crypto: drbg - Call CTR DRBG DF function only once

[karo-tx-linux.git] / crypto / drbg.c

/*
 * DRBG: Deterministic Random Bits Generator
 *       Based on NIST Recommended DRBG from NIST SP800-90A with the following
 *       properties:
 *              * CTR DRBG with DF with AES-128, AES-192, AES-256 cores
 *              * Hash DRBG with DF with SHA-1, SHA-256, SHA-384, SHA-512 cores
 *              * HMAC DRBG with DF with SHA-1, SHA-256, SHA-384, SHA-512 cores
 *              * with and without prediction resistance
 *
 * Copyright Stephan Mueller <smueller@chronox.de>, 2014
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, and the entire permission notice in its entirety,
 *    including the disclaimer of warranties.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote
 *    products derived from this software without specific prior
 *    written permission.
 *
 * ALTERNATIVELY, this product may be distributed under the terms of
 * the GNU General Public License, in which case the provisions of the GPL are
 * required INSTEAD OF the above restrictions.  (This clause is
 * necessary due to a potential bad interaction between the GPL and
 * the restrictions contained in a BSD-style copyright.)
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
 * WHICH ARE HEREBY DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
 * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 *
 * DRBG Usage
 * ==========
 * The SP 800-90A DRBG allows the user to specify a personalization string
 * for initialization as well as an additional information string for each
 * random number request. The following code fragments show how a caller
 * uses the kernel crypto API to use the full functionality of the DRBG.
 *
 * Usage without any additional data
 * ---------------------------------
 * struct crypto_rng *drng;
 * int err;
 * char data[DATALEN];
 *
 * drng = crypto_alloc_rng(drng_name, 0, 0);
 * err = crypto_rng_get_bytes(drng, &data, DATALEN);
 * crypto_free_rng(drng);
 *
 *
 * Usage with personalization string during initialization
 * -------------------------------------------------------
 * struct crypto_rng *drng;
 * int err;
 * char data[DATALEN];
 * struct drbg_string pers;
 * char personalization[11] = "some-string";
 *
 * drbg_string_fill(&pers, personalization, strlen(personalization));
 * drng = crypto_alloc_rng(drng_name, 0, 0);
 * // The reset completely re-initializes the DRBG with the provided
 * // personalization string
 * err = crypto_rng_reset(drng, &personalization, strlen(personalization));
 * err = crypto_rng_get_bytes(drng, &data, DATALEN);
 * crypto_free_rng(drng);
 *
 *
 * Usage with additional information string during random number request
 * ---------------------------------------------------------------------
 * struct crypto_rng *drng;
 * int err;
 * char data[DATALEN];
 * char addtl_string[11] = "some-string";
 * string drbg_string addtl;
 *
 * drbg_string_fill(&addtl, addtl_string, strlen(addtl_string));
 * drng = crypto_alloc_rng(drng_name, 0, 0);
 * // The following call is a wrapper to crypto_rng_get_bytes() and returns
 * // the same error codes.
 * err = crypto_drbg_get_bytes_addtl(drng, &data, DATALEN, &addtl);
 * crypto_free_rng(drng);
 *
 *
 * Usage with personalization and additional information strings
 * -------------------------------------------------------------
 * Just mix both scenarios above.
 */

#include <crypto/drbg.h>

/***************************************************************
 * Backend cipher definitions available to DRBG
 ***************************************************************/

/*
 * The order of the DRBG definitions here matter: every DRBG is registered
 * as stdrng. Each DRBG receives an increasing cra_priority values the later
 * they are defined in this array (see drbg_fill_array).
 *
 * HMAC DRBGs are favored over Hash DRBGs over CTR DRBGs, and
 * the SHA256 / AES 256 over other ciphers. Thus, the favored
 * DRBGs are the latest entries in this array.
 */
static const struct drbg_core drbg_cores[] = {
#ifdef CONFIG_CRYPTO_DRBG_CTR
        {
                .flags = DRBG_CTR | DRBG_STRENGTH128,
                .statelen = 32, /* 256 bits as defined in 10.2.1 */
                .max_addtllen = 35,
                .max_bits = 19,
                .max_req = 48,
                .blocklen_bytes = 16,
                .cra_name = "ctr_aes128",
                .backend_cra_name = "ecb(aes)",
        }, {
                .flags = DRBG_CTR | DRBG_STRENGTH192,
                .statelen = 40, /* 320 bits as defined in 10.2.1 */
                .max_addtllen = 35,
                .max_bits = 19,
                .max_req = 48,
                .blocklen_bytes = 16,
                .cra_name = "ctr_aes192",
                .backend_cra_name = "ecb(aes)",
        }, {
                .flags = DRBG_CTR | DRBG_STRENGTH256,
                .statelen = 48, /* 384 bits as defined in 10.2.1 */
                .max_addtllen = 35,
                .max_bits = 19,
                .max_req = 48,
                .blocklen_bytes = 16,
                .cra_name = "ctr_aes256",
                .backend_cra_name = "ecb(aes)",
        },
#endif /* CONFIG_CRYPTO_DRBG_CTR */
#ifdef CONFIG_CRYPTO_DRBG_HASH
        {
                .flags = DRBG_HASH | DRBG_STRENGTH128,
                .statelen = 55, /* 440 bits */
                .max_addtllen = 35,
                .max_bits = 19,
                .max_req = 48,
                .blocklen_bytes = 20,
                .cra_name = "sha1",
                .backend_cra_name = "sha1",
        }, {
                .flags = DRBG_HASH | DRBG_STRENGTH256,
                .statelen = 111, /* 888 bits */
                .max_addtllen = 35,
                .max_bits = 19,
                .max_req = 48,
                .blocklen_bytes = 48,
                .cra_name = "sha384",
                .backend_cra_name = "sha384",
        }, {
                .flags = DRBG_HASH | DRBG_STRENGTH256,
                .statelen = 111, /* 888 bits */
                .max_addtllen = 35,
                .max_bits = 19,
                .max_req = 48,
                .blocklen_bytes = 64,
                .cra_name = "sha512",
                .backend_cra_name = "sha512",
        }, {
                .flags = DRBG_HASH | DRBG_STRENGTH256,
                .statelen = 55, /* 440 bits */
                .max_addtllen = 35,
                .max_bits = 19,
                .max_req = 48,
                .blocklen_bytes = 32,
                .cra_name = "sha256",
                .backend_cra_name = "sha256",
        },
#endif /* CONFIG_CRYPTO_DRBG_HASH */
#ifdef CONFIG_CRYPTO_DRBG_HMAC
        {
                .flags = DRBG_HMAC | DRBG_STRENGTH256,
                .statelen = 20, /* block length of cipher */
                .max_addtllen = 35,
                .max_bits = 19,
                .max_req = 48,
                .blocklen_bytes = 20,
                .cra_name = "hmac_sha1",
                .backend_cra_name = "hmac(sha1)",
        }, {
                .flags = DRBG_HMAC | DRBG_STRENGTH256,
                .statelen = 48, /* block length of cipher */
                .max_addtllen = 35,
                .max_bits = 19,
                .max_req = 48,
                .blocklen_bytes = 48,
                .cra_name = "hmac_sha384",
                .backend_cra_name = "hmac(sha384)",
        }, {
                .flags = DRBG_HMAC | DRBG_STRENGTH256,
                .statelen = 64, /* block length of cipher */
                .max_addtllen = 35,
                .max_bits = 19,
                .max_req = 48,
                .blocklen_bytes = 64,
                .cra_name = "hmac_sha512",
                .backend_cra_name = "hmac(sha512)",
        }, {
                .flags = DRBG_HMAC | DRBG_STRENGTH256,
                .statelen = 32, /* block length of cipher */
                .max_addtllen = 35,
                .max_bits = 19,
                .max_req = 48,
                .blocklen_bytes = 32,
                .cra_name = "hmac_sha256",
                .backend_cra_name = "hmac(sha256)",
        },
#endif /* CONFIG_CRYPTO_DRBG_HMAC */
};

/******************************************************************
 * Generic helper functions
 ******************************************************************/

/*
 * Return strength of DRBG according to SP800-90A section 8.4
 *
 * @flags DRBG flags reference
 *
 * Return: normalized strength in *bytes* value or 32 as default
 *         to counter programming errors
 */
static inline unsigned short drbg_sec_strength(drbg_flag_t flags)
{
        switch (flags & DRBG_STRENGTH_MASK) {
        case DRBG_STRENGTH128:
                return 16;
        case DRBG_STRENGTH192:
                return 24;
        case DRBG_STRENGTH256:
                return 32;
        default:
                return 32;
        }
}

