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tailscale/ipn/ipnlocal/network-lock.go

718 lines
21 KiB
Go

// Copyright (c) 2022 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package ipnlocal
import (
"bytes"
"context"
"encoding/json"
"errors"
"fmt"
"io"
"net/http"
"os"
"path/filepath"
"time"
"tailscale.com/envknob"
"tailscale.com/ipn/ipnstate"
"tailscale.com/tailcfg"
"tailscale.com/tka"
"tailscale.com/types/key"
"tailscale.com/types/netmap"
"tailscale.com/types/tkatype"
)
// TODO(tom): RPC retry/backoff was broken and has been removed. Fix?
var (
errMissingNetmap = errors.New("missing netmap: verify that you are logged in")
errNetworkLockNotActive = errors.New("network-lock is not active")
)
type tkaState struct {
authority *tka.Authority
storage *tka.FS
}
// tkaFilterNetmapLocked checks the signatures on each node key, dropping
// nodes from the netmap who's signature does not verify.
//
// b.mu must be held.
func (b *LocalBackend) tkaFilterNetmapLocked(nm *netmap.NetworkMap) {
if !envknob.UseWIPCode() {
return // Feature-flag till network-lock is in Alpha.
}
if b.tka == nil {
return // TKA not enabled.
}
toDelete := make(map[int]struct{}, len(nm.Peers))
for i, p := range nm.Peers {
if len(p.KeySignature) == 0 {
b.logf("Network lock is dropping peer %v(%v) due to missing signature", p.ID, p.StableID)
toDelete[i] = struct{}{}
} else {
if err := b.tka.authority.NodeKeyAuthorized(p.Key, p.KeySignature); err != nil {
b.logf("Network lock is dropping peer %v(%v) due to failed signature check: %v", p.ID, p.StableID, err)
toDelete[i] = struct{}{}
}
}
}
// nm.Peers is ordered, so deletion must be order-preserving.
peers := make([]*tailcfg.Node, 0, len(nm.Peers))
for i, p := range nm.Peers {
if _, delete := toDelete[i]; !delete {
peers = append(peers, p)
}
}
nm.Peers = peers
}
// tkaSyncIfNeeded examines TKA info reported from the control plane,
// performing the steps necessary to synchronize local tka state.
//
// There are 4 scenarios handled here:
// - Enablement: nm.TKAEnabled but b.tka == nil
// ∴ reach out to /machine/tka/bootstrap to get the genesis AUM, then
// initialize TKA.
// - Disablement: !nm.TKAEnabled but b.tka != nil
// ∴ reach out to /machine/tka/bootstrap to read the disablement secret,
// then verify and clear tka local state.
// - Sync needed: b.tka.Head != nm.TKAHead
// ∴ complete multi-step synchronization flow.
// - Everything up to date: All other cases.
// ∴ no action necessary.
//
// tkaSyncIfNeeded immediately takes b.takeSyncLock which is held throughout,
// and may take b.mu as required.
func (b *LocalBackend) tkaSyncIfNeeded(nm *netmap.NetworkMap) error {
if !envknob.UseWIPCode() {
// If the feature flag is not enabled, pretend we don't exist.
return nil
}
b.tkaSyncLock.Lock() // take tkaSyncLock to make this function an exclusive section.
defer b.tkaSyncLock.Unlock()
b.mu.Lock() // take mu to protect access to synchronized fields.
defer b.mu.Unlock()
ourNodeKey := b.prefs.Persist.PrivateNodeKey.Public()
isEnabled := b.tka != nil
wantEnabled := nm.TKAEnabled
if isEnabled != wantEnabled {
var ourHead tka.AUMHash
if b.tka != nil {
ourHead = b.tka.authority.Head()
}
// Regardless of whether we are moving to disabled or enabled, we
// need information from the tka bootstrap endpoint.
b.mu.Unlock()
bs, err := b.tkaFetchBootstrap(ourNodeKey, ourHead)
b.mu.Lock()
if err != nil {
return fmt.Errorf("fetching bootstrap: %w", err)
}
if wantEnabled && !isEnabled {
if err := b.tkaBootstrapFromGenesisLocked(bs.GenesisAUM); err != nil {
return fmt.Errorf("bootstrap: %w", err)
}
isEnabled = true
} else if !wantEnabled && isEnabled {
if b.tka.authority.ValidDisablement(bs.DisablementSecret) {
b.tka = nil
isEnabled = false
if err := os.RemoveAll(b.chonkPath()); err != nil {
return fmt.Errorf("os.RemoveAll: %v", err)
}
} else {
b.logf("Disablement secret did not verify, leaving TKA enabled.")
