[PATCH v43 03/15] LRNG - sysctls and /proc interface

From: Stephan Müller
Date: Sun Nov 21 2021 - 11:50:39 EST


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@xxxxxx>
CC: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
CC: "Alexander E. Patrakov" <patrakov@xxxxxxxxx>
CC: "Ahmed S. Darwish" <darwish.07@xxxxxxxxx>
CC: "Theodore Y. Ts'o" <tytso@xxxxxxx>
CC: Willy Tarreau <w@xxxxxx>
CC: Matthew Garrett <mjg59@xxxxxxxxxxxxx>
CC: Vito Caputo <vcaputo@xxxxxxxxxxx>
CC: Andreas Dilger <adilger.kernel@xxxxxxxxx>
CC: Jan Kara <jack@xxxxxxx>
CC: Ray Strode <rstrode@xxxxxxxxxx>
CC: William Jon McCann <mccann@xxxxxxx>
CC: zhangjs <zachary@xxxxxxxxxxxxxxxx>
CC: Andy Lutomirski <luto@xxxxxxxxxx>
CC: Florian Weimer <fweimer@xxxxxxxxxx>
CC: Lennart Poettering <mzxreary@xxxxxxxxxxx>
CC: Nicolai Stange <nstange@xxxxxxx>
Reviewed-by: Alexander Lobakin <alobakin@xxxxx>
Tested-by: Alexander Lobakin <alobakin@xxxxx>
Reviewed-by: Marcelo Henrique Cerri <marcelo.cerri@xxxxxxxxxxxxx>
Reviewed-by: Roman Drahtmueller <draht@xxxxxxxxxxxxxx>
Tested-by: Marcelo Henrique Cerri <marcelo.cerri@xxxxxxxxxxxxx>
Tested-by: Neil Horman <nhorman@xxxxxxxxxx>
Tested-by: Jirka Hladky <jhladky@xxxxxxxxxx>
Reviewed-by: Jirka Hladky <jhladky@xxxxxxxxxx>
Signed-off-by: Stephan Mueller <smueller@xxxxxxxxxx>
---
drivers/char/lrng/Makefile | 1 +
drivers/char/lrng/lrng_interfaces.c | 2 -
drivers/char/lrng/lrng_proc.c | 199 ++++++++++++++++++++++++++++
3 files changed, 200 insertions(+), 2 deletions(-)
create mode 100644 drivers/char/lrng/lrng_proc.c

diff --git a/drivers/char/lrng/Makefile b/drivers/char/lrng/Makefile
index d321d6d21a44..d7df72a702e4 100644
--- a/drivers/char/lrng/Makefile
+++ b/drivers/char/lrng/Makefile
@@ -8,3 +8,4 @@ obj-y += lrng_es_mgr.o lrng_aux.o \
lrng_interfaces.o lrng_es_aux.o

obj-$(CONFIG_LRNG_IRQ) += lrng_es_irq.o
+obj-$(CONFIG_SYSCTL) += lrng_proc.o
diff --git a/drivers/char/lrng/lrng_interfaces.c b/drivers/char/lrng/lrng_interfaces.c
index 6316a534bb54..b656aaf0c6cb 100644
--- a/drivers/char/lrng/lrng_interfaces.c
+++ b/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? */
diff --git a/drivers/char/lrng/lrng_proc.c b/drivers/char/lrng/lrng_proc.c
new file mode 100644
index 000000000000..b48094c32b95
--- /dev/null
+++ b/drivers/char/lrng/lrng_proc.c
@@ -0,0 +1,199 @@
+// SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
+/*
+ * LRNG proc and sysctl interfaces
+ *
+ * Copyright (C) 2016 - 2021, Stephan Mueller <smueller@xxxxxxxxxx>
+ */
+
+#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"
+
+/*
+ * 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_WRITE_WAKEUP_ENTROPY << 3);
+static char lrng_sysctl_bootid[16];
+static int lrng_drng_reseed_max_min;
+
+void lrng_proc_update_max_write_thresh(u32 new_digestsize)
+{
+ lrng_max_write_thresh = (int)new_digestsize;
+ mb();
+}
+
+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[250], irq[200], aux[100], cpu[90], jent[45];
+
+ lrng_drng_lock(lrng_drng_init, &flags);
+ snprintf(buf, sizeof(buf),
+ "DRNG name: %s\n"
+ "LRNG security strength in bits: %d\n"
+ "number of DRNG instances: %u\n"
+ "Standards compliance: %s\n"
+ "Entropy Sources: %s%s%sAuxiliary\n"
+ "LRNG minimally seeded: %s\n"
+ "LRNG fully seeded: %s\n",
+ lrng_drng_init->crypto_cb->lrng_drng_name(),
+ lrng_security_strength(),
+ numa_drngs,
+ lrng_sp80090c_compliant() ? "SP800-90C " : "",
+ IS_ENABLED(CONFIG_LRNG_IRQ) ? "IRQ " : "",
+ IS_ENABLED(CONFIG_LRNG_JENT) ? "JitterRNG " : "",
+ IS_ENABLED(CONFIG_LRNG_CPU) ? "CPU " : "",
+ lrng_state_min_seeded() ? "true" : "false",
+ lrng_state_fully_seeded() ? "true" : "false");
+
+ lrng_aux_es_state(aux, sizeof(aux));
+
+ irq[0] = '\0';
+ lrng_irq_es_state(irq, sizeof(irq));
+
+ jent[0] = '\0';
+ lrng_jent_es_state(jent, sizeof(jent));
+
+ cpu[0] = '\0';
+ lrng_arch_es_state(cpu, sizeof(cpu));
+
+ lrng_drng_unlock(lrng_drng_init, &flags);
+
+ seq_write(m, buf, strlen(buf));
+ seq_write(m, aux, strlen(aux));
+ seq_write(m, irq, strlen(irq));
+ seq_write(m, jent, strlen(jent));
+ seq_write(m, cpu, strlen(cpu));
+
+ 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);
--
2.31.1