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/sftp_userstore.go

@@ -0,0 +1,143 @@
+package sftpd
+
+import (
+	"crypto/subtle"
+	"encoding/json"
+	"fmt"
+	"os"
+	"strings"
+	"sync"
+)
+
+// UserStore interface for user management.
+type UserStore interface {
+	GetUser(username string) (*User, error)
+	ValidatePassword(username string, password []byte) bool
+	ValidatePublicKey(username string, keyData string) bool
+	GetUserPermissions(username string, path string) []string
+}
+
+// User represents an SFTP user with authentication and permission details.
+type User struct {
+	Username    string
+	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
+}
+
+// FileUserStore implements UserStore using a JSON file.
+type FileUserStore struct {
+	filePath string
+	users    map[string]*User
+	mu       sync.RWMutex
+}
+
+// NewFileUserStore creates a new user store from a JSON file.
+func NewFileUserStore(filePath string) (*FileUserStore, error) {
+	store := &FileUserStore{
+		filePath: filePath,
+		users:    make(map[string]*User),
+	}
+
+	if err := store.loadUsers(); err != nil {
+		return nil, err
+	}
+
+	return store, nil
+}
+
+// loadUsers loads users from the JSON file.
+func (s *FileUserStore) loadUsers() error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	// Check if file exists
+	if _, err := os.Stat(s.filePath); os.IsNotExist(err) {
+		return fmt.Errorf("user store file not found: %s", s.filePath)
+	}
+
+	data, err := os.ReadFile(s.filePath)
+	if err != nil {
+		return fmt.Errorf("failed to read user store file: %v", err)
+	}
+
+	var users []*User
+	if err := json.Unmarshal(data, &users); err != nil {
+		return fmt.Errorf("failed to parse user store file: %v", err)
+	}
+
+	for _, user := range users {
+		s.users[user.Username] = user
+	}
+
+	return nil
+}
+
+// GetUser returns a user by username.
+func (s *FileUserStore) GetUser(username string) (*User, error) {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	user, ok := s.users[username]
+	if !ok {
+		return nil, fmt.Errorf("user not found: %s", username)
+	}
+
+	return user, nil
+}
+
+// ValidatePassword checks if the password is valid for the user.
+func (s *FileUserStore) ValidatePassword(username string, password []byte) bool {
+	user, err := s.GetUser(username)
+	if err != nil {
+		return false
+	}
+
+	// Compare plaintext password using constant time comparison for security
+	return subtle.ConstantTimeCompare([]byte(user.Password), password) == 1
+}
+
+// ValidatePublicKey checks if the public key is valid for the user.
+func (s *FileUserStore) ValidatePublicKey(username string, keyData string) bool {
+	user, err := s.GetUser(username)
+	if err != nil {
+		return false
+	}
+
+	for _, key := range user.PublicKeys {
+		if subtle.ConstantTimeCompare([]byte(key), []byte(keyData)) == 1 {
+			return true
+		}
+	}
+
+	return false
+}
+
+// GetUserPermissions returns the permissions for a user on a path.
+func (s *FileUserStore) GetUserPermissions(username string, path string) []string {
+	user, err := s.GetUser(username)
+	if err != nil {
+		return nil
+	}
+
+	// Check exact path match first
+	if perms, ok := user.Permissions[path]; ok {
+		return perms
+	}
+
+	// Check parent directories
+	var bestMatch string
+	var bestPerms []string
+
+	for p, perms := range user.Permissions {
+		if strings.HasPrefix(path, p) && len(p) > len(bestMatch) {
+			bestMatch = p
+			bestPerms = perms
+		}
+	}
+
+	return bestPerms
+}