Update libsodium wrapper to prevent segfaults

src/Discord.Net/Audio/Sodium/SecretBox.cs

@@ -1,9 +1,67 @@
-using System.Runtime.InteropServices;
+using System;
+using System.Runtime.InteropServices;
 
 namespace Discord.Audio
 {
     public unsafe static class SecretBox
     {
+        // from crypto_secretbox.h and crypto_secretbox_xsalsa20poly1305.h
+        private const uint crypto_secretbox_KEYBYTES = 32U;
+        private const uint crypto_secretbox_NONCEBYTES = 24U;
+        private const uint crypto_secretbox_MACBYTES = 16U;
+
+        [DllImport("libsodium", CallingConvention = CallingConvention.Cdecl)]
+        private static extern int crypto_secretbox_easy(
+            [Out] byte[] c, // ciphertext
+            [In] byte[] m, // message
+            [MarshalAs(UnmanagedType.U8)] ulong mlen, // length of message
+            [In] byte[] n, // nonce
+            [In] byte[] k // key
+            );
+
+        [DllImport("libsodium", CallingConvention = CallingConvention.Cdecl)]
+        private static extern int crypto_secretbox_open_easy(
+            [Out] byte[] m, // message
+            [In] byte[] c, // ciphertext
+            [MarshalAs(UnmanagedType.U8)] ulong clen, // length of ciphertext
+            [In] byte[] n, // nonce
+            [In] byte[] k // key
+            );
+
+        // Both of the above functions return 0 on success, -1 on error
+
+        public static void Encrypt(byte[] input, int inputOffset, ulong inputLength, byte[] output, int outputOffset, byte[] nonce, byte[] secret)
+        {
+            byte[] _input = new byte[inputLength];
+            Buffer.BlockCopy(input, inputOffset, _input, 0, (int)inputLength); // TODO: this will probably cause an overflow or throw an exception...
+
+            byte[] _output = new byte[crypto_secretbox_MACBYTES + inputLength];
+            int result = crypto_secretbox_easy(_output, _input, inputLength, nonce, secret);
+
+            if (result == -1)
+                throw new InvalidOperationException("Failed to encrypt the provided payload");
+
+            Buffer.BlockCopy(_output, 0, output, outputOffset, _output.Length);
+        }
+
+        public static void Decrypt(byte[] input, int inputOffset, ulong inputLength, byte[] output, int outputOffset, byte[] nonce, byte[] secret)
+        {
+            if (inputLength < crypto_secretbox_MACBYTES)
+                throw new ArgumentException($"the length of the input arary must be greater than {crypto_secretbox_MACBYTES} bytes", "inputLength");
+
+            byte[] _input = new byte[inputLength];
+            Buffer.BlockCopy(input, inputOffset, _input, 0, (int)inputLength); // TODO: this will also probably overflow or throw an exception
+
+            byte[] _output = new byte[inputLength - crypto_secretbox_MACBYTES];
+            int result = crypto_secretbox_open_easy(_output, _input, inputLength, nonce, secret);
+
+            if (result == -1)
+                throw new InvalidOperationException("Failed to verify the decrypted payload");
+
+            Buffer.BlockCopy(_output, 0, output, outputOffset, _output.Length);
+        }
+
+        /* I kept the old code here to refer to in case it is needed
         [DllImport("libsodium", EntryPoint = "crypto_secretbox_easy", CallingConvention = CallingConvention.Cdecl)]
         private static extern int SecretBoxEasy(byte* output, byte* input, long inputLength, byte[] nonce, byte[] secret);
         [DllImport("libsodium", EntryPoint = "crypto_secretbox_open_easy", CallingConvention = CallingConvention.Cdecl)]
@@ -21,5 +79,6 @@ namespace Discord.Audio
             fixed (byte* outPtr = output)
                 return SecretBoxOpenEasy(outPtr + outputOffset, inPtr + inputOffset, inputLength, nonce, secret);
         }
+        */
     }
 }

src/Discord.Net/Audio/Streams/RTPReadStream.cs

@@ -32,7 +32,7 @@ namespace Discord.Audio
         public override void Write(byte[] buffer, int offset, int count)
         {
             Buffer.BlockCopy(buffer, 0, _nonce, 0, 12);
-            count = SecretBox.Decrypt(buffer, offset, count, _buffer, 0, _nonce, _secretKey);
+            SecretBox.Decrypt(buffer, offset, (ulong)count, _buffer, 0, _nonce, _secretKey);
             var newBuffer = new byte[count];
             Buffer.BlockCopy(_buffer, 0, newBuffer, 0, count);
             _queuedData.Add(newBuffer);

src/Discord.Net/Audio/Streams/RTPWriteStream.cs

@@ -46,7 +46,7 @@ namespace Discord.Audio
             }
 
             Buffer.BlockCopy(buffer, 0, _nonce, 0, 12);
-            count = SecretBox.Encrypt(buffer, offset, count, _buffer, 12, _nonce, _secretKey);
+            SecretBox.Encrypt(buffer, offset, (ulong)count, _buffer, 12, _nonce, _secretKey);
             _audioClient.Send(_buffer, count);
         }