Add block and index proofs [ECR-4011] (#1355)

Added block and index proofs support. They shall be created through Blockchain.

Documented the various proof types: what they prove, what comprises
them, how to create them. Added an example for a commonly used proof type.

Also:
- Made SignedMessage public to be able to use it in tests; 
   got rid of redundant serialization in #parseFrom.
- Added Block#parseFrom and Block#fromMessage.

exonum-java-binding/CHANGELOG.md

@@ -16,17 +16,29 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ## [Unreleased]
 
 ### Added
+- Support of creation of various blockchain proofs:
+    - Block Proof
+    - Transaction Execution Proof
+    - Call Result Proof
+    - Service Data Proof.
+
+  See [`Blockchain`][blockchain-proofs], `BlockProof` and `IndexProof`
+  for details. (#1355)
 - Support of creation of Protobuf-based proofs for maps and lists.
   Such proofs can be easily serialized using Protocol Buffers
   and sent to the light clients.
-  See `ProofMapIndexProxy#getProof` and `MapProof`;
-  `ProofListIndexProxy.getProof`, `ProofListIndexProxy.getRangeProof` and
-  `ListProof`.
+  See:
+     - `ProofMapIndexProxy#getProof` and `MapProof`;
+     - `ProofListIndexProxy.getProof`, `ProofListIndexProxy.getRangeProof` and
+  `ListProof`;
+     - [`Blockchain`][blockchain-proofs].
 - `ProofEntryIndexProxy` collection.
 - `supervisor-mode` CLI parameter added for `generate-template` command. It
   allows to configure the mode of the Supervisor service. Possible values are
   "simple" and "decentralized". (#1361)
 
+[blockchain-proofs]: https://exonum.com/doc/api/java-binding/0.10.0-SNAPSHOT/com/exonum/binding/core/blockchain/Blockchain.html#proofs
+
 ### Changed
 - Transactions are now implemented as service methods annotated with
   `@Transaction(TX_ID)`, instead of classes implementing

exonum-java-binding/common/src/main/java/com/exonum/binding/common/message/SignedMessage.java

@@ -16,9 +16,10 @@
 
 package com.exonum.binding.common.message;
 
+import static com.exonum.binding.common.hash.Hashing.sha256;
+
 import com.exonum.binding.common.crypto.PublicKey;
 import com.exonum.binding.common.hash.HashCode;
-import com.exonum.binding.common.hash.Hashing;
 import com.exonum.core.messages.Consensus;
 import com.exonum.core.messages.Consensus.ExonumMessage;
 import com.google.protobuf.ByteString;
@@ -31,7 +32,7 @@
  * <p>It currently does not support verification of the signature against the author's public
  * key — such functionality may be added later if needed.
  */
-final class SignedMessage {
+public final class SignedMessage {
 
   private final ExonumMessage payload;
   private final PublicKey authorPk;
@@ -56,10 +57,11 @@ private SignedMessage(ExonumMessage payload, PublicKey authorPk,
    *     {@link Consensus.SignedMessage}; or if the payload of the message is not
    *     {@link Consensus.ExonumMessage}
    */
-  static SignedMessage parseFrom(byte[] messageBytes) throws InvalidProtocolBufferException {
+  public static SignedMessage parseFrom(byte[] messageBytes) throws InvalidProtocolBufferException {
     // Try to decode the SignedMessage container
+    HashCode hash = sha256().hashBytes(messageBytes);
     Consensus.SignedMessage message = Consensus.SignedMessage.parseFrom(messageBytes);
-    return fromProto(message);
+    return fromProto(message, hash);
   }
 
   /**
@@ -69,26 +71,28 @@ static SignedMessage parseFrom(byte[] messageBytes) throws InvalidProtocolBuffer
    * @throws InvalidProtocolBufferException if a signed message does not contain a valid payload
    *     that is a serialized {@link Consensus.ExonumMessage}
    */
-  static SignedMessage fromProto(Consensus.SignedMessage message)
+  public static SignedMessage fromProto(Consensus.SignedMessage message)
       throws InvalidProtocolBufferException {
+    HashCode hash = sha256().hashBytes(message.toByteArray());
+    return fromProto(message, hash);
+  }
+
+  private static SignedMessage fromProto(Consensus.SignedMessage message,
+      HashCode messageHash) throws InvalidProtocolBufferException {
     // Try to decode the payload, which is stored as bytes. It is expected to be an ExonumMessage
     ByteString payloadBytes = message.getPayload();
     ExonumMessage payload = ExonumMessage.parseFrom(payloadBytes);
-
     PublicKey authorPk = PublicKey.fromBytes(message.getAuthor()
         .getData()
         .toByteArray());
     ByteString signature = message.getSignature().getData();
-
-    HashCode hash = Hashing.sha256().hashBytes(message.toByteArray());
-
-    return new SignedMessage(payload, authorPk, signature, hash);
+    return new SignedMessage(payload, authorPk, signature, messageHash);
   }
 
