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5e4cc87d6c
This is not really a cipher, more just obfuscation and is specific to the Walkera Devo line of RC controllers. Many thanks to Mike Meyer for the help.
123 lines
3.0 KiB
C
123 lines
3.0 KiB
C
/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*-
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*
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* Copyright (C) 2016 Richard Hughes <richard@hughsie.com>
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*
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* Licensed under the GNU Lesser General Public License Version 2.1
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "config.h"
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#include <string.h>
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#include "dfu-cipher-devo.h"
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#include "dfu-error.h"
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/* this is not really a cipher, more just obfuscation and is specific to the
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* Walkera Devo line of RC controllers */
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static gboolean
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dfu_tool_parse_devo_key (const gchar *key, guint8 *offset, GError **error)
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{
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gchar *endptr;
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guint64 tmp;
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tmp = g_ascii_strtoull (key, &endptr, 10);
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if (tmp > 0xff || endptr[0] != '\0') {
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g_set_error (error,
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DFU_ERROR,
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DFU_ERROR_INTERNAL,
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"Failed to parse offset value '%s'", key);
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return FALSE;
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}
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/* success */
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if (offset != NULL)
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*offset = (guint8) tmp;
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g_debug ("using devo offset %u", (guint) tmp);
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return TRUE;
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}
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/**
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* dfu_cipher_decrypt_devo: (skip)
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* @key: a XTEA key
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* @data: data to parse
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* @length: length of @data
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* @error: a #GError, or %NULL
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*
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* Decrypt a buffer using DEVO obfuscation.
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*
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* Returns: %TRUE for success
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**/
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gboolean
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dfu_cipher_decrypt_devo (const gchar *key,
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guint8 *data,
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guint32 length,
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GError **error)
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{
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guint8 offset;
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guint32 i;
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if (!dfu_tool_parse_devo_key (key, &offset, error))
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return FALSE;
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/* no words for how stupid this cipher is */
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for (i = 0; i < length; i++) {
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guint8 val = data[i];
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if (val >= 0x80 + offset && val <= 0xcf)
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data[i] -= offset;
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else if (val >= 0x80 && val < 0x80 + offset)
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data[i] += (0x50 - offset);
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}
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return TRUE;
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}
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/**
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* dfu_cipher_encrypt_devo: (skip)
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* @key: a XTEA key
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* @data: data to parse
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* @length: length of @data
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* @error: a #GError, or %NULL
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*
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* Encrypt a buffer using DEVO obfuscation.
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*
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* Returns: %TRUE for success
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**/
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gboolean
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dfu_cipher_encrypt_devo (const gchar *key,
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guint8 *data,
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guint32 length,
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GError **error)
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{
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guint8 offset;
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guint32 i;
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if (!dfu_tool_parse_devo_key (key, &offset, error))
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return FALSE;
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/* no words for how stupid this cipher is */
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for (i = 0; i < length; i++) {
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guint8 val = data[i];
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if (val >= 0x80 && val <= 0xcf - offset)
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data[i] += offset;
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else if (val >= 0xd0 - offset && val < 0xd0)
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data[i] -= (0x50 - offset);
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}
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return TRUE;
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}
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