我的FTP Server——ftp.py

在上文中，我们简要地学习了下FTP协议，链接 http://everet.org/2012/03/ftp-protocol.html。

有兴趣的同学们可以去围观下。

因为最近偶看了下FTP协议，所以决定写个FTP Server玩玩。毕竟一直写的都是应用程序，于是乎想写下服务器端的程序。

结果就有了ftp.py，名字灵感来源于web.py。

ftp.py

ftp.py由Python 2.x实现。目前有部署到我的服务器上。支持Windows、Unix和类Unix系统。支持多线程模式和多进程模式，不过在Windows上仅支持多线程模式。支持虚拟用户。

其中多进程模式支持以其他用户身份运行，加强了安全性。

bash

usage: ftp.py [-d] [-h] [-p port] [-o] [-t]
    -d become a daemon
    -h help
    -p listen port
    -o output log to stdout, by default, it outputs to a log file.
    -t thread mode, fork model by default

其中用户设置写在ftp.py.config中，如果文件不存在则默认使用anonymous账户。

用户设置文件ftp.py.config格式如下：

account_info = {
‘et’:{‘pass’:‘123456789’, ‘home_dir’:’/root/’},
‘lst’:{‘pass’:‘987654321’, ‘home_dir’:’/tmp/’}
}

也就是账户名+密码+家目录路径。

ftp.py.config

我们还可以在ftp.py的同级目录中通过ftp.py.config设置我们的FTP Server。

最大用户连接数 limit_connection_number

``超时时间（单位：秒）timeout

``默认家目录：default_home_dir

日志文件：logfile

运行的用户身份：runas_user

默认值为：

python

limit_connection_number = 5     # max client number
timeout = 60 * 3                # timeout in second
default_home_dir = os.path.normpath(os.path.abspath(os.curdir)).replace('\\', '/')
logfile = '/var/log/ftp.py.log' if os.name == 'posix' else default_home_dir + 'ftp.py.log'
runas_user = 'www-data'

源码如下：

最新的源码请见Git: https://github.com/cedricporter/ftp.py

python

#!/usr/bin/env python
# author:  Hua Liang [ Stupid ET ]
# email:   et@everet.org
# website: http://EverET.org
#
import socket, os, stat, threading, time, struct, getopt
import sys, re, signal, select, logging, logging.handlers

host = '0.0.0.0'
port = 21
limit_connection_number = 5     # max client number
timeout = 60 * 3                # timeout in second
default_home_dir = os.path.normpath(os.path.abspath(os.curdir)).replace('\\', '/')
logfile = '/var/log/ftp.py.log' if os.name == 'posix' else default_home_dir + 'ftp.py.log'

runas_user = 'www-data'
global_options = {'run_mode':'fork'}

# current working directory
account_info = {
    'anonymous':{'pass':'', 'home_dir':default_home_dir, 'runas_user':runas_user},
    } 

def runas(username):
    if os.name != 'posix': return
    uid = get_uid(username)
    os.setgid(uid)
    os.setuid(uid)

class FTPConnection:
    '''You can add handle func by startswith handle_ prefix.
    When the connection receives CWD command, it'll use handle_CWD to handle it.
    '''
    def __init__(self, fd, remote_ip):
        self.fd = fd
        self.data_fd = 0
        self.options = {'pasv': False, 'utf8': False}
        self.data_host = ''
        self.data_port = 0
        self.localhost = fd.getsockname()[0]
        self.home_dir = default_home_dir
        self.curr_dir = '/'
        self.running = True
        self.handler = dict(
            [(method[7:], getattr(self, method)) \
            for method in dir(self) \
            if method.startswith("handle_") and callable(getattr(self, method))])

    def start(self): 
        try:
            self.say_welcome()
            while self.running:
                success, command, arg = self.recv()
                command = command.upper()
                if self.options['utf8']:
                    arg = unicode(arg, 'utf8').encode(sys.getfilesystemencoding())
                logger.info('[ ' + command + ' ] ' + arg)
                if not success: 
                    self.send_msg(500, "Failed")
                    continue
                if not self.handler.has_key(command):
                    self.send_msg(500, "Command Not Found")
                    continue
                try:
                    self.handler[command](arg)
                except OSError, e:
                    logger.error(e)
                    logger.error("in start")
                    self.send_msg(500, 'Permission denied')
            self.say_bye()
        except Exception, e:
            self.running = False
            logger.error(e)
            logger.error("in start")
        finally:
            self.fd.close()

        logger.info("FTP connnection done.")

