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/user/user.go

@@ -0,0 +1,111 @@
+// Package user provides user management functionality for the SFTP server
+package user
+
+import (
+	"fmt"
+	"math/rand"
+	"path/filepath"
+)
+
+// User represents an SFTP user with authentication and permission details
+type User struct {
+	Username    string              // Username for authentication
+	Password    string              // Plaintext password
+	PublicKeys  []string            // Authorized public keys
+	HomeDir     string              // User's home directory
+	Permissions map[string][]string // path -> permissions (read, write, list, etc.)
+	Uid         uint32              // User ID for file ownership
+	Gid         uint32              // Group ID for file ownership
+}
+
+// Store defines the interface for user storage and retrieval
+type Store interface {
+	// GetUser retrieves a user by username
+	GetUser(username string) (*User, error)
+
+	// ValidatePassword checks if the password is valid for the user
+	ValidatePassword(username string, password []byte) bool
+
+	// ValidatePublicKey checks if the public key is valid for the user
+	ValidatePublicKey(username string, keyData string) bool
+
+	// GetUserPermissions returns the permissions for a user on a path
+	GetUserPermissions(username string, path string) []string
+
+	// SaveUser saves or updates a user
+	SaveUser(user *User) error
+
+	// DeleteUser removes a user
+	DeleteUser(username string) error
+
+	// ListUsers returns all usernames
+	ListUsers() ([]string, error)
+}
+
+// UserNotFoundError is returned when a user is not found
+type UserNotFoundError struct {
+	Username string
+}
+
+func (e *UserNotFoundError) Error() string {
+	return fmt.Sprintf("user not found: %s", e.Username)
+}
+
+// NewUser creates a new user with default settings
+func NewUser(username string) *User {
+	// Generate a random UID/GID between 1000 and 60000
+	// This range is typically safe for regular users in most systems
+	// 0-999 are often reserved for system users
+	randomId := 1000 + rand.Intn(59000)
+
+	return &User{
+		Username:    username,
+		Permissions: make(map[string][]string),
+		HomeDir:     filepath.Join("/home", username),
+		Uid:         uint32(randomId),
+		Gid:         uint32(randomId),
+	}
+}
+
+// SetPassword sets a plaintext password for the user
+func (u *User) SetPassword(password string) {
+	u.Password = password
+}
+
+// AddPublicKey adds a public key to the user
+func (u *User) AddPublicKey(key string) {
+	// Check if key already exists
+	for _, existingKey := range u.PublicKeys {
+		if existingKey == key {
+			return
+		}
+	}
+	u.PublicKeys = append(u.PublicKeys, key)
+}
+
+// RemovePublicKey removes a public key from the user
+func (u *User) RemovePublicKey(key string) bool {
+	for i, existingKey := range u.PublicKeys {
+		if existingKey == key {
+			// Remove the key by replacing it with the last element and truncating
+			u.PublicKeys[i] = u.PublicKeys[len(u.PublicKeys)-1]
+			u.PublicKeys = u.PublicKeys[:len(u.PublicKeys)-1]
+			return true
+		}
+	}
+	return false
+}
+
+// SetPermission sets permissions for a specific path
+func (u *User) SetPermission(path string, permissions []string) {
+	u.Permissions[path] = permissions
+}
+
+// RemovePermission removes permissions for a specific path
+func (u *User) RemovePermission(path string) bool {
+	if _, exists := u.Permissions[path]; exists {
+		delete(u.Permissions, path)
+		return true
+	}
+	return false
+}