mirror of
https://github.com/tailscale/tailscale.git
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f0347e841f
The io/ioutil package has been deprecated as of Go 1.16 [1]. This commit replaces the existing io/ioutil functions with their new definitions in io and os packages. Reference: https://golang.org/doc/go1.16#ioutil Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>
438 lines
11 KiB
Go
438 lines
11 KiB
Go
// Copyright (c) 2022 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package tka
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import (
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"bytes"
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"fmt"
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"os"
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"path/filepath"
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"sync"
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"github.com/fxamacker/cbor/v2"
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"tailscale.com/atomicfile"
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)
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// Chonk implementations provide durable storage for AUMs and other
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// TKA state.
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//
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// All methods must be thread-safe.
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//
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// The name 'tailchonk' was coined by @catzkorn.
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type Chonk interface {
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// AUM returns the AUM with the specified digest.
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//
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// If the AUM does not exist, then os.ErrNotExist is returned.
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AUM(hash AUMHash) (AUM, error)
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// ChildAUMs returns all AUMs with a specified previous
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// AUM hash.
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ChildAUMs(prevAUMHash AUMHash) ([]AUM, error)
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// CommitVerifiedAUMs durably stores the provided AUMs.
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// Callers MUST ONLY provide AUMs which are verified (specifically,
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// a call to aumVerify() must return a nil error).
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// as the implementation assumes that only verified AUMs are stored.
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CommitVerifiedAUMs(updates []AUM) error
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// Heads returns AUMs for which there are no children. In other
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// words, the latest AUM in all possible chains (the 'leaves').
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Heads() ([]AUM, error)
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// SetLastActiveAncestor is called to record the oldest-known AUM
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// that contributed to the current state. This value is used as
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// a hint on next startup to determine which chain to pick when computing
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// the current state, if there are multiple distinct chains.
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SetLastActiveAncestor(hash AUMHash) error
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// LastActiveAncestor returns the oldest-known AUM that was (in a
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// previous run) an ancestor of the current state. This is used
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// as a hint to pick the correct chain in the event that the Chonk stores
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// multiple distinct chains.
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LastActiveAncestor() (*AUMHash, error)
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}
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// Mem implements in-memory storage of TKA state, suitable for
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// tests.
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//
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// Mem implements the Chonk interface.
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type Mem struct {
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l sync.RWMutex
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aums map[AUMHash]AUM
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parentIndex map[AUMHash][]AUMHash
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lastActiveAncestor *AUMHash
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}
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func (c *Mem) SetLastActiveAncestor(hash AUMHash) error {
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c.l.Lock()
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defer c.l.Unlock()
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c.lastActiveAncestor = &hash
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return nil
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}
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func (c *Mem) LastActiveAncestor() (*AUMHash, error) {
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c.l.RLock()
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defer c.l.RUnlock()
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return c.lastActiveAncestor, nil
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}
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// Heads returns AUMs for which there are no children. In other
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// words, the latest AUM in all chains (the 'leaf').
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func (c *Mem) Heads() ([]AUM, error) {
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c.l.RLock()
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defer c.l.RUnlock()
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out := make([]AUM, 0, 6)
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// An AUM is a 'head' if there are no nodes for which it is the parent.
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for _, a := range c.aums {
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if len(c.parentIndex[a.Hash()]) == 0 {
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out = append(out, a)
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}
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}
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return out, nil
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}
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// AUM returns the AUM with the specified digest.
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func (c *Mem) AUM(hash AUMHash) (AUM, error) {
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c.l.RLock()
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defer c.l.RUnlock()
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aum, ok := c.aums[hash]
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if !ok {
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return AUM{}, os.ErrNotExist
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}
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return aum, nil
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}
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// Orphans returns all AUMs which do not have a parent.
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func (c *Mem) Orphans() ([]AUM, error) {
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c.l.RLock()
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defer c.l.RUnlock()
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out := make([]AUM, 0, 6)
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for _, a := range c.aums {
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if _, ok := a.Parent(); !ok {
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out = append(out, a)
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}
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}
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return out, nil
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}
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// ChildAUMs returns all AUMs with a specified previous
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// AUM hash.
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func (c *Mem) ChildAUMs(prevAUMHash AUMHash) ([]AUM, error) {
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c.l.RLock()
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defer c.l.RUnlock()
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out := make([]AUM, 0, 6)
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for _, entry := range c.parentIndex[prevAUMHash] {
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out = append(out, c.aums[entry])
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}
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return out, nil
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}
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// CommitVerifiedAUMs durably stores the provided AUMs.
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// Callers MUST ONLY provide well-formed and verified AUMs,
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// as the rest of the TKA implementation assumes that only
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// verified AUMs are stored.
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func (c *Mem) CommitVerifiedAUMs(updates []AUM) error {
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c.l.Lock()
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defer c.l.Unlock()
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if c.aums == nil {
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c.parentIndex = make(map[AUMHash][]AUMHash, 64)
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c.aums = make(map[AUMHash]AUM, 64)
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}
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updateLoop:
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for _, aum := range updates {
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aumHash := aum.Hash()
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c.aums[aumHash] = aum
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parent, ok := aum.Parent()
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if ok {
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for _, exists := range c.parentIndex[parent] {
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if exists == aumHash {
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continue updateLoop
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}
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}
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c.parentIndex[parent] = append(c.parentIndex[parent], aumHash)
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}
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}
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return nil
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}
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// FS implements filesystem storage of TKA state.
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//
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// FS implements the Chonk interface.
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type FS struct {
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base string
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mu sync.RWMutex
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}
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// ChonkDir returns an implementation of Chonk which uses the
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// given directory to store TKA state.
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func ChonkDir(dir string) (*FS, error) {
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stat, err := os.Stat(dir)
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if err != nil {
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return nil, err
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}
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if !stat.IsDir() {
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return nil, fmt.Errorf("chonk directory %q is a file", dir)
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}
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return &FS{base: dir}, nil
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}
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// fsHashInfo describes how information about an AUMHash is represented
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// on disk.
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//
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// The CBOR-serialization of this struct is stored to base/__/base32(hash)
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// where __ are the first two characters of base32(hash).
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//
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// CBOR was chosen because we are already using it and it serializes
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// much smaller than JSON for AUMs. The 'keyasint' thing isn't essential
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// but again it saves a bunch of bytes.
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type fsHashInfo struct {
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Children []AUMHash `cbor:"1,keyasint"`
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AUM *AUM `cbor:"2,keyasint"`
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}
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// aumDir returns the directory an AUM is stored in, and its filename
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// within the directory.
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func (c *FS) aumDir(h AUMHash) (dir, base string) {
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s := h.String()
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return filepath.Join(c.base, s[:2]), s
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}
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// AUM returns the AUM with the specified digest.
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//
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// If the AUM does not exist, then os.ErrNotExist is returned.
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func (c *FS) AUM(hash AUMHash) (AUM, error) {
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c.mu.RLock()
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defer c.mu.RUnlock()
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info, err := c.get(hash)
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if err != nil {
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return AUM{}, err
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}
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if info.AUM == nil {
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return AUM{}, os.ErrNotExist
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}
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return *info.AUM, nil
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}
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// AUM returns any known AUMs with a specific parent hash.
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func (c *FS) ChildAUMs(prevAUMHash AUMHash) ([]AUM, error) {
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c.mu.RLock()
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defer c.mu.RUnlock()
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info, err := c.get(prevAUMHash)
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if err != nil {
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if os.IsNotExist(err) {
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// not knowing about this hash is not an error
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return nil, nil
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}
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return nil, err
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}
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out := make([]AUM, len(info.Children))
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for i, h := range info.Children {
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c, err := c.get(h)
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if err != nil {
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// We expect any AUM recorded as a child on its parent to exist.
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return nil, fmt.Errorf("reading child %d of %x: %v", i, h, err)
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}
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if c.AUM == nil {
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return nil, fmt.Errorf("child %d of %x: AUM not stored", i, h)
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}
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out[i] = *c.AUM
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}
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return out, nil
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}
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func (c *FS) get(h AUMHash) (*fsHashInfo, error) {
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dir, base := c.aumDir(h)
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f, err := os.Open(filepath.Join(dir, base))
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if err != nil {
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return nil, err
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}
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defer f.Close()
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m, err := cborDecOpts.DecMode()
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if err != nil {
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return nil, err
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}
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var out fsHashInfo
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if err := m.NewDecoder(f).Decode(&out); err != nil {
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return nil, err
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}
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if out.AUM != nil && out.AUM.Hash() != h {
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return nil, fmt.Errorf("%s: AUM does not match file name hash %s", f.Name(), out.AUM.Hash())
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}
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return &out, nil
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}
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// Heads returns AUMs for which there are no children. In other
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// words, the latest AUM in all possible chains (the 'leaves').
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//
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// Heads is expected to be called infrequently compared to AUM() or
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// ChildAUMs(), so we haven't put any work into maintaining an index.
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// Instead, the full set of AUMs is scanned.
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func (c *FS) Heads() ([]AUM, error) {
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c.mu.RLock()
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defer c.mu.RUnlock()
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out := make([]AUM, 0, 6) // 6 is arbitrary.
