Issue 6

[Edward-Lo]

Description

The FlamingoSwapPairContract contract implements many functionalities for token-swap-pair. These interfaces will be called by FlamingoSwapRouterContract in many different scenarios.

For example. a user can claim his bonus after providing liquidity for a token-swap-pair by RemoveLiquidity function of FlamingoSwapRouterContract. It will first do some sanity checks, then transfer the liquidity token to the FlamingoSwapPairContract and calls Burn to remove the liquidity token and retrieve the tokens back and send them back to the user.

However, Burn is publicly avaiable, so an attacker can burn the liquidity token if someone mistakenly transfer it to the FlamingoSwapPairContract contract. There is a medium article by Dan Robinson thoroughly explains the concept and exploitation.

The same issue also applies to Mint and Swap.

Recommendation

Add permission checks for these functions.

[Ashuaidehao]

I'v add "Router WhiteList" for permission check, please help to check if it can resolve the problem. Thanks!

[Ashuaidehao]

Ralated Changes:

flamingo-contract-swap/Swap/flamingo-contract-swap/FlamingoSwapPair/FlamingoSwapPairContract.Nep5.cs

Line 77 in 90bdb87

Assert(CheckIsRouter(callscript), "Only support transfer to me by Router");

flamingo-contract-swap/Swap/flamingo-contract-swap/FlamingoSwapPair/FlamingoSwapPairContract.cs

Line 162 in 90bdb87

Assert(CheckIsRouter(msgSender), "Only Router Can Swap");

flamingo-contract-swap/Swap/flamingo-contract-swap/FlamingoSwapPair/FlamingoSwapPairContract.cs

Line 225 in 90bdb87

Assert(CheckIsRouter(msgSender),"Only Router Can Burn");

flamingo-contract-swap/Swap/flamingo-contract-swap/FlamingoSwapPair/FlamingoSwapPairContract.cs

Line 273 in 90bdb87

Assert(CheckIsRouter(msgSender), "Only Router Can Mint");

[Edward-Lo]

Ralated Changes:

flamingo-contract-swap/Swap/flamingo-contract-swap/FlamingoSwapPair/FlamingoSwapPairContract.Nep5.cs

Line 77 in 90bdb87

Assert(CheckIsRouter(callscript), "Only support transfer to me by Router");

flamingo-contract-swap/Swap/flamingo-contract-swap/FlamingoSwapPair/FlamingoSwapPairContract.cs

Line 162 in 90bdb87

Assert(CheckIsRouter(msgSender), "Only Router Can Swap");

flamingo-contract-swap/Swap/flamingo-contract-swap/FlamingoSwapPair/FlamingoSwapPairContract.cs

Line 225 in 90bdb87

Assert(CheckIsRouter(msgSender),"Only Router Can Burn");

flamingo-contract-swap/Swap/flamingo-contract-swap/FlamingoSwapPair/FlamingoSwapPairContract.cs

Line 273 in 90bdb87

Assert(CheckIsRouter(msgSender), "Only Router Can Mint");

I think these should do, LGTM