}
} else {
return fmt.Errorf("[bug] unreachable invariant of wantEnabled /w isEnabled")
}
}
if isEnabled && b.tka.authority.Head() != nm.TKAHead {
if err := b.tkaSyncLocked(ourNodeKey); err != nil {
return fmt.Errorf("tka sync: %w", err)
}
}
return nil
}
func toSyncOffer(head string, ancestors []string) (tka.SyncOffer, error) {
var out tka.SyncOffer
if err := out.Head.UnmarshalText([]byte(head)); err != nil {
return tka.SyncOffer{}, fmt.Errorf("head.UnmarshalText: %v", err)
}
out.Ancestors = make([]tka.AUMHash, len(ancestors))
for i, a := range ancestors {
if err := out.Ancestors[i].UnmarshalText([]byte(a)); err != nil {
return tka.SyncOffer{}, fmt.Errorf("ancestor[%d].UnmarshalText: %v", i, err)
}
}
return out, nil
}
// tkaSyncLocked synchronizes TKA state with control. b.mu must be held
// and tka must be initialized. b.mu will be stepped out of (and back into)
// during network RPCs.
//
// b.mu must be held.
func (b *LocalBackend) tkaSyncLocked(ourNodeKey key.NodePublic) error {
offer, err := b.tka.authority.SyncOffer(b.tka.storage)
if err != nil {
return fmt.Errorf("offer: %w", err)
}
b.mu.Unlock()
offerResp, err := b.tkaDoSyncOffer(ourNodeKey, offer)
b.mu.Lock()
if err != nil {
return fmt.Errorf("offer RPC: %w", err)
}
controlOffer, err := toSyncOffer(offerResp.Head, offerResp.Ancestors)
if err != nil {
return fmt.Errorf("control offer: %v", err)
}
if controlOffer.Head == offer.Head {
// We are up to date.
return nil
}
// Compute missing AUMs before we apply any AUMs from the control-plane,
// so we still submit AUMs to control even if they are not part of the
// active chain.
toSendAUMs, err := b.tka.authority.MissingAUMs(b.tka.storage, controlOffer)
if err != nil {
return fmt.Errorf("computing missing AUMs: %w", err)
}
// If we got this far, then we are not up to date. Either the control-plane
// has updates for us, or we have updates for the control plane.
//
// TODO(tom): Do we want to keep processing even if the Inform fails? Need
// to think through if theres holdback concerns here or not.
if len(offerResp.MissingAUMs) > 0 {
aums := make([]tka.AUM, len(offerResp.MissingAUMs))
for i, a := range offerResp.MissingAUMs {
if err := aums[i].Unserialize(a); err != nil {
return fmt.Errorf("MissingAUMs[%d]: %v", i, err)
}
}
if err := b.tka.authority.Inform(b.tka.storage, aums); err != nil {
return fmt.Errorf("inform failed: %v", err)
}
}
// NOTE(tom): We could short-circuit here if our HEAD equals the
// control-plane's head, but we don't just so control always has a
// copy of all forks that clients had.
b.mu.Unlock()
sendResp, err := b.tkaDoSyncSend(ourNodeKey, toSendAUMs, false)
b.mu.Lock()
if err != nil {
return fmt.Errorf("send RPC: %v", err)
}
var remoteHead tka.AUMHash
if err := remoteHead.UnmarshalText([]byte(sendResp.Head)); err != nil {
return fmt.Errorf("head unmarshal: %v", err)
}
if remoteHead != b.tka.authority.Head() {
b.logf("TKA desync: expected consensus after sync but our head is %v and the control plane's is %v", b.tka.authority.Head(), remoteHead)
}
return nil
}
// chonkPath returns the absolute path to the directory in which TKA
// state (the 'tailchonk') is stored.
func (b *LocalBackend) chonkPath() string {
return filepath.Join(b.TailscaleVarRoot(), "tka")
}
// tkaBootstrapFromGenesisLocked initializes the local (on-disk) state of the
// tailnet key authority, based on the given genesis AUM.
