fixed #2263, geth keys with ciphertext shorter than 32 bytes (#2318)

* fixed #2263, geth keys with ciphertext shorter than 32 bytes

* replace unwrap with more helpful expect

* tests for decrypting short secrets

ethstore/src/json/bytes.rs

@@ -0,0 +1,58 @@
+use std::{ops, str};
+use serde::{Deserialize, Deserializer, Error, Serialize, Serializer};
+use rustc_serialize::hex::{ToHex, FromHex, FromHexError};
+
+#[derive(Debug, PartialEq)]
+pub struct Bytes(Vec<u8>);
+
+impl ops::Deref for Bytes {
+	type Target = [u8];
+
+	fn deref(&self) -> &Self::Target {
+		&self.0
+	}
+}
+
+impl Deserialize for Bytes {
+	fn deserialize<D>(deserializer: &mut D) -> Result<Self, D::Error>
+		where D: Deserializer
+	{
+		let s = try!(String::deserialize(deserializer));
+		let data = try!(s.from_hex().map_err(|e| Error::custom(format!("Invalid hex value {}", e))));
+		Ok(Bytes(data))
+	}
+}
+
+impl Serialize for Bytes {
+	fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+	where S: Serializer {
+		serializer.serialize_str(&self.0.to_hex())
+	}
+}
+
+impl str::FromStr for Bytes {
+	type Err = FromHexError;
+
+	fn from_str(s: &str) -> Result<Self, Self::Err> {
+		s.from_hex().map(Bytes)
+	}
+}
+
+impl From<&'static str> for Bytes {
+	fn from(s: &'static str) -> Self {
+		s.parse().expect(&format!("invalid string literal for {}: '{}'", stringify!(Self), s))
+	}
+}
+
+impl From<Vec<u8>> for Bytes {
+	fn from(v: Vec<u8>) -> Self {
+		Bytes(v)
+	}
+}
+
+impl From<Bytes> for Vec<u8> {
+	fn from(b: Bytes) -> Self {
+		b.0
+	}
+}
+