1=pod 2 3=head1 NAME 4 5RAND_load_file, RAND_write_file, RAND_file_name - PRNG seed file 6 7=head1 SYNOPSIS 8 9 #include <openssl/rand.h> 10 11 int RAND_load_file(const char *filename, long max_bytes); 12 13 int RAND_write_file(const char *filename); 14 15 const char *RAND_file_name(char *buf, size_t num); 16 17=head1 DESCRIPTION 18 19RAND_load_file() reads a number of bytes from file B<filename> and 20adds them to the PRNG. If B<max_bytes> is nonnegative, 21up to B<max_bytes> are read; 22if B<max_bytes> is -1, the complete file is read. 23Do not load the same file multiple times unless its contents have 24been updated by RAND_write_file() between reads. 25Also, note that B<filename> should be adequately protected so that an 26attacker cannot replace or examine the contents. 27If B<filename> is not a regular file, then user is considered to be 28responsible for any side effects, e.g. non-anticipated blocking or 29capture of controlling terminal. 30 31RAND_write_file() writes a number of random bytes (currently 128) to 32file B<filename> which can be used to initialize the PRNG by calling 33RAND_load_file() in a later session. 34 35RAND_file_name() generates a default path for the random seed 36file. B<buf> points to a buffer of size B<num> in which to store the 37filename. 38 39On all systems, if the environment variable B<RANDFILE> is set, its 40value will be used as the seed filename. 41Otherwise, the file is called C<.rnd>, found in platform dependent locations: 42 43=over 4 44 45=item On Windows (in order of preference) 46 47 %HOME%, %USERPROFILE%, %SYSTEMROOT%, C:\ 48 49=item On VMS 50 51 SYS$LOGIN: 52 53=item On all other systems 54 55 $HOME 56 57=back 58 59If C<$HOME> (on non-Windows and non-VMS system) is not set either, or 60B<num> is too small for the pathname, an error occurs. 61 62=head1 RETURN VALUES 63 64RAND_load_file() returns the number of bytes read or -1 on error. 65 66RAND_write_file() returns the number of bytes written, or -1 if the 67bytes written were generated without appropriate seeding. 68 69RAND_file_name() returns a pointer to B<buf> on success, and NULL on 70error. 71 72=head1 SEE ALSO 73 74L<RAND_add(3)>, 75L<RAND_bytes(3)>, 76L<RAND(7)> 77 78=head1 COPYRIGHT 79 80Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved. 81 82Licensed under the OpenSSL license (the "License"). You may not use 83this file except in compliance with the License. You can obtain a copy 84in the file LICENSE in the source distribution or at 85L<https://www.openssl.org/source/license.html>. 86 87=cut 88