Price oracle proxy to allow decoupling SAI/DAI

compound-finance · Apr 1, 2020 · eee83bc · eee83bc
1 parent afbe8a4
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diff --git a/contracts/PriceOracleProxy.sol b/contracts/PriceOracleProxy.sol
@@ -3,141 +3,104 @@ pragma solidity ^0.5.16;
 import "./CErc20.sol";
 import "./CToken.sol";
 import "./PriceOracle.sol";
-import "./Comptroller.sol";
-import "./SafeMath.sol";
 
 interface V1PriceOracleInterface {
     function assetPrices(address asset) external view returns (uint);
 }
 
 contract PriceOracleProxy is PriceOracle {
-    using SafeMath for uint256;
+    /// @notice Indicator that this is a PriceOracle contract (for inspection)
+    bool public constant isPriceOracle = true;
 
-    /**
-     * @notice The v1 price oracle, which will continue to serve prices for v1 assets
-     */
+    /// @notice The v1 price oracle, which will continue to serve prices for v1 assets
     V1PriceOracleInterface public v1PriceOracle;
 
-    /**
-     * @notice The comptroller which is used to white-list assets the proxy will price
-     * @dev Assets which are not white-listed will not be priced, to defend against abuse
-     */
-    Comptroller public comptroller;
+    /// @notice Address of the guardian, which may set the SAI price once
+    address public guardian;
 
-    /**
-     * @notice address of the cEther contract, which has a constant price
-     */
+    /// @notice Address of the cEther contract, which has a constant price
     address public cEthAddress;
 
-    /**
-     * @notice address of the cUSDC contract, which we hand pick a key for
-     */
+    /// @notice Address of the cUSDC contract, which we hand pick a key for
     address public cUsdcAddress;
 
-    /**
-     * @notice address of the cSAI contract, which we hand pick a key for
-     */
+    /// @notice Address of the cSAI contract, which we hand pick a key for
     address public cSaiAddress;
 
-    /**
-     * @notice address of the cDAI contract, which we peg to the SAI price
-     */
+    /// @notice Address of the cDAI contract, which we hand pick a key for
     address public cDaiAddress;
 
-    /**
-     * @notice address of the USDC contract, which we hand pick a key for
-     */
-    address constant usdcOracleKey = address(1);
-
-    /**
-     * @notice address of the SAI contract, which we hand pick a key for
-     */
-    address constant saiOracleKey = address(2);
+    /// @notice Handpicked key for USDC
+    address public constant usdcOracleKey = address(1);
 
-    /**
-     * @notice address of the asset which contains the USD/ETH price from Maker
-     */
-    address public makerUsdOracleKey;
+    /// @notice Handpicked key for DAI
+    address public constant daiOracleKey = address(2);
 
-    /**
-     * @notice Indicator that this is a PriceOracle contract (for inspection)
-     */
-    bool public constant isPriceOracle = true;
+    /// @notice Frozen SAI price (or 0 if not set yet)
+    uint public saiPrice;
 
     /**
-     * @param comptroller_ The address of the comptroller, which will be consulted for market listing status
+     * @param guardian_ The address of the guardian, which may set the SAI price once
      * @param v1PriceOracle_ The address of the v1 price oracle, which will continue to operate and hold prices for collateral assets
      * @param cEthAddress_ The address of cETH, which will return a constant 1e18, since all prices relative to ether
      * @param cUsdcAddress_ The address of cUSDC, which will be read from a special oracle key
-     * @param cSaiAddress_ The address of cSAI, which will be read from a special oracle key
-     * @param cDaiAddress_ The address of cDAI, which will be pegged to the SAI price
+     * @param cSaiAddress_ The address of cSAI, which will be read directly from storage
+     * @param cDaiAddress_ The address of cDAI, which will be read from a special oracle key
      */
-    constructor(address comptroller_,
+    constructor(address guardian_,
                 address v1PriceOracle_,
                 address cEthAddress_,
                 address cUsdcAddress_,
                 address cSaiAddress_,
                 address cDaiAddress_) public {
-        comptroller = Comptroller(comptroller_);
+        guardian = guardian_;
         v1PriceOracle = V1PriceOracleInterface(v1PriceOracle_);
 
