objective-c - SecKeychainGetPath 错误

Question

有时，在尝试获取 SecKeychainCopySearchList 返回的钥匙串(keychain)的路径时，我会收到代码 -25301 的错误，错误列表中的代码代表 errSecBufferTooSmall。 SecCopyErrorMessageString 声明:

There is not enough memory available to use the specified item.

奇怪的是，它并不总是在同一个钥匙串(keychain)引用上返回错误。

以下是我尝试获取钥匙串(keychain)路径的方法:

- (NSString *)getKeychainPath:(SecKeychainRef)keychain {
    char *pathName = malloc(sizeof(*pathName) * 1024);
    UInt32 pathLength;
    OSStatus errCode = SecKeychainGetPath(keychain, &pathLength, pathName);
    if (errCode != errSecSuccess) {
        NSString *errString = (NSString *)SecCopyErrorMessageString(errCode, NULL);
        DLog(@"%d: %@", errCode, errString);
    }
    NSData *d = [NSData dataWithBytes:pathName length:pathLength];
    return [[[NSString alloc] initWithData:d encoding:NSUTF8StringEncoding] autorelease];
}

我对函数使用什么缓冲区感兴趣？我试过输出 pathLength 变量，但它低于 1K 字节。我究竟做错了什么？我应该怎么做才能避免这些错误？是否可以通过任何方式绕过它们？

Answer 1

来自SecKeychainGetPath documentation :

ioPathLength

On entry, a pointer to a variable containing the length (in bytes) of the buffer specified by pathName.
On return, the string length of pathName, not including the null termination.

您没有执行“输入时”部分。您需要将 pathLength 初始化为 pathName 缓冲区的大小。例如:

UInt32 pathLength = 1024;
char *pathName = malloc(pathLength);