Introduces author_hasKey and author_hasSessionKeys rpc endpoints (#4720)

* Introduces `author_hasKey` and `author_hasSessionKeys` rpc endpoints

Both endpoints can be used to check if a key is present in the keystore.

- `hasKey` works on with an individual public key and key type. It
checks if a private key for the given combination exists in the
keystore.
- `hasSessionKeys` works with the full encoded session key blob stored
on-chain in `nextKeys`. This requires that the given blob can be decoded
by the runtime. It will return `true`, iff all public keys of the
session key exist in the storage.

Fixes: https://github.com/paritytech/substrate/issues/4696

* Update client/rpc-api/src/author/error.rs

Co-Authored-By: Nikolay Volf <nikvolf@gmail.com>

* Indentation

Co-authored-by: Nikolay Volf <nikvolf@gmail.com>

substrate/client/keystore/src/lib.rs

@@ -72,7 +72,8 @@ impl std::error::Error for Error {
 /// Every pair that is being generated by a `seed`, will be placed in memory.
 pub struct Store {
 	path: Option<PathBuf>,
-	additional: HashMap<(KeyTypeId, Vec<u8>), Vec<u8>>,
+	/// Map over `(KeyTypeId, Raw public key)` -> `Key phrase/seed`
+	additional: HashMap<(KeyTypeId, Vec<u8>), String>,
 	password: Option<Protected<String>>,
 }
 
@@ -97,25 +98,22 @@ impl Store {
 		}))
 	}
 
-	/// Get the public/private key pair for the given public key and key type.
-	fn get_additional_pair<Pair: PairT>(
+	/// Get the key phrase for the given public key and key type from the in-memory store.
+	fn get_additional_pair(
 		&self,
-		public: &Pair::Public,
+		public: &[u8],
 		key_type: KeyTypeId,
-	) -> Result<Option<Pair>> {
-		let key = (key_type, public.to_raw_vec());
-		self.additional
-			.get(&key)
-			.map(|bytes| Pair::from_seed_slice(bytes).map_err(|_| Error::InvalidSeed))
-			.transpose()
+	) -> Option<&String> {
+		let key = (key_type, public.to_vec());
+		self.additional.get(&key)
 	}
 
 	/// Insert the given public/private key pair with the given key type.
 	///
 	/// Does not place it into the file system store.
-	fn insert_ephemeral_pair<Pair: PairT>(&mut self, pair: &Pair, key_type: KeyTypeId) {
+	fn insert_ephemeral_pair<Pair: PairT>(&mut self, pair: &Pair, seed: &str, key_type: KeyTypeId) {
 		let key = (key_type, pair.public().to_raw_vec());
-		self.additional.insert(key, pair.to_raw_vec());
+		self.additional.insert(key, seed.into());
 	}
 
 	/// Insert a new key with anonymous crypto.
@@ -179,7 +177,7 @@ impl Store {
 		key_type: KeyTypeId,
 	) -> Result<Pair> {
 		let pair = Pair::from_string(seed, None).map_err(|_| Error::InvalidSeed)?;
-		self.insert_ephemeral_pair(&pair, key_type);
+		self.insert_ephemeral_pair(&pair, seed, key_type);
 		Ok(pair)
 	}
 
@@ -190,20 +188,24 @@ impl Store {
 		self.insert_ephemeral_from_seed_by_type::<Pair::Generic>(seed, Pair::ID).map(Into::into)
 	}
 
+	/// Get the key phrase for a given public key and key type.
+	fn key_phrase_by_type(&self, public: &[u8], key_type: KeyTypeId) -> Result<String> {
+		if let Some(phrase) = self.get_additional_pair(public, key_type) {
+			return Ok(phrase.clone())
+		}
+
+		let path = self.key_file_path(public, key_type).ok_or_else(|| Error::Unavailable)?;
+		let file = File::open(path)?;
+
+		serde_json::from_reader(&file).map_err(Into::into)
+	}
+
 	/// Get a key pair for the given public key and key type.
 	pub fn key_pair_by_type<Pair: PairT>(&self,
 		public: &Pair::Public,
 		key_type: KeyTypeId,
 	) -> Result<Pair> {
-		if let Some(pair) = self.get_additional_pair(public, key_type)? {
-			return Ok(pair)
-		}
-
-		let path = self.key_file_path(public.as_slice(), key_type)
-			.ok_or_else(|| Error::Unavailable)?;
-		let file = File::open(path)?;
-
-		let phrase: String = serde_json::from_reader(&file)?;
+		let phrase = self.key_phrase_by_type(public.as_slice(), key_type)?;
 		let pair = Pair::from_string(
 			&phrase,
 			self.password.as_ref().map(|p| &***p),
@@ -328,6 +330,10 @@ impl BareCryptoStore for Store {
 	fn password(&self) -> Option<&str> {
 		self.password.as_ref().map(|x| x.as_str())
 	}
+
+	fn has_keys(&self, public_keys: &[(Vec<u8>, KeyTypeId)]) -> bool {
+		public_keys.iter().all(|(p, t)| self.key_phrase_by_type(&p, *t).is_ok())
+	}
 }
 
 #[cfg(test)]

substrate/client/rpc-api/src/author/error.rs

@@ -54,6 +54,9 @@ pub enum Error {
 	/// Some random issue with the key store. Shouldn't happen.
 	#[display(fmt="The key store is unavailable")]
 	KeyStoreUnavailable,
+	/// Invalid session keys encoding.
+	#[display(fmt="Session keys are not encoded correctly")]
+	InvalidSessionKeys,
 }
 
 impl std::error::Error for Error {

substrate/client/rpc-api/src/author/mod.rs

@@ -39,7 +39,8 @@ pub trait AuthorApi<Hash, BlockHash> {
 
 	/// Insert a key into the keystore.
 	#[rpc(name = "author_insertKey")]
-	fn insert_key(&self,
+	fn insert_key(
+		&self,
 		key_type: String,
 		suri: String,
 		public: Bytes,
@@ -49,6 +50,20 @@ pub trait AuthorApi<Hash, BlockHash> {
 	#[rpc(name = "author_rotateKeys")]
 	fn rotate_keys(&self) -> Result<Bytes>;
 
+	/// Checks if the keystore has private keys for the given session public keys.
+	///
+	/// `session_keys` is the SCALE encoded session keys object from the runtime.
+	///
+	/// Returns `true` iff all private keys could be found.
+	#[rpc(name = "author_hasSessionKeys")]
+	fn has_session_keys(&self, session_keys: Bytes) -> Result<bool>;
+
+	/// Checks if the keystore has private keys for the given public key and key type.
+	///
+	/// Returns `true` if a private key could be found.
+	#[rpc(name = "author_hasKey")]
+	fn has_key(&self, public_key: Bytes, key_type: String) -> Result<bool>;
+
 	/// Returns all pending extrinsics, potentially grouped by sender.
 	#[rpc(name = "author_pendingExtrinsics")]
 	fn pending_extrinsics(&self) -> Result<Vec<Bytes>>;

substrate/client/rpc/src/author/mod.rs

@@ -112,6 +112,22 @@ where
 		).map(Into::into).map_err(|e| Error::Client(Box::new(e)))
 	}
 
+	fn has_session_keys(&self, session_keys: Bytes) -> Result<bool> {
+		let best_block_hash = self.client.chain_info().best_hash;
+		let keys = self.client.runtime_api().decode_session_keys(
+			&generic::BlockId::Hash(best_block_hash),
+			session_keys.to_vec(),
+		).map_err(|e| Error::Client(Box::new(e)))?
+			.ok_or_else(|| Error::InvalidSessionKeys)?;
+
+		Ok(self.keystore.read().has_keys(&keys))
+	}
+
+	fn has_key(&self, public_key: Bytes, key_type: String) -> Result<bool> {
+		let key_type = key_type.as_str().try_into().map_err(|_| Error::BadKeyType)?;
+		Ok(self.keystore.read().has_keys(&[(public_key.to_vec(), key_type)]))
+	}
+
 	fn submit_extrinsic(&self, ext: Bytes) -> FutureResult<TxHash<P>> {
 		let xt = match Decode::decode(&mut &ext[..]) {
 			Ok(xt) => xt,

substrate/client/rpc/src/author/tests.rs

@@ -16,12 +16,12 @@
 
 use super::*;
 
-use std::sync::Arc;
+use std::{mem, sync::Arc};
 use assert_matches::assert_matches;
 use codec::Encode;
 use sp_core::{
-	H256, blake2_256, hexdisplay::HexDisplay, testing::{ED25519, SR25519, KeyStore}, traits::BareCryptoStorePtr, ed25519,
-	crypto::Pair,
+	H256, blake2_256, hexdisplay::HexDisplay, testing::{ED25519, SR25519, KeyStore},
+	traits::BareCryptoStorePtr, ed25519, crypto::{Pair, Public},
 };
 use rpc::futures::Stream as _;
 use substrate_test_runtime_client::{
@@ -237,3 +237,59 @@ fn should_rotate_keys() {
 	assert_eq!(session_keys.ed25519, ed25519_key_pair.public().into());
 	assert_eq!(session_keys.sr25519, sr25519_key_pair.public().into());
 }
+
+#[test]
+fn test_has_session_keys() {
+	let setup = TestSetup::default();
+	let p = setup.author();
+
+	let non_existent_public_keys = TestSetup::default()
+		.author()
+		.rotate_keys()
+		.expect("Rotates the keys");
+
+	let public_keys = p.rotate_keys().expect("Rotates the keys");
+	let test_vectors = vec![
+		(public_keys, Ok(true)),
+		(vec![1, 2, 3].into(), Err(Error::InvalidSessionKeys)),
+		(non_existent_public_keys, Ok(false)),
+	];
+
+	for (keys, result) in test_vectors {
+		assert_eq!(
+			result.map_err(|e| mem::discriminant(&e)),
+			p.has_session_keys(keys).map_err(|e| mem::discriminant(&e)),
+		);
+	}
+}
+
+#[test]
+fn test_has_key() {
+	let setup = TestSetup::default();
+	let p = setup.author();
+
+	let suri = "//Alice";
+	let alice_key_pair = ed25519::Pair::from_string(suri, None).expect("Generates keypair");
+	p.insert_key(
+		String::from_utf8(ED25519.0.to_vec()).expect("Keytype is a valid string"),
+		suri.to_string(),
+		alice_key_pair.public().0.to_vec().into(),
+	).expect("Insert key");
+	let bob_key_pair = ed25519::Pair::from_string("//Bob", None).expect("Generates keypair");
+
+	let test_vectors = vec![
+		(alice_key_pair.public().to_raw_vec().into(), ED25519, Ok(true)),
+		(alice_key_pair.public().to_raw_vec().into(), SR25519, Ok(false)),
+		(bob_key_pair.public().to_raw_vec().into(), ED25519, Ok(false)),
+	];
+
+	for (key, key_type, result) in test_vectors {
+		assert_eq!(
+			result.map_err(|e| mem::discriminant(&e)),
+			p.has_key(
+				key,
+				String::from_utf8(key_type.0.to_vec()).expect("Keytype is a valid string"),
+			).map_err(|e| mem::discriminant(&e)),
+		);
+	}
+}