Merge pull request #30 from WeBankFinTech/feature/evi-linked-event

Evidence in linked event

Author: chaoxinhu

contracts/EvidenceContract.sol

@@ -0,0 +1,107 @@
+pragma solidity ^0.4.4;
+/*
+ *       Copyright© (2018-2020) WeBank Co., Ltd.
+ *
+ *       This file is part of weidentity-contract.
+ *
+ *       weidentity-contract is free software: you can redistribute it and/or modify
+ *       it under the terms of the GNU Lesser General Public License as published by
+ *       the Free Software Foundation, either version 3 of the License, or
+ *       (at your option) any later version.
+ *
+ *       weidentity-contract is distributed in the hope that it will be useful,
+ *       but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *       GNU Lesser General Public License for more details.
+ *
+ *       You should have received a copy of the GNU Lesser General Public License
+ *       along with weidentity-contract.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+contract EvidenceContract {
+
+    // block number map, hash as key
+    mapping(string => uint256) changed;
+
+    // Attribute keys
+    string constant private ATTRIB_KEY_SIGNINFO = "info";
+    string constant private ATTRIB_KEY_EXTRA = "extra";
+
+    // Error codes
+    uint256 constant private RETURN_CODE_SUCCESS = 0;
+    uint256 constant private RETURN_CODE_FAILURE_NOT_EXIST = 500600;
+
+    // Both hash and signer are used as identification key
+    event EvidenceAttributeChanged(
+        string hash,
+        address signer,
+        string key,
+        string value,
+        uint256 updated,
+        uint256 previousBlock
+    );
+
+    function getLatestRelatedBlock(
+        string hash
+    ) 
+        public 
+        constant 
+        returns (uint256) 
+    {
+        return changed[hash];
+    }
+
+    /**
+     * Create evidence. Here, hash value is the key; signInfo is the base64 signature;
+     * and extra is the compact json of blob: {"credentialId":"aacc1122-324b.."}
+     * This allows append operation from other signer onto a same hash, so no permission check.
+     */
+    function createEvidence(
+        string hash,
+        string sig,
+        string extra,
+        uint256 updated
+    )
+        public
+    {
+        EvidenceAttributeChanged(hash, msg.sender, ATTRIB_KEY_SIGNINFO, sig, updated, changed[hash]);
+        EvidenceAttributeChanged(hash, msg.sender, ATTRIB_KEY_EXTRA, extra, updated, changed[hash]);
+        changed[hash] = block.number;
+    }
+
+    /**
+     * Aribitrarily append attributes to an existing hash evidence, e.g. revoke status.
+     */
+    function setAttribute(
+        string hash,
+        string key,
+        string value,
+        uint256 updated
+    )
+        public
+    {
+        if (!isHashExist(hash)) {
+            return;
+        }
+        if (isEqualString(key, ATTRIB_KEY_SIGNINFO)) {
+            return;
+        }
+        EvidenceAttributeChanged(hash, msg.sender, key, value, updated, changed[hash]);
+        changed[hash] = block.number;
+    }
+
+    function isHashExist(string hash) public constant returns (bool) {
+        if (changed[hash] != 0) {
+            return true;
+        }
+        return false;
+    }
+
+    function isEqualString(string a, string b) private constant returns (bool) {
+        if (bytes(a).length != bytes(b).length) {
+            return false;
+        } else {
+            return keccak256(a) == keccak256(b);
+        }
+    }
+}