circuitpython/shared-bindings/aesio/aes.c

#include <stdint.h>
#include <string.h>

#include "py/obj.h"
#include "py/objproperty.h"
#include "py/runtime.h"

#include "shared-bindings/aesio/__init__.h"

// Defined at the end of this file

//| class AES:
//|     """Encrypt and decrypt AES streams"""
//|
//|     def __init__(self, key, mode=0, iv=None, segment_size=8) -> Any:
//|         """Create a new AES state with the given key.
//|
//|            :param bytearray key: A 16-, 24-, or 32-byte key
//|            :param int mode: AES mode to use.  One of: AES.MODE_ECB, AES.MODE_CBC, or
//|                             AES.MODE_CTR
//|            :param bytearray iv: Initialization vector to use for CBC or CTR mode
//|
//|            Additional arguments are supported for legacy reasons.
//|
//|            Encrypting a string::
//|
//|              import aesio
//|              from binascii import hexlify
//|
//|              key = b'Sixteen byte key'
//|              inp = b'Circuit Python!!' # Note: 16-bytes long
//|              outp = bytearray(len(inp))
//|              cipher = aesio.AES(key, aesio.mode.MODE_ECB)
//|              cipher.encrypt_into(inp, outp)
//|              hexlify(outp)"""
//|         ...
//|

STATIC mp_obj_t aesio_aes_make_new(const mp_obj_type_t *type, size_t n_args,
                                   const mp_obj_t *pos_args,
                                   mp_map_t *kw_args) {
  (void)type;
  enum { ARG_key, ARG_mode, ARG_IV, ARG_counter, ARG_segment_size };
  static const mp_arg_t allowed_args[] = {
      {MP_QSTR_key, MP_ARG_OBJ | MP_ARG_REQUIRED},
      {MP_QSTR_mode, MP_ARG_INT, {.u_int = AES_MODE_ECB}},
      {MP_QSTR_IV, MP_ARG_OBJ},
      {MP_QSTR_counter, MP_ARG_OBJ},
      {MP_QSTR_segment_size, MP_ARG_INT, {.u_int = 8}},
  };
  mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];

  mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args),
                   allowed_args, args);

  aesio_aes_obj_t *self = m_new_obj(aesio_aes_obj_t);
  self->base.type = &aesio_aes_type;

  mp_buffer_info_t bufinfo;

  const uint8_t *key = NULL;
  uint32_t key_length = 0;
  if (mp_get_buffer(args[ARG_key].u_obj, &bufinfo, MP_BUFFER_READ)) {
    if ((bufinfo.len != 16) && (bufinfo.len != 24) && (bufinfo.len != 32)) {
      mp_raise_TypeError(translate("Key must be 16, 24, or 32 bytes long"));
    }
    key = bufinfo.buf;
    key_length = bufinfo.len;
  } else {
    mp_raise_TypeError(translate("No key was specified"));
  }

  int mode = args[ARG_mode].u_int;
  switch (args[ARG_mode].u_int) {
  case AES_MODE_CBC:
  case AES_MODE_ECB:
  case AES_MODE_CTR:
    break;
  default:
    mp_raise_TypeError(translate("Requested AES mode is unsupported"));
  }

  // IV is required for CBC mode and is ignored for other modes.
  const uint8_t *iv = NULL;
  if (args[ARG_IV].u_obj != NULL &&
      mp_get_buffer(args[ARG_IV].u_obj, &bufinfo, MP_BUFFER_READ)) {
    if (bufinfo.len != AES_BLOCKLEN) {
      mp_raise_TypeError_varg(translate("IV must be %d bytes long"),
                              AES_BLOCKLEN);
    }
    iv = bufinfo.buf;
  }

  common_hal_aesio_aes_construct(self, key, key_length, iv, mode,
                                 args[ARG_counter].u_int);
  return MP_OBJ_FROM_PTR(self);
}

