From: Stephan Mueller Subject: [PATCH v2 03/11] crypto: Documentation - RNG API documentation Date: Sun, 02 Nov 2014 21:36:58 +0100 Message-ID: <5465244.OPD58DmVa6@tachyon.chronox.de> References: <6375771.bx7QqLJLuR@tachyon.chronox.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Cc: "David S. Miller" , Marek Vasut , Jason Cooper , Grant Likely , Geert Uytterhoeven , Linux Kernel Developers List , linux-crypto@vger.kernel.org To: Herbert Xu Return-path: In-Reply-To: <6375771.bx7QqLJLuR@tachyon.chronox.de> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-crypto.vger.kernel.org The API function calls exported by the kernel crypto API for RNGs to be used by consumers are documented. Signed-off-by: Stephan Mueller CC: Marek Vasut --- include/crypto/rng.h | 113 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 113 insertions(+) diff --git a/include/crypto/rng.h b/include/crypto/rng.h index c93f9b9..83c4238 100644 --- a/include/crypto/rng.h +++ b/include/crypto/rng.h @@ -20,11 +20,68 @@ extern struct crypto_rng *crypto_default_rng; int crypto_get_default_rng(void); void crypto_put_default_rng(void); +/** + * Random number generator API to use the ciphers of type + * CRYPTO_ALG_TYPE_RNG (listed as type "rng" in /proc/crypto) + * + * Example code: + * + *static int get_random_numbers(u8 *buf, unsigned int len) + *{ + * struct crypto_rng *rng = NULL; + * char *drbg = "drbg_nopr_sha256"; // Hash DRBG with SHA-256, no PR + * int ret; + * + * if (!buf || !len) { + * pr_debug("No output buffer provided\n"); + * return -EINVAL; + * } + * + * rng = crypto_alloc_rng(drbg, 0, 0); + * if (IS_ERR(rng)) { + * pr_debug("could not allocate RNG handle for %s\n", drbg); + * return -PTR_ERR(rng); + * } + * + * ret = crypto_rng_get_bytes(rng, buf, len); + * if (ret < 0) + * pr_debug("generation of random numbers failed\n"); + * else if (ret == 0) + * pr_debug("RNG returned no data"); + * else + * pr_debug("RNG returned %d bytes of data\n", ret); + * + *out: + * crypto_free_rng(rng); + * return ret; + *} + */ + static inline struct crypto_rng *__crypto_rng_cast(struct crypto_tfm *tfm) { return (struct crypto_rng *)tfm; } +/** + * Allocate a cipher handle for a random number generator. The returned struct + * crypto_rng is the cipher handle that is required for any subsequent + * API invocation for that random number generator. + * + * For all random number generators, this call creates a new private copy of + * the random number generator that does not share a state with other + * instances. The only exception is the "krng" random number generator which + * is a kernel crypto API use case for the get_random_bytes() function of the + * /dev/random driver. + * + * @alg_name is the cra_name / name or cra_driver_name / driver name of the + * message digest cipher + * @type specifies the type of the cipher (see Documentation/crypto/) + * @mask specifies the mask for the cipher (see Documentation/crypto/) + * + * return value: + * allocated cipher handle in case of success + * IS_ERR() is true in case of an error, PTR_ERR() returns the error code. + */ static inline struct crypto_rng *crypto_alloc_rng(const char *alg_name, u32 type, u32 mask) { @@ -40,6 +97,14 @@ static inline struct crypto_tfm *crypto_rng_tfm(struct crypto_rng *tfm) return &tfm->base; } +/** + * Return the generic name (cra_name) of the initialized random number generator + * + * @tfm cipher handle + * + * return value: + * generic name string + */ static inline struct rng_alg *crypto_rng_alg(struct crypto_rng *tfm) { return &crypto_rng_tfm(tfm)->__crt_alg->cra_rng; @@ -50,23 +115,71 @@ static inline struct rng_tfm *crypto_rng_crt(struct crypto_rng *tfm) return &crypto_rng_tfm(tfm)->crt_rng; } +/** + * The referenced random number generator handle is zeroized and subsequently + * freed. + * + * @tfm cipher handle to be freed + */ static inline void crypto_free_rng(struct crypto_rng *tfm) { crypto_free_tfm(crypto_rng_tfm(tfm)); } +/** + * This function fills the caller-allocated buffer with random numbers using the + * random number generator referenced by the cipher handle. + * + * @tfm cipher handle + * @rdata output buffer holding the random numbers + * @dlen length of the output buffer + * + * return value: + * > 0 function was successful and returns the number of generated bytes + * < 0 if an error occurred + */ static inline int crypto_rng_get_bytes(struct crypto_rng *tfm, u8 *rdata, unsigned int dlen) { return crypto_rng_crt(tfm)->rng_gen_random(tfm, rdata, dlen); } +/** + * The reset function completely re-initializes the random number generator + * referenced by the cipher handle by clearing the current state. The new state + * is initialized with the caller provided seed or automatically, depending + * on the random number generator type (the ANSI X9.31 RNG requires + * caller-provided seed, the SP800-90A DRBGs perform an automatic seeding). + * The seed is provided with the. The provided seed should have the length of + * the seed size defined for the random number generator as defined by + * crypto_rng_seedsize. + * + * @tfm cipher handle + * @seed seed input data + * @slen length of the seed input data + * + * return value: + * 0 if the setting of the key was successful + * < 0 if an error occurred + */ static inline int crypto_rng_reset(struct crypto_rng *tfm, u8 *seed, unsigned int slen) { return crypto_rng_crt(tfm)->rng_reset(tfm, seed, slen); } +/** + * The function returns the seed size for the random number generator + * referenced by the cipher handle. This value may be zero if the random + * number generator does not implement or require a reseeding. For example, + * the SP800-90A DRBGs implement an automated reseeding after reaching a + * pre-defined threshold. + * + * @tfm cipher handle + * + * return value: + * seed size for the random number generator + */ static inline int crypto_rng_seedsize(struct crypto_rng *tfm) { return crypto_rng_alg(tfm)->seedsize; -- 2.1.0