1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
|
=pod
=head1 NAME
SSL_get_client_random, SSL_get_server_random, SSL_SESSION_get_master_key - retrieve internal TLS/SSL random values and master key
=head1 SYNOPSIS
#include <openssl/ssl.h>
size_t SSL_get_client_random(const SSL *ssl, unsigned char *out, size_t outlen);
size_t SSL_get_server_random(const SSL *ssl, unsigned char *out, size_t outlen);
size_t SSL_SESSION_get_master_key(const SSL_SESSION *session, unsigned char *out, size_t outlen);
=head1 DESCRIPTION
SSL_get_client_random() extracts the random value sent from the client
to the server during the initial SSL/TLS handshake. It copies as many
bytes as it can of this value into the buffer provided in B<out>,
which must have at least B<outlen> bytes available. It returns the
total number of bytes that were actually copied. If B<outlen> is
zero, SSL_get_client_random() copies nothing, and returns the
total size of the client_random value.
SSL_get_server_random() behaves the same, but extracts the random value
sent from the server to the client during the initial SSL/TLS handshake.
SSL_SESSION_get_master_key() behaves the same, but extracts the master
secret used to guarantee the security of the SSL/TLS session. This one
can be dangerous if misused; see NOTES below.
=head1 NOTES
You probably shouldn't use these functions.
These functions expose internal values from the TLS handshake, for
use in low-level protocols. You probably should not use them, unless
you are implementing something that needs access to the internal protocol
details.
Despite the names of SSL_get_client_random() and SSL_get_server_random(), they
ARE NOT random number generators. Instead, they return the mostly-random values that
were already generated and used in the TLS protocol. Using them
in place of RAND_bytes() would be grossly foolish.
The security of your TLS session depends on keeping the master key secret:
do not expose it, or any information about it, to anybody.
If you need to calculate another secret value that depends on the master
secret, you should probably use SSL_export_keying_material() instead, and
forget that you ever saw these functions.
In current versions of the TLS protocols, the length of client_random
(and also server_random) is always SSL3_RANDOM_SIZE bytes. Support for
other outlen arguments to the SSL_get_*_random() functions is provided
in case of the unlikely event that a future version or variant of TLS
uses some other length there.
Finally, though the "client_random" and "server_random" values are called
"random", many TLS implementations will generate four bytes of those
values based on their view of the current time.
=head1 RETURN VALUES
If B<outlen> is greater than 0, these functions return the number of bytes
actually copied, which will be less than or equal to B<outlen>.
If B<outlen> is 0, these functions return the maximum number
of bytes they would copy--that is, the length of the underlying field.
=head1 SEE ALSO
L<ssl(3)>,
L<RAND_bytes(3)>,
L<SSL_export_keying_material(3)>
=cut
|