first commit

2026-08-09 18:03:09 +01:00
commit d7ca591b76
169 changed files with 51272 additions and 0 deletions
@@ -0,0 +1,227 @@
+package tlsutil
+
+import (
+	"context"
+	"crypto/tls"
+	"crypto/x509"
+	"fmt"
+	"log/slog"
+	"sync"
+	"time"
+
+	"gomail/internal/acme"
+	"gomail/internal/crypto"
+	"gomail/internal/db"
+)
+
+// renewalMargin is how far before expiry a certificate is renewed.
+const renewalMargin = 30 * 24 * time.Hour
+
+// ACMEManager obtains and caches ACME certificates per domain, encrypted at
+// rest (same HKDF-per-record scheme as everything else), and serves them
+// via a SNI-aware tls.Config.GetCertificate callback so a single listener
+// can present the right certificate for whichever domain a client connects
+// to. A background loop renews any certificate within renewalMargin of
+// expiry.
+type ACMEManager struct {
+	database     *db.DB
+	mk           *crypto.MasterKey
+	directoryURL string
+	contactEmail string
+	responder    *acme.ChallengeResponder
+
+	mu    sync.RWMutex
+	cache map[string]*tls.Certificate
+}
+
+func NewACMEManager(database *db.DB, mk *crypto.MasterKey, directoryURL, contactEmail string, responder *acme.ChallengeResponder) *ACMEManager {
+	return &ACMEManager{
+		database: database, mk: mk, directoryURL: directoryURL, contactEmail: contactEmail,
+		responder: responder, cache: make(map[string]*tls.Certificate),
+	}
+}
+
+// TLSConfig returns a tls.Config whose GetCertificate looks up the right
+// cert per SNI, obtaining one on first use if none is cached yet.
+func (m *ACMEManager) TLSConfig() *tls.Config {
+	return &tls.Config{
+		MinVersion: tls.VersionTLS12,
+		GetCertificate: func(hello *tls.ClientHelloInfo) (*tls.Certificate, error) {
+			return m.CertificateFor(hello.ServerName)
+		},
+	}
+}
+
+// CertificateFor returns a cached certificate for domain, obtaining one via
+// ACME (and caching it, in memory and encrypted in the DB) if not already
+// cached or if the cached one is expired/near expiry.
+func (m *ACMEManager) CertificateFor(domain string) (*tls.Certificate, error) {
+	m.mu.RLock()
+	cached, ok := m.cache[domain]
+	m.mu.RUnlock()
+	if ok {
+		return cached, nil
+	}
+
+	if stored, err := m.loadFromDB(domain); err == nil {
+		m.mu.Lock()
+		m.cache[domain] = stored
+		m.mu.Unlock()
+		return stored, nil
+	}
+
+	cert, err := m.obtainAndStore(domain)
+	if err != nil {
+		return nil, err
+	}
+	return cert, nil
+}
+
+func (m *ACMEManager) loadFromDB(domain string) (*tls.Certificate, error) {
+	row, err := m.database.GetTLSCert(domain)
+	if err != nil {
+		return nil, err
+	}
+	if row.CertPEMEnc == nil || row.KeyPEMEnc == nil {
+		return nil, fmt.Errorf("no cert material stored for %s", domain)
+	}
+	if row.ExpiresAt != nil && time.Now().UTC().After(row.ExpiresAt.Add(-renewalMargin)) {
+		return nil, fmt.Errorf("stored cert for %s is expired or near expiry", domain)
+	}
+
+	certPEM, err := crypto.Decrypt(m.mk, row.ID, "tls-cert", row.CertPEMEnc)
+	if err != nil {
+		return nil, fmt.Errorf("decrypting cert: %w", err)
+	}
+	keyPEM, err := crypto.Decrypt(m.mk, row.ID, "tls-key", row.KeyPEMEnc)
+	if err != nil {
+		return nil, fmt.Errorf("decrypting key: %w", err)
+	}
+
+	cert, err := tls.X509KeyPair(certPEM, keyPEM)
+	if err != nil {
+		return nil, fmt.Errorf("parsing stored cert/key: %w", err)
+	}
+	return &cert, nil
+}
+
+func (m *ACMEManager) obtainAndStore(domain string) (*tls.Certificate, error) {
+	accountKey, err := m.loadOrCreateAccountKey(domain)
