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Hi.
I have a whole bunch of DLLs on a server and I want to trace the CreateObject calls within the DLL classes so I can see how things are linked together.
I know that the whole concept of compiled DLLs is to encapsulate the implementation. However, is there a way to efficiently and accurate trace through these DLLs?
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I have a COM+ component. Until now i have only clients hosted into the same computer like my business component.
Now is needed to have clients on other computers, over the net, who must access data from my COM+ component.
The way is to deploy a DCOM component and make calls from clients to that DCOM.
But i dont want to copy the code from my COM+ component into the new DCOM component.
I know is possible to make a com to be like an exe DCOM, but i dont know how... Know somebody how ?
Adrian Bacaianu
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Since this is a COM+ component, you can instantiate it remotely too. You don't have to write a new DCOM server - thank God! (How would you provide all COM+ services in the DCOM server after all? rewrite them?)
Just call (from VB/VBScript)
Set obj = CreateObject(ProgID, Remote server name)
and you' ll get a remote instance of your component.
For C++ code, CoCreateInstanceEx will do the trick.
For DCOM to work, you need ports 135 & 1024-65535 open between your machines.
Hope I helped.
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Yes, was working, many thanks!
The speed isnt so good but that it is...
Adrian Bacaianu
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I have two classes, classA and classB.
Both these classes have got only pure virtual functions and nothing else.
But ClassA has got aggregation relationship with classB. For more clarity let us say, classA contains classB.
My question: whether classA can be treated as a COM compatible inteface.
Here my question is, whether this aggregation relationship does effect this ClassA not to be tratred as an Interface, as per COM spesification.
My requirement is that, when I create an object (component)of classA
say ObjA.
ObjA should also contain an object of classB say ObjB.
So that when ever I call a method on objA, it should be possible to delegate
or forward this call to objeB.
Thanks in advance for clarification.
Regards
Hara
Hara
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Why OLECHAR* maps to 'ref ushort' in c#?
And how do I pass strings.
Do I have to declare array: ushort[] arr = new ushort[100] fill with ascii codes and supply
'ref arr[0]'
I'm having problems with the following function:
IMarkupPointer::Right(BOOL fMove, MARKUP_CONTEXT_TYPE* pContext, IHTMLElement** ppElement, long* pcch, OLECHAR* pchText);
Please help
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Everything works fine with ushort array , I wish there were some easy convertion between array of uchar and string
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it is possible by writing a few lines code.
if you want to know how, please have a look at my articles or e-mail me
make a search by author fkocak
yours,
Fırat Koçak
Doing something is better than doing nothing. So ... Move !
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Whenever I want to create an out-of-proc COM server,I use MFC application wizard to generate Dialog based Application with Automation support. Then i delete all the dialog related stuff from it, derive a new class from CCmdTarget and implement functions that external applications can call.
Now i want to fire events from such out-of-proc server. Can anyone tell me how can i do so?? Any sample application would be extremely welcome.
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- Create a simple ATL Object.
- Create an event interface (dispinterface, see MSDN docs)
- Right click on the ATL class generated in step 1 and choose Add Connection Point. Select your event interface, and click ok.
- Use the
Fire_XX methods generated by the event proxy class.
It's real easy, you'll figure it out.
--
we dance to the sound of sirens
and we watch genocide to relax
we dance to the sound of sirens
we are the heroes of self-deception
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Hi,
Does somebody know a secure solution to ensure that the DLL an application
is talking to hasn't been replaced with a fake one?
I am thinking about implementing a "handshaking" procedure. With this
method, the application sends a "challenge" random message to the DLL. The DLL responds with a value calculated using a one-way hash function. The application checks the response against its own calculation of the expected hash value. If the values match, the authentication is acknowledged; otherwise the application is terminated.
Do you know other/better solutions? Does COM provides some solution?
Remark: I am developing both the application part and the DLL part.
Thanks.
antoine
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COM itself doesn't provide any solution for this (somehow you can use Licencing, but it is very easy to break).