         cEthAddress = cEthAddress_;
         cUsdcAddress = cUsdcAddress_;
         cSaiAddress = cSaiAddress_;
         cDaiAddress = cDaiAddress_;
-
-        if (cSaiAddress_ != address(0)) {
-            makerUsdOracleKey = CErc20(cSaiAddress_).underlying();
-        }
     }
 
     /**
      * @notice Get the underlying price of a listed cToken asset
      * @param cToken The cToken to get the underlying price of
-     * @return The underlying asset price mantissa (scaled by 1e18).
-     *  Zero means the price is unavailable.
+     * @return The underlying asset price mantissa (scaled by 1e18)
      */
     function getUnderlyingPrice(CToken cToken) public view returns (uint) {
         address cTokenAddress = address(cToken);
-        (bool isListed, ) = comptroller.markets(cTokenAddress);
-
-        if (!isListed) {
-            // not white-listed, worthless
-            return 0;
-        }
 
         if (cTokenAddress == cEthAddress) {
             // ether always worth 1
             return 1e18;
         }
 
         if (cTokenAddress == cUsdcAddress) {
-            // we assume USDC/USD = 1, and let DAI/ETH float based on the DAI/USDC ratio
-            //  use the maker usd price (for a token w/ 6 decimals)
-            return v1PriceOracle.assetPrices(makerUsdOracleKey).mul(1e12); // 1e(18 - 6)
+            return v1PriceOracle.assetPrices(usdcOracleKey);
         }
 
-        if (cTokenAddress == cSaiAddress || cTokenAddress == cDaiAddress) {
-            // check and bound the DAI/USDC posted price ratio
-            //  and use that to scale the maker price (for a token w/ 18 decimals)
-            uint makerUsdPrice = v1PriceOracle.assetPrices(makerUsdOracleKey);
-            uint postedUsdcPrice = v1PriceOracle.assetPrices(usdcOracleKey);
-            uint postedScaledDaiPrice = v1PriceOracle.assetPrices(saiOracleKey).mul(1e12);
-            uint daiUsdcRatio = postedScaledDaiPrice.mul(1e18).div(postedUsdcPrice);
-
-            if (daiUsdcRatio < 0.95e18) {
-                return makerUsdPrice.mul(0.95e18).div(1e18);
-            }
-
-            if (daiUsdcRatio > 1.05e18) {
-                return makerUsdPrice.mul(1.05e18).div(1e18);
-            }
+        if (cTokenAddress == cDaiAddress) {
+            return v1PriceOracle.assetPrices(daiOracleKey);
+        }
 
-            return makerUsdPrice.mul(daiUsdcRatio).div(1e18);
+        if (cTokenAddress == cSaiAddress) {
+            // use the frozen SAI price if set, otherwise use the DAI price
+            return saiPrice > 0 ? saiPrice : v1PriceOracle.assetPrices(daiOracleKey);
         }
 
