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32 results

processor.h

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  • ansi_cprng.c 10.92 KiB
    /*
     * 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");