path: root/common/natspec/natspec.go

package natspec

import (
    "bytes"
    "encoding/json"
    "fmt"
    "github.com/robertkrimen/otto"
    "strings"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/common/docserver"
    "github.com/ethereum/go-ethereum/common/registrar"
    "github.com/ethereum/go-ethereum/crypto"
    "github.com/ethereum/go-ethereum/xeth"
)

type abi2method map[[8]byte]*method

type NatSpec struct {
    jsvm       *otto.Otto
    abiDocJson []byte
    userDoc    userDoc
    tx, data   string
}

// main entry point for to get natspec notice for a transaction
// the implementation is frontend friendly in that it always gives back
// a notice that is safe to display
// :FIXME: the second return value is an error, which can be used to fine-tune bahaviour
func GetNotice(xeth *xeth.XEth, tx string, http *docserver.DocServer) (notice string) {
    ns, err := New(xeth, tx, http)
    if err != nil {
        if ns == nil {
            return getFallbackNotice(fmt.Sprintf("no NatSpec info found for contract: %v", err), tx)
        } else {
            return getFallbackNotice(fmt.Sprintf("invalid NatSpec info: %v", err), tx)
        }
    }

    notice, err = ns.Notice()
    if err != nil {
        return getFallbackNotice(fmt.Sprintf("NatSpec notice error: %v", err), tx)
    }

    return
}

func getFallbackNotice(comment, tx string) string {
    return fmt.Sprintf("About to submit transaction (%s): %s", comment, tx)
}

type transaction struct {
    To   string `json:"to"`
    Data string `json:"data"`
}

type jsonTx struct {
    Params []transaction `json:"params"`
}

type contractInfo struct {
    Source        string          `json:"source"`
    Language      string          `json:"language"`
    Version       string          `json:"compilerVersion"`
    AbiDefinition json.RawMessage `json:"abiDefinition"`
    UserDoc       userDoc         `json:"userDoc"`
    DeveloperDoc  json.RawMessage `json:"developerDoc"`
}

func New(xeth *xeth.XEth, jsontx string, http *docserver.DocServer) (self *NatSpec, err error) {

    // extract contract address from tx
    var tx jsonTx
    err = json.Unmarshal([]byte(jsontx), &tx)
    if err != nil {
        return
    }
    t := tx.Params[0]
    contractAddress := t.To

    content, err := FetchDocsForContract(contractAddress, xeth, http)
    if err != nil {
        return
    }

    self, err = NewWithDocs(content, jsontx, t.Data)
    return
}

// also called by admin.contractInfo.get
func FetchDocsForContract(contractAddress string, xeth *xeth.XEth, ds *docserver.DocServer) (content []byte, err error) {
    // retrieve contract hash from state
    codehex := xeth.CodeAt(contractAddress)
    codeb := xeth.CodeAtBytes(contractAddress)

    if codehex == "0x" {
        err = fmt.Errorf("contract (%v) not found", contractAddress)
        return
    }
    codehash := common.BytesToHash(crypto.Sha3(codeb))
    // set up nameresolver with natspecreg + urlhint contract addresses
    reg := registrar.New(xeth)

    // resolve host via HashReg/UrlHint Resolver
    hash, err := reg.HashToHash(codehash)
    if err != nil {
        return
    }
    if ds.HasScheme("bzz") {
        content, err = ds.Get("bzz://"+hash.Hex()[2:], "")
        if err == nil { // non-fatal
            return
        }
        err = nil
        //falling back to urlhint
    }

    uri, err := reg.HashToUrl(hash)
    if err != nil {
        return
    }

    // get content via http client and authenticate content using hash
    content, err = ds.GetAuthContent(uri, hash)
    if err != nil {
        return
    }
    return
}

func NewWithDocs(infoDoc []byte, tx string, data string) (self *NatSpec, err error) {

    var contract contractInfo
    err = json.Unmarshal(infoDoc, &contract)
    if err != nil {
        return
    }

    self = &NatSpec{
        jsvm:       otto.New(),
        abiDocJson: []byte(contract.AbiDefinition),
        userDoc:    contract.UserDoc,
        tx:         tx,
        data:       data,
    }

    // load and require natspec js (but it is meant to be protected environment)
    _, err = self.jsvm.Run(natspecJS)
    if err != nil {
        return
    }
    _, err = self.jsvm.Run("var natspec = require('natspec');")
    return
}

// type abiDoc []method

// type method struct {
//  Name   string  `json:name`
//  Inputs []input `json:inputs`
//  abiKey [8]byte
// }

// type input struct {
//  Name string `json:name`
//  Type string `json:type`
// }

// json skeleton for abi doc (contract method definitions)
type method struct {
    Notice string `json:notice`
    name   string
}

type userDoc struct {
    Methods map[string]*method `json:methods`
}

func (self *NatSpec) makeAbi2method(abiKey [8]byte) (meth *method) {
    for signature, m := range self.userDoc.Methods {
        name := strings.Split(signature, "(")[0]
        hash := []byte(common.Bytes2Hex(crypto.Sha3([]byte(signature))))
        var key [8]byte
        copy(key[:], hash[:8])
        if bytes.Equal(key[:], abiKey[:]) {
            meth = m
            meth.name = name
            return
        }
    }
    return
}

func (self *NatSpec) Notice() (notice string, err error) {
    var abiKey [8]byte
    if len(self.data) < 10 {
        err = fmt.Errorf("Invalid transaction data")
        return
    }
    copy(abiKey[:], self.data[2:10])
    meth := self.makeAbi2method(abiKey)

    if meth == nil {
        err = fmt.Errorf("abi key does not match any method")
        return
    }
    notice, err = self.noticeForMethod(self.tx, meth.name, meth.Notice)
    return
}

func (self *NatSpec) noticeForMethod(tx string, name, expression string) (notice string, err error) {

    if _, err = self.jsvm.Run("var transaction = " + tx + ";"); err != nil {
        return "", fmt.Errorf("natspec.js error setting transaction: %v", err)
    }

    if _, err = self.jsvm.Run("var abi = " + string(self.abiDocJson) + ";"); err != nil {
        return "", fmt.Errorf("natspec.js error setting abi: %v", err)
    }

    if _, err = self.jsvm.Run("var method = '" + name + "';"); err != nil {
        return "", fmt.Errorf("natspec.js error setting method: %v", err)
    }

    if _, err = self.jsvm.Run("var expression = \"" + expression + "\";"); err != nil {
        return "", fmt.Errorf("natspec.js error setting expression: %v", err)
    }

    self.jsvm.Run("var call = {method: method,abi: abi,transaction: transaction};")
    value, err := self.jsvm.Run("natspec.evaluateExpression(expression, call);")
    if err != nil {
        return "", fmt.Errorf("natspec.js error evaluating expression: %v", err)
    }
    evalError := "Natspec evaluation failed, wrong input params"
    if value.String() == evalError {
        return "", fmt.Errorf("natspec.js error evaluating expression: wrong input params in expression '%s'", expression)
    }
    if len(value.String()) == 0 {
        return "", fmt.Errorf("natspec.js error evaluating expression")
    }

    return value.String(), nil

}