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libgarble-rust

This is a port from C to Rust of Alex Malozemoff's libgarble. It produces a dynamic library (shared object) that should be a drop-in replacement (although only the functions needed to run his AES test circuit are currently implmented).

Installing dependencies

rustup

The easiest way to install rust is through rustup:

$ wget https://sh.rustup.rs -O rustup_installer
$ chmod +x ./rustup_installer
$ ./rustup_installer

Once rustup is installed, use your favorite editor to add source ~/.cargo/env to your .bashrc (to put the executables it installs on your PATH).

libgarble-rust has other dependencies, but they are automatically managed through cargo.

msgpack

The C driver program that benchmarks the garbling/evaluation of an AES circuit depends on the msgpack serialization library. If you're on any Debian-derived OS, install it via sudo apt-get install libmsgpack-dev. --with-msgpack=no is still passed to configure below to avoid fiddling with pkg-config manifests, but make aes manages to find the right version anyway.

Building and running

somedir/$ git clone https://github.com/amaloz/libgarble
somedir/$ git clone https://github.com/aweinstock314/libgarble-rust
somedir/libgarble$ autoreconf -f -i && ./configure --with-msgpack=no && make
somedir/libgarble/test$ make aes
somedir/libgarble/test$ ./aes > output_with_c_dylib.txt
somedir/libgarble-rust$ source setup_rustflags
somedir/libgarble-rust$ rustup override set nightly
somedir/libgarble-rust$ cargo build --release
somedir/libgarble-rust$ ./tamper_with_so.sh
somedir/libgarble/test$ ./aes > output_with_rust_dylib.txt

Correspondences between this and the C version

  • Some of the functions are direct transliterations from C (e.g. garble_{allocate_blocks,delete,new,seed}).
  • garble_{check,extract_labels} are fairly similar to their C versions, but use slice::from_raw_parts{,_mut} to make things more convenient (e.g. == on slices does structural equality).
  • garble_{garble,eval} are similar at a high-level to their C counterparts, but like check and extract_labels use more rust features for convenience.
  • _garble_{standard,halfgates,privacy_free} in the C are mostly the same, and were abstracted to garble_loop, with their inner-loop functions being passed as arguments (likewise with s/garble/eval/).
  • garble_{create_delta,random_block} were modified to use helper functions that don't touch global memory for the tweak (although the AES key is still global, since the API doesn't have anywhere else to stash the key between garble_seed and garble_garble).
  • aes_set_encrypt_key uses inline assembly instead of intrinsics, because I didn't know about the llvmint crate for intrinsics at the time.
  • aes_ecb_encrypt_blocks is templated over a choice of callers using inline assembly and LLVM intrinsics. I initially wrote it in assembly, but the interface between the inline assembly and rust code was generating unneccessary loads from memory to registers (vaesenc{,last} allow a memory operand for the AES key). Switching to LLVM intrinsics got a speedup in most places, but a slowdown for halfgates mode. I haven't found out the reason (I just tallied it up to processor magic), but the templates allow each callsite to pick the more performant one.