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- /*
- * PRNG: Pseudo Random Number Generator
- * Based on NIST Recommended PRNG From ANSI X9.31 Appendix A.2.4 using
- * AES 128 cipher
- *
- * (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 <crypto/internal/rng.h>
- #include <linux/err.h>
- #include <linux/init.h>
- #include <linux/module.h>
- #include <linux/moduleparam.h>
- #include <linux/string.h>
- #define DEFAULT_PRNG_KEY "0123456789abcdef"
- #define DEFAULT_PRNG_KSZ 16
- #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 {
- 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_cipher *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 succeeded, <0 if something went wrong
- */
- static int _get_more_prng_bytes(struct prng_context *ctx, int cont_test)
- {
- int i;
- unsigned char tmp[DEFAULT_BLK_SZ];
- unsigned char *output = NULL;
- 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++) {
- switch (i) {
- case 0:
- /*
- * Start by encrypting the counter value
- * This gives us an intermediate value I
- */
- memcpy(tmp, ctx->DT, DEFAULT_BLK_SZ);
- output = ctx->I;
- 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);
- hexdump("tmp stage 1: ", tmp, DEFAULT_BLK_SZ);
- output = ctx->rand_data;
- 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)) {
- if (cont_test) {
- panic("cprng %p Failed repetition check!\n",
- ctx);
- }
- printk(KERN_ERR
- "ctx %p Failed repetition check!\n",
- ctx);
- ctx->flags |= PRNG_NEED_RESET;
- return -EINVAL;
- }
- 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);
- output = ctx->V;
- hexdump("tmp stage 2: ", tmp, DEFAULT_BLK_SZ);
- break;
- }
- /* do the encryption */
- crypto_cipher_encrypt_one(ctx->tfm, output, tmp);
- }
- /*
- * Now update our DT value
- */
- for (i = DEFAULT_BLK_SZ - 1; i >= 0; i--) {
- ctx->DT[i] += 1;
- if (ctx->DT[i] != 0)
- break;
- }
- 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 */
- static int get_prng_bytes(char *buf, size_t nbytes, struct prng_context *ctx,
- int do_cont_test)
- {
- unsigned char *ptr = buf;
- unsigned int byte_count = (unsigned int)nbytes;
- int err;
- spin_lock_bh(&ctx->prng_lock);
- err = -EINVAL;
- 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;
- }
- /*
- * Return 0 in case of success as mandated by the kernel
- * crypto API interface definition.
- */
- err = 0;
- 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, do_cont_test) < 0) {
- memset(buf, 0, nbytes);
- err = -EINVAL;
- goto done;
- }
- }
- /*
- * Copy any data less than an entire block
- */
- if (byte_count < DEFAULT_BLK_SZ) {
- empty_rbuf:
- while (ctx->rand_data_valid < DEFAULT_BLK_SZ) {
- *ptr = ctx->rand_data[ctx->rand_data_valid];
- ptr++;
- byte_count--;
- ctx->rand_data_valid++;
- if (byte_count == 0)
- goto done;
- }
- }
- /*
- * Now copy whole blocks
- */
- for (; byte_count >= DEFAULT_BLK_SZ; byte_count -= DEFAULT_BLK_SZ) {
- if (ctx->rand_data_valid == DEFAULT_BLK_SZ) {
- if (_get_more_prng_bytes(ctx, do_cont_test) < 0) {
- memset(buf, 0, nbytes);
- err = -EINVAL;
- goto done;
- }
- }
- if (ctx->rand_data_valid > 0)
- goto empty_rbuf;
- memcpy(ptr, ctx->rand_data, DEFAULT_BLK_SZ);
- ctx->rand_data_valid += DEFAULT_BLK_SZ;
- ptr += DEFAULT_BLK_SZ;
- }
- /*
- * Now go back and get any remaining partial block
- */
- if (byte_count)
- goto remainder;
- done:
- spin_unlock_bh(&ctx->prng_lock);
- dbgprint(KERN_CRIT "returning %d from get_prng_bytes in context %p\n",
- err, ctx);
- return err;
- }
- static void free_prng_context(struct prng_context *ctx)
- {
- crypto_free_cipher(ctx->tfm);
- }
- static int reset_prng_context(struct prng_context *ctx,
- const unsigned char *key, size_t klen,
- const unsigned char *V, const unsigned char *DT)
- {
- int ret;
- const unsigned char *prng_key;
- spin_lock_bh(&ctx->prng_lock);
- ctx->flags |= PRNG_NEED_RESET;
- prng_key = (key != NULL) ? key : (unsigned char *)DEFAULT_PRNG_KEY;
- if (!key)
- klen = DEFAULT_PRNG_KSZ;
- 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);
- ctx->rand_data_valid = DEFAULT_BLK_SZ;
