Add SFTP Server Support (#6753)

* Add SFTP Server Support

Signed-off-by: Mohamed Sekour <mohamed.sekour@exfo.com>

* fix s3 tests and helm lint

Signed-off-by: Mohamed Sekour <mohamed.sekour@exfo.com>

* increase  helm chart version

* adjust version

---------

Signed-off-by: Mohamed Sekour <mohamed.sekour@exfo.com>
Co-authored-by: chrislu <chris.lu@gmail.com>

weed/sftpd/auth/auth.go

@@ -0,0 +1,76 @@
+// Package auth provides authentication and authorization functionality for the SFTP server
+package auth
+
+import (
+	"github.com/seaweedfs/seaweedfs/weed/sftpd/user"
+	"golang.org/x/crypto/ssh"
+)
+
+// Provider defines the interface for authentication providers
+type Provider interface {
+	// GetAuthMethods returns the SSH server auth methods
+	GetAuthMethods() []ssh.AuthMethod
+}
+
+// Manager handles authentication and authorization
+type Manager struct {
+	userStore          user.Store
+	passwordAuth       *PasswordAuthenticator
+	publicKeyAuth      *PublicKeyAuthenticator
+	permissionChecker  *PermissionChecker
+	enabledAuthMethods []string
+}
+
+// NewManager creates a new authentication manager
+func NewManager(userStore user.Store, fsHelper FileSystemHelper, enabledAuthMethods []string) *Manager {
+	manager := &Manager{
+		userStore:          userStore,
+		enabledAuthMethods: enabledAuthMethods,
+	}
+
+	// Initialize authenticators based on enabled methods
+	passwordEnabled := false
+	publicKeyEnabled := false
+
+	for _, method := range enabledAuthMethods {
+		switch method {
+		case "password":
+			passwordEnabled = true
+		case "publickey":
+			publicKeyEnabled = true
+		}
+	}
+
+	manager.passwordAuth = NewPasswordAuthenticator(userStore, passwordEnabled)
+	manager.publicKeyAuth = NewPublicKeyAuthenticator(userStore, publicKeyEnabled)
+	manager.permissionChecker = NewPermissionChecker(fsHelper)
+
+	return manager
+}
+
+// GetSSHServerConfig returns an SSH server config with the appropriate authentication methods
+func (m *Manager) GetSSHServerConfig() *ssh.ServerConfig {
+	config := &ssh.ServerConfig{}
+
+	// Add password authentication if enabled
+	if m.passwordAuth.Enabled() {
+		config.PasswordCallback = m.passwordAuth.Authenticate
+	}
+
+	// Add public key authentication if enabled
+	if m.publicKeyAuth.Enabled() {
+		config.PublicKeyCallback = m.publicKeyAuth.Authenticate
+	}
+
+	return config
+}
+
+// CheckPermission checks if a user has the required permission on a path
+func (m *Manager) CheckPermission(user *user.User, path, permission string) error {
+	return m.permissionChecker.CheckFilePermission(user, path, permission)
+}
+
+// GetUser retrieves a user from the user store
+func (m *Manager) GetUser(username string) (*user.User, error) {
+	return m.userStore.GetUser(username)
+}