Expose proof generation and verifying api.

primitives/trie/Cargo.toml

@@ -15,9 +15,9 @@ harness = false
 codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false }
 sp-std = { version = "2.0.0", default-features = false, path = "../std" }
 hash-db = { version = "0.15.2", default-features = false }
-trie-db = { version = "0.18.1", default-features = false }
+trie-db = { version = "0.19.2", default-features = false }
 trie-root = { version = "0.15.2", default-features = false }
-memory-db = { version = "0.18.0", default-features = false }
+memory-db = { version = "0.18.1", default-features = false }
 sp-core = { version = "2.0.0", default-features = false, path = "../core" }
 
 [dev-dependencies]

primitives/trie/src/lib.rs

@@ -1,5 +1,3 @@
-// Copyright 2015-2020 Parity Technologies (UK) Ltd.
-// This file is part of Substrate.
 
 // Parity is free software: you can redistribute it and/or modify
 // it under the terms of the GNU General Public License as published by
@@ -27,6 +25,8 @@ use sp_std::boxed::Box;
 use sp_std::marker::PhantomData;
 use sp_std::vec::Vec;
 use hash_db::{Hasher, Prefix};
+use trie_db::proof::{generate_proof, verify_proof};
+pub use trie_db::proof::VerifyError;
 /// Our `NodeCodec`-specific error.
 pub use error::Error;
 /// The Substrate format implementation of `TrieStream`.
@@ -119,6 +119,51 @@ pub mod trie_types {
 	pub type TrieError<H> = trie_db::TrieError<H, super::Error>;
 }
 
+/// Create a proof for a subset of keys in a trie.
+///
+/// The `keys` may contain any set of keys regardless of each one of them is included
+/// into the `db`.
+///
+/// For a key `K` that is included into the `db` a proof of inclusion is generated.
+/// For a key `K` that is not included into the `db` a proof of non-inclusion is generated.
+/// These can be later checked in [`verify_trie_proof`].
+///
+/// [`verify_trie_proof`]: ./fn.verify_trie_proof.html
+pub fn generate_trie_proof<'a, L: TrieConfiguration, I, K, DB>(
+    db: &DB,
+    root: TrieHash<L>,
+    keys: I
+) -> Result<Vec<Vec<u8>>, Box<TrieError<L>>> where
+    I: IntoIterator<Item=&'a K>,
+    K: 'a + AsRef<[u8]>,
+    DB: hash_db::HashDBRef<L::Hash, trie_db::DBValue>,
+{
+    let trie = TrieDB::<L>::new(db, &root)?;
+    generate_proof(&trie, keys)
+}
+
+/// Verify a set of key-value pairs against a trie root and a proof.
+///
+/// Checks a set of keys with optional values for inclusion into the proof that was generated by
+/// [`generate_trie_proof`].
+/// If the value in the pair is supplied (`(key, Some(value))`), this key-value pair will be
+/// checked for inclusion into the proof.
+/// If the value is omitted (`(key, None)`), this key will be checked for non-inclusion into the
+/// proof.
+///
+/// [`generate_trie_proof`]: ./fn.generate_trie_proof.html
+pub fn verify_trie_proof<'a, L: TrieConfiguration, I, K, V>(
+    root: &TrieHash<L>,
+    proof: &[Vec<u8>],
+    items: I,
+) -> Result<(), VerifyError<TrieHash<L>, error::Error>> where
+    I: IntoIterator<Item=&'a (K, Option<V>)>,
+    K: 'a + AsRef<[u8]>,
+    V: 'a + AsRef<[u8]>,
+{
+    verify_proof::<Layout<L::Hash>, _, _, _>(root, proof, items)
+}
+
 /// Determine a trie root given a hash DB and delta values.
 pub fn delta_trie_root<L: TrieConfiguration, I, A, B, DB>(
 	db: &mut DB,
@@ -727,4 +772,89 @@ mod tests {
 
 		assert_eq!(pairs, iter_pairs);
 	}
+
+    #[test]
+    fn proof_non_inclusion_works() {
+        let pairs = vec![
+            (hex!("0102").to_vec(), hex!("01").to_vec()),
+            (hex!("0203").to_vec(), hex!("0405").to_vec()),
+        ];
+
+        let mut memdb = MemoryDB::default();
+        let mut root = Default::default();
+        populate_trie::<Layout>(&mut memdb, &mut root, &pairs);
+
+        let non_included_key: Vec<u8> = hex!("0909").to_vec();
+        let proof = generate_trie_proof::<Layout, _, _, _>(
+            &memdb,
+            root,
+            &[non_included_key.clone()]
+        ).unwrap();
+
+        // Verifying that the K was not included into the trie should work.
+        assert!(verify_trie_proof::<Layout, _, _, Vec<u8>>(
+                &root,
+                &proof,
+                &[(non_included_key.clone(), None)],
+            ).is_ok()
+        );
+
+        // Verifying that the K was included into the trie should fail.
+        assert!(verify_trie_proof::<Layout, _, _, Vec<u8>>(
+                &root,
+                &proof,
+                &[(non_included_key, Some(hex!("1010").to_vec()))],
+            ).is_err()
+        );
+    }
+
+    #[test]
+    fn proof_inclusion_works() {
+        let pairs = vec![
+            (hex!("0102").to_vec(), hex!("01").to_vec()),
+            (hex!("0203").to_vec(), hex!("0405").to_vec()),
+        ];
+
+        let mut memdb = MemoryDB::default();
+        let mut root = Default::default();
+        populate_trie::<Layout>(&mut memdb, &mut root, &pairs);
+
+        let proof = generate_trie_proof::<Layout, _, _, _>(
+            &memdb,
+            root,
+            &[pairs[0].0.clone()]
+        ).unwrap();
+
+        // Check that a K, V included into the proof are verified.
+        assert!(verify_trie_proof::<Layout, _, _, _>(
+                &root,
+                &proof,
+                &[(pairs[0].0.clone(), Some(pairs[0].1.clone()))]
+            ).is_ok()
+        );
+
+        // Absence of the V is not verified with the proof that has K, V included.
+        assert!(verify_trie_proof::<Layout, _, _, Vec<u8>>(
+                &root,
+                &proof,
+                &[(pairs[0].0.clone(), None)]
+            ).is_err()
+        );
+
+        // K not included into the trie is not verified.
+        assert!(verify_trie_proof::<Layout, _, _, _>(
+                &root,
+                &proof,
+                &[(hex!("4242").to_vec(), Some(pairs[0].1.clone()))]
+            ).is_err()
+        );
+
+        // K included into the trie but not included into the proof is not verified.
+        assert!(verify_trie_proof::<Layout, _, _, _>(
+                &root,
+                &proof,
+                &[(pairs[1].0.clone(), Some(pairs[1].1.clone()))]
+            ).is_err()
+        );
+    }
 }

test-utils/runtime/Cargo.toml

@@ -35,7 +35,7 @@ pallet-timestamp = { version = "2.0.0", default-features = false, path = "../../
 sc-client = { version = "0.8", optional = true, path = "../../client" }
 sp-trie = { version = "2.0.0", default-features = false, path = "../../primitives/trie" }
 sp-transaction-pool = { version = "2.0.0", default-features = false, path = "../../primitives/transaction-pool" }
-trie-db = { version = "0.18.1", default-features = false }
+trie-db = { version = "0.19.2", default-features = false }
 
 [dev-dependencies]
 sc-executor = { version = "0.8", path = "../../client/executor" }