1 /*
2  * RNG: Random Number Generator  algorithms under the crypto API
3  *
4  * Copyright (c) 2008 Neil Horman <nhorman@tuxdriver.com>
5  * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au>
6  *
7  * This program is free software; you can redistribute it and/or modify it
8  * under the terms of the GNU General Public License as published by the Free
9  * Software Foundation; either version 2 of the License, or (at your option)
10  * any later version.
11  *
12  */
13 
14 #ifndef _CRYPTO_RNG_H
15 #define _CRYPTO_RNG_H
16 
17 #include <linux/crypto.h>
18 
19 struct crypto_rng;
20 
21 /**
22  * struct rng_alg - random number generator definition
23  *
24  * @generate:	The function defined by this variable obtains a
25  *		random number. The random number generator transform
26  *		must generate the random number out of the context
27  *		provided with this call, plus any additional data
28  *		if provided to the call.
29  * @seed:	Seed or reseed the random number generator.  With the
30  *		invocation of this function call, the random number
31  *		generator shall become ready for generation.  If the
32  *		random number generator requires a seed for setting
33  *		up a new state, the seed must be provided by the
34  *		consumer while invoking this function. The required
35  *		size of the seed is defined with @seedsize .
36  * @set_ent:	Set entropy that would otherwise be obtained from
37  *		entropy source.  Internal use only.
38  * @seedsize:	The seed size required for a random number generator
39  *		initialization defined with this variable. Some
40  *		random number generators does not require a seed
41  *		as the seeding is implemented internally without
42  *		the need of support by the consumer. In this case,
43  *		the seed size is set to zero.
44  * @base:	Common crypto API algorithm data structure.
45  */
46 struct rng_alg {
47 	int (*generate)(struct crypto_rng *tfm,
48 			const u8 *src, unsigned int slen,
49 			u8 *dst, unsigned int dlen);
50 	int (*seed)(struct crypto_rng *tfm, const u8 *seed, unsigned int slen);
51 	void (*set_ent)(struct crypto_rng *tfm, const u8 *data,
52 			unsigned int len);
53 
54 	unsigned int seedsize;
55 
56 	struct crypto_alg base;
57 };
58 
59 struct crypto_rng {
60 	struct crypto_tfm base;
61 };
62 
63 extern struct crypto_rng *crypto_default_rng;
64 
65 int crypto_get_default_rng(void);
66 void crypto_put_default_rng(void);
67 
68 /**
69  * DOC: Random number generator API
70  *
71  * The random number generator API is used with the ciphers of type
72  * CRYPTO_ALG_TYPE_RNG (listed as type "rng" in /proc/crypto)
73  */
74 
75 /**
76  * crypto_alloc_rng() -- allocate RNG handle
77  * @alg_name: is the cra_name / name or cra_driver_name / driver name of the
78  *	      message digest cipher
79  * @type: specifies the type of the cipher
80  * @mask: specifies the mask for the cipher
81  *
82  * Allocate a cipher handle for a random number generator. The returned struct
83  * crypto_rng is the cipher handle that is required for any subsequent
84  * API invocation for that random number generator.
85  *
86  * For all random number generators, this call creates a new private copy of
87  * the random number generator that does not share a state with other
88  * instances. The only exception is the "krng" random number generator which
89  * is a kernel crypto API use case for the get_random_bytes() function of the
90  * /dev/random driver.
91  *
92  * Return: allocated cipher handle in case of success; IS_ERR() is true in case
93  *	   of an error, PTR_ERR() returns the error code.
94  */
95 struct crypto_rng *crypto_alloc_rng(const char *alg_name, u32 type, u32 mask);
96 
crypto_rng_tfm(struct crypto_rng * tfm)97 static inline struct crypto_tfm *crypto_rng_tfm(struct crypto_rng *tfm)
98 {
99 	return &tfm->base;
100 }
101 
102 /**
103  * crypto_rng_alg - obtain name of RNG
104  * @tfm: cipher handle
105  *
106  * Return the generic name (cra_name) of the initialized random number generator
107  *
108  * Return: generic name string
109  */
crypto_rng_alg(struct crypto_rng * tfm)110 static inline struct rng_alg *crypto_rng_alg(struct crypto_rng *tfm)
111 {
112 	return container_of(crypto_rng_tfm(tfm)->__crt_alg,
113 			    struct rng_alg, base);
114 }
115 
116 /**
117  * crypto_free_rng() - zeroize and free RNG handle
118  * @tfm: cipher handle to be freed
119  *
120  * If @tfm is a NULL or error pointer, this function does nothing.
