char/lrng: sysctls and /proc interface

The LRNG sysctl interface provides the same controls as the existing
/dev/random implementation. These sysctls behave identically and are
implemented identically. The goal is to allow a possible merge of the
existing /dev/random implementation with this implementation which
implies that this patch tries have a very close similarity. Yet, all
sysctls are documented at [1].

In addition, it provides the file lrng_type which provides details about
the LRNG:

- the name of the DRNG that produces the random numbers for /dev/random,
/dev/urandom, getrandom(2)

- the hash used to produce random numbers from the entropy pool

- the number of secondary DRNG instances

- indicator whether the LRNG operates SP800-90B compliant

- indicator whether a high-resolution timer is identified - only with a
high-resolution timer the interrupt noise source will deliver sufficient
entropy

- indicator whether the LRNG has been minimally seeded (i.e. is the
secondary DRNG seeded with at least 128 bits of entropy)

- indicator whether the LRNG has been fully seeded (i.e. is the
secondary DRNG seeded with at least 256 bits of entropy)

[1] https://www.chronox.de/lrng.html

CC: Torsten Duwe <duwe@lst.de>
CC: "Eric W. Biederman" <ebiederm@xmission.com>
CC: "Alexander E. Patrakov" <patrakov@gmail.com>
CC: "Ahmed S. Darwish" <darwish.07@gmail.com>
CC: "Theodore Y. Ts'o" <tytso@mit.edu>
CC: Willy Tarreau <w@1wt.eu>
CC: Matthew Garrett <mjg59@srcf.ucam.org>
CC: Vito Caputo <vcaputo@pengaru.com>
CC: Andreas Dilger <adilger.kernel@dilger.ca>
CC: Jan Kara <jack@suse.cz>
CC: Ray Strode <rstrode@redhat.com>
CC: William Jon McCann <mccann@jhu.edu>
CC: zhangjs <zachary@baishancloud.com>
CC: Andy Lutomirski <luto@kernel.org>
CC: Florian Weimer <fweimer@redhat.com>
CC: Lennart Poettering <mzxreary@0pointer.de>
CC: Nicolai Stange <nstange@suse.de>
CC: Alexander Lobakin <alobakin@mailbox.org>
Reviewed-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com>
Reviewed-by: Roman Drahtmueller <draht@schaltsekun.de>
Tested-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com>
Tested-by: Neil Horman <nhorman@redhat.com>
Signed-off-by: Stephan Mueller <smueller@chronox.de>

drivers/char/lrng/Makefile

@@ -9,3 +9,4 @@ obj-y				+= lrng_pool.o lrng_aux.o \
 				   lrng_interfaces.o
 
 obj-$(CONFIG_NUMA)		+= lrng_numa.o
+obj-$(CONFIG_SYSCTL)		+= lrng_proc.o

drivers/char/lrng/lrng_interfaces.c

@@ -38,8 +38,6 @@ static DECLARE_WAIT_QUEUE_HEAD(lrng_write_wait);
 static DECLARE_WAIT_QUEUE_HEAD(lrng_init_wait);
 static struct fasync_struct *fasync;
 
-struct ctl_table random_table[];
-
 /********************************** Helper ***********************************/
 
 /* Is the DRNG seed level too low? */

drivers/char/lrng/lrng_internal.h

@@ -114,7 +114,11 @@ void lrng_cc20_init_state(struct chacha20_state *state);
 
 /********************************** /proc *************************************/
 
+#ifdef CONFIG_SYSCTL
+void lrng_pool_inc_numa_node(void);
+#else
 static inline void lrng_pool_inc_numa_node(void) { }
+#endif
 
