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consul.go
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consul.go
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package nomad
import (
"context"
"fmt"
"strings"
"sync"
"time"
"github.com/armon/go-metrics"
"github.com/hashicorp/consul/api"
"github.com/hashicorp/go-hclog"
"github.com/hashicorp/nomad/command/agent/consul"
"github.com/hashicorp/nomad/nomad/structs"
"github.com/pkg/errors"
"golang.org/x/sync/errgroup"
"golang.org/x/time/rate"
)
const (
// siTokenDescriptionFmt is the format for the .Description field of
// service identity tokens generated on behalf of Nomad.
siTokenDescriptionFmt = "_nomad_si [%s] [%s] [%s]"
// siTokenRequestRateLimit is the maximum number of requests per second Nomad
// will make against Consul for requesting SI tokens.
siTokenRequestRateLimit rate.Limit = 500
// siTokenMaxParallelRevokes is the maximum number of parallel SI token
// revocation requests Nomad will make against Consul.
siTokenMaxParallelRevokes = 64
// siTokenRevocationInterval is the interval at which SI tokens that failed
// initial revocation are retried.
siTokenRevocationInterval = 5 * time.Minute
)
const (
// ConsulPolicyWrite is the literal text of the policy field of a Consul Policy
// Rule that we check when validating an Operator Consul token against the
// necessary permissions for creating a Service Identity token for a given
// service.
//
// The rule may be:
// - service.<exact>
// - service."*" (wildcard)
// - service_prefix.<matching> (including empty string)
//
// e.g.
// service "web" { policy = "write" }
// service_prefix "" { policy = "write" }
ConsulPolicyWrite = "write"
)
type ServiceIdentityRequest struct {
TaskKind structs.TaskKind
TaskName string
ClusterID string
AllocID string
}
func (sir ServiceIdentityRequest) Validate() error {
switch {
case sir.ClusterID == "":
return errors.New("cluster id not set")
case sir.AllocID == "":
return errors.New("alloc id not set")
case sir.TaskName == "":
return errors.New("task name not set")
case sir.TaskKind == "":
return errors.New("task kind not set")
default:
return nil
}
}
func (sir ServiceIdentityRequest) Description() string {
return fmt.Sprintf(siTokenDescriptionFmt, sir.ClusterID, sir.AllocID, sir.TaskName)
}
// ConsulACLsAPI is an abstraction over the consul/api.ACL API used by Nomad
// Server.
//
// ACL requirements
// - acl:write (transitive through ACLsAPI)
type ConsulACLsAPI interface {
// CheckSIPolicy checks that the given operator token has the equivalent ACL
// permissiveness that a Service Identity token policy for task would have.
CheckSIPolicy(ctx context.Context, task, secretID string) error
// Create instructs Consul to create a Service Identity token.
CreateToken(context.Context, ServiceIdentityRequest) (*structs.SIToken, error)
// RevokeTokens instructs Consul to revoke the given token accessors.
RevokeTokens(context.Context, []*structs.SITokenAccessor, bool) bool
// MarkForRevocation marks the tokens for background revocation
MarkForRevocation([]*structs.SITokenAccessor)
// Stop is used to stop background token revocations. Intended to be used
// on Nomad Server shutdown.
Stop()
// todo(shoenig): use list endpoint for finding orphaned tokens
// ListTokens lists every token in Consul.
// ListTokens() ([]string, error)
}
// PurgeSITokenAccessorFunc is called to remove SI Token accessors from the
// system (i.e. raft). If the function returns an error, the token will still
// be tracked and revocation attempts will retry in the background until there
// is a success.
type PurgeSITokenAccessorFunc func([]*structs.SITokenAccessor) error
type SITokenStats struct {
TrackedForRevoke int
}
type consulACLsAPI struct {
// aclClient is the API subset of the real consul client we need for
// managing Service Identity tokens
aclClient consul.ACLsAPI
// limiter is used to rate limit requests to consul
limiter *rate.Limiter
bgRevokeLock sync.Mutex
// Track accessors that must have their revocation retried in the background.
bgRetryRevocation []*structs.SITokenAccessor
// Track whether the background revocations have been stopped, to avoid
// creating tokens we would no longer be able to revoke. Expected to be used
// on a Server shutdown.