        return True

    def send_msg(self, code, msg):
        if self.options['utf8']:
            msg = unicode(msg, sys.getfilesystemencoding()).encode('utf8')
        message = str(code) + ' ' + msg + '\r\n'
        self.fd.send(message)

    def recv(self):
        '''returns 3 tuples, success, command, arg'''
        try:
            success, buf, command, arg = True, '', '', ''
            while True:
                data = self.fd.recv(4096)
                if not data or data <= 0:
                    self.running = False
                    success = False
                    break
                buf += data
                if buf[-2:] == '\r\n': break
            split = buf.find(' ')
            command, arg = (buf[:split], buf[split + 1:].strip()) if split != -1 else (buf.strip(), '')
        except Exception, e:
            logger.error(e)
            logger.error("in recv")
            self.running = False
            success = False

        return success, command, arg


    def say_welcome(self):
        self.send_msg(220, "Welcome to EverET.org FTP")

    def say_bye(self):
        self.handle_BYE('')

    def data_connect(self):
        '''establish data connection'''
        if self.data_fd == 0:
            self.send_msg(500, "no data connection")
            return False
        elif self.options['pasv']:
            fd, addr = self.data_fd.accept()
            self.data_fd.close()
            self.data_fd = fd
        else:
            try:
                self.data_fd.connect((self.data_host, self.data_port))
            except:
                self.send_msg(500, "failed to connect")
                return False
        return True

    def close_data_fd(self):
        self.data_fd.close()
        self.data_fd = 0

    def parse_path(self, path):
        if path == '': path = '.'
        if path[0] != '/': path = self.curr_dir + '/' + path
        logger.info('parse_path ' + path)
        split_path = os.path.normpath(path).replace('\\', '/').split('/')
        remote = '' 
        local = self.home_dir
        for item in split_path:
            if item.startswith('..') or item == '': continue # ignore parent directory
            remote += '/' + item
            local += '/' + item
        if remote == '': remote = '/'
        logger.info(split_path)
        logger.info('remote: %s  local: %s' % (remote, local))
        return remote, local

