package consul import ( "context" "errors" "fmt" "reflect" "strings" "sync" "time" "github.com/hashicorp/consul/lib/semaphore" "golang.org/x/time/rate" "github.com/hashicorp/consul/acl" "github.com/hashicorp/consul/agent/connect" "github.com/hashicorp/consul/agent/consul/state" "github.com/hashicorp/consul/agent/structs" "github.com/hashicorp/go-memdb" ) var ( // Err strings. net/rpc doesn't have a way to transport typed/rich errors so // we currently rely on sniffing the error string in a few cases where we need // to change client behavior. These are the canonical error strings to use. // Note though that client code can't use `err == consul.Err*` directly since // the error returned by RPC will be a plain error.errorString created by // net/rpc client so will not be the same _instance_ that this package // variable points to. Clients need to compare using `err.Error() == // consul.ErrRateLimited.Error()` which is very sad. Short of replacing our // RPC mechanism it's hard to know how to make that much better though. ErrConnectNotEnabled = errors.New("Connect must be enabled in order to use this endpoint") ErrRateLimited = errors.New("Rate limit reached, try again later") ) const ( // csrLimitWait is the maximum time we'll wait for a slot when CSR concurrency // limiting or rate limiting is occuring. It's intentionally short so small // batches of requests can be accommodated when server has capacity (assuming // signing one cert takes much less than this) but failing requests fast when // a thundering herd comes along. csrLimitWait = 500 * time.Millisecond ) // ConnectCA manages the Connect CA. type ConnectCA struct { // srv is a pointer back to the server. srv *Server // csrRateLimiter limits the rate of signing new certs if configured. Lazily // initialized from current config to support dynamic changes. // csrRateLimiterMu must be held while dereferencing the pointer or storing a // new one, but methods can be called on the limiter object outside of the // locked section. This is done only in the getCSRRateLimiterWithLimit method. csrRateLimiter *rate.Limiter csrRateLimiterMu sync.RWMutex // csrConcurrencyLimiter is a dynamically resizable semaphore used to limit // Sign RPC concurrency if configured. The zero value is usable as soon as // SetSize is called which we do dynamically in the RPC handler to avoid // having to hook elaborate synchronization mechanisms through the CA config // endpoint and config reload etc. csrConcurrencyLimiter semaphore.Dynamic } // getCSRRateLimiterWithLimit returns a rate.Limiter with the desired limit set. // It uses the shared server-wide limiter unless the limit has been changed in // config or the limiter has not been setup yet in which case it just-in-time // configures the new limiter. We assume that limit changes are relatively rare // and that all callers (there is currently only one) use the same config value // as the limit. There might be some flapping if there are multiple concurrent // requests in flight at the time the config changes where A sees the new value // and updates, B sees the old but then gets this lock second and changes back. // Eventually though and very soon (once all current RPCs are complete) we are // guaranteed to have the correct limit set by the next RPC that comes in so I // assume this is fine. If we observe strange behavior because of it, we could // add hysteresis that prevents changes too soon after a previous change but // that seems unnecessary for now. func (s *ConnectCA) getCSRRateLimiterWithLimit(limit rate.Limit) *rate.Limiter { s.csrRateLimiterMu.RLock() lim := s.csrRateLimiter s.csrRateLimiterMu.RUnlock() // If there is a current limiter with the same limit, return it. This should // be the common case. if lim != nil && lim.Limit() == limit { return lim } // Need to change limiter, get write lock s.csrRateLimiterMu.Lock() defer s.csrRateLimiterMu.Unlock() // No limiter yet, or limit changed in CA config, reconfigure a new limiter. // We use burst of 1 for a hard limit. Note that either bursting or waiting is // necessary to get expected behavior in fact of random arrival