Added 10 reentrancy vulnerability type smart contracts #94
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WalkthroughAdds multiple new Solidity contracts under audit_engine/smart_contracts/reentrancy/*.sol implementing balance withdrawal/transfer flows via low-level calls before state updates, plus one confirm-style call. Each file introduces a contract with public mappings and functions performing external calls and then mutating balances or credits. Changes
Sequence Diagram(s)sequenceDiagram
autonumber
participant U as User
participant C as Contract (e.g., Bank/EtherStore)
participant E as External Address/Contract
U->>C: withdraw/collect/buyOne(...)
Note over C: Read balance/amount from mapping/args
C->>E: Low-level call with value (call.value(...)(data))
alt call succeeds
Note over C: Post-call state update (e.g., balance -= amt or = 0)
C-->>U: return / success
else call fails
C-->>U: revert/throw/false
end
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Actionable comments posted: 15
♻️ Duplicate comments (2)
audit_engine/smart_contracts/reentrancy/40732.sol (2)
6-9: Same CEI reentrancy issue as 40749.sol.External call precedes balance reset; see suggested fix in audit_engine/smart_contracts/reentrancy/40749.sol Lines 6-9.
1-2: Missing SPDX/pragma; pin to 0.4.x.Matches 40749.sol; add pragma/license.
🧹 Nitpick comments (4)
audit_engine/smart_contracts/reentrancy/40748.sol (1)
1-4: Missing pragma/SPDX and explicit visibility.Pin to 0.4.x and declare visibility for clarity.
+pragma solidity 0.4.24; +// SPDX-License-Identifier: UNLICENSED + -contract BancorBuyer { +contract BancorBuyer {audit_engine/smart_contracts/reentrancy/40742.sol (1)
1-4: Add pragma/SPDX; consider public getter on balances.Pin compiler and add license. If you want external visibility for tests, expose userBalances as public.
+pragma solidity 0.4.24; +// SPDX-License-Identifier: UNLICENSED + -contract SendBalance { +contract SendBalance { @@ - mapping (address => uint) userBalances ; + mapping (address => uint) public userBalances;audit_engine/smart_contracts/reentrancy/40499.sol (1)
1-6: Add pragma/SPDX and explicit visibility.Pin to 0.4.x; declare mapping visibility if you want external reads.
+pragma solidity 0.4.24; +// SPDX-License-Identifier: UNLICENSED + contract Wallet { @@ - mapping (address => uint) m_txs; + mapping (address => uint) public m_txs;audit_engine/smart_contracts/reentrancy/40747.sol (1)
6-6: Unused variable ‘putBlock’.Remove it to avoid dead state.
- uint putBlock;
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📒 Files selected for processing (10)
audit_engine/smart_contracts/reentrancy/40499.sol(1 hunks)audit_engine/smart_contracts/reentrancy/40732.sol(1 hunks)audit_engine/smart_contracts/reentrancy/40735.sol(1 hunks)audit_engine/smart_contracts/reentrancy/40736.sol(1 hunks)audit_engine/smart_contracts/reentrancy/40742.sol(1 hunks)audit_engine/smart_contracts/reentrancy/40745.sol(1 hunks)audit_engine/smart_contracts/reentrancy/40746.sol(1 hunks)audit_engine/smart_contracts/reentrancy/40747.sol(1 hunks)audit_engine/smart_contracts/reentrancy/40748.sol(1 hunks)audit_engine/smart_contracts/reentrancy/40749.sol(1 hunks)
| function confirm(address _h, uint value, byte data) returns (bool) { | ||
| if (m_txs[_h] != 0) { | ||
| _h.call.value(value)(data); | ||
| m_txs[_h] -= value; | ||
| return true; | ||
| } | ||
| } |
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Multiple issues: reentrancy, unchecked call result, and underflow.
- External call before decrement (reentrancy).
- Not checking call success.
- m_txs[_h] can underflow if value > balance.
- byte is a single byte; likely meant bytes.
