feat: replace makesalt with a more secure function (MESSENGER-6727)

bwi/SecureStorage/SecureFileStorage.swift

@@ -17,6 +17,7 @@
 
 import Foundation
 import MatrixSDK
+import Security
 
 
 class SecureFileStorage {
@@ -100,11 +101,28 @@ class SecureFileStorage {
     // MARK: -
     
     private func makeSalt() -> String {
-        let secret = ProcessInfo.processInfo.globallyUniqueString
-        let index = secret.index(secret.startIndex, offsetBy: 32)
-        return String(secret.prefix(upTo: index))
+        return generateSecureRandomString(length: 32)!
     }
     
+    func generateSecureRandomString(length: Int) -> String? {
+        let characters = Array("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")
+        let charactersCount = characters.count
+        
+        var randomBytes = [UInt8](repeating: 0, count: length)
+        let status = SecRandomCopyBytes(kSecRandomDefault, length, &randomBytes)
+        
+        guard status == errSecSuccess else {
+            MXLog.error("generateSecureRandomString failed")
+            return nil
+        }
+        
+        let randomString = randomBytes.map { byte in
+            String(characters[Int(byte) % charactersCount])
+        }.joined()
+        
+        return randomString
+    }
+
     func update(passphrase: String) throws {
         guard !locked else {
             throw SecureStorageError.locked