scp.py

# scp.py
# Copyright (C) 2008 James Bardin <j.bardin@gmail.com>

"""
Utilities for sending files over ssh using the scp1 protocol.
"""

__version__ = '0.8.0'

import locale
import os
import re
from socket import timeout as SocketTimeout

DEBUG = False

# this is quote from the shlex module, added in py3.3
_find_unsafe = re.compile(br'[^\w@%+=:,./~-]').search


def _sh_quote(s):
    """Return a shell-escaped version of the string `s`."""
    if not s:
        return b""
    if _find_unsafe(s) is None:
        return s

    # use single quotes, and put single quotes into double quotes
    # the string $'b is then quoted as '$'"'"'b'
    return b"'" + s.replace(b"'", b"'\"'\"'") + b"'"


# Unicode conversion functions; assume UTF-8

def asbytes(s):
    """Turns unicode into bytes, if needed.

    Assumes UTF-8.
    """
    if isinstance(s, bytes):
        return s
    else:
        return s.encode('utf-8')


def asunicode(s):
    """Turns bytes into unicode, if needed.

    Uses UTF-8.
    """
    if isinstance(s, bytes):
        return s.decode('utf-8', 'replace')
    else:
        return s


# os.path.sep is unicode on Python 3, no matter the platform
bytes_sep = asbytes(os.path.sep)


# Unicode conversion function for Windows
# Used to convert local paths if the local machine is Windows

def asunicode_win(s):
    """Turns bytes into unicode, if needed.
    """
    if isinstance(s, bytes):
        return s.decode(locale.getpreferredencoding())
    else:
        return s


class SCPClient(object):
    """
    An scp1 implementation, compatible with openssh scp.
    Raises SCPException for all transport related errors. Local filesystem
    and OS errors pass through.

    Main public methods are .put and .get
    The get method is controlled by the remote scp instance, and behaves
    accordingly. This means that symlinks are resolved, and the transfer is
    halted after too many levels of symlinks are detected.
    The put method uses os.walk for recursion, and sends files accordingly.
    Since scp doesn't support symlinks, we send file symlinks as the file
    (matching scp behaviour), but we make no attempt at symlinked directories.
    """
    def __init__(self, transport, buff_size=16384, socket_timeout=5.0,
                 progress=None, sanitize=_sh_quote):
        """
        Create an scp1 client.

        @param transport: an existing paramiko L{Transport}
        @type transport: L{Transport}
        @param buff_size: size of the scp send buffer.
        @type buff_size: int
        @param socket_timeout: channel socket timeout in seconds
        @type socket_timeout: float
        @param progress: callback - called with (filename, size, sent) during
            transfers
        @param sanitize: function - called with filename, should return
            safe or escaped string.  Uses _sh_quote by default.
        @type progress: function(string, int, int)
        """
        self.transport = transport
        self.buff_size = buff_size
        self.socket_timeout = socket_timeout
        self.channel = None
        self.preserve_times = False
        self._progress = progress
        self._recv_dir = b''
        self._rename = False
        self._utime = None
        self.sanitize = sanitize
        self._dirtimes = {}

    def put(self, files, remote_path=b'.',
            recursive=False, preserve_times=False):
        """
        Transfer files to remote host.

        @param files: A single path, or a list of paths to be transfered.
            recursive must be True to transfer directories.
        @type files: string OR list of strings
        @param remote_path: path in which to receive the files on the remote
            host. defaults to '.'
        @type remote_path: str
        @param recursive: transfer files and directories recursively
        @type recursive: bool
        @param preserve_times: preserve mtime and atime of transfered files
            and directories.
        @type preserve_times: bool
        """
        self.preserve_times = preserve_times
        self.channel = self.transport.open_session()
        self.channel.settimeout(self.socket_timeout)
        scp_command = (b'scp -t ', b'scp -r -t ')[recursive]
        self.channel.exec_command(scp_command +
                                  self.sanitize(asbytes(remote_path)))
        self._recv_confirm()

        if not isinstance(files, (list, tuple)):
            files = [files]

        if recursive:
            self._send_recursive(files)
        else:
            self._send_files(files)

        if self.channel:
            self.channel.close()

    def get(self, remote_path, local_path='',
            recursive=False, preserve_times=False):
        """
        Transfer files from remote host to localhost

