crypto: drbg - SP800-90A Deterministic Random Bit Generator

This is a clean-room implementation of the DRBG defined in SP800-90A.
All three viable DRBGs defined in the standard are implemented:

 * HMAC: This is the leanest DRBG and compiled per default
 * Hash: The more complex DRBG can be enabled at compile time
 * CTR: The most complex DRBG can also be enabled at compile time

The DRBG implementation offers the following:

 * All three DRBG types are implemented with a derivation function.
 * All DRBG types are available with and without prediction resistance.
 * All SHA types of SHA-1, SHA-256, SHA-384, SHA-512 are available for
   the HMAC and Hash DRBGs.
 * All AES types of AES-128, AES-192 and AES-256 are available for the
   CTR DRBG.
 * A self test is implemented with drbg_healthcheck().
 * The FIPS 140-2 continuous self test is implemented.

Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 2007 insertions, 0 deletions

diff --git a/crypto/drbg.c b/crypto/drbg.c
new file mode 100644
index 000000000000..faaa2cefeeed
--- /dev/null
+++ b/crypto/drbg.c
@@ -0,0 +1,2007 @@
+/*
+ * 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>
+
+#if !defined(CONFIG_CRYPTO_DRBG_HASH) && \
+	!defined(CONFIG_CRYPTO_DRBG_HMAC) && \
+	!defined(CONFIG_CRYPTO_DRBG_CTR)
+#warning "The DRBG code is useless without compiling at least one DRBG type"
+#endif
+
+/***************************************************************
+ * 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
+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 drbg_string *in)
+{
+	int ret = -EFAULT;
+	struct drbg_string *curr = in;
+	size_t inpos = curr->len;
+	const unsigned char *pos = curr->buf;
+	struct drbg_string data;
+
+	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 */
+	while (inpos) {
+		short cnt = 0;
+		/* 10.4.3 step 4.1 */
+		for (cnt = 0; cnt < drbg_blocklen(drbg); cnt++) {
+			out[cnt] ^= *pos;
+			pos++; inpos--;
+			/*
+			 * The following branch implements the linked list
+			 * iteration of drbg_string *in. If we are at the
+			 * end of the current list member, we have to start
+			 * using the next member if available. The inpos
+			 * value always points to the current byte and will
+			 * be zero if we have processed the last byte of
+			 * the last linked list member.
+			 */
+			if (0 == inpos) {
+				curr = curr->next;
+				if (NULL != curr) {
+					pos = curr->buf;
+					inpos = curr->len;
+				} else {
+					inpos = 0;
+					break;
+				}
+			}
+		}
+		/* 10.4.3 step 4.2 */
+		ret = drbg_kcapi_sym(drbg, key, out, &data);
+		if (ret)
+			return ret;
+		/* 10.4.3 step 2 */
+	}
+	return 0;
+}
+
+/*
+ * 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_keylen(drbg) + drbg_blocklen(drbg) ==
+ *				drbg_statelen(drbg))
+ */
+
+/* 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 drbg_string *addtl)
+{
+	int ret = -EFAULT;
+	unsigned char L_N[8];
+	/* S3 is input */
+	struct drbg_string S1, S2, S4, cipherin;
+	struct drbg_string *tempstr = addtl;
+	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;
+
+	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 */
+	for (; NULL != tempstr; tempstr = tempstr->next)
+		inputlen += tempstr->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));
+	drbg_string_fill(&S2, L_N, sizeof(L_N));
+	drbg_string_fill(&S4, pad, padlen);
+	S1.next = &S2;
+	S2.next = addtl;
+
+	/*
+	 * splice in addtl between S2 and S4 -- we place S4 at the end of the
+	 * input data chain
+	 */
+	tempstr = addtl;
+	for (; NULL != tempstr; tempstr = tempstr->next)
+		if (NULL == tempstr->next)
+			break;
+	tempstr->next = &S4;
+
+	/* 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, &S1);
+		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 */
+static int drbg_ctr_update(struct drbg_state *drbg,
+			   struct drbg_string *addtl, 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));
+	memset(df_data, 0, drbg_statelen(drbg));
+
+	/* 10.2.1.3.2 step 2 and 10.2.1.4.2 step 2 */
+	if (addtl && 0 < addtl->len) {
+		ret = drbg_ctr_df(drbg, df_data, drbg_statelen(drbg),
+				  addtl);
+		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));
+	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) {
+		addtl->next = NULL;
