fix: auto-renew TLS certificates without restart #1337
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,115 @@ | ||
| package acme | ||
|
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| import ( | ||
| "context" | ||
| "crypto/tls" | ||
| "os" | ||
| "sync" | ||
| "sync/atomic" | ||
| "time" | ||
|
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| "github.com/projectdiscovery/gologger" | ||
| ) | ||
|
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| const defaultCertCheckInterval = 1 * time.Hour | ||
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| 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 | ||
| } | ||
|
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| // 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] | ||
| modTime time.Time | ||
| mu sync.Mutex // protects reload; reads are lock-free via atomic | ||
| } | ||
|
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| // 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 | ||
| } | ||
|
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| modTime, _ := latestModTime(certPath, keyPath) | ||
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| r := &CertReloader{ | ||
| certPath: certPath, | ||
| keyPath: keyPath, | ||
| modTime: modTime, | ||
| } | ||
| r.cert.Store(&cert) | ||
| return r, nil | ||
| } | ||
|
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| // GetCertificate returns the current certificate. Safe for concurrent use. | ||
| func (r *CertReloader) GetCertificate(_ *tls.ClientHelloInfo) (*tls.Certificate, error) { | ||
| return r.cert.Load(), nil | ||
| } | ||
|
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| // 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() | ||
| } | ||
| } | ||
| } | ||
|
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| func (r *CertReloader) tryReload() { | ||
| r.mu.Lock() | ||
|
Member
There was a problem hiding this comment. Isn't the |
||
| defer r.mu.Unlock() | ||
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| 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.After(r.modTime) { | ||
| return | ||
| } | ||
|
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| cert, err := tls.LoadX509KeyPair(r.certPath, r.keyPath) | ||
| if err != nil { | ||
| gologger.Warning().Msgf("Could not reload certificate: %s", err) | ||
| return | ||
| } | ||
|
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| r.cert.Store(&cert) | ||
| r.modTime = mt | ||
| gologger.Info().Msgf("Reloaded TLS certificate from %s", r.certPath) | ||
| } | ||
|
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| // 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 | ||
| } | ||
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🟡 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