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"""Compat module to handle files security on Windows and
Linux"""
from __future__ import absolute_import

import errno
import os  # pylint: disable=os-module-forbidden
import stat

from acme.magic_typing import List

try:
    import ntsecuritycon
    import win32security
    import win32con
    import win32api
    import win32file
    import pywintypes
    import winerror
except ImportError:
    POSIX_MODE = True
else:
    POSIX_MODE = False


# Windows umask implementation, since Windows does not have a concept of
umask by default.
# We choose 022 as initial value since it is the default one on most Linux
distributions, and
# it is a decent choice to not have write permissions for group owner and
everybody by default.
# We use a class here to avoid needing to define a global variable, and the
potential mistakes
# that could happen with this kind of pattern.
class _WindowsUmask:
    """Store the current umask to apply on
Windows"""
    def __init__(self):
        self.mask = 0o022


_WINDOWS_UMASK = _WindowsUmask()


def chmod(file_path, mode):
    # type: (str, int) -> None
    """
    Apply a POSIX mode on given file_path:

      - for Linux, the POSIX mode will be directly applied using chmod,
      - for Windows, the POSIX mode will be translated into a Windows DACL
that make sense for
        Certbot context, and applied to the file using kernel calls.

    The definition of the Windows DACL that correspond to a POSIX mode, in
the context of Certbot,
    is explained at https://github.com/certbot/certbot/issues/6356 and is
implemented by the
    method `_generate_windows_flags()`.

    :param str file_path: Path of the file
    :param int mode: POSIX mode to apply
    """
    if POSIX_MODE:
        os.chmod(file_path, mode)
    else:
        _apply_win_mode(file_path, mode)


def umask(mask):
    # type: (int) -> int
    """
    Set the current numeric umask and return the previous umask. On Linux,
the built-in umask
    method is used. On Windows, our Certbot-side implementation is used.

    :param int mask: The user file-creation mode mask to apply.
    :rtype: int
    :return: The previous umask value.
    """
    if POSIX_MODE:
        return os.umask(mask)

    previous_umask = _WINDOWS_UMASK.mask
    _WINDOWS_UMASK.mask = mask
    return previous_umask


# One could ask why there is no copy_ownership() function, or even a
reimplementation
# of os.chown() that would modify the ownership of file without touching
the mode itself.
# This is because on Windows, it would require recalculating the existing
DACL against
# the new owner, since the DACL is composed of ACEs that targets a specific
user, not dynamically
# the current owner of a file. This action would be necessary to keep
consistency between
# the POSIX mode applied to the file and the current owner of this file.
# Since copying and editing arbitrary DACL is very difficult, and since we
actually know
# the mode to apply at the time the owner of a file should change, it is
easier to just
# change the owner, then reapply the known mode, as
copy_ownership_and_apply_mode() does.
def copy_ownership_and_apply_mode(src, dst, mode, copy_user, copy_group):
    # type: (str, str, int, bool, bool) -> None
    """
    Copy ownership (user and optionally group on Linux) from the source to
the
    destination, then apply given mode in compatible way for Linux and
Windows.
    This replaces the os.chown command.

    :param str src: Path of the source file
    :param str dst: Path of the destination file
    :param int mode: Permission mode to apply on the destination file
    :param bool copy_user: Copy user if `True`
    :param bool copy_group: Copy group if `True` on Linux (has no effect on
Windows)
    """
    if POSIX_MODE:
        stats = os.stat(src)
        user_id = stats.st_uid if copy_user else -1
        group_id = stats.st_gid if copy_group else -1
        # On Windows, os.chown does not exist. This is checked through
POSIX_MODE value,
        # but MyPy/PyLint does not know it and raises an error here on
Windows.
        # We disable specifically the check to fix the issue.
        os.chown(dst, user_id, group_id)
    elif copy_user:
        # There is no group handling in Windows
        _copy_win_ownership(src, dst)

    chmod(dst, mode)


# Quite similar to copy_ownership_and_apply_mode, but this time the DACL is
copied from
# the source file on Windows. The DACL stays consistent with the dynamic
rights of the
# equivalent POSIX mode, because ownership and mode are copied altogether
on the destination
# file, so no recomputing of the DACL against the new owner is needed, as
it would be
# for a copy_ownership alone method.
def copy_ownership_and_mode(src, dst, copy_user=True, copy_group=True):
    # type: (str, str, bool, bool) -> None
    """
    Copy ownership (user and optionally group on Linux) and mode/DACL
    from the source to the destination.