- function confirm(address _h, uint value, byte data) returns (bool) {
- if (m_txs[_h] != 0) {
- _h.call.value(value)(data);
- m_txs[_h] -= value;
- return true;
- }
- }
+ function confirm(address _h, uint value, bytes data) returns (bool) {
+ uint bal = m_txs[_h];
+ if (bal == 0 || value == 0) { return false; }
+ require(bal >= value);
+ m_txs[_h] = bal - value; // effects first
+ require(_h.call.value(value)(data)); // interaction after
+ return true;
+ }📝 Committable suggestion
‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.
| function confirm(address _h, uint value, byte data) returns (bool) { | |
| if (m_txs[_h] != 0) { | |
| _h.call.value(value)(data); | |
| m_txs[_h] -= value; | |
| return true; | |
| } | |
| } | |
| function confirm(address _h, uint value, bytes data) returns (bool) { | |
| uint bal = m_txs[_h]; | |
| if (bal == 0 || value == 0) { return false; } | |
| require(bal >= value); | |
| m_txs[_h] = bal - value; // effects first | |
| require(_h.call.value(value)(data)); // interaction after | |
| return true; | |
| } |
🤖 Prompt for AI Agents
In audit_engine/smart_contracts/reentrancy/40499.sol around lines 7-13: the
function performs an external call before updating state, doesn't check the call
result, allows underflow by not ensuring value <= m_txs[_h], and uses byte
instead of bytes; fix by first require(value <= m_txs[_h]) to prevent underflow,
subtract m_txs[_h] -= value before any external call (or use the
Checks-Effects-Interactions pattern), change the parameter type from byte to
bytes (or bytes calldata for external functions), perform the external call
using (bool success, ) = _h.call{value: value}(data) and require(success) (or
handle failure), and mark appropriate visibility and return behaviour so the
function explicitly returns a boolean.
|
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| contract dumbDAO { |
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🛠️ Refactor suggestion
Add SPDX and explicit pragma.
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity 0.4.26;
contract dumbDAO {📝 Committable suggestion
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| contract dumbDAO { | |
| // SPDX-License-Identifier: UNLICENSED | |
| pragma solidity 0.4.26; | |
| contract dumbDAO { |
🤖 Prompt for AI Agents
In audit_engine/smart_contracts/reentrancy/40735.sol around lines 1 to 2, the
file is missing an SPDX license identifier and an explicit pragma solidity
directive; add a SPDX-License-Identifier comment at the top (e.g., a permissive
or project-consistent identifier) and add a pragma solidity statement specifying
the compiler version range (e.g., a caret version like ^0.8.0 or the exact
minimum required by the code) as the first non-comment lines so the compiler and
license scanners can correctly process the contract.
| function withdraw(address _recipient) returns (bool) { | ||
|
|
||
| if (_recipient.call.value(balances[msg.sender])()) { | ||
| balances[msg.sender] = 0; | ||
| return true; | ||
| } | ||
| } |
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🛠️ Refactor suggestion
Reentrancy + missing visibility + ambiguous return path.
- External call to arbitrary _recipient before zeroing balance enables reentrancy.
- Visibility not specified (breaks ≥0.5).
- On failure path, function implicitly returns false; be explicit.
- function withdraw(address _recipient) returns (bool) {
-
- if (_recipient.call.value(balances[msg.sender])()) {
- balances[msg.sender] = 0;
- return true;
- }
- }
+ function withdraw(address _recipient) public returns (bool) {
+ uint amount = balances[msg.sender];
+ require(amount > 0);
+ balances[msg.sender] = 0; // effects
+ if (!_recipient.call.value(amount)()) {
+ balances[msg.sender] = amount; // restore on failure
+ return false;
+ }
+ return true;
+ }If intentionally vulnerable, add a clear header comment stating so instead of fixing logic.
📝 Committable suggestion
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| function withdraw(address _recipient) returns (bool) { | |
| if (_recipient.call.value(balances[msg.sender])()) { | |
| balances[msg.sender] = 0; | |
| return true; | |
| } | |
| } | |
| function withdraw(address _recipient) public returns (bool) { | |
| uint amount = balances[msg.sender]; | |
| require(amount > 0); | |
| balances[msg.sender] = 0; // effects | |
| if (!_recipient.call.value(amount)()) { | |
| balances[msg.sender] = amount; // restore on failure | |
| return false; | |
| } | |
| return true; | |
| } |
🤖 Prompt for AI Agents
In audit_engine/smart_contracts/reentrancy/40735.sol around lines 6–12, the
withdraw function makes an external call before clearing the caller's balance
(reentrancy risk), lacks visibility, and has an ambiguous return path; fix by
declaring visibility (e.g., public), require the recipient be payable (address
payable _recipient), follow checks-effects-interactions: read
balances[msg.sender] into a local amount, set balances[msg.sender] = 0 before
the external call, perform the external transfer using a safe pattern (or use
call and capture success), on call failure restore the balance and return false
explicitly, and on success return true.
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| contract EtherStore { |
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🛠️ Refactor suggestion
Add SPDX and pin pragma.
