python 扭曲的信誉使用

Question

当我浏览 twisted 的例子（写得很好）时，我对 twisted for ex 有一个小疑问，我看到了一个使用 cred 的例子。我不得不提到这种好奇心是因为我使用 twisted 的次数越多，我就越喜欢它并试图围绕它并详细了解它的功能。现在我的问题是 为什么首先要使用 cred？如果它是为了简单的用户传递凭据，那么不能像在大多数 Web 应用程序中那样使用对数据库的简单检查吗？ 如果它是为了制作异步，那么不能使用异步版本的数据库客户端来实现相同的目的吗？什么使用 relam 、 avatars 和 portals 有什么好处？我的意思是在什么情况下可以使用这些东西。我知道这与我对扭曲信誉的理解有关，所以请帮忙。下面是我说的前男友

from __future__ import print_function

import sys
from zope.interface import implementer, Interface

from twisted.protocols import basic
from twisted.internet import protocol
from twisted.python import log

from twisted.cred import error
from twisted.cred import portal
from twisted.cred import checkers
from twisted.cred import credentials

class IProtocolUser(Interface):
    def getPrivileges():
        """Return a list of privileges this user has."""

    def logout():
        """Cleanup per-login resources allocated to this avatar"""

@implementer(IProtocolUser)
class AnonymousUser:
    def getPrivileges(self):
        return [1, 2, 3]

    def logout(self):
        print("Cleaning up anonymous user resources")

@implementer(IProtocolUser)
class RegularUser:
    def getPrivileges(self):
        return [1, 2, 3, 5, 6]

    def logout(self):
        print("Cleaning up regular user resources")

@implementer(IProtocolUser)
class Administrator:
    def getPrivileges(self):
        return range(50)

    def logout(self):
        print("Cleaning up administrator resources")

class Protocol(basic.LineReceiver):
    user = None
    portal = None
    avatar = None
    logout = None

    def connectionMade(self):
        self.sendLine("Login with USER <name> followed by PASS <password> or ANON")
        self.sendLine("Check privileges with PRIVS")

    def connectionLost(self, reason):
        if self.logout:
            self.logout()
            self.avatar = None
            self.logout = None

    def lineReceived(self, line):
        f = getattr(self, 'cmd_' + line.upper().split()[0])
        if f:
            try:
                f(*line.split()[1:])
            except TypeError:
                self.sendLine("Wrong number of arguments.")
            except:
                self.sendLine("Server error (probably your fault)")

    def cmd_ANON(self):
        if self.portal:
            self.portal.login(credentials.Anonymous(), None, IProtocolUser
                ).addCallbacks(self._cbLogin, self._ebLogin
                )
        else:
            self.sendLine("DENIED")

    def cmd_USER(self, name):
        self.user = name
        self.sendLine("Alright.  Now PASS?")

    def cmd_PASS(self, password):
        if not self.user:
            self.sendLine("USER required before PASS")
        else:
            if self.portal:
                self.portal.login(
                    credentials.UsernamePassword(self.user, password),
                    None,
                    IProtocolUser
                ).addCallbacks(self._cbLogin, self._ebLogin
                )
            else:
                self.sendLine("DENIED")

    def cmd_PRIVS(self):
        self.sendLine("You have the following privileges: ")
        self.sendLine(" ".join(map(str, self.avatar.getPrivileges())))

    def _cbLogin(self, result):
        (interface, avatar, logout) = result
        assert interface is IProtocolUser
        self.avatar = avatar
        self.logout = logout
        self.sendLine("Login successful.  Available commands: PRIVS")

    def _ebLogin(self, failure):
        failure.trap(error.UnauthorizedLogin)
        self.sendLine("Login denied!  Go away.")

class ServerFactory(protocol.ServerFactory):
    protocol = Protocol

    def __init__(self, portal):
        self.portal = portal

    def buildProtocol(self, addr):
        p = protocol.ServerFactory.buildProtocol(self, addr)
        p.portal = self.portal
        return p

@implementer(portal.IRealm)
class Realm:
    def requestAvatar(self, avatarId, mind, *interfaces):
        if IProtocolUser in interfaces:
            if avatarId == checkers.ANONYMOUS:
                av = AnonymousUser()
            elif avatarId.isupper():
                # Capitalized usernames are administrators.
                av = Administrator()
            else:
                av = RegularUser()
            return IProtocolUser, av, av.logout
        raise NotImplementedError("Only IProtocolUser interface is supported by this realm")

def main():
    r = Realm()
    p = portal.Portal(r)
    c = checkers.InMemoryUsernamePasswordDatabaseDontUse()
    c.addUser("auser", "thepass")
    c.addUser("SECONDUSER", "secret")
    p.registerChecker(c)
    p.registerChecker(checkers.AllowAnonymousAccess())

    f = ServerFactory(p)

    log.startLogging(sys.stdout)

    from twisted.internet import reactor
    reactor.listenTCP(4738, f)
    reactor.run()

if __name__ == '__main__':
    main()

Answer 1

twisted.cred 提供了一个抽象，它允许您的应用程序独立于验证某些凭据的特定方法进行开发，并允许您的凭据数据库独立于您的应用程序进行开发。

在您的示例中，请注意您的应用程序代码 (Protocol) 如何不知道凭据纯粹存储在内存中这一事实。如果您将 InMemoryUsernamePasswordDatabaseDontUse 替换为 PAM 后端、/etc-passwd 风格的数据库或使用 PostgreSQL 的东西，它同样不会意识到。

此外，这些 username/password 后端都可以独立于您的应用程序逻辑进行开发 - 允许您的每个应用程序重复使用它们，无论它们是您的作品还是其他人与您共享的作品。

python 扭曲的信誉使用

python twisted cred use

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twisted