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random: entropy: Return error in csrand

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Propagate driver error when getting entropy data when calling a
cryptographically secure random generator.

Signed-off-by: Flavio Ceolin <flavio.ceolin@intel.com>
This commit is contained in:
Flavio Ceolin 2020-01-24 15:39:26 -08:00 • committed by Andrew Boie
commit ade23d57b1
1 changed files with 19 additions and 7 deletions
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24
subsys/random/rand32_entropy_device.c
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@ -46,7 +46,7 @@ u32_t sys_rand32_get(void)
} }
#endif /* CONFIG_ENTROPY_DEVICE_RANDOM_GENERATOR */ #endif /* CONFIG_ENTROPY_DEVICE_RANDOM_GENERATOR */
static void rand_get(u8_t *dst, size_t outlen) static int rand_get(u8_t *dst, size_t outlen, bool csrand)
{ {
struct device *dev = entropy_driver; struct device *dev = entropy_driver;
u32_t random_num; u32_t random_num;
@ -67,6 +67,14 @@ static void rand_get(u8_t *dst, size_t outlen)
ret = entropy_get_entropy(dev, dst, outlen); ret = entropy_get_entropy(dev, dst, outlen);
if (unlikely(ret < 0)) { if (unlikely(ret < 0)) {
/* Don't try to fill the buffer in case of
* cryptographically secure random numbers, just
* propagate the driver error.
*/
if (csrand) {
return ret;
}
/* Use system timer in case the entropy device couldn't deliver /* Use system timer in case the entropy device couldn't deliver
* 32-bit of data. There's not much that can be done in this * 32-bit of data. There's not much that can be done in this
* situation. An __ASSERT() isn't used here as the HWRNG might * situation. An __ASSERT() isn't used here as the HWRNG might
@ -89,12 +97,14 @@ static void rand_get(u8_t *dst, size_t outlen)
len += blocksize; len += blocksize;
} }
} }
return 0;
} }
#if defined(CONFIG_ENTROPY_DEVICE_RANDOM_GENERATOR) #if defined(CONFIG_ENTROPY_DEVICE_RANDOM_GENERATOR)
void sys_rand_get(void *dst, size_t outlen) void sys_rand_get(void *dst, size_t outlen)
{ {
return rand_get(dst, outlen); rand_get(dst, outlen, false);
} }
#endif /* CONFIG_ENTROPY_DEVICE_RANDOM_GENERATOR */ #endif /* CONFIG_ENTROPY_DEVICE_RANDOM_GENERATOR */
@ -102,11 +112,13 @@ void sys_rand_get(void *dst, size_t outlen)
int sys_csrand_get(void *dst, size_t outlen) int sys_csrand_get(void *dst, size_t outlen)
{ {
rand_get(dst, outlen); if (rand_get(dst, outlen, true) != 0) {
/* need deeper inspection on hardware based RNG error cases. Right /* Is it the only error it should return ? entropy_sam
* now the assumption is that the HW will continue providing a stream * can return -ETIMEDOUT for example
* of RNG values
*/ */
return -EIO;
}
return 0; return 0;
} }