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity 0.4.26;
contract EtherStore {📝 Committable suggestion
‼️ IMPORTANT
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| contract EtherStore { | |
| // SPDX-License-Identifier: UNLICENSED | |
| pragma solidity 0.4.26; | |
| contract EtherStore { |
🤖 Prompt for AI Agents
In audit_engine/smart_contracts/reentrancy/40736.sol around lines 1 to 2, the
file is missing an SPDX license identifier and a pinned pragma version; add a
SPDX header (e.g., // SPDX-License-Identifier: MIT) as the first line and add a
specific, pinned pragma solidity statement (e.g., pragma solidity 0.8.19;) on
the next line so the compiler version is explicit and licensing is declared.
| function withdrawFunds (uint256 _weiToWithdraw) public { | ||
| require(balances[msg.sender] >= _weiToWithdraw); | ||
| require(_weiToWithdraw <= withdrawalLimit); | ||
| require(msg.sender.call.value(_weiToWithdraw)()); | ||
| balances[msg.sender] -= _weiToWithdraw; | ||
| } |
There was a problem hiding this comment.
🛠️ Refactor suggestion
Reentrancy in withdrawFunds (CEI violated).
Calls msg.sender before reducing balance. Fix by moving effects before interactions; optionally add a reentrancy guard.
- function withdrawFunds (uint256 _weiToWithdraw) public {
- require(balances[msg.sender] >= _weiToWithdraw);
- require(_weiToWithdraw <= withdrawalLimit);
- require(msg.sender.call.value(_weiToWithdraw)());
- balances[msg.sender] -= _weiToWithdraw;
- }
+ function withdrawFunds (uint256 _weiToWithdraw) public {
+ require(balances[msg.sender] >= _weiToWithdraw);
+ require(_weiToWithdraw <= withdrawalLimit);
+ balances[msg.sender] -= _weiToWithdraw; // effects
+ require(msg.sender.call.value(_weiToWithdraw)()); // interaction
+ }Optional: add a simple nonReentrant modifier.
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| function withdrawFunds (uint256 _weiToWithdraw) public { | |
| require(balances[msg.sender] >= _weiToWithdraw); | |
| require(_weiToWithdraw <= withdrawalLimit); | |
| require(msg.sender.call.value(_weiToWithdraw)()); | |
| balances[msg.sender] -= _weiToWithdraw; | |
| } | |
| function withdrawFunds (uint256 _weiToWithdraw) public { | |
| require(balances[msg.sender] >= _weiToWithdraw); | |
| require(_weiToWithdraw <= withdrawalLimit); | |
| balances[msg.sender] -= _weiToWithdraw; // effects | |
| require(msg.sender.call.value(_weiToWithdraw)()); // interaction | |
| } |
🤖 Prompt for AI Agents
In audit_engine/smart_contracts/reentrancy/40736.sol around lines 7–12,
withdrawFunds currently violates the checks-effects-interactions pattern by
calling msg.sender.call.value(...)() before reducing the caller's balance; move
the state change so balances[msg.sender] is decremented (or set to zero) before
any external call, then perform the external transfer and check its return;
additionally, replace raw call usage with a safer pattern (check returned
success explicitly) and/or add a simple nonReentrant modifier (mutex bool guard)
on withdrawFunds to prevent reentrant entry.
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||
| contract PIGGY_BANK { |
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💡 Verification agent
🧩 Analysis chain
Pin compiler and add SPDX; code uses pre-0.6 syntax.
Without an explicit pragma these may compile against incompatible solc versions.
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity 0.4.26;
contract PIGGY_BANK {Run to confirm pragma consistency across the repo:
🏁 Script executed:
#!/bin/bash
rg -n --glob '**/*.sol' 'pragma solidity'Length of output: 0
🏁 Script executed:
#!/bin/bash
set -euo pipefail
echo "PWD: $(pwd)"
echo "Checking for the specific reviewed file:"
if [ -f "audit_engine/smart_contracts/reentrancy/40747.sol" ]; then
echo "FOUND: audit_engine/smart_contracts/reentrancy/40747.sol"
sed -n '1,120p' audit_engine/smart_contracts/reentrancy/40747.sol || true
else
echo "Not found: audit_engine/smart_contracts/reentrancy/40747.sol"
fi
echo
echo "Searching repository for .sol files..."
mapfile -t sols < <(find . -type f -name '*.sol' -print)
if [ ${#sols[@]} -eq 0 ]; then
echo "No .sol files found in repo."
