♻️ refactor: split src into internal packages and cmd

internal/sshserver/hostkeys.go

@@ -0,0 +1,61 @@
+package sshserver
+
+import (
+	"crypto/ed25519"
+	"crypto/rand"
+	"crypto/rsa"
+	"encoding/pem"
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"golang.org/x/crypto/ssh"
+)
+
+func generateAndSave(keyPath, keyType string) error {
+	fmt.Printf("Generating %s host key...\n", keyType)
+
+	var key any
+	var err error
+	if keyType == "rsa" {
+		key, err = rsa.GenerateKey(rand.Reader, 4096)
+	} else {
+		_, key, err = ed25519.GenerateKey(rand.Reader)
+	}
+	if err != nil {
+		return err
+	}
+
+	block, err := ssh.MarshalPrivateKey(key, "")
+	if err != nil {
+		return err
+	}
+	return os.WriteFile(keyPath, pem.EncodeToMemory(block), 0o600)
+}
+
+func EnsureHostKeys(configDir string) ([]ssh.Signer, error) {
+	keys := []struct{ file, keyType string }{
+		{"id_rsa", "rsa"},
+		{"id_ed25519", "ed25519"},
+	}
+
+	signers := make([]ssh.Signer, 0, len(keys))
+	for _, k := range keys {
+		keyPath := filepath.Join(configDir, k.file)
+		if _, err := os.Stat(keyPath); os.IsNotExist(err) {
+			if err := generateAndSave(keyPath, k.keyType); err != nil {
+				return nil, fmt.Errorf("failed to generate %s host key: %w", k.keyType, err)
+			}
+		}
+		raw, err := os.ReadFile(keyPath)
+		if err != nil {
+			return nil, err
+		}
+		signer, err := ssh.ParsePrivateKey(raw)
+		if err != nil {
+			return nil, fmt.Errorf("failed to parse host key %q: %w", keyPath, err)
+		}
+		signers = append(signers, signer)
+	}
+	return signers, nil
+}