From: Steffen Trumtrar <s.trumtrar@xxxxxxxxxxxxxx>
Instead of generating pseudo random numbers, get random bytes
from an optional HW generator, if enabled and registered.
Signed-off-by: Steffen Trumtrar <s.trumtrar@xxxxxxxxxxxxxx>
Signed-off-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
---
include/stdlib.h | 1 +
lib/Kconfig | 9 +++++++++
lib/random.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 68 insertions(+)
diff --git a/include/stdlib.h b/include/stdlib.h
index f3185069f..ee3f22996 100644
--- a/include/stdlib.h
+++ b/include/stdlib.h
@@ -13,6 +13,7 @@ void srand(unsigned int seed);
/* fill a buffer with pseudo-random data */
void get_random_bytes(void *buf, int len);
+int get_crypto_bytes(void *buf, int len);
static inline u32 random32(void)
{
diff --git a/lib/Kconfig b/lib/Kconfig
index f9f25bdef..c16511c05 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -66,6 +66,15 @@ config RATP
transferring packets over serial links described in RFC916. This implementation
is used for controlling barebox over serial ports.
+config ALLOW_PRNG_FALLBACK
+ bool "Allow fallback to PRNG if HWRNG not available."
+ help
+ WARNING: it is not secure!!
+
+ get_crypto_bytes() users like cmd_password relay on HWRNG. If HWRNG is not
+ available and this option is disabled, cmd_password will fail.
+ Enable it on your own risk.
+
source lib/gui/Kconfig
source lib/fonts/Kconfig
diff --git a/lib/random.c b/lib/random.c
index 210fea994..fa1fa5606 100644
--- a/lib/random.c
+++ b/lib/random.c
@@ -1,5 +1,6 @@
#include <common.h>
#include <stdlib.h>
+#include <linux/hw_random.h>
static unsigned int random_seed;
@@ -18,6 +19,11 @@ void srand(unsigned int seed)
random_seed = seed;
}
+/**
+ * get_random_bytes - get pseudo random numbers.
+ * This interface can be good enough to generate MAC address
+ * or use for NAND test.
+ */
void get_random_bytes(void *_buf, int len)
{
char *buf = _buf;
@@ -25,3 +31,55 @@ void get_random_bytes(void *_buf, int len)
while (len--)
*buf++ = rand() % 256;
}
+
+/**
+ * get_crypto_bytes - get random numbers suitable for cryptographic needs.
+ */
+static int _get_crypto_bytes(void *_buf, int len)
+{
+ struct hwrng *rng;
+ u8 *buf = _buf;
+
+ if (!IS_ENABLED(CONFIG_HWRNG))
+ return -ENOENT;
+
+ rng = hwrng_get_first();
+ if (IS_ERR(rng))
+ return PTR_ERR(rng);
+
+ while (len) {
+ int bytes = hwrng_get_data(rng, buf, len, true);
+ if (!bytes)
+ return -ENOMEDIUM;
+
+ if (bytes < 0)
+ return bytes;
+
+ if (bytes > len)
+ bytes = len;
+ len -= bytes;
+ buf = buf + bytes;
+ }
+
+ return 0;
+}
+
+int get_crypto_bytes(void *buf, int len)
+{
+ int err;
+
+ err = _get_crypto_bytes(buf, len);
+ if (!err)
+ return 0;
+
+ if (!IS_ENABLED(CONFIG_ALLOW_PRNG_FALLBACK)) {
+ pr_err("error: no HWRNG available!\n");
+ return err;
+ }
+
+ pr_warn("warning: falling back to Pseudo RNG source!\n");
+
+ get_random_bytes(buf, len);
+
+ return 0;
+}
--
2.11.0
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