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err := c.scanHashes(func(info *fsHashInfo) {
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if len(info.Children) == 0 && info.AUM != nil {
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out = append(out, *info.AUM)
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}
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})
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return out, err
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}
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func (c *FS) scanHashes(eachHashInfo func(*fsHashInfo)) error {
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prefixDirs, err := os.ReadDir(c.base)
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if err != nil {
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return fmt.Errorf("reading prefix dirs: %v", err)
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}
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for _, prefix := range prefixDirs {
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if !prefix.IsDir() {
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continue
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}
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files, err := os.ReadDir(filepath.Join(c.base, prefix.Name()))
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if err != nil {
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return fmt.Errorf("reading prefix dir: %v", err)
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}
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for _, file := range files {
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var h AUMHash
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if err := h.UnmarshalText([]byte(file.Name())); err != nil {
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return fmt.Errorf("invalid aum file: %s: %w", file.Name(), err)
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}
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info, err := c.get(h)
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if err != nil {
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return fmt.Errorf("reading %x: %v", h, err)
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}
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eachHashInfo(info)
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}
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}
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return nil
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}
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// SetLastActiveAncestor is called to record the oldest-known AUM
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// that contributed to the current state. This value is used as
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// a hint on next startup to determine which chain to pick when computing
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// the current state, if there are multiple distinct chains.
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func (c *FS) SetLastActiveAncestor(hash AUMHash) error {
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c.mu.Lock()
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defer c.mu.Unlock()
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return atomicfile.WriteFile(filepath.Join(c.base, "last_active_ancestor"), hash[:], 0644)
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}
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// LastActiveAncestor returns the oldest-known AUM that was (in a
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// previous run) an ancestor of the current state. This is used
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// as a hint to pick the correct chain in the event that the Chonk stores
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// multiple distinct chains.
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//
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// Nil is returned if no last-active ancestor is set.
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func (c *FS) LastActiveAncestor() (*AUMHash, error) {
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c.mu.RLock()
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defer c.mu.RUnlock()
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hash, err := os.ReadFile(filepath.Join(c.base, "last_active_ancestor"))
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if err != nil {
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if os.IsNotExist(err) {
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return nil, nil // Not exist == none set.
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}
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return nil, err
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}
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var out AUMHash
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if len(hash) != len(out) {
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return nil, fmt.Errorf("stored hash is of wrong length: %d != %d", len(hash), len(out))
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}
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copy(out[:], hash)
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return &out, nil
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}
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// CommitVerifiedAUMs durably stores the provided AUMs.
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// Callers MUST ONLY provide AUMs which are verified (specifically,
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// a call to aumVerify must return a nil error), as the
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// implementation assumes that only verified AUMs are stored.
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func (c *FS) CommitVerifiedAUMs(updates []AUM) error {
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c.mu.Lock()
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defer c.mu.Unlock()
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for i, aum := range updates {
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h := aum.Hash()
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// We keep track of children against their parent so that
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// ChildAUMs() do not need to scan all AUMs.
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parent, hasParent := aum.Parent()
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if hasParent {
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err := c.commit(parent, func(info *fsHashInfo) {
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// Only add it if its not already there.
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for i := range info.Children {
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if info.Children[i] == h {
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return
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}
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}
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info.Children = append(info.Children, h)
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})
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if err != nil {
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return fmt.Errorf("committing update[%d] to parent %x: %v", i, parent, err)
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}
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}
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err := c.commit(h, func(info *fsHashInfo) {
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info.AUM = &aum
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})
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if err != nil {
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return fmt.Errorf("committing update[%d] (%x): %v", i, h, err)
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}
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}
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return nil
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}
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// commit calls the provided updater function to record changes relevant
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// to the given hash. The caller is expected to update the AUM and
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// Children fields, as relevant.
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func (c *FS) commit(h AUMHash, updater func(*fsHashInfo)) error {
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toCommit := fsHashInfo{}
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existing, err := c.get(h)
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switch {
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case os.IsNotExist(err):
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case err != nil:
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return err
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default:
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toCommit = *existing
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}
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updater(&toCommit)
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if toCommit.AUM != nil && toCommit.AUM.Hash() != h {
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return fmt.Errorf("cannot commit AUM with hash %x to %x", toCommit.AUM.Hash(), h)
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}
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dir, base := c.aumDir(h)
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if err := os.MkdirAll(dir, 0755); err != nil && !os.IsExist(err) {
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return fmt.Errorf("creating directory: %v", err)
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}
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m, err := cbor.CTAP2EncOptions().EncMode()
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if err != nil {
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return fmt.Errorf("cbor EncMode: %v", err)
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}
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var buff bytes.Buffer
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if err := m.NewEncoder(&buff).Encode(toCommit); err != nil {
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return fmt.Errorf("encoding: %v", err)
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}
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return atomicfile.WriteFile(filepath.Join(dir, base), buff.Bytes(), 0644)
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}
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