fix: added new implementation of randomBytes and deprecated old one

Author: JeneaVranceanu

Sources/Web3Core/Utility/Data+Extension.swift

@@ -41,27 +41,51 @@ extension Data {
         }
     }
 
+    @available(*, deprecated, message: "Please, use throwing `randomBytes(count)` function instead to get information instead of `nil` value on why the function call failed.")
+    /// Runs `SecRandomCopyBytes` for Apple platforms and `openssl rand -hex` for other platforms
+    /// to generate cryptographically secure random bytes.
+    /// - Parameter count: how many bytes to generate. Value below or equal to 0 will return `nil`.
+    /// - Returns: random bytes or `nil`.
     public static func randomBytes(length: Int) -> Data? {
-        #if os(Linux)
-//        return Data(URandom().bytes(count: length))
-        return try? Data.random(length: length)
-        #else
-        for _ in 0...1024 {
-            var data = Data(repeating: 0, count: length)
-            let result = data.withUnsafeMutableBytes { (body: UnsafeMutableRawBufferPointer) -> Int32? in
-                if let bodyAddress = body.baseAddress, body.count > 0 {
+        try? randomBytes(count: length)
+    }
+
+    /// Runs `SecRandomCopyBytes` for Apple platforms and `openssl rand -hex` for other platforms
+    /// to generate cryptographically secure random bytes.
+    /// - Parameter count: how many bytes to generate. Value below or equal to 0 will throw an error.
+    /// - Parameter useOpenSSL: **has no effect on Linux and Windows**. When set to `true` forces the use of external executable `openssl`. It's your responsibility to make sure openssl is installed on this machine. By default set to `false`. To install follow [the official guide](https://www.openssl.org/source/ ).
+    /// - Returns: random bytes or throws an error,
+    public static func randomBytes(count: Int, useOpenSSL: Bool = true) throws -> Data {
+        guard count > 0 else { throw Web3Error.valueError(desc: "Cannot generate \(count) random bytes.") }
+
+        #if !(os(Linux) || os(Windows))
+        if !useOpenSSL {
+            for _ in 0...1024 {
+                var data = Data(repeating: 0, count: count)
+                let result = try data.withUnsafeMutableBytes { (body: UnsafeMutableRawBufferPointer) -> Int32? in
+                    guard let bodyAddress = body.baseAddress, body.count == count else {
+                        throw Web3Error.processingError(desc: "Address of the buffer is nil (\(body.baseAddress == nil)) or the count of bytes in the buffer is not equal to the count requested by the user (\(body.count < count)).")
+                    }
+
                     let pointer = bodyAddress.assumingMemoryBound(to: UInt8.self)
-                    return SecRandomCopyBytes(kSecRandomDefault, length, pointer)
-                } else {
-                    return nil
+                    return SecRandomCopyBytes(kSecRandomDefault, count, pointer)
+                }
+                if let notNilResult = result, notNilResult == errSecSuccess {
+                    return data
                 }
-            }
-            if let notNilResult = result, notNilResult == errSecSuccess {
-                return data
             }
         }
-        return nil
         #endif
+        let randomBytesHex = try ShellCommandExecutor().run(commandName: "openssl rand -hex \(count)")
+        guard let bytes = Data.fromHex(randomBytesHex) else {
+            throw Web3Error.processingError(desc: "Random bytes generated by the openssl are in an invalid hex representation: \(randomBytesHex)")
+        }
+
+        guard bytes.count == count else {
+            throw Web3Error.processingError(desc: "Count of generated by the openssl random bytes is not equal to the count requested by the user: expected \(count), given \(bytes.count).")
+        }
+
+        return bytes
     }
 
     public func bitsInRange(_ startingBit: Int, _ length: Int) -> UInt64? { // return max of 8 bytes for simplicity, non-public