The man you want to talk to is actually Bryan Payne (CCed). He would also be able to supply you with all relevant source code for what we've done and perhaps relevant papers from IBM. I'm glad you're interested in this approach too, though we'll be using X509 certificate checking as well, so our solution is much more complicated! Initially we've put this code into the polled ide etherboot source, but will also move it into linuxbios soon.
On 18 Jan 2002, Eric W. Biederman wrote: > > Currently I am in the processes of extending the ELF boot loader > so that if you have an appropriate ELF note is in the ELF image > we can verify the checksum of the Image. I have seen enough corrupt > network downloads (when the ram is at fault) that I don't want to see > anymore. > > My first implementation will use a 2 byte 1's complement checksum. > Which has many very nice properties the nicest is that you can add or > subtract portions of the image and simply modify the checksum (not > recompute it), allow the checksum to be end-to-end even in the > presence of modification. > > Modification is important for the case of editing the command line > or adding a ramdisk to an already compiled kernel. > > Currently I checksum over a stream of bytes consisting of: > The ELF header + the ELF program header + the PT_LOAD segments in the > order the are listed in the program header. I was vague on how to do > this when I speced it all so I need to update my draft on this point. > > > Adam for the work on trusted booting I would like to include it as a > compile option. Since this is very similiar to what you are doing > any feedback would be appreciated. > > > Eric >
