[PATCH 2/2] crypto/crc32c: Provide crc32c-base alias to enable fuzz testing

[Ard Biesheuvel <ardb+git@google.com>]

From: Ard Biesheuvel <ardb@kernel.org>

crc32-generic is backed by the architecture's CRC-32c library, which may
offer a variety of implementations depending on the capabilities of the
platform. These are not covered by the crypto subsystem's fuzz testing
capabilities because crc32c-generic is the reference driver that the
fuzzing logic uses as a source of truth.

Fix this by proving a crc32c-base implementation which is always based
on the generic C implementation, and wire it up as the reference
implementation for the fuzz tester.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 crypto/crc32c_generic.c | 72 ++++++++++++++------
 crypto/testmgr.c        |  1 +
 2 files changed, 51 insertions(+), 22 deletions(-)

diff --git a/crypto/crc32c_generic.c b/crypto/crc32c_generic.c
index a8c90b3f4c6c..0a7543dbc515 100644
--- a/crypto/crc32c_generic.c
+++ b/crypto/crc32c_generic.c
@@ -80,6 +80,17 @@ static int chksum_setkey(struct crypto_shash *tfm, const u8 *key,
 	return 0;
 }
 
+#ifdef CONFIG_CRYPTO_MANAGER_EXTRA_TESTS
+static int chksum_update_base(struct shash_desc *desc, const u8 *data,
+			      unsigned int length)
+{
+	struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);
+
+	ctx->crc = __crc32c_le_base(ctx->crc, data, length);
+	return 0;
+}
+#endif
+
 static int chksum_update(struct shash_desc *desc, const u8 *data,
 			 unsigned int length)
 {
@@ -127,35 +138,52 @@ static int crc32c_cra_init(struct crypto_tfm *tfm)
 	return 0;
 }
 
-static struct shash_alg alg = {
-	.digestsize		=	CHKSUM_DIGEST_SIZE,
-	.setkey			=	chksum_setkey,
-	.init		=	chksum_init,
-	.update		=	chksum_update,
-	.final		=	chksum_final,
-	.finup		=	chksum_finup,
-	.digest		=	chksum_digest,
-	.descsize		=	sizeof(struct chksum_desc_ctx),
-	.base			=	{
-		.cra_name		=	"crc32c",
-		.cra_driver_name	=	"crc32c-generic",
-		.cra_priority		=	100,
-		.cra_flags		=	CRYPTO_ALG_OPTIONAL_KEY,
-		.cra_blocksize		=	CHKSUM_BLOCK_SIZE,
-		.cra_ctxsize		=	sizeof(struct chksum_ctx),
-		.cra_module		=	THIS_MODULE,
-		.cra_init		=	crc32c_cra_init,
-	}
-};
+static struct shash_alg algs[] = {{
+	.digestsize		= CHKSUM_DIGEST_SIZE,
+	.setkey			= chksum_setkey,
+	.init			= chksum_init,
+	.update			= chksum_update,
+	.final			= chksum_final,
+	.finup			= chksum_finup,
+	.digest			= chksum_digest,
+	.descsize		= sizeof(struct chksum_desc_ctx),
+
+	.base.cra_name		= "crc32c",
+	.base.cra_driver_name	= "crc32c-generic",
+	.base.cra_priority	= 100,
+	.base.cra_flags		= CRYPTO_ALG_OPTIONAL_KEY,
+	.base.cra_blocksize	= CHKSUM_BLOCK_SIZE,
+	.base.cra_ctxsize	= sizeof(struct chksum_ctx),
+	.base.cra_module	= THIS_MODULE,
+	.base.cra_init		= crc32c_cra_init,
+#ifdef CONFIG_CRYPTO_MANAGER_EXTRA_TESTS
+}, {
+	.digestsize		= CHKSUM_DIGEST_SIZE,
+	.setkey			= chksum_setkey,
+	.init			= chksum_init,
+	.update			= chksum_update_base,
+	.final			= chksum_final,
+	.digest			= chksum_digest,
+	.descsize		= sizeof(struct chksum_desc_ctx),
+
+	.base.cra_name		= "crc32c",
+	.base.cra_driver_name	= "crc32c-base",
+	.base.cra_flags		= CRYPTO_ALG_OPTIONAL_KEY,
+	.base.cra_blocksize	= CHKSUM_BLOCK_SIZE,
+	.base.cra_ctxsize	= sizeof(struct chksum_ctx),
+	.base.cra_module	= THIS_MODULE,
+	.base.cra_init		= crc32c_cra_init,
+#endif
+}};
 
 static int __init crc32c_mod_init(void)
 {
-	return crypto_register_shash(&alg);
+	return crypto_register_shashes(algs, ARRAY_SIZE(algs));
 }
 
 static void __exit crc32c_mod_fini(void)
 {
-	crypto_unregister_shash(&alg);
+	crypto_unregister_shashes(algs, ARRAY_SIZE(algs));
 }
 
 subsys_initcall(crc32c_mod_init);
diff --git a/crypto/testmgr.c b/crypto/testmgr.c
index e0d6bfcc13e6..c3f1cfe9e17e 100644
--- a/crypto/testmgr.c
+++ b/crypto/testmgr.c
@@ -4700,6 +4700,7 @@ static const struct alg_test_desc alg_test_descs[] = {
 		}
 	}, {
 		.alg = "crc32c",
+		.generic_driver = "crc32c-base",
 		.test = alg_test_crc32c,
 		.fips_allowed = 1,
 		.suite = {
-- 
2.47.0.rc1.288.g06298d1525-goog