Merge remote-tracking branch 'manishearth/fuzz' into develop

fuzz/.gitignore

@@ -0,0 +1,4 @@
+
+target
+corpus
+artifacts

fuzz/Cargo.toml

@@ -0,0 +1,24 @@
+
+[package]
+name = "curve25519-dalek-fuzz"
+version = "0.0.1"
+authors = ["Automatically generated"]
+publish = false
+
+[package.metadata]
+cargo-fuzz = true
+
+[dependencies.curve25519-dalek]
+path = ".."
+features = ["yolocrypto"]
+
+[dependencies.libfuzzer-sys]
+git = "https://github.com/rust-fuzz/libfuzzer-sys.git"
+
+# Prevent this from interfering with workspaces
+[workspace]
+members = ["."]
+
+[[bin]]
+name = "decaf"
+path = "fuzzers/decaf.rs"

fuzz/fuzzers/decaf.rs

@@ -0,0 +1,21 @@
+#![no_main]
+#[macro_use] extern crate libfuzzer_sys;
+extern crate curve25519_dalek;
+
+use curve25519_dalek::curve::ValidityCheck;
+use curve25519_dalek::decaf::DecafPoint;
+use curve25519_dalek::field::FieldElement;
+
+fuzz_target!(|data: &[u8]| {
+    if data.len() != 32 {
+        return;
+    }
+    let mut field_bytes = [0u8; 32];
+    for (by, data) in field_bytes.iter_mut().zip(data.iter()) {
+        *by = *data;
+    }
+    let fe = FieldElement::from_bytes(&field_bytes);
+    let p = DecafPoint::elligator_decaf_flavour(&fe);
+    assert!(p.0.is_valid());
+    p.compress();
+});

src/decaf.rs

@@ -265,7 +265,7 @@ impl DecafPoint {
     ///
     /// This method is not public because it's just used for hashing
     /// to a point -- proper elligator support is deferred for now.
-    fn elligator_decaf_flavour(r_0: &FieldElement) -> DecafPoint {
+    pub fn elligator_decaf_flavour(r_0: &FieldElement) -> DecafPoint {
         // Follows Appendix C of the Decaf paper.
         // Use n = 2 as the quadratic nonresidue so that n*x = x + x.
         let minus_one = -&FieldElement::one();