crypto/prng.c - kernel/msm-5.4 - Gitiles

 /*
  * PRNG: Pseudo Random Number Generator
  *       Based on NIST Recommended PRNG From ANSI X9.31 Appendix A.2.4 using
  *       AES 128 cipher in RFC3686 ctr mode
  *
  *  (C) Neil Horman <nhorman@tuxdriver.com>
  *
  *  This program is free software; you can redistribute it and/or modify it
  *  under the terms of the GNU General Public License as published by the
  *  Free Software Foundation; either version 2 of the License, or (at your
  *  any later version.
  *
  *
  */

 #include <linux/err.h>
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/mm.h>
 #include <linux/slab.h>
 #include <linux/fs.h>
 #include <linux/scatterlist.h>
 #include <linux/string.h>
 #include <linux/crypto.h>
 #include <linux/highmem.h>
 #include <linux/moduleparam.h>
 #include <linux/jiffies.h>
 #include <linux/timex.h>
 #include <linux/interrupt.h>
 #include <linux/miscdevice.h>
 #include "prng.h"

 #define TEST_PRNG_ON_START 0

 #define DEFAULT_PRNG_KEY "0123456789abcdef1011"
 #define DEFAULT_PRNG_KSZ 20
 #define DEFAULT_PRNG_IV "defaultv"
 #define DEFAULT_PRNG_IVSZ 8
 #define DEFAULT_BLK_SZ 16
 #define DEFAULT_V_SEED "zaybxcwdveuftgsh"

 /*
  * Flags for the prng_context flags field
  */

 #define PRNG_FIXED_SIZE 0x1
 #define PRNG_NEED_RESET 0x2

 /*
  * Note: DT is our counter value
  * 	 I is our intermediate value
  *	 V is our seed vector
  * See http://csrc.nist.gov/groups/STM/cavp/documents/rng/931rngext.pdf
  * for implementation details
  */


 struct prng_context {
 	char *prng_key;
 	char *prng_iv;
 	spinlock_t prng_lock;
 	unsigned char rand_data[DEFAULT_BLK_SZ];
 	unsigned char last_rand_data[DEFAULT_BLK_SZ];
 	unsigned char DT[DEFAULT_BLK_SZ];
 	unsigned char I[DEFAULT_BLK_SZ];
 	unsigned char V[DEFAULT_BLK_SZ];
 	u32 rand_data_valid;
 	struct crypto_blkcipher *tfm;
 	u32 flags;
 };

 static int dbg;

 static void hexdump(char *note, unsigned char *buf, unsigned int len)
 {
 	if (dbg) {
 		printk(KERN_CRIT "%s", note);
 		print_hex_dump(KERN_CONT, "", DUMP_PREFIX_OFFSET,
 				16, 1,
 				buf, len, false);
 	}
 }

 #define dbgprint(format, args...) do {if(dbg) printk(format, ##args);} while(0)

 static void xor_vectors(unsigned char *in1, unsigned char *in2,
 		        unsigned char *out, unsigned int size)
 {
 	int i;

 	for (i=0;i<size;i++)
 		out[i] = in1[i] ^ in2[i];

 }
 /*
  * Returns DEFAULT_BLK_SZ bytes of random data per call
  * returns 0 if generation succeded, <0 if something went wrong
  */
 static int _get_more_prng_bytes(struct prng_context *ctx)
 {
 	int i;
 	struct blkcipher_desc desc;
 	struct scatterlist sg_in, sg_out;
 	int ret;
 	unsigned char tmp[DEFAULT_BLK_SZ];

 	desc.tfm = ctx->tfm;
 	desc.flags = 0;


 	dbgprint(KERN_CRIT "Calling _get_more_prng_bytes for context %p\n",ctx);

 	hexdump("Input DT: ", ctx->DT, DEFAULT_BLK_SZ);
 	hexdump("Input I: ", ctx->I, DEFAULT_BLK_SZ);
 	hexdump("Input V: ", ctx->V, DEFAULT_BLK_SZ);

