iOS验证数字签名

Question

在我的应用程序中，我有一个公钥（表示为字符串），普通消息和数字签名，表示为base64编码字符串，用SHA256散列，用RSA加密）。现在，我需要验证数字签名。我试图做如下操作：

1. 从nsstring创建seckeyref（取自此处）
2. 根据原始消息创建SHA256摘要
3. 使用seckeyrawverify函数
验证签名

（我正在努力避免使用OpenSSL函数）

此外，我的数字签名是使用Java的SHA256withRSA方法创建的。我在这里读到SHA256WithRSA将算法标识符附加到实际哈希中。现在，我不确定是否需要将它追加到散列中。

下面是我的代码：

-(BOOL) verifySignature:(NSString*) rawData andKey:(NSString*) key andSignature:(NSString*)signature {

    NSData* originalData = [rawData dataUsingEncoding:NSUTF8StringEncoding];
    NSData *signatureData = [NSData dataFromBase64String:signature];

    SecKeyRef publicKey = [self generatePublicKey:key];

    uint8_t sha2HashDigest[CC_SHA256_DIGEST_LENGTH];
    CC_SHA256([originalData bytes], [originalData length], sha2HashDigest);

    //DO I NEED THIS?
    NSString *algIdentifier = @"1.3.14.3.2.26";
    NSData *algData = [algIdentifier dataUsingEncoding:NSUTF8StringEncoding];
    NSData* d_hash = [NSData dataWithBytes:sha2HashDigest length:CC_SHA256_DIGEST_LENGTH];

    NSMutableData *concatenatedData = [NSMutableData data];
    [concatenatedData appendData:algData];
    [concatenatedData appendData:d_hash];

    OSStatus verficationResult =  SecKeyRawVerify (publicKey,
                     kSecPaddingPKCS1SHA256,
                     (const uint8_t *)[d_hash bytes],
                     (size_t)[d_hash length],
                     (const uint8_t *)[signatureData bytes],
                     (size_t)[signatureData length]
                     );


    CFRelease(publicKey);

    if (verficationResult == errSecSuccess){
        NSLog(@"Verified");
        return YES;
    }
    return NO;

}

- (SecKeyRef)generatePublicKey:(NSString *)key
{

    // This will be base64 encoded, decode it.
    NSData *d_key = [NSData dataFromBase64String:key];
    d_key = [self stripPublicKeyHeader:d_key];
    if (d_key == nil) return(nil);

    NSData *d_tag = [NSData dataWithBytes:[@"pubKey" UTF8String] length:[@"pubKey" length]];

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

    CFTypeRef persistKey = nil;

    // Add persistent version of the key to system keychain
    [publicKey setObject:d_key forKey:(id)kSecValueData];
    [publicKey setObject:(id) kSecAttrKeyClassPublic forKey:(id)
     kSecAttrKeyClass];
    [publicKey setObject:[NSNumber numberWithBool:YES] forKey:(id)
     kSecReturnPersistentRef];

    OSStatus secStatus = SecItemAdd((CFDictionaryRef)publicKey, &persistKey);
    if (persistKey != nil) CFRelease(persistKey);

    if ((secStatus != noErr) && (secStatus != errSecDuplicateItem)) {
        [publicKey release];
        return(nil);
    }

    // Now fetch the SecKeyRef version of the key
    SecKeyRef keyRef = nil;

    [publicKey removeObjectForKey:(id)kSecValueData];
    [publicKey removeObjectForKey:(id)kSecReturnPersistentRef];
    [publicKey setObject:[NSNumber numberWithBool:YES] forKey:(id)kSecReturnRef
     ];

    [publicKey setObject:(id) kSecAttrKeyTypeRSA forKey:(id)kSecAttrKeyType];
    secStatus = SecItemCopyMatching((CFDictionaryRef)publicKey,
                                    (CFTypeRef *)&keyRef);

    [publicKey release];
    return keyRef;

}

Answer 1

也许这个答案有点晚，但我也有同样的问题。

事实证明，Java为您处理散列，而iOS没有。

因此，如果您有一个名为plaintext的明文，您可以在Java中生成一个签名，执行以下操作：

public static byte[] sign(PrivateKey key, byte[] plainText) {
    try {
        Signature signature = Signature.getInstance("SHA256withRSA");
        signature.initSign(key);
        signature.update(plainText);
        return signature.sign();
    } catch (Exception e) {
        return null;
    }
}

+ (BOOL)verifySignature:(uint8_t*)signature signatureLen:(size_t)sLen
            withPlainText:(uint8_t*)plainText plainTextLen:(size_t)pLen
            andKey:(SecKeyRef)key {
    uint8_t hash[32];
    CC_SHA256(plainText, pLen, hash);
    OSStatus returnCode = SecKeyRawVerify(key,
                                          kSecPaddingPKCS1SHA256,
                                          hash,
                                          32,
                                          signature,
                                          sLen);
    return returnCode == 0;
}

在上述方法中，signature是Java方法生成的字节。

当然，您可能不希望硬编码参数，如所使用的散列函数（和散列长度）。