//
// b.mu must be held.
func (b *LocalBackend) tkaBootstrapFromGenesisLocked(g tkatype.MarshaledAUM) error {
if err := b.CanSupportNetworkLock(); err != nil {
return err
}
var genesis tka.AUM
if err := genesis.Unserialize(g); err != nil {
return fmt.Errorf("reading genesis: %v", err)
}
chonkDir := b.chonkPath()
if err := os.Mkdir(chonkDir, 0755); err != nil && !os.IsExist(err) {
return fmt.Errorf("mkdir: %v", err)
}
chonk, err := tka.ChonkDir(chonkDir)
if err != nil {
return fmt.Errorf("chonk: %v", err)
}
authority, err := tka.Bootstrap(chonk, genesis)
if err != nil {
return fmt.Errorf("tka bootstrap: %v", err)
}
b.tka = &tkaState{
authority: authority,
storage: chonk,
}
return nil
}
// CanSupportNetworkLock returns nil if tailscaled is able to operate
// a local tailnet key authority (and hence enforce network lock).
func (b *LocalBackend) CanSupportNetworkLock() error {
if !envknob.UseWIPCode() {
return errors.New("this feature is not yet complete, a later release may support this functionality")
}
if b.tka != nil {
// If the TKA is being used, it is supported.
return nil
}
if b.TailscaleVarRoot() == "" {
return errors.New("network-lock is not supported in this configuration, try setting --statedir")
}
// There's a var root (aka --statedir), so if network lock gets
// initialized we have somewhere to store our AUMs. That's all
// we need.
return nil
}
// NetworkLockStatus returns a structure describing the state of the
// tailnet key authority, if any.
func (b *LocalBackend) NetworkLockStatus() *ipnstate.NetworkLockStatus {
b.mu.Lock()
defer b.mu.Unlock()
if b.tka == nil {
return &ipnstate.NetworkLockStatus{
Enabled: false,
PublicKey: b.nlPrivKey.Public(),
}
}
var head [32]byte
h := b.tka.authority.Head()
copy(head[:], h[:])
return &ipnstate.NetworkLockStatus{
Enabled: true,
Head: &head,
PublicKey: b.nlPrivKey.Public(),
}
}
// NetworkLockInit enables network-lock for the tailnet, with the tailnets'
// key authority initialized to trust the provided keys.
//
// Initialization involves two RPCs with control, termed 'begin' and 'finish'.
// The Begin RPC transmits the genesis Authority Update Message, which
// encodes the initial state of the authority, and the list of all nodes
// needing signatures is returned as a response.
// The Finish RPC submits signatures for all these nodes, at which point
// Control has everything it needs to atomically enable network lock.
func (b *LocalBackend) NetworkLockInit(keys []tka.Key) error {
if err := b.CanSupportNetworkLock(); err != nil {
return err
}
var ourNodeKey key.NodePublic
b.mu.Lock()
if b.prefs != nil {
ourNodeKey = b.prefs.Persist.PrivateNodeKey.Public()
}
b.mu.Unlock()
if ourNodeKey.IsZero() {
return errors.New("no node-key: is tailscale logged in?")
}
// Generates a genesis AUM representing trust in the provided keys.
// We use an in-memory tailchonk because we don't want to commit to
// the filesystem until we've finished the initialization sequence,
// just in case something goes wrong.
_, genesisAUM, err := tka.Create(&tka.Mem{}, tka.State{
Keys: keys,
// TODO(tom): Actually plumb a real disablement value.