/*
 * FIPS 140-2 continuous self test
 * The test is performed on the result of one round of the output
 * function. Thus, the function implicitly knows the size of the
 * buffer.
 *
 * The FIPS test can be called in an endless loop until it returns
 * true. Although the code looks like a potential for a deadlock, it
 * is not the case, because returning a false cannot mathematically
 * occur (except once when a reseed took place and the updated state
 * would is now set up such that the generation of new value returns
 * an identical one -- this is most unlikely and would happen only once).
 * Thus, if this function repeatedly returns false and thus would cause
 * a deadlock, the integrity of the entire kernel is lost.
 *
 * @drbg DRBG handle
 * @buf output buffer of random data to be checked
 *
 * return:
 *      true on success
 *      false on error
 */
static bool drbg_fips_continuous_test(struct drbg_state *drbg,
                                      const unsigned char *buf)
{
#ifdef CONFIG_CRYPTO_FIPS
        int ret = 0;
        /* skip test if we test the overall system */
        if (drbg->test_data)
                return true;
        /* only perform test in FIPS mode */
        if (0 == fips_enabled)
                return true;
        if (!drbg->fips_primed) {
                /* Priming of FIPS test */
                memcpy(drbg->prev, buf, drbg_blocklen(drbg));
                drbg->fips_primed = true;
                /* return false due to priming, i.e. another round is needed */
                return false;
        }
        ret = memcmp(drbg->prev, buf, drbg_blocklen(drbg));
        memcpy(drbg->prev, buf, drbg_blocklen(drbg));
        /* the test shall pass when the two compared values are not equal */
        return ret != 0;
#else
        return true;
#endif /* CONFIG_CRYPTO_FIPS */
}

/*
 * Convert an integer into a byte representation of this integer.
 * The byte representation is big-endian
 *
 * @buf buffer holding the converted integer
 * @val value to be converted
 * @buflen length of buffer
 */
#if (defined(CONFIG_CRYPTO_DRBG_HASH) || defined(CONFIG_CRYPTO_DRBG_CTR))
static inline void drbg_int2byte(unsigned char *buf, uint64_t val,
                                 size_t buflen)
{
        unsigned char *byte;
        uint64_t i;

        byte = buf + (buflen - 1);
        for (i = 0; i < buflen; i++)
                *(byte--) = val >> (i * 8) & 0xff;
}

/*
 * Increment buffer
 *
 * @dst buffer to increment
 * @add value to add
 */
static inline void drbg_add_buf(unsigned char *dst, size_t dstlen,
                                const unsigned char *add, size_t addlen)
{
        /* implied: dstlen > addlen */
        unsigned char *dstptr;
        const unsigned char *addptr;
        unsigned int remainder = 0;
        size_t len = addlen;

        dstptr = dst + (dstlen-1);
        addptr = add + (addlen-1);
        while (len) {
                remainder += *dstptr + *addptr;
                *dstptr = remainder & 0xff;
                remainder >>= 8;
                len--; dstptr--; addptr--;
        }
        len = dstlen - addlen;
        while (len && remainder > 0) {
                remainder = *dstptr + 1;
                *dstptr = remainder & 0xff;
                remainder >>= 8;
                len--; dstptr--;
        }
}
#endif /* defined(CONFIG_CRYPTO_DRBG_HASH) || defined(CONFIG_CRYPTO_DRBG_CTR) */

/******************************************************************
 * CTR DRBG callback functions
 ******************************************************************/

#ifdef CONFIG_CRYPTO_DRBG_CTR
#define CRYPTO_DRBG_CTR_STRING "CTR "
static int drbg_kcapi_sym(struct drbg_state *drbg, const unsigned char *key,
                          unsigned char *outval, const struct drbg_string *in);
static int drbg_init_sym_kernel(struct drbg_state *drbg);
static int drbg_fini_sym_kernel(struct drbg_state *drbg);

/* BCC function for CTR DRBG as defined in 10.4.3 */
static int drbg_ctr_bcc(struct drbg_state *drbg,
                        unsigned char *out, const unsigned char *key,
                        struct list_head *in)
{
        int ret = 0;
        struct drbg_string *curr = NULL;
        struct drbg_string data;
        short cnt = 0;

        drbg_string_fill(&data, out, drbg_blocklen(drbg));

        /* 10.4.3 step 1 */
        memset(out, 0, drbg_blocklen(drbg));

        /* 10.4.3 step 2 / 4 */
        list_for_each_entry(curr, in, list) {
                const unsigned char *pos = curr->buf;
                size_t len = curr->len;
                /* 10.4.3 step 4.1 */
                while (len) {
                        /* 10.4.3 step 4.2 */
                        if (drbg_blocklen(drbg) == cnt) {
                                cnt = 0;
                                ret = drbg_kcapi_sym(drbg, key, out, &data);
                                if (ret)
                                        return ret;
                        }
                        out[cnt] ^= *pos;
                        pos++;
                        cnt++;
                        len--;
                }
        }
        /* 10.4.3 step 4.2 for last block */
        if (cnt)
                ret = drbg_kcapi_sym(drbg, key, out, &data);

        return ret;
}

/*
 * scratchpad usage: drbg_ctr_update is interlinked with drbg_ctr_df
 * (and drbg_ctr_bcc, but this function does not need any temporary buffers),
 * the scratchpad is used as follows:
 * drbg_ctr_update:
 *      temp
 *              start: drbg->scratchpad
 *              length: drbg_statelen(drbg) + drbg_blocklen(drbg)
 *                      note: the cipher writing into this variable works
 *                      blocklen-wise. Now, when the statelen is not a multiple
 *                      of blocklen, the generateion loop below "spills over"
 *                      by at most blocklen. Thus, we need to give sufficient
 *                      memory.
 *      df_data
 *              start: drbg->scratchpad +
 *                              drbg_statelen(drbg) + drbg_blocklen(drbg)
 *              length: drbg_statelen(drbg)
 *
 * drbg_ctr_df:
 *      pad
 *              start: df_data + drbg_statelen(drbg)
 *              length: drbg_blocklen(drbg)
 *      iv
 *              start: pad + drbg_blocklen(drbg)
 *              length: drbg_blocklen(drbg)
 *      temp
 *              start: iv + drbg_blocklen(drbg)
 *              length: drbg_satelen(drbg) + drbg_blocklen(drbg)
 *                      note: temp is the buffer that the BCC function operates
 *                      on. BCC operates blockwise. drbg_statelen(drbg)
 *                      is sufficient when the DRBG state length is a multiple
 *                      of the block size. For AES192 (and maybe other ciphers)
 *                      this is not correct and the length for temp is
 *                      insufficient (yes, that also means for such ciphers,
 *                      the final output of all BCC rounds are truncated).
 *                      Therefore, add drbg_blocklen(drbg) to cover all
 *                      possibilities.
 */

/* Derivation Function for CTR DRBG as defined in 10.4.2 */
static int drbg_ctr_df(struct drbg_state *drbg,
                       unsigned char *df_data, size_t bytes_to_return,
                       struct list_head *seedlist)
{
        int ret = -EFAULT;
        unsigned char L_N[8];
        /* S3 is input */
        struct drbg_string S1, S2, S4, cipherin;
        LIST_HEAD(bcc_list);
        unsigned char *pad = df_data + drbg_statelen(drbg);
        unsigned char *iv = pad + drbg_blocklen(drbg);
        unsigned char *temp = iv + drbg_blocklen(drbg);
        size_t padlen = 0;
        unsigned int templen = 0;
        /* 10.4.2 step 7 */
        unsigned int i = 0;
        /* 10.4.2 step 8 */
        const unsigned char *K = (unsigned char *)
                           "\x00\x01\x02\x03\x04\x05\x06\x07"
                           "\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f"
                           "\x10\x11\x12\x13\x14\x15\x16\x17"
                           "\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f";
        unsigned char *X;
        size_t generated_len = 0;
        size_t inputlen = 0;
        struct drbg_string *seed = NULL;

        memset(pad, 0, drbg_blocklen(drbg));
        memset(iv, 0, drbg_blocklen(drbg));
        memset(temp, 0, drbg_statelen(drbg));

        /* 10.4.2 step 1 is implicit as we work byte-wise */

        /* 10.4.2 step 2 */
        if ((512/8) < bytes_to_return)
                return -EINVAL;

        /* 10.4.2 step 2 -- calculate the entire length of all input data */
        list_for_each_entry(seed, seedlist, list)
                inputlen += seed->len;
        drbg_int2byte(&L_N[0], inputlen, 4);

        /* 10.4.2 step 3 */
        drbg_int2byte(&L_N[4], bytes_to_return, 4);

        /* 10.4.2 step 5: length is L_N, input_string, one byte, padding */
        padlen = (inputlen + sizeof(L_N) + 1) % (drbg_blocklen(drbg));
        /* wrap the padlen appropriately */
        if (padlen)
                padlen = drbg_blocklen(drbg) - padlen;
        /*
         * pad / padlen contains the 0x80 byte and the following zero bytes.
         * As the calculated padlen value only covers the number of zero
         * bytes, this value has to be incremented by one for the 0x80 byte.
         */
        padlen++;
        pad[0] = 0x80;

        /* 10.4.2 step 4 -- first fill the linked list and then order it */
        drbg_string_fill(&S1, iv, drbg_blocklen(drbg));
        list_add_tail(&S1.list, &bcc_list);
        drbg_string_fill(&S2, L_N, sizeof(L_N));
        list_add_tail(&S2.list, &bcc_list);
        list_splice_tail(seedlist, &bcc_list);
        drbg_string_fill(&S4, pad, padlen);
        list_add_tail(&S4.list, &bcc_list);

