From 597c3a477090a516af5e6fc90598fe4cda53cb11 Mon Sep 17 00:00:00 2001
From: Gav Wood <gavin@ethcore.io>
Date: Tue, 13 Dec 2016 21:21:07 +0100
Subject: [PATCH] Ensure chain state is at threshold security level before
 looking for updates.

---
 ethcore/src/client/client.rs         |  2 +-
 ethcore/src/types/blockchain_info.rs | 13 +++++++++++++
 ethcore/src/types/security_level.rs  | 24 ++++++++++++++++++------
 updater/src/updater.rs               |  5 +++++
 4 files changed, 37 insertions(+), 7 deletions(-)

diff --git a/ethcore/src/client/client.rs b/ethcore/src/client/client.rs
index 55636f936..6583d77c6 100644
--- a/ethcore/src/client/client.rs
+++ b/ethcore/src/client/client.rs
@@ -1377,7 +1377,7 @@ impl BlockChainClient for Client {
 		self.registrar.lock().as_ref()
 			.and_then(|r| r.get_address(&(name.as_bytes().sha3()), "A").ok())
 			.and_then(|a| if a.is_zero() { None } else { Some(a) })
-	} 
+	}
 }
 
 impl MiningBlockChainClient for Client {
diff --git a/ethcore/src/types/blockchain_info.rs b/ethcore/src/types/blockchain_info.rs
index 6757acf64..33657ff0e 100644
--- a/ethcore/src/types/blockchain_info.rs
+++ b/ethcore/src/types/blockchain_info.rs
@@ -18,6 +18,7 @@
 
 use util::{U256, H256};
 use header::BlockNumber;
+use types::security_level::SecurityLevel;
 
 /// Information about the blockchain gathered together.
 #[derive(Clone, Debug, Binary)]
@@ -41,3 +42,15 @@ pub struct BlockChainInfo {
 	/// Number of the first block on the best sequence.
 	pub first_block_number: Option<BlockNumber>,
 }
+
+impl BlockChainInfo {
+	/// Determine the security model for the current state.
+	pub fn security_level(&self) -> SecurityLevel {
+		// TODO: Detect SecurityLevel::FullState : https://github.com/ethcore/parity/issues/3834
+		if self.ancient_block_number.is_none() || self.first_block_number.is_none() {
+			SecurityLevel::FullProofOfWork
+		} else {
+			SecurityLevel::PartialProofOfWork(self.best_block_number - self.first_block_number.expect("Guard condition means this is not none"))
+		}
+	}
+}
\ No newline at end of file
diff --git a/ethcore/src/types/security_level.rs b/ethcore/src/types/security_level.rs
index 555ddf195..0415b9bb1 100644
--- a/ethcore/src/types/security_level.rs
+++ b/ethcore/src/types/security_level.rs
@@ -16,13 +16,25 @@
 
 //! Indication of how secure the chain is.
 
+use header::BlockNumber;
+
 /// Indication of how secure the chain is.
 #[derive(Debug, PartialEq, Copy, Clone, Hash, Eq, Binary)]
 pub enum SecurityLevel {
-	/// Chain was synced through manually evaluating all transactions from genesis.
-	Full,
-	/// All blocks are known to have a valid PoW from genesis.
-	Continuous,
-	/// Some headers (the argument) are known to have a valid PoW from genesis.
-	Light(u64),
+	/// All blocks from genesis to chain head are known to have valid state transitions and PoW.
+	FullState,
+	/// All blocks from genesis to chain head are known to have a valid PoW.
+	FullProofOfWork,
+	/// Some recent headers (the argument) are known to have a valid PoW.
+	PartialProofOfWork(BlockNumber),
 }
+
+impl SecurityLevel {
+	/// `true` for `FullPoW`/`FullState`.
+	pub fn is_full(&self) -> bool {
+		match *self {
+			SecurityLevel::FullState | SecurityLevel::FullProofOfWork => true,
+			_ => false,
+		} 
+	}
+}
\ No newline at end of file
diff --git a/updater/src/updater.rs b/updater/src/updater.rs
index 050e52be2..75637f139 100644
--- a/updater/src/updater.rs
+++ b/updater/src/updater.rs
@@ -214,6 +214,11 @@ impl Updater {
 	fn poll(&self) {
 		info!(target: "updater", "Current release is {} ({:?})", self.this, self.this.hash);
 
+		// We rely on a secure state. Bail if we're unsure about it.
+		if self.client.upgrade().map_or(true, |s| !s.chain_info().security_level().is_full()) {
+			return;
+		}
+
 		if self.operations.lock().is_none() {
 			if let Some(ops_addr) = self.client.upgrade().and_then(|c| c.registry_address("operations".into())) {
 				trace!(target: "updater", "Found operations at {}", ops_addr);