    # Command Handlers
    def handle_USER(self, arg):
        if arg in account_info:
            self.username = arg
            if self.username == 'anonymous':
                self.send_msg(230, 'OK')
            else:
                self.send_msg(331, "Need password")
        else:
            self.send_msg(500, "Invalid User")
            self.running = False
    def handle_PASS(self, arg):
        if arg == account_info[self.username]['pass']: 
            self.home_dir = account_info[self.username]['home_dir']
            if account_info[self.username].has_key('runas_user'):
                user = account_info[self.username]['runas_user']
            else:
                user = 'www-data'
            runas(user) 
            if os.path.isdir(self.home_dir):
                self.send_msg(230, "OK")
                return
        self.send_msg(530, "Password is not corrected")
        self.running = False
    def handle_QUIT(self, arg):
        self.handle_BYE(arg)
    def handle_BYE(self, arg):
        self.running = False
        self.send_msg(200, "OK")
    def handle_CDUP(self, arg):
        self.handle_CWD('..')
    def handle_XPWD(self, arg):
        self.handle_PWD(arg)
    def handle_PWD(self, arg):
        remote, local = self.parse_path(self.curr_dir)
        self.send_msg(257, '"' + remote + '"')
    def handle_CWD(self, arg):
        remote, local = self.parse_path(arg)
        try:
            os.listdir(local)
            self.curr_dir = remote
            self.send_msg(250, "OK")
        except Exception, e:
            logger.error(e)
            logger.error("in cwd")
            self.send_msg(500, "Change directory failed!")
    def handle_SIZE(self, arg):
        remote, local = self.parse_path(self.curr_dir)
        self.send_msg(231, str(os.path.getsize(local)))
    def handle_SYST(self, arg):
        self.send_msg(215, "UNIX")
    def handle_STOR(self, arg):
        remote, local = self.parse_path(arg)
        if not self.data_connect(): return
        self.send_msg(125, "OK")
        f = open(local, 'wb')
        while True:
            data = self.data_fd.recv(8192)
            if len(data) == 0: break
            f.write(data)
        f.close()
        self.close_data_fd()
        self.send_msg(226, "OK")
    def handle_RETR(self, arg):
        remote, local = self.parse_path(arg)
        if not self.data_connect(): return
        self.send_msg(125, "OK")
        f = open(local, 'rb')
        while True:
            data = f.read(8192)
            if len(data) == 0: break
            self.data_fd.send(data)
        f.close()
        self.close_data_fd()
        self.send_msg(226, "OK")
    def handle_TYPE(self, arg):
        self.send_msg(220, "OK")
    def handle_RNFR(self, arg):
        remote, local = self.parse_path(arg)
        self.rename_tmp_path = local
        self.send_msg(350, 'rename from ' + remote)
    def handle_RNTO(self, arg):
        remote, local = self.parse_path(arg)
        os.rename(self.rename_tmp_path, local)
        self.send_msg(250, 'rename to ' + remote)
    def handle_NLST(self, arg):
        if not self.data_connect(): return
        self.send_msg(125, "OK")
        remote, local = self.parse_path(self.curr_dir)
        for filename in os.listdir(local):
            self.data_fd.send(filename + '\r\n')
        self.send_msg(226, "Limit")
        self.close_data_fd()
    def handle_XMKD(self, arg):
        self.handle_MKD(arg)
    def handle_MKD(self, arg):
        remote, local = self.parse_path(arg)
        if os.path.exists(local):
            self.send_msg(500, "Folder is already existed")
            return
        os.mkdir(local)
        self.send_msg(257, "OK")
    def handle_XRMD(self, arg):
        self.handle_RMD(arg)
    def handle_RMD(self, arg):
        remote, local = self.parse_path(arg)
        if not os.path.exists(local):
            self.send_msg(500, "Folder is not existed")
            return
        os.rmdir(local)
        self.send_msg(250, "OK")
    def handle_LIST(self, arg):
        if not self.data_connect(): return 
        self.send_msg(125, "OK")
        template = "%s%s%s------- %04u %8s %8s %8lu %s %s\r\n"
        remote, local = self.parse_path(self.curr_dir)
        for filename in os.listdir(local):
            path = local + '/' + filename
            if os.path.isfile(path) or os.path.isdir(path): # ignores link or block file
                status = os.stat(path)
                msg = template % (
                    'd' if os.path.isdir(path) else '-',
                    'r', 'w', 1, '0', '0', 
                    status[stat.ST_SIZE], 
                    time.strftime("%b %d  %Y", time.localtime(status[stat.ST_MTIME])), 
                    filename)
                if self.options['utf8']: msg = unicode(msg, sys.getfilesystemencoding()).encode('utf8')
                self.data_fd.send(msg)
        self.send_msg(226, "Limit")
        self.close_data_fd()
    def handle_PASV(self, arg):
        self.options['pasv'] = True
        try:
            self.data_fd = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
            self.data_fd.bind((self.localhost, 0))
            self.data_fd.listen(1)
            ip, port = self.data_fd.getsockname()
            self.send_msg(227, 'Enter Passive Mode (%s,%u,%u).' %
                    (','.join(ip.split('.')), (port >> 8 & 0xff), (port & 0xff)))
        except Exception, e:
            logger.error(e)
            logger.error("in pasv")
            self.send_msg(500, 'passive mode failed')
    def handle_PORT(self, arg):
        try:
            if self.data_fd:
                self.data_fd.close()
            t = arg.split(',')
            self.data_host = '.'.join(t[:4])
            self.data_port = int(t[4]) * 256 + int(t[5])
            self.data_fd = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        except:
            self.send_msg(500, "PORT failed")
        self.send_msg(200, "OK")
    def handle_DELE(self, arg):
        remote, local = self.parse_path(arg)
        if not os.path.exists(local):
            self.send_msg(450, "File not exist")
            return
        os.remove(local)
        self.send_msg(250, 'File deleted')
    def handle_OPTS(self, arg):
        if arg.upper() == "UTF8 ON":
            self.options['utf8'] = True
            self.send_msg(200, "OK")
        elif arg.upper() == "UTF8 OFF":
            self.options['utf8'] = False
            self.send_msg(200, "OK")
        else:
            self.send_msg(500, "Invalid argument")
            


class FTPThread(threading.Thread):
    '''FTPConnection Thread Wrapper'''
    def __init__(self, fd, remote_ip):
        threading.Thread.__init__(self)
        self.ftp = FTPConnection(fd, remote_ip)

    def run(self):
        self.ftp.start()
        logger.info("Thread done")

class FTPThreadServer:
    '''FTP Server which is using thread'''
    def serve_forever(self):
        listen_fd = socket.socket()
        listen_fd.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        listen_fd.bind((host, port))
        listen_fd.listen(512)
        while True:
            logger.info('new server')
            client_fd, client_addr = listen_fd.accept()
            handler = FTPThread(client_fd, client_addr)
            handler.start()


class FTPForkServer:
    '''FTP Fork Server, use process per user'''
    def child_main(self, client_fd, client_addr, write_end):
        '''never return'''
        for fd in self.read_fds:
            os.close(fd)
        self.read_fds = []

        try:
            handler = FTPConnection(client_fd, client_addr)
            handler.start()
        except Exception, e:
            logger.error(e)
            logger.error("in child_main")

        os.write(write_end, str(write_end))

        sys.exit()