DisablementSecrets: [][]byte{bytes.Repeat([]byte{1}, 32)},
}, b.nlPrivKey)
if err != nil {
return fmt.Errorf("tka.Create: %v", err)
}
b.logf("Generated genesis AUM to initialize network lock, trusting the following keys:")
for i, k := range genesisAUM.State.Keys {
b.logf(" - key[%d] = nlpub:%x with %d votes", i, k.Public, k.Votes)
}
// Phase 1/2 of initialization: Transmit the genesis AUM to Control.
initResp, err := b.tkaInitBegin(ourNodeKey, genesisAUM)
if err != nil {
return fmt.Errorf("tka init-begin RPC: %w", err)
}
// Our genesis AUM was accepted but before Control turns on enforcement of
// node-key signatures, we need to sign keys for all the existing nodes.
// If we don't get these signatures ahead of time, everyone will loose
// connectivity because control won't have any signatures to send which
// satisfy network-lock checks.
sigs := make(map[tailcfg.NodeID]tkatype.MarshaledSignature, len(initResp.NeedSignatures))
for _, nodeInfo := range initResp.NeedSignatures {
nks, err := signNodeKey(nodeInfo, b.nlPrivKey)
if err != nil {
return fmt.Errorf("generating signature: %v", err)
}
sigs[nodeInfo.NodeID] = nks.Serialize()
}
// Finalize enablement by transmitting signature for all nodes to Control.
_, err = b.tkaInitFinish(ourNodeKey, sigs)
return err
}
// Only use is in tests.
func (b *LocalBackend) NetworkLockVerifySignatureForTest(nks tkatype.MarshaledSignature, nodeKey key.NodePublic) error {
b.mu.Lock()
defer b.mu.Unlock()
if b.tka == nil {
return errNetworkLockNotActive
}
return b.tka.authority.NodeKeyAuthorized(nodeKey, nks)
}
// Only use is in tests.
func (b *LocalBackend) NetworkLockKeyTrustedForTest(keyID tkatype.KeyID) bool {
b.mu.Lock()
defer b.mu.Unlock()
if b.tka == nil {
panic("network lock not initialized")
}
return b.tka.authority.KeyTrusted(keyID)
}
// NetworkLockModify adds and/or removes keys in the tailnet's key authority.
func (b *LocalBackend) NetworkLockModify(addKeys, removeKeys []tka.Key) (err error) {
defer func() {
if err != nil {
err = fmt.Errorf("modify network-lock keys: %w", err)
}
}()
b.mu.Lock()
defer b.mu.Unlock()
if err := b.CanSupportNetworkLock(); err != nil {
return err
}
if b.tka == nil {
return errNetworkLockNotActive
}
updater := b.tka.authority.NewUpdater(b.nlPrivKey)
for _, addKey := range addKeys {
if err := updater.AddKey(addKey); err != nil {
return err
}
}
for _, removeKey := range removeKeys {
if err := updater.RemoveKey(removeKey.ID()); err != nil {
return err
}
}
aums, err := updater.Finalize(b.tka.storage)
if err != nil {
return err
}
if len(aums) == 0 {
return nil
}
ourNodeKey := b.prefs.Persist.PrivateNodeKey.Public()
b.mu.Unlock()
resp, err := b.tkaDoSyncSend(ourNodeKey, aums, true)
b.mu.Lock()
if err != nil {
return err
}
var controlHead tka.AUMHash
if err := controlHead.UnmarshalText([]byte(resp.Head)); err != nil {
return err
}
lastHead := aums[len(aums)-1].Hash()
if controlHead != lastHead {
return errors.New("central tka head differs from submitted AUM, try again")
}
return nil
}
func signNodeKey(nodeInfo tailcfg.TKASignInfo, signer key.NLPrivate) (*tka.NodeKeySignature, error) {
p, err := nodeInfo.NodePublic.MarshalBinary()
if err != nil {
return nil, err
}
sig := tka.NodeKeySignature{
SigKind: tka.SigDirect,
KeyID: signer.KeyID(),
Pubkey: p,
WrappingPubkey: nodeInfo.RotationPubkey,
}
sig.Signature, err = signer.SignNKS(sig.SigHash())
if err != nil {
return nil, fmt.Errorf("signature failed: %w", err)
}
return &sig, nil
}
func (b *LocalBackend) tkaInitBegin(ourNodeKey key.NodePublic, aum tka.AUM) (*tailcfg.TKAInitBeginResponse, error) {
var req bytes.Buffer
if err := json.NewEncoder(&req).Encode(tailcfg.TKAInitBeginRequest{
Version: tailcfg.CurrentCapabilityVersion,
NodeKey: ourNodeKey,
GenesisAUM: aum.Serialize(),
}); err != nil {
return nil, fmt.Errorf("encoding request: %v", err)
