Hi!
I have a rather special question here. I'd like to write a wrapper
for a .NET assembly, and register that on my server so that the people on
my server call my assembly instead of the standard .NET assembly. Reason
is that I want to include some additional security checks in my assembly,
to prevent everybody from the calling the .NET assembly unchecked. So,
writing the wrapper is no problem, but I'm not sure how/if it is possible
to register my assembly on the server to be called *instead* of the
original assembly, using the original name. So, e.g. if the customer
creates an instance of System.Data.Ole Db.OleDbCommand , I want an instance
from *my* System.Data.Ole Db.OleDbCommand to be created (that in turn will
eventually create an instance of the real System.Data.Ole Db.OleDbCommand ,
granted the caller will pass my security checks). I don't want the customer
to have to call something like System.Data.MyC ustomOleDb.OleD bCommand,
since my class won't be available at their client computer when they create
their apps, and it will be just easier otherwise.
I remember that achieving the above was no probelm with COM, but is it
possible in .NET as well?
TIA,
Thomas
15  2294 
Thomas,
My understanding is the security built into .NET prevents this from
happening for largely the opposite reason then you are wanting it to happen.
In that with .NET security I cannot introduce an assembly that reduces the
security of the standard assemblies.
I cannot replace the System.Data.Ole Db.OleDbCommand with an object that will
bypass the System.Data.Ole Db.OleDbPermiss ion permissions.
For a good starting point on articles on .NET security see: http://msdn.microsoft.com/library/de...rksecurity.asp
Hope this helps
Jay
"Thomas Christmann" <th************ ***@online.de> wrote in message
news:5t******** *************** ****@40tude.net ... Hi!
I have a rather special question here. I'd like to write a wrapper
for a .NET assembly, and register that on my server so that the people on
my server call my assembly instead of the standard .NET assembly. Reason
is that I want to include some additional security checks in my assembly,
to prevent everybody from the calling the .NET assembly unchecked. So,
writing the wrapper is no problem, but I'm not sure how/if it is possible
to register my assembly on the server to be called *instead* of the
original assembly, using the original name. So, e.g. if the customer
creates an instance of System.Data.Ole Db.OleDbCommand , I want an instance
from *my* System.Data.Ole Db.OleDbCommand to be created (that in turn will
eventually create an instance of the real System.Data.Ole Db.OleDbCommand ,
granted the caller will pass my security checks). I don't want the
customer to have to call something like System.Data.MyC ustomOleDb.OleD bCommand,
since my class won't be available at their client computer when they
create their apps, and it will be just easier otherwise.
I remember that achieving the above was no probelm with COM, but is it
possible in .NET as well?
TIA,
Thomas
Thomas,
My understanding is the security built into .NET prevents this from
happening for largely the opposite reason then you are wanting it to happen.
In that with .NET security I cannot introduce an assembly that reduces the
security of the standard assemblies.
I cannot replace the System.Data.Ole Db.OleDbCommand with an object that will
bypass the System.Data.Ole Db.OleDbPermiss ion permissions.
For a good starting point on articles on .NET security see: http://msdn.microsoft.com/library/de...rksecurity.asp
Hope this helps
Jay
"Thomas Christmann" <th************ ***@online.de> wrote in message
news:5t******** *************** ****@40tude.net ... Hi!
I have a rather special question here. I'd like to write a wrapper
for a .NET assembly, and register that on my server so that the people on
my server call my assembly instead of the standard .NET assembly. Reason
is that I want to include some additional security checks in my assembly,
to prevent everybody from the calling the .NET assembly unchecked. So,
writing the wrapper is no problem, but I'm not sure how/if it is possible
to register my assembly on the server to be called *instead* of the
original assembly, using the original name. So, e.g. if the customer
creates an instance of System.Data.Ole Db.OleDbCommand , I want an instance
from *my* System.Data.Ole Db.OleDbCommand to be created (that in turn will
eventually create an instance of the real System.Data.Ole Db.OleDbCommand ,
granted the caller will pass my security checks). I don't want the
customer to have to call something like System.Data.MyC ustomOleDb.OleD bCommand,
since my class won't be available at their client computer when they
create their apps, and it will be just easier otherwise.
I remember that achieving the above was no probelm with COM, but is it
possible in .NET as well?
TIA,
Thomas
> I cannot replace the System.Data.Ole Db.OleDbCommand with an object that will bypass the System.Data.Ole Db.OleDbPermiss ion permissions.
Is there a good reason why not? Is it strictly not possible, or is it just
that OleDbPermission s relies on OleDbCommand being there, and being named
like that? In which case I could maybe replace OleDbCommand as well...
