---
# System prepended metadata

title: '\[GNO\] ERC20 Token Smart Contract Technical Assessment'

---

# \[GNO\] ERC20 Token Smart Contract Technical Assessment

## General Information

- **Symbol** : GNO
- **Address(es)**:
  - `GnosisToken`: [`0x6810e776880C02933D47DB1b9fc05908e5386b96`](https://etherscan.io/address/0x6810e776880c02933d47db1b9fc05908e5386b96)
  - `DutchAuction`<sup>[2]</sup>: [`0x1d0DcC8d8BcaFa8e8502BEaEeF6CBD49d3AFFCDC`](https://etherscan.io/address/0x1d0DcC8d8BcaFa8e8502BEaEeF6CBD49d3AFFCDC)
- **Deployment date**:
  - `GnosisToken`: [Apr-18-2017 01:45:16 PM +UTC](https://etherscan.io/tx/0xa7838a091c7daa3033ec59a3f13bd8dc5b4c69d3b3ab33f486d06faae72a1606)
  - `DutchAuction`<sup>[1]</sup>: [Apr-18-2017 01:42:10 PM +UTC](https://etherscan.io/tx/0x4dbf95eb08cde01d46fcc0916c2da4adb7cd12eed473ec96f6dbe2ba6054a417)  
- **Total supply**: $10,000,000$
- **Developers allotment**: $1,000,000$
- **Collateral onboarding application**: [\[GNO\] MIP6 Collateral Onboarding Application - GnosisDAO](https://forum.makerdao.com/t/gno-mip6-collateral-onboarding-application-gnosisdao/17321)
- **Project website**: [Gnosis](https://gnosis.pm)
- **Project whitepaper**: N/A
- **Github repository**:
  - GnosisToken: [`gno-token`](https://github.com/gnosis/gno-token)<sup>[2]</sup>
- **Can use existing MCD collateral type adapter?**  
  Yes, we can use the original [`GemJoin`](https://github.com/makerdao/dss/blob/master/src/join.sol#L66-L121) adapter.

---

<sup>[1]</sup> The `DutchAuction` smart contract is only listed for completeness, since it is referenced by the `GnosisToken` (no interactions, only to set its balance), but it is not part of this assessment, as it does not hold a significant amount of GNO as of this writing.

<sup>[2]</sup> The deployed `GnosisToken` contract verified on [Etherscan](https://etherscan.io/address/0x6810e776880c02933d47db1b9fc05908e5386b96#code) differs from [all revisions](https://github.com/gnosis/gno-token/commits/master/contracts/TokenGNO.sol) that can be found in the Github repository. The `DutchAuction` smart contract could not be found on Gnosis Github.

## Risk Summary

-   **Does the contract implement the ERC20 token standards?** Yes.
-   **Risk analysis** : LOW.

## Technical Information

- **Compiler version** : `v0.4.10+commit.f0d539ae`
- **Decimals** : $18$
- **Overflow checks** : Yes, where there are practical implications. See notes below.
- **Mitigation against allowance race-condition** : No.
- **Upgradeable contract patterns** : No.
- **Access control or restriction lists** : No.
- **Non-standard features or behaviors** : No.

## Formal Verification Considerations:

- **Does `transfer` have simple semantics?** Yes.
- **Does `transferFrom` have simple semantics?** Yes.
- **Can balances be arbitrarily modified by some actor?** No.
- **Are there any external calls?** No.

## Testnet Information

GNO is only deployed to now deprecated testnets:

- **Rinkeby**: [https://rinkeby.etherscan.io/token/0xd0dab4e640d95e9e8a47545598c33e31bdb53c7c](https://rinkeby.etherscan.io/token/0xd0dab4e640d95e9e8a47545598c33e31bdb53c7c)
- **Kovan**: [https://kovan.etherscan.io/token/0x6018bf616ec9db02f90c8c8529ddadc10a5c29dc](https://kovan.etherscan.io/token/0x6018bf616ec9db02f90c8c8529ddadc10a5c29dc)

## Contract Logic Summary<sup>[3]</sup>

GNO is a straightforward implementation of the ERC20 standard.

There is a simple inheritance structure (see below) and it does not interact with any external contract.

The total supply is fixed and set to $10,000,000$ in the constructor. There is no possible way to modify it.

