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Fixed CTM verifyTransfer bug #736

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merged 6 commits into from
Jul 8, 2019
Merged

Fixed CTM verifyTransfer bug #736

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0d541c1
Fixed CTM canTransferBug
maxsam4 Jul 3, 2019
994bdd5
Added test case
maxsam4 Jul 3, 2019
4753504
Merge branch 'dev-3.0.0' into ctm-canTransfer-fix
adamdossa Jul 3, 2019
9986f98
Merge branch 'dev-3.0.0' into ctm-canTransfer-fix
satyamakgec Jul 4, 2019
fdd421d
Merge branch 'dev-3.0.0' into ctm-canTransfer-fix
adamdossa Jul 5, 2019
5a5be38
Added comment for devs
maxsam4 Jul 8, 2019
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21 changes: 17 additions & 4 deletions contracts/modules/TransferManager/CTM/CountTransferManager.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -33,7 +33,7 @@ contract CountTransferManager is CountTransferManagerStorage, TransferManager {
external
returns(Result)
{
(Result success, ) = _verifyTransfer(_from, _to, _amount);
(Result success, ) = _verifyTransfer(_from, _to, _amount, securityToken.holderCount());
return success;
}

Expand All @@ -53,20 +53,33 @@ contract CountTransferManager is CountTransferManagerStorage, TransferManager {
view
returns(Result, bytes32)
{
return _verifyTransfer(_from, _to, _amount);
uint256 holderCount = securityToken.holderCount();
if (_amount != 0 && _from != _to) {
// Check whether receiver is a new token holder
if (_to != address(0) && securityToken.balanceOf(_to) == 0) {
holderCount++;
}
// Check whether sender is moving all of their tokens
if (_amount == securityToken.balanceOf(_from)) {
holderCount--;
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guard holderCount from over/underflows as it can be zero. See existing implementation in TokenLib.adjustInvestorCount.

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@tintinweb Since holderCount can only be incremented/decremented by one at a time, it can not be overflowed.

holderCount cannot be underflowed either since holderCount must be greater than 1 if _amount != 0 && _from != _to (checked on L57).

Earlier, we used SafeMath everywhere (including TokenLib.adjustInvestorCount) but lately, I have using SafeMath only where it is needed (for optimization).

Do you have a scenario in mind where holderCount can be underflowed or overflowed?

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thanks @maxsam4, agree the upper bound is unrealistic (especially when using ctm :)) and holderCount==0 with amount !=0 is mutually exclusive 👍

}
}

return _verifyTransfer(_from, _to, _amount, holderCount);
}

function _verifyTransfer(
address _from,
address _to,
uint256 _amount
uint256 _amount,
uint256 _holderCount
)
internal
view
returns(Result, bytes32)
{
if (!paused) {
if (maxHolderCount < securityToken.holderCount()) {
if (maxHolderCount < _holderCount) {
// Allow transfers to existing maxHolders
if (securityToken.balanceOf(_to) != 0 || securityToken.balanceOf(_from) == _amount) {
return (Result.NA, bytes32(0));
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3 changes: 3 additions & 0 deletions test/d_count_transfer_manager.js
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Original file line number Diff line number Diff line change
Expand Up @@ -311,6 +311,9 @@ contract("CountTransferManager", async (accounts) => {
);

await catchRevert(I_SecurityToken.issue(account_investor3, new BN(web3.utils.toWei("3", "ether")), "0x0", { from: token_owner }));
await catchRevert(I_SecurityToken.transfer(account_investor3, new BN(web3.utils.toWei("1", "ether")), { from: account_investor2 }));
let canTransfer = await I_SecurityToken.canTransfer(account_investor3, new BN(web3.utils.toWei("1", "ether")), "0x0", { from: account_investor2 });
assert.equal(canTransfer[0], "0x50"); //Transfer failure.
});

it("Should still be able to add to original token holders", async () => {
Expand Down