lib/libavb/avb_slot_verify.h

/* SPDX-License-Identifier: MIT */
/*
 * Copyright (C) 2016 The Android Open Source Project
 */

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

#ifndef AVB_SLOT_VERIFY_H_
#define AVB_SLOT_VERIFY_H_

#include "avb_ops.h"
#include "avb_vbmeta_image.h"

#ifdef __cplusplus
extern "C" {
#endif

/* Return codes used in avb_slot_verify(), see that function for
 * documentation for each field.
 *
 * Use avb_slot_verify_result_to_string() to get a textual
 * representation usable for error/debug output.
 */
typedef enum {
  AVB_SLOT_VERIFY_RESULT_OK,
  AVB_SLOT_VERIFY_RESULT_ERROR_OOM,
  AVB_SLOT_VERIFY_RESULT_ERROR_IO,
  AVB_SLOT_VERIFY_RESULT_ERROR_VERIFICATION,
  AVB_SLOT_VERIFY_RESULT_ERROR_ROLLBACK_INDEX,
  AVB_SLOT_VERIFY_RESULT_ERROR_PUBLIC_KEY_REJECTED,
  AVB_SLOT_VERIFY_RESULT_ERROR_INVALID_METADATA,
  AVB_SLOT_VERIFY_RESULT_ERROR_UNSUPPORTED_VERSION,
  AVB_SLOT_VERIFY_RESULT_ERROR_INVALID_ARGUMENT
} AvbSlotVerifyResult;

/* Various error handling modes for when verification fails using a
 * hashtree at runtime inside the HLOS.
 *
 * AVB_HASHTREE_ERROR_MODE_RESTART_AND_INVALIDATE means that the OS
 * will invalidate the current slot and restart.
 *
 * AVB_HASHTREE_ERROR_MODE_RESTART means that the OS will restart.
 *
 * AVB_HASHTREE_ERROR_MODE_EIO means that an EIO error will be
 * returned to applications.
 *
 * AVB_HASHTREE_ERROR_MODE_LOGGING means that errors will be logged
 * and corrupt data may be returned to applications. This mode should
 * be used ONLY for diagnostics and debugging. It cannot be used
 * unless AVB_SLOT_VERIFY_FLAGS_ALLOW_VERIFICATION_ERROR is also
 * used.
 *
 * AVB_HASHTREE_ERROR_MODE_MANAGED_RESTART_AND_EIO means that either
 * AVB_HASHTREE_ERROR_MODE_RESTART or AVB_HASHTREE_ERROR_MODE_EIO is used
 * depending on state. This mode implements a state machine whereby
 * AVB_HASHTREE_ERROR_MODE_RESTART is used by default and when
 * AVB_SLOT_VERIFY_FLAGS_RESTART_CAUSED_BY_HASHTREE_CORRUPTION is passed the
 * mode transitions to AVB_HASHTREE_ERROR_MODE_EIO. When a new OS has been
 * detected the device transitions back to the AVB_HASHTREE_ERROR_MODE_RESTART
 * mode. To do this persistent storage is needed - specifically this means that
 * the passed in AvbOps will need to have the read_persistent_value() and
 * write_persistent_value() operations implemented. The name of the persistent
 * value used is "avb.managed_verity_mode" and 32 bytes of storage is needed.
 */
typedef enum {
  AVB_HASHTREE_ERROR_MODE_RESTART_AND_INVALIDATE,
  AVB_HASHTREE_ERROR_MODE_RESTART,
  AVB_HASHTREE_ERROR_MODE_EIO,
  AVB_HASHTREE_ERROR_MODE_LOGGING,
  AVB_HASHTREE_ERROR_MODE_MANAGED_RESTART_AND_EIO
} AvbHashtreeErrorMode;

