Add FakeSignature and FakeAggregateSignature

They replace Signature and FakeAggregateSignature when compling with
debug. Compiling with release uses the real structs.

eth2/utils/bls/src/fake_signature.rs

@@ -0,0 +1,117 @@
+use super::serde_vistors::HexVisitor;
+use super::{PublicKey, SecretKey};
+use hex::encode as hex_encode;
+use serde::de::{Deserialize, Deserializer};
+use serde::ser::{Serialize, Serializer};
+use ssz::{
+    decode_ssz_list, hash, ssz_encode, Decodable, DecodeError, Encodable, SszStream, TreeHash,
+};
+
+const SIGNATURE_LENGTH: usize = 48;
+
+/// A single BLS signature.
+///
+/// This struct is a wrapper upon a base type and provides helper functions (e.g., SSZ
+/// serialization).
+#[derive(Debug, PartialEq, Clone, Eq)]
+pub struct FakeSignature {
+    bytes: Vec<u8>,
+}
+
+impl FakeSignature {
+    /// Creates a new all-zero's signature
+    pub fn new(_msg: &[u8], _domain: u64, _sk: &SecretKey) -> Self {
+        FakeSignature::zero()
+    }
+
+    /// Creates a new all-zero's signature
+    pub fn zero() -> Self {
+        Self {
+            bytes: vec![0; SIGNATURE_LENGTH],
+        }
+    }
+
+    /// Creates a new all-zero's signature
+    pub fn new_hashed(_x_real_hashed: &[u8], _x_imaginary_hashed: &[u8], _sk: &SecretKey) -> Self {
+        FakeSignature::zero()
+    }
+
+    /// _Always_ returns `true`.
+    pub fn verify(&self, _msg: &[u8], _domain: u64, _pk: &PublicKey) -> bool {
+        true
+    }
+
+    /// _Always_ returns true.
+    pub fn verify_hashed(
+        &self,
+        _x_real_hashed: &[u8],
+        _x_imaginary_hashed: &[u8],
+        _pk: &PublicKey,
+    ) -> bool {
+        true
+    }
+
+    /// Returns a new empty signature.
+    pub fn empty_signature() -> Self {
+        FakeSignature::zero()
+    }
+}
+
+impl Encodable for FakeSignature {
+    fn ssz_append(&self, s: &mut SszStream) {
+        s.append_vec(&self.bytes);
+    }
+}
+
+impl Decodable for FakeSignature {
+    fn ssz_decode(bytes: &[u8], i: usize) -> Result<(Self, usize), DecodeError> {
+        let (sig_bytes, i) = decode_ssz_list(bytes, i)?;
+        Ok((FakeSignature { bytes: sig_bytes }, i))
+    }
+}
+
+impl TreeHash for FakeSignature {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        hash(&self.bytes)
+    }
+}
+
+impl Serialize for FakeSignature {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        serializer.serialize_str(&hex_encode(ssz_encode(self)))
+    }
+}
+
+impl<'de> Deserialize<'de> for FakeSignature {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let bytes = deserializer.deserialize_str(HexVisitor)?;
+        let (pubkey, _) = <_>::ssz_decode(&bytes[..], 0)
+            .map_err(|e| serde::de::Error::custom(format!("invalid ssz ({:?})", e)))?;
+        Ok(pubkey)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::super::Keypair;
+    use super::*;
+    use ssz::ssz_encode;
+
+    #[test]
+    pub fn test_ssz_round_trip() {
+        let keypair = Keypair::random();
+
+        let original = FakeSignature::new(&[42, 42], 0, &keypair.sk);
+
+        let bytes = ssz_encode(&original);
+        let (decoded, _) = FakeSignature::ssz_decode(&bytes, 0).unwrap();
+
+        assert_eq!(original, decoded);
+    }
+}