/src/openssl/crypto/rand/rand_pool.c

Source (jump to first uncovered line)
/*
 * Copyright 1995-2021 The OpenSSL Project Authors. All Rights Reserved.
 *
 * Licensed under the Apache License 2.0 (the "License").  You may not use
 * this file except in compliance with the License.  You can obtain a copy
 * in the file LICENSE in the source distribution or at
 * https://www.openssl.org/source/license.html
 */

#include <stdio.h>
#include <time.h>
#include "internal/cryptlib.h"
#include <openssl/opensslconf.h>
#include "crypto/rand.h"
#include <openssl/engine.h>
#include "internal/thread_once.h"
#include "crypto/rand_pool.h"

/*
 * Allocate memory and initialize a new random pool
 */
RAND_POOL *ossl_rand_pool_new(int entropy_requested, int secure,
                              size_t min_len, size_t max_len)
{
    RAND_POOL *pool = OPENSSL_zalloc(sizeof(*pool));
    size_t min_alloc_size = RAND_POOL_MIN_ALLOCATION(secure);

    if (pool == NULL)
        return NULL;

    pool->min_len = min_len;
    pool->max_len = (max_len > RAND_POOL_MAX_LENGTH) ?
        RAND_POOL_MAX_LENGTH : max_len;
    pool->alloc_len = min_len < min_alloc_size ? min_alloc_size : min_len;
    if (pool->alloc_len > pool->max_len)
        pool->alloc_len = pool->max_len;

    if (secure)
        pool->buffer = OPENSSL_secure_zalloc(pool->alloc_len);
    else
        pool->buffer = OPENSSL_zalloc(pool->alloc_len);

    if (pool->buffer == NULL)
        goto err;

    pool->entropy_requested = entropy_requested;
    pool->secure = secure;
    return pool;

err:
    OPENSSL_free(pool);
    return NULL;
}

/*
 * Attach new random pool to the given buffer
 *
 * This function is intended to be used only for feeding random data
 * provided by RAND_add() and RAND_seed() into the <master> DRBG.
 */
RAND_POOL *ossl_rand_pool_attach(const unsigned char *buffer, size_t len,
                                 size_t entropy)
{
    RAND_POOL *pool = OPENSSL_zalloc(sizeof(*pool));

    if (pool == NULL)
        return NULL;

    /*
     * The const needs to be cast away, but attached buffers will not be
     * modified (in contrary to allocated buffers which are zeroed and
     * freed in the end).
     */
    pool->buffer = (unsigned char *) buffer;
    pool->len = len;

    pool->attached = 1;

    pool->min_len = pool->max_len = pool->alloc_len = pool->len;
    pool->entropy = entropy;

    return pool;
}

/*
 * Free |pool|, securely erasing its buffer.
 */
void ossl_rand_pool_free(RAND_POOL *pool)
{
    if (pool == NULL)
        return;

    /*
     * Although it would be advisable from a cryptographical viewpoint,
     * we are not allowed to clear attached buffers, since they are passed
     * to ossl_rand_pool_attach() as `const unsigned char*`.
     * (see corresponding comment in ossl_rand_pool_attach()).
     */
    if (!pool->attached) {
        if (pool->secure)
            OPENSSL_secure_clear_free(pool->buffer, pool->alloc_len);
        else
            OPENSSL_clear_free(pool->buffer, pool->alloc_len);
    }

    OPENSSL_free(pool);
}

/*
 * Return the |pool|'s buffer to the caller (readonly).
 */
const unsigned char *ossl_rand_pool_buffer(RAND_POOL *pool)
{
    return pool->buffer;
}

/*
 * Return the |pool|'s entropy to the caller.
 */
size_t ossl_rand_pool_entropy(RAND_POOL *pool)
{
    return pool->entropy;
}

/*
 * Return the |pool|'s buffer length to the caller.
 */
size_t ossl_rand_pool_length(RAND_POOL *pool)
{
    return pool->len;
}