 	/*
 	 * This algorithm is a 3 stage state machine
 	 */
 	for (i=0;i<3;i++) {

 		desc.tfm = ctx->tfm;
 		desc.flags = 0;
 		switch (i) {
 			case 0:
 				/*
 				 * Start by encrypting the counter value
 				 * This gives us an intermediate value I
 				 */
 				memcpy(tmp, ctx->DT, DEFAULT_BLK_SZ);
 				sg_init_one(&sg_out, &ctx->I[0], DEFAULT_BLK_SZ);
 				hexdump("tmp stage 0: ", tmp, DEFAULT_BLK_SZ);
 				break;
 			case 1:

 				/*
 				 * Next xor I with our secret vector V
 				 * encrypt that result to obtain our
 				 * pseudo random data which we output
 				 */
 				xor_vectors(ctx->I, ctx->V, tmp, DEFAULT_BLK_SZ);
 				sg_init_one(&sg_out, &ctx->rand_data[0], DEFAULT_BLK_SZ);
 				hexdump("tmp stage 1: ", tmp, DEFAULT_BLK_SZ);
 				break;
 			case 2:
 				/*
 				 * First check that we didn't produce the same random data
 				 * that we did last time around through this
 				 */
 				if (!memcmp(ctx->rand_data, ctx->last_rand_data, DEFAULT_BLK_SZ)) {
 					printk(KERN_ERR "ctx %p Failed repetition check!\n",
 						ctx);
 					ctx->flags |= PRNG_NEED_RESET;
 					return -1;
 				}
 				memcpy(ctx->last_rand_data, ctx->rand_data, DEFAULT_BLK_SZ);

 				/*
 				 * Lastly xor the random data with I
 				 * and encrypt that to obtain a new secret vector V
 				 */
 				xor_vectors(ctx->rand_data, ctx->I, tmp, DEFAULT_BLK_SZ);
 				sg_init_one(&sg_out, &ctx->V[0], DEFAULT_BLK_SZ);
 				hexdump("tmp stage 2: ", tmp, DEFAULT_BLK_SZ);
 				break;
 		}

 		/* Initialize our input buffer */
 		sg_init_one(&sg_in, &tmp[0], DEFAULT_BLK_SZ);

 		/* do the encryption */
 		ret = crypto_blkcipher_encrypt(&desc, &sg_out, &sg_in, DEFAULT_BLK_SZ);

 		/* And check the result */
 		if (ret) {
 			dbgprint(KERN_CRIT "Encryption of new block failed for context %p\n",ctx);
 			ctx->rand_data_valid = DEFAULT_BLK_SZ;
 			return -1;
 		}

 	}

 	/*
 	 * Now update our DT value
 	 */
 	for (i=DEFAULT_BLK_SZ-1;i>0;i--) {
 		ctx->DT[i] = ctx->DT[i-1];
 	}
 	ctx->DT[0] += 1;

 	dbgprint("Returning new block for context %p\n",ctx);
 	ctx->rand_data_valid = 0;

 	hexdump("Output DT: ", ctx->DT, DEFAULT_BLK_SZ);
 	hexdump("Output I: ", ctx->I, DEFAULT_BLK_SZ);
 	hexdump("Output V: ", ctx->V, DEFAULT_BLK_SZ);
 	hexdump("New Random Data: ", ctx->rand_data, DEFAULT_BLK_SZ);

 	return 0;
 }

 /* Our exported functions */
 int get_prng_bytes(char *buf, int nbytes, struct prng_context *ctx)
 {
 	unsigned long flags;
 	unsigned char *ptr = buf;
 	unsigned int byte_count = (unsigned int)nbytes;
 	int err;


 	if (nbytes < 0)
 		return -EINVAL;

 	spin_lock_irqsave(&ctx->prng_lock, flags);

 	err = -EFAULT;
 	if (ctx->flags & PRNG_NEED_RESET)
 		goto done;

