diff options
Diffstat (limited to 'crypto/prng.c')
| -rw-r--r-- | crypto/prng.c | 410 |
1 files changed, 410 insertions, 0 deletions
diff --git a/crypto/prng.c b/crypto/prng.c new file mode 100644 index 00000000000..24e4f3282c5 --- /dev/null +++ b/crypto/prng.c @@ -0,0 +1,410 @@ +/* + * 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); |