Base64 formatting of crypto protection error
throw new SecurityException("Value of the SessionID cookie is corrupted or has been tampered with.", ex);
}
}
}
private const string KDF_LABEL_TOKEN = "DotVVM.Framework.Security.DefaultCsrfProtector.Token"; // Key derivation label for protecting token
public string GenerateToken(DotvvmRequestContext context)
{
if (context == null) throw new ArgumentNullException("context");
// Get SID
var sid = this.GetOrCreateSessionId(context);
// Get application key helper
var keyHelper = new ApplicationKeyHelper(context.Configuration.Security);
// Get token
var userIdentity = ProtectionHelpers.GetUserIdentity(context);
var requestIdentity = ProtectionHelpers.GetRequestIdentity(context);
var tokenData = keyHelper.ProtectData(sid, KDF_LABEL_TOKEN, userIdentity, requestIdentity);
// Return encoded token
return Convert.ToBase64String(tokenData);
}