xref: /openbmc/u-boot/lib/libavb/avb_property_descriptor.h (revision 897a1d947e7e50cf03113dcbe505ffb63dce45a9)
1  /* SPDX-License-Identifier: MIT */
2  /*
3   * Copyright (C) 2016 The Android Open Source Project
4   */
5  
6  #if !defined(AVB_INSIDE_LIBAVB_H) && !defined(AVB_COMPILATION)
7  #error "Never include this file directly, include libavb.h instead."
8  #endif
9  
10  #ifndef AVB_PROPERTY_DESCRIPTOR_H_
11  #define AVB_PROPERTY_DESCRIPTOR_H_
12  
13  #include "avb_descriptor.h"
14  
15  #ifdef __cplusplus
16  extern "C" {
17  #endif
18  
19  /* A descriptor for properties (free-form key/value pairs).
20   *
21   * Following this struct are |key_num_bytes| bytes of key data,
22   * followed by a NUL byte, then |value_num_bytes| bytes of value data,
23   * followed by a NUL byte and then enough padding to make the combined
24   * size a multiple of 8.
25   */
26  typedef struct AvbPropertyDescriptor {
27    AvbDescriptor parent_descriptor;
28    uint64_t key_num_bytes;
29    uint64_t value_num_bytes;
30  } AVB_ATTR_PACKED AvbPropertyDescriptor;
31  
32  /* Copies |src| to |dest| and validates, byte-swapping fields in the
33   * process if needed. Returns true if valid, false if invalid.
34   *
35   * Data following the struct is not validated nor copied.
36   */
37  bool avb_property_descriptor_validate_and_byteswap(
38      const AvbPropertyDescriptor* src,
39      AvbPropertyDescriptor* dest) AVB_ATTR_WARN_UNUSED_RESULT;
40  
41  /* Convenience function for looking up the value for a property with
42   * name |key| in a vbmeta image. If |key_size| is 0, |key| must be
43   * NUL-terminated.
44   *
45   * The |image_data| parameter must be a pointer to a vbmeta image of
46   * size |image_size|.
47   *
48   * This function returns a pointer to the value inside the passed-in
49   * image or NULL if not found. Note that the value is always
50   * guaranteed to be followed by a NUL byte.
51   *
52   * If the value was found and |out_value_size| is not NULL, the size
53   * of the value is returned there.
54   *
55   * This function is O(n) in number of descriptors so if you need to
56   * look up a lot of values, you may want to build a more efficient
57   * lookup-table by manually walking all descriptors using
58   * avb_descriptor_foreach().
59   *
60   * Before using this function, you MUST verify |image_data| with
61   * avb_vbmeta_image_verify() and reject it unless it's signed by a
62   * known good public key.
63   */
64  const char* avb_property_lookup(const uint8_t* image_data,
65                                  size_t image_size,
66                                  const char* key,
67                                  size_t key_size,
68                                  size_t* out_value_size)
69      AVB_ATTR_WARN_UNUSED_RESULT;
70  
71  /* Like avb_property_lookup() but parses the intial portions of the
72   * value as an unsigned 64-bit integer. Both decimal and hexadecimal
73   * representations (e.g. "0x2a") are supported. Returns false on
74   * failure and true on success. On success, the parsed value is
75   * returned in |out_value|.
76   */
77  bool avb_property_lookup_uint64(const uint8_t* image_data,
78                                  size_t image_size,
79                                  const char* key,
80                                  size_t key_size,
81                                  uint64_t* out_value)
82      AVB_ATTR_WARN_UNUSED_RESULT;
83  
84  #ifdef __cplusplus
85  }
86  #endif
87  
88  #endif /* AVB_PROPERTY_DESCRIPTOR_H_ */
89