More secure Signed implementation (#2963)

* Remove signature verification in backing.

`SignedFullStatement` now signals that the signature has already been
checked.

* Remove unused check_payload function.

* Introduced unchecked signed variants.

* Fix inclusion to use unchecked variant.

* More unchecked variants.

* Use unchecked variants in protocols.

* Start fixing statement-distribution.

* Fixup statement distribution.

* Fix inclusion.

* Fix warning.

* Fix backing properly.

* Fix bitfield distribution.

* Make crypto store optional for `RuntimeInfo`.

* Factor out utility functions.

* get_group_rotation_info

* WIP: Collator cleanup + check signatures.

* Convenience signature checking functions.

* Check signature on collator-side.

* Fix warnings.

* Fix collator side tests.

* Get rid of warnings.

* Better Signed/UncheckedSigned implementation.

Also get rid of Encode/Decode for Signed! *party*

* Get rid of dead code.

* Move Signed in its own module.

* into_checked -> try_into_checked

* Fix merge.

polkadot/node/network/collator-protocol/src/error.rs

@@ -0,0 +1,92 @@
+// Copyright 2021 Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Polkadot is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+//! Error handling related code and Error/Result definitions.
+
+use polkadot_node_primitives::UncheckedSignedFullStatement;
+use polkadot_subsystem::SubsystemError;
+use thiserror::Error;
+
+use polkadot_node_subsystem_util::{Fault, runtime, unwrap_non_fatal};
+
+use crate::LOG_TARGET;
+
+/// General result.
+pub type Result<T> = std::result::Result<T, Error>;
+
+/// Result for fatal only failures.
+pub type FatalResult<T> = std::result::Result<T, Fatal>;
+
+/// Errors for statement distribution.
+#[derive(Debug, Error)]
+#[error(transparent)]
+pub struct Error(pub Fault<NonFatal, Fatal>);
+
+impl From<NonFatal> for Error {
+	fn from(e: NonFatal) -> Self {
+		Self(Fault::from_non_fatal(e))
+	}
+}
+
+impl From<Fatal> for Error {
+	fn from(f: Fatal) -> Self {
+		Self(Fault::from_fatal(f))
+	}
+}
+
+impl From<runtime::Error> for Error {
+	fn from(o: runtime::Error) -> Self {
+		Self(Fault::from_other(o))
+	}
+}
+
+/// Fatal runtime errors.
+#[derive(Debug, Error)]
+pub enum Fatal {
+	/// Receiving subsystem message from overseer failed.
+	#[error("Receiving message from overseer failed")]
+	SubsystemReceive(#[source] SubsystemError),
+
+	/// Errors coming from runtime::Runtime.
+	#[error("Error while accessing runtime information")]
+	Runtime(#[from] #[source] runtime::Fatal),
+}
+
+/// Errors for fetching of runtime information.
+#[derive(Debug, Error)]
+pub enum NonFatal {
+	/// Signature was invalid on received statement.
+	#[error("CollationSeconded contained statement with invalid signature.")]
+	InvalidStatementSignature(UncheckedSignedFullStatement),
+
+	/// Errors coming from runtime::Runtime.
+	#[error("Error while accessing runtime information")]
+	Runtime(#[from] #[source] runtime::NonFatal),
+}
+
+/// Utility for eating top level errors and log them.
+///
+/// We basically always want to try and continue on error. This utility function is meant to
+/// consume top-level errors by simply logging them.
+pub fn log_error(result: Result<()>, ctx: &'static str)
+	-> FatalResult<()>
+{
+	if let Some(error) = unwrap_non_fatal(result.map_err(|e| e.0))? {
+		tracing::warn!(target: LOG_TARGET, error = ?error, ctx)
+	}
+	Ok(())
+}