        /* 10.4.2 step 9 */
        while (templen < (drbg_keylen(drbg) + (drbg_blocklen(drbg)))) {
                /*
                 * 10.4.2 step 9.1 - the padding is implicit as the buffer
                 * holds zeros after allocation -- even the increment of i
                 * is irrelevant as the increment remains within length of i
                 */
                drbg_int2byte(iv, i, 4);
                /* 10.4.2 step 9.2 -- BCC and concatenation with temp */
                ret = drbg_ctr_bcc(drbg, temp + templen, K, &bcc_list);
                if (ret)
                        goto out;
                /* 10.4.2 step 9.3 */
                i++;
                templen += drbg_blocklen(drbg);
        }

        /* 10.4.2 step 11 */
        X = temp + (drbg_keylen(drbg));
        drbg_string_fill(&cipherin, X, drbg_blocklen(drbg));

        /* 10.4.2 step 12: overwriting of outval is implemented in next step */

        /* 10.4.2 step 13 */
        while (generated_len < bytes_to_return) {
                short blocklen = 0;
                /*
                 * 10.4.2 step 13.1: the truncation of the key length is
                 * implicit as the key is only drbg_blocklen in size based on
                 * the implementation of the cipher function callback
                 */
                ret = drbg_kcapi_sym(drbg, temp, X, &cipherin);
                if (ret)
                        goto out;
                blocklen = (drbg_blocklen(drbg) <
                                (bytes_to_return - generated_len)) ?
                            drbg_blocklen(drbg) :
                                (bytes_to_return - generated_len);
                /* 10.4.2 step 13.2 and 14 */
                memcpy(df_data + generated_len, X, blocklen);
                generated_len += blocklen;
        }

        ret = 0;

out:
        memset(iv, 0, drbg_blocklen(drbg));
        memset(temp, 0, drbg_statelen(drbg));
        memset(pad, 0, drbg_blocklen(drbg));
        return ret;
}

/*
 * update function of CTR DRBG as defined in 10.2.1.2
 *
 * The reseed variable has an enhanced meaning compared to the update
 * functions of the other DRBGs as follows:
 * 0 => initial seed from initialization
 * 1 => reseed via drbg_seed
 * 2 => first invocation from drbg_ctr_update when addtl is present. In
 *      this case, the df_data scratchpad is not deleted so that it is
 *      available for another calls to prevent calling the DF function
 *      again.
 * 3 => second invocation from drbg_ctr_update. When the update function
 *      was called with addtl, the df_data memory already contains the
 *      DFed addtl information and we do not need to call DF again.
 */
static int drbg_ctr_update(struct drbg_state *drbg, struct list_head *seed,
                           int reseed)
{
        int ret = -EFAULT;
        /* 10.2.1.2 step 1 */
        unsigned char *temp = drbg->scratchpad;
        unsigned char *df_data = drbg->scratchpad + drbg_statelen(drbg) +
                                 drbg_blocklen(drbg);
        unsigned char *temp_p, *df_data_p; /* pointer to iterate over buffers */
        unsigned int len = 0;
        struct drbg_string cipherin;
        unsigned char prefix = DRBG_PREFIX1;

        memset(temp, 0, drbg_statelen(drbg) + drbg_blocklen(drbg));
        if (3 > reseed)
                memset(df_data, 0, drbg_statelen(drbg));

        /* 10.2.1.3.2 step 2 and 10.2.1.4.2 step 2 */
        if (seed) {
                ret = drbg_ctr_df(drbg, df_data, drbg_statelen(drbg), seed);
                if (ret)
                        goto out;
        }

        drbg_string_fill(&cipherin, drbg->V, drbg_blocklen(drbg));
        /*
         * 10.2.1.3.2 steps 2 and 3 are already covered as the allocation
         * zeroizes all memory during initialization
         */
        while (len < (drbg_statelen(drbg))) {
                /* 10.2.1.2 step 2.1 */
                drbg_add_buf(drbg->V, drbg_blocklen(drbg), &prefix, 1);
                /*
                 * 10.2.1.2 step 2.2 */
                ret = drbg_kcapi_sym(drbg, drbg->C, temp + len, &cipherin);
                if (ret)
                        goto out;
                /* 10.2.1.2 step 2.3 and 3 */
                len += drbg_blocklen(drbg);
        }

        /* 10.2.1.2 step 4 */
        temp_p = temp;
        df_data_p = df_data;
        for (len = 0; len < drbg_statelen(drbg); len++) {
                *temp_p ^= *df_data_p;
                df_data_p++; temp_p++;
        }

        /* 10.2.1.2 step 5 */
        memcpy(drbg->C, temp, drbg_keylen(drbg));
        /* 10.2.1.2 step 6 */
        memcpy(drbg->V, temp + drbg_keylen(drbg), drbg_blocklen(drbg));
        ret = 0;

out:
        memset(temp, 0, drbg_statelen(drbg) + drbg_blocklen(drbg));
        if (2 != reseed)
                memset(df_data, 0, drbg_statelen(drbg));
        return ret;
}

/*
 * scratchpad use: drbg_ctr_update is called independently from
 * drbg_ctr_extract_bytes. Therefore, the scratchpad is reused
 */
/* Generate function of CTR DRBG as defined in 10.2.1.5.2 */
static int drbg_ctr_generate(struct drbg_state *drbg,
                             unsigned char *buf, unsigned int buflen,
                             struct drbg_string *addtl)
{
        int len = 0;
        int ret = 0;
        struct drbg_string data;
        unsigned char prefix = DRBG_PREFIX1;

        memset(drbg->scratchpad, 0, drbg_blocklen(drbg));

        /* 10.2.1.5.2 step 2 */
        if (addtl && 0 < addtl->len) {
                LIST_HEAD(addtllist);

                list_add_tail(&addtl->list, &addtllist);
                ret = drbg_ctr_update(drbg, &addtllist, 2);
                if (ret)
                        return 0;
        }

        /* 10.2.1.5.2 step 4.1 */
        drbg_add_buf(drbg->V, drbg_blocklen(drbg), &prefix, 1);
        drbg_string_fill(&data, drbg->V, drbg_blocklen(drbg));
        while (len < buflen) {
                int outlen = 0;
                /* 10.2.1.5.2 step 4.2 */
                ret = drbg_kcapi_sym(drbg, drbg->C, drbg->scratchpad, &data);
                if (ret) {
                        len = ret;
                        goto out;
                }
                outlen = (drbg_blocklen(drbg) < (buflen - len)) ?
                          drbg_blocklen(drbg) : (buflen - len);
                if (!drbg_fips_continuous_test(drbg, drbg->scratchpad)) {
                        /* 10.2.1.5.2 step 6 */
                        drbg_add_buf(drbg->V, drbg_blocklen(drbg), &prefix, 1);
                        continue;
                }
                /* 10.2.1.5.2 step 4.3 */
                memcpy(buf + len, drbg->scratchpad, outlen);
                len += outlen;
                /* 10.2.1.5.2 step 6 */
                if (len < buflen)
                        drbg_add_buf(drbg->V, drbg_blocklen(drbg), &prefix, 1);
        }

        /* 10.2.1.5.2 step 6 */
        ret = drbg_ctr_update(drbg, NULL, 3);
        if (ret)
                len = ret;

out:
        memset(drbg->scratchpad, 0, drbg_blocklen(drbg));
        return len;
}

static struct drbg_state_ops drbg_ctr_ops = {
        .update         = drbg_ctr_update,
        .generate       = drbg_ctr_generate,
        .crypto_init    = drbg_init_sym_kernel,
        .crypto_fini    = drbg_fini_sym_kernel,
};
#endif /* CONFIG_CRYPTO_DRBG_CTR */

/******************************************************************
 * HMAC DRBG callback functions
 ******************************************************************/

#if defined(CONFIG_CRYPTO_DRBG_HASH) || defined(CONFIG_CRYPTO_DRBG_HMAC)
static int drbg_kcapi_hash(struct drbg_state *drbg, const unsigned char *key,
                           unsigned char *outval, const struct list_head *in);
static int drbg_init_hash_kernel(struct drbg_state *drbg);
static int drbg_fini_hash_kernel(struct drbg_state *drbg);
#endif /* (CONFIG_CRYPTO_DRBG_HASH || CONFIG_CRYPTO_DRBG_HMAC) */

#ifdef CONFIG_CRYPTO_DRBG_HMAC
#define CRYPTO_DRBG_HMAC_STRING "HMAC "
/* update function of HMAC DRBG as defined in 10.1.2.2 */
static int drbg_hmac_update(struct drbg_state *drbg, struct list_head *seed,
                            int reseed)
{
        int ret = -EFAULT;
        int i = 0;
        struct drbg_string seed1, seed2, vdata;
        LIST_HEAD(seedlist);
        LIST_HEAD(vdatalist);

        if (!reseed) {
                /* 10.1.2.3 step 2 */
                memset(drbg->C, 0, drbg_statelen(drbg));
                memset(drbg->V, 1, drbg_statelen(drbg));
        }

        drbg_string_fill(&seed1, drbg->V, drbg_statelen(drbg));
        list_add_tail(&seed1.list, &seedlist);
        /* buffer of seed2 will be filled in for loop below with one byte */
        drbg_string_fill(&seed2, NULL, 1);
        list_add_tail(&seed2.list, &seedlist);
        /* input data of seed is allowed to be NULL at this point */
        if (seed)
                list_splice_tail(seed, &seedlist);

        drbg_string_fill(&vdata, drbg->V, drbg_statelen(drbg));
        list_add_tail(&vdata.list, &vdatalist);
        for (i = 2; 0 < i; i--) {
                /* first round uses 0x0, second 0x1 */
                unsigned char prefix = DRBG_PREFIX0;
                if (1 == i)
                        prefix = DRBG_PREFIX1;
                /* 10.1.2.2 step 1 and 4 -- concatenation and HMAC for key */
                seed2.buf = &prefix;
                ret = drbg_kcapi_hash(drbg, drbg->C, drbg->C, &seedlist);
                if (ret)
                        return ret;

