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// Copyright 2017 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 accounts
import (
"encoding/json"
"errors"
"fmt"
"math"
"math/big"
"strings"
)
// DefaultRootDerivationPath is the root path to which custom derivation endpoints
// are appended. As such, the first account will be at m/44'/60'/0'/0, the second
// at m/44'/60'/0'/1, etc.
var DefaultRootDerivationPath = DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0}
// DefaultBaseDerivationPath is the base path from which custom derivation endpoints
// are incremented. As such, the first account will be at m/44'/60'/0'/0/0, the second
// at m/44'/60'/0'/0/1, etc.
var DefaultBaseDerivationPath = DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0, 0}
// LegacyLedgerBaseDerivationPath is the legacy base path from which custom derivation
// endpoints are incremented. As such, the first account will be at m/44'/60'/0'/0, the
// second at m/44'/60'/0'/1, etc.
var LegacyLedgerBaseDerivationPath = DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0}
// DerivationPath represents the computer friendly version of a hierarchical
// deterministic wallet account derivaion path.
//
// The BIP-32 spec https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki
// defines derivation paths to be of the form:
//
// m / purpose' / coin_type' / account' / change / address_index
//
// The BIP-44 spec https://github.com/bitcoin/bips/blob/master/bip-0044.mediawiki
// defines that the `purpose` be 44' (or 0x8000002C) for crypto currencies, and
// SLIP-44 https://github.com/satoshilabs/slips/blob/master/slip-0044.md assigns
// the `coin_type` 60' (or 0x8000003C) to Ethereum.
//
// The root path for Ethereum is m/44'/60'/0'/0 according to the specification
// from https://github.com/ethereum/EIPs/issues/84, albeit it's not set in stone
// yet whether accounts should increment the last component or the children of
// that. We will go with the simpler approach of incrementing the last component.
type DerivationPath []uint32
// ParseDerivationPath converts a user specified derivation path string to the
// internal binary representation.
//
// Full derivation paths need to start with the `m/` prefix, relative derivation
// paths (which will get appended to the default root path) must not have prefixes
// in front of the first element. Whitespace is ignored.
func ParseDerivationPath(path string) (DerivationPath, error) {
var result DerivationPath
// Handle absolute or relative paths
components := strings.Split(path, "/")
switch {
case len(components) == 0:
return nil, errors.New("empty derivation path")
case strings.TrimSpace(components[0]) == "":
return nil, errors.New("ambiguous path: use 'm/' prefix for absolute paths, or no leading '/' for relative ones")
case strings.TrimSpace(components[0]) == "m":
components = components[1:]
default:
result = append(result, DefaultRootDerivationPath...)
}
// All remaining components are relative, append one by one
if len(components) == 0 {
return nil, errors.New("empty derivation path") // Empty relative paths
}
for _, component := range components {
// Ignore any user added whitespace
component = strings.TrimSpace(component)
var value uint32
// Handle hardened paths
if strings.HasSuffix(component, "'") {
value = 0x80000000
component = strings.TrimSpace(strings.TrimSuffix(component, "'"))
}
// Handle the non hardened component
bigval, ok := new(big.Int).SetString(component, 0)
if !ok {
return nil, fmt.Errorf("invalid component: %s", component)
}
max := math.MaxUint32 - value
if bigval.Sign() < 0 || bigval.Cmp(big.NewInt(int64(max))) > 0 {
if value == 0 {
return nil, fmt.Errorf("component %v out of allowed range [0, %d]", bigval, max)
}
return nil, fmt.Errorf("component %v out of allowed hardened range [0, %d]", bigval, max)
}
value += uint32(bigval.Uint64())
// Append and repeat
result = append(result, value)
}
return result, nil
}
// String implements the stringer interface, converting a binary derivation path
// to its canonical representation.
func (path DerivationPath) String() string {
result := "m"
for _, component := range path {
var hardened bool
if component >= 0x80000000 {
component -= 0x80000000
hardened = true
}
result = fmt.Sprintf("%s/%d", result, component)
if hardened {
result += "'"
}
}
return result
}
// MarshalJSON turns a derivation path into its json-serialized string
func (path DerivationPath) MarshalJSON() ([]byte, error) {
return json.Marshal(path.String())
}
// UnmarshalJSON a json-serialized string back into a derivation path
func (path *DerivationPath) UnmarshalJSON(b []byte) error {
var dp string
var err error
if err = json.Unmarshal(b, &dp); err != nil {
return err
}
*path, err = ParseDerivationPath(dp)
return err
}
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