From 1ec9c3aa4bf99022df969de20acc84ff49314910 Mon Sep 17 00:00:00 2001
From: Matt Corallo <git@bluematt.me>
Date: Mon, 16 Apr 2018 16:55:03 -0400
Subject: [PATCH] Provide fallback for crypto's fixed_time_eq on non-x86/arm
 targets

---
 Cargo.toml                              |  4 ++++
 build.rs                                | 10 ++++++++++
 fuzz/Cargo.toml                         |  7 +++++++
 fuzz/src/util/rust_crypto_nonstd_arch.c |  1 +
 src/util/rust_crypto_nonstd_arch.c      | 13 +++++++++++++
 5 files changed, 35 insertions(+)
 create mode 100644 build.rs
 create mode 120000 fuzz/src/util/rust_crypto_nonstd_arch.c
 create mode 100644 src/util/rust_crypto_nonstd_arch.c

diff --git a/Cargo.toml b/Cargo.toml
index bb00a9239..f097d7fbc 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -8,6 +8,7 @@ description = """
 A Bitcoin Lightning implementation in Rust.
 Still super-early code-dump quality and is missing large chunks. See README in git repo for suggested projects if you want to contribute. Don't have to bother telling you not to use this for anything serious, because you'd have to finish building it to even try.
 """
+build = "build.rs"
 
 [features]
 # Supports tracking channels with a non-bitcoin chain hashes. Currently enables all kinds of fun DoS attacks.
@@ -20,6 +21,9 @@ rust-crypto = "0.2"
 rand = "0.4"
 secp256k1 = "0.9"
 
+[build-dependencies]
+gcc = "0.3"
+
 [dev-dependencies.bitcoin]
 version = "0.13"
 features = ["bitcoinconsensus"]
diff --git a/build.rs b/build.rs
new file mode 100644
index 000000000..7dd340397
--- /dev/null
+++ b/build.rs
@@ -0,0 +1,10 @@
+extern crate gcc;
+
+fn main() {
+	#[cfg(not(any(target_arch = "x86", target_arch = "x86_64", target_arch = "arm")))]
+	{
+		let mut cfg = gcc::Build::new();
+		cfg.file("src/util/rust_crypto_nonstd_arch.c");
+		cfg.compile("lib_rust_crypto_nonstd_arch.a");
+	}
+}
diff --git a/fuzz/Cargo.toml b/fuzz/Cargo.toml
index 1d2e24420..9b718badf 100644
--- a/fuzz/Cargo.toml
+++ b/fuzz/Cargo.toml
@@ -3,6 +3,10 @@ name = "lightning-fuzz"
 version = "0.0.1"
 authors = ["Automatically generated"]
 publish = false
+# Because the function is unused it gets dropped before we link lightning, so
+# we have to duplicate build.rs here. Note that this is only required for
+# fuzztarget mode.
+build = "../build.rs"
 
 [package.metadata]
 cargo-fuzz = true
@@ -19,6 +23,9 @@ rust-crypto = "0.2"
 honggfuzz = { version = "0.5", optional = true }
 afl = { version = "0.3", optional = true }
 
+[build-dependencies]
+gcc = "0.3"
+
 # Prevent this from interfering with workspaces
 [workspace]
 members = ["."]
diff --git a/fuzz/src/util/rust_crypto_nonstd_arch.c b/fuzz/src/util/rust_crypto_nonstd_arch.c
new file mode 120000
index 000000000..321d648a2
--- /dev/null
+++ b/fuzz/src/util/rust_crypto_nonstd_arch.c
@@ -0,0 +1 @@
+../../../src/util/rust_crypto_nonstd_arch.c
\ No newline at end of file
diff --git a/src/util/rust_crypto_nonstd_arch.c b/src/util/rust_crypto_nonstd_arch.c
new file mode 100644
index 000000000..f50765800
--- /dev/null
+++ b/src/util/rust_crypto_nonstd_arch.c
@@ -0,0 +1,13 @@
+#include <stdint.h>
+#include <stdlib.h>
+
+uint32_t rust_crypto_util_fixed_time_eq_asm(uint8_t* lhsp, uint8_t* rhsp, size_t count) {
+	if (count == 0) {
+		return 1;
+	}
+	uint8_t result = 0;
+	for (size_t i = 0; i < count; i++) {
+		result |= (lhsp[i] ^ rhsp[i]);
+	}
+	return result;
+}
-- 
2.39.5