ios - SecItemCopyMatching はエラーなしで nil 値を返します

Question

CryptoExercise の SecKeyWrapperaddPeerPublicKey:keyBits:メソッドを使用して、RSA 公開鍵を iPhone のキーチェーンに追加しようとしています。このメソッドのロジックは、最初にキーをキーチェーンに追加しようとし、既にそこにある(sanityCheck==errSecDuplicateItem)場合は、を呼び出してキーチェーンからこのキーを取得しようとすることSecKeyItemCopyMatching()です。

それはまさに私の場合に起こることです: キーはすでにキーチェーンにあるので、SecKeyItemAdd() returns errSecDuplicateItem.

次に、既存のキーを取得しようとしますがSecKeyItemCopyMatching() returns 0(エラーがなかったことを示します)、2 番目のパラメーター ( peerKeyRef) は必死に nil のままです。

これはどのように可能ですか？これの何が問題なのですか？

[SecKeyWrapper addPeerPublicKey:keyBits:]参考までに、CryptoExercise サンプルのコードを次に示します。

- (SecKeyRef)addPeerPublicKey:(NSString *)peerName keyBits:(NSData *)publicKey {
    OSStatus sanityCheck = noErr;
    SecKeyRef peerKeyRef = NULL;
    CFTypeRef persistPeer = NULL;

    LOGGING_FACILITY( peerName != nil, @"Peer name parameter is nil." );
    LOGGING_FACILITY( publicKey != nil, @"Public key parameter is nil." );

    NSData *peerTag = [[NSData alloc] initWithBytes:(const void *) [peerName UTF8String] length:[peerName length]];
    NSMutableDictionary *peerPublicKeyAttr = [[NSMutableDictionary alloc] init];

    [peerPublicKeyAttr setObject:(__bridge id) kSecClassKey forKey:(__bridge id) kSecClass];
    [peerPublicKeyAttr setObject:(__bridge id) kSecAttrKeyTypeRSA forKey:(__bridge id) kSecAttrKeyType];
    [peerPublicKeyAttr setObject:peerTag forKey:(__bridge id) kSecAttrApplicationTag];
    [peerPublicKeyAttr setObject:publicKey forKey:(__bridge id) kSecValueData];
    [peerPublicKeyAttr setObject:[NSNumber numberWithBool:YES] forKey:(__bridge id) kSecReturnPersistentRef];

    sanityCheck = SecItemAdd((__bridge CFDictionaryRef) peerPublicKeyAttr, (CFTypeRef *) &persistPeer);

    // The nice thing about persistent references is that you can write their value out to disk and
    // then use them later. I don't do that here but it certainly can make sense for other situations
    // where you don't want to have to keep building up dictionaries of attributes to get a reference.
    //
    // Also take a look at SecKeyWrapper's methods (CFTypeRef)getPersistentKeyRefWithKeyRef:(SecKeyRef)key
    // & (SecKeyRef)getKeyRefWithPersistentKeyRef:(CFTypeRef)persistentRef.

    LOGGING_FACILITY1( sanityCheck == noErr || sanityCheck == errSecDuplicateItem, @"Problem adding the peer public key to the keychain, OSStatus == %ld.", sanityCheck );

    if (persistPeer) {
        peerKeyRef = [self getKeyRefWithPersistentKeyRef:persistPeer];
    } else {
        [peerPublicKeyAttr removeObjectForKey:(__bridge id) kSecValueData];
        [peerPublicKeyAttr setObject:[NSNumber numberWithBool:YES] forKey:(__bridge id) kSecReturnRef];
        // Let's retry a different way.
        sanityCheck = SecItemCopyMatching((__bridge CFDictionaryRef) peerPublicKeyAttr, (CFTypeRef *) &peerKeyRef);
    }

    LOGGING_FACILITY1( sanityCheck == noErr && peerKeyRef != NULL, @"Problem acquiring reference to the public key, OSStatus == %ld.", sanityCheck );

    if (persistPeer) CFRelease(persistPeer);
    return peerKeyRef;
}