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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/resolver"
"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, http *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
res := resolver.New(xeth)
// resolve host via HashReg/UrlHint Resolver
uri, hash, err := res.KeyToUrl(codehash)
if err != nil {
return
}
// get content via http client and authenticate content using hash
content, err = http.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
}
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