Source code for file.sign.generic

import os.path

from contextlib import contextmanager, suppress
from tempfile import mkstemp
from io import UnsupportedOperation


from typing import Any, ClassVar, Protocol, TYPE_CHECKING
if TYPE_CHECKING:
    from _typeshed import SupportsRead, SupportsWrite
    from collections.abc import Iterator
    from onegov.file.types import SigningServiceConfig

[docs] class SupportsReadAndHasName(SupportsRead[bytes], Protocol): @property
[docs] def name(self) -> str: ...
[docs] class SigningService: """ A generic interface for various file signing services. """
[docs] registry: ClassVar[dict[str, type['SigningService']]] = {}
[docs] service_name: ClassVar[str]
[docs] def __init_subclass__(cls, service_name: str, **kwargs: Any): SigningService.registry[service_name] = cls cls.service_name = service_name super().__init_subclass__(**kwargs)
@staticmethod
[docs] def for_config(config: 'SigningServiceConfig') -> 'SigningService': """ Spawns a service instance using the given config. """ return SigningService.registry[config['name']]( **config.get('parameters', {}) )
def __init__(self, **parameters: Any): """ Signing services are initialised with parameters of their chosing. Typically those parameters are read from a yaml file:: name: service_name paramters: foo: bar bar: foo This function may be overwritten by the subclass with concrete arguemnts. For example:: class MyService(SigningService, name='my_service'): def __init__(self, user, password): pass During initialisiation through onegov.file.integration (and only then), the current path is set to the path of the config file. """ self.parameters = parameters
[docs] def sign( self, infile: 'SupportsRead[bytes]', outfile: 'SupportsWrite[bytes]' ) -> str: """ Signs the input file and writes it to the given output file. Arguments ========= If the input-file exists on disk, its ``file.name`` attribute points to an existing path. Sublcasses may add extra parameters to this signing function, though it is expected that they all have a default value set. So it is okay to do this:: def sign(self, infile, outfile, foo) But it would be better to do thiss:: def sign(self, infile, outfile, foo='bar') Return Value ============ The sign function *must* return a unique request id for each signed file. This function should be composed of the service name and a unique identifier. For example: 'my_service/0b86854'. Using this identifier it should be possible to query the signing service backend for more information (in case we ever need to investigate). It is up to the signing service to know what should be part of this unique identifer. The only thing that can't be part of the identifer are secrets. """ raise NotImplementedError
@contextmanager
[docs] def materialise( self, file: 'SupportsRead[bytes]' ) -> 'Iterator[SupportsReadAndHasName]': """ Takes the given file-like object and ensures that it exists somewhere on the disk during the lifetime of the context. """ if hasattr(file, 'seek'): with suppress(UnsupportedOperation): file.seek(0) if hasattr(file, 'name') and os.path.exists(file.name): yield file # type:ignore[misc] else: fd, path = mkstemp() with open(path, 'rb+') as output: for chunk in iter(lambda: file.read(4096), b''): output.write(chunk) output.seek(0) yield output os.unlink(path)