+		ret = drbg_ctr_update(drbg, addtl, 1);
+		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 */
+	if (addtl)
+		addtl->next = NULL;
+	/*
+	 * The following call invokes the DF function again which could be
+	 * optimized. In step 2, the "additional_input" after step 2 is the
+	 * output of the DF function. If this result would be saved, the DF
+	 * function would not need to be invoked again at this point.
+	 */
+	ret = drbg_ctr_update(drbg, addtl, 1);
+	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 drbg_string *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
+/* update function of HMAC DRBG as defined in 10.1.2.2 */
+static int drbg_hmac_update(struct drbg_state *drbg,
+			    struct drbg_string *seed, int reseed)
+{
+	int ret = -EFAULT;
+	int i = 0;
+	struct drbg_string seed1, seed2, cipherin;
+
+	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));
+	/* buffer of seed2 will be filled in for loop below with one byte */
+	drbg_string_fill(&seed2, NULL, 1);
+	seed1.next = &seed2;
+	/* input data of seed is allowed to be NULL at this point */
+	seed2.next = seed;
+
+	drbg_string_fill(&cipherin, drbg->V, drbg_statelen(drbg));
+	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, &seed1);
+		if (ret)
+			return ret;
+
+		/* 10.1.2.2 step 2 and 5 -- HMAC for V */
+		ret = drbg_kcapi_hash(drbg, drbg->C, drbg->V, &cipherin);
+		if (ret)
+			return ret;
+
+		/* 10.1.2.2 step 3 */
+		if (!seed || 0 == seed->len)
+			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;
+
+	/* 10.1.2.5 step 2 */
+	if (addtl && 0 < addtl->len) {
+		addtl->next = NULL;
+		ret = drbg_hmac_update(drbg, addtl, 1);
+		if (ret)
+			return ret;
+	}
+
+	drbg_string_fill(&data, drbg->V, drbg_statelen(drbg));
+	while (len < buflen) {
+		unsigned int outlen = 0;
+		/* 10.1.2.5 step 4.1 */
+		ret = drbg_kcapi_hash(drbg, drbg->C, drbg->V, &data);
+		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)
+		addtl->next = NULL;
+	ret = drbg_hmac_update(drbg, addtl, 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
+/*
+ * 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 drbg_string *entropy)
+{
+	int ret = 0;
+	size_t len = 0;
+	unsigned char input[5];
+	unsigned char *tmp = drbg->scratchpad + drbg_statelen(drbg);
+	struct drbg_string data1;
+
+	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(&data1, input, 5);
+	data1.next = entropy;
+
+	/* 10.4.1 step 4 */
+	while (len < outlen) {
+		short blocklen = 0;
+		/* 10.4.1 step 4.1 */
+		ret = drbg_kcapi_hash(drbg, NULL, tmp, &data1);
+		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 drbg_string *seed,
+			    int reseed)
+{
+	int ret = 0;
+	struct drbg_string data1, data2;
+	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);
+		drbg_string_fill(&data2, V, drbg_statelen(drbg));
+		data1.next = &data2;
+		data2.next = seed;
+	} else {
+		drbg_string_fill(&data1, seed->buf, seed->len);
+		data1.next = seed->next;
+	}
+
+	/* 10.1.1.2 / 10.1.1.3 step 2 and 3 */
+	ret = drbg_hash_df(drbg, drbg->V, drbg_statelen(drbg), &data1);
+	if (ret)
+		goto out;
+
+	/* 10.1.1.2 / 10.1.1.3 step 4  */
+	prefix = DRBG_PREFIX0;
+	drbg_string_fill(&data1, &prefix, 1);
+	drbg_string_fill(&data2, drbg->V, drbg_statelen(drbg));
+	data1.next = &data2;
+	/* 10.1.1.2 / 10.1.1.3 step 4 */
+	ret = drbg_hash_df(drbg, drbg->C, drbg_statelen(drbg), &data1);
+
+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;
+	struct drbg_string *data3;
+	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));
+	data3 = addtl;
+	data1.next = &data2;
+	data2.next = data3;
+	data3->next = NULL;
+	ret = drbg_kcapi_hash(drbg, NULL, drbg->scratchpad, &data1);
+	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;
+	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));
+	while (len < buflen) {
+		unsigned int outlen = 0;
+		/* 10.1.1.4 step hashgen 4.1 */
+		ret = drbg_kcapi_hash(drbg, NULL, dst, &data);
+		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;
+
+	/* 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);
+	drbg_string_fill(&data2, drbg->V, drbg_statelen(drbg));
+	data1.next = &data2;
+	ret = drbg_kcapi_hash(drbg, NULL, drbg->scratchpad, &data1);
+	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 d