1 /**
2  * \file entropy.h
3  *
4  * \brief Entropy accumulator implementation
5  */
6 /*
7  *  Copyright (C) 2006-2016, ARM Limited, All Rights Reserved
8  *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
9  *
10  *  This file is provided under the Apache License 2.0, or the
11  *  GNU General Public License v2.0 or later.
12  *
13  *  **********
14  *  Apache License 2.0:
15  *
16  *  Licensed under the Apache License, Version 2.0 (the "License"); you may
17  *  not use this file except in compliance with the License.
18  *  You may obtain a copy of the License at
19  *
20  *  http://www.apache.org/licenses/LICENSE-2.0
21  *
22  *  Unless required by applicable law or agreed to in writing, software
23  *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
24  *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
25  *  See the License for the specific language governing permissions and
26  *  limitations under the License.
27  *
28  *  **********
29  *
30  *  **********
31  *  GNU General Public License v2.0 or later:
32  *
33  *  This program is free software; you can redistribute it and/or modify
34  *  it under the terms of the GNU General Public License as published by
35  *  the Free Software Foundation; either version 2 of the License, or
36  *  (at your option) any later version.
37  *
38  *  This program is distributed in the hope that it will be useful,
39  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
40  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
41  *  GNU General Public License for more details.
42  *
43  *  You should have received a copy of the GNU General Public License along
44  *  with this program; if not, write to the Free Software Foundation, Inc.,
45  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
46  *
47  *  **********
48  *
49  *  This file is part of mbed TLS (https://tls.mbed.org)
50  */
51 #ifndef MBEDTLS_ENTROPY_H
52 #define MBEDTLS_ENTROPY_H
53 
54 #if !defined(MBEDTLS_CONFIG_FILE)
55 #include "config.h"
56 #else
57 #include MBEDTLS_CONFIG_FILE
58 #endif
59 
60 #include <stddef.h>
61 
62 #if defined(MBEDTLS_SHA512_C) && !defined(MBEDTLS_ENTROPY_FORCE_SHA256)
63 #include "sha512.h"
64 #define MBEDTLS_ENTROPY_SHA512_ACCUMULATOR
65 #else
66 #if defined(MBEDTLS_SHA256_C)
67 #define MBEDTLS_ENTROPY_SHA256_ACCUMULATOR
68 #include "sha256.h"
69 #endif
70 #endif
71 
72 #if defined(MBEDTLS_THREADING_C)
73 #include "threading.h"
74 #endif
75 
76 #if defined(MBEDTLS_HAVEGE_C)
77 #include "havege.h"
78 #endif
79 
80 #define MBEDTLS_ERR_ENTROPY_SOURCE_FAILED                 -0x003C  /**< Critical entropy source failure. */
81 #define MBEDTLS_ERR_ENTROPY_MAX_SOURCES                   -0x003E  /**< No more sources can be added. */
82 #define MBEDTLS_ERR_ENTROPY_NO_SOURCES_DEFINED            -0x0040  /**< No sources have been added to poll. */
83 #define MBEDTLS_ERR_ENTROPY_NO_STRONG_SOURCE              -0x003D  /**< No strong sources have been added to poll. */
84 #define MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR                 -0x003F  /**< Read/write error in file. */
85 
86 /**
87  * \name SECTION: Module settings
88  *
89  * The configuration options you can set for this module are in this section.
90  * Either change them in config.h or define them on the compiler command line.
