验证RSA签名iOS [英] Verifying RSA Signature iOS

问题描述

在我的静态库我有一个许可证文件。我想确保是由自己生成的（并没有被改变）。所以想法是使用从我已经阅读的RSA签名。

In my static Library I have a licence file. Which I want to make sure has been generated by myself (and has not been altered). So the idea was to use an RSA Signature from what I've read.

我看过互联网，这是我想出的：

I've looked on the internet and this is what I came up with:

私钥和自签名证书与我在此处找到的信息。

First: Generating the private keys and self signed certificates with the information I found here.

// Generate private key
openssl genrsa -out private_key.pem 2048 -sha256

// Generate certificate request
openssl req -new -key private_key.pem -out certificate_request.pem -sha256

// Generate public certificate
openssl x509 -req -days 2000 -in certificate_request.pem -signkey private_key.pem -out certificate.pem -sha256

// Convert it to cer format so iOS kan work with it
openssl x509 -outform der -in certificate.pem -out certificate.cer -sha256

之后，我创建一个许可证文件（日期和应用程序标识符作为内容），并为该文件生成签名基于此处找到的信息：

After that, I create a licence file (with a date and app identifier as contents) and generate a signature for that file like so based on the information found here:

// Store the sha256 of the licence in a file
openssl dgst -sha256 licence.txt > hash

// And generate a signature file for that hash with the private key generated earlier
openssl rsautl -sign -inkey private_key.pem -keyform PEM -in hash > signature.sig

我认为一切都很好。我没有得到任何错误，并得到的钥匙和证书和其他文件，如预期。

Which I think all works fine. I don't get any errors and get the keys and certificates and other files as expected.

接下来我复制 certificate.cer ， signature.sig 和 license.txt

现在我想检查签名是否已经由我签名，并且对license.txt有效。我发现很难找到任何好的例子，但这是我目前的：

Now I want to check if the signature has been signed by me and is valid for the license.txt. I found it fairly hard to find any good examples but this is what I have currently:

Seucyrity.Framework 我发现使用 SecKeyRef 引用RSA密钥/证书和 SecKeyRawVerify 来验证签名。

The Seucyrity.Framework I found out uses a SecKeyRef to reference an RSA key / certificate and SecKeyRawVerify to verify a signature.

我有以下方法从文件加载公共密钥。

I have the following method to load the public key from a file.

- (SecKeyRef)publicKeyFromFile:(NSString *) path
{
    NSData *myCertData = [[NSFileManager defaultManager] contentsAtPath:path];
    CFDataRef myCertDataRef = (__bridge CFDataRef) myCertData;

    SecCertificateRef cert = SecCertificateCreateWithData (kCFAllocatorDefault, myCertDataRef);
    CFArrayRef certs = CFArrayCreate(kCFAllocatorDefault, (const void **) &cert, 1, NULL);
    SecPolicyRef policy = SecPolicyCreateBasicX509();
    SecTrustRef trust;
    SecTrustCreateWithCertificates(certs, policy, &trust);
    SecTrustResultType trustResult;
    SecTrustEvaluate(trust, &trustResult);
    SecKeyRef pub_key_leaf = SecTrustCopyPublicKey(trust);

    if (trustResult == kSecTrustResultRecoverableTrustFailure)
    {
        NSLog(@"I think this is the problem");
    }
    return pub_key_leaf;
}

这是基于此 SO post。

Which is based on this SO post.

对于签名验证，我找到以下函数

For the signature validation I found the following function

BOOL PKCSVerifyBytesSHA256withRSA(NSData* plainData, NSData* signature, SecKeyRef publicKey)
{
    size_t signedHashBytesSize = SecKeyGetBlockSize(publicKey);
    const void* signedHashBytes = [signature bytes];

    size_t hashBytesSize = CC_SHA256_DIGEST_LENGTH;
    uint8_t* hashBytes = malloc(hashBytesSize);
    if (!CC_SHA256([plainData bytes], (CC_LONG)[plainData length], hashBytes)) {
        return nil;
    }

    OSStatus status = SecKeyRawVerify(publicKey,
                                      kSecPaddingPKCS1SHA256,
                                      hashBytes,
                                      hashBytesSize,
                                      signedHashBytes,
                                      signedHashBytesSize);

    return status == errSecSuccess;
}

这取自这里

在我的项目中，我调用的代码如下：

In my project I call the code like so:

// Get the licence data
NSString *licencePath = [[NSBundle mainBundle] pathForResource:@"licence" ofType:@"txt"];
NSData *data = [[NSFileManager defaultManager] contentsAtPath:licencePath];

// Get the signature data
NSString *signaturePath = [[NSBundle mainBundle] pathForResource:@"signature" ofType:@"sig"];
NSData *signature = [[NSFileManager defaultManager] contentsAtPath:signaturePath];

// Get the public key
NSString *publicKeyPath = [[NSBundle mainBundle] pathForResource:@"certificate" ofType:@"cer"];
SecKeyRef publicKey = [self publicKeyFromFile:publicKeyPath];