    :param str src: Path of the source file
    :param str dst: Path of the destination file
    :param bool copy_user: Copy user if `True`
    :param bool copy_group: Copy group if `True` on Linux (has no effect on
Windows)
    """
    if POSIX_MODE:
        # On Linux, we just delegate to chown and chmod.
        stats = os.stat(src)
        user_id = stats.st_uid if copy_user else -1
        group_id = stats.st_gid if copy_group else -1
        os.chown(dst, user_id, group_id)
        chmod(dst, stats.st_mode)
    else:
        if copy_user:
            # There is no group handling in Windows
            _copy_win_ownership(src, dst)
        _copy_win_mode(src, dst)


def check_mode(file_path, mode):
    # type: (str, int) -> bool
    """
    Check if the given mode matches the permissions of the given file.
    On Linux, will make a direct comparison, on Windows, mode will be
compared against
    the security model.

    :param str file_path: Path of the file
    :param int mode: POSIX mode to test
    :rtype: bool
    :return: True if the POSIX mode matches the file permissions
    """
    if POSIX_MODE:
        return stat.S_IMODE(os.stat(file_path).st_mode) == mode

    return _check_win_mode(file_path, mode)


def check_owner(file_path):
    # type: (str) -> bool
    """
    Check if given file is owned by current user.

    :param str file_path: File path to check
    :rtype: bool
    :return: True if given file is owned by current user, False otherwise.
    """
    if POSIX_MODE:
        # On Windows, os.getuid does not exist. This is checked through
POSIX_MODE value,
        # but MyPy/PyLint does not know it and raises an error here on
Windows.
        # We disable specifically the check to fix the issue.
        return os.stat(file_path).st_uid == os.getuid()  # type: ignore

    # Get owner sid of the file
    security = win32security.GetFileSecurity(file_path,
win32security.OWNER_SECURITY_INFORMATION)
    user = security.GetSecurityDescriptorOwner()

    # Compare sids
    return _get_current_user() == user


def check_permissions(file_path, mode):
    # type: (str, int) -> bool
    """
    Check if given file has the given mode and is owned by current user.

    :param str file_path: File path to check
    :param int mode: POSIX mode to check
    :rtype: bool
    :return: True if file has correct mode and owner, False otherwise.
    """
    return check_owner(file_path) and check_mode(file_path, mode)


def open(file_path, flags, mode=0o777):  # pylint:
disable=redefined-builtin
    # type: (str, int, int) -> int
    """
    Wrapper of original os.open function, that will ensure on Windows that
given mode
    is correctly applied.

    :param str file_path: The file path to open
    :param int flags: Flags to apply on file while opened
    :param int mode: POSIX mode to apply on file when opened,
        Python defaults will be applied if ``None``
    :returns: the file descriptor to the opened file
    :rtype: int
    :raise: OSError(errno.EEXIST) if the file already exists and os.O_CREAT
& os.O_EXCL are set,
            OSError(errno.EACCES) on Windows if the file already exists and
is a directory, and
            os.O_CREAT is set.
    """
    if POSIX_MODE:
        # On Linux, invoke os.open directly.
        return os.open(file_path, flags, mode)

