ios - 使用 SecKeyEncrypt 的 RSA 加密给出错误 -4 (errSecUnimplemented)

Question

我正在尝试使用 iOS 上的安全框架使用 RSA 加密一些数据。我想加密一个简单的 base64 编码字符串，如下所示:

NSData *data = [[NSData alloc] initWithBase64EncodedString:@"aGFsbG8=" options:0x0];
NSData *encrypted = [pair encrypt:data];

pair 变量包含对在使用 SecKeyGeneratePair 之前成功生成的私钥和公钥的引用。

加密函数如下所示:

- (NSData *)encrypt:(NSData *)data {
    void *buffer = malloc([self blockSize] * sizeof(uint8_t));
    memset(buffer, 0x0, [self blockSize]);
    size_t ciphertextBufferLength = [data length];
    OSStatus res = SecKeyEncrypt([self keyRef], 0x1, [data bytes], [data length], &buffer[0], &ciphertextBufferLength);
    NSLog(@"Result of encryption: %d", res);
    return [NSData dataWithBytesNoCopy:buffer length:[self blockSize] freeWhenDone:YES];
}

[self blockSize] 的实现相当简单:

- (unsigned long)blockSize {
    return SecKeyGetBlockSize(keyRef);
}

我使用以下函数生成我的 key :

- (BOOL)generateNewKeyPairOfSize:(unsigned int)keySize
{
    SecKeyRef privKey = [[self publicKey] keyRef];
    SecKeyRef pubKey = [[self publicKey] keyRef];

    NSDictionary *privateKeyDict = @{ (__bridge id)kSecAttrIsPermanent : @(YES), (__bridge id)kSecAttrApplicationTag : [[self privateKey] tag] };
    NSDictionary *publicKeyDict = @{ (__bridge id)kSecAttrIsPermanent : @(YES), (__bridge id)kSecAttrApplicationTag : [[self publicKey] tag] };
    NSDictionary *keyDict = @{ (__bridge id)kSecAttrKeyType : (__bridge id)kSecAttrKeyTypeRSA, (__bridge id)kSecAttrKeySizeInBits : @(keySize), (__bridge id)kSecPublicKeyAttrs : publicKeyDict, (__bridge id)kSecPrivateKeyAttrs : privateKeyDict };
    OSStatus res = SecKeyGeneratePair((__bridge CFDictionaryRef)keyDict, &privKey, &pubKey);
    NSLog(@"Result of generating keys: %d", res);

    [[self publicKey] setKeyRef:pubKey];
    [[self privateKey] setKeyRef:privKey];

    return YES;
}

问题是res的值是-4，根据文档意思是errSecUnimplemented。我不确定我在这里做错了什么，因为我需要所有参数。我不确定参数是否有错误以及在哪里。调用 [self blockSize] 返回 128。

谁能帮我解决这个问题？

Answer 1

来自文档:

cipherTextLen - On entry, the size of the buffer provided in the cipherText parameter. On return, the amount of data actually placed in the buffer.

您没有为 ciphertextBufferLength 设置任何值。

更新 #1

在 SecKeyGeneratePair() 中你有错误的参数:公钥参数必须是第一个，私钥是第二个。我认为这就是您出现错误代码 -4 的原因。

更新 #2

当您修复更新 #1 中的问题时，您将看到错误代码 -50 (errSecParam)，因为您的密文长度错误。这是正确的加密/解密的样子:

[self generateNewKeyPairOfSize:1024];

NSData *data = [[NSData alloc] initWithBase64EncodedString:@"aGFsbG8=" options:0x0];

size_t cipherTextSize = [self blockSize];
uint8_t *cipherText = malloc(cipherTextSize);
memset(cipherText, 0, cipherTextSize);
OSStatus res = SecKeyEncrypt(_publicKey, kSecPaddingPKCS1, [data bytes], data.length, cipherText, &cipherTextSize);
NSLog(@"Result of encryption: %d", res);

size_t plainTextSize = cipherTextSize;
uint8_t *plainText = malloc(plainTextSize);
res = SecKeyDecrypt(_privateKey, kSecPaddingPKCS1, cipherText, cipherTextSize, plainText, &plainTextSize);
NSLog(@"Result of decryption: %d", res);