- ret = crypto_cipher_setkey(ctx->tfm, prng_key, klen);
- if (ret) {
- dbgprint(KERN_CRIT "PRNG: setkey() failed flags=%x\n",
- crypto_cipher_get_flags(ctx->tfm));
- goto out;
- }
- ret = 0;
- ctx->flags &= ~PRNG_NEED_RESET;
- out:
- spin_unlock_bh(&ctx->prng_lock);
- return ret;
- }
- static int cprng_init(struct crypto_tfm *tfm)
- {
- struct prng_context *ctx = crypto_tfm_ctx(tfm);
- spin_lock_init(&ctx->prng_lock);
- ctx->tfm = crypto_alloc_cipher("aes", 0, 0);
- if (IS_ERR(ctx->tfm)) {
- dbgprint(KERN_CRIT "Failed to alloc tfm for context %p\n",
- ctx);
- return PTR_ERR(ctx->tfm);
- }
- if (reset_prng_context(ctx, NULL, DEFAULT_PRNG_KSZ, NULL, NULL) < 0)
- return -EINVAL;
- /*
- * after allocation, we should always force the user to reset
- * so they don't inadvertently use the insecure default values
- * without specifying them intentially
- */
- ctx->flags |= PRNG_NEED_RESET;
- return 0;
- }
- static void cprng_exit(struct crypto_tfm *tfm)
- {
- free_prng_context(crypto_tfm_ctx(tfm));
- }
- static int cprng_get_random(struct crypto_rng *tfm,
- const u8 *src, unsigned int slen,
- u8 *rdata, unsigned int dlen)
- {
- struct prng_context *prng = crypto_rng_ctx(tfm);
- return get_prng_bytes(rdata, dlen, prng, 0);
- }
- /*
- * This is the cprng_registered reset method the seed value is
- * interpreted as the tuple { V KEY DT}
- * V and KEY are required during reset, and DT is optional, detected
- * as being present by testing the length of the seed
- */
- static int cprng_reset(struct crypto_rng *tfm,
- const u8 *seed, unsigned int slen)
- {
- struct prng_context *prng = crypto_rng_ctx(tfm);
- const u8 *key = seed + DEFAULT_BLK_SZ;
- const u8 *dt = NULL;
- if (slen < DEFAULT_PRNG_KSZ + DEFAULT_BLK_SZ)
- return -EINVAL;
- if (slen >= (2 * DEFAULT_BLK_SZ + DEFAULT_PRNG_KSZ))
- dt = key + DEFAULT_PRNG_KSZ;
- reset_prng_context(prng, key, DEFAULT_PRNG_KSZ, seed, dt);
- if (prng->flags & PRNG_NEED_RESET)
- return -EINVAL;
- return 0;
- }
- #ifdef CONFIG_CRYPTO_FIPS
- static int fips_cprng_get_random(struct crypto_rng *tfm,
- const u8 *src, unsigned int slen,
- u8 *rdata, unsigned int dlen)
- {
- struct prng_context *prng = crypto_rng_ctx(tfm);
- return get_prng_bytes(rdata, dlen, prng, 1);
- }
- static int fips_cprng_reset(struct crypto_rng *tfm,
- const u8 *seed, unsigned int slen)
- {
- u8 rdata[DEFAULT_BLK_SZ];
- const u8 *key = seed + DEFAULT_BLK_SZ;
- int rc;
- struct prng_context *prng = crypto_rng_ctx(tfm);
- if (slen < DEFAULT_PRNG_KSZ + DEFAULT_BLK_SZ)
- return -EINVAL;
- /* fips strictly requires seed != key */
- if (!memcmp(seed, key, DEFAULT_PRNG_KSZ))
- return -EINVAL;
- rc = cprng_reset(tfm, seed, slen);
- if (!rc)
- goto out;
- /* this primes our continuity test */
- rc = get_prng_bytes(rdata, DEFAULT_BLK_SZ, prng, 0);
- prng->rand_data_valid = DEFAULT_BLK_SZ;
- out:
- return rc;
- }
- #endif
- static struct rng_alg rng_algs[] = { {
- .generate = cprng_get_random,
- .seed = cprng_reset,
- .seedsize = DEFAULT_PRNG_KSZ + 2 * DEFAULT_BLK_SZ,
- .base = {
- .cra_name = "stdrng",
- .cra_driver_name = "ansi_cprng",
- .cra_priority = 100,
- .cra_ctxsize = sizeof(struct prng_context),
- .cra_module = THIS_MODULE,
- .cra_init = cprng_init,
- .cra_exit = cprng_exit,
- }
- #ifdef CONFIG_CRYPTO_FIPS
- }, {
- .generate = fips_cprng_get_random,
- .seed = fips_cprng_reset,
- .seedsize = DEFAULT_PRNG_KSZ + 2 * DEFAULT_BLK_SZ,
- .base = {
- .cra_name = "fips(ansi_cprng)",
- .cra_driver_name = "fips_ansi_cprng",
- .cra_priority = 300,
- .cra_ctxsize = sizeof(struct prng_context),
- .cra_module = THIS_MODULE,
- .cra_init = cprng_init,
- .cra_exit = cprng_exit,
- }
- #endif
- } };
- /* Module initalization */
- static int __init prng_mod_init(void)
- {
- return crypto_register_rngs(rng_algs, ARRAY_SIZE(rng_algs));
- }
- static void __exit prng_mod_fini(void)
- {
- crypto_unregister_rngs(rng_algs, ARRAY_SIZE(rng_algs));
- }
- 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);
- MODULE_ALIAS_CRYPTO("stdrng");
- MODULE_ALIAS_CRYPTO("ansi_cprng");
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