   /**
    * Returns the message payload.
    */
-  Consensus.ExonumMessage getPayload() {
+  public Consensus.ExonumMessage getPayload() {
     return payload;
   }
 
@@ -98,7 +102,7 @@ Consensus.ExonumMessage getPayload() {
    * <p>The correctness of the signature is <strong>not</strong> verified against this key
    * and must be done separately if needed.
    */
-  PublicKey getAuthorPk() {
+  public PublicKey getAuthorPk() {
     return authorPk;
   }
 
@@ -109,15 +113,15 @@ PublicKey getAuthorPk() {
    * <p>The correctness of the signature is <strong>not</strong> verified against this key
    * and must be done separately if needed.
    */
-  byte[] getSignature() {
+  public byte[] getSignature() {
     return signature.toByteArray();
   }
 
   /**
    * Returns the hash of the signed message, which is the hash of the protobuf-serialized
    * representation.
    */
-  HashCode hash() {
+  public HashCode hash() {
     return hash;
   }
 }

exonum-java-binding/core/rust/src/storage/blockchain.rs

@@ -20,7 +20,7 @@ use {
 /// - index is not initialized (index have not been used before calling the method)
 /// - index is not Merkelized
 #[no_mangle]
-pub extern "system" fn Java_com_exonum_binding_core_blockchain_Blockchain_nativeCreateIndexProof(
+pub extern "system" fn Java_com_exonum_binding_core_blockchain_BlockchainProofs_nativeCreateIndexProof(
     env: JNIEnv,
     _: JObject,
     snapshot_handle: jlong,
@@ -50,7 +50,7 @@ pub extern "system" fn Java_com_exonum_binding_core_blockchain_Blockchain_native
 /// - there is no such block
 /// - passed `snapshot_handle` is Fork handle
 #[no_mangle]
-pub extern "system" fn Java_com_exonum_binding_core_blockchain_Blockchain_nativeCreateBlockProof(
+pub extern "system" fn Java_com_exonum_binding_core_blockchain_BlockchainProofs_nativeCreateBlockProof(
     env: JNIEnv,
     _: JObject,
     snapshot_handle: jlong,

exonum-java-binding/core/src/main/java/com/exonum/binding/core/blockchain/Block.java

@@ -16,9 +16,11 @@
 
 package com.exonum.binding.core.blockchain;
 
+import static com.exonum.binding.common.hash.Hashing.sha256;
 import static com.google.common.base.Preconditions.checkState;
 
 import com.exonum.binding.common.hash.HashCode;
+import com.exonum.binding.core.blockchain.serialization.BlockSerializer;
 import com.exonum.binding.core.blockchain.serialization.CoreTypeAdapterFactory;
 import com.exonum.binding.core.service.Schema;
 import com.google.auto.value.AutoValue;
@@ -95,7 +97,7 @@ public final boolean isEmpty() {
   /**
    * Root hash of exceptions occurred in the block.
    *
-   * @see Blockchain#getCallErrors()
+   * @see Blockchain#getCallErrors(long)
    */
   public abstract HashCode getErrorHash();
 
@@ -122,6 +124,27 @@ public static TypeAdapter<Block> typeAdapter(Gson gson) {
     return new AutoValue_Block.GsonTypeAdapter(gson);
   }
 
+  /**
+   * Creates a block from the block message.
+   * @param blockMessage a block
+   */
+  public static Block fromMessage(com.exonum.core.messages.Blockchain.Block blockMessage) {
+    // Such implementation prevents a redundant deserialization of Block message
+    // (in BlockSerializer#fromBytes).
+    HashCode blockHash = sha256().hashBytes(blockMessage.toByteArray());
+    return BlockSerializer.newBlockInternal(blockMessage, blockHash);
+  }
+
+  /**
+   * Creates a block from the serialized block message.
+   * @param serializedBlock a serialized block message
+   * @throws IllegalArgumentException if the block bytes are not a serialized
+   *     {@link com.exonum.core.messages.Blockchain.Block}
+   */
+  public static Block parseFrom(byte[] serializedBlock) {
+    return BlockSerializer.INSTANCE.fromBytes(serializedBlock);
+  }
+
   /**
    * Creates a new block builder.
    */
@@ -172,7 +195,7 @@ public abstract static class Builder {
      * Sets the blockchain state hash at the moment this block was committed. The blockchain
      * state hash reflects the state of each service in the database.
      *
-     * @see Schema#getStateHashes()
+     * @see Schema
      */
     public abstract Builder stateHash(HashCode blockchainStateHash);