                /* 10.1.2.2 step 2 and 5 -- HMAC for V */
                ret = drbg_kcapi_hash(drbg, drbg->C, drbg->V, &vdatalist);
                if (ret)
                        return ret;

                /* 10.1.2.2 step 3 */
                if (!seed)
                        return ret;
        }

        return 0;
}

/* generate function of HMAC DRBG as defined in 10.1.2.5 */
static int drbg_hmac_generate(struct drbg_state *drbg,
                              unsigned char *buf,
                              unsigned int buflen,
                              struct drbg_string *addtl)
{
        int len = 0;
        int ret = 0;
        struct drbg_string data;
        LIST_HEAD(datalist);

        /* 10.1.2.5 step 2 */
        if (addtl && 0 < addtl->len) {
                LIST_HEAD(addtllist);

                list_add_tail(&addtl->list, &addtllist);
                ret = drbg_hmac_update(drbg, &addtllist, 1);
                if (ret)
                        return ret;
        }

        drbg_string_fill(&data, drbg->V, drbg_statelen(drbg));
        list_add_tail(&data.list, &datalist);
        while (len < buflen) {
                unsigned int outlen = 0;
                /* 10.1.2.5 step 4.1 */
                ret = drbg_kcapi_hash(drbg, drbg->C, drbg->V, &datalist);
                if (ret)
                        return ret;
                outlen = (drbg_blocklen(drbg) < (buflen - len)) ?
                          drbg_blocklen(drbg) : (buflen - len);
                if (!drbg_fips_continuous_test(drbg, drbg->V))
                        continue;

                /* 10.1.2.5 step 4.2 */
                memcpy(buf + len, drbg->V, outlen);
                len += outlen;
        }

        /* 10.1.2.5 step 6 */
        if (addtl && 0 < addtl->len) {
                LIST_HEAD(addtllist);

                list_add_tail(&addtl->list, &addtllist);
                ret = drbg_hmac_update(drbg, &addtllist, 1);
        } else {
                ret = drbg_hmac_update(drbg, NULL, 1);
        }
        if (ret)
                return ret;

        return len;
}

static struct drbg_state_ops drbg_hmac_ops = {
        .update         = drbg_hmac_update,
        .generate       = drbg_hmac_generate,
        .crypto_init    = drbg_init_hash_kernel,
        .crypto_fini    = drbg_fini_hash_kernel,

};
#endif /* CONFIG_CRYPTO_DRBG_HMAC */

/******************************************************************
 * Hash DRBG callback functions
 ******************************************************************/

#ifdef CONFIG_CRYPTO_DRBG_HASH
#define CRYPTO_DRBG_HASH_STRING "HASH "
/*
 * scratchpad usage: as drbg_hash_update and drbg_hash_df are used
 * interlinked, the scratchpad is used as follows:
 * drbg_hash_update
 *      start: drbg->scratchpad
 *      length: drbg_statelen(drbg)
 * drbg_hash_df:
 *      start: drbg->scratchpad + drbg_statelen(drbg)
 *      length: drbg_blocklen(drbg)
 *
 * drbg_hash_process_addtl uses the scratchpad, but fully completes
 * before either of the functions mentioned before are invoked. Therefore,
 * drbg_hash_process_addtl does not need to be specifically considered.
 */

/* Derivation Function for Hash DRBG as defined in 10.4.1 */
static int drbg_hash_df(struct drbg_state *drbg,
                        unsigned char *outval, size_t outlen,
                        struct list_head *entropylist)
{
        int ret = 0;
        size_t len = 0;
        unsigned char input[5];
        unsigned char *tmp = drbg->scratchpad + drbg_statelen(drbg);
        struct drbg_string data;

        memset(tmp, 0, drbg_blocklen(drbg));

        /* 10.4.1 step 3 */
        input[0] = 1;
        drbg_int2byte(&input[1], (outlen * 8), 4);

        /* 10.4.1 step 4.1 -- concatenation of data for input into hash */
        drbg_string_fill(&data, input, 5);
        list_add(&data.list, entropylist);

        /* 10.4.1 step 4 */
        while (len < outlen) {
                short blocklen = 0;
                /* 10.4.1 step 4.1 */
                ret = drbg_kcapi_hash(drbg, NULL, tmp, entropylist);
                if (ret)
                        goto out;
                /* 10.4.1 step 4.2 */
                input[0]++;
                blocklen = (drbg_blocklen(drbg) < (outlen - len)) ?
                            drbg_blocklen(drbg) : (outlen - len);
                memcpy(outval + len, tmp, blocklen);
                len += blocklen;
        }

out:
        memset(tmp, 0, drbg_blocklen(drbg));
        return ret;
}

/* update function for Hash DRBG as defined in 10.1.1.2 / 10.1.1.3 */
static int drbg_hash_update(struct drbg_state *drbg, struct list_head *seed,
                            int reseed)
{
        int ret = 0;
        struct drbg_string data1, data2;
        LIST_HEAD(datalist);
        LIST_HEAD(datalist2);
        unsigned char *V = drbg->scratchpad;
        unsigned char prefix = DRBG_PREFIX1;

        memset(drbg->scratchpad, 0, drbg_statelen(drbg));
        if (!seed)
                return -EINVAL;

        if (reseed) {
                /* 10.1.1.3 step 1 */
                memcpy(V, drbg->V, drbg_statelen(drbg));
                drbg_string_fill(&data1, &prefix, 1);
                list_add_tail(&data1.list, &datalist);
                drbg_string_fill(&data2, V, drbg_statelen(drbg));
                list_add_tail(&data2.list, &datalist);
        }
        list_splice_tail(seed, &datalist);

        /* 10.1.1.2 / 10.1.1.3 step 2 and 3 */
        ret = drbg_hash_df(drbg, drbg->V, drbg_statelen(drbg), &datalist);
        if (ret)
                goto out;

        /* 10.1.1.2 / 10.1.1.3 step 4  */
        prefix = DRBG_PREFIX0;
        drbg_string_fill(&data1, &prefix, 1);
        list_add_tail(&data1.list, &datalist2);
        drbg_string_fill(&data2, drbg->V, drbg_statelen(drbg));
        list_add_tail(&data2.list, &datalist2);
        /* 10.1.1.2 / 10.1.1.3 step 4 */
        ret = drbg_hash_df(drbg, drbg->C, drbg_statelen(drbg), &datalist2);

out:
        memset(drbg->scratchpad, 0, drbg_statelen(drbg));
        return ret;
}

/* processing of additional information string for Hash DRBG */
static int drbg_hash_process_addtl(struct drbg_state *drbg,
                                   struct drbg_string *addtl)
{
        int ret = 0;
        struct drbg_string data1, data2;
        LIST_HEAD(datalist);
        unsigned char prefix = DRBG_PREFIX2;

        /* this is value w as per documentation */
        memset(drbg->scratchpad, 0, drbg_blocklen(drbg));

        /* 10.1.1.4 step 2 */
        if (!addtl || 0 == addtl->len)
                return 0;

        /* 10.1.1.4 step 2a */
        drbg_string_fill(&data1, &prefix, 1);
        drbg_string_fill(&data2, drbg->V, drbg_statelen(drbg));
        list_add_tail(&data1.list, &datalist);
        list_add_tail(&data2.list, &datalist);
        list_add_tail(&addtl->list, &datalist);
        ret = drbg_kcapi_hash(drbg, NULL, drbg->scratchpad, &datalist);
        if (ret)
                goto out;

        /* 10.1.1.4 step 2b */
        drbg_add_buf(drbg->V, drbg_statelen(drbg),
                     drbg->scratchpad, drbg_blocklen(drbg));

out:
        memset(drbg->scratchpad, 0, drbg_blocklen(drbg));
        return ret;
}

/* Hashgen defined in 10.1.1.4 */
static int drbg_hash_hashgen(struct drbg_state *drbg,
                             unsigned char *buf,
                             unsigned int buflen)
{
        int len = 0;
        int ret = 0;
        unsigned char *src = drbg->scratchpad;
        unsigned char *dst = drbg->scratchpad + drbg_statelen(drbg);
        struct drbg_string data;
        LIST_HEAD(datalist);
        unsigned char prefix = DRBG_PREFIX1;

        memset(src, 0, drbg_statelen(drbg));
        memset(dst, 0, drbg_blocklen(drbg));