         // otherwise just read from v1 oracle
         address underlying = CErc20(cTokenAddress).underlying();
         return v1PriceOracle.assetPrices(underlying);
     }
+
+    /**
+     * @notice Set the price of SAI, permanently
+     * @param price The price for SAI
+     */
+    function setSaiPrice(uint price) public {
+        require(msg.sender == guardian, "only guardian may set the SAI price");
+        require(saiPrice == 0, "SAI price may only be set once");
+        require(price < 0.1e18, "SAI price must be < 0.1 ETH");
+        saiPrice = price;
+    }
 }
diff --git a/networks/mainnet-abi.json b/networks/mainnet-abi.json
@@ -1941,7 +1941,7 @@
             "inputs": [
                 {
                     "internalType": "address",
-                    "name": "comptroller_",
+                    "name": "guardian_",
                     "type": "address"
                 },
                 {
@@ -2042,18 +2042,18 @@
         {
             "constant": true,
             "inputs": [],
-            "name": "comptroller",
+            "name": "daiOracleKey",
             "outputs": [
                 {
-                    "internalType": "contract Comptroller",
+                    "internalType": "address",
                     "name": "",
                     "type": "address"
                 }
             ],
             "payable": false,
             "stateMutability": "view",
             "type": "function",
-            "signature": "0x5fe3b567"
+            "signature": "0xe5ee0f6e"
         },
         {
             "constant": true,
@@ -2077,6 +2077,22 @@
             "type": "function",
             "signature": "0xfc57d4df"
         },
+        {
+            "constant": true,
+            "inputs": [],
+            "name": "guardian",
+            "outputs": [
+                {
+                    "internalType": "address",
+                    "name": "",
+                    "type": "address"
+                }
+            ],
+            "payable": false,
+            "stateMutability": "view",
+            "type": "function",
+            "signature": "0x452a9320"
+        },
         {
             "constant": true,
             "inputs": [],
@@ -2096,7 +2112,39 @@
         {
             "constant": true,
             "inputs": [],
-            "name": "makerUsdOracleKey",
+            "name": "saiPrice",
+            "outputs": [
+                {
+                    "internalType": "uint256",
+                    "name": "",
+                    "type": "uint256"
+                }
+            ],
+            "payable": false,
+            "stateMutability": "view",
+            "type": "function",
+            "signature": "0xa86b1944"
+        },
+        {
+            "constant": false,
+            "inputs": [
+                {
+                    "internalType": "uint256",
+                    "name": "price",
+                    "type": "uint256"
+                }
+            ],
+            "name": "setSaiPrice",
+            "outputs": [],
+            "payable": false,
+            "stateMutability": "nonpayable",
+            "type": "function",
+            "signature": "0xf9c99e9c"
+        },
+        {
+            "constant": true,
+            "inputs": [],
+            "name": "usdcOracleKey",
             "outputs": [
                 {
                     "internalType": "address",
@@ -2107,7 +2155,7 @@
             "payable": false,
             "stateMutability": "view",
             "type": "function",
-            "signature": "0xbc8a4ef4"
+            "signature": "0x3e76f255"
         },
         {
             "constant": true,