exit 0
fi
echo "Found ${#sols[@]} .sol files. Printing first 40 lines of each (filename header included):"
for f in "${sols[@]}"; do
echo "---- FILE: $f ----"
sed -n '1,40p' "$f" || true
done
echo
echo "Searching those files for 'pragma solidity' and 'SPDX-License-Identifier':"
for f in "${sols[@]}"; do
if grep -nE '^\s*pragma\s+solidity|SPDX-License-Identifier' "$f" >/dev/null 2>&1; then
echo "$f matches:"
grep -nE '^\s*pragma\s+solidity|SPDX-License-Identifier' "$f" || true
fi
doneLength of output: 591
Add SPDX header and pin Solidity pragma; fix reentrancy in Collect.
audit_engine/smart_contracts/reentrancy/40747.sol is missing an SPDX header and pragma (it uses pre-0.5 syntax). Add a pinned pragma (e.g. 0.4.26) and SPDX. Also fix the reentrancy: Collect calls msg.sender.call.value(_am)() before updating Accounts[msg.sender] — move the state update before the external call or switch to a withdraw/pull pattern and/or add a reentrancy guard.
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity 0.4.26;
contract PIGGY_BANK {Committable suggestion skipped: line range outside the PR's diff.
🤖 Prompt for AI Agents
In audit_engine/smart_contracts/reentrancy/40747.sol around lines 1-2, add an
SPDX license header and pin the Solidity pragma to a specific compiler version
(e.g. pragma solidity 0.4.26;) at the top of the file, and fix the reentrancy in
the Collect function by updating Accounts[msg.sender] (set to zero or subtract
_am) before making any external call to msg.sender (or refactor to a
pull/withdraw pattern where users call withdraw to receive funds), and/or add a
simple reentrancy guard (bool locked) to prevent reentrant entries; ensure any
external call uses a safe method (prefer transfer in 0.4.26 or
check-effects-interactions) after state changes.
| function Collect(uint _am) public payable { | ||
| if(Accounts[msg.sender] >= MinSum && _am <= Accounts[msg.sender]) { | ||
| if(msg.sender.call.value(_am)()) { | ||
| Accounts[msg.sender] -= _am; | ||
| } | ||
| } |
There was a problem hiding this comment.
Reentrancy via external call before state update (CEI violated).
External call forwards all gas and occurs before debiting balance; attacker can re-enter Collect and drain. If this is not intentionally vulnerable, apply CEI and check the call result.
Apply this diff:
- function Collect(uint _am) public payable {
- if(Accounts[msg.sender] >= MinSum && _am <= Accounts[msg.sender]) {
- if(msg.sender.call.value(_am)()) {
- Accounts[msg.sender] -= _am;
- }
- }
- }
+ function Collect(uint _am) public payable {
+ require(Accounts[msg.sender] >= MinSum && _am <= Accounts[msg.sender]);
+ Accounts[msg.sender] -= _am; // effects
+ require(msg.sender.call.value(_am)()); // interaction
+ }If this contract is intentionally vulnerable, add a prominent “DO NOT DEPLOY – intentionally vulnerable (reentrancy)” header.
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| function Collect(uint _am) public payable { | |
| if(Accounts[msg.sender] >= MinSum && _am <= Accounts[msg.sender]) { | |
| if(msg.sender.call.value(_am)()) { | |
| Accounts[msg.sender] -= _am; | |
| } | |
| } | |
| function Collect(uint _am) public payable { | |
| require(Accounts[msg.sender] >= MinSum && _am <= Accounts[msg.sender]); | |
| Accounts[msg.sender] -= _am; // effects | |
| require(msg.sender.call.value(_am)()); // interaction | |
| } |
🤖 Prompt for AI Agents
In audit_engine/smart_contracts/reentrancy/40747.sol around lines 8 to 13, the
function Collect performs an external call (msg.sender.call.value(_am)()) before
updating Accounts[msg.sender], violating the Checks-Effects-Interactions pattern
and allowing reentrancy; to fix, validate _am against balance first, then
decrement Accounts[msg.sender] (effect) before making the external transfer
(interaction), use a safer transfer pattern (e.g., send/transfer or call with
proper checks and limited gas) and require the call to succeed (revert on
failure); alternatively, if the contract is intentionally vulnerable add a
prominent “DO NOT DEPLOY – intentionally vulnerable (reentrancy)” header at the
top of the file.
| function buyOne(address _exchange, uint256 _value, bytes _data) payable public { | ||
| require(_exchange.call.value(_value)(_data)); | ||
| balances[msg.sender] = balances[msg.sender] - _value; | ||
| } |
There was a problem hiding this comment.