/* Flags that influence how avb_slot_verify() works.
 *
 * If AVB_SLOT_VERIFY_FLAGS_ALLOW_VERIFICATION_ERROR is NOT set then
 * avb_slot_verify() will bail out as soon as an error is encountered
 * and |out_data| is set only if AVB_SLOT_VERIFY_RESULT_OK is
 * returned.
 *
 * Otherwise if AVB_SLOT_VERIFY_FLAGS_ALLOW_VERIFICATION_ERROR is set
 * avb_slot_verify() will continue verification efforts and |out_data|
 * is also set if AVB_SLOT_VERIFY_RESULT_ERROR_PUBLIC_KEY_REJECTED,
 * AVB_SLOT_VERIFY_RESULT_ERROR_VERIFICATION, or
 * AVB_SLOT_VERIFY_RESULT_ERROR_ROLLBACK_INDEX is returned. It is
 * undefined which error is returned if more than one distinct error
 * is encountered. It is guaranteed that AVB_SLOT_VERIFY_RESULT_OK is
 * returned if, and only if, there are no errors. This mode is needed
 * to boot valid but unverified slots when the device is unlocked.
 *
 * Also, if AVB_SLOT_VERIFY_FLAGS_ALLOW_VERIFICATION_ERROR is set the
 * contents loaded from |requested_partition| will be the contents of
 * the entire partition instead of just the size specified in the hash
 * descriptor.
 *
 * The AVB_SLOT_VERIFY_FLAGS_RESTART_CAUSED_BY_HASHTREE_CORRUPTION flag
 * should be set if using AVB_HASHTREE_ERROR_MODE_MANAGED_RESTART_AND_EIO
 * and the reason the boot loader is running is because the device
 * was restarted by the dm-verity driver.
 *
 * If the AVB_SLOT_VERIFY_FLAGS_NO_VBMETA_PARTITION flag is set then
 * data won't be loaded from the "vbmeta" partition and the
 * |validate_vbmeta_public_key| operation is never called. Instead, the
 * vbmeta structs in |requested_partitions| are loaded and processed and the
 * |validate_public_key_for_partition| operation is called for each of these
 * vbmeta structs. This flag is useful when booting into recovery on a device
 * not using A/B - see section "Booting into recovery" in README.md for
 * more information.
 */
typedef enum {
  AVB_SLOT_VERIFY_FLAGS_NONE = 0,
  AVB_SLOT_VERIFY_FLAGS_ALLOW_VERIFICATION_ERROR = (1 << 0),
  AVB_SLOT_VERIFY_FLAGS_RESTART_CAUSED_BY_HASHTREE_CORRUPTION = (1 << 1),
  AVB_SLOT_VERIFY_FLAGS_NO_VBMETA_PARTITION = (1 << 2),
} AvbSlotVerifyFlags;

/* Get a textual representation of |result|. */
const char* avb_slot_verify_result_to_string(AvbSlotVerifyResult result);

/* Maximum number of rollback index locations supported. */
#define AVB_MAX_NUMBER_OF_ROLLBACK_INDEX_LOCATIONS 32

/* AvbPartitionData contains data loaded from partitions when using
 * avb_slot_verify(). The |partition_name| field contains the name of
 * the partition (without A/B suffix), |data| points to the loaded
 * data which is |data_size| bytes long. If |preloaded| is set to true,
 * this structure dose not own |data|. The caller of |avb_slot_verify|
 * needs to make sure that the preloaded data outlives this
 * |AvbPartitionData| structure.
 *
 * Note that this is strictly less than the partition size - it's only
 * the image stored there, not the entire partition nor any of the
 * metadata.
 */
typedef struct {
  char* partition_name;
  uint8_t* data;
  size_t data_size;
  bool preloaded;
} AvbPartitionData;

/* AvbVBMetaData contains a vbmeta struct loaded from a partition when
 * using avb_slot_verify(). The |partition_name| field contains the
 * name of the partition (without A/B suffix), |vbmeta_data| points to
 * the loaded data which is |vbmeta_size| bytes long.
 *
 * The |verify_result| field contains the result of
 * avb_vbmeta_image_verify() on the data. This is guaranteed to be
 * AVB_VBMETA_VERIFY_RESULT_OK for all vbmeta images if
 * avb_slot_verify() returns AVB_SLOT_VERIFY_RESULT_OK.
 *
 * You can use avb_descriptor_get_all(), avb_descriptor_foreach(), and
 * avb_vbmeta_image_header_to_host_byte_order() with this data.
 */
typedef struct {
  char* partition_name;
  uint8_t* vbmeta_data;
  size_t vbmeta_size;
  AvbVBMetaVerifyResult verify_result;
} AvbVBMetaData;