diff --git a/networks/mainnet.json b/networks/mainnet.json
@@ -3,7 +3,7 @@
         "ZRX": "0xE41d2489571d322189246DaFA5ebDe1F4699F498",
         "cUSDC": "0x39AA39c021dfbaE8faC545936693aC917d5E7563",
         "PriceOracle": "0x02557a5e05defeffd4cae6d83ea3d173b272c904",
-        "PriceOracleProxy": "0x1D8aEdc9E924730DD3f9641CDb4D1B92B848b4bd",
+        "PriceOracleProxy": "0xdA17fbEdA95222f331Cb1D252401F4b44F49f7A0",
         "Maximillion": "0xf859A1AD94BcF445A406B892eF0d3082f4174088",
         "GovernorAlpha": "0xc0dA01a04C3f3E0be433606045bB7017A7323E38",
         "cDAI": "0x5d3a536E4D6DbD6114cc1Ead35777bAB948E3643",
@@ -42,7 +42,7 @@
     "Blocks": {
         "cUSDC": 7710760,
         "PriceOracle": 6747538,
-        "PriceOracleProxy": 8983577,
+        "PriceOracleProxy": 9788084,
         "Maximillion": 7710775,
         "GovernorAlpha": 9601447,
         "cDAI": 8983575,
@@ -73,7 +73,7 @@
         "cUSDC": "0x39AA39c021dfbaE8faC545936693aC917d5E7563",
         "cSAI": "0xF5DCe57282A584D2746FaF1593d3121Fcac444dC",
         "cDAI": "0x5d3a536E4D6DbD6114cc1Ead35777bAB948E3643",
-        "address": "0x1D8aEdc9E924730DD3f9641CDb4D1B92B848b4bd"
+        "address": "0xdA17fbEdA95222f331Cb1D252401F4b44F49f7A0"
     },
     "Maximillion": {
         "description": "Maximillion",
@@ -136,7 +136,7 @@
     },
     "Constructors": {
         "cUSDC": "0x000000000000000000000000a0b86991c6218b36c1d19d4a2e9eb0ce3606eb480000000000000000000000003d9819210a31b4961b30ef54be2aed79b9c9cd3b000000000000000000000000c64c4cba055efa614ce01f4bad8a9f519c4f8fab0000000000000000000000000000000000000000000000000000b5e620f4800000000000000000000000000000000000000000000000000000000000000000e0000000000000000000000000000000000000000000000000000000000000012000000000000000000000000000000000000000000000000000000000000000080000000000000000000000000000000000000000000000000000000000000011436f6d706f756e642055534420436f696e00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000056355534443000000000000000000000000000000000000000000000000000000",
-        "PriceOracleProxy": "0x0000000000000000000000003d9819210a31b4961b30ef54be2aed79b9c9cd3b00000000000000000000000002557a5e05defeffd4cae6d83ea3d173b272c9040000000000000000000000004ddc2d193948926d02f9b1fe9e1daa0718270ed500000000000000000000000039aa39c021dfbae8fac545936693ac917d5e7563000000000000000000000000f5dce57282a584d2746faf1593d3121fcac444dc0000000000000000000000005d3a536e4d6dbd6114cc1ead35777bab948e3643",
+        "PriceOracleProxy": "0x0000000000000000000000008b8592e9570e96166336603a1b4bd1e8db20fa2000000000000000000000000002557a5e05defeffd4cae6d83ea3d173b272c9040000000000000000000000004ddc2d193948926d02f9b1fe9e1daa0718270ed500000000000000000000000039aa39c021dfbae8fac545936693ac917d5e7563000000000000000000000000f5dce57282a584d2746faf1593d3121fcac444dc0000000000000000000000005d3a536e4d6dbd6114cc1ead35777bab948e3643",
         "Maximillion": "0x0000000000000000000000004ddc2d193948926d02f9b1fe9e1daa0718270ed5",
         "GovernorAlpha": "0x0000000000000000000000006d903f6003cca6255d85cca4d3b5e5146dc33925000000000000000000000000c00e94cb662c3520282e6f5717214004a7f268880000000000000000000000008b8592e9570e96166336603a1b4bd1e8db20fa20",
         "cDAI": "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",

diff --git a/scenario/src/Builder/PriceOracleProxyBuilder.ts b/scenario/src/Builder/PriceOracleProxyBuilder.ts
@@ -22,24 +22,24 @@ export interface PriceOracleProxyData {
 
 export async function buildPriceOracleProxy(world: World, from: string, event: Event): Promise<{world: World, priceOracleProxy: PriceOracleProxy, invokation: Invokation<PriceOracleProxy>}> {
   const fetchers = [
-    new Fetcher<{comptroller: AddressV, priceOracle: AddressV, cETH: AddressV, cUSDC: AddressV, cSAI: AddressV, cDAI: AddressV}, PriceOracleProxyData>(`
+    new Fetcher<{guardian: AddressV, priceOracle: AddressV, cETH: AddressV, cUSDC: AddressV, cSAI: AddressV, cDAI: AddressV}, PriceOracleProxyData>(`
         #### Price Oracle Proxy
 
