feat(ssh): auto generate additional ssh keys (#33974)

adds capabilities for gitea to generate ecdsa and ed25519 keys by
default
adds cli for built-in ssh key generation helpers


closes: https://github.com/go-gitea/gitea/issues/33783

---------

Co-authored-by: Nicolas <bircni@icloud.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: Giteabot <teabot@gitea.io>

cmd/generate.go

@@ -6,10 +6,12 @@ package cmd
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"os"
 
 	"gitea.dev/modules/generate"
+	"gitea.dev/modules/ssh"
 
 	"github.com/mattn/go-isatty"
 	"github.com/urfave/cli/v3"
@@ -21,6 +23,7 @@ func newGenerateCommand() *cli.Command {
 		Usage: "Generate Gitea's secrets/keys/tokens",
 		Commands: []*cli.Command{
 			newGenerateSecretCommand(),
+			newGenerateSSHCommand(),
 		},
 	}
 }
@@ -37,6 +40,17 @@ func newGenerateSecretCommand() *cli.Command {
 	}
 }
 
+func newGenerateSSHCommand() *cli.Command {
+	return &cli.Command{
+		Name:  "ssh",
+		Usage: "Generate ssh keys",
+		Commands: []*cli.Command{
+			newGenerateSSHKeyCommand(),
+			newGenerateSSHHostKeysCommand(),
+		},
+	}
+}
+
 func newGenerateInternalTokenCommand() *cli.Command {
 	return &cli.Command{
 		Name:   "INTERNAL_TOKEN",
@@ -62,6 +76,30 @@ func newGenerateSecretKeyCommand() *cli.Command {
 	}
 }
 
+func newGenerateSSHKeyCommand() *cli.Command {
+	return &cli.Command{
+		Name:  "key",
+		Usage: "Generate a new ssh key",
+		Flags: []cli.Flag{
+			&cli.IntFlag{Name: "bits", Aliases: []string{"b"}, Usage: "Number of bits in the key, ignored when key is ed25519"},
+			&cli.StringFlag{Name: "type", Aliases: []string{"t"}, Value: "ed25519", Usage: "Specifies the type of key to create."},
+			&cli.StringFlag{Name: "file", Aliases: []string{"f"}, Usage: "Specifies the path or base directory for the key file", Required: true},
+		},
+		Action: runGenerateKeyPair,
+	}
+}
+
+func newGenerateSSHHostKeysCommand() *cli.Command {
+	return &cli.Command{
+		Name:  "host-keys",
+		Usage: "Generate host keys of all default key types (rsa, ecdsa, and ed25519) if they do not already exist.",
+		Flags: []cli.Flag{
+			&cli.StringFlag{Name: "dir", Aliases: []string{"d"}, Usage: "Specifies the base directory for the key files", Required: true},
+		},
+		Action: runGenerateHostKey,
+	}
+}
+
 func runGenerateInternalToken(_ context.Context, c *cli.Command) error {
 	internalToken, err := generate.NewInternalToken()
 	if err != nil {
@@ -103,3 +141,41 @@ func runGenerateSecretKey(_ context.Context, c *cli.Command) error {
 
 	return nil
 }
+
+func runGenerateHostKey(_ context.Context, c *cli.Command) error {
+	file := c.String("dir")
+	info, err := os.Stat(file)
+	if errors.Is(err, os.ErrNotExist) {
+		if err = os.MkdirAll(file, 0o644); err != nil {
+			return err
+		}
+	} else if err != nil {
+		return err
+	} else if !info.IsDir() {
+		return errors.New("file already exists and is not a directory")
+	}
+	fmt.Fprintf(c.Writer, "Generating host keys in %s\n", file)
+	_, err = ssh.InitDefaultHostKeys(file)
+	return err
+}
+
+func runGenerateKeyPair(_ context.Context, c *cli.Command) error {
+	file := c.String("file")
+	keyType := c.String("type")
+
+	fmt.Fprintf(c.Writer, "Generating public/private %s key pair.\n", keyType)
+
+	// Check if file exists to prevent overwriting
+	if _, err := os.Stat(file); err == nil {
+		if !confirm(c.Reader, c.Writer, "%s already exists.\nOverwrite (y/n)? ", file) {
+			fmt.Println("Aborting")
+			return nil
+		}
+	}
+	bits := c.Int("bits")
+	err := ssh.GenKeyPair(file, generate.SSHKeyType(keyType), bits)
+	if err == nil {
+		fmt.Printf("Your SSH key has been saved in %s\n", file)
+	}
+	return err
+}