Question

我正在尝试从VB.NET重新创建PasswordDeriveBytes的实现，到目前为止，我已经在iOS Objective C代码中实现了它，它给了我不同的Java实现结果。

我们尝试重新创建PasswordDeriveBytes的原因是因为客户端服务器端正在使用它来加密/解密数据，而且从我搜索的内容来看，PasswordDeriveBytes使用过时的PBKDF1。 Java实现返回预期的加密值，并由服务器成功解密。但是，从iOS ObjC实现返回的值不正确。

以下是构造函数的Java实现，取自此答案：Encryption Diff Between Java and C#

public static class PasswordDeriveBytes{

private final MessageDigest hash;

private final byte[] firstToLastDigest;
private final byte[] outputBuffer;

private int position = 0;

public PasswordDeriveBytes(String password, byte[] salt, int iterations) {
    try {
        this.hash = MessageDigest.getInstance("SHA-1");

        this.hash.update(password.getBytes("UTF-8"));
        this.hash.update(salt);
        this.firstToLastDigest = this.hash.digest();
        // At this point, the Obj-C and Java values are the same
        // this.firstToLastDigest = b8fa3d36....

        for (int i = 1; i < iterations - 1; i++) {
            System.out.println( "  Iterate " + i);
            hash.update(firstToLastDigest);
            hash.digest(firstToLastDigest, 0, firstToLastDigest.length);
        }

        this.outputBuffer = hash.digest(firstToLastDigest);
        // However at this point, they become different
        // Java has outputBuffer = f498e100...
        // Obj-C has outputBuffer = <d7d5fa71...

    } catch (UnsupportedEncodingException|NoSuchAlgorithmException | DigestException e) {
        throw new IllegalStateException("SHA-1 digest should always be available", e);
    }
}

虽然以下是构造函数的Objective C代码，但使用此库：https://github.com/TakahikoKawasaki/nv-ios-digest

@implementation PasswordDeriveBytesObjC
{
    SHA1 *hash;
    Byte *firstToLastDigest;
    Byte *outputBuffer;

    int position;
}

- (instancetype)initWithPassword:(NSString *)password salt:(NSData *)salt iterations:(int)iterations
{
    self = [[[self class] alloc] init];
    if (self){
        hash = [[SHA1 alloc] init];

        const char* ASCIIpassword = [password cStringUsingEncoding:NSUTF8StringEncoding];
        NSData *passwordData = [NSData dataWithBytes:ASCIIpassword length:strlen(ASCIIpassword)];

        [hash updateWith:[passwordData bytes] length:(CC_LONG)[passwordData length]];
        [hash updateWith:[salt bytes] length:(CC_LONG)[salt length]];
        firstToLastDigest = [hash final];
        // At this point, the Obj-C and Java values are the same
        // firstToLastDigest = <b8fa3d36....

        for ( int i = 1; i < iterations - 1; i++ ){
            [hash updateWith:firstToLastDigest length:(CC_LONG)strlen(firstToLastDigest)];
        }

        [hash updateWith:firstToLastDigest length:(CC_LONG)strlen(firstToLastDigest)];
        outputBuffer = [hash final];  
        // However at this point, they become different
        // Java has outputBuffer = f498e100...
        // Obj-C has outputBuffer = <d7d5fa71...

    }
    return self;
}

据我所研究，java的hash.digest(input)的实现与Obj-C中的[hash updateWith:firstToLastDigest length:(CC_LONG)strlen(firstToLastDigest)]; outputBuffer = [hash final];相同，但我得到的结果不同。

在这一点上，我没有其他想法，为什么他们得到不同的价值观，所以欢迎任何形式的指导或建议。

Answer 1

在撕掉我的头发4天后回答我自己的问题。

似乎CommonCrypto的CC_SHA1_Final（）没有重置CC_SHA1_CTX对象上下文，尽管苹果文档声明它确实存在，这会导致输出的差异。

来自Apple文档：https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man3/CC_SHA1_Final.3cc.html

CC_SHA1_Final（）将消息摘要放在md中，其中必须有空格用于CC_SHA1_DIGEST_LENGTH == 20        输出字节，并擦除CC_SHA1_CTX。

我必须编辑nv-ios-digest库并在每个CC_SHA1_CTX方法中手动重置- (unsigned char *)final对象，如下所示：

- (unsigned char *)final
{
    CC_SHA1_Final(_digest, &_context);  // <-- _context does not reset
    CC_SHA1_Init(&_context);  // <-- manually reset the CC_SHA1_CTX object

    _description = [NSString stringWithFormat:
                    @"%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x",
                    _digest[ 0], _digest[ 1], _digest[ 2], _digest[ 3],
                    _digest[ 4], _digest[ 5], _digest[ 6], _digest[ 7],
                    _digest[ 8], _digest[ 9], _digest[10], _digest[11],
                    _digest[12], _digest[13], _digest[14], _digest[15],
                    _digest[16], _digest[17], _digest[18], _digest[19]];

    return _digest;
}

希望这有助于某人。：）

SHA1 MessageDigest和CommonCrypto更新获得不同的结果

1 个答案: