Decoding headers can fail (#8570)

* rlp::decode returns Result

* Fix journaldb to handle rlp::decode Result

* Fix ethcore to work with rlp::decode returning Result

* Light client handles rlp::decode returning Result

* Fix tests in rlp_derive

* Fix tests

* Cleanup

* cleanup

* Allow panic rather than breaking out of iterator

* Let decoding failures when reading from disk blow up

* syntax

* Fix the trivial grumbles

* Fix failing tests

* Make Account::from_rlp return Result

* Syntx, sigh

* Temp-fix for decoding failures

* Header::decode returns Result

Handle new return type throughout the code base.

* Do not continue reading from the DB when a value could not be read

* Fix tests

* Handle header decoding in light_sync

* Handling header decoding errors

* Let the DecodeError bubble up unchanged

* Remove redundant error conversion

ethcore/src/client/client.rs

@@ -1219,8 +1219,7 @@ impl Client {
 				=> Some(self.chain.read().best_block_header()),
 			BlockId::Number(number) if number == self.chain.read().best_block_number()
 				=> Some(self.chain.read().best_block_header()),
-			_
-				=> self.block_header(id).map(|h| h.decode()),
+			_   => self.block_header(id).and_then(|h| h.decode().ok())
 		}
 	}
 }
@@ -1915,7 +1914,11 @@ impl BlockChainClient for Client {
 
 	fn uncle_extra_info(&self, id: UncleId) -> Option<BTreeMap<String, String>> {
 		self.uncle(id)
-			.map(|header| self.engine.extra_info(&header.decode()))
+			.and_then(|h| {
+				h.decode().map(|dh| {
+					self.engine.extra_info(&dh)
+				}).ok()
+			})
 	}
 
 	fn pruning_info(&self) -> PruningInfo {
@@ -2033,7 +2036,8 @@ impl ReopenBlock for Client {
 			for h in uncles {
 				if !block.uncles().iter().any(|header| header.hash() == h) {
 					let uncle = chain.block_header_data(&h).expect("find_uncle_hashes only returns hashes for existing headers; qed");
-					block.push_uncle(uncle.decode()).expect("pushing up to maximum_uncle_count;
+					let uncle = uncle.decode().expect("decoding failure");
+					block.push_uncle(uncle).expect("pushing up to maximum_uncle_count;
 												push_uncle is not ok only if more than maximum_uncle_count is pushed;
 												so all push_uncle are Ok;
 												qed");
@@ -2074,7 +2078,7 @@ impl PrepareOpenBlock for Client {
 			.into_iter()
 			.take(engine.maximum_uncle_count(open_block.header().number()))
 			.foreach(|h| {
-				open_block.push_uncle(h.decode()).expect("pushing maximum_uncle_count;
+				open_block.push_uncle(h.decode().expect("decoding failure")).expect("pushing maximum_uncle_count;
 												open_block was just created;
 												push_uncle is not ok only if more than maximum_uncle_count is pushed;
 												so all push_uncle are Ok;

ethcore/src/client/test_client.rs

@@ -289,7 +289,7 @@ impl TestBlockChainClient {
 	/// Make a bad block by setting invalid extra data.
 	pub fn corrupt_block(&self, n: BlockNumber) {
 		let hash = self.block_hash(BlockId::Number(n)).unwrap();
-		let mut header: BlockHeader = self.block_header(BlockId::Number(n)).unwrap().decode();
+		let mut header: BlockHeader = self.block_header(BlockId::Number(n)).unwrap().decode().expect("decoding failed");
 		header.set_extra_data(b"This extra data is way too long to be considered valid".to_vec());
 		let mut rlp = RlpStream::new_list(3);
 		rlp.append(&header);
@@ -301,7 +301,7 @@ impl TestBlockChainClient {
 	/// Make a bad block by setting invalid parent hash.
 	pub fn corrupt_block_parent(&self, n: BlockNumber) {
 		let hash = self.block_hash(BlockId::Number(n)).unwrap();
-		let mut header: BlockHeader = self.block_header(BlockId::Number(n)).unwrap().decode();
+		let mut header: BlockHeader = self.block_header(BlockId::Number(n)).unwrap().decode().expect("decoding failed");
 		header.set_parent_hash(H256::from(42));
 		let mut rlp = RlpStream::new_list(3);
 		rlp.append(&header);
@@ -479,6 +479,7 @@ impl BlockInfo for TestBlockChainClient {
 		self.block_header(BlockId::Hash(self.chain_info().best_block_hash))
 			.expect("Best block always has header.")
 			.decode()
+			.expect("decoding failed")
 	}
 
 	fn block(&self, id: BlockId) -> Option<encoded::Block> {

ethcore/src/encoded.rs

@@ -28,7 +28,7 @@ use ethereum_types::{H256, Bloom, U256, Address};
 use hash::keccak;
 use header::{BlockNumber, Header as FullHeader};
 use heapsize::HeapSizeOf;
-use rlp::{Rlp, RlpStream};
+use rlp::{self, Rlp, RlpStream};
 use transaction::UnverifiedTransaction;
 use views::{self, BlockView, HeaderView, BodyView};
 
