Re: [PATCH v28 06/12] LRNG - add SP800-90A DRBG extension

CC: "Eric W. Biederman" <redacted>
CC: "Alexander E. Patrakov" <redacted>
CC: "Ahmed S. Darwish" <redacted>
CC: "Theodore Y. Ts'o" <tytso@mit.edu>
CC: Willy Tarreau <w@1wt.eu>
CC: Matthew Garrett <mjg59@srcf.ucam.org>
CC: Vito Caputo <redacted>
CC: Andreas Dilger <adilger.kernel@dilger.ca>
CC: Jan Kara <jack@suse.cz>
CC: Ray Strode <redacted>
CC: William Jon McCann <redacted>
CC: zhangjs <redacted>
CC: Andy Lutomirski <luto@kernel.org>
CC: Florian Weimer <redacted>
CC: Lennart Poettering <redacted>
CC: Nicolai Stange <redacted>
Reviewed-by: Roman Drahtmueller <redacted>
Tested-by: Roman Drahtmüller <redacted>
Tested-by: Marcelo Henrique Cerri <redacted>
Tested-by: Neil Horman <redacted>
Signed-off-by: Stephan Mueller <redacted>
---
 drivers/char/lrng/Kconfig     |  11 ++
 drivers/char/lrng/Makefile    |   1 +
 drivers/char/lrng/lrng_drbg.c | 260 ++++++++++++++++++++++++++++++++++
 3 files changed, 272 insertions(+)
 create mode 100644 drivers/char/lrng/lrng_drbg.c

diff --git a/drivers/char/lrng/Kconfig b/drivers/char/lrng/Kconfig
index cb701bb0b8b6..15fb623d9d1f 100644
--- a/drivers/char/lrng/Kconfig
+++ b/drivers/char/lrng/Kconfig

@@ -71,4 +71,15 @@ menuconfig LRNG_DRNG_SWITCH
 	  accessible via the external interfaces. With this configuration
 	  option other DRNGs can be selected and loaded at runtime.
 
+if LRNG_DRNG_SWITCH
+config LRNG_DRBG
+	tristate "SP800-90A support for the LRNG"
+	select CRYPTO_DRBG_MENU
+	select CRYPTO_CMAC if CRYPTO_DRBG_CTR

diff --git a/drivers/char/lrng/lrng_drbg.c b/drivers/char/lrng/lrng_drbg.c
new file mode 100644
index 000000000000..8bf2badb1fe0
--- /dev/null
+++ b/drivers/char/lrng/lrng_drbg.c

@@ -0,0 +1,260 @@
+// SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
+/*
+ * Backend for the LRNG providing the cryptographic primitives using the
+ * kernel crypto API and its DRBG.
+ *
+ * Copyright (C) 2016 - 2020, Stephan Mueller <smueller@chronox.de>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <crypto/drbg.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/lrng.h>
+
+/*
+ * Define a DRBG plus a hash / MAC used to extract data from the entropy pool.
+ * For LRNG_HASH_NAME you can use a hash or a MAC (HMAC or CMAC) of your choice
+ * (Note, you should use the suggested selections below -- using SHA-1 or MD5
+ * is not wise). The idea is that the used cipher primitive can be selected to
+ * be the same as used for the DRBG. I.e. the LRNG only uses one cipher
+ * primitive using the same cipher implementation with the options offered in
+ * the following. This means, if the CTR DRBG is selected and AES-NI is present,
+ * both the CTR DRBG and the selected cmac(aes) use AES-NI.
+ *
+ * The security strengths of the DRBGs are all 256 bits according to
+ * SP800-57 section 5.6.1.
+ *
+ * This definition is allowed to be changed.
+ */
+#ifdef CONFIG_CRYPTO_DRBG_CTR
+static unsigned int lrng_drbg_type = 0;
+#elif defined CONFIG_CRYPTO_DRBG_HMAC
+static unsigned int lrng_drbg_type = 1;
+#elif defined CONFIG_CRYPTO_DRBG_HASH
+static unsigned int lrng_drbg_type = 2;
+#else
+#error "Unknown DRBG in use"
+#endif
+
+/* The parameter must be r/o in sysfs as otherwise races appear. */
+module_param(lrng_drbg_type, uint, 0444);
+MODULE_PARM_DESC(lrng_drbg_type, "DRBG type used for LRNG (0->CTR_DRBG, "
+				 "1->HMAC_DRBG, 2->Hash_DRBG)");