/*
 * Detach the |pool| buffer and return it to the caller.
 * It's the responsibility of the caller to free the buffer
 * using OPENSSL_secure_clear_free() or to re-attach it
 * again to the pool using ossl_rand_pool_reattach().
 */
unsigned char *ossl_rand_pool_detach(RAND_POOL *pool)
{
    unsigned char *ret = pool->buffer;
    pool->buffer = NULL;
    pool->entropy = 0;
    return ret;
}

/*
 * Re-attach the |pool| buffer. It is only allowed to pass
 * the |buffer| which was previously detached from the same pool.
 */
void ossl_rand_pool_reattach(RAND_POOL *pool, unsigned char *buffer)
{
    pool->buffer = buffer;
    OPENSSL_cleanse(pool->buffer, pool->len);
    pool->len = 0;
}

/*
 * If |entropy_factor| bits contain 1 bit of entropy, how many bytes does one
 * need to obtain at least |bits| bits of entropy?
 */
#define ENTROPY_TO_BYTES(bits, entropy_factor) \
    (((bits) * (entropy_factor) + 7) / 8)


/*
 * Checks whether the |pool|'s entropy is available to the caller.
 * This is the case when entropy count and buffer length are high enough.
 * Returns
 *
 *  |entropy|  if the entropy count and buffer size is large enough
 *      0      otherwise
 */
size_t ossl_rand_pool_entropy_available(RAND_POOL *pool)
{
    if (pool->entropy < pool->entropy_requested)
        return 0;

    if (pool->len < pool->min_len)
        return 0;

    return pool->entropy;
}

/*
 * Returns the (remaining) amount of entropy needed to fill
 * the random pool.
 */

size_t ossl_rand_pool_entropy_needed(RAND_POOL *pool)
{
    if (pool->entropy < pool->entropy_requested)
        return pool->entropy_requested - pool->entropy;

    return 0;
}

/* Increase the allocation size -- not usable for an attached pool */
static int rand_pool_grow(RAND_POOL *pool, size_t len)
{
    if (len > pool->alloc_len - pool->len) {
        unsigned char *p;
        const size_t limit = pool->max_len / 2;
        size_t newlen = pool->alloc_len;

        if (pool->attached || len > pool->max_len - pool->len) {
            ERR_raise(ERR_LIB_RAND, ERR_R_INTERNAL_ERROR);
            return 0;
        }

        do
            newlen = newlen < limit ? newlen * 2 : pool->max_len;
        while (len > newlen - pool->len);

        if (pool->secure)
            p = OPENSSL_secure_zalloc(newlen);
        else
            p = OPENSSL_zalloc(newlen);
        if (p == NULL)
            return 0;
        memcpy(p, pool->buffer, pool->len);
        if (pool->secure)
            OPENSSL_secure_clear_free(pool->buffer, pool->alloc_len);
        else
            OPENSSL_clear_free(pool->buffer, pool->alloc_len);
        pool->buffer = p;
        pool->alloc_len = newlen;
    }
    return 1;
}

/*
 * Returns the number of bytes needed to fill the pool, assuming
 * the input has 1 / |entropy_factor| entropy bits per data bit.
 * In case of an error, 0 is returned.
 */

size_t ossl_rand_pool_bytes_needed(RAND_POOL *pool, unsigned int entropy_factor)
{
    size_t bytes_needed;
    size_t entropy_needed = ossl_rand_pool_entropy_needed(pool);

    if (entropy_factor < 1) {
        ERR_raise(ERR_LIB_RAND, RAND_R_ARGUMENT_OUT_OF_RANGE);
        return 0;
    }

    bytes_needed = ENTROPY_TO_BYTES(entropy_needed, entropy_factor);

    if (bytes_needed > pool->max_len - pool->len) {
        /* not enough space left */
        ERR_raise(ERR_LIB_RAND, RAND_R_RANDOM_POOL_OVERFLOW);
        return 0;
    }

    if (pool->len < pool->min_len &&
        bytes_needed < pool->min_len - pool->len)
        /* to meet the min_len requirement */
        bytes_needed = pool->min_len - pool->len;

