open-consul/connect/service.go

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package connect
import (
"context"
"crypto/tls"
"crypto/x509"
"errors"
"log"
"net"
"net/http"
"os"
"time"
"github.com/hashicorp/consul/api"
"github.com/hashicorp/consul/api/watch"
"golang.org/x/net/http2"
)
// Service represents a Consul service that accepts and/or connects via Connect.
// This can represent a service that only is a server, only is a client, or
// both.
//
// TODO(banks): Agent implicit health checks based on knowing which certs are
// available should prevent clients being routed until the agent knows the
// service has been delivered valid certificates. Once built, document that here
// too.
type Service struct {
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// service is the name (not ID) for the Consul service. This is used to request
// Connect metadata.
service string
// client is the Consul API client. It must be configured with an appropriate
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// Token that has `service:write` policy on the provided service. If an
// insufficient token is provided, the Service will abort further attempts to
// fetch certificates and print a loud error message. It will not Close() or
// kill the process since that could lead to a crash loop in every service if
// ACL token was revoked. All attempts to dial will error and any incoming
// connections will fail to verify. It may be nil if the Service is being
// configured from local files for development or testing.
client *api.Client
// tlsCfg is the dynamic TLS config
tlsCfg *dynamicTLSConfig
// httpResolverFromAddr is a function that returns a Resolver from a string
// address for HTTP clients. It's privately pluggable to make testing easier
// but will default to a simple method to parse the host as a Consul DNS host.
httpResolverFromAddr func(addr string) (Resolver, error)
rootsWatch *watch.Plan
leafWatch *watch.Plan
logger *log.Logger
}
// NewService creates and starts a Service. The caller must close the returned
// service to free resources and allow the program to exit normally. This is
// typically called in a signal handler.
//
// Caller must provide client which is already configured to speak to the local
// Consul agent, and with an ACL token that has `service:write` privileges for
// the service specified.
func NewService(serviceName string, client *api.Client) (*Service, error) {
return NewServiceWithLogger(serviceName, client,
log.New(os.Stderr, "", log.LstdFlags))
}
// NewServiceWithLogger starts the service with a specified log.Logger.
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func NewServiceWithLogger(serviceName string, client *api.Client,
logger *log.Logger) (*Service, error) {
s := &Service{
service: serviceName,
client: client,
logger: logger,
tlsCfg: newDynamicTLSConfig(defaultTLSConfig(), logger),
httpResolverFromAddr: ConsulResolverFromAddrFunc(client),
}
// Set up root and leaf watches
p, err := watch.Parse(map[string]interface{}{
"type": "connect_roots",
})
if err != nil {
return nil, err
}
s.rootsWatch = p
s.rootsWatch.HybridHandler = s.rootsWatchHandler
p, err = watch.Parse(map[string]interface{}{
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"type": "connect_leaf",
"service": s.service,
})
if err != nil {
return nil, err
}
s.leafWatch = p
s.leafWatch.HybridHandler = s.leafWatchHandler
go s.rootsWatch.RunWithClientAndLogger(client, s.logger)
go s.leafWatch.RunWithClientAndLogger(client, s.logger)
return s, nil
}
// NewDevServiceFromCertFiles creates a Service using certificate and key files
// passed instead of fetching them from the client.
func NewDevServiceFromCertFiles(serviceID string, logger *log.Logger,
caFile, certFile, keyFile string) (*Service, error) {
tlsCfg, err := devTLSConfigFromFiles(caFile, certFile, keyFile)
if err != nil {
return nil, err
}
return NewDevServiceWithTLSConfig(serviceID, logger, tlsCfg)
}
// NewDevServiceWithTLSConfig creates a Service using static TLS config passed.
// It's mostly useful for testing.
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func NewDevServiceWithTLSConfig(serviceName string, logger *log.Logger,
tlsCfg *tls.Config) (*Service, error) {
s := &Service{
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service: serviceName,
logger: logger,
tlsCfg: newDynamicTLSConfig(tlsCfg, logger),
}
return s, nil
}
// Name returns the name of the service this object represents. Note it is the
// service _name_ as used during discovery, not the ID used to uniquely identify
// an instance of the service with an agent.
func (s *Service) Name() string {
return s.service
}
// ServerTLSConfig returns a *tls.Config that allows any TCP listener to accept
// and authorize incoming Connect clients. It will return a single static config
// with hooks to dynamically load certificates, and perform Connect
// authorization during verification. Service implementations do not need to
// reload this to get new certificates.
//
// At any time it may be possible that the Service instance does not have access
// to usable certificates due to not being initially setup yet or a prolonged
// error during renewal. The listener will be able to accept connections again
// once connectivity is restored provided the client's Token is valid.
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//
// To prevent routing traffic to the app instance while it's certificates are
// invalid or not populated yet you may use Ready in a health check endpoint
// and/or ReadyWait during startup before starting the TLS listener. The latter
// only prevents connections during initial bootstrap (including permission
// issues where certs can never be issued due to bad credentials) but won't
// handle the case that certificates expire and an error prevents timely
// renewal.
func (s *Service) ServerTLSConfig() *tls.Config {
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return s.tlsCfg.Get(newServerSideVerifier(s.client, s.service))
}
// Dial connects to a remote Connect-enabled server. The passed Resolver is used
// to discover a single candidate instance which will be dialed and have it's
// TLS certificate verified against the expected identity. Failures are returned
// directly with no retries. Repeated dials may use different instances
// depending on the Resolver implementation.
