[PATCH v2 1/6] SP800-90A Deterministic Random Bit Generator

[Stephan Mueller <smueller@chronox.de>]

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.
 * Additional cipher primitives, such as Serpent or Twofish, can be
 * added to the DRBG without changing the implementation. The only
 * change necessary is to the DRBG definition given in the cores[]
 * array.

Changes to v1:

 * Overhauling code structure for simpler code as suggested by Rafael Aquini:
     - each DRBG type exports only two crypto functions,
     - the individual DRBG implementations structure closely according to
       SP 800-90A,
     - using struct drbg_string to refer to buffers to avoid too many
       function parameters and prevent multiple data structure conversions
     - use inline more thoroughly
     - replace macros with small inline functions
     - remove unnecessary indirections
     - replace of large stack variables with a scratch buffer allocated at
       the beginning of DRBG operation -- see comments about scratchpad
       throughout the code
 * Revamping DRBG flags usage: flags are only intended to select the appropriate
   DRBG type and DRBG strength. Flags are not intended to be visible to
   external callers.
 * Adding comments throughout the code to refer to the appropriate steps
   documented in SP 800-90A.
 * Fix invocation of kernel crypto API hash
 * Fix coding style and apply scripts/checkpatch.pl
 * Change locking approach: only very small code sections are guarded by a lock.
   This implies that the entire DRBG operates on a shadow copy of the original
   DRBG state -- see comments for drbg_copy_drbg
 * Perform thorough testing:
   - Performing of a full scale CAVS test with CAVS interface available at
     http://www.chronox.de/drbg.html
   - Performing tests by obtaining data which is not a multiple of cipher block
     size and check it with the ent tool to ensure that the generation loop
     does not reuse stale buffers to avoid errors like CVE-2013-4345.

Signed-off-by: Stephan Mueller <smueller@chronox.de>
---
 create mode 100644 crypto/drbg.c

diff --git a/crypto/drbg.c b/crypto/drbg.c
new file mode 100644
index 0000000..808852b
--- /dev/null
+++ b/crypto/drbg.c
@@ -0,0 +1,1790 @@
+/*
+ * 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 = "some-string";
+ *
+ * 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];
+ * string drbg_string addtl;
+ *
+ * drbg_string_fill(&addtl, "some-string", strlen(addtl)); *
+ * 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
+ ***************************************************************/
+
+const struct drbg_core cores[] = {
+		/* Hash DRBGs */
+#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",
+		.cra_driver_name = "sha1",
+		.backend_cra_name = "sha1",
+	}, {
+		.flags = DRBG_HASH | DRBG_STRENGTH256,
+		.statelen = 55, /* 440 bits */
+		.max_addtllen = 35,
+		.max_bits = 19,
+		.max_req = 48,
+		.blocklen_bytes = 32,
+		.cra_name = "sha256",
+		.cra_driver_name = "sha256",
+		.backend_cra_name = "sha256",
+	}, {
+		.flags = DRBG_HASH | DRBG_STRENGTH256,
+		.statelen = 111, /* 888 bits */
+		.max_addtllen = 35,
+		.max_bits = 19,
+		.max_req = 48,
+		.blocklen_bytes = 48,
+		.cra_name = "sha384",
+		.cra_driver_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",
+		.cra_driver_name = "sha512",
+		.backend_cra_name = "sha512",
+	},
+#endif /* CONFIG_CRYPTO_DRBG_HASH */
+#ifdef CONFIG_CRYPTO_DRBG_HMAC
+	{
+		/* HMAC DRBGs */
+		.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)",
+		.cra_driver_name = "hmac_sha1",
+		.backend_cra_name = "hmac(sha1)",
+	}, {
+		.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)",
+		.cra_driver_name = "hmac_sha256",
+		.backend_cra_name = "hmac(sha256)",
+	}, {
+		.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)",
+		.cra_driver_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)",
+		.cra_driver_name = "hmac_sha512",
+		.backend_cra_name = "hmac(sha512)",
+	},
+#endif /* CONFIG_CRYPTO_DRBG_HMAC */
+#ifdef CONFIG_CRYPTO_DRBG_CTR
+	{
+		/* block ciphers */
+		.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)",
+		.cra_driver_name = "ctr_aes128",
+		.backend_cra_name = "ecb(aes)",
+	}, {
+		/* block ciphers */
+		.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)",
+		.cra_driver_name = "ctr_aes192",
+		.backend_cra_name = "ecb(aes)",
+	}, {
+		/* block ciphers */
+		.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)",
+		.cra_driver_name = "ctr_aes256",