times, but we // don't need both and we use Wait with a small delay to smooth noise. See // https://github.com/banks/sim-rate-limit-backoff/blob/master/README.md. s.csrRateLimiter = rate.NewLimiter(limit, 1) return s.csrRateLimiter } // ConfigurationGet returns the configuration for the CA. func (s *ConnectCA) ConfigurationGet( args *structs.DCSpecificRequest, reply *structs.CAConfiguration) error { // Exit early if Connect hasn't been enabled. if !s.srv.config.ConnectEnabled { return ErrConnectNotEnabled } if done, err := s.srv.forward("ConnectCA.ConfigurationGet", args, args, reply); done { return err } // This action requires operator read access. rule, err := s.srv.ResolveToken(args.Token) if err != nil { return err } if rule != nil && !rule.OperatorRead() { return acl.ErrPermissionDenied } state := s.srv.fsm.State() _, config, err := state.CAConfig() if err != nil { return err } *reply = *config return nil } // ConfigurationSet updates the configuration for the CA. func (s *ConnectCA) ConfigurationSet( args *structs.CARequest, reply *interface{}) error { // Exit early if Connect hasn't been enabled. if !s.srv.config.ConnectEnabled { return ErrConnectNotEnabled } if done, err := s.srv.forward("ConnectCA.ConfigurationSet", args, args, reply); done { return err } // This action requires operator write access. rule, err := s.srv.ResolveToken(args.Token) if err != nil { return err } if rule != nil && !rule.OperatorWrite() { return acl.ErrPermissionDenied } // Exit early if it's a no-op change state := s.srv.fsm.State() confIdx, config, err := state.CAConfig() if err != nil { return err } // Don't allow users to change the ClusterID. args.Config.ClusterID = config.ClusterID if args.Config.Provider == config.Provider && reflect.DeepEqual(args.Config.Config, config.Config) { return nil } // Create a new instance of the provider described by the config // and get the current active root CA. This acts as a good validation // of the config and makes sure the provider is functioning correctly // before we commit any changes to Raft. newProvider, err := s.srv.createCAProvider(args.Config) if err != nil { return fmt.Errorf("could not initialize provider: %v", err) } if err := newProvider.Configure(args.Config.ClusterID, true, args.Config.Config); err != nil { return fmt.Errorf("error configuring provider: %v", err) } if err := newProvider.GenerateRoot(); err != nil { return fmt.Errorf("error generating CA root certificate: %v", err) } newRootPEM, err := newProvider.ActiveRoot() if err != nil { return err } newActiveRoot, err := parseCARoot(newRootPEM, args.Config.Provider, args.Config.ClusterID) if err != nil { return err } // Compare the new provider's root CA ID to the current one. If they // match, just update the existing provider with the new config. // If they don't match, begin the root rotation process. _, root, err := state.CARootActive(nil) if err != nil { return err } // If the root didn't change or if this is a secondary DC, just update the // config and return. if (s.srv.config.Datacenter != s.srv.config.PrimaryDatacenter) || root != nil && root.ID == newActiveRoot.ID { args.Op = structs.CAOpSetConfig resp, err := s.srv.raftApply(structs.ConnectCARequestType, args) if err != nil { return err } if respErr, ok := resp.(error); ok { return respErr } // If the config has been committed, update the local provider instance s.srv.setCAProvider(newProvider, newActiveRoot) s.srv.logger.Printf("[INFO] connect: CA provider config updated") return nil } // At this point, we know the config change has trigged a root rotation, // either by swapping the provider type or changing the provider's config // to use a different root certificate. // If it's a config change that would trigger a rotation (different provider/root): // 1. Get the root from the new provider. // 2. Call CrossSignCA on the old provider to sign the new root with the old one to // get a cross-signed certificate. // 3. Take the active root for the new provider and append the intermediate from step 2 // to its list of intermediates. newRoot, err := connect.ParseCert(newRootPEM) if err != nil { return err } // Have the old provider cross-sign the new intermediate oldProvider, _ := s.srv.getCAProvider() if oldProvider == nil { return fmt.Errorf("internal error: CA provider is nil") } xcCert, err := oldProvider.CrossSignCA(newRoot) if err != nil { return err } // Add the cross signed cert to the new root's intermediates. newActiveRoot.IntermediateCerts = []string{xcCert} intermediate, err := newProvider.GenerateIntermediate() if err != nil { return err } if intermediate != newRootPEM { newActiveRoot.IntermediateCerts = append(newActiveRoot.IntermediateCerts, intermediate) } // Update the roots and CA config in the state store at the same time idx, roots, err := state.CARoots(nil) if err != nil { return err } var newRoots structs.CARoots for _, r := range roots { newRoot := *r if newRoot.Active { newRoot.Active = false newRoot.RotatedOutAt = time.Now() } newRoots = append(newRoots, &newRoot) } newRoots = append(newRoots, newActiveRoot) args.Op = structs.CAOpSetRootsAndConfig args.Index = idx args.Config.ModifyIndex = confIdx args.Roots = newRoots resp, err := s.srv.raftApply(structs.ConnectCARequestType, args) if err != nil { return err } if respErr, ok := resp.(error); ok { return respErr } if respOk, ok := resp.(bool); ok && !respOk { return fmt.Errorf("could not atomically update roots and config") } // If the config has been committed, update the local provider instance // and call teardown on the old provider s.srv.setCAProvider(newProvider, newActiveRoot) if err := oldProvider.Cleanup(); err != nil { s.srv.logger.Printf("[WARN] connect: failed to clean up old provider %q", config.Provider) } s.srv.logger.Printf("[INFO] connect: CA rotated to new root under provider %q", args.Config.Provider) return nil } // Roots returns the currently trusted root certificates. func (s *ConnectCA) Roots( args *structs.DCSpecificRequest, reply *structs.IndexedCARoots) error { // Forward if necessary if done, err := s.srv.forward("ConnectCA.Roots", args, args, reply); done { return err } // Exit early if Connect hasn't been enabled. if !s.srv.config.ConnectEnabled { return ErrConnectNotEnabled } // Load the ClusterID to generate TrustDomain. We do this outside the loop // since by definition this value should be immutable once set for lifetime of // the cluster so we don't need to look it up more than once. We also don't // have to worry about non-atomicity between the config fetch transaction and // the CARoots transaction below since this field must remain immutable. Do // not re-use this state/config for other logic that might care about changes // of config during the blocking query below. { state := s.srv.fsm.State() _, config, err := state.CAConfig() if err != nil { return err } // Check CA is actually bootstrapped... if config != nil { // Build TrustDomain based on the ClusterID stored. signingID := connect.SpiffeIDSigningForCluster(config) if signingID == nil { // If CA is bootstrapped at all then this should never happen but be // defensive. return errors.New("no cluster trust domain setup") } reply.TrustDomain = signingID.Host() } } return s.srv.blockingQuery( &args.QueryOptions, &reply.QueryMeta, func(ws memdb.WatchSet, state *state.Store) error { index, roots, err := state.CARoots(ws) if err != nil { return err } reply.Index, reply.Roots = index, roots if reply.Roots == nil { reply.Roots = make(structs.CARoots, 0) } // The API response must NEVER contain the secret information // such as keys and so on. We use a whitelist below to copy the // specific fields we want to expose. for i, r := range reply.Roots { // IMPORTANT: r must NEVER be modified, since it is a pointer // directly to the structure in the memdb store. reply.Roots[i] = &structs.CARoot{ ID: r.ID, Name: r.Name, SerialNumber: r.SerialNumber, SigningKeyID: r.SigningKeyID, ExternalTrustDomain: r.ExternalTrustDomain, NotBefore: r.NotBefore, NotAfter: r.NotAfter, RootCert: r.RootCert, IntermediateCerts: r.IntermediateCerts, RaftIndex: r.RaftIndex, Active: r.Active, } if r.Active { reply.ActiveRootID = r.ID } } return nil }, ) } // Sign signs a certificate for a service. func (s *ConnectCA) Sign( args *structs.CASignRequest, reply *structs.IssuedCert) error { // Exit early if Connect hasn't been enabled. if !s.srv.config.ConnectEnabled { return ErrConnectNotEnabled } if done, err := s.srv.forward("ConnectCA.Sign", args, args, reply); done { return err } // Parse the CSR csr, err := connect.ParseCSR(args.CSR) if err != nil { return err } // Parse the SPIFFE ID spiffeID, err := connect.ParseCertURI(csr.URIs[0]) if err != nil { return err } serviceID, ok := spiffeID.