Receipts

CMakeLists.txt

@@ -299,6 +299,12 @@ if(BUILD_TESTS)
           --app-script ${CMAKE_CURRENT_SOURCE_DIR}/samples/apps/txregulator/app/txregulator.lua
           --datafile ${CMAKE_CURRENT_SOURCE_DIR}/samples/apps/txregulator/dataset/sample_data.csv)
 
+      ## Receipts end to end test
+      add_e2e_test(
+        NAME receipts_test
+        PYTHON_SCRIPT ${CMAKE_SOURCE_DIR}/tests/receipts.py
+      )
+
       if(QUOTES_ENABLED)
         add_e2e_test(
           NAME governance_tests

sphinx/source/schemas/getReceipt_params.json

@@ -0,0 +1,15 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "properties": {
+    "commit": {
+      "maximum": 9223372036854775807,
+      "minimum": -9223372036854775808,
+      "type": "number"
+    }
+  },
+  "required": [
+    "commit"
+  ],
+  "title": "getReceipt/params",
+  "type": "object"
+}

sphinx/source/schemas/getReceipt_result.json

@@ -0,0 +1,18 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "properties": {
+    "receipt": {
+      "items": {
+        "maximum": 255,
+        "minimum": 0,
+        "type": "number"
+      },
+      "type": "array"
+    }
+  },
+  "required": [
+    "receipt"
+  ],
+  "title": "getReceipt/result",
+  "type": "object"
+}

sphinx/source/schemas/verifyReceipt_params.json

@@ -0,0 +1,18 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "properties": {
+    "receipt": {
+      "items": {
+        "maximum": 255,
+        "minimum": 0,
+        "type": "number"
+      },
+      "type": "array"
+    }
+  },
+  "required": [
+    "receipt"
+  ],
+  "title": "verifyReceipt/params",
+  "type": "object"
+}

sphinx/source/schemas/verifyReceipt_result.json

@@ -0,0 +1,13 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "properties": {
+    "valid": {
+      "type": "boolean"
+    }
+  },
+  "required": [
+    "valid"
+  ],
+  "title": "verifyReceipt/result",
+  "type": "object"
+}

sphinx/source/users/issue_commands.rst

@@ -75,3 +75,66 @@ To guarantee that their request is successfully committed to the ledger, a user
     }
 
 In this example, the ``result`` field indicates that the request was executed at ``30`` (``commit``) was in term ``2``, the same term that the ``LOG_record``. Moreover, the ``global_commit`` (``31``) is now greater than the ``commit`` version. The ``LOG_record`` request issued earlier was successfully committed to the ledger.
+
+Transaction receipts
+--------------------
+
+Once a transaction has been committed, it is possible to get a receipt for it. That receipt can later be checked against either a CCF service, or offline against the ledger, to prove that the transaction did happen at a particular commit.
+
+To obtain a receipt, a user needs to issue a ``getReceipt`` RPC for a particular commit:
+
+.. code-block:: bash
+
+    $ cat get_receipt.json
+    {
+      "id": 0,
+      "method": "users/getReceipt",
+      "jsonrpc": "2.0",
+      "params":
+      {
+        "commit": 30
+      }
+   }
+
+    $ client --pretty-print --rpc-address node_rpc_ip:node_rpc_port --ca networkcert.pem userrpc --req @get_receipt.json --cert user_cert.pem --pk user_privk.pem
+    Sending RPC to node_rpc_ip:node_rpc_port
+    Doing user RPC:
+    {
+      "commit": 31,
+      "global_commit": 31,
+      "id": 0,
+      "jsonrpc": "2.0",
+      "result": {
+        "receipt": [ ... ],
+      },
+      "term": 2
+    }
+
+Receipts can be verified with the ``verifyReceipt`` RPC:
+
+.. code-block:: bash
+
+    $ cat get_receipt.json
+    {
+      "id": 0,
+      "method": "users/verifyReceipt",
+      "jsonrpc": "2.0",
+      "params":
+      {
+        "receipt": [ ... ]
+      }
+   }
+
+    $ client --pretty-print --rpc-address node_rpc_ip:node_rpc_port --ca networkcert.pem userrpc --req @get_receipt.json --cert user_cert.pem --pk user_privk.pem
+    Sending RPC to node_rpc_ip:node_rpc_port
+    Doing user RPC:
+    {
+      "commit": 31,
+      "global_commit": 31,
+      "id": 0,
+      "jsonrpc": "2.0",
+      "result": {
+        "valid": true,
+      },
+      "term": 2
+    }

src/kv/kvtypes.h

@@ -135,6 +135,8 @@ namespace kv
     virtual void clear_on_result() = 0;
     virtual void clear_on_response() = 0;
     virtual crypto::Sha256Hash get_root() = 0;
+    virtual std::vector<uint8_t> get_receipt(Version v) = 0;
+    virtual bool verify_receipt(const std::vector<uint8_t>& receipt) = 0;
   };
 
