crypto: prng - Deterministic CPRNG
This patch adds a cryptographic pseudo-random number generator based on CTR(AES-128). It is meant to be used in cases where a deterministic CPRNG is required. One of the first applications will be as an input in the IPsec IV generation process. Signed-off-by: Neil Horman <nhorman@tuxdriver.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Neil Horman
Herbert Xu
parent
166247f46a
commit
b8454eebe3
4 changed files with 447 additions and 1 deletions
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@ -666,6 +666,15 @@ config CRYPTO_LZO
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help
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This is the LZO algorithm.
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comment "Random Number Generation"
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config CRYPTO_PRNG
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tristate "Pseudo Random Number Generation for Cryptographic modules"
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help
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This option enables the generic pseudo random number generator
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for cryptographic modules. Uses the Algorithm specified in
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ANSI X9.31 A.2.4
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source "drivers/crypto/Kconfig"
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endif # if CRYPTO
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@ -69,7 +69,7 @@ obj-$(CONFIG_CRYPTO_MICHAEL_MIC) += michael_mic.o
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obj-$(CONFIG_CRYPTO_CRC32C) += crc32c.o
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obj-$(CONFIG_CRYPTO_AUTHENC) += authenc.o
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obj-$(CONFIG_CRYPTO_LZO) += lzo.o
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obj-$(CONFIG_CRYPTO_PRNG) += prng.o
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obj-$(CONFIG_CRYPTO_TEST) += tcrypt.o
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#
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410
crypto/prng.c
Normal file
410
crypto/prng.c
Normal file
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@ -0,0 +1,410 @@
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/*
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* PRNG: Pseudo Random Number Generator
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* Based on NIST Recommended PRNG From ANSI X9.31 Appendix A.2.4 using
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* AES 128 cipher in RFC3686 ctr mode
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*
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* (C) Neil Horman <nhorman@tuxdriver.com>
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2 of the License, or (at your
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* any later version.
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*
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*
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*/
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#include <linux/err.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/mm.h>
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#include <linux/slab.h>
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#include <linux/fs.h>
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#include <linux/scatterlist.h>
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#include <linux/string.h>
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#include <linux/crypto.h>
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#include <linux/highmem.h>
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#include <linux/moduleparam.h>
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#include <linux/jiffies.h>
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#include <linux/timex.h>
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#include <linux/interrupt.h>
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#include <linux/miscdevice.h>
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#include "prng.h"
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#define TEST_PRNG_ON_START 0
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#define DEFAULT_PRNG_KEY "0123456789abcdef1011"
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#define DEFAULT_PRNG_KSZ 20
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#define DEFAULT_PRNG_IV "defaultv"
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#define DEFAULT_PRNG_IVSZ 8
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#define DEFAULT_BLK_SZ 16
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#define DEFAULT_V_SEED "zaybxcwdveuftgsh"
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/*
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* Flags for the prng_context flags field
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*/
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#define PRNG_FIXED_SIZE 0x1
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#define PRNG_NEED_RESET 0x2
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/*
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* Note: DT is our counter value
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* I is our intermediate value
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* V is our seed vector
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* See http://csrc.nist.gov/groups/STM/cavp/documents/rng/931rngext.pdf
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* for implementation details
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*/
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struct prng_context {
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char *prng_key;
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char *prng_iv;
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spinlock_t prng_lock;
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unsigned char rand_data[DEFAULT_BLK_SZ];
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unsigned char last_rand_data[DEFAULT_BLK_SZ];
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unsigned char DT[DEFAULT_BLK_SZ];
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unsigned char I[DEFAULT_BLK_SZ];
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unsigned char V[DEFAULT_BLK_SZ];
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u32 rand_data_valid;
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struct crypto_blkcipher *tfm;
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u32 flags;
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};
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static int dbg;
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static void hexdump(char *note, unsigned char *buf, unsigned int len)
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{
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if (dbg) {
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printk(KERN_CRIT "%s", note);
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print_hex_dump(KERN_CONT, "", DUMP_PREFIX_OFFSET,
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16, 1,
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buf, len, false);
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}
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}
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#define dbgprint(format, args...) do {if(dbg) printk(format, ##args);} while(0)
