traefik/pkg/provider/tailscale/provider.go

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package tailscale
import (
"context"
"crypto/tls"
"crypto/x509"
"sort"
"strings"
"sync"
"time"
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"github.com/rs/zerolog/log"
"github.com/tailscale/tscert"
"github.com/traefik/traefik/v2/pkg/config/dynamic"
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"github.com/traefik/traefik/v2/pkg/logs"
"github.com/traefik/traefik/v2/pkg/muxer/http"
"github.com/traefik/traefik/v2/pkg/muxer/tcp"
"github.com/traefik/traefik/v2/pkg/safe"
traefiktls "github.com/traefik/traefik/v2/pkg/tls"
)
// Provider is the Tailscale certificates provider implementation. It receives
// configuration updates (e.g. new router, with new domain) from Traefik core,
// fetches the corresponding TLS certificates from the Tailscale daemon, and
// sends back to Traefik core a configuration updated with the certificates.
type Provider struct {
ResolverName string
dynConfigs chan dynamic.Configuration // updates from Traefik core
dynMessages chan<- dynamic.Message // update to Traefik core
certByDomainMu sync.RWMutex
certByDomain map[string]traefiktls.Certificate
}
// ThrottleDuration implements the aggregator.throttled interface, in order to
// ensure that this provider is unthrottled.
func (p *Provider) ThrottleDuration() time.Duration {
return 0
}
// Init implements the provider.Provider interface.
func (p *Provider) Init() error {
p.dynConfigs = make(chan dynamic.Configuration)
p.certByDomain = make(map[string]traefiktls.Certificate)
return nil
}
// HandleConfigUpdate hands out a configuration update to the provider.
func (p *Provider) HandleConfigUpdate(cfg dynamic.Configuration) {
p.dynConfigs <- cfg
}
// Provide starts the provider, which will henceforth send configuration
// updates on dynMessages.
func (p *Provider) Provide(dynMessages chan<- dynamic.Message, pool *safe.Pool) error {
p.dynMessages = dynMessages
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logger := log.With().Str(logs.ProviderName, p.ResolverName+".tailscale").Logger()
pool.GoCtx(func(ctx context.Context) {
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p.watchDomains(logger.WithContext(ctx))
})
pool.GoCtx(func(ctx context.Context) {
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p.renewCertificates(logger.WithContext(ctx))
})
return nil
}
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// watchDomains watches for Tailscale domain certificates that should be fetched from the Tailscale daemon.
func (p *Provider) watchDomains(ctx context.Context) {
for {
select {
case <-ctx.Done():
return
case cfg := <-p.dynConfigs:
domains := p.findDomains(ctx, cfg)
newDomains := p.findNewDomains(domains)
purged := p.purgeUnusedCerts(domains)
if len(newDomains) == 0 && !purged {
continue
}
// TODO: what should we do if the fetched certificate is going to expire before the next refresh tick?
p.fetchCerts(ctx, newDomains)
p.sendDynamicConfig()
}
}
}
// renewCertificates routinely renews previously resolved Tailscale
// certificates before they expire.
func (p *Provider) renewCertificates(ctx context.Context) {
ticker := time.NewTicker(24 * time.Hour)
defer ticker.Stop()
for {
select {
case <-ctx.Done():
return
case <-ticker.C:
p.certByDomainMu.RLock()
var domainsToRenew []string
for domain, cert := range p.certByDomain {
tlsCert, err := cert.GetCertificateFromBytes()
if err != nil {
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log.Ctx(ctx).
Err(err).
Msgf("Unable to get certificate for domain %s", domain)
continue
}
// Tailscale tries to renew certificates 14 days before its expiration date.
// See https://github.com/tailscale/tailscale/blob/d9efbd97cbf369151e31453749f6692df7413709/ipn/localapi/cert.go#L116
if isValidCert(tlsCert, domain, time.Now().AddDate(0, 0, 14)) {
continue
}
domainsToRenew = append(domainsToRenew, domain)
}
p.certByDomainMu.RUnlock()
if len(domainsToRenew) == 0 {
continue
}
p.fetchCerts(ctx, domainsToRenew)
p.sendDynamicConfig()
}
}
}
// findDomains goes through the given dynamic.Configuration and returns all
// Tailscale-specific domains found.
func (p *Provider) findDomains(ctx context.Context, cfg dynamic.Configuration) []string {
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logger := log.Ctx(ctx)
var domains []string
if cfg.HTTP != nil {
for _, router := range cfg.HTTP.Routers {
if router.TLS == nil || router.TLS.CertResolver != p.ResolverName {
continue
}
// As a domain list is explicitly defined we are only using the
// configured domains. Only the Main domain is considered as
// Tailscale domain certificate does not support multiple SANs.
if len(router.TLS.Domains) > 0 {
for _, domain := range router.TLS.Domains {
domains = append(domains, domain.Main)
}
continue
}
parsedDomains, err := http.ParseDomains(router.Rule)
if err != nil {
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logger.Error().Err(err).Msg("Unable to parse HTTP router domains")
continue
}
domains = append(domains, parsedDomains...)
