NAME

       RAND_load_file, RAND_write_file, RAND_file_name - PRNG seed file

SYNOPSIS

        #include <openssl/rand.h>

        int RAND_load_file(const char *filename, long max_bytes);

        int RAND_write_file(const char *filename);

        const char *RAND_file_name(char *buf, size_t num);

DESCRIPTION

       RAND_load_file() reads a number of bytes from file filename and adds them to the PRNG. If
       max_bytes is nonnegative, up to max_bytes are read; if max_bytes is -1, the complete file
       is read.  Do not load the same file multiple times unless its contents have been updated
       by RAND_write_file() between reads.  Also, note that filename should be adequately
       protected so that an attacker cannot replace or examine the contents.  If filename is not
       a regular file, then user is considered to be responsible for any side effects, e.g. non-
       anticipated blocking or capture of controlling terminal.

       RAND_write_file() writes a number of random bytes (currently 128) to file filename which
       can be used to initialize the PRNG by calling RAND_load_file() in a later session.

       RAND_file_name() generates a default path for the random seed file. buf points to a buffer
       of size num in which to store the filename.

       On all systems, if the environment variable RANDFILE is set, its value will be used as the
       seed filename.  Otherwise, the file is called ".rnd", found in platform dependent
       locations:

       On Windows (in order of preference)
            %HOME%, %USERPROFILE%, %SYSTEMROOT%, C:\

       On VMS
            SYS$LOGIN:

       On all other systems
            $HOME

       If $HOME (on non-Windows and non-VMS system) is not set either, or num is too small for
       the pathname, an error occurs.

RETURN VALUES

       RAND_load_file() returns the number of bytes read or -1 on error.

       RAND_write_file() returns the number of bytes written, or -1 if the bytes written were
       generated without appropriate seeding.

       RAND_file_name() returns a pointer to buf on success, and NULL on error.

SEE ALSO

       RAND_add(3), RAND_bytes(3), RAND(7)

COPYRIGHT

       Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the Apache License 2.0 (the "License").  You may not use this file except
       in compliance with the License.  You can obtain a copy in the file LICENSE in the source
       distribution or at <https://www.openssl.org/source/license.html>.