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PKCS1-padding/RSA encryption ios objc 和 java 之间的区别

ios android java encryption rsa
2022-09-01 12:19:17

我正在为ios和Android开发一个应用程序。我对加密任务相对较新，在过去的3天里，我一直在用头撞墙，因为我无法运行RSA加密。

两个客户端都从 Java 服务器接收公钥。在android中，我有（显然，因为它与服务器端的代码几乎相同）没有麻烦，但是ios部分似乎根本不兼容。我想用公钥加密一小段数据（aes密钥），这就是我在Java中这样做的方式：

try {
    String publickey  = "MCwwDQYJKoZIhvcNAQEBBQADGwAwGAIRAK+dBpbOKw+1VKMWoFxjU6UCAwEAAQ==";
    byte[] bArr = Crypto.base64Decode(publicKey, false);
    KeyFactory keyFactory = KeyFactory.getInstance("RSA", "BC");
    EncodedKeySpec publicKeySpec = new X509EncodedKeySpec(publicKey);
    PublicKey publicKey = keyFactory.generatePublic(publicKeySpec);

    Cipher cipher = Cipher.getInstance("RSA/NONE/PKCS1Padding", "BC");
    cipher.init(1,publicKey);
    int cipherBlockSize = cipher.getBlockSize();
    ByteArrayOutputStream bArrOut = new ByteArrayOutputStream();
    bArrOut.flush();
    int pos = 0;
    Log.i("ContentBufferLength", contentBuffer.length+"");

    while (true) {
        if (cipherBlockSize > contentBuffer.length - pos) {
            cipherBlockSize = contentBuffer.length - pos;
        }
        Log.i("CipherBlockSize", cipherBlockSize+"");
        byte[] tmp = cipher.doFinal(contentBuffer, pos, cipherBlockSize);
        bArrOut.write(tmp);
        pos += cipherBlockSize;
        if (contentBuffer.length <= pos) {
            break;
        }
    }
    bArrOut.flush();
    encryptedBuffer = bArrOut.toByteArray();
    bArrOut.close();
} catch (Exception ex) {
    throw ex;
}

//  Log.i("Encrypted Buffer Length", encryptedBuffer.length+"");
return encryptedBuffer;

这是我（不能正常工作）的ios代码，从这里借来的：

http://blog.wingsofhermes.org/?p=75 和苹果加密练习。

-(NSString* )encryptWithPublicKey:(NSString*)key input:(NSString*) input {
    const size_t BUFFER_SIZE =      16;
    const size_t CIPHER_BUFFER_SIZE = 16;
   //const uint32_t PADDING = kSecPaddingNone;
    const uint32_t PADDING = kSecPaddingPKCS1;

    static const UInt8 publicKeyIdentifier[] = "de.irgendwas.app";

    NSData *publicTag;

    publicTag = [[NSData alloc] initWithBytes:publicKeyIdentifier length:sizeof(publicKeyIdentifier)];

    NSMutableDictionary *publicKey2 = [[NSMutableDictionary alloc] init];
    [publicKey2 setObject:kSecClassKey forKey:kSecClass];
    [publicKey2 setObject:kSecAttrKeyTypeRSA forKey:kSecAttrKeyType];
    [publicKey2 setObject:publicTag forKey:kSecAttrApplicationTag];
    SecItemDelete((CFDictionaryRef)publicKey2);


    NSData *strippedPublicKeyData = [NSData dataFromBase64String:key];

    unsigned char * bytes = (unsigned char *)[strippedPublicKeyData bytes];
    size_t bytesLen = [strippedPublicKeyData length];

    size_t i = 0;
    if (bytes[i++] != 0x30)
        [Exception raise:FAILURE function:__PRETTY_FUNCTION__ line:__LINE__ description:@"Could not set public key."];

