Ximin Luo: > Mike Frysinger: >> On 28 Jul 2016 15:15, Florian Weimer wrote: >>> On 03/09/2016 05:30 PM, Mike Frysinger wrote: >>>> would it be so terrible to properly marshall this data ? >>> >>> Ximin Luo and I discussed this and I wonder if it is possible to read >>> out the libc.so.6 build ID if it is present. It should indirectly call >>> all the layout dependencies and be reasonably easy to access because it >>> is in an allocated section (and we might want to print it from an >>> libc.so.6 invocation, too). >>> >>> We still need the time-based approach if the build ID is not available, >>> but I expect most distributions will have something like it. >>> >>> The Debian bug is: >>> >>> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=783210 >>> >>> (Also Cc:ed) >> >> agreed that build-id should be an acceptable replacement for what the >> code is doing today, but in order to pull that off, i guess you'd have >> to have to do a configure test to see if build-id is active ? if you >> leave the logic to runtime, you'd still need to include the datetime >> stamp in the object which would still make the build unreproducible. >> >> this also doesn't really cover the quoted idea of marshalling the data >> between client & server :). >> -mike >> > > Hi all, > > I've written a small program that prints out the Build IDs of all the objects > that are dynamically linked to it, plus itself. > > It works well, although I'm not a C expert so I don't know if it is portable > enough. For example, I hard-code some >>2 <<2s in there, along with a uint8_t > - I didn't see a corresponding ElfW(xxx) type in elf.h > > Another downside is it needs to be linked against libdl, which I think is not > the case currently with nscd. I'm not sure if this carries extra security > risk or whatever. >
Oh! Actually it doesn't need to be linked against libdl. That was from an earlier version of the code where I was using dlinfo instead of dl_iterate_phdr. But this latter function doesn't need extra libs. :) > An alternative would be to detect the build-id *at build time* and then > monkey-patch it into the binary itself. > > What do you all think? How shall I proceed? > X -- GPG: ed25519/56034877E1F87C35 GPG: rsa4096/1318EFAC5FBBDBCE https://github.com/infinity0/pubkeys.git