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Tools/SmartCheck/Solidity/Rules/SOLIDITY_TRANSFER_IN_LOOP.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_TRANSFER_IN_LOOP
+### Rule Description
+<p>
+    ETH is transferred in a loop. If at least one address cannot receive ETH (e.g. it is a contract with default fallback function), the whole transaction will be reverted.
+</p>
+<p>
+    Vulnerability type by SmartDec classification: <a href="https://github.com/smartdec/classification#contract-interaction">
+    DoS with revert</a>.
+</p>
+
+### Solidity-Rules
+
+![](https://img.shields.io/badge/Pattern_ID-8jdj43-gold) ![](https://img.shields.io/badge/Severity-2-brown) 
+
+```
+statement
+                        [forStatement or whileStatement or doWhileStatement]
+                        [descendant::functionCall
+                            [functionName/identifier[text()[1] = "transfer"]]
+                            [callArguments/tupleExpression[count(expression) = 1]]
+                        ]
+```
+
+### Sample Code
+
+```
+pragma solidity 0.4.24;
+
+contract ERC20Token {
+    function transfer(address to, uint value) returns(bool);
+}
+
+contract TransferInCycle {
+    address[] users;
+    mapping(address => uint) balances;
+
+    function dangerousWithdraw() returns (bool) {
+        uint l = users.length;
+        // <yes> <report> SOLIDITY_TRANSFER_IN_LOOP 8jdj43
+        for(uint i; i < l; i++) {
+            users[i].transfer(balances[users[i]]);
+        }
+        i=0;
+        // <yes> <report> SOLIDITY_TRANSFER_IN_LOOP 8jdj43
+        while(i < l) {
+            users[i].transfer(balances[users[i]]);
+            i++;
+        }
+    }
+
+    function goodPrictice(address token) {
+        uint l = users.length;
+        uint i;
+        while(i < l) {
+            ERC20Token(token).transfer(users[i], balances[users[i]]);
+            i++;
+        }
+    }
+}
+```
+
+### Abstract Syntax Tree 
+
+[Click Here](https://astexplorer.net/#/gist/55cc5e14e6f147bdae1ead7568b8f233/16f15e101d7cf92c3d118da11935973aab849c75) to view the AST for the above code. Code generated from AST Explorer using _solidity-parser-antlr-0.4.11_
+
+
+### Code Result
+
+```
+SOLIDITY_FUNCTIONS_RETURNS_TYPE_AND_NO_RETURN
+patternId: 47acc2
+severity: 1
+line: 11
+column: 4
+content: functiondangerousWithdraw()returns(bool){uintl=users.length;for(uinti;i<l;i++){users[i].transfer(balances[users[i]]);}i=0;while(i<l){users[i].transfer(balances[users[i]]);i++;}}
+
+ruleId: SOLIDITY_GAS_LIMIT_IN_LOOPS
+patternId: f6f853
+severity: 2
+line: 14
+column: 8
+content: for(uinti;i<l;i++){users[i].transfer(balances[users[i]]);}
+
+ruleId: SOLIDITY_GAS_LIMIT_IN_LOOPS
+patternId: 17f23a
+severity: 1
+line: 19
+column: 14
+content: i<l
+
+ruleId: SOLIDITY_GAS_LIMIT_IN_LOOPS
+patternId: 17f23a
+severity: 1
+line: 28
+column: 14
+content: i<l
+
+ruleId: SOLIDITY_TRANSFER_IN_LOOP
+patternId: 8jdj43
+severity: 2
+line: 14
+column: 8
+content: for(uinti;i<l;i++){users[i].transfer(balances[users[i]]);}
+
+ruleId: SOLIDITY_TRANSFER_IN_LOOP
+patternId: 8jdj43
+severity: 2
+line: 19
+column: 8
+content: while(i<l){users[i].transfer(balances[users[i]]);i++;}
+
+ruleId: SOLIDITY_VISIBILITY
+patternId: 910067
+severity: 1
+line: 4
+column: 4
+content: functiontransfer(addressto,uintvalue)returns(bool);
+
+ruleId: SOLIDITY_VISIBILITY
+patternId: 910067
+severity: 1
+line: 11
+column: 4
+content: functiondangerousWithdraw()returns(bool){uintl=users.length;for(uinti;i<l;i++){users[i].transfer(balances[users[i]]);}i=0;while(i<l){users[i].transfer(balances[users[i]]);i++;}}
+
+ruleId: SOLIDITY_VISIBILITY
+patternId: 910067
+severity: 1
+line: 25
+column: 4
+content: functiongoodPrictice(addresstoken){uintl=users.length;uinti;while(i<l){ERC20Token(token).transfer(users[i],balances[users[i]]);i++;}}
+
+ruleId: SOLIDITY_VISIBILITY
+patternId: b51ce0
+severity: 1
+line: 8
+column: 4
+content: address[]users;
+
+ruleId: SOLIDITY_VISIBILITY
+patternId: b51ce0
+severity: 1
+line: 9
+column: 4
+content: mapping(address=>uint)balances;
+
+SOLIDITY_VISIBILITY :5
+SOLIDITY_FUNCTIONS_RETURNS_TYPE_AND_NO_RETURN :1
+SOLIDITY_GAS_LIMIT_IN_LOOPS :3
+SOLIDITY_TRANSFER_IN_LOOP :2
+
+```