trying to make I_NetLogonControl2 work with JNA

[Amritanshu]

Hello,
I am using JNA version 5.0.0 to invoke a Win32 API part of NetAPI32.dll

The function prototype for the API looks like this :

DWORD _stdcall I_NetLogonControl2( LPCWSTR ServerName, DWORD FunctionCode, DWORD QueryLevel, LPBYTE Data, LPBYTE *Buffer ); [0]

For the FunctionCode (NETLOGON_CONTROL_TC_VERIFY) I am using, Data is expected to be an address of WCHAR* string that is null terminated (the data type is LPWSTR *).

While the Instance is declared as follows in my code

static interface NetAPI extends StdCallLibrary {
            int I_NetLogonControl2( WString serverName, int functionCode, int queryLevel, PointerByReference data, PointerByReference buffer);
            NetAPI INSTANCE = (NetAPI) Native.loadLibrary("netapi32", NetAPI.class, W32APIOptions.DEFAULT_OPTIONS); 

}


The call to the function is made using the following code snippet:

     String domainName =  new String("fabrikam.com");
     PointerByReference buffer = new PointerByReference();

     Pointer ptr = new Memory((domainName.length() + 1) * Native.WCHAR_SIZE);

     ptr.setWideString(0, domainName);

     PointerByReference data = new PointerByReference();

     data.setPointer(ptr);

     int i = NetAPI.INSTANCE.I_NetLogonControl2(null, 10, 2, data, buffer);

It throws an IMA exception :

Exception in thread "main" java.lang.Error: Invalid memory access

at com.sun.jna.Native.invokeInt(Native Method)

at com.sun.jna.Function.invoke(Function.java:425)

at com.sun.jna.Function.invoke(Function.java:360)

The exception is being thrown while accessing the second last argument - 'data'. What am I missing ? How do I go about debugging this issue.

Instead of SetWideString, I have tried to manually set the memory in ptr to the expected values directly byte-by-byte it didn't make any difference.

Any suggestions will help.

Many thanks!

[0] https://docs.microsoft.com/en-us/windows/desktop/api/lmaccess/nf-lmaccess-i_netlogoncontrol2

[Václav Haisman]

On Tue, 23 Oct 2018 at 14:36, Amritanshu <amrit...@gmail.com> wrote:

Hello,
I am using JNA version 5.0.0 to invoke a Win32 API part of NetAPI32.dll

The function prototype for the API looks like this :

DWORD _stdcall I_NetLogonControl2( LPCWSTR ServerName, DWORD FunctionCode, DWORD QueryLevel, LPBYTE Data, LPBYTE *Buffer ); [0]

LPBYTE is just BYTE *

 

For the FunctionCode (NETLOGON_CONTROL_TC_VERIFY) I am using, Data is expected to be an address of WCHAR* string that is null terminated (the data type is LPWSTR *).

While the Instance is declared as follows in my code

static interface NetAPI extends StdCallLibrary {
            int I_NetLogonControl2( WString serverName, int functionCode, int queryLevel, PointerByReference data, PointerByReference buffer);

`PointerByReference data` is `BYTE ** data`. You only want `Pointer data` here, I think.

 

            NetAPI INSTANCE = (NetAPI) Native.loadLibrary("netapi32", NetAPI.class, W32APIOptions.DEFAULT_OPTIONS); 

}


The call to the function is made using the following code snippet:

     String domainName =  new String("fabrikam.com");
     PointerByReference buffer = new PointerByReference();

     Pointer ptr = new Memory((domainName.length() + 1) * Native.WCHAR_SIZE);

     ptr.setWideString(0, domainName);

     PointerByReference data = new PointerByReference();

     data.setPointer(ptr);

     int i = NetAPI.INSTANCE.I_NetLogonControl2(null, 10, 2, data, buffer);

It throws an IMA exception :

Exception in thread "main" java.lang.Error: Invalid memory access

at com.sun.jna.Native.invokeInt(Native Method)

at com.sun.jna.Function.invoke(Function.java:425)

at com.sun.jna.Function.invoke(Function.java:360)

The exception is being thrown while accessing the second last argument - 'data'. What am I missing ? How do I go about debugging this issue.

Instead of SetWideString, I have tried to manually set the memory in ptr to the expected values directly byte-by-byte it didn't make any difference.

Any suggestions will help.

Many thanks!

[0] https://docs.microsoft.com/en-us/windows/desktop/api/lmaccess/nf-lmaccess-i_netlogoncontrol2

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VH

[Amritanshu]

`PointerByReference data` is `BYTE ** data`. You only want `Pointer data` here, I think.

No. That's what one would think while giving it a cursory look.  

Have a look at: 

https://docs.microsoft.com/en-us/windows/desktop/api/lmaccess/nf-lmaccess-i_netlogoncontrol2 

As stated before:

For the FunctionCode (NETLOGON_CONTROL_TC_VERIFY) I am using, Data is expected to be an address of WCHAR* string that is null terminated (the data type is LPWSTR *).

Here is how it is used in C/C++.

   int wmain(int argc, wchar_t **argv ) {
      ...

      LPBYTE domainName = (LPBYTE)argv[1];
      int ret = I_NetLogonControl2(NULL, NETLOGON_CONTROL_TC_VERIFY, 2, (LPBYTE)&domainName, (LPBYTE*)&buffer);

}

[mbla...@doppel-helix.eu]

Václav is right, the binding is not correct. However it would most probably work, as the API expects a wchar_t**:

Carries input data that depends on the value specified in the FunctionCode parameter. The NETLOGON_CONTROL_REDISCOVER and NETLOGON_CONTROL_TC_QUERY function codes specify the trusted domain name (the data type is LPWSTR *).

The problem is in the use of Pointer#setPointer here:

String domainName = new String("fabrikam.com");
PointerByReference buffer = new PointerByReference();
Pointer ptr = new Memory((domainName.length() + 1) * Native.WCHAR_SIZE);
ptr.setWideString(0, domainName);
PointerByReference data = new PointerByReference();

data.setPointer(ptr); // This should be data.setValue(ptr);

// or directly instantiate via:

// PointerByReference data = new PointerByReference(ptr);

int i = NetAPI.INSTANCE.I_NetLogonControl2(null, 10, 2, data, buffer);

Hope that helps,

Matthias

[Amritanshu]

Thanks Matthias. I will give this a try and update everyone.