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.\" ========================================================================
.\"
.IX Title "RAND_LOAD_FILE 3"
.TH RAND_LOAD_FILE 3 "2023-09-11" "1.1.1w" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
RAND_load_file, RAND_write_file, RAND_file_name \- PRNG seed file
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #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);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fBRAND_load_file()\fR reads a number of bytes from file \fBfilename\fR and
adds them to the \s-1PRNG.\s0 If \fBmax_bytes\fR is nonnegative,
up to \fBmax_bytes\fR are read;
if \fBmax_bytes\fR is \-1, the complete file is read.
Do not load the same file multiple times unless its contents have
been updated by \fBRAND_write_file()\fR between reads.
Also, note that \fBfilename\fR should be adequately protected so that an
attacker cannot replace or examine the contents.
If \fBfilename\fR 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.
.PP
\&\fBRAND_write_file()\fR writes a number of random bytes (currently 128) to
file \fBfilename\fR which can be used to initialize the \s-1PRNG\s0 by calling
\&\fBRAND_load_file()\fR in a later session.
.PP
\&\fBRAND_file_name()\fR generates a default path for the random seed
file. \fBbuf\fR points to a buffer of size \fBnum\fR in which to store the
filename.
.PP
On all systems, if the environment variable \fB\s-1RANDFILE\s0\fR is set, its
value will be used as the seed filename.
Otherwise, the file is called \f(CW\*(C`.rnd\*(C'\fR, found in platform dependent locations:
.IP "On Windows (in order of preference)" 4
.IX Item "On Windows (in order of preference)"
.Vb 1
\& %HOME%, %USERPROFILE%, %SYSTEMROOT%, C:\e
.Ve
.IP "On \s-1VMS\s0" 4
.IX Item "On VMS"
.Vb 1
\& SYS$LOGIN:
.Ve
.IP "On all other systems" 4
.IX Item "On all other systems"
.Vb 1
\& $HOME
.Ve
.PP
If \f(CW$HOME\fR (on non-Windows and non-VMS system) is not set either, or
\&\fBnum\fR is too small for the pathname, an error occurs.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBRAND_load_file()\fR returns the number of bytes read or \-1 on error.
.PP
\&\fBRAND_write_file()\fR returns the number of bytes written, or \-1 if the
bytes written were generated without appropriate seeding.
.PP
\&\fBRAND_file_name()\fR returns a pointer to \fBbuf\fR on success, and \s-1NULL\s0 on
error.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBRAND_add\fR\|(3),
\&\fBRAND_bytes\fR\|(3),
\&\s-1\fBRAND\s0\fR\|(7)
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2000\-2020 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the OpenSSL license (the \*(L"License\*(R").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file \s-1LICENSE\s0 in the source distribution or at
<https://www.openssl.org/source/license.html>.