//
// Timeout can be managed via the Context.
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//
// Calls to Dial made before the Service has loaded certificates from the agent
// will fail. You can prevent this by using Ready or ReadyWait in app during
// startup.
func (s *Service) Dial(ctx context.Context, resolver Resolver) (net.Conn, error) {
addr, certURI, err := resolver.Resolve(ctx)
if err != nil {
return nil, err
}
s.logger.Printf("[DEBUG] resolved service instance: %s (%s)", addr,
certURI.URI())
var dialer net.Dialer
tcpConn, err := dialer.DialContext(ctx, "tcp", addr)
if err != nil {
return nil, err
}
tlsConn := tls.Client(tcpConn, s.tlsCfg.Get(clientSideVerifier))
// Set deadline for Handshake to complete.
deadline, ok := ctx.Deadline()
if ok {
tlsConn.SetDeadline(deadline)
}
// Perform handshake
if err = tlsConn.Handshake(); err != nil {
tlsConn.Close()
return nil, err
}
// Clear deadline since that was only for connection. Caller can set their own
// deadline later as necessary.
tlsConn.SetDeadline(time.Time{})
// Verify that the connect server's URI matches certURI
err = verifyServerCertMatchesURI(tlsConn.ConnectionState().PeerCertificates,
certURI)
if err != nil {
tlsConn.Close()
return nil, err
}
s.logger.Printf("[DEBUG] successfully connected to %s (%s)", addr,
certURI.URI())
return tlsConn, nil
}
// HTTPDialTLS is compatible with http.Transport.DialTLS. It expects the addr
// hostname to be specified using Consul DNS query syntax, e.g.
// "web.service.consul". It converts that into the equivalent ConsulResolver and
// then call s.Dial with the resolver. This is low level, clients should
// typically use HTTPClient directly.
func (s *Service) HTTPDialTLS(network,
addr string) (net.Conn, error) {
if s.httpResolverFromAddr == nil {
return nil, errors.New("no http resolver configured")
}
r, err := s.httpResolverFromAddr(addr)
if err != nil {
return nil, err
}
// TODO(banks): figure out how to do timeouts better.
return s.Dial(context.Background(), r)
}
// HTTPClient returns an *http.Client configured to dial remote Consul Connect
// HTTP services. The client will return an error if attempting to make requests
// to a non HTTPS hostname. It resolves the domain of the request with the same
// syntax as Consul DNS queries although it performs discovery directly via the
// API rather than just relying on Consul DNS. Hostnames that are not valid
// Consul DNS queries will fail.
func (s *Service) HTTPClient() *http.Client {
t := &http.Transport{
// Sadly we can't use DialContext hook since that is expected to return a
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// plain TCP connection and http.Client tries to start a TLS handshake over
// it. We need to control the handshake to be able to do our validation.
// So we have to use the older DialTLS which means no context/timeout
// support.
//
// TODO(banks): figure out how users can configure a timeout when using
// this and/or compatibility with http.Request.WithContext.
DialTLS: s.HTTPDialTLS,
}
// Need to manually re-enable http2 support since we set custom DialTLS.
// See https://golang.org/src/net/http/transport.go?s=8692:9036#L228
http2.ConfigureTransport(t)
return &http.Client{
Transport: t,
}
}
// Close stops the service and frees resources.
func (s *Service) Close() error {
if s.rootsWatch != nil {
s.rootsWatch.Stop()
}
if s.leafWatch != nil {
s.leafWatch.Stop()
}
return nil
}
func (s *Service) rootsWatchHandler(blockParam watch.BlockingParamVal, raw interface{}) {
if raw == nil {
return
}
v, ok := raw.(*api.CARootList)
if !ok || v == nil {
s.logger.Println("[ERR] got invalid response from root watch")
return
}
// Got new root certificates, update the tls.Configs.
roots := x509.NewCertPool()
for _, root := range v.Roots {
roots.AppendCertsFromPEM([]byte(root.RootCertPEM))
}
s.tlsCfg.SetRoots(roots)
}
func (s *Service) leafWatchHandler(blockParam watch.BlockingParamVal, raw interface{}) {
if raw == nil {
return // ignore
}
v, ok := raw.(*api.LeafCert)
if !ok || v == nil {
s.logger.Println("[ERR] got invalid response from root watch")
return
}
// Got new leaf, update the tls.Configs
cert, err := tls.X509KeyPair([]byte(v.CertPEM), []byte(v.PrivateKeyPEM))
if err != nil {
s.logger.Printf("[ERR] failed to parse new leaf cert: %s", err)
return
}
s.tlsCfg.SetLeaf(&cert)
}
// Ready returns whether or not both roots and a leaf certificate are
// configured. If both are non-nil, they are assumed to be valid and usable.
func (s *Service) Ready() bool {
return s.tlsCfg.Ready()
}
// ReadyWait returns a chan that is closed when the the Service becomes ready
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// for use for the first time. Note that if the Service is ready when it is
// called it returns a nil chan. Ready means that it has root and leaf
// certificates configured which we assume are valid. The service may
// subsequently stop being "ready" if it's certificates expire or are revoked
// and an error prevents new ones being loaded but this method will not stop
// returning a nil chan in that case. It is only useful for initial startup. For
// ongoing health Ready() should be used.
func (s *Service) ReadyWait() <-chan struct{} {
return s.tlsCfg.ReadyWait()
}