JEDI Windows API

The Delphi JEDI Project needs your help

Remko — Sun, 20 Apr 2008 20:16:40 +0000

The JEDI API Library project (JWA) has been successfully revived from a sleep status to an active project with lots of ambitions. Some recent achievements are the new include model of JWA, the release of JWSCL (the Security Library) and of course the “birth” of this blog.

We made a roadmap for JWA and JWSCL which includes “unicodifying” (Nick Hodges gave birth to a new word, meaning making the code ready for the next Delphi) and converting new Vista/Server 2008 API’s.

To help us fullfill these ambitions and continue contributing to the Delphi Community, we are looking for experienced Delphi developers to help us with the following tasks:

Maintaining and extending the Jedi API Library (convert new header files, fix errors in existing code).
Maintaining and extending the Jedi Windows Security Code Library (use and test the library, contribute new code, maintain documentation, Active Directory).
Create examples and write blog posts about using JWA and/or JWSCL.

We support YOU developing with JWA and JWSCL!

Christian Wimmer — Thu, 03 Apr 2008 18:42:59 +0000

Do you need help? We can support you creating application using JWA and/or JWSCL.

Visit the Get Service site on SourceForge for more information like pricing.

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COM Server tells you sth about opened client connections

Christian Wimmer — Tue, 01 Jul 2008 13:59:58 +0000

If you create a COM Server to serve some clients with COM interfaces (or better their functionality), you maybe get sometimes a dialog box that tells you that there are client connections opened. This happens as soon as you try to close your app. If you want to close it though, you have to explicitly click “Yes”.

You can prevent this dialog box by setting the property UIInteractive of TComServer to true. The COM Server instance is defined in unit ComServ by the instance variable ComServer. It also sets ObjectCount which defines the remaining client COM connections. The dialog pops up if this value is greater than zero. In this way you can easily check yourself the whole circumstance and show a dialog yourself if you need it.

uses ComServ,…;
…
ComServer.UIInteractive := false;

Consider what happens if a dialog box appears in your service app. I did some tests in Windows Vista and found out that the dialog box prevented the service process to be terminated although the service shuts down correctly. So I just set UIInteractive to false and it worked fine.

Remember: If a service must be shut down it should do it as fast as possible.

uses ComServ,…;
…
ComServer.UIInteractive := false;

Remember: If a service must be shut down it should do it as fast as possible.

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So you want to write a service…

Christian Wimmer — Sat, 21 Jun 2008 22:55:05 +0000

If you are going to write a service you should consider why you need it to be a service at all. If you can run your application as a standard user, you should do it. A service is a high privileged application that should be created with care and clear thoughts.
So think about your task you want to solve with the application.

Do you need special privileges (e.g. TCB) that only a SYSTEM user can give?
Do you have to keep secrets in a real safe area?
Do you want to support multiple logged on users?
Can the user profit from your service?
Has the application to be active and available all the time?

You should say at least Yes twice to have a real reason.

Okay, but you want to get into that domain first. So what should you think of:

A service is like a thread that has an execute method and if this method is exits, the service exits. There is no loop by default!
A service cannot communicate with the user through a GUI. In preVista Windows versions, this “feature” was only a coincidence which frankly was used quite often (in fact everybody used it). It does not work for Remote desktop Logins or FastUserSwitch.
Use any log mechanism to give status report. Delphi offers the Windows event report mechanism by the method LogMessage.
Use the method ProcessRequests if you go into a loop. This method lets the service respond to the requests of the Windows service control manager. If you just call Sleep your service will be unresponsible.
The MessageBox API can show a message box on the current user’s desktop. To make it work add the flag MB_SERVICE_NOTIFICATION to the last parameter. You should also add MB_DEFAULT_DESKTOP_ONLY , so the messagebox only appears on the user’s desktop and not on the winlogon or any other desktop. Be aware that in this way you can only show one message at a time. The next message won’t appear until the first message has been clicked away.In my opinion this API is only good for debugging purposes. Think of a computer which does not have a logged on user. No administrator will every see your message.
You cannot debug a service like any other application by default. Luckily there is remedy. The JEDI API offers a RunAsSys application that lets you start your Delphi in the SYSTEM context. In this way you just have to do a minor patch to your service source code to make it run like any other application in Delphi. See my post Debugging services: an easy way.