    /*
     * Make sure the buffer is large enough for the requested amount
     * of data. This guarantees that existing code patterns where
     * ossl_rand_pool_add_begin, ossl_rand_pool_add_end or ossl_rand_pool_add
     * are used to collect entropy data without any error handling
     * whatsoever, continue to be valid.
     * Furthermore if the allocation here fails once, make sure that
     * we don't fall back to a less secure or even blocking random source,
     * as that could happen by the existing code patterns.
     * This is not a concern for additional data, therefore that
     * is not needed if rand_pool_grow fails in other places.
     */
    if (!rand_pool_grow(pool, bytes_needed)) {
        /* persistent error for this pool */
        pool->max_len = pool->len = 0;
        return 0;
    }

    return bytes_needed;
}

/* Returns the remaining number of bytes available */
size_t ossl_rand_pool_bytes_remaining(RAND_POOL *pool)
{
    return pool->max_len - pool->len;
}

/*
 * Add random bytes to the random pool.
 *
 * It is expected that the |buffer| contains |len| bytes of
 * random input which contains at least |entropy| bits of
 * randomness.
 *
 * Returns 1 if the added amount is adequate, otherwise 0
 */
int ossl_rand_pool_add(RAND_POOL *pool,
                  const unsigned char *buffer, size_t len, size_t entropy)
{
    if (len > pool->max_len - pool->len) {
        ERR_raise(ERR_LIB_RAND, RAND_R_ENTROPY_INPUT_TOO_LONG);
        return 0;
    }

    if (pool->buffer == NULL) {
        ERR_raise(ERR_LIB_RAND, ERR_R_INTERNAL_ERROR);
        return 0;
    }

    if (len > 0) {
        /*
         * This is to protect us from accidentally passing the buffer
         * returned from ossl_rand_pool_add_begin.
         * The check for alloc_len makes sure we do not compare the
         * address of the end of the allocated memory to something
         * different, since that comparison would have an
         * indeterminate result.
         */
        if (pool->alloc_len > pool->len && pool->buffer + pool->len == buffer) {
            ERR_raise(ERR_LIB_RAND, ERR_R_INTERNAL_ERROR);
            return 0;
        }
        /*
         * We have that only for cases when a pool is used to collect
         * additional data.
         * For entropy data, as long as the allocation request stays within
         * the limits given by ossl_rand_pool_bytes_needed this rand_pool_grow
         * below is guaranteed to succeed, thus no allocation happens.
         */
        if (!rand_pool_grow(pool, len))
            return 0;
        memcpy(pool->buffer + pool->len, buffer, len);
        pool->len += len;
        pool->entropy += entropy;
    }

    return 1;
}

/*
 * Start to add random bytes to the random pool in-place.
 *
 * Reserves the next |len| bytes for adding random bytes in-place
 * and returns a pointer to the buffer.
 * The caller is allowed to copy up to |len| bytes into the buffer.
 * If |len| == 0 this is considered a no-op and a NULL pointer
 * is returned without producing an error message.
 *
 * After updating the buffer, ossl_rand_pool_add_end() needs to be called
 * to finish the update operation (see next comment).
 */
unsigned char *ossl_rand_pool_add_begin(RAND_POOL *pool, size_t len)
{
    if (len == 0)
        return NULL;

    if (len > pool->max_len - pool->len) {
        ERR_raise(ERR_LIB_RAND, RAND_R_RANDOM_POOL_OVERFLOW);
        return NULL;
    }

    if (pool->buffer == NULL) {
        ERR_raise(ERR_LIB_RAND, ERR_R_INTERNAL_ERROR);
        return NULL;
    }

