[PATCH 5.10 3/3] crypto: crypto4xx - Remove insecure and unused rng_alg

[Eric Biggers <ebiggers@kernel.org>]

commit 7811ec9e973d2c9e465083699f0c8240b98cb8c4 upstream.

Remove crypto4xx_rng, as it is insecure and unused:

- It has only a 64-bit security strength, which is highly inadequate.
  This can be seen by the fact that crypto4xx_hw_init() seeds it with
  only 64 bits of entropy, and the fact that the original commit
  mentions that it implements ANSI X9.17 Annex C.

  Another issue was that this driver didn't implement the crypto_rng API
  correctly, as crypto4xx_prng_generate() didn't return 0 on success.

- No user of this code is known.  It's usable only theoretically via the
  "rng" algorithm type of AF_ALG.  But userspace actually just uses the
  actual Linux RNG (/dev/random etc) instead.  And rng_algs don't
  contribute entropy to the actual Linux RNG either.  (This may have
  been confused with hwrng, which does contribute entropy.)

Fixes: d072bfa48853 ("crypto: crypto4xx - add prng crypto support")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Acked-by: Christian Lamparter <chunkeey@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
---
 drivers/crypto/amcc/crypto4xx_core.c    | 87 -------------------------
 drivers/crypto/amcc/crypto4xx_core.h    |  4 --
 drivers/crypto/amcc/crypto4xx_reg_def.h | 11 ----
 3 files changed, 102 deletions(-)

diff --git a/drivers/crypto/amcc/crypto4xx_core.c b/drivers/crypto/amcc/crypto4xx_core.c
index b0841b3504a5..d370e707dbdd 100644
--- a/drivers/crypto/amcc/crypto4xx_core.c
+++ b/drivers/crypto/amcc/crypto4xx_core.c
@@ -31,11 +31,9 @@
 #include <crypto/ctr.h>
 #include <crypto/gcm.h>
 #include <crypto/sha.h>
-#include <crypto/rng.h>
 #include <crypto/scatterwalk.h>
 #include <crypto/skcipher.h>
 #include <crypto/internal/aead.h>
-#include <crypto/internal/rng.h>
 #include <crypto/internal/skcipher.h>
 #include "crypto4xx_reg_def.h"
 #include "crypto4xx_core.h"
@@ -989,10 +987,6 @@ static int crypto4xx_register_alg(struct crypto4xx_device *sec_dev,
 			rc = crypto_register_aead(&alg->alg.u.aead);
 			break;
 
-		case CRYPTO_ALG_TYPE_RNG:
-			rc = crypto_register_rng(&alg->alg.u.rng);
-			break;
-
 		default:
 			rc = crypto_register_skcipher(&alg->alg.u.cipher);
 			break;
@@ -1018,10 +1012,6 @@ static void crypto4xx_unregister_alg(struct crypto4xx_device *sec_dev)
 			crypto_unregister_aead(&alg->alg.u.aead);
 			break;
 
-		case CRYPTO_ALG_TYPE_RNG:
-			crypto_unregister_rng(&alg->alg.u.rng);
-			break;
-
 		default:
 			crypto_unregister_skcipher(&alg->alg.u.cipher);
 		}
@@ -1080,69 +1070,6 @@ static irqreturn_t crypto4xx_ce_interrupt_handler_revb(int irq, void *data)
 		PPC4XX_TMO_ERR_INT);
 }
 
-static int ppc4xx_prng_data_read(struct crypto4xx_device *dev,
-				 u8 *data, unsigned int max)
-{
-	unsigned int i, curr = 0;
-	u32 val[2];
-
-	do {
-		/* trigger PRN generation */
-		writel(PPC4XX_PRNG_CTRL_AUTO_EN,
-		       dev->ce_base + CRYPTO4XX_PRNG_CTRL);
-
-		for (i = 0; i < 1024; i++) {
-			/* usually 19 iterations are enough */
-			if ((readl(dev->ce_base + CRYPTO4XX_PRNG_STAT) &
-			     CRYPTO4XX_PRNG_STAT_BUSY))
-				continue;
-
-			val[0] = readl_be(dev->ce_base + CRYPTO4XX_PRNG_RES_0);
-			val[1] = readl_be(dev->ce_base + CRYPTO4XX_PRNG_RES_1);
-			break;
-		}
-		if (i == 1024)
-			return -ETIMEDOUT;
-
-		if ((max - curr) >= 8) {
-			memcpy(data, &val, 8);
-			data += 8;
-			curr += 8;
-		} else {
-			/* copy only remaining bytes */
-			memcpy(data, &val, max - curr);
-			break;
-		}
-	} while (curr < max);
-
-	return curr;
-}
-
-static int crypto4xx_prng_generate(struct crypto_rng *tfm,
-				   const u8 *src, unsigned int slen,
-				   u8 *dstn, unsigned int dlen)
-{
-	struct rng_alg *alg = crypto_rng_alg(tfm);
-	struct crypto4xx_alg *amcc_alg;
-	struct crypto4xx_device *dev;
-	int ret;
-
-	amcc_alg = container_of(alg, struct crypto4xx_alg, alg.u.rng);
-	dev = amcc_alg->dev;
-
-	mutex_lock(&dev->core_dev->rng_lock);
-	ret = ppc4xx_prng_data_read(dev, dstn, dlen);
-	mutex_unlock(&dev->core_dev->rng_lock);
-	return ret;
-}
-
-
-static int crypto4xx_prng_seed(struct crypto_rng *tfm, const u8 *seed,
-			unsigned int slen)
-{
-	return 0;
-}
-
 /*
  * Supported Crypto Algorithms
  */
@@ -1312,18 +1239,6 @@ static struct crypto4xx_alg_common crypto4xx_alg[] = {
 			.cra_module	= THIS_MODULE,
 		},
 	} },
-	{ .type = CRYPTO_ALG_TYPE_RNG, .u.rng = {
-		.base = {
-			.cra_name		= "stdrng",
-			.cra_driver_name        = "crypto4xx_rng",
-			.cra_priority		= 300,
-			.cra_ctxsize		= 0,
-			.cra_module		= THIS_MODULE,
-		},
-		.generate               = crypto4xx_prng_generate,
-		.seed                   = crypto4xx_prng_seed,
-		.seedsize               = 0,
-	} },
 };
 