There can be thousands of other good advices you should consider. However I didn’t want to scare you away. Just be aware of the upcoming (possible) problems and try to learn, learn and learn and ….

If you want to give another good advice, post it here.

. If you can run your application as a standard user, you should do it. A service is a high privileged application that should be created with care and clear thoughts.
So think about your task you want to solve with the application.

Do you need special privileges (e.g. TCB) that only a SYSTEM user can give?
Do you have to keep secrets in a real safe area?
Do you want to support multiple logged on users?
Can the user profit from your service?
Has the application to be active and available all the time?

You should say at least Yes twice to have a real reason.

Okay, but you want to get into that domain first. So what should you think of:

A service is like a thread that has an execute method and if this method is exits, the service exits. There is no loop by default!
A service cannot communicate with the user through a GUI. In preVista Windows versions, this “feature” was only a coincidence which frankly was used quite often (in fact everybody used it). It does not work for Remote desktop Logins or FastUserSwitch.
Use any log mechanism to give status report. Delphi offers the Windows event report mechanism by the method LogMessage.
Use the method ProcessRequests if you go into a loop. This method lets the service respond to the requests of the Windows service control manager. If you just call Sleep your service will be unresponsible.
The MessageBox API can show a message box on the current user’s desktop. To make it work add the flag MB_SERVICE_NOTIFICATION to the last parameter. You should also add MB_DEFAULT_DESKTOP_ONLY , so the messagebox only appears on the user’s desktop and not on the winlogon or any other desktop. Be aware that in this way you can only show one message at a time. The next message won’t appear until the first message has been clicked away.In my opinion this API is only good for debugging purposes. Think of a computer which does not have a logged on user. No administrator will every see your message.
You cannot debug a service like any other application by default. Luckily there is remedy. The JEDI API offers a RunAsSys application that lets you start your Delphi in the SYSTEM context. In this way you just have to do a minor patch to your service source code to make it run like any other application in Delphi. See my post Debugging services: an easy way.

If you want to give another good advice, post it here.

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Technical note

Apollonius — Sat, 21 Jun 2008 15:14:07 +0000

After making some changes to the A-records of the DNS servers responsible for *.delphi-jedi.net, a different host was queried by the clients (e.g. your browsers) for the contents of this blog. Obviously the other host didn’t know how to react and thus gave back a simple “no idea what file that is” (i.e. HTTP error 404) in most cases. The issue has been resolved, but it may take some more time for some people until the DNS changes propagate to their DNS servers.

Mail traffic (the MX-record) was not influenced by this at any time. Jabber communication, however, may have been affected by it.

// Oliver

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Don’t misspell your target desktop…

Christian Wimmer — Wed, 18 Jun 2008 22:58:26 +0000

If you want to use CreateProcess or CreateProcessAsUser and you also want to set the target desktop, you should make sure that the target winstation (usual winsta0) and desktop name (usual default) is spelled correctly.
If you misspell the name (say defaut instead of default - missing l ) the process creation may succeed but your application won’t show but start running.

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Calculating Binary Hashes using TJwFileStreamEx

NeutralGeneral — Tue, 17 Jun 2008 08:50:37 +0000

Calculating Binary Hashes using TJwFileStreamEx

Why should I use TJwFileStreamEx instead of any other common stream class from the VCL?

Well this question is quite easily answered.

The first thing is that TJwFileStreamEx is based on Memory Mapped Files (MMF). MMF might be the fastest way to access files on your hard disk. Another good reason for using TJwFileStreamEx is its Memory property which is well known from the VCL TMemoryStream class. This property will reduce the effort remarkably.

