path: root/accounts/keystore/account_cache.go

// 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 keystore

import (
    "bufio"
    "encoding/json"
    "fmt"
    "os"
    "path/filepath"
    "sort"
    "strings"
    "sync"
    "time"

    mapset "github.com/deckarep/golang-set"
    "github.com/dexon-foundation/dexon/accounts"
    "github.com/dexon-foundation/dexon/common"
    "github.com/dexon-foundation/dexon/log"
)

// Minimum amount of time between cache reloads. This limit applies if the platform does
// not support change notifications. It also applies if the keystore directory does not
// exist yet, the code will attempt to create a watcher at most this often.
const minReloadInterval = 2 * time.Second

type accountsByURL []accounts.Account

func (s accountsByURL) Len() int           { return len(s) }
func (s accountsByURL) Less(i, j int) bool { return s[i].URL.Cmp(s[j].URL) < 0 }
func (s accountsByURL) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }

// AmbiguousAddrError is returned when attempting to unlock
// an address for which more than one file exists.
type AmbiguousAddrError struct {
    Addr    common.Address
    Matches []accounts.Account
}

func (err *AmbiguousAddrError) Error() string {
    files := ""
    for i, a := range err.Matches {
        files += a.URL.Path
        if i < len(err.Matches)-1 {
            files += ", "
        }
    }
    return fmt.Sprintf("multiple keys match address (%s)", files)
}

// accountCache is a live index of all accounts in the keystore.
type accountCache struct {
    keydir   string
    watcher  *watcher
    mu       sync.Mutex
    all      accountsByURL
    byAddr   map[common.Address][]accounts.Account
    throttle *time.Timer
    notify   chan struct{}
    fileC    fileCache
}

func newAccountCache(keydir string) (*accountCache, chan struct{}) {
    ac := &accountCache{
        keydir: keydir,
        byAddr: make(map[common.Address][]accounts.Account),
        notify: make(chan struct{}, 1),
        fileC:  fileCache{all: mapset.NewThreadUnsafeSet()},
    }
    ac.watcher = newWatcher(ac)
    return ac, ac.notify
}

func (ac *accountCache) accounts() []accounts.Account {
    ac.maybeReload()
    ac.mu.Lock()
    defer ac.mu.Unlock()
    cpy := make([]accounts.Account, len(ac.all))
    copy(cpy, ac.all)
    return cpy
}

func (ac *accountCache) hasAddress(addr common.Address) bool {
    ac.maybeReload()
    ac.mu.Lock()
    defer ac.mu.Unlock()
    return len(ac.byAddr[addr]) > 0
}

func (ac *accountCache) add(newAccount accounts.Account) {
    ac.mu.Lock()
    defer ac.mu.Unlock()

    i := sort.Search(len(ac.all), func(i int) bool { return ac.all[i].URL.Cmp(newAccount.URL) >= 0 })
    if i < len(ac.all) && ac.all[i] == newAccount {
        return
    }
    // newAccount is not in the cache.
    ac.all = append(ac.all, accounts.Account{})
    copy(ac.all[i+1:], ac.all[i:])
    ac.all[i] = newAccount
    ac.byAddr[newAccount.Address] = append(ac.byAddr[newAccount.Address], newAccount)
}

// note: removed needs to be unique here (i.e. both File and Address must be set).
func (ac *accountCache) delete(removed accounts.Account) {
    ac.mu.Lock()
    defer ac.mu.Unlock()

    ac.all = removeAccount(ac.all, removed)
    if ba := removeAccount(ac.byAddr[removed.Address], removed); len(ba) == 0 {
        delete(ac.byAddr, removed.Address)
    } else {
        ac.byAddr[removed.Address] = ba
    }
}

// deleteByFile removes an account referenced by the given path.
func (ac *accountCache) deleteByFile(path string) {
    ac.mu.Lock()
    defer ac.mu.Unlock()
    i := sort.Search(len(ac.all), func(i int) bool { return ac.all[i].URL.Path >= path })

    if i < len(ac.all) && ac.all[i].URL.Path == path {
        removed := ac.all[i]
        ac.all = append(ac.all[:i], ac.all[i+1:]...)
        if ba := removeAccount(ac.byAddr[removed.Address], removed); len(ba) == 0 {
            delete(ac.byAddr, removed.Address)
        } else {
            ac.byAddr[removed.Address] = ba
        }
    }
}

func removeAccount(slice []accounts.Account, elem accounts.Account) []accounts.Account {
    for i := range slice {
        if slice[i] == elem {
            return append(slice[:i], slice[i+1:]...)
        }
    }
    return slice
}

