131 lines
4.7 KiB
Go
131 lines
4.7 KiB
Go
// Copyright 2017 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package accounts
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import (
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"errors"
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"fmt"
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"math"
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"math/big"
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"strings"
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)
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// DefaultRootDerivationPath is the root path to which custom derivation endpoints
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// are appended. As such, the first account will be at m/44'/60'/0'/0, the second
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// at m/44'/60'/0'/1, etc.
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var DefaultRootDerivationPath = DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0}
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// DefaultBaseDerivationPath is the base path from which custom derivation endpoints
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// are incremented. As such, the first account will be at m/44'/60'/0'/0, the second
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// at m/44'/60'/0'/1, etc.
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var DefaultBaseDerivationPath = DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0}
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// DerivationPath represents the computer friendly version of a hierarchical
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// deterministic wallet account derivaion path.
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//
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// The BIP-32 spec https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki
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// defines derivation paths to be of the form:
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//
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// m / purpose' / coin_type' / account' / change / address_index
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//
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// The BIP-44 spec https://github.com/bitcoin/bips/blob/master/bip-0044.mediawiki
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// defines that the `purpose` be 44' (or 0x8000002C) for crypto currencies, and
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// SLIP-44 https://github.com/satoshilabs/slips/blob/master/slip-0044.md assigns
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// the `coin_type` 60' (or 0x8000003C) to Ethereum.
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//
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// The root path for Ethereum is m/44'/60'/0'/0 according to the specification
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// from https://github.com/ethereum/EIPs/issues/84, albeit it's not set in stone
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// yet whether accounts should increment the last component or the children of
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// that. We will go with the simpler approach of incrementing the last component.
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type DerivationPath []uint32
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// ParseDerivationPath converts a user specified derivation path string to the
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// internal binary representation.
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//
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// Full derivation paths need to start with the `m/` prefix, relative derivation
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// paths (which will get appended to the default root path) must not have prefixes
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// in front of the first element. Whitespace is ignored.
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func ParseDerivationPath(path string) (DerivationPath, error) {
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var result DerivationPath
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// Handle absolute or relative paths
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components := strings.Split(path, "/")
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switch {
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case len(components) == 0:
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return nil, errors.New("empty derivation path")
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case strings.TrimSpace(components[0]) == "":
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return nil, errors.New("ambiguous path: use 'm/' prefix for absolute paths, or no leading '/' for relative ones")
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case strings.TrimSpace(components[0]) == "m":
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components = components[1:]
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default:
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result = append(result, DefaultRootDerivationPath...)
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}
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// All remaining components are relative, append one by one
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if len(components) == 0 {
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return nil, errors.New("empty derivation path") // Empty relative paths
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}
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for _, component := range components {
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// Ignore any user added whitespace
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component = strings.TrimSpace(component)
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var value uint32
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// Handle hardened paths
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if strings.HasSuffix(component, "'") {
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value = 0x80000000
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component = strings.TrimSpace(strings.TrimSuffix(component, "'"))
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}
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// Handle the non hardened component
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bigval, ok := new(big.Int).SetString(component, 0)
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if !ok {
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return nil, fmt.Errorf("invalid component: %s", component)
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}
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max := math.MaxUint32 - value
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if bigval.Sign() < 0 || bigval.Cmp(big.NewInt(int64(max))) > 0 {
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if value == 0 {
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return nil, fmt.Errorf("component %v out of allowed range [0, %d]", bigval, max)
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}
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return nil, fmt.Errorf("component %v out of allowed hardened range [0, %d]", bigval, max)
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}
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value += uint32(bigval.Uint64())
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// Append and repeat
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result = append(result, value)
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}
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return result, nil
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}
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// String implements the stringer interface, converting a binary derivation path
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// to its canonical representation.
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func (path DerivationPath) String() string {
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result := "m"
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for _, component := range path {
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var hardened bool
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if component >= 0x80000000 {
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component -= 0x80000000
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hardened = true
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}
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result = fmt.Sprintf("%s/%d", result, component)
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if hardened {
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result += "'"
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}
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}
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return result
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}
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