1 /** \file psa_crypto_random_impl.h
2 *
3 * \brief PSA crypto random generator implementation abstraction.
4 *
5 * The definitions here need to be consistent with the declarations
6 * in include/mbedtls/psa_util.h. This file contains some redundant
7 * declarations to increase the chance that a compiler will detect
8 * inconsistencies if one file is changed without updating the other,
9 * but not all potential inconsistencies can be enforced, so make sure
10 * to check the public declarations and contracts in
11 * include/mbedtls/psa_util.h if you modify this file.
12 */
13 /*
14 * Copyright The Mbed TLS Contributors
15 * SPDX-License-Identifier: Apache-2.0
16 *
17 * Licensed under the Apache License, Version 2.0 (the "License"); you may
18 * not use this file except in compliance with the License.
19 * You may obtain a copy of the License at
20 *
21 * http://www.apache.org/licenses/LICENSE-2.0
22 *
23 * Unless required by applicable law or agreed to in writing, software
24 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
25 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
26 * See the License for the specific language governing permissions and
27 * limitations under the License.
28 */
29
30 #ifndef PSA_CRYPTO_RANDOM_IMPL_H
31 #define PSA_CRYPTO_RANDOM_IMPL_H
32
33 #include <mbedtls/psa_util.h>
34
35 #if defined(MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG)
36
37 #include <string.h>
38 #include <mbedtls/entropy.h> // only for error codes
39 #include <psa/crypto.h>
40
41 typedef mbedtls_psa_external_random_context_t mbedtls_psa_random_context_t;
42
43 /* Trivial wrapper around psa_generate_random(). */
44 int mbedtls_psa_get_random(void *p_rng,
45 unsigned char *output,
46 size_t output_size);
47
48 /* The PSA RNG API doesn't need any externally maintained state. */
49 #define MBEDTLS_PSA_RANDOM_STATE NULL
50
51 #else /* MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG */
52
53 /* Choose a DRBG based on configuration and availability */
54 #if defined(MBEDTLS_PSA_HMAC_DRBG_MD_TYPE)
55
56 #include "mbedtls/hmac_drbg.h"
57
58 #elif defined(MBEDTLS_CTR_DRBG_C)
59
60 #include "mbedtls/ctr_drbg.h"
61
62 #elif defined(MBEDTLS_HMAC_DRBG_C)
63
64 #include "mbedtls/hmac_drbg.h"
65 #if defined(MBEDTLS_SHA512_C) && defined(MBEDTLS_SHA256_C)
66 #include <limits.h>
67 #if SIZE_MAX > 0xffffffff
68 /* Looks like a 64-bit system, so prefer SHA-512. */
69 #define MBEDTLS_PSA_HMAC_DRBG_MD_TYPE MBEDTLS_MD_SHA512
70 #else
71 /* Looks like a 32-bit system, so prefer SHA-256. */
72 #define MBEDTLS_PSA_HMAC_DRBG_MD_TYPE MBEDTLS_MD_SHA256
73 #endif
74 #elif defined(MBEDTLS_SHA512_C)
75 #define MBEDTLS_PSA_HMAC_DRBG_MD_TYPE MBEDTLS_MD_SHA512
76 #elif defined(MBEDTLS_SHA256_C)
77 #define MBEDTLS_PSA_HMAC_DRBG_MD_TYPE MBEDTLS_MD_SHA256
78 #else
79 #error "No hash algorithm available for HMAC_DBRG."
80 #endif
81
82 #else
83 #error "No DRBG module available for the psa_crypto module."
84 #endif
85
86 #include "mbedtls/entropy.h"
87
88 /** Initialize the PSA DRBG.
89 *
90 * \param p_rng Pointer to the Mbed TLS DRBG state.
91 */
mbedtls_psa_drbg_init(mbedtls_psa_drbg_context_t * p_rng)92 static inline void mbedtls_psa_drbg_init(mbedtls_psa_drbg_context_t *p_rng)
93 {
94 #if defined(MBEDTLS_CTR_DRBG_C)
95 mbedtls_ctr_drbg_init(p_rng);
96 #elif defined(MBEDTLS_HMAC_DRBG_C)
97 mbedtls_hmac_drbg_init(p_rng);
98 #endif
99 }
100
101 /** Deinitialize the PSA DRBG.
102 *
103 * \param p_rng Pointer to the Mbed TLS DRBG state.