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static void xor_vectors(unsigned char *in1, unsigned char *in2,
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unsigned char *out, unsigned int size)
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{
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int i;
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for (i=0;i<size;i++)
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out[i] = in1[i] ^ in2[i];
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}
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/*
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* Returns DEFAULT_BLK_SZ bytes of random data per call
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* returns 0 if generation succeded, <0 if something went wrong
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*/
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static int _get_more_prng_bytes(struct prng_context *ctx)
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{
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int i;
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struct blkcipher_desc desc;
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struct scatterlist sg_in, sg_out;
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int ret;
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unsigned char tmp[DEFAULT_BLK_SZ];
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desc.tfm = ctx->tfm;
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desc.flags = 0;
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dbgprint(KERN_CRIT "Calling _get_more_prng_bytes for context %p\n",ctx);
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hexdump("Input DT: ", ctx->DT, DEFAULT_BLK_SZ);
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hexdump("Input I: ", ctx->I, DEFAULT_BLK_SZ);
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hexdump("Input V: ", ctx->V, DEFAULT_BLK_SZ);
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/*
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* This algorithm is a 3 stage state machine
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*/
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for (i=0;i<3;i++) {
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desc.tfm = ctx->tfm;
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desc.flags = 0;
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switch (i) {
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case 0:
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/*
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* Start by encrypting the counter value
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* This gives us an intermediate value I
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*/
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memcpy(tmp, ctx->DT, DEFAULT_BLK_SZ);
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sg_init_one(&sg_out, &ctx->I[0], DEFAULT_BLK_SZ);
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hexdump("tmp stage 0: ", tmp, DEFAULT_BLK_SZ);
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break;
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case 1:
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/*
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* Next xor I with our secret vector V
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* encrypt that result to obtain our
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* pseudo random data which we output
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*/
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xor_vectors(ctx->I, ctx->V, tmp, DEFAULT_BLK_SZ);
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sg_init_one(&sg_out, &ctx->rand_data[0], DEFAULT_BLK_SZ);
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hexdump("tmp stage 1: ", tmp, DEFAULT_BLK_SZ);
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break;
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case 2:
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/*
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* First check that we didn't produce the same random data
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* that we did last time around through this
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*/
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if (!memcmp(ctx->rand_data, ctx->last_rand_data, DEFAULT_BLK_SZ)) {
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printk(KERN_ERR "ctx %p Failed repetition check!\n",
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ctx);
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ctx->flags |= PRNG_NEED_RESET;
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return -1;
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}
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memcpy(ctx->last_rand_data, ctx->rand_data, DEFAULT_BLK_SZ);
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/*
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* Lastly xor the random data with I
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* and encrypt that to obtain a new secret vector V
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*/
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xor_vectors(ctx->rand_data, ctx->I, tmp, DEFAULT_BLK_SZ);
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sg_init_one(&sg_out, &ctx->V[0], DEFAULT_BLK_SZ);
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hexdump("tmp stage 2: ", tmp, DEFAULT_BLK_SZ);
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break;
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}
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/* Initialize our input buffer */
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sg_init_one(&sg_in, &tmp[0], DEFAULT_BLK_SZ);
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/* do the encryption */
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ret = crypto_blkcipher_encrypt(&desc, &sg_out, &sg_in, DEFAULT_BLK_SZ);
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/* And check the result */
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if (ret) {
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dbgprint(KERN_CRIT "Encryption of new block failed for context %p\n",ctx);
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ctx->rand_data_valid = DEFAULT_BLK_SZ;
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return -1;
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}
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}
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/*
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* Now update our DT value
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*/
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for (i=DEFAULT_BLK_SZ-1;i>0;i--) {
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ctx->DT[i] = ctx->DT[i-1];
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}
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ctx->DT[0] += 1;
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dbgprint("Returning new block for context %p\n",ctx);
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ctx->rand_data_valid = 0;
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hexdump("Output DT: ", ctx->DT, DEFAULT_BLK_SZ);
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hexdump("Output I: ", ctx->I, DEFAULT_BLK_SZ);
