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1 | =pod |
2 | ||
3 | =head1 NAME | |
4 | ||
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5 | SSL_get_client_random, |
6 | SSL_get_server_random, | |
7 | SSL_SESSION_get_master_key, | |
8 | SSL_SESSION_set1_master_key | |
9 | - get internal TLS/SSL random values and get/set master key | |
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10 | |
11 | =head1 SYNOPSIS | |
12 | ||
13 | #include <openssl/ssl.h> | |
14 | ||
d9f1c639 MC |
15 | size_t SSL_get_client_random(const SSL *ssl, unsigned char *out, size_t outlen); |
16 | size_t SSL_get_server_random(const SSL *ssl, unsigned char *out, size_t outlen); | |
e9b77246 BB |
17 | size_t SSL_SESSION_get_master_key(const SSL_SESSION *session, |
18 | unsigned char *out, size_t outlen); | |
725b0f1e | 19 | int SSL_SESSION_set1_master_key(SSL_SESSION *sess, const unsigned char *in, |
5eb72736 | 20 | size_t len); |
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21 | |
22 | =head1 DESCRIPTION | |
23 | ||
24 | SSL_get_client_random() extracts the random value sent from the client | |
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25 | to the server during the initial SSL/TLS handshake. It copies as many |
26 | bytes as it can of this value into the buffer provided in B<out>, | |
27 | which must have at least B<outlen> bytes available. It returns the | |
d9f1c639 MC |
28 | total number of bytes that were actually copied. If B<outlen> is |
29 | zero, SSL_get_client_random() copies nothing, and returns the | |
7470cefc | 30 | total size of the client_random value. |
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31 | |
32 | SSL_get_server_random() behaves the same, but extracts the random value | |
33 | sent from the server to the client during the initial SSL/TLS handshake. | |
34 | ||
35 | SSL_SESSION_get_master_key() behaves the same, but extracts the master | |
36 | secret used to guarantee the security of the SSL/TLS session. This one | |
37 | can be dangerous if misused; see NOTES below. | |
38 | ||
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39 | SSL_SESSION_set1_master_key() sets the master key value associated with the |
40 | SSL_SESSION B<sess>. For example, this could be used to set up a session based | |
41 | PSK (see L<SSL_CTX_set_psk_use_session_callback(3)>). The master key of length | |
72257204 MC |
42 | B<len> should be provided at B<in>. The supplied master key is copied by the |
43 | function, so the caller is responsible for freeing and cleaning any memory | |
44 | associated with B<in>. The caller must ensure that the length of the key is | |
45 | suitable for the ciphersuite associated with the SSL_SESSION. | |
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46 | |
47 | =head1 NOTES | |
48 | ||
49 | You probably shouldn't use these functions. | |
50 | ||
51 | These functions expose internal values from the TLS handshake, for | |
52 | use in low-level protocols. You probably should not use them, unless | |
53 | you are implementing something that needs access to the internal protocol | |
54 | details. | |
55 | ||
56 | Despite the names of SSL_get_client_random() and SSL_get_server_random(), they | |
57 | ARE NOT random number generators. Instead, they return the mostly-random values that | |
24c2cd39 | 58 | were already generated and used in the TLS protocol. Using them |
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59 | in place of RAND_bytes() would be grossly foolish. |
60 | ||
61 | The security of your TLS session depends on keeping the master key secret: | |
62 | do not expose it, or any information about it, to anybody. | |
63 | If you need to calculate another secret value that depends on the master | |
64 | secret, you should probably use SSL_export_keying_material() instead, and | |
65 | forget that you ever saw these functions. | |
66 | ||
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67 | In current versions of the TLS protocols, the length of client_random |
68 | (and also server_random) is always SSL3_RANDOM_SIZE bytes. Support for | |
69 | other outlen arguments to the SSL_get_*_random() functions is provided | |
70 | in case of the unlikely event that a future version or variant of TLS | |
71 | uses some other length there. | |
72 | ||
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73 | Finally, though the "client_random" and "server_random" values are called |
74 | "random", many TLS implementations will generate four bytes of those | |
75 | values based on their view of the current time. | |
76 | ||
77 | ||
78 | =head1 RETURN VALUES | |
79 | ||
5eb72736 | 80 | SSL_SESSION_set1_master_key() returns 1 on success or 0 on failure. |
858618e7 | 81 | |
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82 | For the other functions, if B<outlen> is greater than 0 then these functions |
83 | return the number of bytes actually copied, which will be less than or equal to | |
84 | B<outlen>. If B<outlen> is 0 then these functions return the maximum number | |
85 | of bytes they would copy -- that is, the length of the underlying field. | |
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86 | |
87 | =head1 SEE ALSO | |
88 | ||
b97fdb57 | 89 | L<ssl(7)>, |
9b86974e | 90 | L<RAND_bytes(3)>, |
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91 | L<SSL_export_keying_material(3)>, |
92 | L<SSL_CTX_set_psk_use_session_callback(3)> | |
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93 | |
94 | ||
e2f92610 RS |
95 | =head1 COPYRIGHT |
96 | ||
5eb72736 | 97 | Copyright 2015-2017 The OpenSSL Project Authors. All Rights Reserved. |
e2f92610 | 98 | |
4746f25a | 99 | Licensed under the Apache License 2.0 (the "License"). You may not use |
e2f92610 RS |
100 | this file except in compliance with the License. You can obtain a copy |
101 | in the file LICENSE in the source distribution or at | |
102 | L<https://www.openssl.org/source/license.html>. | |
103 | ||
858618e7 | 104 | =cut |