    /* Skip size bytes */
    if (bytes[i] > 0x80)
        i += bytes[i] - 0x80 + 1;
    else
        i++;

    if (i >= bytesLen)
        [Exception raise:FAILURE function:__PRETTY_FUNCTION__ line:__LINE__ description:@"Could not set public key."];

    if (bytes[i] != 0x30)
        [Exception raise:FAILURE function:__PRETTY_FUNCTION__ line:__LINE__ description:@"Could not set public key."];

    /* Skip OID */
    i += 15;

    if (i >= bytesLen - 2)
        [Exception raise:FAILURE function:__PRETTY_FUNCTION__ line:__LINE__ description:@"Could not set public key."];

    if (bytes[i++] != 0x03)
        [Exception raise:FAILURE function:__PRETTY_FUNCTION__ line:__LINE__ description:@"Could not set public key."];

    /* Skip length and null */
    if (bytes[i] > 0x80)
        i += bytes[i] - 0x80 + 1;
    else
        i++;

    if (i >= bytesLen)
        [Exception raise:FAILURE function:__PRETTY_FUNCTION__ line:__LINE__ description:@"Could not set public key."];

    if (bytes[i++] != 0x00)
        [Exception raise:FAILURE function:__PRETTY_FUNCTION__ line:__LINE__ description:@"Could not set public key."];

    if (i >= bytesLen)
        [Exception raise:FAILURE function:__PRETTY_FUNCTION__ line:__LINE__ description:@"Could not set public key."];

    strippedPublicKeyData = [NSData dataWithBytes:&bytes[i] length:bytesLen - i];

    DLog(@"X.509 Formatted Public Key bytes:\n%@",[strippedPublicKeyData description]);

    if (strippedPublicKeyData == nil)
        [Exception raise:FAILURE function:__PRETTY_FUNCTION__ line:__LINE__ description:@"Could not set public key."];



    CFTypeRef persistKey = nil;
    [publicKey2 setObject:strippedPublicKeyData forKey:kSecValueData];
    [publicKey2 setObject: (kSecAttrKeyClassPublic) forKey:kSecAttrKeyClass];
    [publicKey2 setObject:[NSNumber numberWithBool:YES] forKey:kSecReturnPersistentRef];

    OSStatus secStatus = SecItemAdd((CFDictionaryRef)publicKey2, &persistKey);

    if (persistKey != nil) CFRelease(persistKey);

    if ((secStatus != noErr) && (secStatus != errSecDuplicateItem))
        [Exception raise:FAILURE function:__PRETTY_FUNCTION__ line:__LINE__ description:@"Could not set public key."];

    SecKeyRef keyRef = nil;
    [publicKey2 removeObjectForKey:kSecValueData];
    [publicKey2 removeObjectForKey:kSecReturnPersistentRef];
    [publicKey2 setObject:[NSNumber numberWithBool:YES] forKey:kSecReturnRef];
    [publicKey2 setObject: kSecAttrKeyTypeRSA forKey:kSecAttrKeyType];

    SecItemCopyMatching((CFDictionaryRef)publicKey2,(CFTypeRef *)&keyRef);
    if (!keyRef)
    [Exception raise:FAILURE function:__PRETTY_FUNCTION__ line:__LINE__ description:@"Could not set public key."];  

    uint8_t *plainBuffer;
    uint8_t *cipherBuffer;
    uint8_t *decryptedBuffer;


    const char inputString[] = "1234";
    int len = strlen(inputString);
    // TODO: this is a hack since i know inputString length will be less than BUFFER_SIZE
    if (len > BUFFER_SIZE) len = BUFFER_SIZE-1;
    plainBuffer = (uint8_t *)calloc(BUFFER_SIZE, sizeof(uint8_t));
    cipherBuffer = (uint8_t *)calloc(CIPHER_BUFFER_SIZE, sizeof(uint8_t));
    decryptedBuffer = (uint8_t *)calloc(BUFFER_SIZE, sizeof(uint8_t));

    strncpy( (char *)plainBuffer, inputString, len);

    size_t plainBufferSize = strlen((char *)plainBuffer);
    size_t cipherBufferSize = CIPHER_BUFFER_SIZE;