    def serve_forever(self):
        listen_fd = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        listen_fd.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        listen_fd.bind((host, port))
        listen_fd.listen(512)
        self.read_fds = [listen_fd]
        while True:
            rlist, wlist, xlist = select.select(self.read_fds, [], [])

            if listen_fd in rlist:
                client_fd, client_addr = listen_fd.accept()
                if len(self.read_fds) > limit_connection_number:
                    logger.error('reject client: ' + str(client_addr))
                    client_fd.close()
                    continue
                try:
                    logger.info('new client: ' + str(client_addr))
                    read_end, write_end = os.pipe()
                    self.read_fds.append(read_end)
                    fork_result = os.fork()
                    if fork_result == 0: # child process
                        listen_fd.close()
                        self.read_fds.remove(listen_fd)
                        self.child_main(client_fd, client_addr, write_end) # never return
                    else:
                        os.close(write_end)
                except Exception, e:
                    logger.error(e)
                    logger.error('Fork failed')
                    
            for read_fd in rlist:
                if read_fd == listen_fd: continue
                data = os.read(read_fd, 32)
                self.read_fds.remove(read_fd)
                os.close(read_fd)

                        

def get_uid(username = 'www-data'):
    '''get uid by username, I don't know whether there's a
    function can get it, so I wrote this function.'''
    pwd = open('/etc/passwd', 'r')
    pat = re.compile(username + ':.*?:(.*?):.*?')
    for line in pwd.readlines():
        try:
            uid = pat.search(line).group(1)
        except: continue
        return int(uid)

def get_logger(handler = logging.StreamHandler()):
    logger = logging.getLogger()
    formatter = logging.Formatter('%(asctime)s %(levelname)s %(message)s')
    handler.setFormatter(formatter)
    logger.addHandler(handler)
    logger.setLevel(logging.NOTSET)
    return logger

def daemonize(stdin='/dev/null', stdout='/dev/null', stderr='/dev/null'):
    '''becomes a daemon'''
    try:
        pid = os.fork()
        if pid > 0: sys.exit(0)
    except OSError, e:
        sys.stderr.write("fork #1 failed\n")
        sys.exit(1)

    os.umask(0)
    os.setsid()

    try:
        pid = os.fork()
        if pid > 0: sys.exit(0)
    except OSError, e:
        sys.stderr.write("fork #2 failed\n")
        sys.exit(1)

    for f in sys.stdout, sys.stderr: f.flush()
    si = file(stdin, 'r')
    so = file(stdout, 'a+')
    se = file(stderr, 'a+', 0)
    os.dup2(si.fileno(), sys.stdin.fileno())  # 0
    os.dup2(so.fileno(), sys.stdout.fileno()) # 1
    os.dup2(se.fileno(), sys.stderr.fileno()) # 2

def serve_forever():
    global global_options
    print global_options
    if global_options['run_mode'] == 'fork':
        signal.signal(signal.SIGCHLD, signal.SIG_IGN)
        server = FTPForkServer()
    else:
        server = FTPThreadServer()
        
    server.serve_forever()

def usage():
    print '''usage: %s [-d] [-h] [-p port] [-o] [-t]
    -d become a daemon
    -h help
    -p listen port
    -o output log to stdout, by default, it outputs to a log file.
    -t thread mode, fork model by default

Waring:
    The Thread Mode is not complete.

Author:
    Hua Liang [ Stupid ET ] <et@everet.org>
    http://EverET.org 
''' % os.path.basename(sys.argv[0])

def param_handler(opts):
    global port, logger, global_options
    be_daemon = False
    logger = get_logger(logging.FileHandler(logfile))
    for o, a in opts:
        if o == '-h':
            usage()
            sys.exit(0)
        elif o == '-d':
            if not os.name == 'posix':
                print 'Only support the os with posix specifications.'
                sys.exit(-1)
            be_daemon = True
        elif o == '-o': 
            logger = get_logger()
        elif o == '-p':
            try: port = int(a)
            except Exception, e:
                usage()
                sys.exit(0)
        elif o == '-t':
            global_options['run_mode'] = 'thread'

    if os.name != 'posix' and global_options['run_mode'] == 'fork':
        print "You can NOT run fork mode in a non posix os,\
 please use -t options to run in thread mode"
        sys.exit(-1)
    if be_daemon: daemonize()

if __name__ == '__main__': 
    try:
        opts, args = getopt.getopt(sys.argv[1:], 'hdp:ot')
    except getopt.GetoptError:
        usage()
        sys.exit(2)

    param_handler(opts)

    socket.setdefaulttimeout(timeout)

    '''You can write your account_info in ftp.py.config'''
    try: execfile('ftp.py.config')
    except Exception, e: logger.error(e) 

    serve_forever()