Merge pull request #40 from RustCrypto/ed25519/serde

ed25519: optional serde support
RustCrypto · Oct 27, 2019 · 7cb1926 · 7cb1926
2 parents 6b759c3 + 26e21c8
commit 7cb1926
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Showing 2 changed files with 75 additions and 15 deletions.
diff --git a/ed25519/Cargo.toml b/ed25519/Cargo.toml
@@ -11,5 +11,12 @@ readme        = "README.md"
 categories    = ["cryptography", "no-std"]
 keywords      = ["crypto", "curve25519", "ecc", "signature", "signing"]
 
-[dependencies]
-signature = { version = "1.0.0-pre.0", path = "../signature-crate", default-features = false }
+[dependencies.signature]
+version = "1.0.0-pre.0"
+path = "../signature-crate"
+default-features = false
+
+[dependencies.serde]
+version = "1"
+optional = true
+default-features = false
diff --git a/ed25519/src/lib.rs b/ed25519/src/lib.rs
@@ -21,6 +21,9 @@
     html_root_url = "https://docs.rs/ed25519/1.0.0-pre.0"
 )]
 
+#[cfg(feature = "serde")]
+use serde::{de, ser, Deserialize, Serialize};
+
 /// Re-export the `signature` crate
 pub use signature::{self, Error};
 
@@ -54,10 +57,25 @@ impl signature::Signature for Signature {
     }
 }
 
+impl AsRef<[u8]> for Signature {
+    fn as_ref(&self) -> &[u8] {
+        self.0.as_ref()
+    }
+}
+
+impl From<[u8; SIGNATURE_LENGTH]> for Signature {
+    fn from(bytes: [u8; SIGNATURE_LENGTH]) -> Signature {
+        Signature(bytes)
+    }
+}
+
 impl<'a> TryFrom<&'a [u8]> for Signature {
     type Error = Error;
 
     fn try_from(bytes: &'a [u8]) -> Result<Self, Error> {
+        // can't use `try_from` ourselves here because core array types only
+        // have TryFrom trait implementations for lengths 0..=32
+        // TODO(tarcieri): switch to `TryFrom` after const generics are available
         if bytes.len() == SIGNATURE_LENGTH {
             let mut arr = [0u8; SIGNATURE_LENGTH];
             arr.copy_from_slice(bytes);
@@ -68,21 +86,12 @@ impl<'a> TryFrom<&'a [u8]> for Signature {
     }
 }
 
-impl AsRef<[u8]> for Signature {
-    fn as_ref(&self) -> &[u8] {
-        self.0.as_ref()
-    }
-}
-
-impl From<[u8; SIGNATURE_LENGTH]> for Signature {
-    fn from(bytes: [u8; SIGNATURE_LENGTH]) -> Signature {
-        Signature(bytes)
-    }
-}
-
+// can't derive `Debug`, `PartialEq`, or `Eq` below because core array types
+// only have  trait implementations for lengths 0..=32
+// TODO(tarcieri): derive `PartialEq` and `Eq` after const generics are available
 impl Debug for Signature {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "Signature({:?})", &self.0[..])
+        write!(f, "ed25519::Signature({:?})", &self.0[..])
     }
 }
 
@@ -93,3 +102,47 @@ impl PartialEq for Signature {
 }
 
 impl Eq for Signature {}
+
+#[cfg(feature = "serde")]
+impl Serialize for Signature {
+    fn serialize<S: ser::Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
+        self.to_bytes().serialize(serializer)
+    }
+}
+
+// serde lacks support for deserializing arrays larger than 32-bytes
+// see: <https://github.com/serde-rs/serde/issues/631>
+#[cfg(feature = "serde")]
+impl<'de> Deserialize<'de> for Signature {
+    fn deserialize<D: de::Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
+        struct ByteArrayVisitor;
+
+        impl<'de> de::Visitor<'de> for ByteArrayVisitor {
+            type Value = [u8; SIGNATURE_LENGTH];
+
+            fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+                formatter.write_str("bytestring of length 64")
+            }
+
+            fn visit_seq<A>(self, mut seq: A) -> Result<[u8; SIGNATURE_LENGTH], A::Error>
+            where
+                A: de::SeqAccess<'de>,
+            {
+                use de::Error;
+                let mut arr = [0u8; SIGNATURE_LENGTH];
+
+                for i in 0..SIGNATURE_LENGTH {
+                    arr[i] = seq
+                        .next_element()?
+                        .ok_or_else(|| Error::invalid_length(i, &self))?;
+                }
+
+                Ok(arr)
+            }
+        }
+
+        deserializer
+            .deserialize_tuple(SIGNATURE_LENGTH, ByteArrayVisitor)
+            .map(|bytes| bytes.into())
+    }
+}