+	if err != nil {
+		return nil, fmt.Errorf("account key: %w", err)
+	}
+
+	slog.Info("obtaining ACME certificate", "domain", domain, "directory", m.directoryURL)
+	certPEM, keyPEM, err := acme.Obtain(m.directoryURL, m.contactEmail, []string{domain}, accountKey, m.responder)
+	if err != nil {
+		return nil, fmt.Errorf("ACME obtain for %s: %w", domain, err)
+	}
+
+	cert, err := tls.X509KeyPair(certPEM, keyPEM)
+	if err != nil {
+		return nil, fmt.Errorf("parsing obtained cert/key: %w", err)
+	}
+
+	var expiresAt *time.Time
+	if len(cert.Certificate) > 0 {
+		if leaf, err := x509.ParseCertificate(cert.Certificate[0]); err == nil {
+			expiresAt = &leaf.NotAfter
+		}
+	}
+
+	existing, _ := m.database.GetTLSCert(domain)
+	recordID := domain
+	if existing != nil {
+		recordID = existing.ID
+	}
+	encCert, err := crypto.Encrypt(m.mk, recordID, "tls-cert", certPEM)
+	if err != nil {
+		return nil, fmt.Errorf("encrypting cert: %w", err)
+	}
+	encKey, err := crypto.Encrypt(m.mk, recordID, "tls-key", keyPEM)
+	if err != nil {
+		return nil, fmt.Errorf("encrypting key: %w", err)
+	}
+
+	if err := m.database.UpsertTLSCert(&db.TLSCert{
+		ID: recordID, Domain: domain, CertPEMEnc: encCert, KeyPEMEnc: encKey, ExpiresAt: expiresAt,
+	}); err != nil {
+		return nil, fmt.Errorf("storing cert: %w", err)
+	}
+
+	m.mu.Lock()
+	m.cache[domain] = &cert
+	m.mu.Unlock()
+
+	slog.Info("ACME certificate obtained and stored", "domain", domain, "expires_at", expiresAt)
+	return &cert, nil
+}
+
+func (m *ACMEManager) loadOrCreateAccountKey(domain string) (*acme.AccountKey, error) {
+	row, err := m.database.GetTLSCert(domain)
+	if err == nil && row.ACMEAccountKeyEnc != nil {
+		plain, decErr := crypto.Decrypt(m.mk, row.ID, "acme-account-key", row.ACMEAccountKeyEnc)
+		if decErr == nil {
+			if key, parseErr := acme.ParseAccountKeyPEM(plain); parseErr == nil {
+				return key, nil
+			}
+		}
+	}
+
+	key, err := acme.GenerateAccountKey()
+	if err != nil {
+		return nil, err
+	}
+	keyPEM, err := key.MarshalPEM()
+	if err != nil {
+		return nil, err
+	}
+
+	recordID := domain
+	if row != nil {
+		recordID = row.ID
+	}
+	encKey, err := crypto.Encrypt(m.mk, recordID, "acme-account-key", keyPEM)
+	if err != nil {
+		return nil, err
+	}
+	if err := m.database.SetACMEAccountKey(domain, encKey); err != nil {
+		return nil, err
+	}
+	return key, nil
+}
+
+// StartRenewalLoop runs a background check (default: daily) and renews any
+// domain whose cached/stored certificate is within renewalMargin of expiry.
+// domains is the full set this instance is responsible for — typically all
+// active hosted domains plus the server's own hostname.
+func (m *ACMEManager) StartRenewalLoop(ctx context.Context, domains []string, checkInterval time.Duration) {
+	ticker := time.NewTicker(checkInterval)
+	defer ticker.Stop()
+
+	checkAndRenew := func() {
+		for _, domain := range domains {
+			row, err := m.database.GetTLSCert(domain)
+			needsRenewal := err != nil || row.ExpiresAt == nil || time.Now().UTC().After(row.ExpiresAt.Add(-renewalMargin))
+			if !needsRenewal {
+				continue
+			}
+			slog.Info("renewing ACME certificate", "domain", domain)
+			m.mu.Lock()
+			delete(m.cache, domain) // force re-obtain, not a stale in-memory hit
+			m.mu.Unlock()
+			if _, err := m.obtainAndStore(domain); err != nil {
+				slog.Error("ACME renewal failed", "domain", domain, "err", err)
+			}
+		}
+	}
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-ticker.C:
+			checkAndRenew()
+		}
+	}
+}