TO DO:kari/taildropsaf

-check if Context.getExternalFilesDirs works as is for private dir

1 files changed, 147 insertions, 0 deletions

diff --git a/cmd/containerboot/certs.go b/cmd/containerboot/certs.go
new file mode 100644
index 000000000..7af0424a9
--- /dev/null
+++ b/cmd/containerboot/certs.go
@@ -0,0 +1,147 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build linux
+
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"net"
+	"sync"
+	"time"
+
+	"tailscale.com/ipn"
+	"tailscale.com/util/goroutines"
+	"tailscale.com/util/mak"
+)
+
+// certManager is responsible for issuing certificates for known domains and for
+// maintaining a loop that re-attempts issuance daily.
+// Currently cert manager logic is only run on ingress ProxyGroup replicas that are responsible for managing certs for
+// HA Ingress HTTPS endpoints ('write' replicas).
+type certManager struct {
+	lc      localClient
+	tracker goroutines.Tracker // tracks running goroutines
+	mu      sync.Mutex         // guards the following
+	// certLoops contains a map of DNS names, for which we currently need to
+	// manage certs to cancel functions that allow stopping a goroutine when
+	// we no longer need to manage certs for the DNS name.
+	certLoops map[string]context.CancelFunc
+}
+
+// ensureCertLoops ensures that, for all currently managed Service HTTPS
+// endpoints, there is a cert loop responsible for issuing and ensuring the
+// renewal of the TLS certs.
+// ServeConfig must not be nil.
+func (cm *certManager) ensureCertLoops(ctx context.Context, sc *ipn.ServeConfig) error {
+	if sc == nil {
+		return fmt.Errorf("[unexpected] ensureCertLoops called with nil ServeConfig")
+	}
+	currentDomains := make(map[string]bool)
+	const httpsPort = "443"
+	for _, service := range sc.Services {
+		for hostPort := range service.Web {
+			domain, port, err := net.SplitHostPort(string(hostPort))
+			if err != nil {
+				return fmt.Errorf("[unexpected] unable to parse HostPort %s", hostPort)
+			}
+			if port != httpsPort { // HA Ingress' HTTP endpoint
+				continue
+			}
+			currentDomains[domain] = true
+		}
+	}
+	cm.mu.Lock()
+	defer cm.mu.Unlock()
+	for domain := range currentDomains {
+		if _, exists := cm.certLoops[domain]; !exists {
+			cancelCtx, cancel := context.WithCancel(ctx)
+			mak.Set(&cm.certLoops, domain, cancel)
+			cm.tracker.Go(func() { cm.runCertLoop(cancelCtx, domain) })
+		}
+	}
+
+	// Stop goroutines for domain names that are no longer in the config.
+	for domain, cancel := range cm.certLoops {
+		if !currentDomains[domain] {
+			cancel()
+			delete(cm.certLoops, domain)
+		}
+	}
+	return nil
+}
+
+// runCertLoop:
+// - calls localAPI certificate endpoint to ensure that certs are issued for the
+// given domain name
+// - calls localAPI certificate endpoint daily to ensure that certs are renewed
+// - if certificate issuance failed retries after an exponential backoff period
+// starting at 1 minute and capped at 24 hours. Reset the backoff once issuance succeeds.
+// Note that renewal check also happens when the node receives an HTTPS request and it is possible that certs get
+// renewed at that point. Renewal here is needed to prevent the shared certs from expiry in edge cases where the 'write'
+// replica does not get any HTTPS requests.
+// https://letsencrypt.org/docs/integration-guide/#retrying-failures
+func (cm *certManager) runCertLoop(ctx context.Context, domain string) {
+	const (
+		normalInterval   = 24 * time.Hour  // regular renewal check
+		initialRetry     = 1 * time.Minute // initial backoff after a failure
+		maxRetryInterval = 24 * time.Hour  // max backoff period
+	)
+	timer := time.NewTimer(0) // fire off timer immediately
+	defer timer.Stop()
+	retryCount := 0
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-timer.C:
+			// We call the certificate endpoint, but don't do anything
+			// with the returned certs here.
+			// The call to the certificate endpoint will ensure that
+			// certs are issued/renewed as needed and stored in the
+			// relevant state store. For example, for HA Ingress
+			// 'write' replica, the cert and key will be stored in a
+			// Kubernetes Secret named after the domain for which we
+			// are issuing.
+			// Note that renewals triggered by the call to the
+			// certificates endpoint here and by renewal check
+			// triggered during a call to node's HTTPS endpoint
+			// share the same state/renewal lock mechanism, so we
+			// should not run into redundant issuances during
+			// concurrent renewal checks.
+			// TODO(irbekrm): maybe it is worth adding a new
+			// issuance endpoint that explicitly only triggers
+			// issuance and stores certs in the relevant store, but
+			// does not return certs to the caller?
+			_, _, err := cm.lc.CertPair(ctx, domain)
+			if err != nil {
+				log.Printf("error refreshing certificate for %s: %v", domain, err)
+			}
+			var nextInterval time.Duration
+			// TODO(irbekrm): distinguish between LE rate limit
+			// errors and other error types like transient network
+			// errors.
+			if err == nil {
+				retryCount = 0
+				nextInterval = normalInterval
+			} else {
+				retryCount++
+				// Calculate backoff: initialRetry * 2^(retryCount-1)
+				// For retryCount=1: 1min * 2^0 = 1min
+				// For retryCount=2: 1min * 2^1 = 2min
+				// For retryCount=3: 1min * 2^2 = 4min
+				backoff := initialRetry * time.Duration(1<<(retryCount-1))
+				if backoff > maxRetryInterval {
+					backoff = maxRetryInterval
+				}
+				nextInterval = backoff
+				log.Printf("Error refreshing certificate for %s (retry %d): %v. Will retry in %v\n",
+					domain, retryCount, err, nextInterval)
+			}
+			timer.Reset(nextInterval)
+		}
+	}
+}