使用ARC的安全框架内存泄漏

Question

打开ASIHTTPRequest的p12证书时遇到内存泄漏。这是获取证书的代码：

- (SecIdentityRef)getClientCertificate {
    SecIdentityRef identityApp = nil;
    NSString *thePath = [[NSBundle mainBundle] pathForResource:@"myCert" ofType:@"p12"];
    NSData *PKCS12Data = [[NSData alloc] initWithContentsOfFile:thePath];
    CFDataRef inPKCS12Data = (__bridge CFDataRef)PKCS12Data;
    CFStringRef password = CFSTR("myPassword");
    const void *keys[] = { kSecImportExportPassphrase };
    const void *values[] = { password };
    CFDictionaryRef options = CFDictionaryCreate(NULL, keys, values, 1, NULL, NULL);
    CFArrayRef items = CFArrayCreate(NULL, 0, 0, NULL);
    OSStatus securityError = SecPKCS12Import(inPKCS12Data, options, &items);
    CFRelease(options);
    CFRelease(password);
    if (securityError == errSecSuccess) {
        NSLog(@"Success opening p12 certificate. Items: %ld", CFArrayGetCount(items));
        CFDictionaryRef identityDict = CFArrayGetValueAtIndex(items, 0);
        identityApp = (SecIdentityRef)CFDictionaryGetValue(identityDict, kSecImportItemIdentity);        
    } else {
        NSLog(@"Error opening Certificate.");
    }
    return identityApp;
}

正如您在此处看到的，它会产生内存泄漏：

或者，这个其他函数（基本相同）会产生其他类型的内存泄漏：

- (SecIdentityRef)getClientCertificate2 {
    SecIdentityRef identityApp = nil;
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *thePath = [documentsDirectory stringByAppendingPathComponent:@"myothercert.p12"];

    NSData *PKCS12Data = [[NSData alloc] initWithContentsOfFile:thePath];
    NSLog(@"PKCS12Data length is %i", [PKCS12Data length]);
    CFDataRef inPKCS12Data = (__bridge CFDataRef)PKCS12Data;

    CFStringRef password = CFSTR("randomgenerated");
    const void *keys[] = { kSecImportExportPassphrase };
    const void *values[] = { password };
    CFDictionaryRef options = CFDictionaryCreate(NULL, keys, values, 1, NULL, NULL);
    CFArrayRef items = CFArrayCreate(NULL, 0, 0, NULL);
    OSStatus securityError = SecPKCS12Import(inPKCS12Data, options, &items);
     CFRelease(options);
    //CFRelease(password);
    if (securityError == errSecSuccess) {
        NSLog(@"Success opening p12 certificate. Items: %ld", CFArrayGetCount(items));
        CFDictionaryRef identityDict = CFArrayGetValueAtIndex(items, 0);
        identityApp = (SecIdentityRef)CFDictionaryGetValue(identityDict, kSecImportItemIdentity);
    } else {
        NSLog(@"Error opening Certificate.");
    }
    return identityApp;
}

产生这些内存泄漏：

导致这些内存泄漏的是什么？该代码适用于打开p12文件，但我需要修复内存泄漏。任何帮助表示赞赏。

谢谢！

  

修改

根据建议的更改，我仍然会收到内存泄漏：

- (SecIdentityRef)copyClientCertificate2 {
SecIdentityRef identityApp = nil;
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *thePath = [documentsDirectory stringByAppendingPathComponent:@"cert.p12"];

NSData *PKCS12Data = [[NSData alloc] initWithContentsOfFile:thePath];
NSLog(@"PKCS12Data length is %i", [PKCS12Data length]);


CFStringRef password = CFSTR("randomgenerated");
const void *keys[] = { kSecImportExportPassphrase };
const void *values[] = { password };
CFDictionaryRef options = CFDictionaryCreate(NULL, keys, values, 1, NULL, NULL);
CFArrayRef items = NULL;
OSStatus securityError = SecPKCS12Import((__bridge CFDataRef)PKCS12Data, options, &items);
 CFRelease(options);
//CFRelease(password);
if (securityError == errSecSuccess) {
    NSLog(@"Success opening p12 certificate. Items: %ld", CFArrayGetCount(items));
    CFDictionaryRef identityDict = CFArrayGetValueAtIndex(items, 0);
    identityApp = (SecIdentityRef)CFDictionaryGetValue(identityDict, kSecImportItemIdentity);
} else {
    NSLog(@"Error opening Certificate.");
}
CFRetain(identityApp);
return identityApp;

}

Answer 1

你正在泄漏items。你创建它但从不发布它。你不应该首先创建它。 SecPKCS12Import通过引用返回items。你没有把它传给现有的;它通过你一个。这应该是：

CFArrayRef items = NULL;

您还需要在CFRetain()上调用identityApp来保留它（因为它目前仅由数组保留。因此，您的方法需要调用copyClientCertificate2并且您完成后需要CFRelease()结果。

附注：除非通过引用返回结果，否则不要在方法前加上“get”。这就是ObjC中的“获取”意味着什么。例如：

- (BOOL)getName:(NSString **)name;

这里有另一个非常危险的代码：

NSData *PKCS12Data = [[NSData alloc] initWithContentsOfFile:thePath]; // (1)
CFDataRef inPKCS12Data = (__bridge CFDataRef)PKCS12Data;              // (2)
...
OSStatus securityError = SecPKCS12Import(inPKCS12Data, options, &items); // (3)

ARC可以在第（2）行后立即释放PKCS12Data。如果你在发布模式下构建它，我会期望它崩溃。这里正确的解决方案是摆脱inPKCS12Data，并在第（3）行执行__bridge演员。

---

编辑：

如果您正在进行此类工作，了解如何管理Core Foundation对象非常重要。首先，研究下面链接的创建规则。然后，调用方法copy…的目的是指示调用者负责在返回的对象上调用CFRelease。它看起来像这样：

SecIdentityRef identity = [self copyClientCertificate2];
... Do what you need to do with identity ....
CFRelease(identity);

由于您从未在self中使用copyClientCertificate2，因此将其设为函数可能更有意义，因此它看起来像其他Core Foundation函数：

SecIdentityRef identity = MYSecIdentityCopyClientCertificate();
... Do what you need to do with identity ....
CFRelease(identity);

请注意函数名称中的单词Copy。