# -*- coding: utf-8 -*-

"""

    kallithea.lib.ssh

    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    :created_on: Dec 10, 2012

    :author: ir4y

    :copyright: (C) 2012 Ilya Beda <ir4y.ix@gmail.com>

    :license: GPLv3, see COPYING for more details.

"""

# This program is free software: you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation, either version 3 of the License, or

# (at your option) any later version.

#

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program.  If not, see <http://www.gnu.org/licenses/>.

import binascii

import logging

import re

from tg.i18n import ugettext as _

log = logging.getLogger(__name__)

class SshKeyParseError(Exception):

    """Exception raised by parse_pub_key"""

def parse_pub_key(ssh_key):

    r"""Parse SSH public key string, raise SshKeyParseError or return decoded keytype, data and comment

    >>> getfixture('doctest_mock_ugettext')

    >>> parse_pub_key('')

    Traceback (most recent call last):

    ...

    SshKeyParseError: SSH key is missing

    >>> parse_pub_key('''AAAAB3NzaC1yc2EAAAALVGhpcyBpcyBmYWtlIQ''')

    Traceback (most recent call last):

    ...

    >>> parse_pub_key('''abc AAAAB3NzaC1yc2EAAAALVGhpcyBpcyBmYWtlIQ''')

    Traceback (most recent call last):

    ...

    SshKeyParseError: Incorrect SSH key - it must start with 'ssh-(rsa|dss|ed25519)'

    >>> parse_pub_key('''ssh-rsa  AAAAB3NzaC1yc2EAAAALVGhpcyBpcyBmYWtlIQ''')

    Traceback (most recent call last):

    ...

    SshKeyParseError: Incorrect SSH key - failed to decode base64 part 'AAAAB3NzaC1yc2EAAAALVGhpcyBpcyBmYWtlIQ'

    >>> parse_pub_key('''ssh-rsa  AAAAB2NzaC1yc2EAAAALVGhpcyBpcyBmYWtlIQ==''')

    Traceback (most recent call last):

    ...

    SshKeyParseError: Incorrect SSH key - base64 part is not 'ssh-rsa' as claimed but 'csh-rsa'

    >>> parse_pub_key('''ssh-rsa  AAAAB3NzaC1yc2EAAAA'LVGhpcyBpcyBmYWtlIQ''')

    Traceback (most recent call last):

    ...

    SshKeyParseError: Incorrect SSH key - unexpected characters in base64 part "AAAAB3NzaC1yc2EAAAA'LVGhpcyBpcyBmYWtlIQ"

    >>> parse_pub_key(''' ssh-rsa  AAAAB3NzaC1yc2EAAAALVGhpcyBpcyBmYWtlIQ== and a comment

    ... ''')

    ('ssh-rsa', '\x00\x00\x00\x07ssh-rsa\x00\x00\x00\x0bThis is fake!', 'and a comment\n')

    >>> parse_pub_key('''ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIP1NA2kBQIKe74afUXmIWD9ByDYQJqUwW44Y4gJOBRuo''')

    ('ssh-ed25519', '\x00\x00\x00\x0bssh-ed25519\x00\x00\x00 \xfdM\x03i\x01@\x82\x9e\xef\x86\x9fQy\x88X?A\xc86\x10&\xa50[\x8e\x18\xe2\x02N\x05\x1b\xa8', '')

    """

    if not ssh_key:

        raise SshKeyParseError(_("SSH key is missing"))

    parts = ssh_key.split(None, 2)

    if len(parts) < 2:

    keytype, keyvalue, comment = (parts + [''])[:3]

    if keytype not in ('ssh-rsa', 'ssh-dss', 'ssh-ed25519'):

        raise SshKeyParseError(_("Incorrect SSH key - it must start with 'ssh-(rsa|dss|ed25519)'"))

    if re.search(r'[^a-zA-Z0-9+/=]', keyvalue):

        raise SshKeyParseError(_("Incorrect SSH key - unexpected characters in base64 part %r") % keyvalue)

    try:

        decoded = keyvalue.decode('base64')

    except binascii.Error:

        raise SshKeyParseError(_("Incorrect SSH key - failed to decode base64 part %r") % keyvalue)

    if not decoded.startswith('\x00\x00\x00' + chr(len(keytype)) + str(keytype) + '\x00'):

        raise SshKeyParseError(_("Incorrect SSH key - base64 part is not %r as claimed but %r") % (str(keytype), str(decoded[4:].split('\0', 1)[0])))

    return keytype, decoded, comment

SSH_OPTIONS = 'no-pty,no-port-forwarding,no-X11-forwarding,no-agent-forwarding'

def authorized_keys_line(kallithea_cli_path, config_file, key):