 	/*
 	 * If the FIXED_SIZE flag is on, only return whole blocks of
 	 * pseudo random data
 	 */
 	err = -EINVAL;
 	if (ctx->flags & PRNG_FIXED_SIZE) {
 		if (nbytes < DEFAULT_BLK_SZ)
 			goto done;
 		byte_count = DEFAULT_BLK_SZ;
 	}

 	err = byte_count;

 	dbgprint(KERN_CRIT "getting %d random bytes for context %p\n",byte_count, ctx);


 remainder:
 	if (ctx->rand_data_valid == DEFAULT_BLK_SZ) {
 		if (_get_more_prng_bytes(ctx) < 0) {
 			memset(buf, 0, nbytes);
 			err = -EFAULT;
 			goto done;
 		}
 	}

 	/*
 	 * Copy up to the next whole block size
 	 */
 	if (byte_count < DEFAULT_BLK_SZ) {
 		for (;ctx->rand_data_valid < DEFAULT_BLK_SZ; ctx->rand_data_valid++) {
 			*ptr = ctx->rand_data[ctx->rand_data_valid];
 			ptr++;
 			byte_count--;
 			if (byte_count == 0)
 				goto done;
 		}
 	}

 	/*
 	 * Now copy whole blocks
 	 */
 	for(;byte_count >= DEFAULT_BLK_SZ; byte_count -= DEFAULT_BLK_SZ) {
 		if (_get_more_prng_bytes(ctx) < 0) {
 			memset(buf, 0, nbytes);
 			err = -1;
 			goto done;
 		}
 		memcpy(ptr, ctx->rand_data, DEFAULT_BLK_SZ);
 		ctx->rand_data_valid += DEFAULT_BLK_SZ;
 		ptr += DEFAULT_BLK_SZ;
 	}

 	/*
 	 * Now copy any extra partial data
 	 */
 	if (byte_count)
 		goto remainder;

 done:
 	spin_unlock_irqrestore(&ctx->prng_lock, flags);
 	dbgprint(KERN_CRIT "returning %d from get_prng_bytes in context %p\n",err, ctx);
 	return err;
 }
 EXPORT_SYMBOL_GPL(get_prng_bytes);

 struct prng_context *alloc_prng_context(void)
 {
 	struct prng_context *ctx=kzalloc(sizeof(struct prng_context), GFP_KERNEL);

 	spin_lock_init(&ctx->prng_lock);

 	if (reset_prng_context(ctx, NULL, NULL, NULL, NULL)) {
 		kfree(ctx);
 		ctx = NULL;
 	}

 	dbgprint(KERN_CRIT "returning context %p\n",ctx);
 	return ctx;
 }

 EXPORT_SYMBOL_GPL(alloc_prng_context);

 void free_prng_context(struct prng_context *ctx)
 {
 	crypto_free_blkcipher(ctx->tfm);
 	kfree(ctx);
 }
 EXPORT_SYMBOL_GPL(free_prng_context);

 int reset_prng_context(struct prng_context *ctx,
 		       unsigned char *key, unsigned char *iv,
 		       unsigned char *V, unsigned char *DT)
 {
 	int ret;
 	int iv_len;
 	int rc = -EFAULT;

 	spin_lock(&ctx->prng_lock);
 	ctx->flags |= PRNG_NEED_RESET;

 	if (key)
 		memcpy(ctx->prng_key,key,strlen(ctx->prng_key));
 	else
 		ctx->prng_key = DEFAULT_PRNG_KEY;

 	if (iv)
 		memcpy(ctx->prng_iv,iv, strlen(ctx->prng_iv));
 	else
 		ctx->prng_iv = DEFAULT_PRNG_IV;

 	if (V)
 		memcpy(ctx->V,V,DEFAULT_BLK_SZ);
 	else
 		memcpy(ctx->V,DEFAULT_V_SEED,DEFAULT_BLK_SZ);

 	if (DT)
 		memcpy(ctx->DT, DT, DEFAULT_BLK_SZ);
 	else
 		memset(ctx->DT, 0, DEFAULT_BLK_SZ);

 	memset(ctx->rand_data,0,DEFAULT_BLK_SZ);
 	memset(ctx->last_rand_data,0,DEFAULT_BLK_SZ);