}
ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
defer cancel()
req2, err := http.NewRequestWithContext(ctx, "GET", "https://unused/machine/tka/init/begin", &req)
if err != nil {
return nil, fmt.Errorf("req: %w", err)
}
res, err := b.DoNoiseRequest(req2)
if err != nil {
return nil, fmt.Errorf("resp: %w", err)
}
if res.StatusCode != 200 {
body, _ := io.ReadAll(res.Body)
res.Body.Close()
return nil, fmt.Errorf("request returned (%d): %s", res.StatusCode, string(body))
}
a := new(tailcfg.TKAInitBeginResponse)
err = json.NewDecoder(res.Body).Decode(a)
res.Body.Close()
if err != nil {
return nil, fmt.Errorf("decoding JSON: %w", err)
}
return a, nil
}
func (b *LocalBackend) tkaInitFinish(ourNodeKey key.NodePublic, nks map[tailcfg.NodeID]tkatype.MarshaledSignature) (*tailcfg.TKAInitFinishResponse, error) {
var req bytes.Buffer
if err := json.NewEncoder(&req).Encode(tailcfg.TKAInitFinishRequest{
Version: tailcfg.CurrentCapabilityVersion,
NodeKey: ourNodeKey,
Signatures: nks,
}); err != nil {
return nil, fmt.Errorf("encoding request: %v", err)
}
ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
defer cancel()
req2, err := http.NewRequestWithContext(ctx, "GET", "https://unused/machine/tka/init/finish", &req)
if err != nil {
return nil, fmt.Errorf("req: %w", err)
}
res, err := b.DoNoiseRequest(req2)
if err != nil {
return nil, fmt.Errorf("resp: %w", err)
}
if res.StatusCode != 200 {
body, _ := io.ReadAll(res.Body)
res.Body.Close()
return nil, fmt.Errorf("request returned (%d): %s", res.StatusCode, string(body))
}
a := new(tailcfg.TKAInitFinishResponse)
err = json.NewDecoder(res.Body).Decode(a)
res.Body.Close()
if err != nil {
return nil, fmt.Errorf("decoding JSON: %w", err)
}
return a, nil
}
// tkaFetchBootstrap sends a /machine/tka/bootstrap RPC to the control plane
// over noise. This is used to get values necessary to enable or disable TKA.
func (b *LocalBackend) tkaFetchBootstrap(ourNodeKey key.NodePublic, head tka.AUMHash) (*tailcfg.TKABootstrapResponse, error) {
bootstrapReq := tailcfg.TKABootstrapRequest{
Version: tailcfg.CurrentCapabilityVersion,
NodeKey: ourNodeKey,
}
if !head.IsZero() {
head, err := head.MarshalText()
if err != nil {
return nil, fmt.Errorf("head.MarshalText failed: %v", err)
}
bootstrapReq.Head = string(head)
}
var req bytes.Buffer
if err := json.NewEncoder(&req).Encode(bootstrapReq); err != nil {
return nil, fmt.Errorf("encoding request: %v", err)
}
ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
defer cancel()
if err := ctx.Err(); err != nil {
return nil, fmt.Errorf("ctx: %w", err)
}
req2, err := http.NewRequestWithContext(ctx, "GET", "https://unused/machine/tka/bootstrap", &req)
if err != nil {
return nil, fmt.Errorf("req: %w", err)
}
res, err := b.DoNoiseRequest(req2)
if err != nil {
return nil, fmt.Errorf("resp: %w", err)
}
if res.StatusCode != 200 {
body, _ := io.ReadAll(res.Body)
res.Body.Close()
return nil, fmt.Errorf("request returned (%d): %s", res.StatusCode, string(body))
}
a := new(tailcfg.TKABootstrapResponse)
err = json.NewDecoder(res.Body).Decode(a)
res.Body.Close()
if err != nil {
return nil, fmt.Errorf("decoding JSON: %w", err)
}
return a, nil
}
func fromSyncOffer(offer tka.SyncOffer) (head string, ancestors []string, err error) {
headBytes, err := offer.Head.MarshalText()
if err != nil {
return "", nil, fmt.Errorf("head.MarshalText: %v", err)
}
ancestors = make([]string, len(offer.Ancestors))
for i, ancestor := range offer.Ancestors {
hash, err := ancestor.MarshalText()
if err != nil {
return "", nil, fmt.Errorf("ancestor[%d].MarshalText: %v", i, err)
}
ancestors[i] = string(hash)
}
return string(headBytes), ancestors, nil
}
// tkaDoSyncOffer sends a /machine/tka/sync/offer RPC to the control plane
// over noise. This is the first of two RPCs implementing tka synchronization.