From those $10,000,000$, exactly $9,000,000$ (90%) was auctioned and $1,000,000$ (10%) was pre-allocated like described bellow:

```
-----Decoded View---------------
Arg [1] : owners (address[]): [
  0x1d805bC00b8fa3c96aE6C8FA97B2FD24B19a9801,
  0x5210c4dCd7eb899a1274Fd6471AdeC9896ae05AA,
  0x9F7dfAb2222A473284205cdDF08a677726d786A0,
  0x6750adBb477d0310f395DA2AD93abE4B9bfd1c87,
  0x31CbA7aD3483F9BFF236DF556E1C3695736a9615,
  0xFc36387AfdbA73d4532AF724eE04d94992E8A2E8,
  0x9EE585a6C270Fd8b046A5b2019fdac86544bcA61,
  0xD8dD5d51eFEA7108C2D2e663F4520FE4715056C0,
  0xC0754d0A5cb5B25d452be07165180eF331A3241A,
  0x9F7dfAb2222A473284205cdDF08a677726d786A0
]
Arg [2] : tokens (uint256[]): [
  400000000000000000000000,
  50000000000000000000000,
  50000000000000000000000,
  15000000000000000000000,
  10000000000000000000000,
  150000000000000000000000,
  150000000000000000000000,
  45000000000000000000000,
  30000000000000000000000,
  100000000000000000000000
]
```
<sub>The parameters above were extracted from the constructor arguments in the transaction that created the contract. Keep in mind that the values in `tokens` include the 18 decimals for GNO. For instance $400000000000000000000000$ is actually $400,000$ GNO.</sub>

Regarding overflow/underflow checks, the contracts have tactical inline checks (no `SafeMath`-like library) for underflows, but it does not check for overflows.

Since the token supply is fixed at $10,000,000$ and GNO has $18$ decimals, the maximum amount the contract needs to be able to handle is $10^{25}$, which can safely fit into $84$ bits, meaning that variables of type  `uint256` **would never overflow**.

---

<sup>[3]</sup> Comments in this section refers to the actual deployed GNO smart contract as it can be seen on [Etherscan](https://etherscan.io/address/0x6810e776880c02933d47db1b9fc05908e5386b96#code).

## Supporting Materials

### Architecture Diagram

![GNO Architecture Diagram](https://i.imgur.com/wVSQrSW.png)

### Inheritance Diagram

![GNO Inheritance Diagram](https://i.imgur.com/zEV24DY.png)

### ABI Description

```rust
+  Token 
    - [Pub] transfer #
    - [Pub] transferFrom #
    - [Pub] approve #
    - [Pub] totalSupply
    - [Pub] balanceOf
    - [Pub] allowance

 +  StandardToken (Token)
    - [Pub] transfer #
    - [Pub] transferFrom #
    - [Pub] approve #
    - [Pub] allowance
    - [Pub] balanceOf

 +  GnosisToken (StandardToken)
    - [Pub] <Constructor> #


 ($) = payable function
 # = non-constant function
```

### Sūrya's Description Report (tool: [`surya`](https://github.com/consensys/surya))

#### Files Description Table


| File Name       | SHA-1 Hash                               |
| -------------   | --------------                           |
| GnosisToken.sol | 50bf6e27d99041cdb8a43b6c0729c73e8a583a10 |


#### Contracts Description Table


| Contract          | Type                  | Bases              |                    |                   |
| :----------:      | :-------------------: | :----------------: | :----------------: | :---------------: |
| └                 | **Function Name**     | **Visibility**     | **Mutability**     | **Modifiers**     |
|                   |                       |                    |                    |                   |
| **Token**         | Implementation        |                    |                    |                   |
| └                 | transfer              | Public ❗️          | 🛑                 | NO❗️              |
| └                 | transferFrom          | Public ❗️          | 🛑                 | NO❗️              |
| └                 | approve               | Public ❗️          | 🛑                 | NO❗️              |
| └                 | totalSupply           | Public ❗️          |                    | NO❗️              |
| └                 | balanceOf             | Public ❗️          |                    | NO❗️              |
| └                 | allowance             | Public ❗️          |                    | NO❗️              |
|                   |                       |                    |                    |                   |
| **StandardToken** | Implementation        | Token              |                    |                   |
| └                 | transfer              | Public ❗️          | 🛑                 | NO❗️              |
| └                 | transferFrom          | Public ❗️          | 🛑                 | NO❗️              |
| └                 | approve               | Public ❗️          | 🛑                 | NO❗️              |
| └                 | allowance             | Public ❗️          |                    | NO❗️              |
| └                 | balanceOf             | Public ❗️          |                    | NO❗️              |
|                   |                       |                    |                    |                   |
| **GnosisToken**   | Implementation        | StandardToken      |                    |                   |
| └                 | &lt;Constructor&gt;   | Public ❗️          | 🛑                 | NO❗️              |


