feat: sftp server support (#7643)

* feat: sftp server support

* fix(sftp-server): try fix build failed

* fix: sftp download lack

internal/bootstrap/ssh.go

@@ -0,0 +1,101 @@
+package bootstrap
+
+import (
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/x509"
+	"encoding/pem"
+	"fmt"
+	"github.com/alist-org/alist/v3/cmd/flags"
+	"github.com/alist-org/alist/v3/internal/conf"
+	"github.com/alist-org/alist/v3/pkg/utils"
+	"golang.org/x/crypto/ssh"
+	"os"
+	"path/filepath"
+)
+
+func InitHostKey() {
+	sshPath := filepath.Join(flags.DataDir, "ssh")
+	if !utils.Exists(sshPath) {
+		err := utils.CreateNestedDirectory(sshPath)
+		if err != nil {
+			utils.Log.Fatalf("failed to create ssh directory: %+v", err)
+			return
+		}
+	}
+	conf.SSHSigners = make([]ssh.Signer, 0, 4)
+	if rsaKey, ok := LoadOrGenerateRSAHostKey(sshPath); ok {
+		conf.SSHSigners = append(conf.SSHSigners, rsaKey)
+	}
+	// TODO Add keys for other encryption algorithms
+}
+
+func LoadOrGenerateRSAHostKey(parentDir string) (ssh.Signer, bool) {
+	privateKeyPath := filepath.Join(parentDir, "ssh_host_rsa_key")
+	publicKeyPath := filepath.Join(parentDir, "ssh_host_rsa_key.pub")
+	privateKeyBytes, err := os.ReadFile(privateKeyPath)
+	if err == nil {
+		var privateKey *rsa.PrivateKey
+		privateKey, err = rsaDecodePrivateKey(privateKeyBytes)
+		if err == nil {
+			var ret ssh.Signer
+			ret, err = ssh.NewSignerFromKey(privateKey)
+			if err == nil {
+				return ret, true
+			}
+		}
+	}
+	_ = os.Remove(privateKeyPath)
+	_ = os.Remove(publicKeyPath)
+	privateKey, err := rsa.GenerateKey(rand.Reader, 4096)
+	if err != nil {
+		utils.Log.Fatalf("failed to generate RSA private key: %+v", err)
+		return nil, false
+	}
+	publicKey, err := ssh.NewPublicKey(&privateKey.PublicKey)
+	if err != nil {
+		utils.Log.Fatalf("failed to generate RSA public key: %+v", err)
+		return nil, false
+	}
+	ret, err := ssh.NewSignerFromKey(privateKey)
+	if err != nil {
+		utils.Log.Fatalf("failed to generate RSA signer: %+v", err)
+		return nil, false
+	}
+	privateBytes := rsaEncodePrivateKey(privateKey)
+	publicBytes := ssh.MarshalAuthorizedKey(publicKey)
+	err = os.WriteFile(privateKeyPath, privateBytes, 0600)
+	if err != nil {
+		utils.Log.Fatalf("failed to write RSA private key to file: %+v", err)
+		return nil, false
+	}
+	err = os.WriteFile(publicKeyPath, publicBytes, 0644)
+	if err != nil {
+		_ = os.Remove(privateKeyPath)
+		utils.Log.Fatalf("failed to write RSA public key to file: %+v", err)
+		return nil, false
+	}
+	return ret, true
+}
+
+func rsaEncodePrivateKey(privateKey *rsa.PrivateKey) []byte {
+	privateKeyBytes := x509.MarshalPKCS1PrivateKey(privateKey)
+	privateBlock := &pem.Block{
+		Type:    "RSA PRIVATE KEY",
+		Headers: nil,
+		Bytes:   privateKeyBytes,
+	}
+	return pem.EncodeToMemory(privateBlock)
+}
+
+func rsaDecodePrivateKey(bytes []byte) (*rsa.PrivateKey, error) {
+	block, _ := pem.Decode(bytes)
+	if block == nil {
+		return nil, fmt.Errorf("failed to parse PEM block containing the key")
+	}
+	privateKey, err := x509.ParsePKCS1PrivateKey(block.Bytes)
+	if err != nil {
+		return nil, err
+	}
+	return privateKey, nil
+}

internal/conf/config.go

@@ -84,6 +84,11 @@ type FTP struct {
 	EnablePasvConnIPCheck   bool   `json:"enable_pasv_conn_ip_check" env:"ENABLE_PASV_CONN_IP_CHECK"`
 }
 
+type SFTP struct {
+	Enable bool   `json:"enable" env:"ENABLE"`
+	Listen string `json:"listen" env:"LISTEN"`
+}
+
 type Config struct {
 	Force                 bool        `json:"force" env:"FORCE"`
 	SiteURL               string      `json:"site_url" env:"SITE_URL"`
@@ -104,6 +109,7 @@ type Config struct {
 	Cors                  Cors        `json:"cors" envPrefix:"CORS_"`
 	S3                    S3          `json:"s3" envPrefix:"S3_"`
 	FTP                   FTP         `json:"ftp" envPrefix:"FTP_"`
+	SFTP                  SFTP        `json:"sftp" envPrefix:"SFTP_"`
 }
 
 func DefaultConfig() *Config {
@@ -185,5 +191,9 @@ func DefaultConfig() *Config {
 			EnableActiveConnIPCheck: true,
 			EnablePasvConnIPCheck:   true,
 		},
+		SFTP: SFTP{
+			Enable: true,
+			Listen: ":5222",
+		},
 	}
 }

internal/conf/var.go

@@ -1,6 +1,7 @@
 package conf
 
 import (
+	"golang.org/x/crypto/ssh"
 	"net/url"
 	"regexp"
 )
@@ -32,3 +33,5 @@ var (
 	ManageHtml   string
 	IndexHtml    string
 )
+
+var SSHSigners []ssh.Signer