Close https://github.com/serai-dex/serai/issues/30.

An extremely minimal subset of Monero is now all that's built, and I'm 
sufficiently happy with it.

coins/monero/Cargo.toml

@@ -19,6 +19,8 @@ rand_chacha = { version = "0.3", optional = true }
 rand = "0.8"
 rand_distr = "0.4"
 
+subtle = "2.4"
+
 tiny-keccak = { version = "2", features = ["keccak"] }
 blake2 = { version = "0.10", optional = true }
 
@@ -31,13 +33,14 @@ transcript = { package = "flexible-transcript", path = "../../crypto/transcript"
 frost = { package = "modular-frost", path = "../../crypto/frost", features = ["ed25519"], optional = true }
 dleq = { path = "../../crypto/dleq", features = ["serialize"], optional = true }
 
-base58-monero = "1"
-monero = "0.16"
-
 hex = "0.4"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
+
+base58-monero = "1"
 monero-epee-bin-serde = "1.0"
+monero = "0.16"
+
 reqwest = { version = "0.11", features = ["json"] }
 
 [features]

coins/monero/build.rs

@@ -14,7 +14,6 @@ fn main() {
 
   // Use a file to signal if Monero was already built, as that should never be rebuilt
   // If the signaling file was deleted, run this script again to rebuild Monero though
-  // TODO: Move this signaling file into OUT_DIR once Monero is built statically successfully
   println!("cargo:rerun-if-changed=c/.build/monero");
   if !Path::new("c/.build/monero").exists() {
     if !Command::new("make").arg(format!("-j{}", &env::var("THREADS").unwrap_or("2".to_string())))
@@ -28,81 +27,46 @@ fn main() {
     }
   }
 
- println!("cargo:rerun-if-env-changed=OUT_DIR");
- if !Path::new(
-    &format!(
-      "{}/{}cncrypto.{}",
-      out_dir,
-      &env::consts::DLL_PREFIX,
-      &env::consts::DLL_EXTENSION
-    )
-  ).exists() {
-    let mut paths = vec![
-      "c/monero/build/release/contrib/epee/src/libepee.a".to_string(),
-      "c/monero/build/release/external/easylogging++/libeasylogging.a".to_string(),
-      "c/monero/build/release/external/randomx/librandomx.a".to_string()
-    ];
-
-    for (folder, lib) in [
-      ("common", "common"),
-      ("crypto", "cncrypto"),
-      ("crypto/wallet", "wallet-crypto"),
-      ("cryptonote_basic", "cryptonote_basic"),
-      ("cryptonote_basic", "cryptonote_format_utils_basic"),
-      ("", "version"),
-      ("device", "device"),
-      ("ringct", "ringct_basic"),
-      ("ringct", "ringct")
-    ] {
-      paths.push(
-        format!(
-          "c/monero/build/release/src/{}/{}{}.a",
-          folder,
-          &env::consts::DLL_PREFIX,
-          lib
-        )
-      );
-    }
-
-    for path in paths {
-      if !Command::new("cp").args(&[&path, out_dir]).status().unwrap().success() {
-        panic!("Failed to cp {}", path);
-      }
-    }
-  }
-
   println!("cargo:rerun-if-changed=c/wrapper.cpp");
-  if !Path::new(&format!("{}/{}wrapper.a", out_dir, &env::consts::DLL_PREFIX)).exists() {
-    cc::Build::new()
-      .file("c/wrapper.cpp")
-      .cpp(true)
-      .warnings(false)
-      .include("c/monero/contrib/epee/include")
-      .include("c/monero/src")
-      .compile("wrapper");
-  }
+  cc::Build::new()
+    .static_flag(true)
+    .warnings(false)
+    .extra_warnings(false)
+    .flag("-Wno-deprecated-declarations")
+
+    .include("c/monero/external/supercop/include")
+    .include("c/monero/contrib/epee/include")
+    .include("c/monero/src")
+    .include("c/monero/build/release/generated_include")
+
+    .define("AUTO_INITIALIZE_EASYLOGGINGPP", None)
+    .include("c/monero/external/easylogging++")
+    .file("c/monero/external/easylogging++/easylogging++.cc")
+
+    .file("c/monero/src/common/aligned.c")
+    .file("c/monero/src/common/perf_timer.cpp")
+
+    .include("c/monero/src/crypto")
+    .file("c/monero/src/crypto/crypto-ops-data.c")
+    .file("c/monero/src/crypto/crypto-ops.c")
+    .file("c/monero/src/crypto/keccak.c")
+    .file("c/monero/src/crypto/hash.c")
+
+    .include("c/monero/src/device")
+    .file("c/monero/src/device/device_default.cpp")
+
+    .include("c/monero/src/ringct")
+    .file("c/monero/src/ringct/rctCryptoOps.c")
+    .file("c/monero/src/ringct/rctTypes.cpp")
+    .file("c/monero/src/ringct/rctOps.cpp")
+    .file("c/monero/src/ringct/multiexp.cc")
+    .file("c/monero/src/ringct/bulletproofs.cc")
+    .file("c/monero/src/ringct/rctSigs.cpp")
+
+    .file("c/wrapper.cpp")
+    .compile("wrapper");
 