-        * "Deploy <Comptroller:Address> <PriceOracle:Address> <cETH:Address> <cUSDC:Address> <cSAI:Address> <cDAI:Address>" - The Price Oracle which proxies to a backing oracle
+        * "Deploy <Guardian:Address> <PriceOracle:Address> <cETH:Address> <cUSDC:Address> <cSAI:Address> <cDAI:Address>" - The Price Oracle which proxies to a backing oracle
         * E.g. "PriceOracleProxy Deploy (Unitroller Address) (PriceOracle Address) cETH cUSDC cSAI cDAI"
       `,
       "PriceOracleProxy",
       [
-        new Arg("comptroller", getAddressV),
+        new Arg("guardian", getAddressV),
         new Arg("priceOracle", getAddressV),
         new Arg("cETH", getAddressV),
         new Arg("cUSDC", getAddressV),
         new Arg("cSAI", getAddressV),
         new Arg("cDAI", getAddressV)
       ],
-      async (world, {comptroller, priceOracle, cETH, cUSDC, cSAI, cDAI}) => {
+      async (world, {guardian, priceOracle, cETH, cUSDC, cSAI, cDAI}) => {
         return {
-          invokation: await PriceOracleProxyContract.deploy<PriceOracleProxy>(world, from, [comptroller.val, priceOracle.val, cETH.val, cUSDC.val, cSAI.val, cDAI.val]),
+          invokation: await PriceOracleProxyContract.deploy<PriceOracleProxy>(world, from, [guardian.val, priceOracle.val, cETH.val, cUSDC.val, cSAI.val, cDAI.val]),
           description: "Price Oracle Proxy",
           cETH: cETH.val,
           cUSDC: cUSDC.val,

diff --git a/scenario/src/Contract/PriceOracleProxy.ts b/scenario/src/Contract/PriceOracleProxy.ts
@@ -1,9 +1,11 @@
 import {Contract} from '../Contract';
 import {Callable, Sendable} from '../Invokation';
+import {encodedNumber} from '../Encoding';
 
 interface PriceOracleProxyMethods {
   getUnderlyingPrice(asset: string): Callable<number>
   v1PriceOracle(): Callable<string>;
+  setSaiPrice(amount: encodedNumber): Sendable<number>
 }
 
 export interface PriceOracleProxy extends Contract {

diff --git a/scenario/src/Event/PriceOracleProxyEvent.ts b/scenario/src/Event/PriceOracleProxyEvent.ts
@@ -45,6 +45,14 @@ async function verifyPriceOracleProxy(world: World, priceOracleProxy: PriceOracl
   return world;
 }
 
+async function setSaiPrice(world: World, from: string, priceOracleProxy: PriceOracleProxy, amount: NumberV): Promise<World> {
+  return addAction(
+    world,
+    `Set price oracle SAI price to ${amount.show()}`,
+    await invoke(world, priceOracleProxy.methods.setSaiPrice(amount.encode()), from)
+  );
+}
+
 export function priceOracleProxyCommands() {
   return [
     new Command<{params: EventV}>(`
@@ -73,6 +81,20 @@ export function priceOracleProxyCommands() {
         new Arg("contractName", getStringV, {default: new StringV("PriceOracleProxy")})
       ],
       (world, {priceOracleProxy, apiKey, contractName}) => verifyPriceOracleProxy(world, priceOracleProxy, apiKey.val, contractName.val)
+    ),
+
+    new Command<{priceOracleProxy: PriceOracleProxy, amount: NumberV}>(`
+        #### SetSaiPrice
+
+        * "SetSaiPrice <Amount>" - Sets the per-ether price for SAI
+          * E.g. "PriceOracleProxy SetSaiPrice 1.0"
+      `,
+      "SetSaiPrice",
+      [
+        new Arg("priceOracleProxy", getPriceOracleProxy, {implicit: true}),
+        new Arg("amount", getExpNumberV)
+      ],
+      (world, from, {priceOracleProxy, amount}) => setSaiPrice(world, from, priceOracleProxy, amount)
     )
   ];
 }