| /* |
| * 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> |
| |
| #include "internal.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; |
| } |
| |
| 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, 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, |
| unsigned char *key, size_t klen, |
| unsigned char *V, unsigned char *DT) |
| { |
| int ret; |
| 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, 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, u8 *seed, unsigned int slen) |
| { |
| struct prng_context *prng = crypto_rng_ctx(tfm); |
| u8 *key = seed + DEFAULT_BLK_SZ; |
| 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; |
| } |
| |
| static struct crypto_alg rng_alg = { |
| .cra_name = "stdrng", |
| .cra_driver_name = "ansi_cprng", |
| .cra_priority = 100, |
| .cra_flags = CRYPTO_ALG_TYPE_RNG, |
| .cra_ctxsize = sizeof(struct prng_context), |
| .cra_type = &crypto_rng_type, |
| .cra_module = THIS_MODULE, |
| .cra_list = LIST_HEAD_INIT(rng_alg.cra_list), |
| .cra_init = cprng_init, |
| .cra_exit = cprng_exit, |
| .cra_u = { |
| .rng = { |
| .rng_make_random = cprng_get_random, |
| .rng_reset = cprng_reset, |
| .seedsize = DEFAULT_PRNG_KSZ + 2*DEFAULT_BLK_SZ, |
| } |
| } |
| }; |
| |
| #ifdef CONFIG_CRYPTO_FIPS |
| static int fips_cprng_get_random(struct crypto_rng *tfm, 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, u8 *seed, unsigned int slen) |
| { |
| u8 rdata[DEFAULT_BLK_SZ]; |
| int rc; |
| |
| struct prng_context *prng = crypto_rng_ctx(tfm); |
| |
| 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; |
| } |
| |
| static struct crypto_alg fips_rng_alg = { |
| .cra_name = "fips(ansi_cprng)", |
| .cra_driver_name = "fips_ansi_cprng", |
| .cra_priority = 300, |
| .cra_flags = CRYPTO_ALG_TYPE_RNG, |
| .cra_ctxsize = sizeof(struct prng_context), |
| .cra_type = &crypto_rng_type, |
| .cra_module = THIS_MODULE, |
| .cra_list = LIST_HEAD_INIT(rng_alg.cra_list), |
| .cra_init = cprng_init, |
| .cra_exit = cprng_exit, |
| .cra_u = { |
| .rng = { |
| .rng_make_random = fips_cprng_get_random, |
| .rng_reset = fips_cprng_reset, |
| .seedsize = DEFAULT_PRNG_KSZ + 2*DEFAULT_BLK_SZ, |
| } |
| } |
| }; |
| #endif |
| |
| /* Module initalization */ |
| static int __init prng_mod_init(void) |
| { |
| int rc = 0; |
| |
| rc = crypto_register_alg(&rng_alg); |
| #ifdef CONFIG_CRYPTO_FIPS |
| if (rc) |
| goto out; |
| |
| rc = crypto_register_alg(&fips_rng_alg); |
| |
| out: |
| #endif |
| return rc; |
| } |
| |
| static void __exit prng_mod_fini(void) |
| { |
| crypto_unregister_alg(&rng_alg); |
| #ifdef CONFIG_CRYPTO_FIPS |
| crypto_unregister_alg(&fips_rng_alg); |
| #endif |
| 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); |
| MODULE_ALIAS_CRYPTO("stdrng"); |
| MODULE_ALIAS_CRYPTO("ansi_cprng"); |