    # Windows: handle creation of the file atomically with proper
permissions.
    if flags & os.O_CREAT:
        # If os.O_EXCL is set, we will use the "CREATE_NEW", that
will raise an exception if
        # file exists, matching the API contract of this bit flag.
Otherwise, we use
        # "CREATE_ALWAYS" that will always create the file
whether it exists or not.
        disposition = win32con.CREATE_NEW if flags & os.O_EXCL else
win32con.CREATE_ALWAYS

        attributes = win32security.SECURITY_ATTRIBUTES()
        security = attributes.SECURITY_DESCRIPTOR
        user = _get_current_user()
        dacl = _generate_dacl(user, mode, _WINDOWS_UMASK.mask)
        # We set second parameter to 0 (`False`) to say that this security
descriptor is
        # NOT constructed from a default mechanism, but is explicitly set
by the user.
        # See
https://docs.microsoft.com/en-us/windows/desktop/api/securitybaseapi/nf-securitybaseapi-setsecuritydescriptorowner
 # pylint: disable=line-too-long
        security.SetSecurityDescriptorOwner(user, 0)
        # We set first parameter to 1 (`True`) to say that this security
descriptor contains
        # a DACL. Otherwise second and third parameters are ignored.
        # We set third parameter to 0 (`False`) to say that this security
descriptor is
        # NOT constructed from a default mechanism, but is explicitly set
by the user.
        # See
https://docs.microsoft.com/en-us/windows/desktop/api/securitybaseapi/nf-securitybaseapi-setsecuritydescriptordacl
 # pylint: disable=line-too-long
        security.SetSecurityDescriptorDacl(1, dacl, 0)

        handle = None
        try:
            handle = win32file.CreateFile(file_path,
win32file.GENERIC_READ,
                                          win32file.FILE_SHARE_READ &
win32file.FILE_SHARE_WRITE,
                                          attributes, disposition, 0, None)
        except pywintypes.error as err:
            # Handle native windows errors into python errors to be
consistent with the API
            # of os.open in the situation of a file already existing or
locked.
            if err.winerror == winerror.ERROR_FILE_EXISTS:
                raise OSError(errno.EEXIST, err.strerror)
            if err.winerror == winerror.ERROR_SHARING_VIOLATION:
                raise OSError(errno.EACCES, err.strerror)
            raise err
        finally:
            if handle:
                handle.Close()

        # At this point, the file that did not exist has been created with
proper permissions,
        # so os.O_CREAT and os.O_EXCL are not needed anymore. We remove
them from the flags to
        # avoid a FileExists exception before calling os.open.
        return os.open(file_path, flags ^ os.O_CREAT ^ os.O_EXCL)

    # Windows: general case, we call os.open, let exceptions be thrown,
then chmod if all is fine.
    handle = os.open(file_path, flags)
    chmod(file_path, mode)
    return handle


def makedirs(file_path, mode=0o777):
    # type: (str, int) -> None
    """
    Rewrite of original os.makedirs function, that will ensure on Windows
that given mode
    is correctly applied.

    :param str file_path: The file path to open
    :param int mode: POSIX mode to apply on leaf directory when created,
Python defaults
                     will be applied if ``None``
    """
    current_umask = umask(0)
    try:
        # Since Python 3.7, os.makedirs does not set the given mode to the
intermediate
        # directories that could be created in the process. To keep things
safe and consistent
        # on all Python versions, we set the umask accordingly to have all
directories
        # (intermediate and leaf) created with the given mode.
        umask(current_umask | 0o777 ^ mode)

        if POSIX_MODE:
            return os.makedirs(file_path, mode)

        orig_mkdir_fn = os.mkdir
        try:
            # As we know that os.mkdir is called internally by os.makedirs,
we will swap the
            # function in os module for the time of makedirs execution on
Windows.
            os.mkdir = mkdir  # type: ignore
            return os.makedirs(file_path, mode)
        finally:
            os.mkdir = orig_mkdir_fn
    finally:
        umask(current_umask)


def mkdir(file_path, mode=0o777):
    # type: (str, int) -> None
    """
    Rewrite of original os.mkdir function, that will ensure on Windows that
given mode
    is correctly applied.

