fix: auto-renew TLS certificates without restart #1337
+471
−55
There are no files selected for viewing
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,110 @@ | ||
| package acme | ||
|
|
||
| import ( | ||
| "context" | ||
| "crypto/tls" | ||
| "os" | ||
| "sync/atomic" | ||
| "time" | ||
|
|
||
| "github.com/projectdiscovery/gologger" | ||
| ) | ||
|
|
||
| const defaultCertCheckInterval = 1 * time.Hour | ||
|
|
||
| func certCheckInterval() time.Duration { | ||
| if v := os.Getenv("CERT_CHECK_INTERVAL"); v != "" { | ||
| if d, err := time.ParseDuration(v); err == nil && d > 0 { | ||
| return d | ||
| } | ||
| gologger.Warning().Msgf("Invalid CERT_CHECK_INTERVAL %q, using default %s", v, defaultCertCheckInterval) | ||
| } | ||
| return defaultCertCheckInterval | ||
| } | ||
|
|
||
| // CertReloader watches a certificate/key file pair and reloads when files change on disk. | ||
| type CertReloader struct { | ||
| certPath string | ||
| keyPath string | ||
| cert atomic.Pointer[tls.Certificate] | ||
| modTimeNs atomic.Int64 | ||
| } | ||
|
|
||
| // NewCertReloader loads the initial certificate and returns a reloader. | ||
| func NewCertReloader(certPath, keyPath string) (*CertReloader, error) { | ||
| cert, err := tls.LoadX509KeyPair(certPath, keyPath) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
|
||
| modTime, _ := latestModTime(certPath, keyPath) | ||
|
|
||
| r := &CertReloader{ | ||
| certPath: certPath, | ||
| keyPath: keyPath, | ||
| } | ||
| r.cert.Store(&cert) | ||
| r.modTimeNs.Store(modTime.UnixNano()) | ||
| return r, nil | ||
| } | ||
|
|
||
| // GetCertificate returns the current certificate. Safe for concurrent use. | ||
| func (r *CertReloader) GetCertificate(_ *tls.ClientHelloInfo) (*tls.Certificate, error) { | ||
| return r.cert.Load(), nil | ||
| } | ||
|
|
||
| // Start polls for certificate file changes and reloads when detected. | ||
| // Blocks until ctx is cancelled. | ||
| // The check interval is configurable via the CERT_CHECK_INTERVAL env variable (e.g. "30m", "2h"). | ||
| func (r *CertReloader) Start(ctx context.Context) { | ||
| interval := certCheckInterval() | ||
| gologger.Info().Msgf("Certificate reload check interval: %s", interval) | ||
| ticker := time.NewTicker(interval) | ||
| defer ticker.Stop() | ||
|
|
||
| for { | ||
| select { | ||
| case <-ctx.Done(): | ||
| return | ||
| case <-ticker.C: | ||
| r.tryReload() | ||
| } | ||
| } | ||
| } | ||
|
|
||
| func (r *CertReloader) tryReload() { | ||
| mt, err := latestModTime(r.certPath, r.keyPath) | ||
|
There was a problem hiding this comment. 🟠 TOCTOU vulnerability in certificate reload mechanism (CWE-367) — The tryReload() function has a time-of-check-time-of-use (TOCTOU) race condition. It checks file modification time at line 81, then loads the certificate at line 90. An attacker with filesystem access could replace the certificate files with symlinks between these operations, causing the server to load certificates from an attacker-controlled location. Attack ExampleSuggested Fix |
||
| if err != nil { | ||
| gologger.Warning().Msgf("Could not stat certificate files: %s", err) | ||
| return | ||
| } | ||
| if mt.UnixNano() <= r.modTimeNs.Load() { | ||
| return | ||
| } | ||
|
|
||
| cert, err := tls.LoadX509KeyPair(r.certPath, r.keyPath) | ||
| if err != nil { | ||
| gologger.Warning().Msgf("Could not reload certificate: %s", err) | ||
| return | ||
| } | ||
|
|
||
| r.cert.Store(&cert) | ||
| r.modTimeNs.Store(mt.UnixNano()) | ||
| gologger.Info().Msgf("Reloaded TLS certificate from %s", r.certPath) | ||
| } | ||
|
|
||
| // latestModTime returns the most recent modification time of the two files. | ||
| func latestModTime(certPath, keyPath string) (time.Time, error) { | ||
| certInfo, err := os.Stat(certPath) | ||
| if err != nil { | ||
| return time.Time{}, err | ||
| } | ||
| keyInfo, err := os.Stat(keyPath) | ||
| if err != nil { | ||
| return time.Time{}, err | ||
| } | ||
| if keyInfo.ModTime().After(certInfo.ModTime()) { | ||
| return keyInfo.ModTime(), nil | ||
| } | ||
| return certInfo.ModTime(), nil | ||
| } | ||
Oops, something went wrong.
Oops, something went wrong.
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
There was a problem hiding this comment.
Choose a reason for hiding this comment
The reason will be displayed to describe this comment to others. Learn more.
🟡 Missing TLS MinVersion allows downgrade to TLS 1.2 (CWE-327) — TLS configuration for custom certificates does not specify MinVersion, allowing clients to negotiate TLS 1.2. While Go 1.22+ defaults to TLS 1.2 minimum, explicitly setting TLS 1.3 provides defense-in-depth against future changes and protocol downgrade attacks.
Suggested Fix