+		.backend_cra_name = "ecb(aes)",
+	},
+#endif /* CONFIG_CRYPTO_DRBG_CTR */
+};
+
+/******************************************************************
+ * 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 0 on error
+ */
+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 0;
+	}
+}
+
+/*
+ * 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,
+				     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));
+	/* invert the memcmp result, because the test shall pass when the
+	 * two compared values do not match */
+	if (ret)
+		return true;
+	else
+		return false;
+#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,
+				unsigned char *add, size_t addlen)
+{
+	/* implied: dstlen > addlen */
+	unsigned char *dstptr, *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, unsigned char *key,
+			  unsigned char *outval, 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, 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. If we are at the end of the current data
+			 * set, we have to start using the next data set 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 *out, 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 = out + drbg_statelen(drbg);
+	unsigned char *iv = pad + drbg_blocklen(drbg);
+	unsigned char *temp = iv + drbg_blocklen(drbg);
+	size_t padlen = 1; /* already reserve space for 0x80 */
+	unsigned int templen = 0;
+	/* 10.4.2 step 7 */
+	unsigned int i = 0;
+	/* 10.4.2 step 8 */
+	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 */
+	while (0 != ((8 + inputlen + padlen) % (drbg_blocklen(drbg))))
+		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, 8);
+	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 */
+	/* implicit key len with seedlen - blocklen according to table 3 */
+	X = temp + (drbg_keylen(drbg));
+	drbg_string_fill(&cipherin, X, drbg_blocklen(drbg));
+
+	/* 10.4.2 step 12: overwriting of outval */
+
+	/* 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 -- check for 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(out + 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 step 2 and 3 -- are already covered as we memset(0)
+	 * 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 */
+		/* using target of temp + len: 10.2.1.2 step 2.3 and 3 */
+		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 unsigned int drbg_ctr_generate(struct drbg_state *drbg,
+				      unsigned char *buf, unsigned int buflen,
+				      struct drbg_string *addtl)
+{
+	unsigned int len = 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;
+		if (drbg_ctr_update(drbg, addtl, 1))
+			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) {
+		unsigned int outlen = 0;
+		/* 10.2.1.5.2 step 4.2 */
+		if (drbg_kcapi_sym(drbg, drbg->C, drbg->scratchpad, &data)) {
+			len = 0;
+			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 */
+	/*TODO the DF function is called again since according to step
+	 * 2, the "additional_input" after step 2 is the output of the DF
+	 * function -- when we save the DF output as a replacement
+	 * for the addtl_input data, we do not need to call the DF again here */
+	if (addtl)
+		addtl->next = NULL;
+	if (drbg_ctr_update(drbg, addtl, 1))
+		return 0;
+
+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, unsigned char *key,
+			   unsigned char *outval, 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 already implicitly covered with
+		 * the initial memset(0) of drbg->C */
+		memset(drbg->C, 0, drbg_statelen(drbg));
+		memset(drbg->V, 1, drbg_statelen(drbg));
+	}
+
+	/* build linked list which implements the concatenation and fill
+	 * first part*/
+	drbg_string_fill(&seed1, drbg->V, drbg_statelen(drbg));
+	/* buffer will be filled in for loop below with one byte */
+	drbg_string_fill(&seed2, NULL, 1);
+	seed1.next = &seed2;
+	/* seed may be NULL */
+	seed2.next = seed;
+
+	drbg_string_fill(&cipherin, drbg->V, drbg_statelen(drbg));
+	/* we execute two rounds of V/K massaging */
+	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 unsigned int drbg_hmac_generate(struct drbg_state *drbg,
+				       unsigned char *buf,
+				       unsigned int buflen,
+				       struct drbg_string *addtl)
+{
+	unsigned int len = 0;
+	struct drbg_string data;
+
+	/* 10.1.2.5 step 2 */
+	if (addtl && 0 < addtl->len) {
+		addtl->next = NULL;
+		if (drbg_hmac_update(drbg, addtl, 1))
+			return 0;
+	}
+
+	drbg_string_fill(&data, drbg->V, drbg_statelen(drbg));
+	while (len < buflen) {
+		unsigned int outlen = 0;