    :param str file_path: The file path to open
    :param int mode: POSIX mode to apply on directory when created, Python
defaults
                     will be applied if ``None``
    """
    if POSIX_MODE:
        return os.mkdir(file_path, mode)

    attributes = win32security.SECURITY_ATTRIBUTES()
    security = attributes.SECURITY_DESCRIPTOR
    user = _get_current_user()
    dacl = _generate_dacl(user, mode, _WINDOWS_UMASK.mask)
    security.SetSecurityDescriptorOwner(user, False)
    security.SetSecurityDescriptorDacl(1, dacl, 0)

    try:
        win32file.CreateDirectory(file_path, attributes)
    except pywintypes.error as err:
        # Handle native windows error into python error to be consistent
with the API
        # of os.mkdir in the situation of a directory already existing.
        if err.winerror == winerror.ERROR_ALREADY_EXISTS:
            raise OSError(errno.EEXIST, err.strerror, file_path,
err.winerror)
        raise err

    return None


def replace(src, dst):
    # type: (str, str) -> None
    """
    Rename a file to a destination path and handles situations where the
destination exists.

    :param str src: The current file path.
    :param str dst: The new file path.
    """
    if hasattr(os, 'replace'):
        # Use replace if possible. Since we don't support Python 2 on
Windows
        # and os.replace() was added in Python 3.3, we can assume that
        # os.replace() is always available on Windows.
        getattr(os, 'replace')(src, dst)
    else:
        # Otherwise, use os.rename() that behaves like os.replace() on
Linux.
        os.rename(src, dst)


def realpath(file_path):
    # type: (str) -> str
    """
    Find the real path for the given path. This method resolves symlinks,
including
    recursive symlinks, and is protected against symlinks that creates an
infinite loop.

    :param str file_path: The path to resolve
    :returns: The real path for the given path
    :rtype: str
    """
    original_path = file_path

    if POSIX_MODE:
        path = os.path.realpath(file_path)
        if os.path.islink(path):
            # If path returned by realpath is still a link, it means that
it failed to
            # resolve the symlink because of a loop.
            # See realpath code:
https://github.com/python/cpython/blob/master/Lib/posixpath.py
            raise RuntimeError('Error, link {0} is a
loop!'.format(original_path))
        return path

    inspected_paths = []  # type: List[str]
    while os.path.islink(file_path):
        link_path = file_path
        file_path = os.readlink(file_path)
        if not os.path.isabs(file_path):
            file_path = os.path.join(os.path.dirname(link_path), file_path)
        if file_path in inspected_paths:
            raise RuntimeError('Error, link {0} is a
loop!'.format(original_path))
        inspected_paths.append(file_path)

    return os.path.abspath(file_path)


# On Windows is_executable run from an unprivileged shell may claim that a
path is
# executable when it is excutable only if run from a privileged shell. This
result
# is due to the fact that GetEffectiveRightsFromAcl calculate effective
rights
# without taking into consideration if the target user has currently
required the
# elevated privileges or not. However this is not a problem since certbot
always
# requires to be run under a privileged shell, so the user will always
benefit
# from the highest (privileged one) set of permissions on a given file.
def is_executable(path):
    # type: (str) -> bool
    """
    Is path an executable file?

    :param str path: path to test
    :return: True if path is an executable file
    :rtype: bool
    """
    if POSIX_MODE:
        return os.path.isfile(path) and os.access(path, os.X_OK)

    return _win_is_executable(path)


def has_world_permissions(path):
    # type: (str) -> bool
    """
    Check if everybody/world has any right (read/write/execute) on a file
given its path.

    :param str path: path to test
    :return: True if everybody/world has any right to the file
    :rtype: bool
    """
    if POSIX_MODE:
        return bool(stat.S_IMODE(os.stat(path).st_mode) & stat.S_IRWXO)

    security = win32security.GetFileSecurity(path,
win32security.DACL_SECURITY_INFORMATION)
    dacl = security.GetSecurityDescriptorDacl()

    return bool(dacl.GetEffectiveRightsFromAcl({
        'TrusteeForm': win32security.TRUSTEE_IS_SID,
        'TrusteeType': win32security.TRUSTEE_IS_USER,
        'Identifier':
win32security.ConvertStringSidToSid('S-1-1-0'),
    }))


def compute_private_key_mode(old_key, base_mode):
    # type: (str, int) -> int
    """
    Calculate the POSIX mode to apply to a private key given the previous
private key.