Maybe I should clear this up a bit: My aim is not to really replace OleDb
completely, I just would like to have all ASP.NET calls to everything below
System.Data.Ole Db to be "routed" to *my* version of System.Data.Ole Db.*
(which would act like a proxy to the real System.Data.Ole Db). So, I don't
want to replace it, I just want to "hijack" it's name, system wide. In COM
this was easily acheived by just going to the registry and replacing the
value of the ProgID key of the old component with something like
"component. old" and giving your new component the original name of the old
component, in the same key, respectively. The new component would then
reference the old one by calling component.old, and system wide, the new
component would replace the old component (and would act like a proxy).
THIS I would like to achieve with .NET assemblies. Possible? If no, why
not? :-)
Thanks,
Thomas
> I cannot replace the System.Data.Ole Db.OleDbCommand with an object that will bypass the System.Data.Ole Db.OleDbPermiss ion permissions.
Is there a good reason why not? Is it strictly not possible, or is it just
that OleDbPermission s relies on OleDbCommand being there, and being named
like that? In which case I could maybe replace OleDbCommand as well...
Maybe I should clear this up a bit: My aim is not to really replace OleDb
completely, I just would like to have all ASP.NET calls to everything below
System.Data.Ole Db to be "routed" to *my* version of System.Data.Ole Db.*
(which would act like a proxy to the real System.Data.Ole Db). So, I don't
want to replace it, I just want to "hijack" it's name, system wide. In COM
this was easily acheived by just going to the registry and replacing the
value of the ProgID key of the old component with something like
"component. old" and giving your new component the original name of the old
component, in the same key, respectively. The new component would then
reference the old one by calling component.old, and system wide, the new
component would replace the old component (and would act like a proxy).
THIS I would like to achieve with .NET assemblies. Possible? If no, why
not? :-)
Thanks,
Thomas
> Is there a good reason why not? Is it strictly not possible, or is it just that OleDbPermission s relies on OleDbCommand being there, and being named
like that? In which case I could maybe replace OleDbCommand as well...
Security.
If someone was using an existing method in OleDB type that did this:
Begin SomeMethod
Demand Permissions
If Demand OK Then do secure action
End SomeMethod
Now you replace the assembly and SomeMethod with your own version:
Begin SomeMethod
do secure action
End SomeMethod
This is a security breach, no?
Not to mention when .NET applications are built, the resulting manifest
contains which assemblies its dependent upon, along with versions, along
with public key tokens.
The better thing to do is have your clients rely on the standard data
provider interfaces instead, use the factory pattern which can be configured
to pass back your objects or OleDB objects.
"Thomas Christmann" <th************ ***@online.de> wrote in message
news:9n******** *************** *****@40tude.ne t... I cannot replace the System.Data.Ole Db.OleDbCommand with an object that
will bypass the System.Data.Ole Db.OleDbPermiss ion permissions.
Is there a good reason why not? Is it strictly not possible, or is it just
that OleDbPermission s relies on OleDbCommand being there, and being named
like that? In which case I could maybe replace OleDbCommand as well...
Maybe I should clear this up a bit: My aim is not to really replace OleDb
completely, I just would like to have all ASP.NET calls to everything
below System.Data.Ole Db to be "routed" to *my* version of System.Data.Ole Db.*
(which would act like a proxy to the real System.Data.Ole Db). So, I don't
want to replace it, I just want to "hijack" it's name, system wide. In COM
this was easily acheived by just going to the registry and replacing the
value of the ProgID key of the old component with something like
"component. old" and giving your new component the original name of the old
component, in the same key, respectively. The new component would then
reference the old one by calling component.old, and system wide, the new
component would replace the old component (and would act like a proxy).
THIS I would like to achieve with .NET assemblies. Possible? If no, why
not? :-)
Thanks,
Thomas
> Begin SomeMethod Demand Permissions
If Demand OK Then do secure action
End SomeMethod
Now you replace the assembly and SomeMethod with your own version:
Begin SomeMethod
do secure action
End SomeMethod
This is a security breach, no?
Well, yes, I understand this would be a security breach, but I was looking
more for why it isn't allowed. Technically, I mean. What prevents it? CAS?
Something deep inside the assembly itself?
Not to mention when .NET applications are built, the resulting manifest
contains which assemblies its dependent upon, along with versions, along
with public key tokens.
Ah okay, key tokens, that I understand. Okay, thats a reason it wouldn't
work, true.
The better thing to do is have your clients rely on the standard data
provider interfaces instead, use the factory pattern which can be configured
to pass back your objects or OleDB objects.
Well, I can't really use OleDB. See, the scenario is that I host ASP.NET
applications on my server, but I don't want to run full trust.
Unfortunately OleDB only works with full trust. So, an article on the MS
website explained that you could write a wrapper around some OleDB
functionality, then register that in gac (to be run under full trust), and
call the (full trusted, globally available) assembly from ASP.NET
applications running under partial trust. Now, this works just fine, I bet,
but the ultimate goal would be to give my clients the convinience of not
having to use my stuff, but the MS stuff instead (from their point of
view).