// find returns the cached account for address if there is a unique match.
// The exact matching rules are explained by the documentation of accounts.Account.
// Callers must hold ac.mu.
func (ac *accountCache) find(a accounts.Account) (accounts.Account, error) {
    // Limit search to address candidates if possible.
    matches := ac.all
    if (a.Address != common.Address{}) {
        matches = ac.byAddr[a.Address]
    }
    if a.URL.Path != "" {
        // If only the basename is specified, complete the path.
        if !strings.ContainsRune(a.URL.Path, filepath.Separator) {
            a.URL.Path = filepath.Join(ac.keydir, a.URL.Path)
        }
        for i := range matches {
            if matches[i].URL == a.URL {
                return matches[i], nil
            }
        }
        if (a.Address == common.Address{}) {
            return accounts.Account{}, ErrNoMatch
        }
    }
    switch len(matches) {
    case 1:
        return matches[0], nil
    case 0:
        return accounts.Account{}, ErrNoMatch
    default:
        err := &AmbiguousAddrError{Addr: a.Address, Matches: make([]accounts.Account, len(matches))}
        copy(err.Matches, matches)
        sort.Sort(accountsByURL(err.Matches))
        return accounts.Account{}, err
    }
}

func (ac *accountCache) maybeReload() {
    ac.mu.Lock()

    if ac.watcher.running {
        ac.mu.Unlock()
        return // A watcher is running and will keep the cache up-to-date.
    }
    if ac.throttle == nil {
        ac.throttle = time.NewTimer(0)
    } else {
        select {
        case <-ac.throttle.C:
        default:
            ac.mu.Unlock()
            return // The cache was reloaded recently.
        }
    }
    // No watcher running, start it.
    ac.watcher.start()
    ac.throttle.Reset(minReloadInterval)
    ac.mu.Unlock()
    ac.scanAccounts()
}

func (ac *accountCache) close() {
    ac.mu.Lock()
    ac.watcher.close()
    if ac.throttle != nil {
        ac.throttle.Stop()
    }
    if ac.notify != nil {
        close(ac.notify)
        ac.notify = nil
    }
    ac.mu.Unlock()
}

// scanAccounts checks if any changes have occurred on the filesystem, and
// updates the account cache accordingly
func (ac *accountCache) scanAccounts() error {
    // Scan the entire folder metadata for file changes
    creates, deletes, updates, err := ac.fileC.scan(ac.keydir)
    if err != nil {
        log.Debug("Failed to reload keystore contents", "err", err)
        return err
    }
    if creates.Cardinality() == 0 && deletes.Cardinality() == 0 && updates.Cardinality() == 0 {
        return nil
    }
    // Create a helper method to scan the contents of the key files
    var (
        buf = new(bufio.Reader)
        key struct {
            Address string `json:"address"`
        }
    )
    readAccount := func(path string) *accounts.Account {
        fd, err := os.Open(path)
        if err != nil {
            log.Trace("Failed to open keystore file", "path", path, "err", err)
            return nil
        }
        defer fd.Close()
        buf.Reset(fd)
        // Parse the address.
        key.Address = ""
        err = json.NewDecoder(buf).Decode(&key)
        addr := common.HexToAddress(key.Address)
        switch {
        case err != nil:
            log.Debug("Failed to decode keystore key", "path", path, "err", err)
        case (addr == common.Address{}):
            log.Debug("Failed to decode keystore key", "path", path, "err", "missing or zero address")
        default:
            return &accounts.Account{
                Address: addr,
                URL:     accounts.URL{Scheme: KeyStoreScheme, Path: path},
            }
        }
        return nil
    }
    // Process all the file diffs
    start := time.Now()

    for _, p := range creates.ToSlice() {
        if a := readAccount(p.(string)); a != nil {
            ac.add(*a)
        }
    }
    for _, p := range deletes.ToSlice() {
        ac.deleteByFile(p.(string))
    }
    for _, p := range updates.ToSlice() {
        path := p.(string)
        ac.deleteByFile(path)
        if a := readAccount(path); a != nil {
            ac.add(*a)
        }
    }
    end := time.Now()

    select {
    case ac.notify <- struct{}{}:
    default:
    }
    log.Trace("Handled keystore changes", "time", end.Sub(start))
    return nil
}