protected override void Action()
{
base.Action();
String guid = Request[PtaServerConstants.OURGUID_KEY];
bboardDR = PtaUtil.GetBBoardDataReaderByGuid(guid);
RequestValidator rv = new RequestValidator(bboardDR);
rv.Validate(Request);
}
/// <summary>
/// Standard entry point of IHttpHandler, main processing flow.
/// </summary>
public void ProcessRequest(HttpContext context)
{
log4net.ILog log = PtaUtil.getLog4netLogger(this.GetType().FullName + ".ProcessRequest(): ");
try {
this.context = context;
String guid = context.Request.Form["ourguid"];
bboardDR = PtaUtil.GetBBoardDataReaderByGuid(guid);
onErrorServerTransfer = PtaUtil.GetDBReaderStringField(bboardDR, "OnErrorServerTransfer");
RequestValidator rv = new RequestValidator(bboardDR);
rv.Validate(context.Request);
Redirect();
} catch (System.Threading.ThreadAbortException) {
//this is normal processing of Server.Transfer() and Response.End()
throw;
} catch (Exception e) {
PtaUtil.LogExceptionAndFormParameters(log, e);
//String on_err_st = onErrorServerTransfer;
//if (on_err_st == null) on_err_st = PtaUtil.GetProxyWebFolder() + "ErrorPages/PtaDefaultErrPage.aspx";
//context.Server.Transfer(on_err_st, true);
String back_link = context.Request.Form["tcbaseurl"] + context.Request.Form["returnurl"];
String err_page = PtaUtil.GenerateSimpleErrorPage(back_link);
context.Response.Write(err_page);
log.Debug("onErrorServerTransfer: " + onErrorServerTransfer);
if (onErrorServerTransfer != null)
{
context.Server.Transfer(onErrorServerTransfer, true);
}
/* else {
* back_link = context.Request.Form["tcbaseurl"] + context.Request.Form["returnurl"];
* context.Response.Write("Your request could not be processed. <br/>");
* context.Response.Write("Back to Blackboard: " + "<a href=\"" + back_link + "\">" + back_link + "</a><br/>");
* }*/
//throw;
} finally {
PtaUtil.CloseDataReader(drParam);
PtaUtil.CloseDataReader(drMenuLink);
PtaUtil.CloseDataReader(bboardDR);
}
}
/// <summary>
/// Performs series of actions necessary for validation of passed by Blackboard parameters.
/// See http://www.edugarage.com/display/BBDN/Proxy+Tool+SSO , internal method comments and java client sample code for details.
/// Performs periodical cleanup of collected nonces upon every NonceCleanupCount invocation
/// </summary>
public void Validate(HttpRequest request)
{
log4net.ILog log = PtaUtil.getLog4netLogger(this.GetType().FullName + ".Validate(): ");
request.ContentEncoding = System.Text.Encoding.UTF8;
if (bboardDR == null)
{
bboardDR = PtaUtil.GetBBoardDataReaderByGuid(guid);
}
String s_secret = PtaUtil.GetDBReaderStringField(bboardDR, "SharedSecret");
//http://www.edugarage.com/display/BBDN/Proxy+Tool+SSO
// 1. Sort the posted data based on the key names and then concatenate all of the values together in the sorted order
String[] sorted_form_keys = request.Form.AllKeys;
Array.Sort(sorted_form_keys);
System.Text.StringBuilder data_string = new System.Text.StringBuilder("");
foreach (String form_key in sorted_form_keys)
{
/* from proxy\java\src\com\blackboard\test\proxy\GenericParameters.java:
* // ignore extra parameters added after the mac was generated/set
* if ( key.startsWith( "top_" ) || key.startsWith( "bottom_" ) )
* {
* //ignore
* }
* */
if (form_key.StartsWith("top_", StringComparison.OrdinalIgnoreCase) ||
form_key.StartsWith("bottom_", StringComparison.OrdinalIgnoreCase)