121  */
crypto_free_rng(struct crypto_rng * tfm)122 static inline void crypto_free_rng(struct crypto_rng *tfm)
123 {
124 	crypto_destroy_tfm(tfm, crypto_rng_tfm(tfm));
125 }
126 
127 /**
128  * crypto_rng_generate() - get random number
129  * @tfm: cipher handle
130  * @src: Input buffer holding additional data, may be NULL
131  * @slen: Length of additional data
132  * @dst: output buffer holding the random numbers
133  * @dlen: length of the output buffer
134  *
135  * This function fills the caller-allocated buffer with random
136  * numbers using the random number generator referenced by the
137  * cipher handle.
138  *
139  * Return: 0 function was successful; < 0 if an error occurred
140  */
crypto_rng_generate(struct crypto_rng * tfm,const u8 * src,unsigned int slen,u8 * dst,unsigned int dlen)141 static inline int crypto_rng_generate(struct crypto_rng *tfm,
142 				      const u8 *src, unsigned int slen,
143 				      u8 *dst, unsigned int dlen)
144 {
145 	return crypto_rng_alg(tfm)->generate(tfm, src, slen, dst, dlen);
146 }
147 
148 /**
149  * crypto_rng_get_bytes() - get random number
150  * @tfm: cipher handle
151  * @rdata: output buffer holding the random numbers
152  * @dlen: length of the output buffer
153  *
154  * This function fills the caller-allocated buffer with random numbers using the
155  * random number generator referenced by the cipher handle.
156  *
157  * Return: 0 function was successful; < 0 if an error occurred
158  */
crypto_rng_get_bytes(struct crypto_rng * tfm,u8 * rdata,unsigned int dlen)159 static inline int crypto_rng_get_bytes(struct crypto_rng *tfm,
160 				       u8 *rdata, unsigned int dlen)
161 {
162 	return crypto_rng_generate(tfm, NULL, 0, rdata, dlen);
163 }
164 
165 /**
166  * crypto_rng_reset() - re-initialize the RNG
167  * @tfm: cipher handle
168  * @seed: seed input data
169  * @slen: length of the seed input data
170  *
171  * The reset function completely re-initializes the random number generator
172  * referenced by the cipher handle by clearing the current state. The new state
173  * is initialized with the caller provided seed or automatically, depending
174  * on the random number generator type (the ANSI X9.31 RNG requires
175  * caller-provided seed, the SP800-90A DRBGs perform an automatic seeding).
176  * The seed is provided as a parameter to this function call. The provided seed
177  * should have the length of the seed size defined for the random number
178  * generator as defined by crypto_rng_seedsize.
179  *
180  * Return: 0 if the setting of the key was successful; < 0 if an error occurred
181  */
182 int crypto_rng_reset(struct crypto_rng *tfm, const u8 *seed,
183 		     unsigned int slen);
184 
185 /**
186  * crypto_rng_seedsize() - obtain seed size of RNG
187  * @tfm: cipher handle
188  *
189  * The function returns the seed size for the random number generator
190  * referenced by the cipher handle. This value may be zero if the random
191  * number generator does not implement or require a reseeding. For example,
192  * the SP800-90A DRBGs implement an automated reseeding after reaching a
193  * pre-defined threshold.
194  *
195  * Return: seed size for the random number generator
196  */
crypto_rng_seedsize(struct crypto_rng * tfm)197 static inline int crypto_rng_seedsize(struct crypto_rng *tfm)
198 {
199 	return crypto_rng_alg(tfm)->seedsize;
200 }
201 
202 #endif
203