+		/* 10.1.2.5 step 4.1 */
+		if (drbg_kcapi_hash(drbg, drbg->C, drbg->V, &data))
+			return 0;
+		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;
+	if (drbg_hmac_update(drbg, addtl, 1))
+		return 0;
+
+	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)
+ */
+/* 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: string length is concatenation of
+		 * 1 byte, V and seed (which is concatenated entropy/addtl
+		 * input)
+		 */
+		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 -- concatenation  */
+	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 -- df operation */
+	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 -- concatenation */
+	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;
+	/* 10.1.1.4 step 2a -- cipher invocation */
+	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 unsigned int drbg_hash_hashgen(struct drbg_state *drbg,
+				      unsigned char *buf,
+				      unsigned int buflen)
+{
+	unsigned int len = 0;
+	unsigned char *src = drbg->scratchpad;
+	unsigned char *dst = drbg->scratchpad + drbg_statelen(drbg);
+	struct drbg_string data;
+	unsigned char prefix = DRBG_PREFIX1;
+
+	/* use the scratchpad as a lookaside buffer */
+	memset(drbg->scratchpad, 0,
+	       (drbg_statelen(drbg) + drbg_blocklen(drbg)));
+	memcpy(drbg->scratchpad, 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 */
+		if (drbg_kcapi_hash(drbg, NULL, dst, &data)) {
+			len = 0;
+			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 unsigned int drbg_hash_generate(struct drbg_state *drbg,
+				       unsigned char *buf, unsigned int buflen,
+				       struct drbg_string *addtl)
+{
+	unsigned int len = 0;
+	unsigned char req[8];
+	unsigned char prefix = DRBG_PREFIX3;
+	struct drbg_string data1, data2;
+
+	/*
+	 * scratchpad usage: drbg_hash_process_addtl uses the scratchpad, but
+	 * fully completes before returning. Thus, we can reuse the scratchpad
+	 */
+	/* 10.1.1.4 step 2 */
+	if (drbg_hash_process_addtl(drbg, addtl))
+		return 0;
+	/* 10.1.1.4 step 3 -- invocation of the Hashgen function defined in
+	 * 10.1.1.4 */
+	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;
+	if (drbg_kcapi_hash(drbg, NULL, drbg->scratchpad, &data1)) {
+		len = 0;
+		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;
+	struct drbg_string *data2;
+
+	/* 9.1 / 9.2 / 9.3.1 step 3 */
+	if (pers && pers->len > (drbg_max_addtl(drbg)))
+		return -EINVAL;
+
+	if (drbg->test_data) {
+		data1.buf = drbg->test_data->testentropy->buf;
+		data1.len = drbg->test_data->testentropy->len;
+		data1.next = NULL;
+	} 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) / 8);
+		if (!entropylen)
+			return -EFAULT;
+		if (!reseed)
+			/* make sure we round up strength/2 in
+			 * case it is not divisible by 2 */
+			entropylen = ((entropylen + 1) / 2) * 3;
+
+		entropy = kzalloc(entropylen, GFP_KERNEL);
+		if (!entropy)
+			return -ENOMEM;
+		get_random_bytes(entropy, entropylen);
+		drbg_string_fill(&data1, entropy, entropylen);
+	}
+
+	/* concatenation of entropy with personalization str / addtl input) */
+	if (pers && 0 < pers->len) {
+		data2 = pers;
+		data2->next = NULL;
+		data1.next = data2;
+	}
+
+	ret = drbg->d_ops->update(drbg, &data1, 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);	/* 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
+ */
+
+/*
+ * Copy the DRBG state
+ */
+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;
+	/* no copy of scratchpad */
+	/* priv_data is initialized with call to crypto_init */
+	/* d_ops are set outside, as the struct is const */
+	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
+	/* test_data is set outside, as the struct is const */
+}
+/*
+ * Generate shadow copy of the DRBG state
+ */
+static int drbg_make_shadow(struct drbg_state *drbg, struct drbg_state **shadow)
+{
+	int ret = -ENOMEM;
+	struct drbg_state *tmp = NULL;
+
+	/* some sanity checks */
+	if (!drbg || !drbg->core || !drbg->V || !drbg->C)
+		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 */
+	tmp->core = drbg->core;
+
+	ret = drbg_alloc_state(tmp);
+	if (ret)
+		goto err;
+
+	spin_lock_bh(&drbg->drbg_lock);
+	drbg_copy_drbg(drbg, tmp);
+	tmp->d_ops = drbg->d_ops;
+	/* 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;
+}
+
+/*
+ * Restore shadow state into original DRBG state
+ */
+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 unsigned int drbg_generate(struct drbg_state *drbg,
+				  unsigned char *buf, unsigned int buflen,
+				  struct drbg_string *addtl)