Your solution can work, but have one weakpoint - it is quite easy to crack, because when the someone would like to switch the DLLs, he needs only to know the one-way hash you are using - if you will choose some standardized, say MD5, he can only with this knowledge calculate correct hash and return it to you exactly as your original DLL does. It is in fact secured only by the alg. of the one-way hash, and this alg. is stored in exe as well as in the DLL, so everybody can look to it and copy it.
Little bit better is a signing the code. If you will use the public key cryptography, the theory is simple, you have to calculate the cryptographic checksum of the DLL. Then the hash result is signed by your private key and stored in DLL.
In runtime, you take this blob from the DLL, calculate hash (of course except modified parts), compare it with the stored one and verify the signature by your public key stored say in a resources of the exe file. If the hashes match and the signature is OK, you are on the safe side.
This method is a bit safer, but also have some problem. It is quite easy to remove the checking code from exe .
In fact, there is no perfect software solution and depends only on the level of security you require for your application.
But in any case, there is a simple helper rule which says, if the system is secured, independently on the method you will use - If the costs for breaking such a system is higher (better significantly higher) than the benefits you can have from it, the system can be considered as safe.
Sorry for such an elaborate, but it is a deep night here and I cannot sleep somehow today...
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Forget dynamic linking if you want security. There are about 1001 different ways of intercepting a dynamically loaded DLL.
To make it as hard as possible, do static linking. At least then you put the cracker to work.
To be real pessimistic, there is no real way to protect software in currently available mainstream operating systems. Nobody has a rigid set of security policies implemented. There will always be ways to trick the system, some harder than others.
--
we dance to the sound of sirens
and we watch genocide to relax
we dance to the sound of sirens
we are the heroes of self-deception
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IEnumVARIANT *scrap;
IUnknownPtr Collection;
ConstraintsPtr ConstraintsList(GetConstraintsDispatch());
if (ConstraintsList->GetCount() > 0)
{
Collection = ConstraintsList->Get_NewEnum();
Collection->QueryInterface(IID_IEnumVARIANT, (void **)&scrap);
For some inexplicable reason the QueryInterface call above has suddenly stopped working...returning E_NOINTERFACE. It worked last week. It works on other machines in the office. It just doesn't work on mine. (This is old code that hasn't been modified in years and has never failed before...)
Any ideas? Tips? Anything? Anyone?
Please
Dan
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Sussed it, the following registry sub-keys, inexplicably, were AWOL:
[HKEY_CLASSES_ROOT\Interface\{00020404-0000-0000-C000-000000000046}\NumMethods]
@="7"
[HKEY_CLASSES_ROOT\Interface\{00020404-0000-0000-C000-000000000046}\ProxyStubClsid]
@="{00020421-0000-0000-C000-000000000046}"
[HKEY_CLASSES_ROOT\Interface\{00020404-0000-0000-C000-000000000046}\ProxyStubClsid32]
@="{00020421-0000-0000-C000-000000000046}"
Mad!
Dan
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Can I define an Interface, to have member variables in addition to pure virtual functions ?
Hara
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By design no. IDL interfaces are only exposing properties (which are special methods) and methods.
Members are contained in the actual implementation class :
class IMyInterface : public IUnknown
{
virtual HRESULT __stdcall Method1(...)=0;
virtual HRESULT __stdcall Method2(...)=0;
};
class MyInterfaceImpl : public IMyInterface
{
protected:
int m_SomeMember;
public:
virtual HRESULT __stdcall QueryInterface(const IID& iid, void** ppv) ;
virtual ULONG __stdcall AddRef() ;
virtual ULONG __stdcall Release() ;
virtual HRESULT __stdcall Method1(...);
virtual HRESULT __stdcall Method2(...);
}
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Thanks for your response. But The interface, that I want to design must have
an aggregation relation ship with some other interface.
How to do this ?
Hara
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Can you give a little more info? 1) Do you mean your COM object will be aggregated or that your COM object will aggregate the other COM object?; 2) Are you using ATL?
things could always be worse...
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Hi
I would like to describe the problem refering a picture in my word document.
Neither, I could insert my document nor even the picture.
Can you please send me your E-mail ID , so that I can mail you my document with detailed problem description of the problem.
