Overlapping accesses to 'salt', but modification requires exclusive access; consider copying to a local variable

Question

I am developing a highly secured iOS application with sensitive data. I'm trying to use an AES256 encryption system to secure Data.

I followed the tutorial here https://code.tutsplus.com/tutorials/securing-ios-data-at-rest-encryption--cms-28786

Xcode 11 (Swift 5) tells me "Overlapping accesses to 'salt', but modification requires exclusive access; consider copying to a local variable"

Could you please tell how can I solve this issue please ?

Thank you.

Here's my code :

var key = Data(repeating:0, count:kCCKeySizeAES256)
    var salt = Data(count: 8)
    salt.withUnsafeMutableBytes {
        (saltBytes: UnsafeMutablePointer<UInt8>) in//-> Void in
        let saltStatus = SecRandomCopyBytes(kSecRandomDefault, salt.count, saltBytes)
        if saltStatus == errSecSuccess
        {
            let passwordData = password.data(using:String.Encoding.utf8)!
            key.withUnsafeMutableBytes { (keyBytes : UnsafeMutablePointer<UInt8>) in
                let derivationStatus = CCKeyDerivationPBKDF(CCPBKDFAlgorithm(kCCPBKDF2), password, passwordData.count, saltBytes, salt.count, CCPseudoRandomAlgorithm(kCCPRFHmacAlgSHA512), 14271, keyBytes, key.count)
                if derivationStatus != Int32(kCCSuccess)
                {
                    setupSuccess = false
                }
            }
        }
        else
        {
            setupSuccess = false
        }
    }

Answer 1

Finally, I resolved my issue modifying my code like this :

salt.withUnsafeMutableBytes { (saltBuffer: UnsafeMutableRawBufferPointer) in  
let saltBytes = saltBuffer.bindMemory(to: UInt8.self)  
let saltStatus = SecRandomCopyBytes(kSecRandomDefault, saltBytes.count, saltBytes.baseAddress!)  
if saltStatus == errSecSuccess {  
    let passwordData = password.data(using: .utf8)!  
    key.withUnsafeMutableBytes { (keyBuffer: UnsafeMutableRawBufferPointer) in  
        let keyBytes = keyBuffer.bindMemory(to: UInt8.self)  
        let derivationStatus = CCKeyDerivationPBKDF(CCPBKDFAlgorithm(kCCPBKDF2), password, passwordData.count, saltBytes.baseAddress!, saltBytes.count, CCPseudoRandomAlgorithm(kCCPRFHmacAlgSHA512), 14271, keyBytes.baseAddress!, keyBytes.count)  
        if derivationStatus != Int32(kCCSuccess) {  
            setupSuccess = false  
        }  
    }  
} else {  
    setupSuccess = false  
}  

}