   class Consensus

src/node/history.h

@@ -175,6 +175,87 @@ namespace ccf
     {
       return crypto::Sha256Hash();
     }
+
+    std::vector<uint8_t> get_receipt(kv::Version v) override
+    {
+      return {};
+    }
+
+    bool verify_receipt(const std::vector<uint8_t>& v) override
+    {
+      return true;
+    }
+  };
+
+  class Receipt
+  {
+  private:
+    uint64_t index;
+    uint32_t max_index;
+    crypto::Sha256Hash root;
+    hash_vec* path;
+
+  public:
+    Receipt()
+    {
+      path = init_path();
+    }
+
+    static Receipt from_v(const std::vector<uint8_t>& v)
+    {
+      Receipt r;
+      const uint8_t* buf = v.data();
+      size_t s = v.size();
+      r.index = serialized::read<decltype(index)>(buf, s);
+      r.max_index = serialized::read<decltype(max_index)>(buf, s);
+      std::copy(buf, buf + r.root.SIZE, r.root.h);
+      buf += r.root.SIZE;
+      s -= r.root.SIZE;
+      for (size_t i = 0; i < s; i += r.root.SIZE)
+        path_insert(r.path, const_cast<uint8_t*>(buf + i));
+      return r;
+    }
+
+    Receipt(merkle_tree* tree, uint64_t index_)
+    {
+      index = index_;
+      path = init_path();
+
+      if (!mt_get_path_pre(tree, index, path, root.h))
+      {
+        free_path(path);
+        throw std::logic_error("Precondition to mt_get_path violated");
+      }
+
+      max_index = mt_get_path(tree, index, path, root.h);
+    }
+
+    bool verify(merkle_tree* tree) const
+    {
+      if (!mt_verify_pre(tree, index, max_index, path, (uint8_t*)root.h))
+        throw std::logic_error("Precondition to mt_verify violated");
+
+      return mt_verify(tree, index, max_index, path, (uint8_t*)root.h);
+    }
+
+    ~Receipt()
+    {
+      free_path(path);
+    }
+
+    std::vector<uint8_t> to_v() const
+    {
+      size_t vs =
+        sizeof(index) + sizeof(max_index) + root.SIZE + root.SIZE * path->sz;
+      std::vector<uint8_t> v(vs);
+      uint8_t* buf = v.data();
+      serialized::write(buf, vs, index);
+      serialized::write(buf, vs, max_index);
+      serialized::write(buf, vs, root.h, root.SIZE);
+      for (size_t i = 0; i < path->sz; ++i)
+        serialized::write(buf, vs, *(path->vs + i), root.SIZE);
+      return v;
+    }
   };
 
   class MerkleTreeHistory
@@ -233,6 +314,16 @@ namespace ccf
         throw std::logic_error("Precondition to mt_retract_to violated");
       mt_retract_to(tree, index);
     }
+
+    Receipt get_receipt(uint64_t index)
+    {
+      return Receipt(tree, index);
+    }
+
+    bool verify(const Receipt& r)
+    {
+      return r.verify(tree);
+    }
   };
 
   template <class T>
@@ -434,6 +525,17 @@ namespace ccf
       LOG_DEBUG << fmt::format("HISTORY: add_response {0}", id) << std::endl;
       responses[id] = response;
     }
+
+    std::vector<uint8_t> get_receipt(kv::Version index) override
+    {
+      return tree.get_receipt(index).to_v();
+    }
+
+    bool verify_receipt(const std::vector<uint8_t>& v) override
+    {
+      auto r = Receipt::from_v(v);
+      return tree.verify(r);
+    }
   };
 
   using MerkleTxHistory = HashedTxHistory<MerkleTreeHistory>;

src/node/rpc/calltypes.h

@@ -89,4 +89,30 @@ namespace ccf
       ds::json::JsonSchema result_schema = {};
     };
   };
+
+  struct GetReceipt
+  {
+    struct In
+    {
+      int64_t commit = 0;
+    };
+
+    struct Out
+    {
+      std::vector<std::uint8_t> receipt = {};
+    };
+  };
+
+  struct VerifyReceipt
+  {
+    struct In
+    {
+      std::vector<std::uint8_t> receipt = {};
+    };
+
+    struct Out
+    {
+      bool valid = false;
+    };
+  };
 }

src/node/rpc/consts.h

@@ -23,6 +23,8 @@ namespace ccf
     static constexpr auto GET_NETWORK_INFO = "getNetworkInfo";
     static constexpr auto LIST_METHODS = "listMethods";
     static constexpr auto GET_SCHEMA = "getSchema";
+    static constexpr auto GET_RECEIPT = "getReceipt";
+    static constexpr auto VERIFY_RECEIPT = "verifyReceipt";
   };
 
   struct MemberProcs