//MAC cannot be calculated over itself
|| form_key.Equals("mac", StringComparison.OrdinalIgnoreCase))
{
continue;
}
data_string.Append(request.Form[form_key]);
}
log.Debug("data_string: " + data_string);
// 2. append the shared secret
data_string.Append(s_secret);
// 3. Turn this string into a string of utf-8 bytes
byte[] data_buffer = System.Text.Encoding.UTF8.GetBytes(data_string.ToString());
// 4. Create a message digest from these bytes
System.Security.Cryptography.MD5 md = new System.Security.Cryptography.MD5CryptoServiceProvider();
byte[] md5_hash = md.ComputeHash(data_buffer);
// 5. Convert the resulting byte array into a base64 encoded string
String md5_hash_64 = System.Convert.ToBase64String(md5_hash);
log.Debug("md5_hash_64: " + md5_hash_64);
//relace operations below are copied from proxy\java\src\com\blackboard\test\proxy\ProxyUtil.java generateMac()
md5_hash_64.Replace("\r", "");
md5_hash_64.Replace("\n", "");
log.Debug("md5_hash_64: " + md5_hash_64);
String bb_mac = request.Form[PtaServerConstants.MAC_KEY];
log.Debug("bb_mac: " + bb_mac);
//compare received and calculated MACs
if (!bb_mac.Equals(md5_hash_64))
{
throw new PtaException("MAC mismatch. md5_hash_64: " + md5_hash_64 + "; bb_mac: " + bb_mac);
}
//check that timestamp is expected timeframe
String bb_ts = request.Form[PtaServerConstants.TIMESTAMP_KEY];
long bb_millis = Int64.Parse(bb_ts);
log.Debug("bb_millis: " + bb_millis);
long mac_life_ms = Int64.Parse(WebConfigurationManager.AppSettings["MacLifetimeInMinutes"]);
log.Debug("mac_life_ms: " + mac_life_ms);
long mac_life_millis = mac_life_ms * 1000 * 60;
//http://bytes.com/topic/c-sharp/answers/557734-java-system-currenttimemillis-equivalent
//- about java System.currentTimeMillis() in .net
DateTime utc_now = DateTime.UtcNow;
log.Debug("utc_now: " + utc_now);
DateTime base_time = new DateTime(1970, 1, 1, 0, 0, 0);
log.Debug("base_time: " + base_time);
long proxy_millis = (utc_now - base_time).Ticks / 10000;
log.Debug("proxy_millis: " + proxy_millis);
if (Math.Abs(proxy_millis - bb_millis) > mac_life_millis) //added abs() - not to be much earlier too. Assuming that earlier timestamp may be possible due to non-synchronized system time on BB and proxy server
{
throw new PtaException("Timestamp is out of max request delay. proxy_millis(secs): " + proxy_millis + "(" + proxy_millis / 1000 + "); bb_millis(secs): " + bb_millis + "(" + bb_millis / 1000 + "); mac_life_ms(secs): " + mac_life_millis + "(" + mac_life_millis / 1000 + ")");
}
String nonce = request.Form[PtaServerConstants.NONCE_KEY];
if (nonce == null)
{
throw new PtaException("Invalid null Nonce");
}
if (RequestValidator.knownNonces.Contains(nonce))
{
throw new PtaException("Invalid duplicated Nonce. nonce: " + nonce);
}
int nonce_cleanup_count = Int16.Parse(WebConfigurationManager.AppSettings["NonceCleanupCount"]);
lock (typeof(RequestValidator)) {
knownNonces.Add(nonce, proxy_millis);
nonceCleanupCounter++;
if (nonceCleanupCounter > nonce_cleanup_count)
{
//!! test/debug
Hashtable non_expired_nonces = new Hashtable();
foreach (DictionaryEntry nonce_de in RequestValidator.knownNonces)
{
long nonce_millis = (long)nonce_de.Value;
if (nonce_millis >= proxy_millis - mac_life_millis)
{
non_expired_nonces.Add(nonce_de.Key, nonce_millis);
}
}
knownNonces = non_expired_nonces;
nonceCleanupCounter = 0;
}
}
}
