LRNG - add interface for gathering of raw entropy

The test interface allows a privileged process to capture the raw
unconditioned noise that is collected by the LRNG for statistical
analysis. Such testing allows the analysis how much entropy
the interrupt noise source provides on a given platform.
Extracted noise data is not used to seed the LRNG. This
is a test interface and not appropriate for production systems.
Yet, the interface is considered to be sufficiently secured for
production systems.

Access to the data is given through the lrng_raw debugfs file. The
data buffer should be multiples of sizeof(u32) to fill the entire
buffer. Using the option lrng_testing.boot_test=1 the raw noise of
the first 1000 entropy events since boot can be sampled.

This test interface allows generating the data required for
analysis whether the LRNG is in compliance with SP800-90B
sections 3.1.3 and 3.1.4.

In addition, the test interface allows gathering of the conatenated raw
entropy data to verify that the concatenation works appropriately.
This includes sampling of the following raw data:

* high-resolution time stamp

* Jiffies

* IRQ number

* IRQ flags

* return instruction pointer

* array logic batching the high-resolution time stamp

Finally, the execution duration for processing a time stamp can be
obtained with the LRNG raw entropy interface.

If a test interface is not compiled, its code is a noop which has no
impact on the performance.

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>
Reviewed-by: Roman Drahtmueller <draht@schaltsekun.de>
Tested-by: Roman Drahtmüller <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/Kconfig

@@ -163,4 +163,128 @@ config LRNG_APT_CUTOFF
 	default 325 if !LRNG_APT_BROKEN
 	default 32 if LRNG_APT_BROKEN
 
+menuconfig LRNG_TESTING_MENU
+	bool "LRNG testing interfaces"
+	depends on DEBUG_FS
+	help
+	  Enable one or more of the following test interfaces.
+
+	  If unsure, say N.
+
+if LRNG_TESTING_MENU
+
+config LRNG_RAW_HIRES_ENTROPY
+	bool "Enable entropy test interface to hires timer noise source"
+	default y
+	help
+	  The test interface allows a privileged process to capture
+	  the raw unconditioned high resolution time stamp noise that
+	  is collected by the LRNG for statistical analysis. Extracted
+	  noise data is not used to seed the LRNG.
+
+	  The raw noise data can be obtained using the lrng_raw_hires
+	  debugfs file. Using the option lrng_testing.boot_raw_hires_test=1
+	  the raw noise of the first 1000 entropy events since boot
+	  can be sampled.
+
+config LRNG_RAW_JIFFIES_ENTROPY
+	bool "Enable entropy test interface to Jiffies noise source"
+	help
+	  The test interface allows a privileged process to capture
+	  the raw unconditioned Jiffies that is collected by
+	  the LRNG for statistical analysis. This data is used for
+	  seeding the LRNG if a high-resolution time stamp is not
+	  available. If a high-resolution time stamp is detected,
+	  the Jiffies value is not collected by the LRNG and no
+	  data is provided via the test interface. Extracted noise
+	  data is not used to seed the random number generator.
+
+	  The raw noise data can be obtained using the lrng_raw_jiffies
+	  debugfs file. Using the option lrng_testing.boot_raw_jiffies_test=1
+	  the raw noise of the first 1000 entropy events since boot
+	  can be sampled.
+
+config LRNG_RAW_IRQ_ENTROPY
+	bool "Enable entropy test interface to IRQ number noise source"
+	help
+	  The test interface allows a privileged process to capture
+	  the raw unconditioned interrupt number that is collected by
+	  the LRNG for statistical analysis. This data is used for
+	  seeding the random32 PRNG external to the LRNG if a
+	  high-resolution time stamp is available or it will be used to
+	  seed the LRNG otherwise. Extracted noise data is not used to
+	  seed the random number generator.
+
+	  The raw noise data can be obtained using the lrng_raw_irq
+	  debugfs file. Using the option lrng_testing.boot_raw_irq_test=1
+	  the raw noise of the first 1000 entropy events since boot
+	  can be sampled.
+
+config LRNG_RAW_IRQFLAGS_ENTROPY
+	bool "Enable entropy test interface to IRQ flags noise source"
+	help
+	  The test interface allows a privileged process to capture
+	  the raw unconditioned interrupt flags that is collected by
+	  the LRNG for statistical analysis. This data is used for
+	  seeding the random32 PRNG external to the LRNG if a
+	  high-resolution time stamp is available or it will be used to
+	  seed the LRNG otherwise. Extracted noise data is not used to
+	  seed the random number generator.
+
+	  The raw noise data can be obtained using the lrng_raw_irqflags
+	  debugfs file. Using the option lrng_testing.boot_raw_irqflags_test=1
+	  the raw noise of the first 1000 entropy events since boot
+	  can be sampled.
+
+config LRNG_RAW_RETIP_ENTROPY
+	bool "Enable entropy test interface to RETIP value noise source"
+	help
+	  The test interface allows a privileged process to capture
+	  the raw unconditioned return instruction pointer value
+	  that is collected by the LRNG for statistical analysis.
+	  This data is used for seeding the random32 PRNG external
+	  to the LRNG if a high-resolution time stamp is available or
+	  it will be used to seed the LRNG otherwise. Extracted noise
+	  data is not used to seed the random number generator.
+
+	  The raw noise data can be obtained using the lrng_raw_retip
+	  debugfs file. Using the option lrng_testing.boot_raw_retip_test=1
+	  the raw noise of the first 1000 entropy events since boot
+	  can be sampled.
+
+config LRNG_RAW_ARRAY
+	bool "Enable test interface to LRNG raw entropy storage array"
+	help
+	  The test interface allows a privileged process to capture
+	  the raw noise data that is collected by the LRNG
+	  in the per-CPU array for statistical analysis. The purpose
+	  of this interface is to verify that the array handling code
+	  truly only concatenates data and provides the same entropy
+	  rate as the raw unconditioned noise source when assessing
+	  the collected data byte-wise.
+
+	  The data can be obtained using the lrng_raw_array debugfs
+	  file. Using the option lrng_testing.boot_raw_array=1
+	  the raw noise of the first 1000 entropy events since boot
+	  can be sampled.
+
+config LRNG_IRQ_PERF
+	bool "Enable LRNG interrupt performance monitor"
+	help
+	  With this option, the performance monitor of the LRNG
+	  interrupt handling code is enabled. The file provides
+	  the execution time of the interrupt handler in
+	  cycles.
+
+	  The interrupt performance data can be obtained using
+	  the lrng_irq_perf debugfs file. Using the option
+	  lrng_testing.boot_irq_perf=1 the performance data of
+	  the first 1000 entropy events since boot can be sampled.
+
+config LRNG_TESTING
+	bool
+	default y if (LRNG_RAW_ENTROPY || LRNG_RAW_ARRAY || LRNG_IRQ_PERF)
+
+endif #LRNG_TESTING_MENU
+
 endif # LRNG

drivers/char/lrng/Makefile

@@ -15,3 +15,4 @@ obj-$(CONFIG_LRNG_DRBG)		+= lrng_drbg.o
 obj-$(CONFIG_LRNG_KCAPI)	+= lrng_kcapi.o
 obj-$(CONFIG_LRNG_JENT)		+= lrng_jent.o
 obj-$(CONFIG_LRNG_HEALTH_TESTS)	+= lrng_health.o
+obj-$(CONFIG_LRNG_TESTING)	+= lrng_testing.o