Determine whether .NET assemblies were built from the same source

Question

Does anyone know of a way to compare two .NET assemblies to determine whether they were built from the "same" source files?

I am aware that there are some differencing utilities available, such as the plugin for Reflector, but I am not interested in viewing differences in a GUI, I just want an automated way to compare a collection of binaries to see whether they were built from the same (or equivalent) source files. I understand that multiple different source files could produce the same IL, and realise that the process would only be sensitive to differences in the IL, not the original source.

The main obstacle to just comparing the byte streams for the two assemblies is that .NET includes a field called "MVID" (Module Version Identifier) the assembly. This appears to have a different value for every compilation, so if you build the same code twice the assembly will be different.

A related question is, does anyone know how to force the MVID to be the same for each compilation? This would avoid us needing to have a comparison process that is insensitive to differences in the value of the MVID. A consistent MVID would be preferable, as this means that standard checksums could be used.

The background behind this is that a third-party company is responsible for independently reviewing and signing off our releases, prior to us being permitted to release to Production. This includes reviewing the source code. They want to independently confirm that the source code we give them matches the binaries that we earlier built, tested and currently plan to deploy. We are looking for a process that allows them to independently build the system from the source we supply them with, and the compare the checksums against the checksums for the binaries we have tested.

BTW. Please note that we are using continuous integration, automated builds, source control etc. The issue is not related to an internal lack of control over what source files went into a given build. The issue is that a third party is responsible for verifying that the source we give them produces the same binaries that we have tested and plan to put into Production. They should not be trusting any of our internal systems or controls, including the build server or the source code control system. All they care about is getting the source associated with the build, performing the build themselves, and verifying that the outputs match what we say we are deploying.

The runtime speed of the comparison solution is not particularly important.

thanks

Answer 1

It's not too painful to use command-line tools to filter out MVID and date-time stamps from a text representation of the IL. Suppose file1.exe and file2.exe are built from the same sources:

c:\temp> ildasm /all /text file1.exe | find /v "Time-date stamp:" | find /v "MVID" > file1.txt

c:\temp> ildasm /all /text file2.exe | find /v "Time-date stamp:" | find /v "MVID" > file2.txt

c:\temp> fc file1.txt file2.txt

Comparing files file1.txt and FILE2.TXT

FC: no differences encountered