python based ftp server

third_party/pyftpdlib/demo/unix_ftpd.py

+#!/usr/bin/env python
+# unix_ftpd.py
+
+"""A ftpd using local unix account database to authenticate users
+(users must already exist).
+
+It also provides a mechanism to (temporarily) impersonate the system
+users every time they are going to perform filesystem operations.
+"""
+
+import os
+import pwd, spwd, crypt
+
+from pyftpdlib import ftpserver
+
+
+class UnixAuthorizer(ftpserver.DummyAuthorizer):
+
+    # the uid/gid the daemon runs under
+    PROCESS_UID = os.getuid()
+    PROCESS_GID = os.getgid()
+
+    def add_user(self, username, homedir=None, **kwargs):
+        """Add a "real" system user to the virtual users table.
+
+        If no home argument is specified the user's home directory will
+        be used.
+
+        The keyword arguments in kwargs are the same expected by the
+        original add_user method: "perm", "msg_login" and "msg_quit".
+        """
+        # get the list of all available users on the system and check
+        # if provided username exists
+        users = [entry.pw_name for entry in pwd.getpwall()]
+        if not username in users:
+            raise ftpserver.AuthorizerError('No such user "%s".' %username)
+        if not homedir:
+            homedir = pwd.getpwnam(username).pw_dir
+        ftpserver.DummyAuthorizer.add_user(self, username, '', homedir,**kwargs)
+
+    def add_anonymous(self, homedir=None, realuser="nobody", **kwargs):
+        """Add an anonymous user to the virtual users table.
+
+        If no homedir argument is specified the realuser's home
+        directory will possibly be determined and used.
+
+        realuser argument specifies the system user to use for managing
+        anonymous sessions.  On many UNIX systems "nobody" is tipically
+        used but it may change (e.g. "ftp").
+        """
+        users = [entry.pw_name for entry in pwd.getpwall()]
+        if not realuser in users:
+            raise ftpserver.AuthorizerError('No such user "%s".' %realuser)
+        if not homedir:
+            homedir = pwd.getpwnam(realuser).pw_dir
+        ftpserver.DummyAuthorizer.add_anonymous(self, homedir, **kwargs)
+        self.anon_user = realuser
+
+    def validate_authentication(self, username, password):
+        if (username == "anonymous") and self.has_user('anonymous'):
+            username = self.anon_user
+        pw1 = spwd.getspnam(username).sp_pwd
+        pw2 = crypt.crypt(password, pw1)
+        return pw1 == pw2
+
+    def impersonate_user(self, username, password):
+        if (username == "anonymous") and self.has_user('anonymous'):
+            username = self.anon_user
+        uid = pwd.getpwnam(username).pw_uid
+        gid = pwd.getpwnam(username).pw_gid
+        os.setegid(gid)
+        os.seteuid(uid)
+
+    def terminate_impersonation(self):
+        os.setegid(self.PROCESS_GID)
+        os.seteuid(self.PROCESS_UID)
+
+
+if __name__ == "__main__":
+    authorizer = UnixAuthorizer()
+    # add a user (note: user must already exists)
+    authorizer.add_user('user', perm='elradfmw')
+    authorizer.add_anonymous(os.getcwd())
+    ftp_handler = ftpserver.FTPHandler
+    ftp_handler.authorizer = authorizer
+    address = ('', 21)
+    ftpd = ftpserver.FTPServer(address, ftp_handler)
+    ftpd.serve_forever()