Updated: 2021/Apr/14


RAND_load_file(3)                   OpenSSL                  RAND_load_file(3)



NAME
       RAND_load_file, RAND_write_file, RAND_file_name - PRNG seed file

LIBRARY
       libcrypto, -lcrypto

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 OpenSSL license (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>.



1.1.1i                            2020-12-10                 RAND_load_file(3)