        /* 10.1.1.4 step hashgen 2 */
        memcpy(src, drbg->V, drbg_statelen(drbg));

        drbg_string_fill(&data, src, drbg_statelen(drbg));
        list_add_tail(&data.list, &datalist);
        while (len < buflen) {
                unsigned int outlen = 0;
                /* 10.1.1.4 step hashgen 4.1 */
                ret = drbg_kcapi_hash(drbg, NULL, dst, &datalist);
                if (ret) {
                        len = ret;
                        goto out;
                }
                outlen = (drbg_blocklen(drbg) < (buflen - len)) ?
                          drbg_blocklen(drbg) : (buflen - len);
                if (!drbg_fips_continuous_test(drbg, dst)) {
                        drbg_add_buf(src, drbg_statelen(drbg), &prefix, 1);
                        continue;
                }
                /* 10.1.1.4 step hashgen 4.2 */
                memcpy(buf + len, dst, outlen);
                len += outlen;
                /* 10.1.1.4 hashgen step 4.3 */
                if (len < buflen)
                        drbg_add_buf(src, drbg_statelen(drbg), &prefix, 1);
        }

out:
        memset(drbg->scratchpad, 0,
               (drbg_statelen(drbg) + drbg_blocklen(drbg)));
        return len;
}

/* generate function for Hash DRBG as defined in  10.1.1.4 */
static int drbg_hash_generate(struct drbg_state *drbg,
                              unsigned char *buf, unsigned int buflen,
                              struct drbg_string *addtl)
{
        int len = 0;
        int ret = 0;
        unsigned char req[8];
        unsigned char prefix = DRBG_PREFIX3;
        struct drbg_string data1, data2;
        LIST_HEAD(datalist);

        /* 10.1.1.4 step 2 */
        ret = drbg_hash_process_addtl(drbg, addtl);
        if (ret)
                return ret;
        /* 10.1.1.4 step 3 */
        len = drbg_hash_hashgen(drbg, buf, buflen);

        /* this is the value H as documented in 10.1.1.4 */
        memset(drbg->scratchpad, 0, drbg_blocklen(drbg));
        /* 10.1.1.4 step 4 */
        drbg_string_fill(&data1, &prefix, 1);
        list_add_tail(&data1.list, &datalist);
        drbg_string_fill(&data2, drbg->V, drbg_statelen(drbg));
        list_add_tail(&data2.list, &datalist);
        ret = drbg_kcapi_hash(drbg, NULL, drbg->scratchpad, &datalist);
        if (ret) {
                len = ret;
                goto out;
        }

        /* 10.1.1.4 step 5 */
        drbg_add_buf(drbg->V, drbg_statelen(drbg),
                     drbg->scratchpad, drbg_blocklen(drbg));
        drbg_add_buf(drbg->V, drbg_statelen(drbg),
                     drbg->C, drbg_statelen(drbg));
        drbg_int2byte(req, drbg->reseed_ctr, sizeof(req));
        drbg_add_buf(drbg->V, drbg_statelen(drbg), req, 8);

out:
        memset(drbg->scratchpad, 0, drbg_blocklen(drbg));
        return len;
}

/*
 * scratchpad usage: as update and generate are used isolated, both
 * can use the scratchpad
 */
static struct drbg_state_ops drbg_hash_ops = {
        .update         = drbg_hash_update,
        .generate       = drbg_hash_generate,
        .crypto_init    = drbg_init_hash_kernel,
        .crypto_fini    = drbg_fini_hash_kernel,
};
#endif /* CONFIG_CRYPTO_DRBG_HASH */

/******************************************************************
 * Functions common for DRBG implementations
 ******************************************************************/

/*
 * Seeding or reseeding of the DRBG
 *
 * @drbg: DRBG state struct
 * @pers: personalization / additional information buffer
 * @reseed: 0 for initial seed process, 1 for reseeding
 *
 * return:
 *      0 on success
 *      error value otherwise
 */
static int drbg_seed(struct drbg_state *drbg, struct drbg_string *pers,
                     bool reseed)
{
        int ret = 0;
        unsigned char *entropy = NULL;
        size_t entropylen = 0;
        struct drbg_string data1;
        LIST_HEAD(seedlist);

        /* 9.1 / 9.2 / 9.3.1 step 3 */
        if (pers && pers->len > (drbg_max_addtl(drbg))) {
                pr_devel("DRBG: personalization string too long %zu\n",
                         pers->len);
                return -EINVAL;
        }

        if (drbg->test_data && drbg->test_data->testentropy) {
                drbg_string_fill(&data1, drbg->test_data->testentropy->buf,
                                 drbg->test_data->testentropy->len);
                pr_devel("DRBG: using test entropy\n");
        } else {
                /*
                 * Gather entropy equal to the security strength of the DRBG.
                 * With a derivation function, a nonce is required in addition
                 * to the entropy. A nonce must be at least 1/2 of the security
                 * strength of the DRBG in size. Thus, entropy * nonce is 3/2
                 * of the strength. The consideration of a nonce is only
                 * applicable during initial seeding.
                 */
                entropylen = drbg_sec_strength(drbg->core->flags);
                if (!entropylen)
                        return -EFAULT;
                if (!reseed)
                        entropylen = ((entropylen + 1) / 2) * 3;
                pr_devel("DRBG: (re)seeding with %zu bytes of entropy\n",
                         entropylen);
                entropy = kzalloc(entropylen, GFP_KERNEL);
                if (!entropy)
                        return -ENOMEM;
                get_random_bytes(entropy, entropylen);
                drbg_string_fill(&data1, entropy, entropylen);
        }
        list_add_tail(&data1.list, &seedlist);

        /*
         * concatenation of entropy with personalization str / addtl input)
         * the variable pers is directly handed in by the caller, so check its
         * contents whether it is appropriate
         */
        if (pers && pers->buf && 0 < pers->len) {
                list_add_tail(&pers->list, &seedlist);
                pr_devel("DRBG: using personalization string\n");
        }

        ret = drbg->d_ops->update(drbg, &seedlist, reseed);
        if (ret)
                goto out;

        drbg->seeded = true;
        /* 10.1.1.2 / 10.1.1.3 step 5 */
        drbg->reseed_ctr = 1;

out:
        if (entropy)
                kzfree(entropy);
        return ret;
}

/* Free all substructures in a DRBG state without the DRBG state structure */
static inline void drbg_dealloc_state(struct drbg_state *drbg)
{
        if (!drbg)
                return;
        if (drbg->V)
                kzfree(drbg->V);
        drbg->V = NULL;
        if (drbg->C)
                kzfree(drbg->C);
        drbg->C = NULL;
        if (drbg->scratchpad)
                kzfree(drbg->scratchpad);
        drbg->scratchpad = NULL;
        drbg->reseed_ctr = 0;
#ifdef CONFIG_CRYPTO_FIPS
        if (drbg->prev)
                kzfree(drbg->prev);
        drbg->prev = NULL;
        drbg->fips_primed = false;
#endif
}

/*
 * Allocate all sub-structures for a DRBG state.
 * The DRBG state structure must already be allocated.
 */
static inline int drbg_alloc_state(struct drbg_state *drbg)
{
        int ret = -ENOMEM;
        unsigned int sb_size = 0;

        if (!drbg)
                return -EINVAL;

        drbg->V = kzalloc(drbg_statelen(drbg), GFP_KERNEL);
        if (!drbg->V)
                goto err;
        drbg->C = kzalloc(drbg_statelen(drbg), GFP_KERNEL);
        if (!drbg->C)
                goto err;
#ifdef CONFIG_CRYPTO_FIPS
        drbg->prev = kzalloc(drbg_blocklen(drbg), GFP_KERNEL);
        if (!drbg->prev)
                goto err;
        drbg->fips_primed = false;
#endif
        /* scratchpad is only generated for CTR and Hash */
        if (drbg->core->flags & DRBG_HMAC)
                sb_size = 0;
        else if (drbg->core->flags & DRBG_CTR)
                sb_size = drbg_statelen(drbg) + drbg_blocklen(drbg) + /* temp */
                          drbg_statelen(drbg) + /* df_data */
                          drbg_blocklen(drbg) + /* pad */
                          drbg_blocklen(drbg) + /* iv */
                          drbg_statelen(drbg) + drbg_blocklen(drbg); /* temp */
        else
                sb_size = drbg_statelen(drbg) + drbg_blocklen(drbg);

        if (0 < sb_size) {
                drbg->scratchpad = kzalloc(sb_size, GFP_KERNEL);
                if (!drbg->scratchpad)
                        goto err;
        }
        spin_lock_init(&drbg->drbg_lock);
        return 0;

err:
        drbg_dealloc_state(drbg);
        return ret;
}

/*
 * Strategy to avoid holding long term locks: generate a shadow copy of DRBG
 * and perform all operations on this shadow copy. After finishing, restore
 * the updated state of the shadow copy into original drbg state. This way,
 * only the read and write operations of the original drbg state must be
 * locked
 */
static inline void drbg_copy_drbg(struct drbg_state *src,
                                  struct drbg_state *dst)
{
        if (!src || !dst)
                return;
        memcpy(dst->V, src->V, drbg_statelen(src));
        memcpy(dst->C, src->C, drbg_statelen(src));
        dst->reseed_ctr = src->reseed_ctr;
        dst->seeded = src->seeded;
        dst->pr = src->pr;
#ifdef CONFIG_CRYPTO_FIPS
        dst->fips_primed = src->fips_primed;
        memcpy(dst->prev, src->prev, drbg_blocklen(src));
#endif
        /*
         * Not copied:
         * scratchpad is initialized drbg_alloc_state;
         * priv_data is initialized with call to crypto_init;
         * d_ops and core are set outside, as these parameters are const;
         * test_data is set outside to prevent it being copied back.
         */
}

static int drbg_make_shadow(struct drbg_state *drbg, struct drbg_state **shadow)
{
        int ret = -ENOMEM;
        struct drbg_state *tmp = NULL;

        if (!drbg || !drbg->core || !drbg->V || !drbg->C) {
                pr_devel("DRBG: attempt to generate shadow copy for "
                         "uninitialized DRBG state rejected\n");
                return -EINVAL;
        }
        /* HMAC does not have a scratchpad */
        if (!(drbg->core->flags & DRBG_HMAC) && NULL == drbg->scratchpad)
                return -EINVAL;

        tmp = kzalloc(sizeof(struct drbg_state), GFP_KERNEL);
        if (!tmp)
                return -ENOMEM;

