docs/syscalls/cprng_draw.md

# mx_cprng_draw

## NAME

mx_cprng_draw - Draw from the kernel's CPRNG

## SYNOPSIS

```
#include <magenta/syscalls.h>

mx_status_t mx_cprng_draw(void* buffer, size_t len, size_t* actual);
```

## DESCRIPTION

**mx_cprng_draw**() draws random bytes from the kernel CPRNG.  This data should be
suitable for cryptographic applications.  It will return at most
**MX_CPRNG_DRAW_MAX_LEN** bytes at a time.

## RETURN VALUE

**mx_cprng_draw**() returns MX_OK and the number of random bytes
drawn into *buffer* (via *actual) on success.

## ERRORS

**MX_ERR_INVALID_ARGS** *len* is too large, or *buffer* or *actual* is
not a valid userspace pointer.

## NOTES

There are no other error conditions.  If its arguments are valid,
**mx_cprng_draw**() will succeed.

## BUGS

This syscall should be rate-limited.