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hexdump("Output V: ", ctx->V, DEFAULT_BLK_SZ);
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hexdump("New Random Data: ", ctx->rand_data, DEFAULT_BLK_SZ);
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return 0;
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}
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/* Our exported functions */
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int get_prng_bytes(char *buf, int nbytes, struct prng_context *ctx)
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{
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unsigned long flags;
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unsigned char *ptr = buf;
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unsigned int byte_count = (unsigned int)nbytes;
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int err;
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if (nbytes < 0)
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return -EINVAL;
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spin_lock_irqsave(&ctx->prng_lock, flags);
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err = -EFAULT;
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if (ctx->flags & PRNG_NEED_RESET)
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goto done;
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/*
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* If the FIXED_SIZE flag is on, only return whole blocks of
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* pseudo random data
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*/
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err = -EINVAL;
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if (ctx->flags & PRNG_FIXED_SIZE) {
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if (nbytes < DEFAULT_BLK_SZ)
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goto done;
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byte_count = DEFAULT_BLK_SZ;
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}
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err = byte_count;
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dbgprint(KERN_CRIT "getting %d random bytes for context %p\n",byte_count, ctx);
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remainder:
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if (ctx->rand_data_valid == DEFAULT_BLK_SZ) {
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if (_get_more_prng_bytes(ctx) < 0) {
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memset(buf, 0, nbytes);
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err = -EFAULT;
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goto done;
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}
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}
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/*
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* Copy up to the next whole block size
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*/
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if (byte_count < DEFAULT_BLK_SZ) {
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for (;ctx->rand_data_valid < DEFAULT_BLK_SZ; ctx->rand_data_valid++) {
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*ptr = ctx->rand_data[ctx->rand_data_valid];
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ptr++;
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byte_count--;
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if (byte_count == 0)
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goto done;
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}
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}
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/*
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* Now copy whole blocks
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*/
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for(;byte_count >= DEFAULT_BLK_SZ; byte_count -= DEFAULT_BLK_SZ) {
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if (_get_more_prng_bytes(ctx) < 0) {
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memset(buf, 0, nbytes);
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err = -1;
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goto done;
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}
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memcpy(ptr, ctx->rand_data, DEFAULT_BLK_SZ);
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ctx->rand_data_valid += DEFAULT_BLK_SZ;
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ptr += DEFAULT_BLK_SZ;
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}
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/*
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* Now copy any extra partial data
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*/
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if (byte_count)
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goto remainder;
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done:
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spin_unlock_irqrestore(&ctx->prng_lock, flags);
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dbgprint(KERN_CRIT "returning %d from get_prng_bytes in context %p\n",err, ctx);
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return err;
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}
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EXPORT_SYMBOL_GPL(get_prng_bytes);
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struct prng_context *alloc_prng_context(void)
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{
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struct prng_context *ctx=kzalloc(sizeof(struct prng_context), GFP_KERNEL);
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spin_lock_init(&ctx->prng_lock);
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if (reset_prng_context(ctx, NULL, NULL, NULL, NULL)) {
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kfree(ctx);
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ctx = NULL;
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}
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dbgprint(KERN_CRIT "returning context %p\n",ctx);
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return ctx;
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}
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EXPORT_SYMBOL_GPL(alloc_prng_context);
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void free_prng_context(struct prng_context *ctx)
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{
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crypto_free_blkcipher(ctx->tfm);
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kfree(ctx);
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}
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EXPORT_SYMBOL_GPL(free_prng_context);
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int reset_prng_context(struct prng_context *ctx,
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unsigned char *key, unsigned char *iv,
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unsigned char *V, unsigned char *DT)
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{
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int ret;
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int iv_len;
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int rc = -EFAULT;
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spin_lock(&ctx->prng_lock);