+{
+	unsigned int len = 0;
+	struct drbg_state *shadow = NULL;
+
+	if (0 == buflen || !buf)
+		return 0;
+	if (addtl && NULL == addtl->buf && 0 < addtl->len)
+		return 0;
+
+	if (drbg_make_shadow(drbg, &shadow))
+		return 0;
+	/* 9.3.1 step 2 */
+	if (buflen > (drbg_max_request_bytes(shadow)))
+		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)))
+		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 -- 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 && shadow->d_ops->crypto_init(shadow))
+		goto err;
+
+	if (shadow->pr || !shadow->seeded) {
+		/* 9.3.1 steps 7.1 through 7.3 */
+		if (drbg_seed(shadow, addtl, true))
+			goto err;
+		/* 9.3.1 step 7.4 */
+		addtl = NULL;
+	}
+	/* 9.3.1 step 8 and 10 */
+	len = drbg->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++;
+
+err:
+	if (shadow->d_ops->crypto_fini)
+		shadow->d_ops->crypto_fini(shadow);
+	drbg_restore_shadow(drbg, &shadow);
+	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
+ * @flags Flags defining the requested DRBG type and cipher type. The flags
+ *	  are defined in drbg.h and may be XORed. Beware, if you XOR multiple
+ *	  cipher types together, the code picks the core on a first come first
+ *	  serve basis as it iterates through the available cipher cores and
+ *	  uses the one with the first match. The minimum required flags are:
+ *	  cipher type flag
+ *
+ * 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;
+
+	drbg->core = &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 -- see
+	 * drbg_sec_strength() */
+
+	/* 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 */
+
+	/* no allocation of drbg as this is done by the kernel crypto API */
+	ret = drbg_alloc_state(drbg);
+	if (ret)
+		return ret;
+
+	ret = -EFAULT;
+	/* allocate cipher handle */
+	if (drbg->d_ops->crypto_init && drbg->d_ops->crypto_init(drbg))
+		goto err;
+	/* 9.1 step 6 through 11 */
+	ret = drbg_seed(drbg, pers, false);
+	/* deallocate cipher handle */
+	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);
+	/* no freeing of drbg as this is done by the kernel crypto API */
+	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)) {
+		printk(KERN_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, unsigned char *key,
+			   unsigned char *outval, struct drbg_string *in)
+{
+	struct sdesc *sdesc = (struct sdesc *)drbg->priv_data;
+
+	if (key)
+		crypto_shash_setkey(sdesc->shash.tfm, key, drbg_statelen(drbg));
+	crypto_shash_init(&sdesc->shash);
+	for (; NULL != in; in = in->next)
+		crypto_shash_update(&sdesc->shash, in->buf, in->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)) {
+		printk(KERN_INFO "drbg: could not allocate cipher TFM handle\n");
+		return PTR_ERR(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, unsigned char *key,
+			  unsigned char *outval, 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)));
+	/* in is only component */
+	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 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_name,
+					 int *coreref, bool *pr)
+{
+	int i = 0;
+	size_t start = 0;
+	int len = 0;
+
+	*pr = true;
+	/* disassemble the names */
+	if (0 == memcmp(cra_name, "drbg(nopr(", 10)) {
+		start = 10;
+		*pr = false;
+	} else if (0 == memcmp(cra_name, "drbg(pr(", 8)) {
+		start = 8;
+	} else {
+		return;
+	}
+
+	/* remove the first part and the closing parenthesis */
+	len = strlen(cra_name) - start - 2;
+	for (i = 0; ARRAY_SIZE(cores) > i; i++) {
+		if (0 == memcmp(cra_name + start, cores[i].cra_name, len)) {
+			*coreref = i;
+			return;
+		}
+	}
+}
+
+/*
+ * Initialize one DRBG invoked by the kernel crypto API
+ *
+ * Function uses the kernel crypto API cra_name to look up
+ * the flags to instantiate the DRBG
+ */
+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(drbg, rdata, dlen, NULL);
+	} else {
+		struct drbg_gen *data = (struct drbg_gen *)rdata;
+		/* catch NULL pointer */
+		if (!data)
+			return 0;
+		drbg_set_testdata(drbg, data->test_data);
+		return drbg_generate(drbg, data->outbuf, data->outlen,
+				     data->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_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);
+		return drbg_instantiate(drbg, data->addtl, coreref, pr);
+	}
+}
+
+/***************************************************************
+ * Kernel module: code to load the module
+ ***************************************************************/
+
+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 cores[] is used.
