getentropy(3) - NetBSD Manual Pages

GETENTROPY(3)           NetBSD Library Functions Manual          GETENTROPY(3)


NAME

     getentropy -- fill a buffer with high quality random data


LIBRARY

     Standard C Library (libc, -lc)


SYNOPSIS

     #include <unistd.h>

     int
     getentropy(void *buf, size_t buflen);

     #include <limits.h>
     #define GETENTROPY_MAX 256


DESCRIPTION

     The getentropy() function fills a buffer with high quality random data,
     suitable for seeding cryptographically secure psuedorandom number genera-
     tors.

     getentropy() is only intended for seeding random number generators and is
     not intended for use by regular code which simply needs secure random
     data.  For this purpose, please use arc4random(3).

     The maximum value for buflen is 256 bytes.


IMPLEMENTATION NOTES

     getentropy() reads from the sysctl(7) variable kern.arandom.


RETURN VALUES

     The getentropy() function returns the value 0 if successful; otherwise
     the value -1 is returned and the global variable errno is set to indicate
     the error.


ERRORS

     getentropy() will succeed unless:

     [EFAULT]           The buf argument points to an invalid memory address.

     [EINVAL]           More than 256 bytes were requested.


SEE ALSO

     arc4random(3), rnd(4)


STANDARDS

     The getentropy() function is non-standard.  However, it is likely to be
     included in the next revision of POSIX.


HISTORY

     The getentropy() function first appeared in OpenBSD 5.6, then in
     FreeBSD 12.0, and NetBSD 10.

NetBSD 10.99                      May 1, 2020                     NetBSD 10.99