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17f0f4a47d
This patch adds a random number generator interface as well as a cryptographic pseudo-random number generator based on AES. 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>
418 lines
9.0 KiB
C
418 lines
9.0 KiB
C
/*
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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
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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 <crypto/internal/rng.h>
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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/moduleparam.h>
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#include <linux/string.h>
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#include "internal.h"
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#define DEFAULT_PRNG_KEY "0123456789abcdef"
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#define DEFAULT_PRNG_KSZ 16
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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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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_cipher *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 {\
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if (dbg)\
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printk(format, ##args);\
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} 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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unsigned char tmp[DEFAULT_BLK_SZ];
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unsigned char *output = NULL;
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dbgprint(KERN_CRIT "Calling _get_more_prng_bytes for context %p\n",
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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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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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output = ctx->I;
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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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hexdump("tmp stage 1: ", tmp, DEFAULT_BLK_SZ);
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output = ctx->rand_data;
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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
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* random data 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,
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DEFAULT_BLK_SZ)) {
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printk(KERN_ERR
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"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 -EINVAL;
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}
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memcpy(ctx->last_rand_data, ctx->rand_data,
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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,
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DEFAULT_BLK_SZ);
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output = ctx->V;
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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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/* do the encryption */
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crypto_cipher_encrypt_one(ctx->tfm, output, tmp);
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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 = 0; i < DEFAULT_BLK_SZ; i++) {
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ctx->DT[i] += 1;
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if (ctx->DT[i] != 0)
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break;
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}
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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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static int get_prng_bytes(char *buf, size_t 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 = -EINVAL;
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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",
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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 = -EINVAL;
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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;
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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 = -EINVAL;
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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",
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err, ctx);
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return err;
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}
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static void free_prng_context(struct prng_context *ctx)
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{
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crypto_free_cipher(ctx->tfm);
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}
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static int reset_prng_context(struct prng_context *ctx,
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unsigned char *key, size_t klen,
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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 rc = -EINVAL;
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unsigned char *prng_key;
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spin_lock(&ctx->prng_lock);
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ctx->flags |= PRNG_NEED_RESET;
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prng_key = (key != NULL) ? key : (unsigned char *)DEFAULT_PRNG_KEY;
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if (!key)
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klen = DEFAULT_PRNG_KSZ;
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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_cipher(ctx->tfm);
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ctx->tfm = crypto_alloc_cipher("aes", 0, 0);
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if (IS_ERR(ctx->tfm)) {
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dbgprint(KERN_CRIT "Failed to alloc tfm for context %p\n",
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ctx);
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ctx->tfm = NULL;
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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_cipher_setkey(ctx->tfm, prng_key, klen);
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if (ret) {
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dbgprint(KERN_CRIT "PRNG: setkey() failed flags=%x\n",
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crypto_cipher_get_flags(ctx->tfm));
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crypto_free_cipher(ctx->tfm);
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goto out;
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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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static int cprng_init(struct crypto_tfm *tfm)
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{
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struct prng_context *ctx = crypto_tfm_ctx(tfm);
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spin_lock_init(&ctx->prng_lock);
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return reset_prng_context(ctx, NULL, DEFAULT_PRNG_KSZ, NULL, NULL);
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}
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static void cprng_exit(struct crypto_tfm *tfm)
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{
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free_prng_context(crypto_tfm_ctx(tfm));
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}
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static int cprng_get_random(struct crypto_rng *tfm, u8 *rdata,
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unsigned int dlen)
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{
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struct prng_context *prng = crypto_rng_ctx(tfm);
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return get_prng_bytes(rdata, dlen, prng);
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}
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static int cprng_reset(struct crypto_rng *tfm, u8 *seed, unsigned int slen)
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{
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struct prng_context *prng = crypto_rng_ctx(tfm);
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u8 *key = seed + DEFAULT_PRNG_KSZ;
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if (slen < DEFAULT_PRNG_KSZ + DEFAULT_BLK_SZ)
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return -EINVAL;
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reset_prng_context(prng, key, DEFAULT_PRNG_KSZ, seed, NULL);
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if (prng->flags & PRNG_NEED_RESET)
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return -EINVAL;
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return 0;
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}
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static struct crypto_alg rng_alg = {
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.cra_name = "stdrng",
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.cra_driver_name = "ansi_cprng",
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.cra_priority = 100,
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.cra_flags = CRYPTO_ALG_TYPE_RNG,
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.cra_ctxsize = sizeof(struct prng_context),
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.cra_type = &crypto_rng_type,
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.cra_module = THIS_MODULE,
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.cra_list = LIST_HEAD_INIT(rng_alg.cra_list),
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.cra_init = cprng_init,
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.cra_exit = cprng_exit,
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.cra_u = {
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.rng = {
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.rng_make_random = cprng_get_random,
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.rng_reset = cprng_reset,
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.seedsize = DEFAULT_PRNG_KSZ + DEFAULT_BLK_SZ,
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}
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}
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};
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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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int ret = 0;
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if (fips_enabled)
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rng_alg.cra_priority += 200;
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ret = crypto_register_alg(&rng_alg);
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if (ret)
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goto out;
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out:
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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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crypto_unregister_alg(&rng_alg);
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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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MODULE_ALIAS("stdrng");
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