   println!("cargo:rustc-link-search={}", out_dir);
   println!("cargo:rustc-link-lib=wrapper");
-  println!("cargo:rustc-link-lib=ringct");
-  println!("cargo:rustc-link-lib=ringct_basic");
-  println!("cargo:rustc-link-lib=device");
-  println!("cargo:rustc-link-lib=cryptonote_basic");
-  println!("cargo:rustc-link-lib=cncrypto");
-  println!("cargo:rustc-link-lib=cryptonote_format_utils_basic");
-  println!("cargo:rustc-link-lib=version");
-  println!("cargo:rustc-link-lib=wallet-crypto");
-  println!("cargo:rustc-link-lib=easylogging");
-  println!("cargo:rustc-link-lib=epee");
-  println!("cargo:rustc-link-lib=common");
-  println!("cargo:rustc-link-lib=randomx");
-  println!("cargo:rustc-link-lib=unbound");
-  println!("cargo:rustc-link-lib=sodium");
-  println!("cargo:rustc-link-lib=boost_system");
-  println!("cargo:rustc-link-lib=boost_thread");
-  println!("cargo:rustc-link-lib=boost_filesystem");
-  println!("cargo:rustc-link-lib=hidapi-hidraw");
   println!("cargo:rustc-link-lib=stdc++");
-
-  println!("cargo:rustc-link-arg=-zmuldefs");
 }

coins/monero/c/wrapper.cpp

@@ -6,36 +6,50 @@
 #include "ringct/rctSigs.h"
 
 typedef std::lock_guard<std::mutex> lock;
-std::mutex rng_mutex;
 
+std::mutex rng_mutex;
 uint8_t rng_entropy[64];
-void rng(uint8_t* seed) {
-  // Set the first half to the seed
-  memcpy(rng_entropy, seed, 32);
-  // Set the second half to the hash of a DST to ensure a lack of collisions
-  crypto::cn_fast_hash("RNG_entropy_seed", 16, (char*) &rng_entropy[32]);
-}
 
 extern "C" {
-  void generate_random_bytes_not_thread_safe(size_t n, uint8_t* value) {
+  void rng(uint8_t* seed) {
+    // Set the first half to the seed
+    memcpy(rng_entropy, seed, 32);
+    // Set the second half to the hash of a DST to ensure a lack of collisions
+    crypto::cn_fast_hash("RNG_entropy_seed", 16, (char*) &rng_entropy[32]);
+  }
+}
+
+extern "C" void monero_wide_reduce(uint8_t* value);
+namespace crypto {
+  void generate_random_bytes_not_thread_safe(size_t n, void* value) {
     size_t written = 0;
     while (written != n) {
       uint8_t hash[32];
       crypto::cn_fast_hash(rng_entropy, 64, (char*) hash);
       // Step the RNG by setting the latter half to the most recent result
-      // Does not leak the RNG, even if the values are leaked (which they are expected to be) due to
-      // the first half remaining constant and undisclosed
+      // Does not leak the RNG, even if the values are leaked (which they are
+      // expected to be) due to the first half remaining constant and
+      // undisclosed
       memcpy(&rng_entropy[32], hash, 32);
 
       size_t next = n - written;
       if (next > 32) {
         next = 32;
       }
-      memcpy(&value[written], hash, next);
+      memcpy(&((uint8_t*) value)[written], hash, next);
       written += next;
     }
   }
 