Getting Started

First you have to include following units to your project:

uses JwsclTypes, JwsclStreams, JwsclCryptProvider;

The signature of our hashing-function looks like this:

function GetFileHash(Algorithm: TJwHashAlgorithm; const Filename: String) : String;

The first parameter is used to specify the Algorithm which is used to hash the file data. The second parameter defines the path to the file which hash you want to compute.

So what do we need to calculate the hash of a file? All we need is an instance of TJwFileStreamEx to open the file and an instance of TJwHash to calculate the hash:

function GetFileHash(Algorithm: TJwHashAlgorithm; const Filename: String) : String;
var
Stream: TJwFileStreamEx;
Hash: TJwHash;
begin
Stream := TJwFileStreamEx.Create(Filename,fmOpenRead);
try
Hash := TJwHash.Create(Algorithm);
// Calculate and return the Hash as a Hex-String
finally
Hash.Free;
Stream.Free;
end;
end;

This is the basic framework of our function. To calculate the hash of the file we need 2 methods:

TJwHash.HashData(Data: Pointer; Size: Cardinal);
TJwHash.RetrieveHash(out Len: Cardinal): Pointer;

HashData tells our instance of TJwHash which data is to be hashed and which size this data has. RetrieveHash calculates the Hash and retrieves a pointer to the hash data.

Finally we have to free the Buffer using the class method

TJwHash.FreeBuffer(Buffer: Pointer);

Now our function looks like this:

function GetFileHash(Algorithm: TJwHashAlgorithm; const Filename: String) : String;
var
Stream: TJwFileStreamEx;
Hash: TJwHash;
HashSize: Cardinal;
HashData: Pointer;
begin
Stream := TJwFileStreamEx.Create(Filename,fmOpenRead);
Hash := TJwHash.Create(Algorithm);
try
Hash.HashData(Stream.Memory,Stream.Size);
HashData := Hash.RetrieveHash(HashSize);
TJwHash.FreeBuffer(HashData);
finally
Hash.Free;
Stream.Free;
end;
end;

At last we need to convert the binary hash into a hex-string:

for i:= 1 to HashSize do
begin
Result := Result + IntToHex(PByte(HashData)^,2);
inc(PByte(HashData));
end;
dec(PByte(HashData),HashSize); //neccessary to free HashData

Now we’re done and finally our function looks like this:

function GetFileHash(Algorithm: TJwHashAlgorithm; const Filename: String) : String;
var
Stream: TJwFileStreamEx;
Hash: TJwHash;
HashSize: Cardinal;
HashData: Pointer;
i: Integer;
begin
Stream := TJwFileStreamEx.Create(Filename,fmOpenRead);
Hash := TJwHash.Create(Algorithm);
try
Hash.HashData(Stream.Memory,Stream.Size);
HashData := Hash.RetrieveHash(HashSize);
for i:= 1 to HashSize do
begin
Result := Result + IntToHex(PByte(HashData)^,2);
inc(PByte(HashData));
end;
dec(PByte(HashData),HashSize);
TJwHash.FreeBuffer(HashData);
finally
Hash.Free;
Stream.Free;
end;
end;

How do I use this function?

// first param can be one of these values:
// haMD2, haMD4, haMD5, haSHA
Label1.Caption := GetFileHash(haSHA,‘C:\Progam Files\Program\AFile.ext’);

OK, but what is the advantage of TJwFileStreamEx over other Streams?

Well, you don’t have to load the file into a TMemoryStream and thus the file will not be loaded completely into memory. Furthermore this solution is much faster than a solution using TMemoryStream and similar…

Download

Download the source and binaries of this example (260kiB). This includes the new and necessary JWSCL source files. However you need to download the whole package separately.

Calculating Binary Hashes using TJwFileStreamEx

Why should I use TJwFileStreamEx instead of any other common stream class from the VCL?