STATIC mp_obj_t aesio_aes_rekey(size_t n_args, const mp_obj_t *pos_args) {
  aesio_aes_obj_t *self = MP_OBJ_TO_PTR(pos_args[0]);

  mp_buffer_info_t bufinfo;
  mp_get_buffer_raise(pos_args[1], &bufinfo, MP_BUFFER_READ);
  const uint8_t *key = bufinfo.buf;
  size_t key_length = bufinfo.len;
  if (key == NULL) {
    mp_raise_ValueError(translate("No key was specified"));
  }
  if ((key_length != 16) && (key_length != 24) && (key_length != 32)) {
    mp_raise_TypeError(translate("Key must be 16, 24, or 32 bytes long"));
  }

  const uint8_t *iv = NULL;
  if (n_args > 2) {
    mp_get_buffer_raise(pos_args[2], &bufinfo, MP_BUFFER_READ);
    size_t iv_length = bufinfo.len;
    iv = (const uint8_t *)bufinfo.buf;
    if (iv_length != AES_BLOCKLEN) {
      mp_raise_TypeError_varg(translate("IV must be %d bytes long"),
                              AES_BLOCKLEN);
    }
  }

  common_hal_aesio_aes_rekey(self, key, key_length, iv);
  return mp_const_none;
}

MP_DEFINE_CONST_FUN_OBJ_VAR(aesio_aes_rekey_obj, 2, aesio_aes_rekey);

STATIC void validate_length(aesio_aes_obj_t *self, size_t src_length,
                            size_t dest_length) {
  if (src_length != dest_length) {
    mp_raise_ValueError(
        translate("Source and destination buffers must be the same length"));
  }

  switch (self->mode) {
  case AES_MODE_ECB:
    if (src_length != 16) {
      mp_raise_msg(&mp_type_ValueError,
                   translate("ECB only operates on 16 bytes at a time"));
    }
    break;
  case AES_MODE_CBC:
    if ((src_length & 15) != 0) {
      mp_raise_msg(&mp_type_ValueError,
                   translate("CBC blocks must be multiples of 16 bytes"));
    }
    break;
  case AES_MODE_CTR:
    break;
  }
}

//|     def encrypt_into(src, dest) -> None:
//|         """Encrypt the buffer from ``src`` into ``dest``.
//|
//|            For ECB mode, the buffers must be 16 bytes long.  For CBC mode, the
//|            buffers must be a multiple of 16 bytes, and must be equal length.  For
//|            CTX mode, there are no restrictions."""
//|         ...
//|
STATIC mp_obj_t aesio_aes_encrypt_into(mp_obj_t aesio_obj, mp_obj_t src,
                                       mp_obj_t dest) {
  if (!MP_OBJ_IS_TYPE(aesio_obj, &aesio_aes_type)) {
    mp_raise_TypeError_varg(translate("Expected a %q"), aesio_aes_type.name);
  }
  // Convert parameters into expected types.
  aesio_aes_obj_t *aes = MP_OBJ_TO_PTR(aesio_obj);

  mp_buffer_info_t srcbufinfo, destbufinfo;
  mp_get_buffer_raise(src, &srcbufinfo, MP_BUFFER_READ);
  mp_get_buffer_raise(dest, &destbufinfo, MP_BUFFER_WRITE);
  validate_length(aes, srcbufinfo.len, destbufinfo.len);

  memcpy(destbufinfo.buf, srcbufinfo.buf, srcbufinfo.len);

  common_hal_aesio_aes_encrypt(aes, (uint8_t *)destbufinfo.buf,
                               destbufinfo.len);
  return mp_const_none;
}

STATIC MP_DEFINE_CONST_FUN_OBJ_3(aesio_aes_encrypt_into_obj,
                                 aesio_aes_encrypt_into);

