Add deserialization workaround for validator updates

This introduces a (somewhat hacky, yet temporary) approach to being able
to deserialize public keys in validator updates until such time that
Tendermint addresses the problem.

Signed-off-by: Thane Thomson <connect@thanethomson.com>

tendermint/src/public_key.rs

@@ -8,20 +8,19 @@ mod pub_key_request;
 mod pub_key_response;
 pub use pub_key_request::PubKeyRequest;
 pub use pub_key_response::PubKeyResponse;
+use serde_json::Value;
 
 use crate::prelude::*;
 use crate::{error::Error, signature::Signature};
 use core::convert::TryFrom;
 use core::{cmp::Ordering, fmt, ops::Deref, str::FromStr};
-use serde::{de, ser, Deserialize, Serialize};
+use serde::{de, ser, Deserialize, Deserializer, Serialize};
+use signature::Verifier as _;
 use subtle_encoding::{base64, bech32, hex};
 use tendermint_proto::crypto::public_key::Sum;
 use tendermint_proto::crypto::PublicKey as RawPublicKey;
 use tendermint_proto::Protobuf;
 
-#[cfg(feature = "secp256k1")]
-use signature::Verifier as _;
-
 // Note:On the golang side this is generic in the sense that it could everything that implements
 // github.com/tendermint/tendermint/crypto.PubKey
 // While this is meant to be used with different key-types, it currently only uses a PubKeyEd25519
@@ -56,6 +55,69 @@ pub enum PublicKey {
     Secp256k1(Secp256k1),
 }
 
+// Internal thunk type to facilitate deserialization from the raw Protobuf data
+// structure's JSON representation.
+#[derive(Serialize, Deserialize)]
+struct ProtobufPublicKeyWrapper {
+    #[serde(rename = "Sum")]
+    sum: ProtobufPublicKey,
+}
+
+impl From<ProtobufPublicKeyWrapper> for PublicKey {
+    fn from(wrapper: ProtobufPublicKeyWrapper) -> Self {
+        match wrapper.sum {
+            ProtobufPublicKey::Ed25519 { ed25519 } => PublicKey::Ed25519(ed25519),
+            #[cfg(feature = "secp256k1")]
+            ProtobufPublicKey::Secp256k1 { secp256k1 } => PublicKey::Secp256k1(secp256k1),
+        }
+    }
+}
+
+#[derive(Serialize, Deserialize)]
+#[serde(tag = "type", content = "value")] // JSON custom serialization for priv_validator_key.json
+enum ProtobufPublicKey {
+    #[serde(rename = "tendermint.crypto.PublicKey_Ed25519")]
+    Ed25519 {
+        #[serde(
+            serialize_with = "serialize_ed25519_base64",
+            deserialize_with = "deserialize_ed25519_base64"
+        )]
+        ed25519: Ed25519,
+    },
+
+    #[cfg(feature = "secp256k1")]
+    #[serde(rename = "tendermint.crypto.PublicKey_Secp256K1")]
+    Secp256k1 {
+        #[serde(
+            serialize_with = "serialize_secp256k1_base64",
+            deserialize_with = "deserialize_secp256k1_base64"
+        )]
+        secp256k1: Secp256k1,
+    },
+}
+
+/// Custom deserialization for public keys to handle multiple potential JSON
+/// formats from Tendermint.
+///
+/// See <https://github.com/informalsystems/tendermint-rs/issues/1021> for
+/// context.
+// TODO(thane): Remove this once the serialization in Tendermint has been fixed.
+pub fn deserialize_public_key<'de, D>(deserializer: D) -> Result<PublicKey, D::Error>
+where
+    D: Deserializer<'de>,
+{
+    let v = Value::deserialize(deserializer)?;
+    if v.as_object()
+        .map(|obj| obj.contains_key("Sum"))
+        .unwrap_or(false)
+    {
+        serde_json::from_value::<ProtobufPublicKeyWrapper>(v).map(Into::into)
+    } else {
+        serde_json::from_value::<PublicKey>(v)
+    }
+    .map_err(serde::de::Error::custom)
+}
+
 impl Protobuf<RawPublicKey> for PublicKey {}
 