 	if (ctx->tfm)
 		crypto_free_blkcipher(ctx->tfm);

 	ctx->tfm = crypto_alloc_blkcipher("rfc3686(ctr(aes))",0,0);
 	if (!ctx->tfm) {
 		dbgprint(KERN_CRIT "Failed to alloc crypto tfm for context %p\n",ctx->tfm);
 		goto out;
 	}

 	ctx->rand_data_valid = DEFAULT_BLK_SZ;

 	ret = crypto_blkcipher_setkey(ctx->tfm, ctx->prng_key, strlen(ctx->prng_key));
 	if (ret) {
 		dbgprint(KERN_CRIT "PRNG: setkey() failed flags=%x\n",
 			crypto_blkcipher_get_flags(ctx->tfm));
 		crypto_free_blkcipher(ctx->tfm);
 		goto out;
 	}

 	iv_len = crypto_blkcipher_ivsize(ctx->tfm);
 	if (iv_len) {
 		crypto_blkcipher_set_iv(ctx->tfm, ctx->prng_iv, iv_len);
 	}
 	rc = 0;
 	ctx->flags &= ~PRNG_NEED_RESET;
 out:
 	spin_unlock(&ctx->prng_lock);

 	return rc;

 }
 EXPORT_SYMBOL_GPL(reset_prng_context);

 /* Module initalization */
 static int __init prng_mod_init(void)
 {

 #ifdef TEST_PRNG_ON_START
 	int i;
 	unsigned char tmpbuf[DEFAULT_BLK_SZ];

 	struct prng_context *ctx = alloc_prng_context();
 	if (ctx == NULL)
 		return -EFAULT;
 	for (i=0;i<16;i++) {
 		if (get_prng_bytes(tmpbuf, DEFAULT_BLK_SZ, ctx) < 0) {
 			free_prng_context(ctx);
 			return -EFAULT;
 		}
 	}
 	free_prng_context(ctx);
 #endif

 	return 0;
 }

 static void __exit prng_mod_fini(void)
 {
 	return;
 }

 MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("Software Pseudo Random Number Generator");
 MODULE_AUTHOR("Neil Horman <nhorman@tuxdriver.com>");
 module_param(dbg, int, 0);
 MODULE_PARM_DESC(dbg, "Boolean to enable debugging (0/1 == off/on)");
 module_init(prng_mod_init);
 module_exit(prng_mod_fini);
	/*
	* PRNG: Pseudo Random Number Generator
	* Based on NIST Recommended PRNG From ANSI X9.31 Appendix A.2.4 using
	* AES 128 cipher in RFC3686 ctr mode
	*
	* (C) Neil Horman <nhorman@tuxdriver.com>
	*
	* This program is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License as published by the
	* Free Software Foundation; either version 2 of the License, or (at your
	* any later version.
	*
	*
	*/

	#include <linux/err.h>
	#include <linux/init.h>
	#include <linux/module.h>
	#include <linux/mm.h>
	#include <linux/slab.h>
	#include <linux/fs.h>
	#include <linux/scatterlist.h>
	#include <linux/string.h>
	#include <linux/crypto.h>
	#include <linux/highmem.h>
	#include <linux/moduleparam.h>
	#include <linux/jiffies.h>
	#include <linux/timex.h>
	#include <linux/interrupt.h>
	#include <linux/miscdevice.h>
	#include "prng.h"

	#define TEST_PRNG_ON_START 0

	#define DEFAULT_PRNG_KEY "0123456789abcdef1011"
	#define DEFAULT_PRNG_KSZ 20
	#define DEFAULT_PRNG_IV "defaultv"
	#define DEFAULT_PRNG_IVSZ 8
	#define DEFAULT_BLK_SZ 16
	#define DEFAULT_V_SEED "zaybxcwdveuftgsh"

