Submit (& sign) extrinsics from the runtime. (#3514)

* Abstract constructing extrinsic and signing.

* Initial impl of signer.

* Implement get payload.

* Clean up the code.

* Improve docs.

* Bump version.

* Update core/sr-primitives/src/generic/unchecked_extrinsic.rs

Co-Authored-By: Bastian Köcher <bkchr@users.noreply.github.com>

* Fix tests & address grumbles.

* Fix build.

* Fix runtime tests.

* Fix bound test.

* Fix bound test.

substrate/core/sr-primitives/src/generic/mod.rs

@@ -27,7 +27,7 @@ mod digest;
 #[cfg(test)]
 mod tests;
 
-pub use self::unchecked_extrinsic::UncheckedExtrinsic;
+pub use self::unchecked_extrinsic::{UncheckedExtrinsic, SignedPayload};
 pub use self::era::{Era, Phase};
 pub use self::checked_extrinsic::CheckedExtrinsic;
 pub use self::header::Header;

substrate/core/sr-primitives/src/generic/unchecked_extrinsic.rs

@@ -72,12 +72,22 @@ impl<Address, Call, Signature, Extra: SignedExtension> Extrinsic
 {
 	type Call = Call;
 
+	type SignaturePayload = (
+		Address,
+		Signature,
+		Extra,
+	);
+
 	fn is_signed(&self) -> Option<bool> {
 		Some(self.signature.is_some())
 	}
 
-	fn new_unsigned(function: Call) -> Option<Self> {
-		Some(UncheckedExtrinsic::new_unsigned(function))
+	fn new(function: Call, signed_data: Option<Self::SignaturePayload>) -> Option<Self> {
+		Some(if let Some((address, signature, extra)) = signed_data {
+			UncheckedExtrinsic::new_signed(function, address, signature, extra)
+		} else {
+			UncheckedExtrinsic::new_unsigned(function)
+		})
 	}
 }
 
@@ -98,21 +108,18 @@ where
 	fn check(self, lookup: &Lookup) -> Result<Self::Checked, &'static str> {
 		Ok(match self.signature {
 			Some((signed, signature, extra)) => {
-				let additional_signed = extra.additional_signed()?;
-				let raw_payload = (self.function, extra, additional_signed);
 				let signed = lookup.lookup(signed)?;
+				let raw_payload = SignedPayload::new(self.function, extra)?;
 				if !raw_payload.using_encoded(|payload| {
-					if payload.len() > 256 {
-						signature.verify(&blake2_256(payload)[..], &signed)
-					} else {
-						signature.verify(payload, &signed)
-					}
+					signature.verify(payload, &signed)
 				}) {
 					return Err(crate::BAD_SIGNATURE)
 				}
+
+				let (function, extra, _) = raw_payload.deconstruct();
 				CheckedExtrinsic {
-					signed: Some((signed, raw_payload.1)),
-					function: raw_payload.0,
+					signed: Some((signed, extra)),
+					function,
 				}
 			}
 			None => CheckedExtrinsic {
@@ -123,6 +130,59 @@ where
 	}
 }
 
+/// A payload that has been signed for an unchecked extrinsics.
+///
+/// Note that the payload that we sign to produce unchecked extrinsic signature
+/// is going to be different than the `SignaturePayload` - so the thing the extrinsic
+/// actually contains.
+pub struct SignedPayload<Call, Extra: SignedExtension>((
+		Call,
+		Extra,
+		Extra::AdditionalSigned,
+));
+
+impl<Call, Extra> SignedPayload<Call, Extra> where
+	Call: Encode,
+	Extra: SignedExtension,
+{
+	/// Create new `SignedPayload`.
+	///
+	/// This function may fail if `additional_signed` of `Extra` is not available.
+	pub fn new(call: Call, extra: Extra) -> Result<Self, &'static str> {
+		let additional_signed = extra.additional_signed()?;
+		let raw_payload = (call, extra, additional_signed);
+		Ok(Self(raw_payload))
+	}
+
+	/// Create new `SignedPayload` from raw components.
+	pub fn from_raw(call: Call, extra: Extra, additional_signed: Extra::AdditionalSigned) -> Self {
+		Self((call, extra, additional_signed))
+	}
+
+	/// Deconstruct the payload into it's components.
+	pub fn deconstruct(self) -> (Call, Extra, Extra::AdditionalSigned) {
+		self.0
+	}
+}
+
+impl<Call, Extra> Encode for SignedPayload<Call, Extra> where
+	Call: Encode,
+	Extra: SignedExtension,
+{
+	/// Get an encoded version of this payload.
+	///
+	/// Payloads longer than 256 bytes are going to be `blake2_256`-hashed.
+	fn using_encoded<R, F: FnOnce(&[u8]) -> R>(&self, f: F) -> R {
+		self.0.using_encoded(|payload| {
+			if payload.len() > 256 {
+				f(&blake2_256(payload)[..])
+			} else {
+				f(payload)
+			}
+		})
+	}
+}
+
 impl<Address, Call, Signature, Extra> Decode
 	for UncheckedExtrinsic<Address, Call, Signature, Extra>
 where