+  void random32_unbiased(unsigned char *bytes) {
+    uint8_t value[64];
+    generate_random_bytes_not_thread_safe(64, value);
+    monero_wide_reduce(value);
+    memcpy(bytes, value, 32);
+  }
+}
+
+extern "C" {
   void c_hash_to_point(uint8_t* point) {
     rct::key key_point;
     ge_p3 e_p3;
@@ -62,16 +76,24 @@ extern "C" {
     std::stringstream ss;
     binary_archive<true> ba(ss);
     ::serialization::serialize(ba, bp);
-    uint8_t* res = (uint8_t*) calloc(ss.str().size(), 1); // malloc would also work
+    uint8_t* res = (uint8_t*) calloc(ss.str().size(), 1);
     memcpy(res, ss.str().data(), ss.str().size());
     return res;
   }
 
-  bool c_verify_bp(uint8_t* seed, uint s_len, uint8_t* s, uint8_t c_len, uint8_t* c) {
-    // BPs are batch verified which use RNG based challenges to ensure individual integrity
-    // That's why this must also have control over RNG, to prevent interrupting multisig signing
-    // while not using known seeds. Considering this doesn't actually define a batch,
-    // and it's only verifying a single BP, it'd probably be fine, but...
+  bool c_verify_bp(
+    uint8_t* seed,
+    uint s_len,
+    uint8_t* s,
+    uint8_t c_len,
+    uint8_t* c
+  ) {
+    // BPs are batch verified which use RNG based weights to ensure individual
+    // integrity
+    // That's why this must also have control over RNG, to prevent interrupting
+    // multisig signing while not using known seeds. Considering this doesn't
+    // actually define a batch, and it's only verifying a single BP,
+    // it'd probably be fine, but...
     lock guard(rng_mutex);
     rng(seed);
 
@@ -94,7 +116,15 @@ extern "C" {
     try { return rct::bulletproof_VERIFY(bp); } catch(...) { return false; }
   }
 
-  bool c_verify_clsag(uint s_len, uint8_t* s, uint8_t k_len, uint8_t* k, uint8_t* I, uint8_t* p, uint8_t* m) {
+  bool c_verify_clsag(
+    uint s_len,
+    uint8_t* s,
+    uint8_t k_len,
+    uint8_t* k,
+    uint8_t* I,
+    uint8_t* p,
+    uint8_t* m
+  ) {
     rct::clsag clsag;
     std::stringstream ss;
     std::string str;
@@ -121,6 +151,8 @@ extern "C" {
     rct::key msg;
     memcpy(msg.bytes, m, 32);
 
-    try { return verRctCLSAGSimple(msg, clsag, keys, pseudo_out); } catch(...) { return false; }
+    try {
+      return verRctCLSAGSimple(msg, clsag, keys, pseudo_out);
+    } catch(...) { return false; }
   }
 }

coins/monero/src/lib.rs

@@ -1,6 +1,10 @@
+use std::slice;
+
 use lazy_static::lazy_static;
 use rand_core::{RngCore, CryptoRng};
 
+use subtle::ConstantTimeEq;
+
 use tiny_keccak::{Hasher, Keccak};
 
 use curve25519_dalek::{
@@ -32,6 +36,29 @@ lazy_static! {
   static ref H_TABLE: EdwardsBasepointTable = EdwardsBasepointTable::create(&*H);
 }
 
+// Function from libsodium our subsection of Monero relies on. Implementing it here means we don't
+// need to link against libsodium
+#[no_mangle]
+unsafe extern "C" fn crypto_verify_32(a: *const u8, b: *const u8) -> isize {
+  isize::from(
+    slice::from_raw_parts(a, 32).ct_eq(slice::from_raw_parts(b, 32)).unwrap_u8()
+  ) - 1
+}
+
+// Offer a wide reduction to C. Our seeded RNG prevented Monero from defining an unbiased scalar
+// generation function, and in order to not use Monero code (which would require propagating its
+// license), the function was rewritten. It was rewritten with wide reduction, instead of rejection
+// sampling however, hence the need for this function
+#[no_mangle]
+unsafe extern "C" fn monero_wide_reduce(value: *mut u8) {
+  let res = Scalar::from_bytes_mod_order_wide(
+    std::slice::from_raw_parts(value, 64).try_into().unwrap()
+  );
+  for (i, b) in res.to_bytes().iter().enumerate() {
+    value.add(i).write(*b);
+  }
+}
+
 #[allow(non_snake_case)]
 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 pub struct Commitment {

processor/build.rs

@@ -1,3 +0,0 @@
-fn main() {
-  println!("cargo:rustc-link-arg=-zmuldefs");
-}