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ctx->flags |= PRNG_NEED_RESET;
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if (key)
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memcpy(ctx->prng_key,key,strlen(ctx->prng_key));
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else
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ctx->prng_key = DEFAULT_PRNG_KEY;
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if (iv)
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memcpy(ctx->prng_iv,iv, strlen(ctx->prng_iv));
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else
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ctx->prng_iv = DEFAULT_PRNG_IV;
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if (V)
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memcpy(ctx->V,V,DEFAULT_BLK_SZ);
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else
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memcpy(ctx->V,DEFAULT_V_SEED,DEFAULT_BLK_SZ);
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if (DT)
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memcpy(ctx->DT, DT, DEFAULT_BLK_SZ);
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else
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memset(ctx->DT, 0, DEFAULT_BLK_SZ);
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memset(ctx->rand_data,0,DEFAULT_BLK_SZ);
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memset(ctx->last_rand_data,0,DEFAULT_BLK_SZ);
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if (ctx->tfm)
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crypto_free_blkcipher(ctx->tfm);
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ctx->tfm = crypto_alloc_blkcipher("rfc3686(ctr(aes))",0,0);
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if (!ctx->tfm) {
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dbgprint(KERN_CRIT "Failed to alloc crypto tfm for context %p\n",ctx->tfm);
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goto out;
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}
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ctx->rand_data_valid = DEFAULT_BLK_SZ;
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ret = crypto_blkcipher_setkey(ctx->tfm, ctx->prng_key, strlen(ctx->prng_key));
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if (ret) {
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dbgprint(KERN_CRIT "PRNG: setkey() failed flags=%x\n",
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crypto_blkcipher_get_flags(ctx->tfm));
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crypto_free_blkcipher(ctx->tfm);
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goto out;
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}
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iv_len = crypto_blkcipher_ivsize(ctx->tfm);
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if (iv_len) {
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crypto_blkcipher_set_iv(ctx->tfm, ctx->prng_iv, iv_len);
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}
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rc = 0;
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ctx->flags &= ~PRNG_NEED_RESET;
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out:
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spin_unlock(&ctx->prng_lock);
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return rc;
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}
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EXPORT_SYMBOL_GPL(reset_prng_context);
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/* Module initalization */
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static int __init prng_mod_init(void)
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{
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#ifdef TEST_PRNG_ON_START
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int i;
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unsigned char tmpbuf[DEFAULT_BLK_SZ];
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struct prng_context *ctx = alloc_prng_context();
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if (ctx == NULL)
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return -EFAULT;
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for (i=0;i<16;i++) {
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if (get_prng_bytes(tmpbuf, DEFAULT_BLK_SZ, ctx) < 0) {
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free_prng_context(ctx);
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return -EFAULT;
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}
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}
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free_prng_context(ctx);
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#endif
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return 0;
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}
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static void __exit prng_mod_fini(void)
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{
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return;
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}
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION("Software Pseudo Random Number Generator");
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MODULE_AUTHOR("Neil Horman <nhorman@tuxdriver.com>");
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module_param(dbg, int, 0);
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MODULE_PARM_DESC(dbg, "Boolean to enable debugging (0/1 == off/on)");
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module_init(prng_mod_init);
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module_exit(prng_mod_fini);
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27
crypto/prng.h
Normal file
27
crypto/prng.h
Normal file
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@ -0,0 +1,27 @@
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/*
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* PRNG: Pseudo Random Number Generator
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*
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* (C) Neil Horman <nhorman@tuxdriver.com>
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2 of the License, or (at your
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* any later version.
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*
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*
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*/
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#ifndef _PRNG_H_
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#define _PRNG_H_
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struct prng_context;
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int get_prng_bytes(char *buf, int nbytes, struct prng_context *ctx);
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struct prng_context *alloc_prng_context(void);
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int reset_prng_context(struct prng_context *ctx,
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unsigned char *key, unsigned char *iv,
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unsigned char *V,
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unsigned char *DT);
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void free_prng_context(struct prng_context *ctx);
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#endif
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