More Information About MSRPC

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MSRPC (Microsoft Remote Procedure Call) is a modified version of DCE/RPC. Additions include support for Unicode strings, implicit handles, inheritance of interfaces (which are extensively used in DCOM), and complex calculations in the variable-length string and structure paradigms already present in DCE/RPC.

Example

The DCE 1.0 reference implementation only allows such constructs as "size_is(len)", or possibly "size_is(len-1)". MSRPC allows much more complex constructs such as "size_is(len / 2 - 1)" and even "length_is ((max & ~0x7) + 0x7)" which is one quite common expression in DCOM IDL files.

Use

MSRPC was used by Microsoft to seamlessly create a client/server model in Windows NT, with very little effort. For example, the Windows Server domains protocols are entirely MSRPC based, as is Microsoft's DNS administrative tool. Microsoft Exchange Server 5.5's administrative front-ends are all MSRPC client/server applications, and its MAPI was made more secure by "proxying" MAPI over a set of simple MSRPC functions that enable encryption at the MSRPC layer without involving the MAPI protocol.

History

MSRPC is derived from the Distributed Computing Environment 1.1 reference implementation from the Open Software Foundation, but has been copyrighted by Microsoft. DCE/RPC was originally commissioned by the Open Software Foundation, an industry consortium to set vendor- and technology-neutral open standards for computing infrastructure. None of the Unix vendors (now represented by the Open Group), wanted to use the complex DCE or such components as DCE/RPC at the time.

The Microsoft proprietary technology, Distributed Component Object Model (DCOM) is for software components distributed across several networked computers to communicate with each other. The "D" was added to COM because of extensive use of DCE/RPC. DCOM, which originally was called "Network OLE", extends Microsoft's COM, and provides the communication substrate under Microsoft's COM+ application server infrastructure. It has been deprecated in favor of Microsoft .NET Framework. Microsoft donated DCOM to the Open Group.^{[citation needed]}

Other implementations

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DCE: The Open Group Distributed Computing Environment DCE is now available as open source under the LGPL. The entire DCE 1.2.2 release and may be downloaded over the web. http://www.opengroup.org/dce/download/ The release is big, consisting of about 100 ".tar.gz" files that take up 170 Megabytes.

FreeDCE is the DCE 1.1 reference implementation ported to Linux, supports 64-bit platforms, and is autoconf'd to make porting to further platforms much easier: a Win32 port is underway.

Entegrity Solutions licensed the OSF's entire DCE 1.2.2 source code and ported it to Win32, creating a product called PC/DCE - see http://support.entegrity.com/private/pcdce32.asp

Samba contains an implementation of MSRPC that is intended to be network-interoperable and IDL-interoperable with MSRPC. It is not binary-interoperable with MSRPC.

The Wine Project contains an implementation of MSRPC that is intended to be binary-interoperable and IDL-interoperable with MSRPC. It is not network-interoperable with MSRPC.

There also appears to be a DCE/RPC interoperable implementation in Java - http://jarapac.sourceforge.net/ FreeDCE

External links

• MSRPC at TechNet
• [1], a chapter on MSRPC from a technical article by Jean-Baptiste Marchand.

References