Regards
Hara
Hara
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I've downloaded http://www.gotdotnet.com/userarea/keywordsrch.aspx?keyword=midi in order to implement a midi song in my app.
But the play(midi) command only works in a [STAThread] model and it stop my app until the music end.
I've few experience in C#.
Any way to fix it??
Any clue???
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Hi, I read the articles about COM basic and still have problems. I try to write a simple console application in vc++ 6.0. I want to use ActiveDesktop componet to handle some info about wallpaper and patern. Also I have an example code. But there is no info about following thing.
In the code there are some variables like CLSID_ActiveDesktop or CLSCTX_INPROC_SERVER.
in which header they are defined. If your answer is comdef.h I include it and it only have some structs IActiveDesktop. Also I found that CLSCTX_INPROC_SERVER is defined in objbase.h but it still get error when I use CLSCTX_INPROC_SERVER. When I write 1 it is ok.
Another thing I could not get last parameter of CoCreateInstance.
here what I try to work and it gives 4 error.
<br />
<br />
#include<iostream.h><br />
#include<objbase.h><br />
#include<comdef.h><br />
<br />
HRESULT hr;<br />
int main()<br />
{<br />
IActiveDesktop *pIActiveDesktop;<br />
<br />
CoInitialize ( NULL ); <br />
<br />
hr = CoCreateInstance( CLSID_ActiveDesktop, NULL, CLSCTX_INPROC_SERVER,<br />
IID_IActiveDesktop, &pIActiveDesktop);<br />
<br />
cout<<hr<<"\n";<br />
<br />
return 0; <br />
}
karanba
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check if you have correctly set the switches or how it is called.
for example if it is defined in your stdafx.h (or simply before you include any of windows/com headers):
#ifndef _WIN32_WINNT<br />
#define _WIN32_WINNT 0x0400<br />
#endif
Possibly you will need to define also version of your explorer etc.
This is because some definitions in standard windows headers are conditionally compiled and if you do not define correct switches, some functions and constants are simply ommited by the compiler - even if you can see it in headers....
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Ok well this is the code and it gives only error at the line which I put a confused face image near it. VC++6.0 says that
\selman\desktop\workarea\comclienta\cpp1.cpp(27) : error C2664: 'CoCreateInstance' : cannot convert parameter 1 from 'char [37]' to 'const struct _GUID &'
Reason: cannot convert from 'char [37]' to 'const struct _GUID'
No constructor could take the source type, or constructor overload resolution was ambiguous But I check many things that I could not found the reason. please give me an explanation
#include<iostream.h>
#include<objbase.h>
#include<comdef.h>
HRESULT hr;
int main()
{
IActiveDesktop *pIActiveDesktop;
CoInitialize ( NULL );
hr = CoCreateInstance( "75048700-ef1f-11d0-9888-006097deacf9",
NULL,
CLSCTX_INPROC_SERVER,
"f490eb00-1240-11d1-9888-006097deacf9",
(void**) &pIActiveDesktop);
cout<<hr<<"\n";
cout<<hr;
return 0;
}
karanba
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I see. The problem is in parameter "f490eb00-1240-11d1-9888-006097deacf9", this and "75048700-ef1f-11d0-9888-006097deacf9". The CoCreateInstance is not designed to handle GUIDs in such a way.
It expect pointer/reference to some memory where GUID is stored in numeric format.
For calls to functions you can use the symbolic names like
CLSID_ActiveDesktop instead of "75048700-ef1f-11d0-9888-006097deacf9"
and IID_IActiveDesktop instead of the second one.
Then the call should looks like that (I hope so):
hr = CoCreateInstance( CLSID_ActiveDesktop, NULL, CLSCTX_INPROC_SERVER, IID_IActiveDesktop,(void**) &pIActiveDesktop);
But for easier coding I would recomend you to use smart pointers from ATL, then the code will looks like this one:
<br />
CComPtr<IActiveDesktop> spActDesktop;<br />
spActDesktop.CoCreateInstance( CLSID_ActiveDesktop );
which is much easier to read, and also the smart pointer takes a care about reference counting.
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