5 RAND_load_file, RAND_write_file, RAND_file_name - PRNG seed file
9 #include <openssl/rand.h>
11 int RAND_load_file(const char *filename, long max_bytes);
13 int RAND_write_file(const char *filename);
15 const char *RAND_file_name(char *buf, size_t num);
19 RAND_load_file() reads a number of bytes from file B<filename> and
20 adds them to the PRNG. If B<max_bytes> is non-negative,
21 up to B<max_bytes> are read;
22 if B<max_bytes> is -1, the complete file is read.
24 RAND_write_file() writes a number of random bytes (currently 256) to
25 file B<filename> which can be used to initialize the PRNG by calling
26 RAND_load_file() in a later session.
28 RAND_file_name() generates a default path for the random seed
29 file. B<buf> points to a buffer of size B<num> in which to store the
32 On all systems, if the environment variable B<RANDFILE> is set, its
33 value will be used as the seed file name.
34 Otherwise, the file is called C<.rnd>, found in platform dependent locations:
38 =item On Windows (in order of preference)
40 %HOME%, %USERPROFILE%, %SYSTEMROOT%, C:\
46 =item On all other systems
52 If C<$HOME> (on non-Windows and non-VMS system) is not set either, or
53 B<num> is too small for the path name, an error occurs.
57 RAND_load_file() returns the number of bytes read.
59 RAND_write_file() returns the number of bytes written, and -1 if the
60 bytes written were generated without appropriate seed.
62 RAND_file_name() returns a pointer to B<buf> on success, and NULL on
67 L<RAND_bytes(3)>, L<RAND_add(3)>
71 A comment in the source since at least OpenSSL version 1.0.2 said that
72 RAND_load_file() and RAND_write_file() were only intended for regular files,
73 and not really device special files such as C</dev/random>. This was
74 poorly enforced before OpenSSL version 1.1.1.
78 Copyright 2000-2017 The OpenSSL Project Authors. All Rights Reserved.
80 Licensed under the OpenSSL license (the "License"). You may not use
81 this file except in compliance with the License. You can obtain a copy
82 in the file LICENSE in the source distribution or at
83 L<https://www.openssl.org/source/license.html>.