	/*
	* Flags for the prng_context flags field
	*/

	#define PRNG_FIXED_SIZE 0x1
	#define PRNG_NEED_RESET 0x2

	/*
	* Note: DT is our counter value
	* I is our intermediate value
	* V is our seed vector
	* See http://csrc.nist.gov/groups/STM/cavp/documents/rng/931rngext.pdf
	* for implementation details
	*/


	struct prng_context {
	char *prng_key;
	char *prng_iv;
	spinlock_t prng_lock;
	unsigned char rand_data[DEFAULT_BLK_SZ];
	unsigned char last_rand_data[DEFAULT_BLK_SZ];
	unsigned char DT[DEFAULT_BLK_SZ];
	unsigned char I[DEFAULT_BLK_SZ];
	unsigned char V[DEFAULT_BLK_SZ];
	u32 rand_data_valid;
	struct crypto_blkcipher *tfm;
	u32 flags;
	};

	static int dbg;

	static void hexdump(char note, unsigned char buf, unsigned int len)
	{
	if (dbg) {
	printk(KERN_CRIT "%s", note);
	print_hex_dump(KERN_CONT, "", DUMP_PREFIX_OFFSET,
	16, 1,
	buf, len, false);
	}
	}

	#define dbgprint(format, args...) do {if(dbg) printk(format, ##args);} while(0)

	static void xor_vectors(unsigned char in1, unsigned char in2,
	unsigned char *out, unsigned int size)
	{
	int i;

	for (i=0;i<size;i++)
	out[i] = in1[i] ^ in2[i];

	}
	/*
	* Returns DEFAULT_BLK_SZ bytes of random data per call
	* returns 0 if generation succeded, <0 if something went wrong
	*/
	static int _get_more_prng_bytes(struct prng_context *ctx)
	{
	int i;
	struct blkcipher_desc desc;
	struct scatterlist sg_in, sg_out;
	int ret;
	unsigned char tmp[DEFAULT_BLK_SZ];

	desc.tfm = ctx->tfm;
	desc.flags = 0;


	dbgprint(KERN_CRIT "Calling _get_more_prng_bytes for context %p\n",ctx);

	hexdump("Input DT: ", ctx->DT, DEFAULT_BLK_SZ);
	hexdump("Input I: ", ctx->I, DEFAULT_BLK_SZ);
	hexdump("Input V: ", ctx->V, DEFAULT_BLK_SZ);

	/*
	* This algorithm is a 3 stage state machine
	*/
	for (i=0;i<3;i++) {

	desc.tfm = ctx->tfm;
	desc.flags = 0;
	switch (i) {
	case 0:
	/*
	* Start by encrypting the counter value
	* This gives us an intermediate value I
	*/
	memcpy(tmp, ctx->DT, DEFAULT_BLK_SZ);
	sg_init_one(&sg_out, &ctx->I[0], DEFAULT_BLK_SZ);
	hexdump("tmp stage 0: ", tmp, DEFAULT_BLK_SZ);
	break;
	case 1:

	/*
	* Next xor I with our secret vector V
	* encrypt that result to obtain our
	* pseudo random data which we output
	*/
	xor_vectors(ctx->I, ctx->V, tmp, DEFAULT_BLK_SZ);
	sg_init_one(&sg_out, &ctx->rand_data[0], DEFAULT_BLK_SZ);
	hexdump("tmp stage 1: ", tmp, DEFAULT_BLK_SZ);
	break;
	case 2:
	/*
	* First check that we didn't produce the same random data
	* that we did last time around through this
	*/
	if (!memcmp(ctx->rand_data, ctx->last_rand_data, DEFAULT_BLK_SZ)) {
	printk(KERN_ERR "ctx %p Failed repetition check!\n",
	ctx);
	ctx->flags \|= PRNG_NEED_RESET;
	return -1;
	}
	memcpy(ctx->last_rand_data, ctx->rand_data, DEFAULT_BLK_SZ);

	/*
	* Lastly xor the random data with I
	* and encrypt that to obtain a new secret vector V
	*/
	xor_vectors(ctx->rand_data, ctx->I, tmp, DEFAULT_BLK_SZ);
	sg_init_one(&sg_out, &ctx->V[0], DEFAULT_BLK_SZ);
	hexdump("tmp stage 2: ", tmp, DEFAULT_BLK_SZ);
	break;
	}