//|     def decrypt_into(src, dest) -> None:
//|
//|         """Decrypt the buffer from ``src`` into ``dest``.
//|            For ECB mode, the buffers must be 16 bytes long.  For CBC mode, the
//|            buffers must be a multiple of 16 bytes, and must be equal length.  For
//|            CTX mode, there are no restrictions."""
//|         ...
//|
STATIC mp_obj_t aesio_aes_decrypt_into(mp_obj_t aesio_obj, mp_obj_t src,
                                       mp_obj_t dest) {
  if (!MP_OBJ_IS_TYPE(aesio_obj, &aesio_aes_type)) {
    mp_raise_TypeError_varg(translate("Expected a %q"), aesio_aes_type.name);
  }
  // Convert parameters into expected types.
  aesio_aes_obj_t *aes = MP_OBJ_TO_PTR(aesio_obj);

  mp_buffer_info_t srcbufinfo, destbufinfo;
  mp_get_buffer_raise(src, &srcbufinfo, MP_BUFFER_READ);
  mp_get_buffer_raise(dest, &destbufinfo, MP_BUFFER_WRITE);
  validate_length(aes, srcbufinfo.len, destbufinfo.len);

  memcpy(destbufinfo.buf, srcbufinfo.buf, srcbufinfo.len);

  common_hal_aesio_aes_decrypt(aes, (uint8_t *)destbufinfo.buf,
                               destbufinfo.len);
  return mp_const_none;
}

STATIC MP_DEFINE_CONST_FUN_OBJ_3(aesio_aes_decrypt_into_obj,
                                 aesio_aes_decrypt_into);

STATIC mp_obj_t aesio_aes_get_mode(mp_obj_t aesio_obj) {
  if (!MP_OBJ_IS_TYPE(aesio_obj, &aesio_aes_type)) {
    mp_raise_TypeError_varg(translate("Expected a %q"), aesio_aes_type.name);
  }
  aesio_aes_obj_t *self = MP_OBJ_TO_PTR(aesio_obj);
  return MP_OBJ_NEW_SMALL_INT(self->mode);
}
MP_DEFINE_CONST_FUN_OBJ_1(aesio_aes_get_mode_obj, aesio_aes_get_mode);

STATIC mp_obj_t aesio_aes_set_mode(mp_obj_t aesio_obj, mp_obj_t mode_obj) {
  if (!MP_OBJ_IS_TYPE(aesio_obj, &aesio_aes_type)) {
    mp_raise_TypeError_varg(translate("Expected a %q"), aesio_aes_type.name);
  }
  aesio_aes_obj_t *self = MP_OBJ_TO_PTR(aesio_obj);

  int mode = mp_obj_get_int(mode_obj);
  switch (mode) {
  case AES_MODE_CBC:
  case AES_MODE_ECB:
  case AES_MODE_CTR:
    break;
  default:
    mp_raise_TypeError(translate("Requested AES mode is unsupported"));
  }

  common_hal_aesio_aes_set_mode(self, mode);
  return mp_const_none;
}
MP_DEFINE_CONST_FUN_OBJ_2(aesio_aes_set_mode_obj, aesio_aes_set_mode);

const mp_obj_property_t aesio_aes_mode_obj = {
    .base.type = &mp_type_property,
    .proxy = {(mp_obj_t)&aesio_aes_get_mode_obj,
              (mp_obj_t)&aesio_aes_set_mode_obj, (mp_obj_t)&mp_const_none_obj},
};

STATIC const mp_rom_map_elem_t aesio_locals_dict_table[] = {
    // Methods
    {MP_ROM_QSTR(MP_QSTR___name__), MP_OBJ_NEW_QSTR(MP_QSTR_AES)},
    {MP_ROM_QSTR(MP_QSTR_encrypt_into), (mp_obj_t)&aesio_aes_encrypt_into_obj},
    {MP_ROM_QSTR(MP_QSTR_decrypt_into), (mp_obj_t)&aesio_aes_decrypt_into_obj},
    {MP_ROM_QSTR(MP_QSTR_rekey), (mp_obj_t)&aesio_aes_rekey_obj},
    {MP_ROM_QSTR(MP_QSTR_mode), (mp_obj_t)&aesio_aes_mode_obj},
};
STATIC MP_DEFINE_CONST_DICT(aesio_locals_dict, aesio_locals_dict_table);

const mp_obj_type_t aesio_aes_type = {
    {&mp_type_type},
    .name = MP_QSTR_AES,
    .make_new = aesio_aes_make_new,
    .locals_dict = (mp_obj_dict_t *)&aesio_locals_dict,
};