    """

    Return a line as it would appear in .authorized_keys

    >>> from kallithea.model.db import UserSshKeys, User

    >>> user = User(user_id=7, username='uu')

    >>> key = UserSshKeys(user_ssh_key_id=17, user=user, description='test key')

    >>> key.public_key='''ssh-rsa  AAAAB3NzaC1yc2EAAAALVGhpcyBpcyBmYWtlIQ== and a comment'''

    >>> authorized_keys_line('/srv/kallithea/venv/bin/kallithea-cli', '/srv/kallithea/my.ini', key)

    'no-pty,no-port-forwarding,no-X11-forwarding,no-agent-forwarding,command="/srv/kallithea/venv/bin/kallithea-cli ssh-serve -c /srv/kallithea/my.ini 7 17" ssh-rsa AAAAB3NzaC1yc2EAAAALVGhpcyBpcyBmYWtlIQ==\\n'

    """

    try:

        keytype, decoded, comment = parse_pub_key(key.public_key)

    except SshKeyParseError:

        return '# Invalid Kallithea SSH key: %s %s\n' % (key.user.user_id, key.user_ssh_key_id)

    mimekey = decoded.encode('base64').replace('\n', '')

    return '%s,command="%s ssh-serve -c %s %s %s" %s %s\n' % (

        SSH_OPTIONS, kallithea_cli_path, config_file,

        key.user.user_id, key.user_ssh_key_id,

        keytype, mimekey)

        ssh_key = UserSshKeys.query().filter(UserSshKeys.fingerprint == fingerprint)

        user = User.guess_instance(user)

        ssh_key = ssh_key.filter(UserSshKeys.user_id == user.user_id)

        ssh_key = ssh_key.scalar()

        if ssh_key is None:

            raise SshKeyModelException(_('SSH key with fingerprint %r found') % safe_str(fingerprint))

        Session().delete(ssh_key)

    def get_ssh_keys(self, user):

        user = User.guess_instance(user)

        user_ssh_keys = UserSshKeys.query() \

            .filter(UserSshKeys.user_id == user.user_id).all()

        return user_ssh_keys

    def write_authorized_keys(self):

        if not str2bool(config.get('ssh_enabled', False)):

            log.error("Will not write SSH authorized_keys file - ssh_enabled is not configured")

            return

        authorized_keys = config.get('ssh_authorized_keys')

        kallithea_cli_path = config.get('kallithea_cli_path', 'kallithea-cli')

        if not authorized_keys:

            log.error('Cannot write SSH authorized_keys file - ssh_authorized_keys is not configured')

            return

        log.info('Writing %s', authorized_keys)

        authorized_keys_dir = os.path.dirname(authorized_keys)

        try:

            os.makedirs(authorized_keys_dir)

            os.chmod(authorized_keys_dir, stat.S_IRUSR | stat.S_IWUSR | stat.S_IXUSR) # ~/.ssh/ must be 0700

        except OSError as exception:

            if exception.errno != errno.EEXIST:

                raise

        # Now, test that the directory is or was created in a readable way by previous.

        if not (os.path.isdir(authorized_keys_dir) and

                os.access(authorized_keys_dir, os.W_OK)):

            raise SshKeyModelException("Directory of authorized_keys cannot be written to so authorized_keys file %s cannot be written" % (authorized_keys))

        # Make sure we don't overwrite a key file with important content

        if os.path.exists(authorized_keys):

            with open(authorized_keys) as f:

                for l in f:

                    if not l.strip() or l.startswith('#'):

                        pass # accept empty lines and comments

                    elif ssh.SSH_OPTIONS in l and ' ssh-serve ' in l:

                        pass # Kallithea entries are ok to overwrite

                    else:

        fh, tmp_authorized_keys = tempfile.mkstemp('.authorized_keys', dir=os.path.dirname(authorized_keys))

        with os.fdopen(fh, 'w') as f:

            f.write("# WARNING: This .ssh/authorized_keys file is managed by Kallithea. Manual editing or adding new entries will make Kallithea back off.\n")

            for key in UserSshKeys.query().join(UserSshKeys.user).filter(User.active == True):

                f.write(ssh.authorized_keys_line(kallithea_cli_path, config['__file__'], key))

        os.chmod(tmp_authorized_keys, stat.S_IRUSR | stat.S_IWUSR)

        # This preliminary remove is needed for Windows, not for Unix.

        # TODO In Python 3, the remove+rename sequence below should become os.replace.

        if os.path.exists(authorized_keys):

            os.remove(authorized_keys)

        os.rename(tmp_authorized_keys, authorized_keys)