 /****************************** LRNG interfaces *******************************/
 

drivers/char/lrng/lrng_proc.c

@@ -0,0 +1,185 @@
+// SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
+/*
+ * LRNG proc and sysctl interfaces
+ *
+ * Copyright (C) 2016 - 2021, Stephan Mueller <smueller@chronox.de>
+ */
+
+#include <linux/lrng.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/sysctl.h>
+#include <linux/uuid.h>
+
+#include "lrng_internal.h"
+#include "lrng_sw_noise.h"
+
+/*
+ * This function is used to return both the bootid UUID, and random
+ * UUID.  The difference is in whether table->data is NULL; if it is,
+ * then a new UUID is generated and returned to the user.
+ *
+ * If the user accesses this via the proc interface, the UUID will be
+ * returned as an ASCII string in the standard UUID format; if via the
+ * sysctl system call, as 16 bytes of binary data.
+ */
+static int lrng_proc_do_uuid(struct ctl_table *table, int write,
+			     void *buffer, size_t *lenp, loff_t *ppos)
+{
+	struct ctl_table fake_table;
+	unsigned char buf[64], tmp_uuid[16], *uuid;
+
+	uuid = table->data;
+	if (!uuid) {
+		uuid = tmp_uuid;
+		generate_random_uuid(uuid);
+	} else {
+		static DEFINE_SPINLOCK(bootid_spinlock);
+
+		spin_lock(&bootid_spinlock);
+		if (!uuid[8])
+			generate_random_uuid(uuid);
+		spin_unlock(&bootid_spinlock);
+	}
+
+	sprintf(buf, "%pU", uuid);
+
+	fake_table.data = buf;
+	fake_table.maxlen = sizeof(buf);
+
+	return proc_dostring(&fake_table, write, buffer, lenp, ppos);
+}
+
+static int lrng_proc_do_entropy(struct ctl_table *table, int write,
+				void *buffer, size_t *lenp, loff_t *ppos)
+{
+	struct ctl_table fake_table;
+	int entropy_count;
+
+	entropy_count = lrng_avail_entropy();
+
+	fake_table.data = &entropy_count;
+	fake_table.maxlen = sizeof(entropy_count);
+
+	return proc_dointvec(&fake_table, write, buffer, lenp, ppos);
+}
+
+static int lrng_proc_do_poolsize(struct ctl_table *table, int write,
+				 void *buffer, size_t *lenp, loff_t *ppos)
+{
+	struct ctl_table fake_table;
+	int entropy_count;
+
+	/* LRNG can at most retain entropy in per-CPU pools and aux pool */
+	entropy_count = lrng_get_digestsize() + lrng_pcpu_avail_pool_size();
+
+	fake_table.data = &entropy_count;
+	fake_table.maxlen = sizeof(entropy_count);
+
+	return proc_dointvec(&fake_table, write, buffer, lenp, ppos);
+}
+
+static int lrng_min_write_thresh;
+static int lrng_max_write_thresh = LRNG_MAX_DIGESTSIZE;
+static char lrng_sysctl_bootid[16];
+static int lrng_drng_reseed_max_min;
+
+struct ctl_table random_table[] = {
+	{
+		.procname	= "poolsize",
+		.maxlen		= sizeof(int),
+		.mode		= 0444,
+		.proc_handler	= lrng_proc_do_poolsize,
+	},
+	{
+		.procname	= "entropy_avail",
+		.maxlen		= sizeof(int),
+		.mode		= 0444,
+		.proc_handler	= lrng_proc_do_entropy,
+	},
+	{
+		.procname	= "write_wakeup_threshold",
+		.data		= &lrng_write_wakeup_bits,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &lrng_min_write_thresh,
+		.extra2		= &lrng_max_write_thresh,
+	},
+	{
+		.procname	= "boot_id",
+		.data		= &lrng_sysctl_bootid,
+		.maxlen		= 16,
+		.mode		= 0444,
+		.proc_handler	= lrng_proc_do_uuid,
+	},
+	{
+		.procname	= "uuid",
+		.maxlen		= 16,
+		.mode		= 0444,
+		.proc_handler	= lrng_proc_do_uuid,
+	},
+	{
+		.procname       = "urandom_min_reseed_secs",
+		.data           = &lrng_drng_reseed_max_time,
+		.maxlen         = sizeof(int),
+		.mode           = 0644,
+		.proc_handler   = proc_dointvec,
+		.extra1		= &lrng_drng_reseed_max_min,
+	},
+	{ }
+};
+
+/* Number of online DRNGs */
+static u32 numa_drngs = 1;
+
+void lrng_pool_inc_numa_node(void)
+{
+	numa_drngs++;
+}
+
+static int lrng_proc_type_show(struct seq_file *m, void *v)
+{
+	struct lrng_drng *lrng_drng_init = lrng_drng_init_instance();
+	unsigned long flags = 0;
+	unsigned char buf[390];
+
+	lrng_drng_lock(lrng_drng_init, &flags);
+	snprintf(buf, sizeof(buf),
+		 "DRNG name: %s\n"
+		 "Hash for reading entropy pool: %s\n"
+		 "Hash for operating aux entropy pool: %s\n"
+		 "LRNG security strength in bits: %d\n"
+		 "per-CPU interrupt collection size: %u\n"
+		 "number of DRNG instances: %u\n"
+		 "Standards compliance: %s%s\n"
+		 "High-resolution timer: %s\n"
+		 "LRNG minimally seeded: %s\n"
+		 "LRNG fully seeded: %s\n"
+		 "Continuous compression: %s\n",
+		 lrng_drng_init->crypto_cb->lrng_drng_name(),
+		 lrng_drng_init->crypto_cb->lrng_hash_name(),
+		 lrng_drng_init->crypto_cb->lrng_hash_name(),
+		 lrng_security_strength(),
+		 LRNG_DATA_NUM_VALUES,
+		 numa_drngs,
+		 lrng_sp80090b_compliant() ? "SP800-90B " : "",
+		 lrng_sp80090c_compliant() ? "SP800-90C " : "",
+		 lrng_pool_highres_timer() ? "true" : "false",
+		 lrng_state_min_seeded() ? "true" : "false",
+		 lrng_state_fully_seeded() ? "true" : "false",
+		 lrng_pcpu_continuous_compression_state() ? "true" : "false");
+	lrng_drng_unlock(lrng_drng_init, &flags);
+
+	seq_write(m, buf, strlen(buf));
+
+	return 0;
+}
+
+static int __init lrng_proc_type_init(void)
+{
+	proc_create_single("lrng_type", 0444, NULL, &lrng_proc_type_show);
+	return 0;
+}
+
+module_init(lrng_proc_type_init);