Add GetCoinbase precompiled contract (ethereum#58)

* Modify geth for single commit verification with GetMinerOf precompiled contract

* Fix references

* Add comment for empty address behavior

* Rename to GetCoinbase

* Fix comment

* Rename to RequestIndex

abe/abe.go

@@ -54,7 +54,7 @@ func createVerificationMessage(request types.VerificationRequest, verificationRe
 	if err != nil {
 		return "", err
 	}
-	return fmt.Sprintf("Celo verification code: %s:%d:%s", base64.URLEncoding.EncodeToString(signature), request.VerificationIndex, base64.URLEncoding.EncodeToString(verificationRewardsAddress.Bytes())), nil
+	return fmt.Sprintf("Celo verification code: %s:%d:%d:%s", base64.URLEncoding.EncodeToString(signature), request.RequestIndex, request.VerificationIndex, base64.URLEncoding.EncodeToString(verificationRewardsAddress.Bytes())), nil
 }
 
 func sendSms(phoneNumber string, message string, account common.Address, verificationServiceURL string) error {
@@ -91,7 +91,6 @@ func SendVerificationMessages(receipts []*types.Receipt, block *types.Block, coi
 				log.Error("[Celo] Failed to decrypt phone number", "err", err)
 				continue
 			}
-			log.Debug(fmt.Sprintf("[Celo] Phone number %s requesting verification", phoneNumber))
 
 			message, err := createVerificationMessage(request, verificationRewardsAddress, account, wallet)
 			if err != nil {

core/evm.go

@@ -48,6 +48,7 @@ func NewEVMContext(msg Message, header *types.Header, chain ChainContext, author
 		CanTransfer: CanTransfer,
 		Transfer:    Transfer,
 		GetHash:     GetHashFn(header, chain),
+		GetCoinbase: GetCoinbaseFn(header, chain),
 		Origin:      msg.From(),
 		Coinbase:    beneficiary,
 		BlockNumber: new(big.Int).Set(header.Number),
@@ -84,6 +85,34 @@ func GetHashFn(ref *types.Header, chain ChainContext) func(n uint64) common.Hash
 	}
 }
 
+// GetCoinbaseFn returns a GetCoinbaseFunc which retrieves the coinbase by block number
+func GetCoinbaseFn(ref *types.Header, chain ChainContext) func(n uint64) common.Address {
+	var cache map[uint64]common.Address
+
+	return func(n uint64) common.Address {
+		// If there's no address cache yet, make one
+		if cache == nil {
+			cache = map[uint64]common.Address{
+				ref.Number.Uint64(): ref.Coinbase,
+			}
+		}
+		// Try to fulfill the request from the cache
+		if address, ok := cache[n]; ok {
+			return address
+		}
+		// Not cached, iterate the blocks and cache the addresses
+		for header := chain.GetHeader(ref.ParentHash, ref.Number.Uint64()-1); header != nil; header = chain.GetHeader(header.ParentHash, header.Number.Uint64()-1) {
+			cache[header.Number.Uint64()] = header.Coinbase
+			if n == header.Number.Uint64() {
+				return header.Coinbase
+			}
+		}
+
+		// Like GetHashFn we'll just return an empty address if we can't find it
+		return common.Address{}
+	}
+}
+
 // CanTransfer checks whether there are enough funds in the address' account to make a transfer.
 // This does not take the necessary gas in to account to make the transfer valid.
 func CanTransfer(db vm.StateDB, addr common.Address, amount *big.Int) bool {

core/types/receipt.go

@@ -47,9 +47,10 @@ const (
 // VerificationRequest represents a request for verification in the Celo ABE protocol.
 type VerificationRequest struct {
 	PhoneHash         common.Hash
+	CodeHash          common.Hash
 	Account           common.Address
+	RequestIndex      *big.Int
 	VerificationIndex *big.Int
-	CodeHash          common.Hash
 	Verifier          common.Address
 	EncryptedPhone    hexutil.Bytes
 }
@@ -111,25 +112,31 @@ func NewReceipt(root []byte, failed bool, cumulativeGasUsed uint64) *Receipt {
 // Decode a VerificationRequest from raw input bytes.
 // Input is expected to be encoded in the following manner:
 // input[0:32]:  bytes32 phoneHash
-// input[32:64]: address account
-// input[64:96]: bytes32 verificationIndex
-// input[96:128]: bytes32 codeHash
-// input[128:160]: address verifier
-// input[160:]    bytes encryptedPhone
+// input[32:64]: bytes32 codeHash
+// input[64:96]: address account
+// input[96:128]: bytes32 requestIndex
+// input[128:160]: bytes32 verificationIndex
+// input[160:192]: address verifier
+// input[192:]:    bytes encryptedPhone
 func DecodeVerificationRequest(input []byte) (VerificationRequest, error) {
 	var v VerificationRequest
 	v.PhoneHash = common.BytesToHash(input[0:32])
-	v.Account = common.BytesToAddress(input[32:64])
+	v.Account = common.BytesToAddress(input[64:96])
 	var parsed bool
-	v.VerificationIndex, parsed = math.ParseBig256(hexutil.Encode(input[64:96]))
+	v.RequestIndex, parsed = math.ParseBig256(hexutil.Encode(input[96:128]))
 	if !parsed {
-		return v, fmt.Errorf("Error parsing VerificationRequest: unable to parse VerificationIndex from " + hexutil.Encode(input[64:96]))
+		return v, fmt.Errorf("Error parsing VerificationRequest: unable to parse RequestIndex from " + hexutil.Encode(input[96:128]))
 	}
-	v.CodeHash = common.BytesToHash(input[96:128])
-	v.Verifier = common.BytesToAddress(input[128:160])
+	v.VerificationIndex, parsed = math.ParseBig256(hexutil.Encode(input[128:160]))
+	if !parsed {
+		return v, fmt.Errorf("Error parsing VerificationRequest: unable to parse VerificationIndex from " + hexutil.Encode(input[128:160]))
+	}
+
+	v.CodeHash = common.BytesToHash(input[32:64])
+	v.Verifier = common.BytesToAddress(input[160:192])
 