bgRevokeStopped bool
// purgeFunc is the Nomad Server function that removes the reference to the
// SI token accessor from the persistent raft store
purgeFunc PurgeSITokenAccessorFunc
// stopC is used to signal the client is shutting down and token revocation
// background goroutine should stop
stopC chan struct{}
// logger is used to log messages
logger hclog.Logger
}
func NewConsulACLsAPI(aclClient consul.ACLsAPI, logger hclog.Logger, purgeFunc PurgeSITokenAccessorFunc) *consulACLsAPI {
if purgeFunc == nil {
purgeFunc = func([]*structs.SITokenAccessor) error { return nil }
}
c := &consulACLsAPI{
aclClient: aclClient,
limiter: rate.NewLimiter(siTokenRequestRateLimit, int(siTokenRequestRateLimit)),
stopC: make(chan struct{}),
purgeFunc: purgeFunc,
logger: logger.Named("consul_acl"),
}
go c.bgRetryRevokeDaemon()
return c
}
// Stop stops background token revocations from happening. Once stopped, tokens
// may no longer be created.
func (c *consulACLsAPI) Stop() {
c.bgRevokeLock.Lock()
defer c.bgRevokeLock.Unlock()
c.stopC <- struct{}{}
c.bgRevokeStopped = true
}
func (c *consulACLsAPI) CheckSIPolicy(ctx context.Context, task, secretID string) error {
defer metrics.MeasureSince([]string{"nomad", "consul", "check_si_policy"}, time.Now())
if id := strings.TrimSpace(secretID); id == "" {
return errors.New("missing consul token")
}
// Ensure we are under our rate limit.
if err := c.limiter.Wait(ctx); err != nil {
return err
}
opToken, _, err := c.aclClient.TokenReadSelf(&api.QueryOptions{
AllowStale: false,
Token: secretID,
})
if err != nil {
return errors.Wrap(err, "unable to validate operator consul token")
}
allowable, err := c.hasSufficientPolicy(task, opToken)
if err != nil {
return errors.Wrap(err, "unable to validate operator consul token")
}
if !allowable {
return errors.Errorf("permission denied for %q", task)
}
return nil
}
func (c *consulACLsAPI) CreateToken(ctx context.Context, sir ServiceIdentityRequest) (*structs.SIToken, error) {
defer metrics.MeasureSince([]string{"nomad", "consul", "create_token"}, time.Now())
// make sure the background token revocations have not been stopped
c.bgRevokeLock.Lock()
stopped := c.bgRevokeStopped
c.bgRevokeLock.Unlock()
if stopped {
return nil, errors.New("client stopped and may no longer create tokens")
}
// sanity check the metadata for the token we want
if err := sir.Validate(); err != nil {
return nil, err
}
// the SI token created must be for the service, not the sidecar of the service
// https://www.consul.io/docs/acl/acl-system.html#acl-service-identities
service := sir.TaskKind.Value()
partial := &api.ACLToken{
Description: sir.Description(),
ServiceIdentities: []*api.ACLServiceIdentity{{ServiceName: service}},
}
// Ensure we are under our rate limit.
if err := c.limiter.Wait(ctx); err != nil {
return nil, err
}
token, _, err := c.aclClient.TokenCreate(partial, nil)
if err != nil {
return nil, err
}
return &structs.SIToken{
TaskName: sir.TaskName,
AccessorID: token.AccessorID,
SecretID: token.SecretID,
}, nil
}
// RevokeTokens revokes the passed set of SI token accessors. If committed is set,
// the client's purge function is called (which purges the tokens from the Server's
// persistent store). If there is an error purging either because of Consul failures
// or because of the purge function, the revocation is retried in the background.
//
// The revocation of an SI token accessor is idempotent.
//
// A return value of true indicates one or more accessors were stored for
// a revocation retry attempt in the background (intended for tests).
func (c *consulACLsAPI) RevokeTokens(ctx context.Context, accessors []*structs.SITokenAccessor, committed bool) bool {
defer metrics.MeasureSince([]string{"nomad", "consul", "revoke_tokens"}, time.Now())
nTokens := float32(len(accessors))
if err := c.parallelRevoke(ctx, accessors); err != nil {
// If these tokens were uncommitted into raft, it is a best effort to
// revoke them now. If this immediate revocation does not work, Nomad loses
// track of them and will need to do a brute reconciliation later. This
// should happen rarely, and will be implemented soon.
if !committed {
metrics.IncrCounter([]string{"nomad", "consul", "undistributed_si_tokens_abandoned"}, nTokens)
}
c.logger.Warn("failed to revoke tokens, will reattempt later", "error", err)
c.storeForRevocation(accessors)
return true
}
if !committed {
// Un-committed tokens were revoked without incident (nothing to purge)
metrics.IncrCounter([]string{"nomad", "consul", "undistributed_si_tokens_revoked"}, nTokens)
return false
}
// Committed tokens were revoked without incident, now purge them
if err := c.purgeFunc(accessors); err != nil {
c.logger.Error("failed to purge SI token accessors", "error", err)
c.storeForRevocation(accessors)
return true
}
// Track that the SI tokens were revoked and purged successfully
metrics.IncrCounter([]string{"nomad", "consul", "distributed_si_tokens_revoked"}, nTokens)
return false
}
func (c *consulACLsAPI) MarkForRevocation(accessors []*structs.SITokenAccessor) {
c.storeForRevocation(accessors)
}
func (c *consulACLsAPI) storeForRevocation(accessors []*structs.SITokenAccessor) {
c.bgRevokeLock.Lock()
defer c.bgRevokeLock.Unlock()
// copy / append the set of accessors we must track for revocation in the
// background
c.bgRetryRevocation = append(c.bgRetryRevocation, accessors...)