    :param str old_key: path to the previous private key
    :param int base_mode: the minimum modes to apply to a private key
    :return: the POSIX mode to apply
    :rtype: int
    """
    if POSIX_MODE:
        # On Linux, we keep read/write/execute permissions
        # for group and read permissions for everybody.
        old_mode = (stat.S_IMODE(os.stat(old_key).st_mode) &
                    (stat.S_IRGRP | stat.S_IWGRP | stat.S_IXGRP |
stat.S_IROTH))
        return base_mode | old_mode

    # On Windows, the mode returned by os.stat is not reliable,
    # so we do not keep any permission from the previous private key.
    return base_mode


def has_same_ownership(path1, path2):
    # type: (str, str) -> bool
    """
    Return True if the ownership of two files given their respective path
is the same.
    On Windows, ownership is checked against owner only, since files do not
have a group owner.

    :param str path1: path to the first file
    :param str path2: path to the second file
    :return: True if both files have the same ownership, False otherwise
    :rtype: bool

    """
    if POSIX_MODE:
        stats1 = os.stat(path1)
        stats2 = os.stat(path2)
        return (stats1.st_uid, stats1.st_gid) == (stats2.st_uid,
stats2.st_gid)

    security1 = win32security.GetFileSecurity(path1,
win32security.OWNER_SECURITY_INFORMATION)
    user1 = security1.GetSecurityDescriptorOwner()

    security2 = win32security.GetFileSecurity(path2,
win32security.OWNER_SECURITY_INFORMATION)
    user2 = security2.GetSecurityDescriptorOwner()

    return user1 == user2


def has_min_permissions(path, min_mode):
    # type: (str, int) -> bool
    """
    Check if a file given its path has at least the permissions defined by
the given minimal mode.
    On Windows, group permissions are ignored since files do not have a
group owner.

    :param str path: path to the file to check
    :param int min_mode: the minimal permissions expected
    :return: True if the file matches the minimal permissions expectations,
False otherwise
    :rtype: bool
    """
    if POSIX_MODE:
        st_mode = os.stat(path).st_mode
        return st_mode == st_mode | min_mode

    # Resolve symlinks, to get a consistent result with os.stat on Linux,
    # that follows symlinks by default.
    path = realpath(path)

    # Get owner sid of the file
    security = win32security.GetFileSecurity(
        path, win32security.OWNER_SECURITY_INFORMATION |
win32security.DACL_SECURITY_INFORMATION)
    user = security.GetSecurityDescriptorOwner()
    dacl = security.GetSecurityDescriptorDacl()
    min_dacl = _generate_dacl(user, min_mode)

    for index in range(min_dacl.GetAceCount()):
        min_ace = min_dacl.GetAce(index)

        # On a given ACE, index 0 is the ACE type, 1 is the permission
mask, and 2 is the SID.
        # See: http://timgolden.me.uk/pywin32-docs/PyACL__GetAce_meth.html
        mask = min_ace[1]
        user = min_ace[2]

        effective_mask = dacl.GetEffectiveRightsFromAcl({
            'TrusteeForm': win32security.TRUSTEE_IS_SID,
            'TrusteeType': win32security.TRUSTEE_IS_USER,
            'Identifier': user,
        })

        if effective_mask != effective_mask | mask:
            return False

    return True


def _win_is_executable(path):
    if not os.path.isfile(path):
        return False

    security = win32security.GetFileSecurity(path,
win32security.DACL_SECURITY_INFORMATION)
    dacl = security.GetSecurityDescriptorDacl()

    mode = dacl.GetEffectiveRightsFromAcl({
        'TrusteeForm': win32security.TRUSTEE_IS_SID,
        'TrusteeType': win32security.TRUSTEE_IS_USER,
        'Identifier': _get_current_user(),
    })

    return mode & ntsecuritycon.FILE_GENERIC_EXECUTE ==
ntsecuritycon.FILE_GENERIC_EXECUTE


def _apply_win_mode(file_path, mode):
    """
    This function converts the given POSIX mode into a Windows ACL list,
and applies it to the
    file given its path. If the given path is a symbolic link, it will
resolved to apply the
    mode on the targeted file.
    """
    file_path = realpath(file_path)
    # Get owner sid of the file
    security = win32security.GetFileSecurity(file_path,
win32security.OWNER_SECURITY_INFORMATION)
    user = security.GetSecurityDescriptorOwner()