 	// TODO(asa): Consider validating the length of EncryptedPhone
-	v.EncryptedPhone = input[160:]
+	v.EncryptedPhone = input[192:]
 	return v, nil
 }
 

core/vm/contracts.go

@@ -52,6 +52,7 @@ var PrecompiledContractsHomestead = map[common.Address]PrecompiledContract{
 
 var CeloPrecompiledContractsAddressOffset = byte(0xff)
 var requestVerificationAddress = common.BytesToAddress(append([]byte{0}, CeloPrecompiledContractsAddressOffset))
+var getCoinbaseAddress = common.BytesToAddress(append([]byte{0}, (CeloPrecompiledContractsAddressOffset - 1)))
 var transferAddress = common.BytesToAddress(append([]byte{0}, (CeloPrecompiledContractsAddressOffset - 2)))
 
 // PrecompiledContractsByzantium contains the default set of pre-compiled Ethereum
@@ -68,6 +69,7 @@ var PrecompiledContractsByzantium = map[common.Address]PrecompiledContract{
 
 	// Celo Precompiled Contracts
 	requestVerificationAddress: &requestVerification{},
+	getCoinbaseAddress:         &getCoinbase{},
 	transferAddress:            &transfer{},
 }
 
@@ -391,6 +393,23 @@ func (c *requestVerification) Run(input []byte, evm *EVM) ([]byte, error) {
 	}
 }
 
+type getCoinbase struct{}
+
+func (c *getCoinbase) RequiredGas(input []byte) uint64 {
+	return params.GetCoinbaseGas
+}
+
+func (c *getCoinbase) Run(input []byte, evm *EVM) ([]byte, error) {
+	var blockNumber, parsingSuccess = math.ParseBig256(hexutil.Encode(input[0:32]))
+
+	if !parsingSuccess {
+		return input, fmt.Errorf("Error parsing block number:" + hexutil.Encode(input[0:32]))
+	}
+
+	var coinbase = evm.Context.GetCoinbase(blockNumber.Uint64())
+	return coinbase.Bytes(), nil
+}
+
 // Native transfer contract to make Celo Gold ERC20 compatible.
 type transfer struct{}
 

core/vm/evm.go

@@ -39,6 +39,9 @@ type (
 	// GetHashFunc returns the nth block hash in the blockchain
 	// and is used by the BLOCKHASH EVM op code.
 	GetHashFunc func(uint64) common.Hash
+	// GetCoinbaseFunc returns the nth block coinbase in the blockchain
+	// and is used by the Celo Precompiled Contract.
+	GetCoinbaseFunc func(uint64) common.Address
 )
 
 // run runs the given contract and takes care of running precompiles with a fallback to the byte code interpreter.
@@ -78,6 +81,8 @@ type Context struct {
 	Transfer TransferFunc
 	// GetHash returns the hash corresponding to n
 	GetHash GetHashFunc
+	// GetCoinbase returns the coinbase corresponding to n
+	GetCoinbase GetCoinbaseFunc
 
 	// Message information
 	Origin   common.Address // Provides information for ORIGIN

params/protocol_params.go

@@ -89,6 +89,7 @@ const (
 	// Celo precompiled contracts
 	// TODO(asa): Figure out what the actual gas cost of this contract should be.
 	VerificationRequestGas uint64 = 3000 // Per-message price for sending an SMS. Not an accurate representation of the real cost of sending an SMS.
+	GetCoinbaseGas         uint64 = 20   // Equivalent to the cost of the BLOCKHASH op
 )
 
 var (