/* AvbSlotVerifyData contains data needed to boot a particular slot
 * and is returned by avb_slot_verify() if partitions in a slot are
 * successfully verified.
 *
 * All data pointed to by this struct - including data in each item in
 * the |partitions| array - will be freed when the
 * avb_slot_verify_data_free() function is called.
 *
 * The |ab_suffix| field is the copy of the of |ab_suffix| field
 * passed to avb_slot_verify(). It is the A/B suffix of the slot. This
 * value includes the leading underscore - typical values are "" (if
 * no slots are in use), "_a" (for the first slot), and "_b" (for the
 * second slot).
 *
 * The VBMeta images that were checked are available in the
 * |vbmeta_images| field. The field |num_vbmeta_images| contains the
 * number of elements in this array. The first element -
 * vbmeta_images[0] - is guaranteed to be from the partition with the
 * top-level vbmeta struct. This is usually the "vbmeta" partition in
 * the requested slot but if there is no "vbmeta" partition it can
 * also be the "boot" partition.
 *
 * The partitions loaded and verified from from the slot are
 * accessible in the |loaded_partitions| array. The field
 * |num_loaded_partitions| contains the number of elements in this
 * array. The order of partitions in this array may not necessarily be
 * the same order as in the passed-in |requested_partitions| array.
 *
 * Rollback indexes for the verified slot are stored in the
 * |rollback_indexes| field. Note that avb_slot_verify() will NEVER
 * modify stored_rollback_index[n] locations e.g. it will never use
 * the write_rollback_index() AvbOps operation. Instead it is the job
 * of the caller of avb_slot_verify() to do this based on e.g. A/B
 * policy and other factors. See libavb_ab/avb_ab_flow.c for an
 * example of how to do this.
 *
 * The |cmdline| field is a NUL-terminated string in UTF-8 resulting
 * from concatenating all |AvbKernelCmdlineDescriptor| and then
 * performing proper substitution of the variables
 * $(ANDROID_SYSTEM_PARTUUID), $(ANDROID_BOOT_PARTUUID), and
 * $(ANDROID_VBMETA_PARTUUID) using the
 * get_unique_guid_for_partition() operation in |AvbOps|. Additionally
 * $(ANDROID_VERITY_MODE) will be replaced with the proper dm-verity
 * option depending on the value of |hashtree_error_mode|.
 *
 * Additionally, the |cmdline| field will have the following kernel
 * command-line options set (unless verification is disabled, see
 * below):
 *
 *   androidboot.veritymode: This is set to 'disabled' if the
 *   AVB_VBMETA_IMAGE_FLAGS_HASHTREE_DISABLED flag is set in top-level
 *   vbmeta struct. Otherwise it is set to 'enforcing' if the
 *   passed-in hashtree error mode is AVB_HASHTREE_ERROR_MODE_RESTART
 *   or AVB_HASHTREE_ERROR_MODE_RESTART_AND_INVALIDATE, 'eio' if it's
 *   set to AVB_HASHTREE_ERROR_MODE_EIO, and 'logging' if it's set to
 *   AVB_HASHTREE_ERROR_MODE_LOGGING.
 *
 *   androidboot.veritymode.managed: This is set to 'yes' only
 *   if hashtree validation isn't disabled and the passed-in hashtree
 *   error mode is AVB_HASHTREE_ERROR_MODE_MANAGED_RESTART_AND_EIO.
 *