    /*
     * As long as the allocation request stays within the limits given
     * by ossl_rand_pool_bytes_needed this rand_pool_grow below is guaranteed
     * to succeed, thus no allocation happens.
     * We have that only for cases when a pool is used to collect
     * additional data. Then the buffer might need to grow here,
     * and of course the caller is responsible to check the return
     * value of this function.
     */
    if (!rand_pool_grow(pool, len))
        return NULL;

    return pool->buffer + pool->len;
}

/*
 * Finish to add random bytes to the random pool in-place.
 *
 * Finishes an in-place update of the random pool started by
 * ossl_rand_pool_add_begin() (see previous comment).
 * It is expected that |len| bytes of random input have been added
 * to the buffer which contain at least |entropy| bits of randomness.
 * It is allowed to add less bytes than originally reserved.
 */
int ossl_rand_pool_add_end(RAND_POOL *pool, size_t len, size_t entropy)
{
    if (len > pool->alloc_len - pool->len) {
        ERR_raise(ERR_LIB_RAND, RAND_R_RANDOM_POOL_OVERFLOW);
        return 0;
    }

    if (len > 0) {
        pool->len += len;
        pool->entropy += entropy;
    }

    return 1;
}

Coverage Report

Created: 2023-06-08 06:40

Line	Count	Source (jump to first uncovered line)
1		/*
2		* Copyright 1995-2021 The OpenSSL Project Authors. All Rights Reserved.
3		*
4		* Licensed under the Apache License 2.0 (the "License"). You may not use
5		* this file except in compliance with the License. You can obtain a copy
6		* in the file LICENSE in the source distribution or at
7		* https://www.openssl.org/source/license.html
8		*/
9
10		#include <stdio.h>
11		#include <time.h>
12		#include "internal/cryptlib.h"
13		#include <openssl/opensslconf.h>
14		#include "crypto/rand.h"
15		#include <openssl/engine.h>
16		#include "internal/thread_once.h"
17		#include "crypto/rand_pool.h"
18
19		/*
20		* Allocate memory and initialize a new random pool
21		*/
22		RAND_POOL *ossl_rand_pool_new(int entropy_requested, int secure,
23		size_t min_len, size_t max_len)
24	0	{
25	0	RAND_POOL pool = OPENSSL_zalloc(sizeof(pool));
26	0	size_t min_alloc_size = RAND_POOL_MIN_ALLOCATION(secure);
27
28	0	if (pool == NULL)
29	0	return NULL;
30
31	0	pool->min_len = min_len;
32	0	pool->max_len = (max_len > RAND_POOL_MAX_LENGTH) ?
33	0	RAND_POOL_MAX_LENGTH : max_len;
34	0	pool->alloc_len = min_len < min_alloc_size ? min_alloc_size : min_len;
35	0	if (pool->alloc_len > pool->max_len)
36	0	pool->alloc_len = pool->max_len;
37
38	0	if (secure)
39	0	pool->buffer = OPENSSL_secure_zalloc(pool->alloc_len);
40	0	else
41	0	pool->buffer = OPENSSL_zalloc(pool->alloc_len);
42
43	0	if (pool->buffer == NULL)
44	0	goto err;
45
46	0	pool->entropy_requested = entropy_requested;
47	0	pool->secure = secure;
48	0	return pool;
49
50	0	err:
51	0	OPENSSL_free(pool);
52	0	return NULL;
53	0	}
54
55		/*
56		* Attach new random pool to the given buffer
57		*
58		* This function is intended to be used only for feeding random data
59		* provided by RAND_add() and RAND_seed() into the <master> DRBG.
60		*/
61		RAND_POOL ossl_rand_pool_attach(const unsigned char buffer, size_t len,
62		size_t entropy)
63	0	{
64	0	RAND_POOL pool = OPENSSL_zalloc(sizeof(pool));
65
66	0	if (pool == NULL)
67	0	return NULL;
68
69		/*
70		* The const needs to be cast away, but attached buffers will not be
