random: Change testing random generator

The old random timer test was not random-looking
enough on some platforms.

Replace with new test which is psuedo-xoshiro.

The generator is still deterministic
and does not depend on entropy at all,
but should look more random for testing.

Change name of generator tree-wide also.

Signed-off-by: Declan Snyder <declan.snyder@nxp.com>

doc/services/crypto/random/index.rst

@@ -47,9 +47,9 @@ An override of the default value can be specified in the SOC or board
 
 The random number generators available include:
 
-:kconfig:option:`CONFIG_TIMER_RANDOM_GENERATOR`
- enables number generator based on system timer clock. This number
- generator is not random and used for testing only.
+:kconfig:option:`CONFIG_RANDOM_TEST_GENERATOR`
+ This number generator is not random and used for testing only.
+ This generator does not depend on entropy.
 
 :kconfig:option:`CONFIG_ENTROPY_DEVICE_RANDOM_GENERATOR`
  enables a random number generator that uses the enabled hardware

samples/subsys/usb/hid-cdc/boards/nrf5340dk_nrf5340_cpuapp.conf

@@ -1,2 +1,2 @@
 CONFIG_TEST_RANDOM_GENERATOR=y
-CONFIG_TIMER_RANDOM_GENERATOR=y
+CONFIG_RANDOM_TEST_GENERATOR=y

subsys/random/CMakeLists.txt

@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: Apache-2.0
 
 if (CONFIG_ENTROPY_DEVICE_RANDOM_GENERATOR OR
-    CONFIG_TIMER_RANDOM_GENERATOR OR
+    CONFIG_RANDOM_TEST_GENERATOR OR
     CONFIG_XOSHIRO_RANDOM_GENERATOR)
 zephyr_library()
 zephyr_library_sources_ifdef(CONFIG_USERSPACE           rand32_handlers.c)
@@ -17,10 +17,10 @@ endif()
 # XOROSHIRO builds the XOSHIRO implementation because a Kconfig choice cannot
 # select another choice as a means of deprecating the symbol. Swapping out the
 # implementation lets out-of-tree users still build until the symbol is removed.
-zephyr_library_sources_ifdef(CONFIG_TIMER_RANDOM_GENERATOR          rand32_timer.c)
 zephyr_library_sources_ifdef(CONFIG_XOROSHIRO_RANDOM_GENERATOR      rand32_xoshiro128.c)
 zephyr_library_sources_ifdef(CONFIG_XOSHIRO_RANDOM_GENERATOR        rand32_xoshiro128.c)
 zephyr_library_sources_ifdef(CONFIG_CTR_DRBG_CSPRNG_GENERATOR       rand32_ctr_drbg.c)
+zephyr_library_sources_ifdef(CONFIG_RANDOM_TEST_GENERATOR	    rand32_test.c)
 
 if (CONFIG_ENTROPY_DEVICE_RANDOM_GENERATOR OR CONFIG_HARDWARE_DEVICE_CS_GENERATOR)
 zephyr_library_sources(rand32_entropy_device.c)

subsys/random/Kconfig

@@ -40,13 +40,12 @@ choice RNG_GENERATOR_CHOICE
 	  to support random request then select that. Otherwise, select the
 	  XOSHIRO algorithm
 
-config TIMER_RANDOM_GENERATOR
+config RANDOM_TEST_GENERATOR
 	bool "System timer clock based number generator"
 	depends on TEST_RANDOM_GENERATOR
 	help
-	  This options enables number generator based on system timer
-	  clock. This number generator is not random and used for
-	  testing only.
+	  This number generator is not random and used only for testing.
+	  Does not rely on an entropy driver, so can be used without entropy.
 
 config ENTROPY_DEVICE_RANDOM_GENERATOR
 	bool "Use entropy driver to generate random numbers"

subsys/random/rand32_test.c

@@ -14,21 +14,44 @@
  * provide a random number generator.
  */
 
+#include <zephyr/init.h>
 #include <zephyr/random/rand32.h>
 #include <zephyr/drivers/timer/system_timer.h>
 #include <zephyr/kernel.h>
-#include <zephyr/sys/atomic.h>
 #include <string.h>
+#include <zephyr/device.h>
 
 #if defined(__GNUC__)
 
-/*
- * Symbols used to ensure a rapid series of calls to random number generator
- * return different values.
- */
-static atomic_val_t _rand32_counter;
+/* seed the state with pseudo-random data */
+static uint32_t state[4] = {0, 0x9b64c2b0, 0x86d3d2d4, 0xa00ae278};
+
+static struct k_spinlock rand_state_lock;
+
+static inline uint32_t rotl(const uint32_t x, int k)
+{
+	return (x << k) | (x >> (32 - k));
+}
+
+static uint32_t xoshiro128_next(void)
+{
+	const uint32_t result = rotl(state[0] + state[3], 7) + state[0];
+	const uint32_t t = state[1] << 9;
+
+	k_spinlock_key_t lock_key = k_spin_lock(&rand_state_lock);
+
+	state[2] ^= state[0];
+	state[3] ^= state[1];
+	state[1] ^= state[2];
+	state[0] ^= state[3];
+
+	state[2] ^= t;
+	state[3] = rotl(state[3], 11);
 
-#define _RAND32_INC 1000000003U
+	k_spin_unlock(&rand_state_lock, lock_key);
+
+	return result;
+}
 
 /**
  * @brief Get a 32 bit random number
@@ -41,7 +64,7 @@ static atomic_val_t _rand32_counter;
  */
 uint32_t z_impl_sys_rand32_get(void)
 {
-	return k_cycle_get_32() + atomic_add(&_rand32_counter, _RAND32_INC);
+	return xoshiro128_next();
 }
 
 /**
@@ -68,4 +91,5 @@ void z_impl_sys_rand_get(void *dst, size_t outlen)
 		outlen -= blocksize;
 	}
 }
+
 #endif /* __GNUC__ */

tests/crypto/rand32/prj_sw_random_systimer.conf

@@ -3,4 +3,4 @@ CONFIG_ZTEST_NEW_API=y
 CONFIG_LOG=y
 CONFIG_ENTROPY_GENERATOR=y
 CONFIG_TEST_RANDOM_GENERATOR=y
-CONFIG_TIMER_RANDOM_GENERATOR=y
+CONFIG_RANDOM_TEST_GENERATOR=y

tests/net/lib/mqtt_publisher/prj_tls.conf

@@ -2,7 +2,7 @@ CONFIG_NETWORKING=y
 CONFIG_NET_TCP=y
 CONFIG_ENTROPY_GENERATOR=y
 CONFIG_TEST_RANDOM_GENERATOR=y
-CONFIG_TIMER_RANDOM_GENERATOR=y
+CONFIG_RANDOM_TEST_GENERATOR=y
 
 CONFIG_NET_ARP=y
 CONFIG_NET_L2_ETHERNET=y

tests/ztest/base/prj_verbose_0.conf

@@ -4,7 +4,7 @@ CONFIG_ZTEST_ASSERT_VERBOSE=0
 
 CONFIG_ENTROPY_GENERATOR=y
 CONFIG_TEST_RANDOM_GENERATOR=y
-CONFIG_TIMER_RANDOM_GENERATOR=y
+CONFIG_RANDOM_TEST_GENERATOR=y
 
 CONFIG_ZTEST_SHUFFLE=y
 CONFIG_ZTEST_SHUFFLE_SUITE_REPEAT_COUNT=2