        @param remote_path: path to retreive from remote host. since this is
            evaluated by scp on the remote host, shell wildcards and
            environment variables may be used.
        @type remote_path: str
        @param local_path: path in which to receive files locally
        @type local_path: str
        @param recursive: transfer files and directories recursively
        @type recursive: bool
        @param preserve_times: preserve mtime and atime of transfered files
            and directories.
        @type preserve_times: bool
        """
        if not isinstance(remote_path, (list, tuple)):
            remote_path = [remote_path]
        remote_path = [self.sanitize(asbytes(r)) for r in remote_path]
        self._recv_dir = local_path or os.getcwd()
        self._rename = (len(remote_path) == 1 and
                        not os.path.isdir(os.path.abspath(local_path)))
        if len(remote_path) > 1:
            if not os.path.exists(self._recv_dir):
                raise SCPException("Local path '%s' does not exist" %
                                   asunicode(self._recv_dir))
            elif not os.path.isdir(self._recv_dir):
                raise SCPException("Local path '%s' is not a directory" %
                                   asunicode(self._recv_dir))
        rcsv = (b'', b' -r')[recursive]
        prsv = (b'', b' -p')[preserve_times]
        self.channel = self.transport.open_session()
        self.channel.settimeout(self.socket_timeout)
        self.channel.exec_command(b"scp" +
                                  rcsv +
                                  prsv +
                                  b" -f " +
                                  b' '.join(remote_path))
        self._recv_all()

        if self.channel:
            self.channel.close()

    def _read_stats(self, name):
        """return just the file stats needed for scp"""
        stats = os.stat(name)
        mode = oct(stats.st_mode)[-4:]
        size = stats.st_size
        atime = int(stats.st_atime)
        mtime = int(stats.st_mtime)
        return (mode, size, mtime, atime)

    def _send_files(self, files):
        for name in files:
            basename = asbytes(os.path.basename(name))
            (mode, size, mtime, atime) = self._read_stats(name)
            if self.preserve_times:
                self._send_time(mtime, atime)
            file_hdl = open(name, 'rb')

            # The protocol can't handle \n in the filename.
            # Quote them as the control sequence \^J for now,
            # which is how openssh handles it.
            self.channel.sendall(("C%s %d " % (mode, size)).encode('ascii') +
                                 basename.replace(b'\n', b'\\^J') + b"\n")
            self._recv_confirm()
            file_pos = 0
            if self._progress:
                if size == 0:
                    # avoid divide-by-zero
                    self._progress(basename, 1, 1)
                else:
                    self._progress(basename, size, 0)
            buff_size = self.buff_size
            chan = self.channel
            while file_pos < size:
                chan.sendall(file_hdl.read(buff_size))
                file_pos = file_hdl.tell()
                if self._progress:
                    self._progress(basename, size, file_pos)
            chan.sendall('\x00')
            file_hdl.close()
            self._recv_confirm()

    def _chdir(self, from_dir, to_dir):
        # Pop until we're one level up from our next push.
        # Push *once* into to_dir.
        # This is dependent on the depth-first traversal from os.walk

        # add path.sep to each when checking the prefix, so we can use
        # path.dirname after
        common = os.path.commonprefix([from_dir + bytes_sep,
                                       to_dir + bytes_sep])
        # now take the dirname, since commonprefix is character based,
        # and we either have a seperator, or a partial name
        common = os.path.dirname(common)
        cur_dir = from_dir.rstrip(bytes_sep)
        while cur_dir != common:
            cur_dir = os.path.split(cur_dir)[0]
            self._send_popd()
        # now we're in our common base directory, so on
        self._send_pushd(to_dir)

    def _send_recursive(self, files):
        for base in files:
            if not os.path.isdir(base):
                # filename mixed into the bunch
                self._send_files([base])
                continue
            last_dir = asbytes(base)
            for root, dirs, fls in os.walk(base):
                self._chdir(last_dir, asbytes(root))
                self._send_files([os.path.join(root, f) for f in fls])
                last_dir = asbytes(root)
            # back out of the directory
            for i in range(len(os.path.split(last_dir))):
                self._send_popd()

    def _send_pushd(self, directory):
        (mode, size, mtime, atime) = self._read_stats(directory)
        basename = asbytes(os.path.basename(directory))
        if self.preserve_times:
            self._send_time(mtime, atime)
        self.channel.sendall(('D%s 0 ' % mode).encode('ascii') +
                             basename.replace(b'\n', b'\\^J') + b'\n')
        self._recv_confirm()

    def _send_popd(self):
        self.channel.sendall('E\n')
        self._recv_confirm()

    def _send_time(self, mtime, atime):
        self.channel.sendall(('T%d 0 %d 0\n' % (mtime, atime)).encode('ascii'))
        self._recv_confirm()