func (b *LocalBackend) tkaDoSyncOffer(ourNodeKey key.NodePublic, offer tka.SyncOffer) (*tailcfg.TKASyncOfferResponse, error) {
head, ancestors, err := fromSyncOffer(offer)
if err != nil {
return nil, fmt.Errorf("encoding offer: %v", err)
}
syncReq := tailcfg.TKASyncOfferRequest{
Version: tailcfg.CurrentCapabilityVersion,
NodeKey: ourNodeKey,
Head: head,
Ancestors: ancestors,
}
var req bytes.Buffer
if err := json.NewEncoder(&req).Encode(syncReq); err != nil {
return nil, fmt.Errorf("encoding request: %v", err)
}
ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
defer cancel()
req2, err := http.NewRequestWithContext(ctx, "GET", "https://unused/machine/tka/sync/offer", &req)
if err != nil {
return nil, fmt.Errorf("req: %w", err)
}
res, err := b.DoNoiseRequest(req2)
if err != nil {
return nil, fmt.Errorf("resp: %w", err)
}
if res.StatusCode != 200 {
body, _ := io.ReadAll(res.Body)
res.Body.Close()
return nil, fmt.Errorf("request returned (%d): %s", res.StatusCode, string(body))
}
a := new(tailcfg.TKASyncOfferResponse)
err = json.NewDecoder(res.Body).Decode(a)
res.Body.Close()
if err != nil {
return nil, fmt.Errorf("decoding JSON: %w", err)
}
return a, nil
}
// tkaDoSyncSend sends a /machine/tka/sync/send RPC to the control plane
// over noise. This is the second of two RPCs implementing tka synchronization.
func (b *LocalBackend) tkaDoSyncSend(ourNodeKey key.NodePublic, aums []tka.AUM, interactive bool) (*tailcfg.TKASyncSendResponse, error) {
sendReq := tailcfg.TKASyncSendRequest{
Version: tailcfg.CurrentCapabilityVersion,
NodeKey: ourNodeKey,
MissingAUMs: make([]tkatype.MarshaledAUM, len(aums)),
Interactive: interactive,
}
for i, a := range aums {
sendReq.MissingAUMs[i] = a.Serialize()
}
var req bytes.Buffer
if err := json.NewEncoder(&req).Encode(sendReq); err != nil {
return nil, fmt.Errorf("encoding request: %v", err)
}
ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
defer cancel()
req2, err := http.NewRequestWithContext(ctx, "GET", "https://unused/machine/tka/sync/send", &req)
if err != nil {
return nil, fmt.Errorf("req: %w", err)
}
res, err := b.DoNoiseRequest(req2)
if err != nil {
return nil, fmt.Errorf("resp: %w", err)
}
if res.StatusCode != 200 {
body, _ := io.ReadAll(res.Body)
res.Body.Close()
return nil, fmt.Errorf("request returned (%d): %s", res.StatusCode, string(body))
}
a := new(tailcfg.TKASyncSendResponse)
err = json.NewDecoder(res.Body).Decode(a)
res.Body.Close()
if err != nil {
return nil, fmt.Errorf("decoding JSON: %w", err)
}
return a, nil
}