+ */
+static inline void drbg_fill_array(unsigned long i, unsigned long j, int pr)
+{
+	int pos = 0;
+
+	memset(&drbg_algs[i], 0, sizeof(struct crypto_alg));
+	if (pr) {
+		memcpy(drbg_algs[i].cra_name, "drbg(pr(", 8);
+		memcpy(drbg_algs[i].cra_driver_name, "drbg_pr_", 8);
+		pos = 8;
+	} else {
+		memcpy(drbg_algs[i].cra_name, "drbg(nopr(", 10);
+		memcpy(drbg_algs[i].cra_driver_name, "drbg_nopr_", 10);
+		pos = 10;
+	}
+	memcpy(drbg_algs[i].cra_name + pos, cores[j].cra_name,
+	       strlen(cores[j].cra_name));
+	memcpy(drbg_algs[i].cra_name + pos + strlen(cores[j].cra_name), "))", 2);
+	memcpy(drbg_algs[i].cra_driver_name + pos,
+	       cores[j].cra_driver_name, strlen(cores[j].cra_driver_name));
+	drbg_algs[i].cra_priority	= 100;
+	drbg_algs[i].cra_flags	 = CRYPTO_ALG_TYPE_RNG;
+	drbg_algs[i].cra_ctxsize = sizeof(struct drbg_state);
+	drbg_algs[i].cra_type	 = &crypto_rng_type;
+	drbg_algs[i].cra_module	 = THIS_MODULE;
+	drbg_algs[i].cra_init	 = drbg_kcapi_init;
+	drbg_algs[i].cra_exit	 = drbg_kcapi_cleanup;
+	drbg_algs[i].cra_u.rng.rng_make_random	= drbg_kcapi_random;
+	drbg_algs[i].cra_u.rng.rng_reset	= drbg_kcapi_reset;
+	drbg_algs[i].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 cores */
+
+	if (ARRAY_SIZE(cores) * 2 > ARRAY_SIZE(drbg_algs))
+		printk(KERN_INFO "drbg: Not all available DRBGs registered"
+		       "(slots needed: %lu, slots available: %lu)\n",
+		       ARRAY_SIZE(cores) * 2, ARRAY_SIZE(drbg_algs));
+
+	/* each DRBG definition can be used with PR and without PR, thus
+	 * we instantiate each DRBG in cores[] twice */
+	for (j = 0; ARRAY_SIZE(cores) > j; j++) {
+		drbg_fill_array(i, j, 1);
+		i++;
+		drbg_fill_array(i, j, 0);
+		i++;
+	}
+	return crypto_register_algs(drbg_algs, (ARRAY_SIZE(cores) * 2));
+}
+
+void __exit drbg_exit(void)
+{
+	crypto_unregister_algs(drbg_algs, (ARRAY_SIZE(cores) * 2));
+}
+
+module_init(drbg_init);
+module_exit(drbg_exit);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
+MODULE_DESCRIPTION("NIST SP800-90A Deterministic Random Bit Generator (DRBG) using following cores:"
+#ifdef CONFIG_CRYPTO_DRBG_HMAC
+"HMAC "
+#endif
+#ifdef CONFIG_CRYPTO_DRBG_HASH
+"Hash "
+#endif
+#ifdef CONFIG_CRYPTO_DRBG_CTR
+"CTR"
+#endif
+);