Well this question is quite easily answered.

Getting Started

First you have to include following units to your project:

uses JwsclTypes, JwsclStreams, JwsclCryptProvider;

The signature of our hashing-function looks like this:

function GetFileHash(Algorithm: TJwHashAlgorithm; const Filename: String) : String;

The first parameter is used to specify the Algorithm which is used to hash the file data. The second parameter defines the path to the file which hash you want to compute.

So what do we need to calculate the hash of a file? All we need is an instance of TJwFileStreamEx to open the file and an instance of TJwHash to calculate the hash:

function GetFileHash(Algorithm: TJwHashAlgorithm; const Filename: String) : String;
var
Stream: TJwFileStreamEx;
Hash: TJwHash;
begin
Stream := TJwFileStreamEx.Create(Filename,fmOpenRead);
try
Hash := TJwHash.Create(Algorithm);
// Calculate and return the Hash as a Hex-String
finally
Hash.Free;
Stream.Free;
end;
end;

This is the basic framework of our function. To calculate the hash of the file we need 2 methods:

TJwHash.HashData(Data: Pointer; Size: Cardinal);
TJwHash.RetrieveHash(out Len: Cardinal): Pointer;

HashData tells our instance of TJwHash which data is to be hashed and which size this data has. RetrieveHash calculates the Hash and retrieves a pointer to the hash data.

Finally we have to free the Buffer using the class method

TJwHash.FreeBuffer(Buffer: Pointer);

Now our function looks like this:

function GetFileHash(Algorithm: TJwHashAlgorithm; const Filename: String) : String;
var
Stream: TJwFileStreamEx;
Hash: TJwHash;
HashSize: Cardinal;
HashData: Pointer;
begin
Stream := TJwFileStreamEx.Create(Filename,fmOpenRead);
Hash := TJwHash.Create(Algorithm);
try
Hash.HashData(Stream.Memory,Stream.Size);
HashData := Hash.RetrieveHash(HashSize);
TJwHash.FreeBuffer(HashData);
finally
Hash.Free;
Stream.Free;
end;
end;

At last we need to convert the binary hash into a hex-string:

for i:= 1 to HashSize do
begin
Result := Result + IntToHex(PByte(HashData)^,2);
inc(PByte(HashData));
end;
dec(PByte(HashData),HashSize); //neccessary to free HashData

Now we’re done and finally our function looks like this:

function GetFileHash(Algorithm: TJwHashAlgorithm; const Filename: String) : String;
var
Stream: TJwFileStreamEx;
Hash: TJwHash;
HashSize: Cardinal;
HashData: Pointer;
i: Integer;
begin
Stream := TJwFileStreamEx.Create(Filename,fmOpenRead);
Hash := TJwHash.Create(Algorithm);
try
Hash.HashData(Stream.Memory,Stream.Size);
HashData := Hash.RetrieveHash(HashSize);
for i:= 1 to HashSize do
begin
Result := Result + IntToHex(PByte(HashData)^,2);
inc(PByte(HashData));
end;
dec(PByte(HashData),HashSize);
TJwHash.FreeBuffer(HashData);
finally
Hash.Free;
Stream.Free;
end;
end;

How do I use this function?

// first param can be one of these values:
// haMD2, haMD4, haMD5, haSHA
Label1.Caption := GetFileHash(haSHA,‘C:\Progam Files\Program\AFile.ext’);

OK, but what is the advantage of TJwFileStreamEx over other Streams?

Download

Download the source and binaries of this example (260kiB). This includes the new and necessary JWSCL source files. However you need to download the whole package separately.

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Issuetracker

Christian Wimmer — Sun, 15 Jun 2008 14:46:15 +0000

The JEDI Community has an issue tracker where you can submit bugs, features and fixes. Please use this tracker for both JEDI projects API and WSCL.

http://homepages.borland.com/jedi/issuetracker

Switch to project “JEDI API” in the drop down field in the top right corner of the page.

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