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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_CRYPTO_H_
30 #define AVB_CRYPTO_H_
31 
32 #include "avb_sysdeps.h"
33 
34 #ifdef __cplusplus
35 extern "C" {
36 #endif
37 
38 /* Size of a RSA-2048 signature. */
39 #define AVB_RSA2048_NUM_BYTES 256
40 
41 /* Size of a RSA-4096 signature. */
42 #define AVB_RSA4096_NUM_BYTES 512
43 
44 /* Size of a RSA-8192 signature. */
45 #define AVB_RSA8192_NUM_BYTES 1024
46 
47 /* Size in bytes of a SHA-1 digest. */
48 #define AVB_SHA1_DIGEST_SIZE 20
49 
50 /* Size in bytes of a SHA-256 digest. */
51 #define AVB_SHA256_DIGEST_SIZE 32
52 
53 /* Size in bytes of a SHA-512 digest. */
54 #define AVB_SHA512_DIGEST_SIZE 64
55 
56 /* Possible digest types supported by libavb routines. */
57 typedef enum {
58   AVB_DIGEST_TYPE_SHA256,
59   AVB_DIGEST_TYPE_SHA512,
60 } AvbDigestType;
61 
62 /* Algorithms that can be used in the vbmeta image for
63  * verification. An algorithm consists of a hash type and a signature
64  * type.
65  *
66  * The data used to calculate the hash is the three blocks mentioned
67  * in the documentation for |AvbVBMetaImageHeader| except for the data
68  * in the "Authentication data" block.
69  *
70  * For signatures with RSA keys, PKCS v1.5 padding is used. The public
71  * key data is stored in the auxiliary data block, see
72  * |AvbRSAPublicKeyHeader| for the serialization format.
73  *
74  * Each algorithm type is described below:
75  *
76  * AVB_ALGORITHM_TYPE_NONE: There is no hash, no signature of the
77  * data, and no public key. The data cannot be verified. The fields
78  * |hash_size|, |signature_size|, and |public_key_size| must be zero.
79  *
80  * AVB_ALGORITHM_TYPE_SHA256_RSA2048: The hash function used is
81  * SHA-256, resulting in 32 bytes of hash digest data. This hash is
82  * signed with a 2048-bit RSA key. The field |hash_size| must be 32,
83  * |signature_size| must be 256, and the public key data must have
84  * |key_num_bits| set to 2048.
85  *
86  * AVB_ALGORITHM_TYPE_SHA256_RSA4096: Like above, but only with
87  * a 4096-bit RSA key and |signature_size| set to 512.
88  *
89  * AVB_ALGORITHM_TYPE_SHA256_RSA8192: Like above, but only with
90  * a 8192-bit RSA key and |signature_size| set to 1024.
91  *
92  * AVB_ALGORITHM_TYPE_SHA512_RSA2048: The hash function used is
93  * SHA-512, resulting in 64 bytes of hash digest data. This hash is
94  * signed with a 2048-bit RSA key. The field |hash_size| must be 64,
95  * |signature_size| must be 256, and the public key data must have
96  * |key_num_bits| set to 2048.
97  *
98  * AVB_ALGORITHM_TYPE_SHA512_RSA4096: Like above, but only with
99  * a 4096-bit RSA key and |signature_size| set to 512.
100  *
101  * AVB_ALGORITHM_TYPE_SHA512_RSA8192: Like above, but only with
102  * a 8192-bit RSA key and |signature_size| set to 1024.
103  */
104 typedef enum {
105   AVB_ALGORITHM_TYPE_NONE,
106   AVB_ALGORITHM_TYPE_SHA256_RSA2048,
107   AVB_ALGORITHM_TYPE_SHA256_RSA4096,
108   AVB_ALGORITHM_TYPE_SHA256_RSA8192,
109   AVB_ALGORITHM_TYPE_SHA512_RSA2048,
110   AVB_ALGORITHM_TYPE_SHA512_RSA4096,
111   AVB_ALGORITHM_TYPE_SHA512_RSA8192,
112   _AVB_ALGORITHM_NUM_TYPES
113 } AvbAlgorithmType;
114 
115 /* Holds algorithm-specific data. The |padding| is needed by avb_rsa_verify. */
116 typedef struct {
117   const uint8_t* padding;
118   size_t padding_len;
119   size_t hash_len;
120 } AvbAlgorithmData;
121 
122 /* Provides algorithm-specific data for a given |algorithm|. Returns NULL if
123  * |algorithm| is invalid.
124  */
125 const AvbAlgorithmData* avb_get_algorithm_data(AvbAlgorithmType algorithm)
126     AVB_ATTR_WARN_UNUSED_RESULT;
127 
128 /* The header for a serialized RSA public key.
129  *
130  * The size of the key is given by |key_num_bits|, for example 2048
131  * for a RSA-2048 key. By definition, a RSA public key is the pair (n,
132  * e) where |n| is the modulus (which can be represented in
133  * |key_num_bits| bits) and |e| is the public exponent. The exponent
134  * is not stored since it's assumed to always be 65537.
135  *
136  * To optimize verification, the key block includes two precomputed
137  * values, |n0inv| (fits in 32 bits) and |rr| and can always be
138  * represented in |key_num_bits|.
139 
140  * The value |n0inv| is the value -1/n[0] (mod 2^32). The value |rr|
141  * is (2^key_num_bits)^2 (mod n).
142  *
143  * Following this header is |key_num_bits| bits of |n|, then
144  * |key_num_bits| bits of |rr|. Both values are stored with most
145  * significant bit first. Each serialized number takes up
146  * |key_num_bits|/8 bytes.
147  *
148  * All fields in this struct are stored in network byte order when
149  * serialized.  To generate a copy with fields swapped to native byte
150  * order, use the function avb_rsa_public_key_header_validate_and_byteswap().
151  *
152  * The avb_rsa_verify() function expects a key in this serialized
153  * format.
154  *
155  * The 'avbtool extract_public_key' command can be used to generate a
156  * serialized RSA public key.
157  */
158 typedef struct AvbRSAPublicKeyHeader {
159   uint32_t key_num_bits;
160   uint32_t n0inv;
161 } AVB_ATTR_PACKED AvbRSAPublicKeyHeader;
162 
163 /* Copies |src| to |dest| and validates, byte-swapping fields in the
164  * process if needed. Returns true if valid, false if invalid.
165  */
166 bool avb_rsa_public_key_header_validate_and_byteswap(
167     const AvbRSAPublicKeyHeader* src,
168     AvbRSAPublicKeyHeader* dest) AVB_ATTR_WARN_UNUSED_RESULT;
169 
170 #ifdef __cplusplus
171 }
172 #endif
173 
174 #endif /* AVB_CRYPTO_H_ */
175