// Copyright 2019 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package fourbyte
import (
"bytes"
"errors"
"fmt"
"math/big"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/signer/core"
)
// ValidateTransaction does a number of checks on the supplied transaction, and
// returns either a list of warnings, or an error (indicating that the transaction
// should be immediately rejected).
func (db *Database) ValidateTransaction(selector *string, tx *core.SendTxArgs) (*core.ValidationMessages, error) {
messages := new(core.ValidationMessages)
// Prevent accidental erroneous usage of both 'input' and 'data' (show stopper)
if tx.Data != nil && tx.Input != nil && !bytes.Equal(*tx.Data, *tx.Input) {
return nil, errors.New(`ambiguous request: both "data" and "input" are set and are not identical`)
}
// Place data on 'data', and nil 'input'
var data []byte
if tx.Input != nil {
tx.Data = tx.Input
tx.Input = nil
}
if tx.Data != nil {
data = *tx.Data
}
// Contract creation doesn't validate call data, handle first
if tx.To == nil {
// Contract creation should contain sufficient data to deploy a contract. A
// typical error is omitting sender due to some quirk in the javascript call
// e.g. https://github.com/ethereum/go-ethereum/issues/16106.
if len(data) == 0 {
// Prevent sending ether into black hole (show stopper)
if tx.Value.ToInt().Cmp(big.NewInt(0)) > 0 {
return nil, errors.New("transaction will create a contract with value but empty code")
}
// No value submitted at least, critically Warn, but don't blow up
messages.Crit("Transaction will create a contract with empty code")
} else if len(data) < 40 { // arbitrary heuristic limit
messages.Warn(fmt.Sprintf("Transaction will create a contract, but the payload is suspiciously small (%d bytes)", len(data)))
}
// Method selector should be nil for contract creation
if selector != nil {
messages.Warn("Transaction will create a contract, but method selector supplied, indicating an intent to call a method")
}
return messages, nil
}
// Not a contract creation, validate as a plain transaction
if !tx.To.ValidChecksum() {
messages.Warn("Invalid checksum on recipient address")
}
if bytes.Equal(tx.To.Address().Bytes(), common.Address{}.Bytes()) {
messages.Crit("Transaction recipient is the zero address")
}
// Semantic fields validated, try to make heads or tails of the call data
db.validateCallData(selector, data, messages)
return messages, nil
}
// validateCallData checks if the ABI call-data + method selector (if given) can
// be parsed and seems to match.
func (db *Database) validateCallData(selector *string, data []byte, messages *core.ValidationMessages) {
// If the data is empty, we have a plain value transfer, nothing more to do
if len(data) == 0 {
return
}
// Validate the call data that it has the 4byte prefix and the rest divisible by 32 bytes
if len(data) < 4 {
messages.Warn("Transaction data is not valid ABI (missing the 4 byte call prefix)")
return
}
if n := len(data) - 4; n%32 != 0 {
messages.Warn(fmt.Sprintf("Transaction data is not valid ABI (length should be a multiple of 32 (was %d))", n))
}
// If a custom method selector was provided, validate with that
if selector != nil {
if info, err := verifySelector(*selector, data); err != nil {
messages.Warn(fmt.Sprintf("Transaction contains data, but provided ABI signature could not be matched: %v", err))
} else {
messages.Info(info.String())
db.AddSelector(*selector, data[:4])
}
return
}
// No method selector was provided, check the database for embedded ones
embedded, err := db.Selector(data[:4])
if err != nil {
messages.Warn(fmt.Sprintf("Transaction contains data, but the ABI signature could not be found: %v", err))
return
}
if info, err := verifySelector(embedded, data); err != nil {
messages.Warn(fmt.Sprintf("Transaction contains data, but provided ABI signature could not be varified: %v", err))
} else {
messages.Info(info.String())
}
}
