diff options
Diffstat (limited to 'crypto/ansi_cprng.c')
| -rw-r--r-- | crypto/ansi_cprng.c | 472 |
1 files changed, 472 insertions, 0 deletions
diff --git a/crypto/ansi_cprng.c b/crypto/ansi_cprng.c new file mode 100644 index 000000000..c475c1129 --- /dev/null +++ b/crypto/ansi_cprng.c @@ -0,0 +1,472 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * 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> + */ + +#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)"); +subsys_initcall(prng_mod_init); +module_exit(prng_mod_fini); +MODULE_ALIAS_CRYPTO("stdrng"); +MODULE_ALIAS_CRYPTO("ansi_cprng"); |