(*connect.SpiffeIDService) if !ok { return fmt.Errorf("SPIFFE ID in CSR must be a service ID") } provider, caRoot := s.srv.getCAProvider() if provider == nil { return fmt.Errorf("internal error: CA provider is nil") } // Verify that the CSR entity is in the cluster's trust domain state := s.srv.fsm.State() _, config, err := state.CAConfig() if err != nil { return err } signingID := connect.SpiffeIDSigningForCluster(config) if !signingID.CanSign(serviceID) { return fmt.Errorf("SPIFFE ID in CSR from a different trust domain: %s, "+ "we are %s", serviceID.Host, signingID.Host()) } // Verify that the ACL token provided has permission to act as this service rule, err := s.srv.ResolveToken(args.Token) if err != nil { return err } if rule != nil && !rule.ServiceWrite(serviceID.Service, nil) { return acl.ErrPermissionDenied } // Verify that the DC in the service URI matches us. We might relax this // requirement later but being restrictive for now is safer. if serviceID.Datacenter != s.srv.config.Datacenter { return fmt.Errorf("SPIFFE ID in CSR from a different datacenter: %s, "+ "we are %s", serviceID.Datacenter, s.srv.config.Datacenter) } commonCfg, err := config.GetCommonConfig() if err != nil { return err } if commonCfg.CSRMaxPerSecond > 0 { lim := s.getCSRRateLimiterWithLimit(rate.Limit(commonCfg.CSRMaxPerSecond)) // Wait up to the small threshold we allow for a token. ctx, cancel := context.WithTimeout(context.Background(), csrLimitWait) defer cancel() if lim.Wait(ctx) != nil { return ErrRateLimited } } else if commonCfg.CSRMaxConcurrent > 0 { s.csrConcurrencyLimiter.SetSize(int64(commonCfg.CSRMaxConcurrent)) ctx, cancel := context.WithTimeout(context.Background(), csrLimitWait) defer cancel() if err := s.csrConcurrencyLimiter.Acquire(ctx); err != nil { return ErrRateLimited } defer s.csrConcurrencyLimiter.Release() } // All seems to be in order, actually sign it. pem, err := provider.Sign(csr) if err != nil { return err } // Append any intermediates needed by this root. for _, p := range caRoot.IntermediateCerts { pem = strings.TrimSpace(pem) + "\n" + p } // Append our local CA's intermediate if there is one. inter, err := provider.ActiveIntermediate() if err != nil { return err } root, err := provider.ActiveRoot() if err != nil { return err } if inter != root { pem = strings.TrimSpace(pem) + "\n" + inter } // TODO(banks): when we implement IssuedCerts table we can use the insert to // that as the raft index to return in response. // // UPDATE(mkeeler): The original implementation relied on updating the CAConfig // and using its index as the ModifyIndex for certs. This was buggy. The long // term goal is still to insert some metadata into raft about the certificates // and use that raft index for the ModifyIndex. This is a partial step in that // direction except that we only are setting an index and not storing the // metadata. req := structs.CALeafRequest{ Op: structs.CALeafOpIncrementIndex, Datacenter: s.srv.config.Datacenter, WriteRequest: structs.WriteRequest{Token: args.Token}, } resp, err := s.srv.raftApply(structs.ConnectCALeafRequestType|structs.IgnoreUnknownTypeFlag, &req) if err != nil { return err } modIdx, ok := resp.(uint64) if !ok { return fmt.Errorf("Invalid response from updating the leaf cert index") } cert, err := connect.ParseCert(pem) if err != nil { return err } // Set the response *reply = structs.IssuedCert{ SerialNumber: connect.HexString(cert.SerialNumber.Bytes()), CertPEM: pem, Service: serviceID.Service, ServiceURI: cert.URIs[0].String(), ValidAfter: cert.NotBefore, ValidBefore: cert.NotAfter, RaftIndex: structs.RaftIndex{ ModifyIndex: modIdx, CreateIndex: modIdx, }, } return nil }