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samples: random: Add sentinel to check for buffer overflows

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Initialize the buffer to 0 and read one byte less than the
buffer size. The result should be that the last byte of
the buffer always stays 0. This way it is possible to verify
it the driver does not write outside the buffer.

Signed-off-by: Erwin Rol <erwin@erwinrol.com>
This commit is contained in:
Erwin Rol 2017-06-30 23:53:34 +02:00 • committed by Kumar Gala
commit 3ff4d7409f
1 changed files with 16 additions and 6 deletions
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22
samples/drivers/random/src/main.c
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@ -25,18 +25,28 @@ void main(void)
while (1) {
#define BUFFER_LENGTH 10
u8_t buffer[BUFFER_LENGTH];
u8_t buffer[BUFFER_LENGTH] = {0};
int r;
r = random_get_entropy(dev, buffer, BUFFER_LENGTH);
/* The BUFFER_LENGTH-1 is used so the driver will not
* write the last byte of the buffer. If that last
* byte is not 0 on return it means the driver wrote
* outside the passed buffer, and that should never
* happen.
*/
r = random_get_entropy(dev, buffer, BUFFER_LENGTH-1);
if (r) {
printf("random_get_entropy failed: %d\n", r);
break;
};
}
for (int i = 0; i < BUFFER_LENGTH; i++) {
printf(" 0x%x", buffer[i]);
};
if (buffer[BUFFER_LENGTH-1] != 0) {
printf("random_get_entropy buffer overflow\n");
}
for (int i = 0; i < BUFFER_LENGTH-1; i++) {
printf(" 0x%02x", buffer[i]);
}
printf("\n");