}
}
if cfg.TCP != nil {
for _, router := range cfg.TCP.Routers {
if router.TLS == nil || router.TLS.CertResolver != p.ResolverName {
continue
}
// As a domain list is explicitly defined we are only using the
// configured domains. Only the Main domain is considered as
// Tailscale domain certificate does not support multiple SANs.
if len(router.TLS.Domains) > 0 {
for _, domain := range router.TLS.Domains {
domains = append(domains, domain.Main)
}
continue
}
parsedDomains, err := tcp.ParseHostSNI(router.Rule)
if err != nil {
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logger.Error().Err(err).Msg("Unable to parse TCP router domains")
continue
}
domains = append(domains, parsedDomains...)
}
}
return sanitizeDomains(ctx, domains)
}
// findNewDomains returns the domains that have not already been fetched from
// the Tailscale daemon.
func (p *Provider) findNewDomains(domains []string) []string {
p.certByDomainMu.RLock()
defer p.certByDomainMu.RUnlock()
var newDomains []string
for _, domain := range domains {
if _, ok := p.certByDomain[domain]; ok {
continue
}
newDomains = append(newDomains, domain)
}
return newDomains
}
// purgeUnusedCerts purges the certByDomain map by removing unused certificates
// and returns whether some certificates have been removed.
func (p *Provider) purgeUnusedCerts(domains []string) bool {
p.certByDomainMu.Lock()
defer p.certByDomainMu.Unlock()
newCertByDomain := make(map[string]traefiktls.Certificate)
for _, domain := range domains {
if cert, ok := p.certByDomain[domain]; ok {
newCertByDomain[domain] = cert
}
}
purged := len(p.certByDomain) > len(newCertByDomain)
p.certByDomain = newCertByDomain
return purged
}
// fetchCerts fetches the certificates for the provided domains from the
// Tailscale daemon.
func (p *Provider) fetchCerts(ctx context.Context, domains []string) {
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logger := log.Ctx(ctx)
for _, domain := range domains {
cert, key, err := tscert.CertPair(ctx, domain)
if err != nil {
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logger.Error().Err(err).Msgf("Unable to fetch certificate for domain %q", domain)
continue
}
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logger.Debug().Msgf("Fetched certificate for domain %q", domain)
p.certByDomainMu.Lock()
p.certByDomain[domain] = traefiktls.Certificate{
CertFile: traefiktls.FileOrContent(cert),
KeyFile: traefiktls.FileOrContent(key),
}
p.certByDomainMu.Unlock()
}
}
// sendDynamicConfig sends a dynamic.Message with the dynamic.Configuration
// containing the newly generated (or renewed) Tailscale certs.
func (p *Provider) sendDynamicConfig() {
p.certByDomainMu.RLock()
defer p.certByDomainMu.RUnlock()
// TODO: we always send back to traefik core the set of certificates
// sorted, to make sure that two identical sets, that would be sorted
// differently, do not trigger another configuration update because of the
// mismatch. But in reality we should not end up sending a certificates
// update if there was no new certs to generate or renew in the first
// place, so this scenario should never happen, and the sorting might
// actually not be needed.
var sortedDomains []string
for domain := range p.certByDomain {
sortedDomains = append(sortedDomains, domain)
}
sort.Strings(sortedDomains)
var certs []*traefiktls.CertAndStores
for _, domain := range sortedDomains {
// Only the default store is supported.
certs = append(certs, &traefiktls.CertAndStores{
Stores: []string{traefiktls.DefaultTLSStoreName},
Certificate: p.certByDomain[domain],
})
}
p.dynMessages <- dynamic.Message{
ProviderName: p.ResolverName + ".tailscale",
Configuration: &dynamic.Configuration{
TLS: &dynamic.TLSConfiguration{Certificates: certs},
},
}
}
// sanitizeDomains removes duplicated and invalid Tailscale subdomains, from
// the provided list.
func sanitizeDomains(ctx context.Context, domains []string) []string {
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logger := log.Ctx(ctx)
seen := map[string]struct{}{}
var sanitizedDomains []string
for _, domain := range domains {
if _, ok := seen[domain]; ok {
continue
}
if !isTailscaleDomain(domain) {
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logger.Error().Msgf("Domain %s is not a valid Tailscale domain", domain)
continue
}
sanitizedDomains = append(sanitizedDomains, domain)
seen[domain] = struct{}{}
}
return sanitizedDomains
}
// isTailscaleDomain returns whether the given domain is a valid Tailscale
// domain. A valid Tailscale domain has the following form:
// machine-name.domains-alias.ts.net.
func isTailscaleDomain(domain string) bool {
// TODO: extra check, against the actual list of allowed domains names,
// provided by the Tailscale daemon status?
labels := strings.Split(domain, ".")
return len(labels) == 4 && labels[2] == "ts" && labels[3] == "net"
}
// isValidCert returns whether the given tls.Certificate is valid for the given
// domain at the given time.
func isValidCert(cert tls.Certificate, domain string, now time.Time) bool {
var leaf *x509.Certificate
intermediates := x509.NewCertPool()
for i, raw := range cert.Certificate {
der, err := x509.ParseCertificate(raw)
if err != nil {
return false
}
if i == 0 {
leaf = der
continue
}
intermediates.AddCert(der)
}
if leaf == nil {
return false
}
_, err := leaf.Verify(x509.VerifyOptions{
DNSName: domain,
Intermediates: intermediates,
CurrentTime: now,
})
return err == nil
}