 /*
@@ -1393,7 +1308,6 @@ static int crypto4xx_probe(struct platform_device *ofdev)
 	core_dev->dev->core_dev = core_dev;
 	core_dev->dev->is_revb = is_revb;
 	core_dev->device = dev;
-	mutex_init(&core_dev->rng_lock);
 	spin_lock_init(&core_dev->lock);
 	INIT_LIST_HEAD(&core_dev->dev->alg_list);
 	ratelimit_default_init(&core_dev->dev->aead_ratelimit);
@@ -1471,7 +1385,6 @@ static int crypto4xx_remove(struct platform_device *ofdev)
 	tasklet_kill(&core_dev->tasklet);
 	/* Un-register with Linux CryptoAPI */
 	crypto4xx_unregister_alg(core_dev->dev);
-	mutex_destroy(&core_dev->rng_lock);
 	/* Free all allocated memory */
 	crypto4xx_stop_all(core_dev);
 
diff --git a/drivers/crypto/amcc/crypto4xx_core.h b/drivers/crypto/amcc/crypto4xx_core.h
index 0d83cde84cca..d8224bbe89ca 100644
--- a/drivers/crypto/amcc/crypto4xx_core.h
+++ b/drivers/crypto/amcc/crypto4xx_core.h
@@ -14,10 +14,8 @@
 #define __CRYPTO4XX_CORE_H__
 
 #include <linux/ratelimit.h>
-#include <linux/mutex.h>
 #include <linux/scatterlist.h>
 #include <crypto/internal/aead.h>
-#include <crypto/internal/rng.h>
 #include <crypto/internal/skcipher.h>
 #include "crypto4xx_reg_def.h"
 #include "crypto4xx_sa.h"
@@ -111,7 +109,6 @@ struct crypto4xx_core_device {
 	u32 irq;
 	struct tasklet_struct tasklet;
 	spinlock_t lock;
-	struct mutex rng_lock;
 };
 
 struct crypto4xx_ctx {
@@ -135,7 +132,6 @@ struct crypto4xx_alg_common {
 	union {
 		struct skcipher_alg cipher;
 		struct aead_alg aead;
-		struct rng_alg rng;
 	} u;
 };
 
diff --git a/drivers/crypto/amcc/crypto4xx_reg_def.h b/drivers/crypto/amcc/crypto4xx_reg_def.h
index 1038061224da..73d626308a84 100644
--- a/drivers/crypto/amcc/crypto4xx_reg_def.h
+++ b/drivers/crypto/amcc/crypto4xx_reg_def.h
@@ -90,20 +90,9 @@
 #define CRYPTO4XX_BYTE_ORDER_CFG 		0x000600d8
 #define CRYPTO4XX_ENDIAN_CFG			0x000600d8
 
-#define CRYPTO4XX_PRNG_STAT			0x00070000
-#define CRYPTO4XX_PRNG_STAT_BUSY		0x1
 #define CRYPTO4XX_PRNG_CTRL			0x00070004
 #define CRYPTO4XX_PRNG_SEED_L			0x00070008
 #define CRYPTO4XX_PRNG_SEED_H			0x0007000c
-
-#define CRYPTO4XX_PRNG_RES_0			0x00070020
-#define CRYPTO4XX_PRNG_RES_1			0x00070024
-#define CRYPTO4XX_PRNG_RES_2			0x00070028
-#define CRYPTO4XX_PRNG_RES_3			0x0007002C
-
-#define CRYPTO4XX_PRNG_LFSR_L			0x00070030
-#define CRYPTO4XX_PRNG_LFSR_H			0x00070034
-
 /*
  * Initialize CRYPTO ENGINE registers, and memory bases.
  */
-- 
2.55.0