// Check if the signature is valid with this public key for this data
BOOL result = PKCSVerifyBytesSHA256withRSA(data, signature, publicKey);

if (result)
{
    NSLog(@"Alright All good!");
}
else
{
    NSLog(@"Something went wrong!");
}

目前总是说：出错了！虽然我不知道什么。我发现在获取公钥的方法中的信任结果等于 kSecTrustResultRecoverableTrustFailure ，我认为是问题。在 Apple文档中，我发现可能是由于已过期的证书。虽然这似乎不是这里的情况。但也许我生成证书的方式有问题吗？

Currently it always says: "Something went wrong!" though I am not sure what. I found out that trust result in the method that fetches the public key equals kSecTrustResultRecoverableTrustFailure which I think is the problem. In the Apple documentation I found that could be the result of a certificate that has been expired. Though that does not seem to be the case here. But maybe there is something wrong with the way I generate my certificate?

我的问题归结到，我做错了，我怎么解决这个问题？我发现这个文档很稀疏，很难阅读。

My question boils down to, what am I doing wrong, and how could I fix that? I find the documentation on this quite sparse and hard to read.

我有上传具有生成的证书和此处引用的代码的iOS项目。

I have uploaded an iOS project with generated certificates and the code referenced here. Maybe that could come in handy.

推荐答案

问题在于你创建签名文件的方式;在同一步骤后，我能够生成二进制等效的 signature.sig 文件。

The problem is lying on the way you create the signature file; following the same step I was able to produce the binary equivalent signature.sig file.

code> hash 文件我们可以看到openssl添加一些前缀（和十六进制编码的哈希）：

By looking inside the hash file we can see openssl add some prefix (and hex encode the hash):

$ cat hash
SHA256(licence.txt)= 652b23d424dd7106b66f14c49bac5013c74724c055bc2711521a1ddf23441724

c $ c> signature.sig 是基于 license.txt

So signature.sig is based on that and not on license.txt

通过使用您的示例并使用以下内容创建签名文件：

By using your sample and creating the signing file with:

openssl dgst -sha256 -sign certificates/private_key.pem licence.txt > signature.sig

签名步骤正确，并且示例输出：好了！

The hashing & signing step gets correct, and the sample outputs: Alright All good!

我的档案的最后状态，只是为了

The final state of my file, just in case

- (SecKeyRef)publicKeyFromFile:(NSString *) path
{
    NSData * certificateData = [[NSFileManager defaultManager] contentsAtPath:path];
    SecCertificateRef certificateFromFile = SecCertificateCreateWithData(NULL, (__bridge CFDataRef)certificateData);
    SecPolicyRef secPolicy = SecPolicyCreateBasicX509();
    SecTrustRef trust;
    SecTrustCreateWithCertificates( certificateFromFile, secPolicy, &trust);
    SecTrustResultType resultType;
    SecTrustEvaluate(trust, &resultType);
    SecKeyRef publicKey = SecTrustCopyPublicKey(trust);
    return publicKey;
}

BOOL PKCSVerifyBytesSHA256withRSA(NSData* plainData, NSData* signature, SecKeyRef publicKey)
{
    uint8_t digest[CC_SHA256_DIGEST_LENGTH];
    if (!CC_SHA256([plainData bytes], (CC_LONG)[plainData length], digest))
        return NO;

    OSStatus status = SecKeyRawVerify(publicKey,
                                      kSecPaddingPKCS1SHA256,
                                      digest,
                                      CC_SHA256_DIGEST_LENGTH,
                                      [signature bytes],
                                      [signature length]);

    return status == errSecSuccess;
}

PS： malloc 是一个泄漏

编辑：

当前 signature.sig 文件按原样工作，您必须生成与openssl相同的步骤（添加前缀，十六进制哈希和换行符 \\ n ），然后使用 kSecPaddingPKCS1 将此数据传递到 SecKeyRawVerify ，而不是 kSecPaddingPKCS1SHA256 ：

To make your current signature.sig file work as-is, you have to produce the same step as openssl (add prefix, hex-hash, and a newline \n), then pass this data to SecKeyRawVerify with kSecPaddingPKCS1 and not kSecPaddingPKCS1SHA256:

BOOL PKCSVerifyBytesSHA256withRSA(NSData* plainData, NSData* signature, SecKeyRef publicKey)
{
    uint8_t digest[CC_SHA256_DIGEST_LENGTH];
    if (!CC_SHA256([plainData bytes], (CC_LONG)[plainData length], digest))
        return NO;

    NSMutableString *hashFile = [NSMutableString stringWithFormat:@"SHA256(licence.txt)= "];
    for (NSUInteger index = 0; index < sizeof(digest); ++index)
        [hashFile appendFormat:@"%02x", digest[index]];

    [hashFile appendString:@"\n"];
    NSData *hashFileData = [hashFile dataUsingEncoding:NSNonLossyASCIIStringEncoding];

    OSStatus status = SecKeyRawVerify(publicKey,
                                      kSecPaddingPKCS1,
                                      [hashFileData bytes],
                                      [hashFileData length],
                                      [signature bytes],
                                      [signature length]);

    return status == errSecSuccess;
}

这篇关于验证RSA签名iOS的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！