0.27.0 — Infisical hardening: runtime refresh, audit logging, CLI verify/audit, startup verification, SSH host key verification, interface consolidation

internal/actuator/hostkeys.go

@@ -0,0 +1,129 @@
+package actuator
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"log/slog"
+	"net"
+	"sync"
+	"time"
+
+	"golang.org/x/crypto/ssh"
+)
+
+var (
+	hostKeyMu    sync.RWMutex
+	hostKeyCache map[string]ssh.PublicKey
+	hostKeyOnce sync.Once
+	hostKeySrc   HostKeySource
+)
+
+// HostKeySource provides storage for SSH host public keys.
+type HostKeySource interface {
+	GetHostKey(ctx context.Context, hostname string) (string, error)
+	SetHostKey(ctx context.Context, hostname string, key string) error
+}
+
+// SetHostKeySource sets the host key source. Must be called before
+// any SSH connections. A nil source enables TOFU-only mode (keys
+// accepted in memory but not persisted).
+func SetHostKeySource(src HostKeySource) {
+	hostKeyMu.Lock()
+	defer hostKeyMu.Unlock()
+	hostKeySrc = src
+}
+
+// HostKeyCallback returns an ssh.HostKeyCallback that verifies host keys.
+// Known keys are verified (MITM detection). Unknown keys are accepted
+// via TOFU and optionally persisted to the source.
+func HostKeyCallback() ssh.HostKeyCallback {
+	return hostKeyVerify
+}
+
+func hostKeyVerify(hostname string, remote net.Addr, key ssh.PublicKey) error {
+	hostKeyOnce.Do(func() {
+		hostKeyCache = make(map[string]ssh.PublicKey)
+	})
+
+	normalized := hostWithoutPort(hostname)
+
+	hostKeyMu.RLock()
+	known, exists := hostKeyCache[normalized]
+	hostKeyMu.RUnlock()
+
+	if exists {
+		if bytes.Equal(key.Marshal(), known.Marshal()) {
+			return nil
+		}
+		return fmt.Errorf("SSH HOST KEY CHANGED for %s (possible MITM)", normalized)
+	}
+
+	hostKeyMu.Lock()
+	hostKeyCache[normalized] = key
+	hostKeyMu.Unlock()
+
+	slog.Info("ssh: accepting new host key (TOFU)", "host", normalized)
+
+	if hostKeySrc != nil {
+		go persistHostKey(normalized, key)
+	}
+
+	return nil
+}
+
+func persistHostKey(hostname string, key ssh.PublicKey) {
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	keyBase64 := key.Type() + " " + string(key.Marshal())
+	if err := hostKeySrc.SetHostKey(ctx, "ssh/host-keys/"+hostname, keyBase64); err != nil {
+		slog.Warn("ssh: failed to persist host key", "host", hostname, "error", err)
+	}
+}
+
+// LoadHostKeys pre-loads known host keys from the source into the
+// in-memory cache. Call at startup to avoid TOFU on first connection.
+// The source should return key lines in the format "key-type base64-data".
+func LoadHostKeys(ctx context.Context, hostnames []string, src HostKeySource) {
+	if src == nil {
+		return
+	}
+	SetHostKeySource(src)
+
+	hostKeyMu.Lock()
+	defer hostKeyMu.Unlock()
+
+	if hostKeyCache == nil {
+		hostKeyCache = make(map[string]ssh.PublicKey)
+	}
+
+	loaded := 0
+	for _, hostname := range hostnames {
+		keyData, err := src.GetHostKey(ctx, "ssh/host-keys/"+hostname)
+		if err != nil {
+			slog.Debug("ssh: no stored key for host", "host", hostname, "error", err)
+			continue
+		}
+		pubKey, _, _, _, err := ssh.ParseAuthorizedKey([]byte(keyData))
+		if err != nil {
+			slog.Warn("ssh: invalid stored key for host", "host", hostname, "error", err)
+			continue
+		}
+		hostKeyCache[hostname] = pubKey
+		loaded++
+	}
+
+	if loaded > 0 {
+		slog.Info("ssh: loaded host keys from Infisical", "count", loaded)
+	}
+}
+
+func hostWithoutPort(hostname string) string {
+	for i := len(hostname) - 1; i >= 0; i-- {
+		if hostname[i] == ':' {
+			return hostname[:i]
+		}
+	}
+	return hostname
+}