#### Legend

| Symbol     | Meaning                   |
| :--------: | -----------               |
| 🛑         | Function can modify state |
| 💵         | Function is payable       |

### Slither Report (tool: [`slither`](https://github.com/crytic/slither))

```
Deprecated standard detected THROW ():
	- Usage of "throw" should be replaced with "revert()"
Reference: https://github.com/crytic/slither/wiki/Detector-Documentation#deprecated-standards

Pragma version0.4.10 () allows old versions
solc-0.4.10 is not recommended for deployment
Reference: https://github.com/crytic/slither/wiki/Detector-Documentation#incorrect-versions-of-solidity

Parameter StandardToken.transfer(address,uint256)._to () is not in mixedCase
Parameter StandardToken.transfer(address,uint256)._value () is not in mixedCase
Parameter StandardToken.transferFrom(address,address,uint256)._from () is not in mixedCase
Parameter StandardToken.transferFrom(address,address,uint256)._to () is not in mixedCase
Parameter StandardToken.transferFrom(address,address,uint256)._value () is not in mixedCase
Parameter StandardToken.approve(address,uint256)._spender () is not in mixedCase
Parameter StandardToken.approve(address,uint256)._value () is not in mixedCase
Parameter StandardToken.allowance(address,address)._owner () is not in mixedCase
Parameter StandardToken.allowance(address,address)._spender () is not in mixedCase
Parameter StandardToken.balanceOf(address)._owner () is not in mixedCase
Reference: https://github.com/crytic/slither/wiki/Detector-Documentation#conformance-to-solidity-naming-conventions

GnosisToken.GnosisToken(address,address[],uint256[]) () uses literals with too many digits:
	- totalSupply = 10000000 * 10 ** 18 ()
GnosisToken.GnosisToken(address,address[],uint256[]) () uses literals with too many digits:
	- balances[dutchAuction] = 9000000 * 10 ** 18 ()
Reference: https://github.com/crytic/slither/wiki/Detector-Documentation#too-many-digits

ERC20 event TokenTransfer(address,address,uint256) ()does not index parameter from
ERC20 event TokenTransfer(address,address,uint256) ()does not index parameter to
ERC20 event TokenApproval(address,address,uint256) ()does not index parameter owner
ERC20 event TokenApproval(address,address,uint256) ()does not index parameter spender
Reference: https://github.com/crytic/slither/wiki/Detector-Documentation#unindexed-erc20-event-parameters

GnosisToken.name () is never used in GnosisToken ()
GnosisToken.symbol () is never used in GnosisToken ()
GnosisToken.decimals () is never used in GnosisToken ()
Reference: https://github.com/crytic/slither/wiki/Detector-Documentation#unused-state-variable

GnosisToken.decimals () should be constant
GnosisToken.name () should be constant
GnosisToken.symbol () should be constant
Reference: https://github.com/crytic/slither/wiki/Detector-Documentation#state-variables-that-could-be-declared-constant

transfer(address,uint256) should be declared external:
	- StandardToken.transfer(address,uint256) ()
	- Token.transfer(address,uint256) ()
transferFrom(address,address,uint256) should be declared external:
	- StandardToken.transferFrom(address,address,uint256) ()
	- Token.transferFrom(address,address,uint256) ()
approve(address,uint256) should be declared external:
	- StandardToken.approve(address,uint256) ()
	- Token.approve(address,uint256) ()
totalSupply() should be declared external:
	- Token.totalSupply() ()
balanceOf(address) should be declared external:
	- StandardToken.balanceOf(address) ()
	- Token.balanceOf(address) ()
allowance(address,address) should be declared external:
	- StandardToken.allowance(address,address) ()
	- Token.allowance(address,address) ()
Reference: https://github.com/crytic/slither/wiki/Detector-Documentation#public-function-that-could-be-declared-external
contracts/GnosisToken.sol analyzed (3 contracts with 78 detectors), 31 result(s) found
```