        /* read-only data as they are defined as const, no lock needed */
        tmp->core = drbg->core;
        tmp->d_ops = drbg->d_ops;

        ret = drbg_alloc_state(tmp);
        if (ret)
                goto err;

        spin_lock_bh(&drbg->drbg_lock);
        drbg_copy_drbg(drbg, tmp);
        /* only make a link to the test buffer, as we only read that data */
        tmp->test_data = drbg->test_data;
        spin_unlock_bh(&drbg->drbg_lock);
        *shadow = tmp;
        return 0;

err:
        if (tmp)
                kzfree(tmp);
        return ret;
}

static void drbg_restore_shadow(struct drbg_state *drbg,
                                struct drbg_state **shadow)
{
        struct drbg_state *tmp = *shadow;

        spin_lock_bh(&drbg->drbg_lock);
        drbg_copy_drbg(tmp, drbg);
        spin_unlock_bh(&drbg->drbg_lock);
        drbg_dealloc_state(tmp);
        kzfree(tmp);
        *shadow = NULL;
}

/*************************************************************************
 * DRBG interface functions
 *************************************************************************/

/*
 * DRBG generate function as required by SP800-90A - this function
 * generates random numbers
 *
 * @drbg DRBG state handle
 * @buf Buffer where to store the random numbers -- the buffer must already
 *      be pre-allocated by caller
 * @buflen Length of output buffer - this value defines the number of random
 *         bytes pulled from DRBG
 * @addtl Additional input that is mixed into state, may be NULL -- note
 *        the entropy is pulled by the DRBG internally unconditionally
 *        as defined in SP800-90A. The additional input is mixed into
 *        the state in addition to the pulled entropy.
 *
 * return: generated number of bytes
 */
static int drbg_generate(struct drbg_state *drbg,
                         unsigned char *buf, unsigned int buflen,
                         struct drbg_string *addtl)
{
        int len = 0;
        struct drbg_state *shadow = NULL;

        if (0 == buflen || !buf) {
                pr_devel("DRBG: no output buffer provided\n");
                return -EINVAL;
        }
        if (addtl && NULL == addtl->buf && 0 < addtl->len) {
                pr_devel("DRBG: wrong format of additional information\n");
                return -EINVAL;
        }

        len = drbg_make_shadow(drbg, &shadow);
        if (len) {
                pr_devel("DRBG: shadow copy cannot be generated\n");
                return len;
        }

        /* 9.3.1 step 2 */
        len = -EINVAL;
        if (buflen > (drbg_max_request_bytes(shadow))) {
                pr_devel("DRBG: requested random numbers too large %u\n",
                         buflen);
                goto err;
        }

        /* 9.3.1 step 3 is implicit with the chosen DRBG */

        /* 9.3.1 step 4 */
        if (addtl && addtl->len > (drbg_max_addtl(shadow))) {
                pr_devel("DRBG: additional information string too long %zu\n",
                         addtl->len);
                goto err;
        }
        /* 9.3.1 step 5 is implicit with the chosen DRBG */

        /*
         * 9.3.1 step 6 and 9 supplemented by 9.3.2 step c is implemented
         * here. The spec is a bit convoluted here, we make it simpler.
         */
        if ((drbg_max_requests(shadow)) < shadow->reseed_ctr)
                shadow->seeded = false;

        /* allocate cipher handle */
        if (shadow->d_ops->crypto_init) {
                len = shadow->d_ops->crypto_init(shadow);
                if (len)
                        goto err;
        }

        if (shadow->pr || !shadow->seeded) {
                pr_devel("DRBG: reseeding before generation (prediction "
                         "resistance: %s, state %s)\n",
                         drbg->pr ? "true" : "false",
                         drbg->seeded ? "seeded" : "unseeded");
                /* 9.3.1 steps 7.1 through 7.3 */
                len = drbg_seed(shadow, addtl, true);
                if (len)
                        goto err;
                /* 9.3.1 step 7.4 */
                addtl = NULL;
        }
        /* 9.3.1 step 8 and 10 */
        len = shadow->d_ops->generate(shadow, buf, buflen, addtl);

        /* 10.1.1.4 step 6, 10.1.2.5 step 7, 10.2.1.5.2 step 7 */
        shadow->reseed_ctr++;
        if (0 >= len)
                goto err;

        /*
         * Section 11.3.3 requires to re-perform self tests after some
         * generated random numbers. The chosen value after which self
         * test is performed is arbitrary, but it should be reasonable.
         * However, we do not perform the self tests because of the following
         * reasons: it is mathematically impossible that the initial self tests
         * were successfully and the following are not. If the initial would
         * pass and the following would not, the kernel integrity is violated.
         * In this case, the entire kernel operation is questionable and it
         * is unlikely that the integrity violation only affects the
         * correct operation of the DRBG.
         *
         * Albeit the following code is commented out, it is provided in
         * case somebody has a need to implement the test of 11.3.3.
         */
#if 0
        if (shadow->reseed_ctr && !(shadow->reseed_ctr % 4096)) {
                int err = 0;
                pr_devel("DRBG: start to perform self test\n");
                if (drbg->core->flags & DRBG_HMAC)
                        err = alg_test("drbg_pr_hmac_sha256",
                                       "drbg_pr_hmac_sha256", 0, 0);
                else if (drbg->core->flags & DRBG_CTR)
                        err = alg_test("drbg_pr_ctr_aes128",
                                       "drbg_pr_ctr_aes128", 0, 0);
                else
                        err = alg_test("drbg_pr_sha256",
                                       "drbg_pr_sha256", 0, 0);
                if (err) {
                        pr_err("DRBG: periodical self test failed\n");
                        /*
                         * uninstantiate implies that from now on, only errors
                         * are returned when reusing this DRBG cipher handle
                         */
                        drbg_uninstantiate(drbg);
                        drbg_dealloc_state(shadow);
                        kzfree(shadow);
                        return 0;
                } else {
                        pr_devel("DRBG: self test successful\n");
                }
        }
#endif

err:
        if (shadow->d_ops->crypto_fini)
                shadow->d_ops->crypto_fini(shadow);
        drbg_restore_shadow(drbg, &shadow);
        return len;
}

/*
 * Wrapper around drbg_generate which can pull arbitrary long strings
 * from the DRBG without hitting the maximum request limitation.
 *
 * Parameters: see drbg_generate
 * Return codes: see drbg_generate -- if one drbg_generate request fails,
 *               the entire drbg_generate_long request fails
 */
static int drbg_generate_long(struct drbg_state *drbg,
                              unsigned char *buf, unsigned int buflen,
                              struct drbg_string *addtl)
{
        int len = 0;
        unsigned int slice = 0;
        do {
                int tmplen = 0;
                unsigned int chunk = 0;
                slice = ((buflen - len) / drbg_max_request_bytes(drbg));
                chunk = slice ? drbg_max_request_bytes(drbg) : (buflen - len);
                tmplen = drbg_generate(drbg, buf + len, chunk, addtl);
                if (0 >= tmplen)
                        return tmplen;
                len += tmplen;
        } while (slice > 0);
        return len;
}

/*
 * DRBG instantiation function as required by SP800-90A - this function
 * sets up the DRBG handle, performs the initial seeding and all sanity
 * checks required by SP800-90A
 *
 * @drbg memory of state -- if NULL, new memory is allocated
 * @pers Personalization string that is mixed into state, may be NULL -- note
 *       the entropy is pulled by the DRBG internally unconditionally
 *       as defined in SP800-90A. The additional input is mixed into
 *       the state in addition to the pulled entropy.
 * @coreref reference to core
 * @pr prediction resistance enabled
 *
 * return
 *      0 on success
 *      error value otherwise
 */
static int drbg_instantiate(struct drbg_state *drbg, struct drbg_string *pers,
                            int coreref, bool pr)
{
        int ret = -ENOMEM;

        pr_devel("DRBG: Initializing DRBG core %d with prediction resistance "
                 "%s\n", coreref, pr ? "enabled" : "disabled");
        drbg->core = &drbg_cores[coreref];
        drbg->pr = pr;
        drbg->seeded = false;
        switch (drbg->core->flags & DRBG_TYPE_MASK) {
#ifdef CONFIG_CRYPTO_DRBG_HMAC
        case DRBG_HMAC:
                drbg->d_ops = &drbg_hmac_ops;
                break;
#endif /* CONFIG_CRYPTO_DRBG_HMAC */
#ifdef CONFIG_CRYPTO_DRBG_HASH
        case DRBG_HASH:
                drbg->d_ops = &drbg_hash_ops;
                break;
#endif /* CONFIG_CRYPTO_DRBG_HASH */
#ifdef CONFIG_CRYPTO_DRBG_CTR
        case DRBG_CTR:
                drbg->d_ops = &drbg_ctr_ops;
                break;
#endif /* CONFIG_CRYPTO_DRBG_CTR */
        default:
                return -EOPNOTSUPP;
        }