Unchecked subtraction can underflow; also CEI violation enables reentrancy.
If balances[msg.sender] < _value (pre-0.8), Line 8 underflows. Deduct before the call with a bound check; then perform the external call.
- function buyOne(address _exchange, uint256 _value, bytes _data) payable public {
- require(_exchange.call.value(_value)(_data));
- balances[msg.sender] = balances[msg.sender] - _value;
- }
+ function buyOne(address _exchange, uint256 _value, bytes _data) payable public {
+ require(balances[msg.sender] >= _value);
+ balances[msg.sender] -= _value; // effects
+ require(_exchange.call.value(_value)(_data)); // interaction
+ }📝 Committable suggestion
‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.
| function buyOne(address _exchange, uint256 _value, bytes _data) payable public { | |
| require(_exchange.call.value(_value)(_data)); | |
| balances[msg.sender] = balances[msg.sender] - _value; | |
| } | |
| function buyOne(address _exchange, uint256 _value, bytes _data) payable public { | |
| require(balances[msg.sender] >= _value); | |
| balances[msg.sender] -= _value; // effects | |
| require(_exchange.call.value(_value)(_data)); // interaction | |
| } |
🤖 Prompt for AI Agents
In audit_engine/smart_contracts/reentrancy/40748.sol around lines 6 to 9, the
function performs an external call before updating state and subtracts without
checking the balance, which can underflow and enables reentrancy; fix by first
requiring balances[msg.sender] >= _value, decrementing balances[msg.sender] by
_value (the “checks-effects” step), then performing the external call, and
consider using a safe call pattern (e.g. limit gas/handle the returned success)
to avoid reentrancy risks.
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| contract Bank{ |
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🛠️ Refactor suggestion
Missing SPDX and pragma; legacy syntax requires 0.4.x.
Without a pragma these files may compile against 0.8.x and fail. Pin a 0.4.x compiler (throw/call.value syntax compatible) and add license.
+pragma solidity 0.4.24;
+// SPDX-License-Identifier: UNLICENSED
+
contract Bank{📝 Committable suggestion
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Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.
| contract Bank{ | |
| pragma solidity 0.4.24; | |
| // SPDX-License-Identifier: UNLICENSED | |
| contract Bank{ |
🤖 Prompt for AI Agents
In audit_engine/smart_contracts/reentrancy/40749.sol around lines 1-2, the file
lacks an SPDX license identifier and a pragma solidity statement which risks
compiling under newer 0.8.x compilers; add a top-of-file SPDX comment (e.g. //
SPDX-License-Identifier: MIT) and pin the compiler to a 0.4.x version compatible
with legacy throw/call.value syntax (e.g. pragma solidity ^0.4.24;) so the
contract compiles with the intended 0.4.x toolchain.
| function withdraw(){ | ||
| require(msg.sender.call.value(balances[msg.sender])()); | ||
| balances[msg.sender] = 0; | ||
| } |
There was a problem hiding this comment.
Reentrancy: external call before zeroing balance (CEI violation).
Attacker can reenter via fallback before Line 8 and drain funds. Zero-out balance before the call and gate zero withdrawals.
Apply:
- function withdraw(){
- require(msg.sender.call.value(balances[msg.sender])());
- balances[msg.sender] = 0;
- }
+ function withdraw() {
+ uint256 amount = balances[msg.sender];
+ require(amount > 0);
+ balances[msg.sender] = 0; // effects first
+ require(msg.sender.call.value(amount)()); // interaction after
+ }📝 Committable suggestion
‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.
| function withdraw(){ | |
| require(msg.sender.call.value(balances[msg.sender])()); | |
| balances[msg.sender] = 0; | |
| } | |
| function withdraw() { | |
| uint256 amount = balances[msg.sender]; | |
| require(amount > 0); | |
| balances[msg.sender] = 0; // effects first | |
| require(msg.sender.call.value(amount)()); // interaction after | |
| } |
🤖 Prompt for AI Agents
In audit_engine/smart_contracts/reentrancy/40749.sol around lines 6 to 9, the
withdraw function performs an external call before zeroing the sender's balance,
allowing reentrancy; change the logic to follow Checks-Effects-Interactions:
first require that balances[msg.sender] > 0, cache the amount to a local
variable, set balances[msg.sender] = 0, then perform the external transfer and
check its return value; alternatively use a reentrancy guard or the pull pattern
(allow owner to withdraw via a withdrawal queue) and avoid using raw
call.value() without proper checks.
Summary by CodeRabbit