 *   androidboot.vbmeta.invalidate_on_error: This is set to 'yes' only
 *   if hashtree validation isn't disabled and the passed-in hashtree
 *   error mode is AVB_HASHTREE_ERROR_MODE_RESTART_AND_INVALIDATE.
 *
 *   androidboot.vbmeta.device_state: set to "locked" or "unlocked"
 *   depending on the result of the result of AvbOps's
 *   read_is_unlocked() function.
 *
 *   androidboot.vbmeta.{hash_alg, size, digest}: Will be set to
 *   the digest of all images in |vbmeta_images|.
 *
 *   androidboot.vbmeta.device: This is set to the value
 *   PARTUUID=$(ANDROID_VBMETA_PARTUUID) before substitution so it
 *   will end up pointing to the vbmeta partition for the verified
 *   slot. If there is no vbmeta partition it will point to the boot
 *   partition of the verified slot. If the flag
 *   AVB_SLOT_VERIFY_FLAGS_NO_VBMETA_PARTITION is used, this is not
 *   set.
 *
 *   androidboot.vbmeta.avb_version: This is set to the decimal value
 *   of AVB_VERSION_MAJOR followed by a dot followed by the decimal
 *   value of AVB_VERSION_MINOR, for example "1.0" or "1.4". This
 *   version number represents the vbmeta file format version
 *   supported by libavb copy used in the boot loader. This is not
 *   necessarily the same version number of the on-disk metadata for
 *   the slot that was verified.
 *
 * Note that androidboot.slot_suffix is not set in the |cmdline| field
 * in |AvbSlotVerifyData| - you will have to set this yourself.
 *
 * If the |AVB_VBMETA_IMAGE_FLAGS_VERIFICATION_DISABLED| flag is set
 * in the top-level vbmeta struct then only the top-level vbmeta
 * struct is verified and descriptors will not processed. The return
 * value will be set accordingly (if this flag is set via 'avbctl
 * disable-verification' then the return value will be
 * |AVB_SLOT_VERIFY_RESULT_ERROR_VERIFICATION|) and
 * |AvbSlotVerifyData| is returned. Additionally all partitions in the
 * |requested_partitions| are loaded and the |cmdline| field is set to
 * "root=PARTUUID=$(ANDROID_SYSTEM_PARTUUID)" and the GUID for the
 * appropriate system partition is substituted in. Note that none of
 * the androidboot.* options mentioned above will be set.
 *
 * The |resolved_hashtree_error_mode| is the the value of the passed
 * avb_slot_verify()'s |hashtree_error_mode| parameter except that it never has
 * the value AVB_HASHTREE_ERROR_MODE_MANAGED_RESTART_AND_EIO. If this value was
 * passed in, then the restart/eio state machine is used resulting in
 * |resolved_hashtree_error_mode| being set to either
 * AVB_HASHTREE_ERROR_MODE_RESTART or AVB_HASHTREE_ERROR_MODE_EIO.  If set to
 * AVB_HASHTREE_ERROR_MODE_EIO the boot loader should present a RED warning
 * screen for the user to click through before continuing to boot.
 *
 * This struct may grow in the future without it being considered an
 * ABI break.
 */
typedef struct {
  char* ab_suffix;
  AvbVBMetaData* vbmeta_images;
  size_t num_vbmeta_images;
  AvbPartitionData* loaded_partitions;
  size_t num_loaded_partitions;
  char* cmdline;
  uint64_t rollback_indexes[AVB_MAX_NUMBER_OF_ROLLBACK_INDEX_LOCATIONS];
  AvbHashtreeErrorMode resolved_hashtree_error_mode;
} AvbSlotVerifyData;