        /* 9.1 step 1 is implicit with the selected DRBG type */

        /*
         * 9.1 step 2 is implicit as caller can select prediction resistance
         * and the flag is copied into drbg->flags --
         * all DRBG types support prediction resistance
         */

        /* 9.1 step 4 is implicit in  drbg_sec_strength */

        ret = drbg_alloc_state(drbg);
        if (ret)
                return ret;

        ret = -EFAULT;
        if (drbg->d_ops->crypto_init && drbg->d_ops->crypto_init(drbg))
                goto err;
        ret = drbg_seed(drbg, pers, false);
        if (drbg->d_ops->crypto_fini)
                drbg->d_ops->crypto_fini(drbg);
        if (ret)
                goto err;

        return 0;

err:
        drbg_dealloc_state(drbg);
        return ret;
}

/*
 * DRBG uninstantiate function as required by SP800-90A - this function
 * frees all buffers and the DRBG handle
 *
 * @drbg DRBG state handle
 *
 * return
 *      0 on success
 */
static int drbg_uninstantiate(struct drbg_state *drbg)
{
        spin_lock_bh(&drbg->drbg_lock);
        drbg_dealloc_state(drbg);
        /* no scrubbing of test_data -- this shall survive an uninstantiate */
        spin_unlock_bh(&drbg->drbg_lock);
        return 0;
}

/*
 * Helper function for setting the test data in the DRBG
 *
 * @drbg DRBG state handle
 * @test_data test data to sets
 */
static inline void drbg_set_testdata(struct drbg_state *drbg,
                                     struct drbg_test_data *test_data)
{
        if (!test_data || !test_data->testentropy)
                return;
        spin_lock_bh(&drbg->drbg_lock);
        drbg->test_data = test_data;
        spin_unlock_bh(&drbg->drbg_lock);
}

/***************************************************************
 * Kernel crypto API cipher invocations requested by DRBG
 ***************************************************************/

#if defined(CONFIG_CRYPTO_DRBG_HASH) || defined(CONFIG_CRYPTO_DRBG_HMAC)
struct sdesc {
        struct shash_desc shash;
        char ctx[];
};

static int drbg_init_hash_kernel(struct drbg_state *drbg)
{
        struct sdesc *sdesc;
        struct crypto_shash *tfm;

        tfm = crypto_alloc_shash(drbg->core->backend_cra_name, 0, 0);
        if (IS_ERR(tfm)) {
                pr_info("DRBG: could not allocate digest TFM handle\n");
                return PTR_ERR(tfm);
        }
        BUG_ON(drbg_blocklen(drbg) != crypto_shash_digestsize(tfm));
        sdesc = kzalloc(sizeof(struct shash_desc) + crypto_shash_descsize(tfm),
                        GFP_KERNEL);
        if (!sdesc) {
                crypto_free_shash(tfm);
                return -ENOMEM;
        }

        sdesc->shash.tfm = tfm;
        sdesc->shash.flags = 0;
        drbg->priv_data = sdesc;
        return 0;
}

static int drbg_fini_hash_kernel(struct drbg_state *drbg)
{
        struct sdesc *sdesc = (struct sdesc *)drbg->priv_data;
        if (sdesc) {
                crypto_free_shash(sdesc->shash.tfm);
                kzfree(sdesc);
        }
        drbg->priv_data = NULL;
        return 0;
}

static int drbg_kcapi_hash(struct drbg_state *drbg, const unsigned char *key,
                           unsigned char *outval, const struct list_head *in)
{
        struct sdesc *sdesc = (struct sdesc *)drbg->priv_data;
        struct drbg_string *input = NULL;

        if (key)
                crypto_shash_setkey(sdesc->shash.tfm, key, drbg_statelen(drbg));
        crypto_shash_init(&sdesc->shash);
        list_for_each_entry(input, in, list)
                crypto_shash_update(&sdesc->shash, input->buf, input->len);
        return crypto_shash_final(&sdesc->shash, outval);
}
#endif /* (CONFIG_CRYPTO_DRBG_HASH || CONFIG_CRYPTO_DRBG_HMAC) */

#ifdef CONFIG_CRYPTO_DRBG_CTR
static int drbg_init_sym_kernel(struct drbg_state *drbg)
{
        int ret = 0;
        struct crypto_blkcipher *tfm;

        tfm = crypto_alloc_blkcipher(drbg->core->backend_cra_name, 0, 0);
        if (IS_ERR(tfm)) {
                pr_info("DRBG: could not allocate cipher TFM handle\n");
                return PTR_ERR(tfm);
        }
        BUG_ON(drbg_blocklen(drbg) != crypto_blkcipher_blocksize(tfm));
        drbg->priv_data = tfm;
        return ret;
}

static int drbg_fini_sym_kernel(struct drbg_state *drbg)
{
        struct crypto_blkcipher *tfm =
                (struct crypto_blkcipher *)drbg->priv_data;
        if (tfm)
                crypto_free_blkcipher(tfm);
        drbg->priv_data = NULL;
        return 0;
}

static int drbg_kcapi_sym(struct drbg_state *drbg, const unsigned char *key,
                          unsigned char *outval, const struct drbg_string *in)
{
        int ret = 0;
        struct scatterlist sg_in, sg_out;
        struct blkcipher_desc desc;
        struct crypto_blkcipher *tfm =
                (struct crypto_blkcipher *)drbg->priv_data;

        desc.tfm = tfm;
        desc.flags = 0;
        crypto_blkcipher_setkey(tfm, key, (drbg_keylen(drbg)));
        /* there is only component in *in */
        sg_init_one(&sg_in, in->buf, in->len);
        sg_init_one(&sg_out, outval, drbg_blocklen(drbg));
        ret = crypto_blkcipher_encrypt(&desc, &sg_out, &sg_in, in->len);

        return ret;
}
#endif /* CONFIG_CRYPTO_DRBG_CTR */

/***************************************************************
 * Kernel crypto API interface to register DRBG
 ***************************************************************/

/*
 * Look up the DRBG flags by given kernel crypto API cra_name
 * The code uses the drbg_cores definition to do this
 *
 * @cra_name kernel crypto API cra_name
 * @coreref reference to integer which is filled with the pointer to
 *  the applicable core
 * @pr reference for setting prediction resistance
 *
 * return: flags
 */
static inline void drbg_convert_tfm_core(const char *cra_driver_name,
                                         int *coreref, bool *pr)
{
        int i = 0;
        size_t start = 0;
        int len = 0;

        *pr = true;
        /* disassemble the names */
        if (!memcmp(cra_driver_name, "drbg_nopr_", 10)) {
                start = 10;
                *pr = false;
        } else if (!memcmp(cra_driver_name, "drbg_pr_", 8)) {
                start = 8;
        } else {
                return;
        }

        /* remove the first part */
        len = strlen(cra_driver_name) - start;
        for (i = 0; ARRAY_SIZE(drbg_cores) > i; i++) {
                if (!memcmp(cra_driver_name + start, drbg_cores[i].cra_name,
                            len)) {
                        *coreref = i;
                        return;
                }
        }
}

static int drbg_kcapi_init(struct crypto_tfm *tfm)
{
        struct drbg_state *drbg = crypto_tfm_ctx(tfm);
        bool pr = false;
        int coreref = 0;

        drbg_convert_tfm_core(crypto_tfm_alg_name(tfm), &coreref, &pr);
        /*
         * when personalization string is needed, the caller must call reset
         * and provide the personalization string as seed information
         */
        return drbg_instantiate(drbg, NULL, coreref, pr);
}

static void drbg_kcapi_cleanup(struct crypto_tfm *tfm)
{
        drbg_uninstantiate(crypto_tfm_ctx(tfm));
}

/*
 * Generate random numbers invoked by the kernel crypto API:
 * The API of the kernel crypto API is extended as follows:
 *
 * If dlen is larger than zero, rdata is interpreted as the output buffer
 * where random data is to be stored.
 *
 * If dlen is zero, rdata is interpreted as a pointer to a struct drbg_gen
 * which holds the additional information string that is used for the
 * DRBG generation process. The output buffer that is to be used to store
 * data is also pointed to by struct drbg_gen.
 */
static int drbg_kcapi_random(struct crypto_rng *tfm, u8 *rdata,
                             unsigned int dlen)
{
        struct drbg_state *drbg = crypto_rng_ctx(tfm);
        if (0 < dlen) {
                return drbg_generate_long(drbg, rdata, dlen, NULL);
        } else {
                struct drbg_gen *data = (struct drbg_gen *)rdata;
                struct drbg_string addtl;
                /* catch NULL pointer */
                if (!data)
                        return 0;
                drbg_set_testdata(drbg, data->test_data);
                /* linked list variable is now local to allow modification */
                drbg_string_fill(&addtl, data->addtl->buf, data->addtl->len);
                return drbg_generate_long(drbg, data->outbuf, data->outlen,
                                          &addtl);
        }
}