71		* modified (in contrary to allocated buffers which are zeroed and
72		* freed in the end).
73		*/
74	0	pool->buffer = (unsigned char *) buffer;
75	0	pool->len = len;
76
77	0	pool->attached = 1;
78
79	0	pool->min_len = pool->max_len = pool->alloc_len = pool->len;
80	0	pool->entropy = entropy;
81
82	0	return pool;
83	0	}
84
85		/*
86		* Free \|pool\|, securely erasing its buffer.
87		*/
88		void ossl_rand_pool_free(RAND_POOL *pool)
89	0	{
90	0	if (pool == NULL)
91	0	return;
92
93		/*
94		* Although it would be advisable from a cryptographical viewpoint,
95		* we are not allowed to clear attached buffers, since they are passed
96		* to ossl_rand_pool_attach() as `const unsigned char*`.
97		* (see corresponding comment in ossl_rand_pool_attach()).
98		*/
99	0	if (!pool->attached) {
100	0	if (pool->secure)
101	0	OPENSSL_secure_clear_free(pool->buffer, pool->alloc_len);
102	0	else
103	0	OPENSSL_clear_free(pool->buffer, pool->alloc_len);
104	0	}
105
106	0	OPENSSL_free(pool);
107	0	}
108
109		/*
110		* Return the \|pool\|'s buffer to the caller (readonly).
111		*/
112		const unsigned char ossl_rand_pool_buffer(RAND_POOL pool)
113	0	{
114	0	return pool->buffer;
115	0	}
116
117		/*
118		* Return the \|pool\|'s entropy to the caller.
119		*/
120		size_t ossl_rand_pool_entropy(RAND_POOL *pool)
121	0	{
122	0	return pool->entropy;
123	0	}
124
125		/*
126		* Return the \|pool\|'s buffer length to the caller.
127		*/
128		size_t ossl_rand_pool_length(RAND_POOL *pool)
129	0	{
130	0	return pool->len;
131	0	}
132
133		/*
134		* Detach the \|pool\| buffer and return it to the caller.
135		* It's the responsibility of the caller to free the buffer
136		* using OPENSSL_secure_clear_free() or to re-attach it
137		* again to the pool using ossl_rand_pool_reattach().
138		*/
139		unsigned char ossl_rand_pool_detach(RAND_POOL pool)
140	0	{
141	0	unsigned char *ret = pool->buffer;
142	0	pool->buffer = NULL;
143	0	pool->entropy = 0;
144	0	return ret;
145	0	}
146
147		/*
148		* Re-attach the \|pool\| buffer. It is only allowed to pass
149		* the \|buffer\| which was previously detached from the same pool.
150		*/
151		void ossl_rand_pool_reattach(RAND_POOL pool, unsigned char buffer)
152	0	{
153	0	pool->buffer = buffer;
154	0	OPENSSL_cleanse(pool->buffer, pool->len);
155	0	pool->len = 0;
156	0	}
157
158		/*
159		* If \|entropy_factor\| bits contain 1 bit of entropy, how many bytes does one
160		* need to obtain at least \|bits\| bits of entropy?
161		*/
162		#define ENTROPY_TO_BYTES(bits, entropy_factor) \
163	0	(((bits) * (entropy_factor) + 7) / 8)
164
165
166		/*
167		* Checks whether the \|pool\|'s entropy is available to the caller.
168		* This is the case when entropy count and buffer length are high enough.
169		* Returns
170		*
171		* \|entropy\| if the entropy count and buffer size is large enough
172		* 0 otherwise
173		*/
174		size_t ossl_rand_pool_entropy_available(RAND_POOL *pool)
175	0	{
176	0	if (pool->entropy < pool->entropy_requested)
177	0	return 0;
178
179	0	if (pool->len < pool->min_len)
180	0	return 0;
181
182	0	return pool->entropy;
183	0	}
184
185		/*
186		* Returns the (remaining) amount of entropy needed to fill
187		* the random pool.
188		*/
189
190		size_t ossl_rand_pool_entropy_needed(RAND_POOL *pool)
191	0	{
192	0	if (pool->entropy < pool->entropy_requested)
193	0	return pool->entropy_requested - pool->entropy;
194
195	0	return 0;
196	0	}
197
198		/* Increase the allocation size -- not usable for an attached pool */
