/*

 * Copyright 2012 Andrew Duggan

 * Copyright 2012 Synaptics Inc.

 * Copyright 2019 Richard Hughes <richard@hughsie.com>

 *

 * SPDX-License-Identifier: LGPL-2.1-or-later

 */

#include "config.h"

#include <fwupdplugin.h>

#include <fcntl.h>

#include <sys/stat.h>

#include <sys/types.h>

#ifdef HAVE_GNUTLS

#include <gnutls/abstract.h>

#include <gnutls/crypto.h>

#endif

#include "fu-synaptics-rmi-common.h"

#define RMI_FUNCTION_QUERY_OFFSET       0

#define RMI_FUNCTION_COMMAND_OFFSET       1

#define RMI_FUNCTION_CONTROL_OFFSET       2

#define RMI_FUNCTION_DATA_OFFSET        3

#define RMI_FUNCTION_INTERRUPT_SOURCES_OFFSET 4

#define RMI_FUNCTION_NUMBER         5

#define RMI_FUNCTION_VERSION_MASK     0x60

#define RMI_FUNCTION_INTERRUPT_SOURCES_MASK 0x7

#ifdef HAVE_GNUTLS

typedef guchar gnutls_data_t;

#pragma clang diagnostic push

#pragma clang diagnostic ignored "-Wunused-function"

G_DEFINE_AUTOPTR_CLEANUP_FUNC(gnutls_data_t, gnutls_free)

G_DEFINE_AUTO_CLEANUP_FREE_FUNC(gnutls_pubkey_t, gnutls_pubkey_deinit, NULL)

#pragma clang diagnostic pop

#endif

guint32

fu_synaptics_rmi_generate_checksum(const guint8 *data, gsize len)

{

  guint32 lsw = 0xffff;

  guint32 msw = 0xffff;

  for (gsize i = 0; i < len / 2; i++) {

    lsw += fu_memread_uint16(&data[i * 2], G_LITTLE_ENDIAN);

    msw += lsw;

    lsw = (lsw & 0xffff) + (lsw >> 16);

    msw = (msw & 0xffff) + (msw >> 16);

  }

  return msw << 16 | lsw;

}

FuSynapticsRmiFunction *

fu_synaptics_rmi_function_parse(GByteArray *buf,

        guint16 page_base,

        guint interrupt_count,

        GError **error)

{

  FuSynapticsRmiFunction *func;

  guint8 interrupt_offset;

  const guint8 *data = buf->data;

  /* not expected */

  if (buf->len != RMI_DEVICE_PDT_ENTRY_SIZE) {

    g_set_error(error,

          FWUPD_ERROR,

          FWUPD_ERROR_INTERNAL,

          "PDT entry buffer invalid size %u != %i",

          buf->len,

          RMI_DEVICE_PDT_ENTRY_SIZE);

    return NULL;

  }

  func = g_new0(FuSynapticsRmiFunction, 1);

  func->query_base = data[RMI_FUNCTION_QUERY_OFFSET] + page_base;

  func->command_base = data[RMI_FUNCTION_COMMAND_OFFSET] + page_base;

  func->control_base = data[RMI_FUNCTION_CONTROL_OFFSET] + page_base;

  func->data_base = data[RMI_FUNCTION_DATA_OFFSET] + page_base;

  func->interrupt_source_count =

      data[RMI_FUNCTION_INTERRUPT_SOURCES_OFFSET] & RMI_FUNCTION_INTERRUPT_SOURCES_MASK;

  func->function_number = data[RMI_FUNCTION_NUMBER];

  func->function_version =

      (data[RMI_FUNCTION_INTERRUPT_SOURCES_OFFSET] & RMI_FUNCTION_VERSION_MASK) >> 5;

  if (func->interrupt_source_count > 0) {

    func->interrupt_reg_num = (interrupt_count + 8) / 8 - 1;

    /* set an enable bit for each data source */

    interrupt_offset = interrupt_count % 8;

    func->interrupt_mask = 0;

    for (guint i = interrupt_offset;

         i < (func->interrupt_source_count + interrupt_offset);

         i++)

      FU_BIT_SET(func->interrupt_mask, i);

  }

  return func;

}

gboolean

fu_synaptics_rmi_verify_sha256_signature(GBytes *payload,

           GBytes *pubkey,

           GBytes *signature,

           GError **error)

{

#ifdef HAVE_GNUTLS

  gnutls_datum_t hash;

  gnutls_datum_t m;

  gnutls_datum_t e;

  gnutls_datum_t sig;

  gnutls_hash_hd_t sha2;

  g_auto(gnutls_pubkey_t) pub = NULL;

  gint ec;

  guint8 exponent[] = {1, 0, 1};

  guint hash_length = gnutls_hash_get_len(GNUTLS_DIG_SHA256);

  g_autoptr(gnutls_data_t) hash_data = NULL;

  /* hash firmware data */

  hash_data = gnutls_malloc(hash_length);

  gnutls_hash_init(&sha2, GNUTLS_DIG_SHA256);

  gnutls_hash(sha2, g_bytes_get_data(payload, NULL), g_bytes_get_size(payload));

  gnutls_hash_deinit(sha2, hash_data);

  /* hash */

  hash.size = hash_length;

  hash.data = hash_data;

  /* modulus */

  m.size = g_bytes_get_size(pubkey);

  m.data = (guint8 *)g_bytes_get_data(pubkey, NULL);

  /* exponent */

  e.size = sizeof(exponent);

  e.data = exponent;

  /* signature */

  sig.size = g_bytes_get_size(signature);

  sig.data = (guint8 *)g_bytes_get_data(signature, NULL);

  gnutls_pubkey_init(&pub);

  ec = gnutls_pubkey_import_rsa_raw(pub, &m, &e);

  if (ec < 0) {

    g_set_error(error,

          FWUPD_ERROR,

          FWUPD_ERROR_NOT_SUPPORTED,

          "failed to import RSA key: %s",

          gnutls_strerror(ec));

    return FALSE;

  }

  ec = gnutls_pubkey_verify_hash2(pub, GNUTLS_SIGN_RSA_SHA256, 0, &hash, &sig);

  if (ec < 0) {

    g_set_error(error,

          FWUPD_ERROR,

          FWUPD_ERROR_NOT_SUPPORTED,

          "failed to verify firmware: %s",

          gnutls_strerror(ec));

    return FALSE;

  }

#endif

  /* success */

  return TRUE;

}