/* Calculates a digest of all vbmeta images in |data| using
 * the digest indicated by |digest_type|. Stores the result
 * in |out_digest| which must be large enough to hold a digest
 * of the requested type.
 */
void avb_slot_verify_data_calculate_vbmeta_digest(AvbSlotVerifyData* data,
                                                  AvbDigestType digest_type,
                                                  uint8_t* out_digest);

/* Frees a |AvbSlotVerifyData| including all data it points to. */
void avb_slot_verify_data_free(AvbSlotVerifyData* data);

/* Performs a full verification of the slot identified by |ab_suffix|
 * and load and verify the contents of the partitions whose name is in
 * the NULL-terminated string array |requested_partitions| (each
 * partition must use hash verification). If not using A/B, pass an
 * empty string (e.g. "", not NULL) for |ab_suffix|. This parameter
 * must include the leading underscore, for example "_a" should be
 * used to refer to the first slot.
 *
 * Typically the |requested_partitions| array only contains a single
 * item for the boot partition, 'boot'.
 *
 * Verification includes loading and verifying data from the 'vbmeta',
 * the requested hash partitions, and possibly other partitions (with
 * |ab_suffix| appended), inspecting rollback indexes, and checking if
 * the public key used to sign the data is acceptable. The functions
 * in |ops| will be used to do this.
 *
 * If |out_data| is not NULL, it will be set to a newly allocated
 * |AvbSlotVerifyData| struct containing all the data needed to
 * actually boot the slot. This data structure should be freed with
 * avb_slot_verify_data_free() when you are done with it. See below
 * for when this is returned.
 *
 * The |flags| parameter is used to influence the semantics of
 * avb_slot_verify() - for example the
 * AVB_SLOT_VERIFY_FLAGS_ALLOW_VERIFICATION_ERROR flag can be used to
 * ignore verification errors which is something needed in the
 * UNLOCKED state. See the AvbSlotVerifyFlags enumeration for details.
 *
 * The |hashtree_error_mode| parameter should be set to the desired error
 * handling mode. See the AvbHashtreeErrorMode enumeration for details.
 *
 * Also note that |out_data| is never set if
 * AVB_SLOT_VERIFY_RESULT_ERROR_OOM, AVB_SLOT_VERIFY_RESULT_ERROR_IO,
 * or AVB_SLOT_VERIFY_RESULT_ERROR_INVALID_METADATA is returned.
 *
 * AVB_SLOT_VERIFY_RESULT_OK is returned if everything is verified
 * correctly and all public keys are accepted.
 *
 * AVB_SLOT_VERIFY_RESULT_ERROR_PUBLIC_KEY_REJECTED is returned if
 * everything is verified correctly out but one or more public keys
 * are not accepted. This includes the case where integrity data is
 * not signed.
 *
 * AVB_SLOT_VERIFY_RESULT_ERROR_OOM is returned if unable to
 * allocate memory.
 *
 * AVB_SLOT_VERIFY_RESULT_ERROR_IO is returned if an I/O error
 * occurred while trying to load data or get a rollback index.
 *
 * AVB_SLOT_VERIFY_RESULT_ERROR_VERIFICATION is returned if the data
 * did not verify, e.g. the digest didn't match or signature checks
 * failed.
 *
 * AVB_SLOT_VERIFY_RESULT_ERROR_ROLLBACK_INDEX is returned if a
 * rollback index was less than its stored value.
 *
 * AVB_SLOT_VERIFY_RESULT_ERROR_INVALID_METADATA is returned if some
 * of the metadata is invalid or inconsistent.
 *
 * AVB_SLOT_VERIFY_RESULT_ERROR_UNSUPPORTED_VERSION is returned if
 * some of the metadata requires a newer version of libavb than what
 * is in use.
 *
 * AVB_SLOT_VERIFY_RESULT_ERROR_INVALID_ARGUMENT is returned if the
 * caller passed invalid parameters, for example trying to use
 * AVB_HASHTREE_ERROR_MODE_LOGGING without
 * AVB_SLOT_VERIFY_FLAGS_ALLOW_VERIFICATION_ERROR.
 */
AvbSlotVerifyResult avb_slot_verify(AvbOps* ops,
                                    const char* const* requested_partitions,
                                    const char* ab_suffix,
                                    AvbSlotVerifyFlags flags,
                                    AvbHashtreeErrorMode hashtree_error_mode,
                                    AvbSlotVerifyData** out_data);

#ifdef __cplusplus
}
#endif

#endif /* AVB_SLOT_VERIFY_H_ */