199		static int rand_pool_grow(RAND_POOL *pool, size_t len)
200	0	{
201	0	if (len > pool->alloc_len - pool->len) {
202	0	unsigned char *p;
203	0	const size_t limit = pool->max_len / 2;
204	0	size_t newlen = pool->alloc_len;
205
206	0	if (pool->attached \|\| len > pool->max_len - pool->len) {
207	0	ERR_raise(ERR_LIB_RAND, ERR_R_INTERNAL_ERROR);
208	0	return 0;
209	0	}
210
211	0	do
212	0	newlen = newlen < limit ? newlen * 2 : pool->max_len;
213	0	while (len > newlen - pool->len);
214
215	0	if (pool->secure)
216	0	p = OPENSSL_secure_zalloc(newlen);
217	0	else
218	0	p = OPENSSL_zalloc(newlen);
219	0	if (p == NULL)
220	0	return 0;
221	0	memcpy(p, pool->buffer, pool->len);
222	0	if (pool->secure)
223	0	OPENSSL_secure_clear_free(pool->buffer, pool->alloc_len);
224	0	else
225	0	OPENSSL_clear_free(pool->buffer, pool->alloc_len);
226	0	pool->buffer = p;
227	0	pool->alloc_len = newlen;
228	0	}
229	0	return 1;
230	0	}
231
232		/*
233		* Returns the number of bytes needed to fill the pool, assuming
234		* the input has 1 / \|entropy_factor\| entropy bits per data bit.
235		* In case of an error, 0 is returned.
236		*/
237
238		size_t ossl_rand_pool_bytes_needed(RAND_POOL *pool, unsigned int entropy_factor)
239	0	{
240	0	size_t bytes_needed;
241	0	size_t entropy_needed = ossl_rand_pool_entropy_needed(pool);
242
243	0	if (entropy_factor < 1) {
244	0	ERR_raise(ERR_LIB_RAND, RAND_R_ARGUMENT_OUT_OF_RANGE);
245	0	return 0;
246	0	}
247
248	0	bytes_needed = ENTROPY_TO_BYTES(entropy_needed, entropy_factor);
249
250	0	if (bytes_needed > pool->max_len - pool->len) {
251		/* not enough space left */
252	0	ERR_raise(ERR_LIB_RAND, RAND_R_RANDOM_POOL_OVERFLOW);
253	0	return 0;
254	0	}
255
256	0	if (pool->len < pool->min_len &&
257	0	bytes_needed < pool->min_len - pool->len)
258		/* to meet the min_len requirement */
259	0	bytes_needed = pool->min_len - pool->len;
260
261		/*
262		* Make sure the buffer is large enough for the requested amount
263		* of data. This guarantees that existing code patterns where
264		* ossl_rand_pool_add_begin, ossl_rand_pool_add_end or ossl_rand_pool_add
265		* are used to collect entropy data without any error handling
266		* whatsoever, continue to be valid.
267		* Furthermore if the allocation here fails once, make sure that
268		* we don't fall back to a less secure or even blocking random source,
269		* as that could happen by the existing code patterns.
270		* This is not a concern for additional data, therefore that
271		* is not needed if rand_pool_grow fails in other places.
272		*/
273	0	if (!rand_pool_grow(pool, bytes_needed)) {
274		/* persistent error for this pool */
275	0	pool->max_len = pool->len = 0;
276	0	return 0;
277	0	}
278
279	0	return bytes_needed;
280	0	}
281
282		/* Returns the remaining number of bytes available */
283		size_t ossl_rand_pool_bytes_remaining(RAND_POOL *pool)
284	0	{
285	0	return pool->max_len - pool->len;
286	0	}
287
288		/*
289		* Add random bytes to the random pool.
290		*
291		* It is expected that the \|buffer\| contains \|len\| bytes of
292		* random input which contains at least \|entropy\| bits of
293		* randomness.
294		*
295		* Returns 1 if the added amount is adequate, otherwise 0
296		*/
297		int ossl_rand_pool_add(RAND_POOL *pool,
298		const unsigned char *buffer, size_t len, size_t entropy)
299	0	{
300	0	if (len > pool->max_len - pool->len) {
301	0	ERR_raise(ERR_LIB_RAND, RAND_R_ENTROPY_INPUT_TOO_LONG);