	/* Initialize our input buffer */
	sg_init_one(&sg_in, &tmp[0], DEFAULT_BLK_SZ);

	/* do the encryption */
	ret = crypto_blkcipher_encrypt(&desc, &sg_out, &sg_in, DEFAULT_BLK_SZ);

	/* And check the result */
	if (ret) {
	dbgprint(KERN_CRIT "Encryption of new block failed for context %p\n",ctx);
	ctx->rand_data_valid = DEFAULT_BLK_SZ;
	return -1;
	}

	}

	/*
	* Now update our DT value
	*/
	for (i=DEFAULT_BLK_SZ-1;i>0;i--) {
	ctx->DT[i] = ctx->DT[i-1];
	}
	ctx->DT[0] += 1;

	dbgprint("Returning new block for context %p\n",ctx);
	ctx->rand_data_valid = 0;

	hexdump("Output DT: ", ctx->DT, DEFAULT_BLK_SZ);
	hexdump("Output I: ", ctx->I, DEFAULT_BLK_SZ);
	hexdump("Output V: ", ctx->V, DEFAULT_BLK_SZ);
	hexdump("New Random Data: ", ctx->rand_data, DEFAULT_BLK_SZ);

	return 0;
	}

	/* Our exported functions */
	int get_prng_bytes(char buf, int nbytes, struct prng_context ctx)
	{
	unsigned long flags;
	unsigned char *ptr = buf;
	unsigned int byte_count = (unsigned int)nbytes;
	int err;


	if (nbytes < 0)
	return -EINVAL;

	spin_lock_irqsave(&ctx->prng_lock, flags);

	err = -EFAULT;
	if (ctx->flags & PRNG_NEED_RESET)
	goto done;

	/*
	* If the FIXED_SIZE flag is on, only return whole blocks of
	* pseudo random data
	*/
	err = -EINVAL;
	if (ctx->flags & PRNG_FIXED_SIZE) {
	if (nbytes < DEFAULT_BLK_SZ)
	goto done;
	byte_count = DEFAULT_BLK_SZ;
	}

	err = byte_count;

	dbgprint(KERN_CRIT "getting %d random bytes for context %p\n",byte_count, ctx);


	remainder:
	if (ctx->rand_data_valid == DEFAULT_BLK_SZ) {
	if (_get_more_prng_bytes(ctx) < 0) {
	memset(buf, 0, nbytes);
	err = -EFAULT;
	goto done;
	}
	}

	/*
	* Copy up to the next whole block size
	*/
	if (byte_count < DEFAULT_BLK_SZ) {
	for (;ctx->rand_data_valid < DEFAULT_BLK_SZ; ctx->rand_data_valid++) {
	*ptr = ctx->rand_data[ctx->rand_data_valid];
	ptr++;
	byte_count--;
	if (byte_count == 0)
	goto done;
	}
	}

	/*
	* Now copy whole blocks
	*/
	for(;byte_count >= DEFAULT_BLK_SZ; byte_count -= DEFAULT_BLK_SZ) {
	if (_get_more_prng_bytes(ctx) < 0) {
	memset(buf, 0, nbytes);
	err = -1;
	goto done;
	}
	memcpy(ptr, ctx->rand_data, DEFAULT_BLK_SZ);
	ctx->rand_data_valid += DEFAULT_BLK_SZ;
	ptr += DEFAULT_BLK_SZ;
	}

	/*
	* Now copy any extra partial data
	*/
	if (byte_count)
	goto remainder;

	done:
	spin_unlock_irqrestore(&ctx->prng_lock, flags);
	dbgprint(KERN_CRIT "returning %d from get_prng_bytes in context %p\n",err, ctx);
	return err;
	}
	EXPORT_SYMBOL_GPL(get_prng_bytes);

	struct prng_context *alloc_prng_context(void)
	{
	struct prng_context *ctx=kzalloc(sizeof(struct prng_context), GFP_KERNEL);

	spin_lock_init(&ctx->prng_lock);