91  * \{
92  */
93 
94 #if !defined(MBEDTLS_ENTROPY_MAX_SOURCES)
95 #define MBEDTLS_ENTROPY_MAX_SOURCES     20      /**< Maximum number of sources supported */
96 #endif
97 
98 #if !defined(MBEDTLS_ENTROPY_MAX_GATHER)
99 #define MBEDTLS_ENTROPY_MAX_GATHER      128     /**< Maximum amount requested from entropy sources */
100 #endif
101 
102 /* \} name SECTION: Module settings */
103 
104 #if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
105 #define MBEDTLS_ENTROPY_BLOCK_SIZE      64      /**< Block size of entropy accumulator (SHA-512) */
106 #else
107 #define MBEDTLS_ENTROPY_BLOCK_SIZE      32      /**< Block size of entropy accumulator (SHA-256) */
108 #endif
109 
110 #define MBEDTLS_ENTROPY_MAX_SEED_SIZE   1024    /**< Maximum size of seed we read from seed file */
111 #define MBEDTLS_ENTROPY_SOURCE_MANUAL   MBEDTLS_ENTROPY_MAX_SOURCES
112 
113 #define MBEDTLS_ENTROPY_SOURCE_STRONG   1       /**< Entropy source is strong   */
114 #define MBEDTLS_ENTROPY_SOURCE_WEAK     0       /**< Entropy source is weak     */
115 
116 #ifdef __cplusplus
117 extern "C" {
118 #endif
119 
120 /**
121  * \brief           Entropy poll callback pointer
122  *
123  * \param data      Callback-specific data pointer
124  * \param output    Data to fill
125  * \param len       Maximum size to provide
126  * \param olen      The actual amount of bytes put into the buffer (Can be 0)
127  *
128  * \return          0 if no critical failures occurred,
129  *                  MBEDTLS_ERR_ENTROPY_SOURCE_FAILED otherwise
130  */
131 typedef int (*mbedtls_entropy_f_source_ptr)(void *data, unsigned char *output, size_t len,
132                             size_t *olen);
133 
134 /**
135  * \brief           Entropy source state
136  */
137 typedef struct
138 {
139     mbedtls_entropy_f_source_ptr    f_source;   /**< The entropy source callback */
140     void *          p_source;   /**< The callback data pointer */
141     size_t          size;       /**< Amount received in bytes */
142     size_t          threshold;  /**< Minimum bytes required before release */
143     int             strong;     /**< Is the source strong? */
144 }
145 mbedtls_entropy_source_state;
146 
147 /**
148  * \brief           Entropy context structure
149  */
150 typedef struct
151 {
152     int accumulator_started;
153 #if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
154     mbedtls_sha512_context  accumulator;
155 #else
156     mbedtls_sha256_context  accumulator;
157 #endif
158     int             source_count;
159     mbedtls_entropy_source_state    source[MBEDTLS_ENTROPY_MAX_SOURCES];
160 #if defined(MBEDTLS_HAVEGE_C)
161     mbedtls_havege_state    havege_data;
162 #endif
163 #if defined(MBEDTLS_THREADING_C)
164     mbedtls_threading_mutex_t mutex;    /*!< mutex                  */
165 #endif
166 #if defined(MBEDTLS_ENTROPY_NV_SEED)
167     int initial_entropy_run;
168 #endif
169 }
170 mbedtls_entropy_context;
171 
172 /**
173  * \brief           Initialize the context
174  *
175  * \param ctx       Entropy context to initialize
176  */
177 void mbedtls_entropy_init( mbedtls_entropy_context *ctx );
178 
179 /**
180  * \brief           Free the data in the context
181  *
182  * \param ctx       Entropy context to free
183  */
184 void mbedtls_entropy_free( mbedtls_entropy_context *ctx );
185 
186 /**
187  * \brief           Adds an entropy source to poll
188  *                  (Thread-safe if MBEDTLS_THREADING_C is enabled)
189  *
190  * \param ctx       Entropy context
191  * \param f_source  Entropy function
192  * \param p_source  Function data
193  * \param threshold Minimum required from source before entropy is released
194  *                  ( with mbedtls_entropy_func() ) (in bytes)
195  * \param strong    MBEDTLS_ENTROPY_SOURCE_STRONG or
196  *                  MBEDTSL_ENTROPY_SOURCE_WEAK.
197  *                  At least one strong source needs to be added.
198  *                  Weaker sources (such as the cycle counter) can be used as
199  *                  a complement.