}
func (c *consulACLsAPI) parallelRevoke(ctx context.Context, accessors []*structs.SITokenAccessor) error {
g, pCtx := errgroup.WithContext(ctx)
// Cap the handlers
handlers := len(accessors)
if handlers > siTokenMaxParallelRevokes {
handlers = siTokenMaxParallelRevokes
}
// Revoke the SI Token Accessors
input := make(chan *structs.SITokenAccessor, handlers)
for i := 0; i < handlers; i++ {
g.Go(func() error {
for {
select {
case accessor, ok := <-input:
if !ok {
return nil
}
if err := c.singleRevoke(ctx, accessor); err != nil {
return errors.Wrapf(err,
"failed to revoke SI token accessor (alloc %q, node %q, task %q)",
accessor.AllocID, accessor.NodeID, accessor.TaskName,
)
}
case <-pCtx.Done():
return nil
}
}
})
}
// Send the input
go func() {
defer close(input)
for _, accessor := range accessors {
select {
case <-pCtx.Done():
return
case input <- accessor:
}
}
}()
// Wait for everything to complete
return g.Wait()
}
func (c *consulACLsAPI) singleRevoke(ctx context.Context, accessor *structs.SITokenAccessor) error {
c.logger.Trace("revoke SI token", "task", accessor.TaskName, "alloc_id", accessor.AllocID, "node_id", accessor.NodeID)
// Ensure we are under our rate limit.
if err := c.limiter.Wait(ctx); err != nil {
return err
}
// Consul will no-op the deletion of a non-existent token (no error)
_, err := c.aclClient.TokenDelete(accessor.AccessorID, nil)
return err
}
func (c *consulACLsAPI) bgRetryRevokeDaemon() {
ticker := time.NewTicker(siTokenRevocationInterval)
defer ticker.Stop()
for {
select {
case <-c.stopC:
return
case <-ticker.C:
c.bgRetryRevoke()
}
}
}
// maxConsulRevocationBatchSize is the maximum tokens a bgRetryRevoke should revoke
// at any given time.
const maxConsulRevocationBatchSize = 1000
func (c *consulACLsAPI) bgRetryRevoke() {
c.bgRevokeLock.Lock()
defer c.bgRevokeLock.Unlock()
// fast path, nothing to do
if len(c.bgRetryRevocation) == 0 {
return
}
// unlike vault tokens, SI tokens do not have a TTL, and so we must try to
// remove all SI token accessors, every time, until they're gone
toRevoke := len(c.bgRetryRevocation)
if toRevoke > maxConsulRevocationBatchSize {
toRevoke = maxConsulRevocationBatchSize
}
toPurge := make([]*structs.SITokenAccessor, toRevoke)
copy(toPurge, c.bgRetryRevocation)
if err := c.parallelRevoke(context.Background(), toPurge); err != nil {
c.logger.Warn("background SI token revocation failed", "error", err)
return
}
// Call the revocation function
if err := c.purgeFunc(toPurge); err != nil {
// Just try again later (revocation is idempotent)
c.logger.Error("background SI token purge failed", "error", err)
return
}
// Track that the SI tokens were revoked successfully
nTokens := float32(len(toPurge))
metrics.IncrCounter([]string{"nomad", "consul", "distributed_tokens_revoked"}, nTokens)
// Reset the list of accessors to retry, since we just removed them all.
c.bgRetryRevocation = nil
}
func (c *consulACLsAPI) ListTokens() ([]string, error) {
// defer metrics.MeasureSince([]string{"nomad", "consul", "list_tokens"}, time.Now())
return nil, errors.New("not yet implemented")
}
// purgeSITokenAccessors is the Nomad Server method which will remove the set
// of SI token accessors from the persistent raft store.
func (s *Server) purgeSITokenAccessors(accessors []*structs.SITokenAccessor) error {
// Commit this update via Raft
request := structs.SITokenAccessorsRequest{Accessors: accessors}
_, _, err := s.raftApply(structs.ServiceIdentityAccessorDeregisterRequestType, request)
return err
}