@@ -182,6 +182,33 @@ config LRNG_IRQ_ENTROPY_RATE
interrupt entropy source will still deliver data but without
being credited with entropy.
+comment "Jitter RNG Entropy Source"
+
+config LRNG_JENT
+ bool "Enable Jitter RNG as LRNG Seed Source"
+ depends on CRYPTO
+ select CRYPTO_JITTERENTROPY
+ help
+ The Linux RNG may use the Jitter RNG as noise source. Enabling
+ this option enables the use of the Jitter RNG. Its default
+ entropy level is 16 bits of entropy per 256 data bits delivered
+ by the Jitter RNG. This entropy level can be changed at boot
+ time or at runtime with the lrng_base.jitterrng configuration
+ variable.
+
+config LRNG_JENT_ENTROPY_RATE
+ int "Jitter RNG Entropy Source Entropy Rate"
+ range 0 256
+ default 16
+ help
+ The option defines the amount of entropy the LRNG applies to 256
+ bits of data obtained from the Jitter RNG entropy source. The
+ LRNG enforces the limit that this value must be in the range
+ between 0 and 256.
+
+ In order to disable the Jitter RNG entropy source, the option
+ has to be set to 0.
+
comment "CPU Entropy Source"
config LRNG_CPU_ENTROPY_RATE
@@ -14,3 +14,4 @@ obj-$(CONFIG_LRNG_DRNG_SWITCH) += lrng_switch.o
obj-$(CONFIG_LRNG_KCAPI_HASH) += lrng_kcapi_hash.o
obj-$(CONFIG_LRNG_DRBG) += lrng_drbg.o
obj-$(CONFIG_LRNG_KCAPI) += lrng_kcapi.o
+obj-$(CONFIG_LRNG_JENT) += lrng_jent.o
new file mode 100644
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
+/*
+ * LRNG Fast Entropy Source: Jitter RNG
+ *
+ * Copyright (C) 2016 - 2021, Stephan Mueller <smueller@chronox.de>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/types.h>
+#include <crypto/internal/jitterentropy.h>
+
+#include "lrng_internal.h"
+
+/*
+ * Estimated entropy of data is a 16th of LRNG_DRNG_SECURITY_STRENGTH_BITS.
+ * Albeit a full entropy assessment is provided for the noise source indicating
+ * that it provides high entropy rates and considering that it deactivates
+ * when it detects insufficient hardware, the chosen under estimation of
+ * entropy is considered to be acceptable to all reviewers.
+ */
+static u32 jitterrng = CONFIG_LRNG_JENT_ENTROPY_RATE;
+#ifdef CONFIG_LRNG_RUNTIME_ES_CONFIG
+module_param(jitterrng, uint, 0644);
+MODULE_PARM_DESC(jitterrng, "Entropy in bits of 256 data bits from Jitter RNG noise source");
+#endif
+
+static bool lrng_jent_initialized = false;
+static struct rand_data *lrng_jent_state;
+
+static int __init lrng_jent_initialize(void)
+{
+ /* Initialize the Jitter RNG after the clocksources are initialized. */
+ lrng_jent_state = jent_lrng_entropy_collector();
+ if (!lrng_jent_state) {
+ jitterrng = 0;
+ pr_info("Jitter RNG unusable on current system\n");
+ return 0;
+ }
+ lrng_jent_initialized = true;
+ lrng_pool_add_entropy();
+ pr_debug("Jitter RNG working on current system\n");
+
+ return 0;
+}
+device_initcall(lrng_jent_initialize);
+
+/**
+ * lrng_get_jent() - Get Jitter RNG entropy
+ *
+ * @outbuf: buffer to store entropy
+ * @outbuflen: length of buffer
+ *
+ * Return:
+ * * > 0 on success where value provides the added entropy in bits
+ * * 0 if no fast source was available
+ */
+u32 lrng_get_jent(u8 *outbuf, u32 requested_bits)
+{
+ int ret;
+ u32 ent_bits = lrng_jent_entropylevel(requested_bits);
+ unsigned long flags;
+ static DEFINE_SPINLOCK(lrng_jent_lock);
+
+ spin_lock_irqsave(&lrng_jent_lock, flags);
+
+ if (!ent_bits || !lrng_jent_initialized) {
+ spin_unlock_irqrestore(&lrng_jent_lock, flags);
+ return 0;
+ }
+
+ ret = jent_read_entropy(lrng_jent_state, outbuf, requested_bits >> 3);
+ spin_unlock_irqrestore(&lrng_jent_lock, flags);
+
+ if (ret) {
+ pr_debug("Jitter RNG failed with %d\n", ret);
+ return 0;
+ }
+
+ pr_debug("obtained %u bits of entropy from Jitter RNG noise source\n",
+ ent_bits);
+
+ return ent_bits;
+}
+
+u32 lrng_jent_entropylevel(u32 requested_bits)
+{
+ return lrng_fast_noise_entropylevel((lrng_jent_initialized) ?
+ jitterrng : 0, requested_bits);
+}