    # New DACL, that will overwrite existing one (including inherited
permissions)
    dacl = _generate_dacl(user, mode)

    # Apply the new DACL
    security.SetSecurityDescriptorDacl(1, dacl, 0)
    win32security.SetFileSecurity(file_path,
win32security.DACL_SECURITY_INFORMATION, security)


def _generate_dacl(user_sid, mode, mask=None):
    if mask:
        mode = mode & (0o777 - mask)
    analysis = _analyze_mode(mode)

    # Get standard accounts from "well-known" sid
    # See the list here:
    #
https://support.microsoft.com/en-us/help/243330/well-known-security-identifiers-in-windows-operating-systems
    system = win32security.ConvertStringSidToSid('S-1-5-18')
    admins = win32security.ConvertStringSidToSid('S-1-5-32-544')
    everyone = win32security.ConvertStringSidToSid('S-1-1-0')

    # New dacl, without inherited permissions
    dacl = win32security.ACL()

    # If user is already system or admins, any ACE defined here would be
superseded by
    # the full control ACE that will be added after.
    if user_sid not in [system, admins]:
        # Handle user rights
        user_flags = _generate_windows_flags(analysis['user'])
        if user_flags:
            dacl.AddAccessAllowedAce(win32security.ACL_REVISION,
user_flags, user_sid)

    # Handle everybody rights
    everybody_flags = _generate_windows_flags(analysis['all'])
    if everybody_flags:
        dacl.AddAccessAllowedAce(win32security.ACL_REVISION,
everybody_flags, everyone)

    # Handle administrator rights
    full_permissions = _generate_windows_flags({'read': True,
'write': True, 'execute': True})
    dacl.AddAccessAllowedAce(win32security.ACL_REVISION, full_permissions,
system)
    dacl.AddAccessAllowedAce(win32security.ACL_REVISION, full_permissions,
admins)

    return dacl


def _analyze_mode(mode):
    return {
        'user': {
            'read': mode & stat.S_IRUSR,
            'write': mode & stat.S_IWUSR,
            'execute': mode & stat.S_IXUSR,
        },
        'all': {
            'read': mode & stat.S_IROTH,
            'write': mode & stat.S_IWOTH,
            'execute': mode & stat.S_IXOTH,
        },
    }


def _copy_win_ownership(src, dst):
    # Resolve symbolic links
    src = realpath(src)

    security_src = win32security.GetFileSecurity(src,
win32security.OWNER_SECURITY_INFORMATION)
    user_src = security_src.GetSecurityDescriptorOwner()

    security_dst = win32security.GetFileSecurity(dst,
win32security.OWNER_SECURITY_INFORMATION)
    # Second parameter indicates, if `False`, that the owner of the file is
not provided by some
    # default mechanism, but is explicitly set instead. This is obviously
what we are doing here.
    security_dst.SetSecurityDescriptorOwner(user_src, False)

    win32security.SetFileSecurity(dst,
win32security.OWNER_SECURITY_INFORMATION, security_dst)


def _copy_win_mode(src, dst):
    # Resolve symbolic links
    src = realpath(src)