200  *
201  * \return          0 if successful or MBEDTLS_ERR_ENTROPY_MAX_SOURCES
202  */
203 int mbedtls_entropy_add_source( mbedtls_entropy_context *ctx,
204                         mbedtls_entropy_f_source_ptr f_source, void *p_source,
205                         size_t threshold, int strong );
206 
207 /**
208  * \brief           Trigger an extra gather poll for the accumulator
209  *                  (Thread-safe if MBEDTLS_THREADING_C is enabled)
210  *
211  * \param ctx       Entropy context
212  *
213  * \return          0 if successful, or MBEDTLS_ERR_ENTROPY_SOURCE_FAILED
214  */
215 int mbedtls_entropy_gather( mbedtls_entropy_context *ctx );
216 
217 /**
218  * \brief           Retrieve entropy from the accumulator
219  *                  (Maximum length: MBEDTLS_ENTROPY_BLOCK_SIZE)
220  *                  (Thread-safe if MBEDTLS_THREADING_C is enabled)
221  *
222  * \param data      Entropy context
223  * \param output    Buffer to fill
224  * \param len       Number of bytes desired, must be at most MBEDTLS_ENTROPY_BLOCK_SIZE
225  *
226  * \return          0 if successful, or MBEDTLS_ERR_ENTROPY_SOURCE_FAILED
227  */
228 int mbedtls_entropy_func( void *data, unsigned char *output, size_t len );
229 
230 /**
231  * \brief           Add data to the accumulator manually
232  *                  (Thread-safe if MBEDTLS_THREADING_C is enabled)
233  *
234  * \param ctx       Entropy context
235  * \param data      Data to add
236  * \param len       Length of data
237  *
238  * \return          0 if successful
239  */
240 int mbedtls_entropy_update_manual( mbedtls_entropy_context *ctx,
241                            const unsigned char *data, size_t len );
242 
243 #if defined(MBEDTLS_ENTROPY_NV_SEED)
244 /**
245  * \brief           Trigger an update of the seed file in NV by using the
246  *                  current entropy pool.
247  *
248  * \param ctx       Entropy context
249  *
250  * \return          0 if successful
251  */
252 int mbedtls_entropy_update_nv_seed( mbedtls_entropy_context *ctx );
253 #endif /* MBEDTLS_ENTROPY_NV_SEED */
254 
255 #if defined(MBEDTLS_FS_IO)
256 /**
257  * \brief               Write a seed file
258  *
259  * \param ctx           Entropy context
260  * \param path          Name of the file
261  *
262  * \return              0 if successful,
263  *                      MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR on file error, or
264  *                      MBEDTLS_ERR_ENTROPY_SOURCE_FAILED
265  */
266 int mbedtls_entropy_write_seed_file( mbedtls_entropy_context *ctx, const char *path );
267 
268 /**
269  * \brief               Read and update a seed file. Seed is added to this
270  *                      instance. No more than MBEDTLS_ENTROPY_MAX_SEED_SIZE bytes are
271  *                      read from the seed file. The rest is ignored.
272  *
273  * \param ctx           Entropy context
274  * \param path          Name of the file
275  *
276  * \return              0 if successful,
277  *                      MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR on file error,
278  *                      MBEDTLS_ERR_ENTROPY_SOURCE_FAILED
279  */
280 int mbedtls_entropy_update_seed_file( mbedtls_entropy_context *ctx, const char *path );
281 #endif /* MBEDTLS_FS_IO */
282 
283 #if defined(MBEDTLS_SELF_TEST)
284 /**
285  * \brief          Checkup routine
286  *
287  *                 This module self-test also calls the entropy self-test,
288  *                 mbedtls_entropy_source_self_test();
289  *
290  * \return         0 if successful, or 1 if a test failed
291  */
292 int mbedtls_entropy_self_test( int verbose );
293 
294 #if defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
295 /**
296  * \brief          Checkup routine
297  *
298  *                 Verifies the integrity of the hardware entropy source
299  *                 provided by the function 'mbedtls_hardware_poll()'.
300  *
301  *                 Note this is the only hardware entropy source that is known
302  *                 at link time, and other entropy sources configured
303  *                 dynamically at runtime by the function
304  *                 mbedtls_entropy_add_source() will not be tested.
305  *
306  * \return         0 if successful, or 1 if a test failed
307  */
308 int mbedtls_entropy_source_self_test( int verbose );
309 #endif /* MBEDTLS_ENTROPY_HARDWARE_ALT */
310 #endif /* MBEDTLS_SELF_TEST */
311 
312 #ifdef __cplusplus
313 }
314 #endif
315 
316 #endif /* entropy.h */
317