Ciao,
Thomas
Thomas,
I'm not sure what the full reason is. Nor if you really can or cannot do
it.
I believe you missed my point, one very good reason to prevent it is
security, as JD explained, and I attempted to explain. What you are
attempting to do is how one might bypass security.
Just a thought
Jay
"Thomas Christmann" <th************ ***@online.de> wrote in message
news:9n******** *************** *****@40tude.ne t... I cannot replace the System.Data.Ole Db.OleDbCommand with an object that
will bypass the System.Data.Ole Db.OleDbPermiss ion permissions.
Is there a good reason why not? Is it strictly not possible, or is it just
that OleDbPermission s relies on OleDbCommand being there, and being named
like that? In which case I could maybe replace OleDbCommand as well...
Maybe I should clear this up a bit: My aim is not to really replace OleDb
completely, I just would like to have all ASP.NET calls to everything
below System.Data.Ole Db to be "routed" to *my* version of System.Data.Ole Db.*
(which would act like a proxy to the real System.Data.Ole Db). So, I don't
want to replace it, I just want to "hijack" it's name, system wide. In COM
this was easily acheived by just going to the registry and replacing the
value of the ProgID key of the old component with something like
"component. old" and giving your new component the original name of the old
component, in the same key, respectively. The new component would then
reference the old one by calling component.old, and system wide, the new
component would replace the old component (and would act like a proxy).
THIS I would like to achieve with .NET assemblies. Possible? If no, why
not? :-)
Thanks,
Thomas
Thomas,
Oh! another reason to prevent it, your assembly could introduce
instabilities in the framework.
I can here the calls to MS Support now. I'm using OleDbCOmmand on my machine
and it works fine, I deploy it to my ISP and I get a Argument Out Of Range
exception. (as your wrapper had a slight flaw in it, that you did not
catch...)
If you find it documented how to do it, I hope you will post here.
Just another thought
Jay
"Thomas Christmann" <th************ ***@online.de> wrote in message
news:9n******** *************** *****@40tude.ne t... I cannot replace the System.Data.Ole Db.OleDbCommand with an object that
will bypass the System.Data.Ole Db.OleDbPermiss ion permissions.
Is there a good reason why not? Is it strictly not possible, or is it just
that OleDbPermission s relies on OleDbCommand being there, and being named
like that? In which case I could maybe replace OleDbCommand as well...
Maybe I should clear this up a bit: My aim is not to really replace OleDb
completely, I just would like to have all ASP.NET calls to everything
below System.Data.Ole Db to be "routed" to *my* version of System.Data.Ole Db.*
(which would act like a proxy to the real System.Data.Ole Db). So, I don't
want to replace it, I just want to "hijack" it's name, system wide. In COM
this was easily acheived by just going to the registry and replacing the
value of the ProgID key of the old component with something like
"component. old" and giving your new component the original name of the old
component, in the same key, respectively. The new component would then
reference the old one by calling component.old, and system wide, the new
component would replace the old component (and would act like a proxy).
THIS I would like to achieve with .NET assemblies. Possible? If no, why
not? :-)
Thanks,
Thomas
> What prevents it? CAS?
Yep. Unfortunately OleDB only works with full trust.
No kidding. I never realized this or ran into a problem because of it.
"Thomas Christmann" <th************ ***@online.de> wrote in message
news:53******** *************** *******@40tude. net... Begin SomeMethod
Demand Permissions
If Demand OK Then do secure action
End SomeMethod
Now you replace the assembly and SomeMethod with your own version:
Begin SomeMethod
do secure action
End SomeMethod
This is a security breach, no?
Well, yes, I understand this would be a security breach, but I was looking
more for why it isn't allowed. Technically, I mean. What prevents it? CAS?
Something deep inside the assembly itself?
Not to mention when .NET applications are built, the resulting manifest
contains which assemblies its dependent upon, along with versions, along
with public key tokens.
Ah okay, key tokens, that I understand. Okay, thats a reason it wouldn't
work, true.
The better thing to do is have your clients rely on the standard data
provider interfaces instead, use the factory pattern which can be
configured to pass back your objects or OleDB objects.
Well, I can't really use OleDB. See, the scenario is that I host ASP.NET
applications on my server, but I don't want to run full trust.
Unfortunately OleDB only works with full trust. So, an article on the MS
website explained that you could write a wrapper around some OleDB
functionality, then register that in gac (to be run under full trust), and
call the (full trusted, globally available) assembly from ASP.NET
applications running under partial trust. Now, this works just fine, I
bet, but the ultimate goal would be to give my clients the convinience of not
having to use my stuff, but the MS stuff instead (from their point of
view).
Ciao,
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