 impl TryFrom<RawPublicKey> for PublicKey {
@@ -326,7 +388,7 @@ impl Serialize for Algorithm {
 }
 
 impl<'de> Deserialize<'de> for Algorithm {
-    fn deserialize<D: de::Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
+    fn deserialize<D: Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
         use de::Error;
         let s = String::deserialize(deserializer)?;
         s.parse().map_err(D::Error::custom)
@@ -356,7 +418,7 @@ where
 
 fn deserialize_ed25519_base64<'de, D>(deserializer: D) -> Result<Ed25519, D::Error>
 where
-    D: de::Deserializer<'de>,
+    D: Deserializer<'de>,
 {
     use de::Error;
     let encoded = String::deserialize(deserializer)?;
@@ -367,7 +429,7 @@ where
 #[cfg(feature = "secp256k1")]
 fn deserialize_secp256k1_base64<'de, D>(deserializer: D) -> Result<Secp256k1, D::Error>
 where
-    D: de::Deserializer<'de>,
+    D: Deserializer<'de>,
 {
     use de::Error;
     let encoded = String::deserialize(deserializer)?;

tendermint/src/validator.rs

@@ -1,9 +1,9 @@
 //! Tendermint validators
 
-use serde::{de::Error as _, Deserialize, Deserializer, Serialize};
-use subtle_encoding::base64;
+use serde::{Deserialize, Serialize};
 
 use crate::prelude::*;
+use crate::public_key::deserialize_public_key;
 use crate::{account, hash::Hash, merkle, vote, Error, PublicKey, Signature};
 
 use core::convert::{TryFrom, TryInto};
@@ -326,34 +326,6 @@ pub struct Update {
     pub power: vote::Power,
 }
 
-/// Validator updates use a slightly different public key format than the one
-/// implemented in `tendermint::PublicKey`.
-///
-/// This is an internal thunk type to parse the `validator_updates` format and
-/// then convert to `tendermint::PublicKey` in `deserialize_public_key` below.
-#[derive(Serialize, Deserialize)]
-#[serde(tag = "type", content = "data")]
-enum Pk {
-    /// Ed25519 keys
-    #[serde(rename = "ed25519")]
-    Ed25519(String),
-}
-
-fn deserialize_public_key<'de, D>(deserializer: D) -> Result<PublicKey, D::Error>
-where
-    D: Deserializer<'de>,
-{
-    match &Pk::deserialize(deserializer)? {
-        Pk::Ed25519(base64_value) => {
-            let bytes =
-                base64::decode(base64_value).map_err(|e| D::Error::custom(format!("{}", e)))?;
-
-            PublicKey::from_raw_ed25519(&bytes)
-                .ok_or_else(|| D::Error::custom("error parsing Ed25519 key"))
-        }
-    }
-}
-
 #[cfg(test)]
 mod tests {
 
@@ -438,4 +410,32 @@ mod tests {
             148_151_478_422_287_875 + 158_095_448_483_785_107 + 770_561_664_770_006_272
         );
     }
+
+    #[test]
+    fn deserialize_validator_updates() {
+        const FMT1: &str = r#"{
+            "pub_key": {
+                "Sum": {
+                    "type": "tendermint.crypto.PublicKey_Ed25519",
+                    "value": {
+                        "ed25519": "VqJCr3vjQdffcLIG6RMBl2MgXDFYNY6b3Joaa43gV3o="
+                    }
+                }
+            },
+            "power": "573929"
+        }"#;
+        const FMT2: &str = r#"{
+            "pub_key": {
+                "type": "tendermint/PubKeyEd25519",
+                "value": "VqJCr3vjQdffcLIG6RMBl2MgXDFYNY6b3Joaa43gV3o="
+            },
+            "power": "573929"
+        }"#;
+
+        let update1 = serde_json::from_str::<Update>(FMT1).unwrap();
+        let update2 = serde_json::from_str::<Update>(FMT2).unwrap();
+
+        assert_eq!(u64::from(update1.power), 573929);
+        assert_eq!(update1, update2);
+    }
 }