1 /*
2  * Copyright (C) 2016 The Android Open Source Project
3  *
4  * Permission is hereby granted, free of charge, to any person
5  * obtaining a copy of this software and associated documentation
6  * files (the "Software"), to deal in the Software without
7  * restriction, including without limitation the rights to use, copy,
8  * modify, merge, publish, distribute, sublicense, and/or sell copies
9  * of the Software, and to permit persons to whom the Software is
10  * furnished to do so, subject to the following conditions:
11  *
12  * The above copyright notice and this permission notice shall be
13  * included in all copies or substantial portions of the Software.
14  *
15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
16  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
17  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
18  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
19  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
20  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
21  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
22  * SOFTWARE.
23  */
24 
25 #if !defined(AVB_INSIDE_LIBAVB_H) && !defined(AVB_COMPILATION)
26 #error "Never include this file directly, include libavb.h instead."
27 #endif
28 
29 #ifndef AVB_DESCRIPTOR_H_
30 #define AVB_DESCRIPTOR_H_
31 
32 #include "avb_sysdeps.h"
33 
34 #ifdef __cplusplus
35 extern "C" {
36 #endif
37 
38 /* Well-known descriptor tags.
39  *
40  * AVB_DESCRIPTOR_TAG_PROPERTY: see |AvbPropertyDescriptor| struct.
41  * AVB_DESCRIPTOR_TAG_HASHTREE: see |AvbHashtreeDescriptor| struct.
42  * AVB_DESCRIPTOR_TAG_HASH: see |AvbHashDescriptor| struct.
43  * AVB_DESCRIPTOR_TAG_KERNEL_CMDLINE: see |AvbKernelCmdlineDescriptor| struct.
44  * AVB_DESCRIPTOR_TAG_CHAIN_PARTITION: see |AvbChainPartitionDescriptor| struct.
45  */
46 typedef enum {
47   AVB_DESCRIPTOR_TAG_PROPERTY,
48   AVB_DESCRIPTOR_TAG_HASHTREE,
49   AVB_DESCRIPTOR_TAG_HASH,
50   AVB_DESCRIPTOR_TAG_KERNEL_CMDLINE,
51   AVB_DESCRIPTOR_TAG_CHAIN_PARTITION,
52 } AvbDescriptorTag;
53 
54 /* The header for a serialized descriptor.
55  *
56  * A descriptor always have two fields, a |tag| (denoting its type,
57  * see the |AvbDescriptorTag| enumeration) and the size of the bytes
58  * following, |num_bytes_following|.
59  *
60  * For padding, |num_bytes_following| is always a multiple of 8.
61  */
62 typedef struct AvbDescriptor {
63   uint64_t tag;
64   uint64_t num_bytes_following;
65 } AVB_ATTR_PACKED AvbDescriptor;
66 
67 /* Copies |src| to |dest| and validates, byte-swapping fields in the
68  * process if needed. Returns true if valid, false if invalid.
69  *
70  * Data following the struct is not validated nor copied.
71  */
72 bool avb_descriptor_validate_and_byteswap(
73     const AvbDescriptor* src, AvbDescriptor* dest) AVB_ATTR_WARN_UNUSED_RESULT;
74 
75 /* Signature for callback function used in avb_descriptor_foreach().
76  * The passed in descriptor is given by |descriptor| and the
77  * |user_data| passed to avb_descriptor_foreach() function is in
78  * |user_data|. Return true to continue iterating, false to stop
79  * iterating.
80  *
81  * Note that |descriptor| points into the image passed to
82  * avb_descriptor_foreach() - all fields need to be byteswapped!
83  */
84 typedef bool AvbDescriptorForeachFunc(const AvbDescriptor* descriptor,
85                                       void* user_data);
86 
87 /* Convenience function to iterate over all descriptors in an vbmeta
88  * image.
89  *
90  * The function given by |foreach_func| will be called for each
91  * descriptor. The given function should return true to continue
92  * iterating, false to stop.
93  *
94  * The |user_data| parameter will be passed to |foreach_func|.
95  *
96  * Returns false if the iteration was short-circuited, that is if
97  * an invocation of |foreach_func| returned false.
98  *
99  * Before using this function, you MUST verify |image_data| with
100  * avb_vbmeta_image_verify() and reject it unless it's signed by a known
101  * good public key. Additionally, |image_data| must be word-aligned.
102  */
103 bool avb_descriptor_foreach(const uint8_t* image_data,
104                             size_t image_size,
105                             AvbDescriptorForeachFunc foreach_func,
106                             void* user_data);
107 
108 /* Gets all descriptors in a vbmeta image.
109  *
110  * The return value is a NULL-pointer terminated array of
111  * AvbDescriptor pointers. Free with avb_free() when you are done with
112  * it. If |out_num_descriptors| is non-NULL, the number of descriptors
113  * will be returned there.
114  *
115  * Note that each AvbDescriptor pointer in the array points into
116  * |image_data| - all fields need to be byteswapped!
117  *
118  * Before using this function, you MUST verify |image_data| with
119  * avb_vbmeta_image_verify() and reject it unless it's signed by a known
120  * good public key. Additionally, |image_data| must be word-aligned.
121  */
122 const AvbDescriptor** avb_descriptor_get_all(const uint8_t* image_data,
123                                              size_t image_size,
124                                              size_t* out_num_descriptors)
125     AVB_ATTR_WARN_UNUSED_RESULT;
126 
127 #ifdef __cplusplus
128 }
129 #endif
130 
131 #endif /* AVB_DESCRIPTOR_H_ */
132