Merge branch 'feature/serde' into develop

.travis.yml

@@ -7,6 +7,7 @@ rust:
 
 env:
   - TEST_COMMAND=test FEATURES=--features="yolocrypto"
+  - TEST_COMMAND=test FEATURES=--features="yolocrypto serde"
   - TEST_COMMAND=test FEATURES=--features="yolocrypto nightly"
   - TEST_COMMAND=bench FEATURES=--features="yolocrypto bench"
   - TEST_COMMAND=bench FEATURES=--features="yolocrypto nightly bench"

Cargo.toml

@@ -18,6 +18,10 @@ exclude = [
 [badges]
 travis-ci = { repository = "isislovecruft/curve25519-dalek", branch = "master"}
 
+[dependencies.serde]
+version = "1.0"
+optional = true
+
 [dependencies.arrayref]
 version = "0.3.3"
 
@@ -35,6 +39,9 @@ version = "^0.6"
 [dev-dependencies.sha2]
 version = "0.4"
 
+[dev-dependencies.serde_cbor]
+version = "0.6"
+
 [features]
 nightly = ["radix_51"]
 default = ["std"]

src/curve.rs

@@ -278,6 +278,59 @@ impl CompressedMontgomeryU {
     }
 }
 
+// ------------------------------------------------------------------------
+// Serde support
+// ------------------------------------------------------------------------
+// Serializes to and from `ExtendedPoint` directly, doing compression
+// and decompression internally.  This means that users can create
+// structs containing `ExtendedPoint`s and use Serde's derived
+// serializers to serialize those structures.
+
+#[cfg(feature = "serde")]
+use serde::{self, Serialize, Deserialize, Serializer, Deserializer};
+#[cfg(feature = "serde")]
+use serde::de::Visitor;
+
+#[cfg(feature = "serde")]
+impl Serialize for ExtendedPoint {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+        where S: Serializer
+    {
+        serializer.serialize_bytes(self.compress_edwards().as_bytes())
+    }
+}
+
+#[cfg(feature = "serde")]
+impl<'de> Deserialize<'de> for ExtendedPoint {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+        where D: Deserializer<'de>
+    {
+        struct ExtendedPointVisitor;
+
+        impl<'de> Visitor<'de> for ExtendedPointVisitor {
+            type Value = ExtendedPoint;
+
+            fn expecting(&self, formatter: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+                formatter.write_str("a valid point in Edwards y + sign format")
+            }
+
+            fn visit_bytes<E>(self, v: &[u8]) -> Result<ExtendedPoint, E>
+                where E: serde::de::Error
+            {
+                if v.len() == 32 {
+                    let arr32 = array_ref!(v,0,32); // &[u8;32] from &[u8]
+                    CompressedEdwardsY(*arr32).decompress()
+                        .ok_or(serde::de::Error::custom("decompression failed"))
+                } else {
+                    Err(serde::de::Error::invalid_length(v.len(), &self))
+                }
+            }
+        }
+
+        deserializer.deserialize_bytes(ExtendedPointVisitor)
+    }
+}
+
 // ------------------------------------------------------------------------
 // Internal point representations
 // ------------------------------------------------------------------------
@@ -1558,7 +1611,7 @@ mod test {
     mod vartime {
         use super::super::*;
         use super::{A_SCALAR, B_SCALAR, A_TIMES_BASEPOINT, DOUBLE_SCALAR_MULT_RESULT};
-        
+
         /// Test double_scalar_mult_vartime vs ed25519.py
         #[test]
         fn double_scalar_mult_basepoint_vs_ed25519py() {
@@ -1577,6 +1630,28 @@ mod test {
             assert_eq!(result.compress_edwards(), DOUBLE_SCALAR_MULT_RESULT);
         }
     }
+
+    #[cfg(feature = "serde")]
+    use serde_cbor;
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn serde_cbor_basepoint_roundtrip() {
+        let output = serde_cbor::to_vec(&constants::ED25519_BASEPOINT).unwrap();
+        let parsed: ExtendedPoint = serde_cbor::from_slice(&output).unwrap();
+        assert_eq!(parsed.compress_edwards(), constants::BASE_CMPRSSD);
+    }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn serde_cbor_decode_invalid_fails() {
+        let mut output = serde_cbor::to_vec(&constants::ED25519_BASEPOINT).unwrap();
+        // CBOR apparently has two bytes of overhead for a 32-byte string.
+        // Set the low byte of the compressed point to 1 to make it invalid.
+        output[2] = 1;
+        let parsed: Result<ExtendedPoint,_> = serde_cbor::from_slice(&output);
+        assert!(parsed.is_err());
+    }
 }
 