302	0	return 0;
303	0	}
304
305	0	if (pool->buffer == NULL) {
306	0	ERR_raise(ERR_LIB_RAND, ERR_R_INTERNAL_ERROR);
307	0	return 0;
308	0	}
309
310	0	if (len > 0) {
311		/*
312		* This is to protect us from accidentally passing the buffer
313		* returned from ossl_rand_pool_add_begin.
314		* The check for alloc_len makes sure we do not compare the
315		* address of the end of the allocated memory to something
316		* different, since that comparison would have an
317		* indeterminate result.
318		*/
319	0	if (pool->alloc_len > pool->len && pool->buffer + pool->len == buffer) {
320	0	ERR_raise(ERR_LIB_RAND, ERR_R_INTERNAL_ERROR);
321	0	return 0;
322	0	}
323		/*
324		* We have that only for cases when a pool is used to collect
325		* additional data.
326		* For entropy data, as long as the allocation request stays within
327		* the limits given by ossl_rand_pool_bytes_needed this rand_pool_grow
328		* below is guaranteed to succeed, thus no allocation happens.
329		*/
330	0	if (!rand_pool_grow(pool, len))
331	0	return 0;
332	0	memcpy(pool->buffer + pool->len, buffer, len);
333	0	pool->len += len;
334	0	pool->entropy += entropy;
335	0	}
336
337	0	return 1;
338	0	}
339
340		/*
341		* Start to add random bytes to the random pool in-place.
342		*
343		* Reserves the next \|len\| bytes for adding random bytes in-place
344		* and returns a pointer to the buffer.
345		* The caller is allowed to copy up to \|len\| bytes into the buffer.
346		* If \|len\| == 0 this is considered a no-op and a NULL pointer
347		* is returned without producing an error message.
348		*
349		* After updating the buffer, ossl_rand_pool_add_end() needs to be called
350		* to finish the update operation (see next comment).
351		*/
352		unsigned char ossl_rand_pool_add_begin(RAND_POOL pool, size_t len)
353	0	{
354	0	if (len == 0)
355	0	return NULL;
356
357	0	if (len > pool->max_len - pool->len) {
358	0	ERR_raise(ERR_LIB_RAND, RAND_R_RANDOM_POOL_OVERFLOW);
359	0	return NULL;
360	0	}
361
362	0	if (pool->buffer == NULL) {
363	0	ERR_raise(ERR_LIB_RAND, ERR_R_INTERNAL_ERROR);
364	0	return NULL;
365	0	}
366
367		/*
368		* As long as the allocation request stays within the limits given
369		* by ossl_rand_pool_bytes_needed this rand_pool_grow below is guaranteed
370		* to succeed, thus no allocation happens.
371		* We have that only for cases when a pool is used to collect
372		* additional data. Then the buffer might need to grow here,
373		* and of course the caller is responsible to check the return
374		* value of this function.
375		*/
376	0	if (!rand_pool_grow(pool, len))
377	0	return NULL;
378
379	0	return pool->buffer + pool->len;
380	0	}
381
382		/*
383		* Finish to add random bytes to the random pool in-place.
384		*
385		* Finishes an in-place update of the random pool started by
386		* ossl_rand_pool_add_begin() (see previous comment).
387		* It is expected that \|len\| bytes of random input have been added
388		* to the buffer which contain at least \|entropy\| bits of randomness.
389		* It is allowed to add less bytes than originally reserved.
390		*/
391		int ossl_rand_pool_add_end(RAND_POOL *pool, size_t len, size_t entropy)
392	0	{
393	0	if (len > pool->alloc_len - pool->len) {
394	0	ERR_raise(ERR_LIB_RAND, RAND_R_RANDOM_POOL_OVERFLOW);
395	0	return 0;
396	0	}
397
398	0	if (len > 0) {
399	0	pool->len += len;
400	0	pool->entropy += entropy;
401	0	}
402
403	0	return 1;
404	0	}