	if (reset_prng_context(ctx, NULL, NULL, NULL, NULL)) {
	kfree(ctx);
	ctx = NULL;
	}

	dbgprint(KERN_CRIT "returning context %p\n",ctx);
	return ctx;
	}

	EXPORT_SYMBOL_GPL(alloc_prng_context);

	void free_prng_context(struct prng_context *ctx)
	{
	crypto_free_blkcipher(ctx->tfm);
	kfree(ctx);
	}
	EXPORT_SYMBOL_GPL(free_prng_context);

	int reset_prng_context(struct prng_context *ctx,
	unsigned char key, unsigned char iv,
	unsigned char V, unsigned char DT)
	{
	int ret;
	int iv_len;
	int rc = -EFAULT;

	spin_lock(&ctx->prng_lock);
	ctx->flags \|= PRNG_NEED_RESET;

	if (key)
	memcpy(ctx->prng_key,key,strlen(ctx->prng_key));
	else
	ctx->prng_key = DEFAULT_PRNG_KEY;

	if (iv)
	memcpy(ctx->prng_iv,iv, strlen(ctx->prng_iv));
	else
	ctx->prng_iv = DEFAULT_PRNG_IV;

	if (V)
	memcpy(ctx->V,V,DEFAULT_BLK_SZ);
	else
	memcpy(ctx->V,DEFAULT_V_SEED,DEFAULT_BLK_SZ);

	if (DT)
	memcpy(ctx->DT, DT, DEFAULT_BLK_SZ);
	else
	memset(ctx->DT, 0, DEFAULT_BLK_SZ);

	memset(ctx->rand_data,0,DEFAULT_BLK_SZ);
	memset(ctx->last_rand_data,0,DEFAULT_BLK_SZ);

	if (ctx->tfm)
	crypto_free_blkcipher(ctx->tfm);

	ctx->tfm = crypto_alloc_blkcipher("rfc3686(ctr(aes))",0,0);
	if (!ctx->tfm) {
	dbgprint(KERN_CRIT "Failed to alloc crypto tfm for context %p\n",ctx->tfm);
	goto out;
	}

	ctx->rand_data_valid = DEFAULT_BLK_SZ;

	ret = crypto_blkcipher_setkey(ctx->tfm, ctx->prng_key, strlen(ctx->prng_key));
	if (ret) {
	dbgprint(KERN_CRIT "PRNG: setkey() failed flags=%x\n",
	crypto_blkcipher_get_flags(ctx->tfm));
	crypto_free_blkcipher(ctx->tfm);
	goto out;
	}

	iv_len = crypto_blkcipher_ivsize(ctx->tfm);
	if (iv_len) {
	crypto_blkcipher_set_iv(ctx->tfm, ctx->prng_iv, iv_len);
	}
	rc = 0;
	ctx->flags &= ~PRNG_NEED_RESET;
	out:
	spin_unlock(&ctx->prng_lock);

	return rc;

	}
	EXPORT_SYMBOL_GPL(reset_prng_context);

	/* Module initalization */
	static int __init prng_mod_init(void)
	{

	#ifdef TEST_PRNG_ON_START
	int i;
	unsigned char tmpbuf[DEFAULT_BLK_SZ];

	struct prng_context *ctx = alloc_prng_context();
	if (ctx == NULL)
	return -EFAULT;
	for (i=0;i<16;i++) {
	if (get_prng_bytes(tmpbuf, DEFAULT_BLK_SZ, ctx) < 0) {
	free_prng_context(ctx);
	return -EFAULT;
	}
	}
	free_prng_context(ctx);
	#endif

	return 0;
	}

	static void __exit prng_mod_fini(void)
	{
	return;
	}

	MODULE_LICENSE("GPL");
	MODULE_DESCRIPTION("Software Pseudo Random Number Generator");
	MODULE_AUTHOR("Neil Horman <nhorman@tuxdriver.com>");
	module_param(dbg, int, 0);
	MODULE_PARM_DESC(dbg, "Boolean to enable debugging (0/1 == off/on)");
	module_init(prng_mod_init);
	module_exit(prng_mod_fini);