    # Copy the DACL from src to dst.
    security_src = win32security.GetFileSecurity(src,
win32security.DACL_SECURITY_INFORMATION)
    dacl = security_src.GetSecurityDescriptorDacl()

    security_dst = win32security.GetFileSecurity(dst,
win32security.DACL_SECURITY_INFORMATION)
    security_dst.SetSecurityDescriptorDacl(1, dacl, 0)
    win32security.SetFileSecurity(dst,
win32security.DACL_SECURITY_INFORMATION, security_dst)


def _generate_windows_flags(rights_desc):
    # Some notes about how each POSIX right is interpreted.
    #
    # For the rights read and execute, we have a pretty bijective relation
between
    # POSIX flags and their generic counterparts on Windows, so we use them
directly
    # (respectively ntsecuritycon.FILE_GENERIC_READ and
ntsecuritycon.FILE_GENERIC_EXECUTE).
    #
    # But ntsecuritycon.FILE_GENERIC_WRITE does not correspond to what one
could expect from a
    # write access on Linux: for Windows, FILE_GENERIC_WRITE does not
include delete, move or
    # rename. This is something that requires
ntsecuritycon.FILE_ALL_ACCESS.
    # So to reproduce the write right as POSIX, we will apply
ntsecuritycon.FILE_ALL_ACCESS
    # subtracted of the rights corresponding to POSIX read and POSIX
execute.
    #
    # Finally, having read + write + execute gives a
ntsecuritycon.FILE_ALL_ACCESS,
    # so a "Full Control" on the file.
    #
    # A complete list of the rights defined on NTFS can be found here:
    #
https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2003/cc783530(v=ws.10)#permissions-for-files-and-folders
    flag = 0
    if rights_desc['read']:
        flag = flag | ntsecuritycon.FILE_GENERIC_READ
    if rights_desc['write']:
        flag = flag | (ntsecuritycon.FILE_ALL_ACCESS
                       ^ ntsecuritycon.FILE_GENERIC_READ
                       ^ ntsecuritycon.FILE_GENERIC_EXECUTE)
    if rights_desc['execute']:
        flag = flag | ntsecuritycon.FILE_GENERIC_EXECUTE

    return flag


def _check_win_mode(file_path, mode):
    # Resolve symbolic links
    file_path = realpath(file_path)
    # Get current dacl file
    security = win32security.GetFileSecurity(file_path,
win32security.OWNER_SECURITY_INFORMATION
                                             |
win32security.DACL_SECURITY_INFORMATION)
    dacl = security.GetSecurityDescriptorDacl()

    # Get current file owner sid
    user = security.GetSecurityDescriptorOwner()

    if not dacl:
        # No DACL means full control to everyone
        # This is not a deterministic permissions set.
        return False

    # Calculate the target dacl
    ref_dacl = _generate_dacl(user, mode)

    return _compare_dacls(dacl, ref_dacl)


def _compare_dacls(dacl1, dacl2):
    """
    This method compare the two given DACLs to check if they are identical.
    Identical means here that they contains the same set of ACEs in the
same order.
    """
    return ([dacl1.GetAce(index) for index in range(dacl1.GetAceCount())]
==
            [dacl2.GetAce(index) for index in range(dacl2.GetAceCount())])


def _get_current_user():
    """
    Return the pySID corresponding to the current user.
    """
    # We craft the account_name ourselves instead of calling for instance
win32api.GetUserNameEx,
    # because this function returns nonsense values when Certbot is run
under NT AUTHORITY\SYSTEM.
    # To run Certbot under NT AUTHORITY\SYSTEM, you can open a shell using
the instructions here:
    #
https://blogs.technet.microsoft.com/ben_parker/2010/10/27/how-do-i-run-powershell-execommand-prompt-as-the-localsystem-account-on-windows-7/
    account_name = r"{0}\{1}".format(win32api.GetDomainName(),
win32api.GetUserName())
    # LookupAccountName() expects the system name as first parameter. By
passing None to it,
    # we instruct Windows to first search the matching account in the
machine local accounts,
    # then into the primary domain accounts, if the machine has joined a
domain, then finally
    # into the trusted domains accounts. This is the preferred lookup
mechanism to use in Windows
    # if there is no reason to use a specific lookup mechanism.
    # See
https://docs.microsoft.com/en-us/windows/desktop/api/winbase/nf-winbase-lookupaccountnamea
    return win32security.LookupAccountName(None, account_name)[0]