Insert random noops to increase security against ROP attacks (clang)

A pass that adds random noops to X86 binaries to introduce diversity with the goal of increasing security against most return-oriented programming attacks.

Command line options:
  -noop-insertion // Enable noop insertion.
  -noop-insertion-percentage=X // X% of assembly instructions will have a noop prepended (default: 50%, requires -noop-insertion)
  -max-noops-per-instruction=X // Randomly generate X noops per instruction. ie. roll the dice X times with probability set above (default: 1). This doesn't guarantee X noop instructions.

In addition, the following 'quick switch' in clang enables basic diversity using default settings (currently: noop insertion and schedule randomization; it is intended to be extended in the future).
  -fdiversify

This is the clang part of the patch.
llvm part: D3392

http://reviews.llvm.org/D3393
Patch by Stephen Crane (@rinon)

llvm-svn: 225910

1 files changed, 11 insertions, 0 deletions

diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index d625c0e..4aecf22 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -3737,6 +3737,17 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
       getToolChain().getTriple().getArch() == llvm::Triple::aarch64_be)
     CmdArgs.push_back("-fallow-half-arguments-and-returns");
 
+  // Translate -frandom-seed to seed the LLVM RNG
+  if (Args.hasArg(options::OPT_frandom_seed_EQ)) {
+    StringRef seed = Args.getLastArgValue(options::OPT_frandom_seed_EQ);
+    CmdArgs.push_back("-backend-option");
+    CmdArgs.push_back(Args.MakeArgString("-rng-seed=" + seed));
+  }
+
+  if (Args.hasArg(options::OPT_fdiversify)) {
+    CmdArgs.push_back("-noop-insertion");
+  }
+
   if (Arg *A = Args.getLastArg(options::OPT_mrestrict_it,
                                options::OPT_mno_restrict_it)) {
     if (A->getOption().matches(options::OPT_mrestrict_it)) {