使用Python中的Security.framework类型

Question

我正在编写一个Python，它通过ctype从OS上调用Security.framework函数。

我能够用Python创建一个CFDictionaryRef和CFStringRef，并将字符串存储在字典中，但现在我正在添加Security.framework查询对象(kSecClass、kSecMatchLimit、kSecReturnAttributes、…)我得到了以下坠机：

objc[28201]: Method cache corrupted. This may be a message to an invalid object, or a memory error somewhere else.
objc[28201]: receiver 0x7fff724fcdf8, SEL 0x7fff8d814fe5, isa 0x7fff724f5f90, cache 0x7fff724f5fa0, buckets 0x7fff8842ffe3, mask 0x5, occupied 0x0, wrap bucket 0x7fff8842ffe3
objc[28201]: receiver 0 bytes, buckets 0 bytes
objc[28201]: selector 'hash'
objc[28201]: isa '(null)'
objc[28201]: Method cache corrupted.
zsh: illegal hardware instruction  python kc.py

我尝试使用包含对象的ctype数组调用CFDictionaryCreate()，并调用CFMutableDictionaryCreate()然后CFDictionarySetValue。见下文。

import ctypes
import ctypes.util
from ctypes import CFUNCTYPE

security = ctypes.CDLL(ctypes.util.find_library('Security'))
foundation = ctypes.CDLL(ctypes.util.find_library('Foundation'))

CFDictionaryRef = ctypes.c_void_p
CFMutableDictionaryRef = ctypes.c_void_p
CFTypeRef = ctypes.c_void_p
CFIndex = ctypes.c_long

CFDictionaryCreate = CFUNCTYPE(CFDictionaryRef, ctypes.c_void_p, ctypes.c_void_p, ctypes.c_void_p, CFIndex, ctypes.c_void_p, ctypes.c_void_p)(('CFDictionaryCreate', foundation))
CFDictionaryCreateMutable = CFUNCTYPE(CFMutableDictionaryRef, CFIndex, ctypes.c_void_p, ctypes.c_void_p)(('CFDictionaryCreateMutable', foundation))
CFDictionarySetValue = CFUNCTYPE(CFMutableDictionaryRef, ctypes.c_void_p, ctypes.c_void_p)(('CFDictionarySetValue', foundation))

def createCFDictionary(items):
    """
    Create a CFDictionaryRef from items = [(CFTypeRef, CFTypeRef), ...]
    """
    # Create C arrays for the keys and values (which are cast as CFTypeRefs).
    keys_array = (CFTypeRef * len(items))(*[ctypes.cast(k, CFTypeRef) for k, v in items])
    values_array = (CFTypeRef * len(items))(*[ctypes.cast(v, CFTypeRef) for k, v in items])

    return CFDictionaryCreate(None,
                              keys_array, values_array, len(items),
                              foundation.kCFTypeDictionaryKeyCallBacks, foundation.kCFTypeDictionaryValueCallBacks)

# 1. Create a CFDictionary with the items in it (crashes).
query = createCFDictionary([(security.kSecClass, security.kSecClassCertificate)])


# 2a. Create a CFMutableDictionary.
query = CFDictionaryCreateMutable(0, foundation.kCFTypeDictionaryKeyCallBacks, foundation.kCFTypeDictionaryValueCallBacks)

# 2b. Add items to it (crashes).
CFDictionarySetValue(query, security.kSecClass, security.kSecClassCertificate)

如果这是一种更简单的解决方案，我很乐意使用PyObjC而不是ctype；然而，我对它不太熟悉，也无法导入Security.framework。

OS 10.9.2，Python2.7.5(随OS一起包括)。

Answer 1

我正在调查第二个案例，因为它看起来更简单。

您的CFDictionarySetValue缺少了dict参数。修复后，security.kSecClass似乎实际上返回了一个函数引用，这是错误的。我认为你需要：

ctypes.c_void_p.in_dll(foundation, 'kSecClass')

这将导致将正确的值传递给函数(如lldb中所示)。

不知何故，kCFTypeDictionaryKeyCallBacks结构仍然无法使用该机制，这可能是因为符号实际上指向的是结构，而不是指向结构的指针。我想不出任何方法让ctype返回符号所代表的实际地址(这就是您想传递给CFDictionaryCreateMutable的地址)，而不是那个符号的值( 0，因为这是该结构的第一个成员的值)。

您可以自己构造回调，这应该更容易一些，因为您可以在ctype中定义struct类型，然后获取所需的函数。