    NSLog(@"SecKeyGetBlockSize() public = %lu", SecKeyGetBlockSize(keyRef));
    //  Error handling
    // Encrypt using the public.
    OSStatus status = noErr;

    status = SecKeyEncrypt(keyRef,
                           PADDING,
                           plainBuffer,
                           plainBufferSize,
                           &cipherBuffer[0],
                           &cipherBufferSize
                           );
    NSLog(@"encryption result code: %ld (size: %lu)", status, cipherBufferSize);

    return [[[NSString stringWithFormat:@"%s",cipherBuffer] dataUsingEncoding:NSUTF8StringEncoding] base64EncodedString];
}

为了测试目的和简单起见，目前我正在尝试仅加密长度为4字节的输入。这应该足够小以适合一个块。公钥导入和加密过程似乎有效，但是与Android方法相比，我总是收到更长的输出。

到目前为止，我遇到的唯一区别是，在java cipher.blocksize中返回5。我认为其他11个字节是为pkcs1填充保留的，但是如何强制相同的行为？SecKeyGetBlockSize returns 16ios/objc


答案 1

尝试将密文拆分为多个部分，以便每个部分包含16个字符长并单独解码它们。我也遇到了同样的问题，但这在PHP中很长一段时间了，上面的技巧对我有用。

这可能有助于您解决问题。


答案 2

解码 Base64 键可得到：

MCwwDQYJKoZIhvcNAQEBBQADGwAwGAIRAK+dBpbOKw+1VKMWoFxjU6UCAwEAAQ==
-> 302c300d06092a864886f70d0101010500031b003018021100af9d0696ce2b0fb554a316a05c6353a50203010001

将其解释为DER编码的ASN.1，我们发现：

30(2c) //SEQUENCE
  30(0d)  //SEQUENCE
    06(09): 2a 86 48 86 f7 0d 01 01 01  //OID 1.2.840.113548.1.1.1 (RSA Encryption)
    05(00): //NULL                           
    03(1b): [00] 30 18 02 11 00 af 9d 06 96 ce 2b 0f b5 54 a3 16 a0 5c 63 53 a5 02 03 01 00 01 //BITSTRING

其中 BITSTRING 似乎还包含 DER 编码的 ASN.1：

30(18) //SEQUENCE
  02(11): 00 af 9d 06 96 ce 2b 0f b5 54 a3 16 a0 5c 63 53 a5 02 03 01 00 01 //INTEGER

 = 0xaf9d0696ce2b0fb554a316a05c6353a50203010001

浏览 IOS 代码，您可以看到它正在解析 DER 编码的 ASN.1。它正确标识前两个 SEQUENCE 标记，并跳过 OID 字段，甚至无需验证它是否为 OID。然后问题发生了：IOS代码期望下一个标签是BITSTRING（0x03）---但是在我们的数据中，我们有一个额外的NULL（0x05）字段来表示公共指数是隐式的。IOS 代码在遇到0x05 标记时引发异常。如果 NULL 不存在，我们看到 IOS 代码将成功提取 BITSTRING 的内容。

因此：NULL 是可选字段，IOS 代码不允许这样做，或者 IOS 代码需要不同的 ASN.1 结构。例如，似乎BITSTRING也是DER编码的ASN.1 INTEGER（可能是RSA模量）。然而，IOS代码没有尝试解析它。可能是IOS例程期望这种格式的模数，或者可能是调用方应该提取模数的原始字节。SecKeyEncrypt

所以仍然需要一点点实验。但是，如果此代码要分析提供的数据对象，则以下附加条件是绝对必要的：

/* Skip OID */
i += 15;

if (i >= bytesLen - 2)
    [Exception raise:FAILURE function:__PRETTY_FUNCTION__ line:__LINE__ description:@"Could not set public key."];

if (bytes[i] == 0x05)    /* This should handle the spurious ASN.1 NULL field */
    i += 2;

if (bytes[i++] != 0x03)

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