Auto merge of zcash#1126 - ebfull:more-libsnark-changes, r=ebfull

Remove more from libsnark, and fix potential remote-DoS.

See zcash/libsnark#1 as well.

[`59adbef`](zcash/libsnark@59adbef) removes a remote-DoS that can occur if proofs are not well-formed.

[`e3779f9`](zcash/libsnark@e3779f9) removes more files that we do not need from libsnark.

[`11242d8`](zcash/libsnark@11242d8) replaces assertions that could be triggered by our verifier with exceptions.

Here in Zcash, we catch all exceptions from the verifier and return false.

Closes zcash#459, Closes zcash#69

depends/packages/libsnark.mk

@@ -3,8 +3,8 @@ $(package)_version=0.1
 $(package)_download_path=https://github.com/zcash/$(package)/archive/
 $(package)_file_name=$(package)-$($(package)_git_commit).tar.gz
 $(package)_download_file=$($(package)_git_commit).tar.gz
-$(package)_sha256_hash=43b0c921e8a1d556e70cf5c63c921db54f151842eb3cada029e3b92095e7b6f9
-$(package)_git_commit=a7031481fd8d2360337321401fe8e24f0359317a
+$(package)_sha256_hash=369fe9f5a8018eb46cce3cf50bfbf21419d8e963b25067ffd00cb9ac5c39f649
+$(package)_git_commit=11242d8afe304c8bcc252baec483f04a110d1dd4
 
 $(package)_dependencies=libgmp libsodium
 

src/zcash/JoinSplit.cpp

@@ -157,7 +157,11 @@ class JoinSplitCircuit : public JoinSplit<NumInputs, NumOutputs> {
             vpub_new
         );
 
-        return r1cs_ppzksnark_verifier_strong_IC<ppzksnark_ppT>(*vk, witness, r1cs_proof);
+        try {
+            return r1cs_ppzksnark_verifier_strong_IC<ppzksnark_ppT>(*vk, witness, r1cs_proof);
+        } catch (...) {
+            return false;
+        }
     }
 
     boost::array<unsigned char, ZKSNARK_PROOF_SIZE> prove(