@@ -47,7 +47,9 @@ impl Header {
 	pub fn new(encoded: Vec<u8>) -> Self { Header(encoded) }
 
 	/// Upgrade this encoded view to a fully owned `Header` object.
-	pub fn decode(&self) -> FullHeader { ::rlp::decode(&self.0).expect("decoding failure") }
+	pub fn decode(&self) -> Result<FullHeader, rlp::DecoderError> {
+		rlp::decode(&self.0)
+	}
 
 	/// Get a borrowed header view onto the data.
 	#[inline]

ethcore/src/engines/authority_round/mod.rs

@@ -996,7 +996,7 @@ impl Engine<EthereumMachine> for AuthorityRound {
 
 				let parent = client.block_header(::client::BlockId::Hash(*block.header().parent_hash()))
 					.expect("hash is from parent; parent header must exist; qed")
-					.decode();
+					.decode()?;
 
 				let parent_step = header_step(&parent, self.empty_steps_transition)?;
 				let current_step = self.step.load();

ethcore/src/error.rs

@@ -290,6 +290,12 @@ error_chain! {
 			description("Unknown engine name")
 			display("Unknown engine name ({})", name)
 		}
+
+		#[doc = "RLP decoding errors"]
+		Decoder(err: ::rlp::DecoderError) {
+			description("decoding value failed")
+			display("decoding value failed with error: {}", err)
+		}
 	}
 }
 
@@ -310,11 +316,11 @@ impl From<AccountsError> for Error {
 	fn from(err: AccountsError) -> Error { 
 		ErrorKind::AccountProvider(err).into()
 	} 
-} 
+}
 
 impl From<::rlp::DecoderError> for Error {
 	fn from(err: ::rlp::DecoderError) -> Error {
-		UtilError::from(err).into()
+		ErrorKind::Decoder(err).into()
 	}
 }
 

ethcore/src/miner/miner.rs

@@ -528,8 +528,8 @@ impl Miner {
 	}
 
 	/// Attempts to perform internal sealing (one that does not require work) and handles the result depending on the type of Seal.
-	fn seal_and_import_block_internally<C>(&self, chain: &C, block: ClosedBlock) -> bool where
-		C: BlockChain + SealedBlockImporter,
+	fn seal_and_import_block_internally<C>(&self, chain: &C, block: ClosedBlock) -> bool
+		where C: BlockChain + SealedBlockImporter,
 	{
 		{
 			let sealing = self.sealing.lock();
@@ -544,7 +544,12 @@ impl Miner {
 		trace!(target: "miner", "seal_block_internally: attempting internal seal.");
 
 		let parent_header = match chain.block_header(BlockId::Hash(*block.header().parent_hash())) {
-			Some(hdr) => hdr.decode(),
+			Some(h) => {
+				match h.decode() {
+					Ok(decoded_hdr) => decoded_hdr,
+					Err(_) => return false
+				}
+			}
 			None => return false,
 		};
 

ethcore/src/snapshot/mod.rs

@@ -487,7 +487,7 @@ pub fn verify_old_block(rng: &mut OsRng, header: &Header, engine: &EthEngine, ch
 	if always || rng.gen::<f32>() <= POW_VERIFY_RATE {
 		engine.verify_block_unordered(header)?;
 		match chain.block_header_data(header.parent_hash()) {
-			Some(parent) => engine.verify_block_family(header, &parent.decode()),
+			Some(parent) => engine.verify_block_family(header, &parent.decode()?),
 			None => Ok(()),
 		}
 	} else {

ethcore/src/verification/verification.rs

@@ -224,7 +224,7 @@ fn verify_uncles(header: &Header, bytes: &[u8], bc: &BlockProvider, engine: &Eth
 				return Err(From::from(BlockError::UncleParentNotInChain(uncle_parent.hash())));
 			}
 
-			let uncle_parent = uncle_parent.decode();
+			let uncle_parent = uncle_parent.decode()?;
 			verify_parent(&uncle, &uncle_parent, engine)?;
 			engine.verify_block_family(&uncle, &uncle_parent)?;
 			verified.insert(uncle.hash());
@@ -500,10 +500,9 @@ mod tests {
 		// no existing tests need access to test, so having this not function
 		// is fine.
 		let client = ::client::TestBlockChainClient::default();
-
 		let parent = bc.block_header_data(header.parent_hash())
 			.ok_or(BlockError::UnknownParent(header.parent_hash().clone()))?
-			.decode();
+			.decode()?;
 
 		let full_params = FullFamilyParams {
 			block_bytes: bytes,