/*
 * Reset the DRBG invoked by the kernel crypto API
 * The reset implies a full re-initialization of the DRBG. Similar to the
 * generate function of drbg_kcapi_random, this function extends the
 * kernel crypto API interface with struct drbg_gen
 */
static int drbg_kcapi_reset(struct crypto_rng *tfm, u8 *seed, unsigned int slen)
{
        struct drbg_state *drbg = crypto_rng_ctx(tfm);
        struct crypto_tfm *tfm_base = crypto_rng_tfm(tfm);
        bool pr = false;
        struct drbg_string seed_string;
        int coreref = 0;

        drbg_uninstantiate(drbg);
        drbg_convert_tfm_core(crypto_tfm_alg_driver_name(tfm_base), &coreref,
                              &pr);
        if (0 < slen) {
                drbg_string_fill(&seed_string, seed, slen);
                return drbg_instantiate(drbg, &seed_string, coreref, pr);
        } else {
                struct drbg_gen *data = (struct drbg_gen *)seed;
                /* allow invocation of API call with NULL, 0 */
                if (!data)
                        return drbg_instantiate(drbg, NULL, coreref, pr);
                drbg_set_testdata(drbg, data->test_data);
                /* linked list variable is now local to allow modification */
                drbg_string_fill(&seed_string, data->addtl->buf,
                                 data->addtl->len);
                return drbg_instantiate(drbg, &seed_string, coreref, pr);
        }
}

/***************************************************************
 * Kernel module: code to load the module
 ***************************************************************/

/*
 * Tests as defined in 11.3.2 in addition to the cipher tests: testing
 * of the error handling.
 *
 * Note: testing of failing seed source as defined in 11.3.2 is not applicable
 * as seed source of get_random_bytes does not fail.
 *
 * Note 2: There is no sensible way of testing the reseed counter
 * enforcement, so skip it.
 */
static inline int __init drbg_healthcheck_sanity(void)
{
#ifdef CONFIG_CRYPTO_FIPS
        int len = 0;
#define OUTBUFLEN 16
        unsigned char buf[OUTBUFLEN];
        struct drbg_state *drbg = NULL;
        int ret = -EFAULT;
        int rc = -EFAULT;
        bool pr = false;
        int coreref = 0;
        struct drbg_string addtl;
        size_t max_addtllen, max_request_bytes;

        /* only perform test in FIPS mode */
        if (!fips_enabled)
                return 0;

#ifdef CONFIG_CRYPTO_DRBG_CTR
        drbg_convert_tfm_core("drbg_nopr_ctr_aes128", &coreref, &pr);
#elif defined CONFIG_CRYPTO_DRBG_HASH
        drbg_convert_tfm_core("drbg_nopr_sha256", &coreref, &pr);
#else
        drbg_convert_tfm_core("drbg_nopr_hmac_sha256", &coreref, &pr);
#endif

        drbg = kzalloc(sizeof(struct drbg_state), GFP_KERNEL);
        if (!drbg)
                return -ENOMEM;

        /*
         * if the following tests fail, it is likely that there is a buffer
         * overflow as buf is much smaller than the requested or provided
         * string lengths -- in case the error handling does not succeed
         * we may get an OOPS. And we want to get an OOPS as this is a
         * grave bug.
         */

        /* get a valid instance of DRBG for following tests */
        ret = drbg_instantiate(drbg, NULL, coreref, pr);
        if (ret) {
                rc = ret;
                goto outbuf;
        }
        max_addtllen = drbg_max_addtl(drbg);
        max_request_bytes = drbg_max_request_bytes(drbg);
        drbg_string_fill(&addtl, buf, max_addtllen + 1);
        /* overflow addtllen with additonal info string */
        len = drbg_generate(drbg, buf, OUTBUFLEN, &addtl);
        BUG_ON(0 < len);
        /* overflow max_bits */
        len = drbg_generate(drbg, buf, (max_request_bytes + 1), NULL);
        BUG_ON(0 < len);
        drbg_uninstantiate(drbg);

        /* overflow max addtllen with personalization string */
        ret = drbg_instantiate(drbg, &addtl, coreref, pr);
        BUG_ON(0 == ret);
        /* test uninstantated DRBG */
        len = drbg_generate(drbg, buf, (max_request_bytes + 1), NULL);
        BUG_ON(0 < len);
        /* all tests passed */
        rc = 0;

        pr_devel("DRBG: Sanity tests for failure code paths successfully "
                 "completed\n");

        drbg_uninstantiate(drbg);
outbuf:
        kzfree(drbg);
        return rc;
#else /* CONFIG_CRYPTO_FIPS */
        return 0;
#endif /* CONFIG_CRYPTO_FIPS */
}

static struct crypto_alg drbg_algs[22];

/*
 * Fill the array drbg_algs used to register the different DRBGs
 * with the kernel crypto API. To fill the array, the information
 * from drbg_cores[] is used.
 */
static inline void __init drbg_fill_array(struct crypto_alg *alg,
                                          const struct drbg_core *core, int pr)
{
        int pos = 0;
        static int priority = 100;

        memset(alg, 0, sizeof(struct crypto_alg));
        memcpy(alg->cra_name, "stdrng", 6);
        if (pr) {
                memcpy(alg->cra_driver_name, "drbg_pr_", 8);
                pos = 8;
        } else {
                memcpy(alg->cra_driver_name, "drbg_nopr_", 10);
                pos = 10;
        }
        memcpy(alg->cra_driver_name + pos, core->cra_name,
               strlen(core->cra_name));

        alg->cra_priority = priority;
        priority++;
        /*
         * If FIPS mode enabled, the selected DRBG shall have the
         * highest cra_priority over other stdrng instances to ensure
         * it is selected.
         */
        if (fips_enabled)
                alg->cra_priority += 200;

        alg->cra_flags          = CRYPTO_ALG_TYPE_RNG;
        alg->cra_ctxsize        = sizeof(struct drbg_state);
        alg->cra_type           = &crypto_rng_type;
        alg->cra_module         = THIS_MODULE;
        alg->cra_init           = drbg_kcapi_init;
        alg->cra_exit           = drbg_kcapi_cleanup;
        alg->cra_u.rng.rng_make_random  = drbg_kcapi_random;
        alg->cra_u.rng.rng_reset        = drbg_kcapi_reset;
        alg->cra_u.rng.seedsize = 0;
}

static int __init drbg_init(void)
{
        unsigned int i = 0; /* pointer to drbg_algs */
        unsigned int j = 0; /* pointer to drbg_cores */
        int ret = -EFAULT;

        ret = drbg_healthcheck_sanity();
        if (ret)
                return ret;

        if (ARRAY_SIZE(drbg_cores) * 2 > ARRAY_SIZE(drbg_algs)) {
                pr_info("DRBG: Cannot register all DRBG types"
                        "(slots needed: %zu, slots available: %zu)\n",
                        ARRAY_SIZE(drbg_cores) * 2, ARRAY_SIZE(drbg_algs));
                return ret;
        }

        /*
         * each DRBG definition can be used with PR and without PR, thus
         * we instantiate each DRBG in drbg_cores[] twice.
         *
         * As the order of placing them into the drbg_algs array matters
         * (the later DRBGs receive a higher cra_priority) we register the
         * prediction resistance DRBGs first as the should not be too
         * interesting.
         */
        for (j = 0; ARRAY_SIZE(drbg_cores) > j; j++, i++)
                drbg_fill_array(&drbg_algs[i], &drbg_cores[j], 1);
        for (j = 0; ARRAY_SIZE(drbg_cores) > j; j++, i++)
                drbg_fill_array(&drbg_algs[i], &drbg_cores[j], 0);
        return crypto_register_algs(drbg_algs, (ARRAY_SIZE(drbg_cores) * 2));
}

void __exit drbg_exit(void)
{
        crypto_unregister_algs(drbg_algs, (ARRAY_SIZE(drbg_cores) * 2));
}

module_init(drbg_init);
module_exit(drbg_exit);
#ifndef CRYPTO_DRBG_HASH_STRING
#define CRYPTO_DRBG_HASH_STRING ""
#endif
#ifndef CRYPTO_DRBG_HMAC_STRING
#define CRYPTO_DRBG_HMAC_STRING ""
#endif
#ifndef CRYPTO_DRBG_CTR_STRING
#define CRYPTO_DRBG_CTR_STRING ""
#endif
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
MODULE_DESCRIPTION("NIST SP800-90A Deterministic Random Bit Generator (DRBG) "
                   "using following cores: "
                   CRYPTO_DRBG_HASH_STRING
                   CRYPTO_DRBG_HMAC_STRING
                   CRYPTO_DRBG_CTR_STRING);