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Tools/SmartCheck/Solidity/Rules/SOLIDITY_BALANCE_EQUALITY.md

+# Analysis of Smart Contract Security Vulnerabilities and Tools ![](https://img.shields.io/badge/-Live-brightgreen)
+![](https://img.shields.io/badge/Batch-UG21CYS-lightgreen) ![](https://img.shields.io/badge/Batch-PG21CYS-green) ![](https://img.shields.io/badge/Batch-UG22CYS-lightgreen) ![](https://img.shields.io/badge/Batch-PG21CYS-green) ![](https://img.shields.io/badge/Batch-PhD-darkgreen) ![](https://img.shields.io/badge/-B_RIG-darkgreen)<br/>   ![](https://img.shields.io/badge/BlockchainCourse-21CY712-green)  ![](https://img.shields.io/badge/-M.Tech_Dissertation-blue) ![](https://img.shields.io/badge/Focus-Smart_Contract_Security-yellow) <br/>
+![](https://img.shields.io/badge/Blockchain-Ethereum-blue)   <br/> 
+![](https://img.shields.io/badge/Language-Solidity-blue)
+
+## SOLIDITY_BALANCE_EQUALITY
+### Rule Description
+The balance is checked for strict equality.Avoid checking for strict balance equality:an adversary can forcibly send ether to any address via selfdestruct() or by mining.
+### Solidity-Rules
+
+![](https://img.shields.io/badge/Pattern_ID-5094ad-gold) ![](https://img.shields.io/badge/Severity-1-brown) 
+
+```
+expression
+                        [comparison]
+                        [
+                            expression[matches(text()[1], "\.balance$")]
+                            or expression/tupleExpression/expression[matches(text()[1], "\.balance$")]
+                            or expression/expression[matches(text()[1], "\.balance$")]
+                        ]
+
+```
+
+
+### Sample Code
+
+```
+pragma solidity 0.6.0;
+
+contract C {
+
+    function badPrictice(address addr) public {
+        // <yes> <report> SOLIDITY_BALANCE_EQUALITY 5094ad
+        if (this.balance == 100 wei) {
+        }
+        // <yes> <report> SOLIDITY_BALANCE_EQUALITY 5094ad
+        if (address(this).balance != 100 wei) {
+        }
+        // <yes> <report> SOLIDITY_BALANCE_EQUALITY 5094ad
+        if (addr.balance != 100 wei) {
+        }
+        // <yes> <report> SOLIDITY_BALANCE_EQUALITY 5094ad
+        if((addr.balance) == 0) {
+        }
+        // <yes> <report> SOLIDITY_BALANCE_EQUALITY 5094ad
+        if(1 + addr.balance == 0) {
+        }
+    }
+
+    function myFoo(uint[] memory a) public returns(uint) {
+        a[1];
+        a[1:];
+        a[:2];
+        return a[1:2];
+    }
+
+    function goodPrictice(address addr) public {
+        if(myFoo(addr.balance) == 0) {
+        }
+        if (this.balance > 100 wei) {
+        }
+        if (address(this).balance >= 100 wei) {
+        }
+        if (addr.balance <= 100 wei) {
+        }
+        if (msg.sender.balance < 100 wei) {
+        }
+        if (foo(addr).balance >= 100 wei) {
+        }
+    }
+
+    function foo(address _addr) public returns(address) {
+        return _addr;
+    }
+}  
+```
+### Abstract Syntax Tree 
+
+[Click Here](https://astexplorer.net/#/gist/c4237a1f1672914443241ccf90d34cdc/b74242bf8de85a8c4df8dc7a16b26440b52f9c80) to view the AST for the above code. Code generated from AST Explorer using _solidity-parser-antlr-0.4.11_
+
+### Code Result
+
+```
+SOLIDITY_BALANCE_EQUALITY
+patternId: 5094ad
+severity: 1
+line: 7
+column: 12
+content: this.balance==100wei
+
+ruleId: SOLIDITY_BALANCE_EQUALITY
+patternId: 5094ad
+severity: 1
+line: 10
+column: 12
+content: address(this).balance!=100wei
+
+ruleId: SOLIDITY_BALANCE_EQUALITY
+patternId: 5094ad
+severity: 1
+line: 13
+column: 12
+content: addr.balance!=100wei
+
+ruleId: SOLIDITY_BALANCE_EQUALITY
+patternId: 5094ad
+severity: 1
+line: 16
+column: 11
+content: (addr.balance)==0
+
+ruleId: SOLIDITY_BALANCE_EQUALITY
+patternId: 5094ad
+severity: 1
+line: 19
+column: 11
+content: 1+addr.balance==0
+
+SOLIDITY_BALANCE_EQUALITY :5
+
+```