libavb/avb_ops.h

/*
 * Copyright (C) 2016 The Android Open Source Project
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use, copy,
 * modify, merge, publish, distribute, sublicense, and/or sell copies
 * of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#if !defined(AVB_INSIDE_LIBAVB_H) && !defined(AVB_COMPILATION)
#error "Never include this file directly, include libavb.h instead."
#endif

#ifndef AVB_OPS_H_
#define AVB_OPS_H_

#include "avb_sysdeps.h"

#ifdef __cplusplus
extern "C" {
#endif

/* Return codes used for I/O operations.
 *
 * AVB_IO_RESULT_OK is returned if the requested operation was
 * successful.
 *
 * AVB_IO_RESULT_ERROR_IO is returned if the underlying hardware (disk
 * or other subsystem) encountered an I/O error.
 *
 * AVB_IO_RESULT_ERROR_OOM is returned if unable to allocate memory.
 *
 * AVB_IO_RESULT_ERROR_NO_SUCH_PARTITION is returned if the requested
 * partition does not exist.
 *
 * AVB_IO_RESULT_ERROR_RANGE_OUTSIDE_PARTITION is returned if the
 * range of bytes requested to be read or written is outside the range
 * of the partition.
 */
typedef enum {
  AVB_IO_RESULT_OK,
  AVB_IO_RESULT_ERROR_OOM,
  AVB_IO_RESULT_ERROR_IO,
  AVB_IO_RESULT_ERROR_NO_SUCH_PARTITION,
  AVB_IO_RESULT_ERROR_RANGE_OUTSIDE_PARTITION
} AvbIOResult;

struct AvbOps;
typedef struct AvbOps AvbOps;

/* High-level operations/functions/methods that are platform
 * dependent.
 */
struct AvbOps {
  /* Reads |num_bytes| from offset |offset| from partition with name
   * |partition| (NUL-terminated UTF-8 string). If |offset| is
   * negative, its absolute value should be interpreted as the number
   * of bytes from the end of the partition.
   *
   * This function returns AVB_IO_RESULT_ERROR_NO_SUCH_PARTITION if
   * there is no partition with the given name,
   * AVB_IO_RESULT_ERROR_RANGE_OUTSIDE_PARTITION if the requested
   * |offset| is outside the partition, and AVB_IO_RESULT_ERROR_IO if
   * there was an I/O error from the underlying I/O subsystem.  If the
   * operation succeeds as requested AVB_IO_RESULT_OK is returned and
   * the data is available in |buffer|.
   *
   * The only time partial I/O may occur is if reading beyond the end
   * of the partition. In this case the value returned in
   * |out_num_read| may be smaller than |num_bytes|.
   */
  AvbIOResult (*read_from_partition)(AvbOps* ops, const char* partition,
                                     int64_t offset, size_t num_bytes,
                                     void* buffer, size_t* out_num_read);

  /* Writes |num_bytes| from |bffer| at offset |offset| to partition
   * with name |partition| (NUL-terminated UTF-8 string). If |offset|
   * is negative, its absolute value should be interpreted as the
   * number of bytes from the end of the partition.
   *
   * This function returns AVB_IO_RESULT_ERROR_NO_SUCH_PARTITION if
   * there is no partition with the given name,
   * AVB_IO_RESULT_ERROR_RANGE_OUTSIDE_PARTITION if the requested
   * byterange goes outside the partition, and AVB_IO_RESULT_ERROR_IO
   * if there was an I/O error from the underlying I/O subsystem.  If
   * the operation succeeds as requested AVB_IO_RESULT_OK is
   * returned.
   *
   * This function never does any partial I/O, it either transfers all
   * of the requested bytes or returns an error.
   */
  AvbIOResult (*write_to_partition)(AvbOps* ops, const char* partition,
                                    int64_t offset, size_t num_bytes,
                                    const void* buffer);

  /* Checks if the given public key used to sign the 'vbmeta'
   * partition is trusted. Boot loaders typically compare this with
   * embedded key material generated with 'avbtool
   * extract_public_key'.
   *
   * If AVB_IO_RESULT_OK is returned then |out_is_trusted| is set -
   * true if trusted or false if untrusted.
   */
  AvbIOResult (*validate_vbmeta_public_key)(AvbOps* ops,
                                            const uint8_t* public_key_data,
                                            size_t public_key_length,
                                            bool* out_is_trusted);

  /* Gets the rollback index corresponding to the slot given by
   * |rollback_index_slot|. The value is returned in
   * |out_rollback_index|. Returns AVB_IO_RESULT_OK if the rollback
   * index was retrieved, otherwise an error code.
   *
   * A device may have a limited amount of rollback index slots (say,
   * one or four) so may error out if |rollback_index_slot| exceeds
   * this number.
   */
  AvbIOResult (*read_rollback_index)(AvbOps* ops, size_t rollback_index_slot,
                                     uint64_t* out_rollback_index);

  /* Sets the rollback index corresponding to the slot given by
   * |rollback_index_slot| to |rollback_index|. Returns
   * AVB_IO_RESULT_OK if the rollback index was set, otherwise an
   * error code.
   *
   * A device may have a limited amount of rollback index slots (say,
   * one or four) so may error out if |rollback_index_slot| exceeds
   * this number.
   */
  AvbIOResult (*write_rollback_index)(AvbOps* ops, size_t rollback_index_slot,
                                      uint64_t rollback_index);

  /* Gets whether the device is unlocked. The value is returned in
   * |out_is_unlocked| (true if unlocked, false otherwise). Returns
   * AVB_IO_RESULT_OK if the state was retrieved, otherwise an error
   * code.
   */
  AvbIOResult (*read_is_device_unlocked)(AvbOps* ops, bool* out_is_unlocked);

  /* Gets the unique partition GUID for a partition with name in
   * |partition| (NUL-terminated UTF-8 string). The GUID is copied as
   * a string into |guid_buf| of size |guid_buf_size| and will be NUL
   * terminated. The string must be lower-case and properly
   * hyphenated. For example:
   *
   *  527c1c6d-6361-4593-8842-3c78fcd39219
   *
   * Returns AVB_IO_RESULT_OK on success, otherwise an error code.
   */
  AvbIOResult (*get_unique_guid_for_partition)(AvbOps* ops,
                                               const char* partition,
                                               char* guid_buf,
                                               size_t guid_buf_size);
};

#ifdef __cplusplus
}
#endif

#endif /* AVB_OPS_H_ */