    def _recv_confirm(self):
        # read scp response
        msg = b''
        try:
            msg = self.channel.recv(512)
        except SocketTimeout:
            raise SCPException('Timout waiting for scp response')
        # slice off the first byte, so this compare will work in python2 and python3
        if msg and msg[0:1] == b'\x00':
            return
        elif msg and msg[0:1] == b'\x01':
            raise SCPException(asunicode(msg[1:]))
        elif self.channel.recv_stderr_ready():
            msg = self.channel.recv_stderr(512)
            raise SCPException(asunicode(msg))
        elif not msg:
            raise SCPException('No response from server')
        else:
            raise SCPException('Invalid response from server', msg)

    def _recv_all(self):
        # loop over scp commands, and receive as necessary
        command = {b'C': self._recv_file,
                   b'T': self._set_time,
                   b'D': self._recv_pushd,
                   b'E': self._recv_popd}
        while not self.channel.closed:
            # wait for command as long as we're open
            self.channel.sendall('\x00')
            msg = self.channel.recv(1024)
            if not msg:  # chan closed while recving
                break
            assert msg[-1:] == b'\n'
            msg = msg[:-1]
            code = msg[0:1]
            try:
                command[code](msg[1:])
            except KeyError:
                raise SCPException(str(msg).strip())
        # directory times can't be set until we're done writing files
        self._set_dirtimes()

    def _set_time(self, cmd):
        try:
            times = cmd.split(b' ')
            mtime = int(times[0])
            atime = int(times[2]) or mtime
        except:
            self.channel.send(b'\x01')
            raise SCPException('Bad time format')
        # save for later
        self._utime = (atime, mtime)

    def _recv_file(self, cmd):
        chan = self.channel
        parts = cmd.strip().split(b' ', 2)

        try:
            mode = int(parts[0], 8)
            size = int(parts[1])
            if self._rename:
                path = self._recv_dir
                self._rename = False
            elif os.name == 'nt':
                path = os.path.join(asunicode_win(self._recv_dir),
                                    parts[2].decode('utf-8'))
            else:
                path = os.path.join(asbytes(self._recv_dir),
                                    parts[2])
        except:
            chan.send('\x01')
            chan.close()
            raise SCPException('Bad file format')

        try:
            file_hdl = open(path, 'wb')
        except IOError as e:
            chan.send(b'\x01' + str(e).encode('utf-8'))
            chan.close()
            raise

        if self._progress:
            if size == 0:
                # avoid divide-by-zero
                self._progress(path, 1, 1)
            else:
                self._progress(path, size, 0)
        buff_size = self.buff_size
        pos = 0
        chan.send(b'\x00')
        try:
            while pos < size:
                # we have to make sure we don't read the final byte
                if size - pos <= buff_size:
                    buff_size = size - pos
                file_hdl.write(chan.recv(buff_size))
                pos = file_hdl.tell()
                if self._progress:
                    self._progress(path, size, pos)

            msg = chan.recv(512)
            if msg and msg[0:1] != b'\x00':
                raise SCPException(msg[1:])
        except SocketTimeout:
            chan.close()
            raise SCPException('Error receiving, socket.timeout')

        file_hdl.truncate()
        try:
            os.utime(path, self._utime)
            self._utime = None
            os.chmod(path, mode)
            # should we notify the other end?
        finally:
            file_hdl.close()
        # '\x00' confirmation sent in _recv_all

    def _recv_pushd(self, cmd):
        parts = cmd.split(b' ', 2)
        try:
            mode = int(parts[0], 8)
            if self._rename:
                path = self._recv_dir
                self._rename = False
            elif os.name == 'nt':
                path = os.path.join(asunicode_win(self._recv_dir),
                                    parts[2].decode('utf-8'))
            else:
                path = os.path.join(asbytes(self._recv_dir),
                                    parts[2])
        except:
            self.channel.send(b'\x01')
            raise SCPException('Bad directory format')
        try:
            if not os.path.exists(path):
                os.mkdir(path, mode)
            elif os.path.isdir(path):
                os.chmod(path, mode)
            else:
                raise SCPException('%s: Not a directory' % path)
            self._dirtimes[path] = (self._utime)
            self._utime = None
            self._recv_dir = path
        except (OSError, SCPException) as e:
            self.channel.send(b'\x01' + asbytes(str(e)))
            raise

    def _recv_popd(self, *cmd):
        self._recv_dir = os.path.split(self._recv_dir)[0]

    def _set_dirtimes(self):
        try:
            for d in self._dirtimes:
                os.utime(d, self._dirtimes[d])
        finally:
            self._dirtimes = {}


class SCPException(Exception):
    """SCP exception class"""
    pass