RSA SHA256登录iOS并在Java上进行验证

Question

1. I generated an RSA key pair with SecKeyGeneratePair. The key size in bits is 2048.

    NSDictionary *privateAttributes = @{(NSString *)kSecAttrIsPermanent: @YES, (NSString *)kSecAttrApplicationTag: PrivTag}; NSDictionary *publicAttributes = @{(NSString *)kSecAttrIsPermanent: @YES, (NSString *)kSecAttrApplicationTag: PubTag}; NSDictionary *pairAttributes = @{(NSString *)kSecAttrKeyType: (NSString *)kSecAttrKeyTypeRSA, (NSString *)kSecAttrKeySizeInBits: @2048, (NSString *)kSecPublicKeyAttrs: publicAttributes, (NSString *)kSecPrivateKeyAttrs: privateAttributes}; SecKeyRef publicKeyRef; SecKeyRef privateKeyRef; OSStatus osStatus = SecKeyGeneratePair((CFDictionaryRef)pairAttributes, &publicKeyRef, &privateKeyRef); switch (osStatus) { case noErr: break; default: break; } 

2. Create the X.509 format of the public key and send it to the server.

3. Create the SHA256 digest of the custom string with CC_SHA256.

    NSMutableData *hash = [NSMutableData dataWithLength:(NSUInteger)CC_SHA256_DIGEST_LENGTH]; NSData *data = [stringToSign dataUsingEncoding:NSUTF8StringEncoding]; CC_SHA256(data.bytes, (CC_LONG)data.length, hash.mutableBytes); 

4. Sign the string with SecKeyRawSign method using kSecPaddingPKCS1SHA256.

    // Sign the hash with the private key size_t blockSize = SecKeyGetBlockSize(privateKeyRef); NSUInteger hashDataLength = hash.length; const unsigned char *hashData = (const unsigned char *)hash.bytes; NSMutableData *result = [NSMutableData dataWithLength:blockSize]; uint8_t *signedHashBytes = malloc(blockSize * sizeof(uint8_t)); memset((void *) signedHashBytes, 0x0, blockSize); size_t encryptedDataLength = blockSize; OSStatus status = SecKeyRawSign(privateKeyRef, kSecPaddingPKCS1SHA256, hashData, hashDataLength, signedHashBytes, &encryptedDataLength); NSData *signedHash = [NSData dataWithBytes:(const void *) signedHashBytes length:(NSUInteger) encryptedDataLength]; 

5. Apply base64 on the signed data and send it to the server.

6. The java server cannot verify it with the public key.

I have the same above code in Swift. As a debug step, I've exported my private key too and tried to follow the exact same steps in java. Until step 3 everything is the same. So, the iOS creates the same digest as the java app. The fourth step, the signing creates a different output than the java code.

Here's the java code:

final Signature instance = Signature.getInstance("SHA256withRSA");
instance.initSign(privateKey);
instance.update(MessageDigest.getInstance("SHA-256").digest(rawString.toString().getBytes("UTF-8")));

Answer 1

Digital signature API for iOS and Java is different but the result is the same.

iOS SecKeyRawSign with kSecPaddingPKCS1SHA256 uses a SHA256 digest, but in Java Signature.sign requires the raw data and it makes digest+pkcs1. Use

instance.update(rawString.toString().getBytes("UTF-8"));