104 */
mbedtls_psa_drbg_free(mbedtls_psa_drbg_context_t * p_rng)105 static inline void mbedtls_psa_drbg_free(mbedtls_psa_drbg_context_t *p_rng)
106 {
107 #if defined(MBEDTLS_CTR_DRBG_C)
108 mbedtls_ctr_drbg_free(p_rng);
109 #elif defined(MBEDTLS_HMAC_DRBG_C)
110 mbedtls_hmac_drbg_free(p_rng);
111 #endif
112 }
113
114 /** The type of the PSA random generator context.
115 *
116 * The random generator context is composed of an entropy context and
117 * a DRBG context.
118 */
119 typedef struct {
120 void (* entropy_init)(mbedtls_entropy_context *ctx);
121 void (* entropy_free)(mbedtls_entropy_context *ctx);
122 mbedtls_entropy_context entropy;
123 mbedtls_psa_drbg_context_t drbg;
124 } mbedtls_psa_random_context_t;
125
126 /* Defined in include/mbedtls/psa_util.h so that it's visible to
127 * application code. The declaration here is redundant, but included
128 * as a safety net to make it more likely that a future change that
129 * accidentally causes the implementation to diverge from the interface
130 * will be noticed. */
131 /* Do not include the declaration under MSVC because it doesn't accept it
132 * ("error C2370: 'mbedtls_psa_get_random' : redefinition; different storage class").
133 * Observed with Visual Studio 2013. A known bug apparently:
134 * https://stackoverflow.com/questions/8146541/duplicate-external-static-declarations-not-allowed-in-visual-studio
135 */
136 #if !defined(_MSC_VER)
137 static mbedtls_f_rng_t *const mbedtls_psa_get_random;
138 #endif
139
140 /** The maximum number of bytes that mbedtls_psa_get_random() is expected to
141 * return.
142 */
143 #if defined(MBEDTLS_CTR_DRBG_C)
144 #define MBEDTLS_PSA_RANDOM_MAX_REQUEST MBEDTLS_CTR_DRBG_MAX_REQUEST
145 #elif defined(MBEDTLS_HMAC_DRBG_C)
146 #define MBEDTLS_PSA_RANDOM_MAX_REQUEST MBEDTLS_HMAC_DRBG_MAX_REQUEST
147 #endif
148
149 /** A pointer to the PSA DRBG state.
150 *
151 * This variable is only intended to be used through the macro
152 * #MBEDTLS_PSA_RANDOM_STATE.
153 */
154 /* psa_crypto.c sets this variable to a pointer to the DRBG state in the
155 * global PSA crypto state. */
156 /* The type `mbedtls_psa_drbg_context_t` is defined in
157 * include/mbedtls/psa_util.h so that `mbedtls_psa_random_state` can be
158 * declared there and be visible to application code. */
159 extern mbedtls_psa_drbg_context_t *const mbedtls_psa_random_state;
160
161 /** A pointer to the PSA DRBG state.
162 *
163 * This macro expands to an expression that is suitable as the \c p_rng
164 * parameter to pass to mbedtls_psa_get_random().
165 *
166 * This macro exists in all configurations where the psa_crypto module is
167 * enabled. Its expansion depends on the configuration.
168 */
169 #define MBEDTLS_PSA_RANDOM_STATE mbedtls_psa_random_state
170
171 /** Seed the PSA DRBG.
172 *
173 * \param entropy An entropy context to read the seed from.
174 * \param custom The personalization string.
175 * This can be \c NULL, in which case the personalization
176 * string is empty regardless of the value of \p len.
177 * \param len The length of the personalization string.
178 *
179 * \return \c 0 on success.
180 * \return An Mbed TLS error code (\c MBEDTLS_ERR_xxx) on failure.
181 */
mbedtls_psa_drbg_seed(mbedtls_entropy_context * entropy,const unsigned char * custom,size_t len)182 static inline int mbedtls_psa_drbg_seed(
183 mbedtls_entropy_context *entropy,
184 const unsigned char *custom, size_t len)
185 {
186 #if defined(MBEDTLS_CTR_DRBG_C)
187 return mbedtls_ctr_drbg_seed(MBEDTLS_PSA_RANDOM_STATE,
188 mbedtls_entropy_func,
189 entropy,
190 custom, len);
191 #elif defined(MBEDTLS_HMAC_DRBG_C)
192 const mbedtls_md_info_t *md_info =
193 mbedtls_md_info_from_type(MBEDTLS_PSA_HMAC_DRBG_MD_TYPE);
194 return mbedtls_hmac_drbg_seed(MBEDTLS_PSA_RANDOM_STATE,
195 md_info,
196 mbedtls_entropy_func,
197 entropy,
198 custom, len);
199 #endif
200 }
201
202 #endif /* MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG */
203
204 #endif /* PSA_CRYPTO_RANDOM_IMPL_H */
205