 // ------------------------------------------------------------------------

src/decaf.rs

@@ -116,6 +116,63 @@ impl Identity for CompressedDecaf {
     }
 }
 
+// ------------------------------------------------------------------------
+// Serde support
+// ------------------------------------------------------------------------
+// Serializes to and from `DecafPoint` directly, doing compression
+// and decompression internally.  This means that users can create
+// structs containing `DecafPoint`s and use Serde's derived
+// serializers to serialize those structures.
+
+#[cfg(feature = "serde")]
+use serde::{self, Serialize, Deserialize, Serializer, Deserializer};
+#[cfg(feature = "serde")]
+use serde::de::Visitor;
+
+#[cfg(feature = "serde")]
+impl Serialize for DecafPoint {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+        where S: Serializer
+    {
+        serializer.serialize_bytes(self.compress().as_bytes())
+    }
+}
+
+#[cfg(feature = "serde")]
+impl<'de> Deserialize<'de> for DecafPoint {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+        where D: Deserializer<'de>
+    {
+        struct DecafPointVisitor;
+
+        impl<'de> Visitor<'de> for DecafPointVisitor {
+            type Value = DecafPoint;
+
+            fn expecting(&self, formatter: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+                formatter.write_str("a valid point in Decaf format")
+            }
+
+            fn visit_bytes<E>(self, v: &[u8]) -> Result<DecafPoint, E>
+                where E: serde::de::Error
+            {
+                if v.len() == 32 {
+                    let arr32 = array_ref!(v,0,32); // &[u8;32] from &[u8]
+                    CompressedDecaf(*arr32).decompress()
+                        .ok_or(serde::de::Error::custom("decompression failed"))
+                } else {
+                    Err(serde::de::Error::invalid_length(v.len(), &self))
+                }
+            }
+        }
+
+        deserializer.deserialize_bytes(DecafPointVisitor)
+    }
+}
+
+// ------------------------------------------------------------------------
+// Internal point representations
+// ------------------------------------------------------------------------
+
 /// A point in a prime-order group.
 ///
 /// XXX think about how this API should work
@@ -523,6 +580,18 @@ mod test {
     use curve::Identity;
     use super::*;
 
+    #[cfg(feature = "serde")]
+    use serde_cbor;
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn serde_cbor_basepoint_roundtrip() {
+        let output = serde_cbor::to_vec(&constants::DECAF_ED25519_BASEPOINT).unwrap();
+        let parsed: DecafPoint = serde_cbor::from_slice(&output).unwrap();
+        assert_eq!(parsed, constants::DECAF_ED25519_BASEPOINT);
+    }
+
+
     #[test]
     fn decaf_decompress_negative_s_fails() {
         // constants::d is neg, so decompression should fail as |d| != d.

src/lib.rs

@@ -47,6 +47,11 @@ extern crate arrayref;
 extern crate generic_array;
 extern crate digest;
 
+#[cfg(feature = "serde")]
+extern crate serde;
+#[cfg(all(test, feature = "serde"))]
+extern crate serde_cbor;
+
 #[cfg(feature = "std")]
 extern crate core;
 

src/scalar.rs

@@ -185,6 +185,50 @@ impl CTAssignable for Scalar {
     }
 }
 
+#[cfg(feature = "serde")]
+use serde::{self, Serialize, Deserialize, Serializer, Deserializer};
+#[cfg(feature = "serde")]
+use serde::de::Visitor;
+
+#[cfg(feature = "serde")]
+impl Serialize for Scalar {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+        where S: Serializer
+    {
+        serializer.serialize_bytes(self.as_bytes())
+    }
+}
+
+#[cfg(feature = "serde")]
+impl<'de> Deserialize<'de> for Scalar {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+        where D: Deserializer<'de>
+    {
+        struct ScalarVisitor;
+
+        impl<'de> Visitor<'de> for ScalarVisitor {
+            type Value = Scalar;
+
+            fn expecting(&self, formatter: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+                formatter.write_str("a 32-byte scalar value")
+            }
+
+            fn visit_bytes<E>(self, v: &[u8]) -> Result<Scalar, E>
+                where E: serde::de::Error
+            {
+                if v.len() == 32 {
+                    // array_ref turns &[u8] into &[u8;32]
+                    Ok(Scalar(*array_ref!(v,0,32))) 
+                } else {
+                    Err(serde::de::Error::invalid_length(v.len(), &self))
+                }
+            }
+        }
+
+        deserializer.deserialize_bytes(ScalarVisitor)
+    }
+}
+
 impl Scalar {
     /// Return a `Scalar` chosen uniformly at random using a user-provided RNG.
     ///
@@ -827,6 +871,17 @@ mod test {
 
         assert_eq!(should_be_X, X);
     }
+
+    #[cfg(feature = "serde")]
+    use serde_cbor;
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn serde_cbor_scalar_roundtrip() {
+        let output = serde_cbor::to_vec(&X).unwrap();
+        let parsed: Scalar = serde_cbor::from_slice(&output).unwrap();
+        assert_eq!(parsed, X);
+    }
 }
 
 #[cfg(all(test, feature = "bench"))]