| 1 | =pod
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| 2 |
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| 3 | =head1 NAME
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| 4 |
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| 5 | SSL_CTX_set1_groups, SSL_CTX_set1_groups_list, SSL_set1_groups,
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| 6 | SSL_set1_groups_list, SSL_get1_groups, SSL_get_shared_group,
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| 7 | SSL_get_negotiated_group, SSL_CTX_set1_curves, SSL_CTX_set1_curves_list,
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| 8 | SSL_set1_curves, SSL_set1_curves_list, SSL_get1_curves, SSL_get_shared_curve
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| 9 | - EC supported curve functions
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| 10 |
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| 11 | =head1 SYNOPSIS
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| 12 |
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| 13 | #include <openssl/ssl.h>
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| 14 |
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| 15 | int SSL_CTX_set1_groups(SSL_CTX *ctx, int *glist, int glistlen);
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| 16 | int SSL_CTX_set1_groups_list(SSL_CTX *ctx, char *list);
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| 17 |
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| 18 | int SSL_set1_groups(SSL *ssl, int *glist, int glistlen);
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| 19 | int SSL_set1_groups_list(SSL *ssl, char *list);
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| 20 |
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| 21 | int SSL_get1_groups(SSL *ssl, int *groups);
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| 22 | int SSL_get_shared_group(SSL *s, int n);
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| 23 | int SSL_get_negotiated_group(SSL *s);
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| 24 |
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| 25 | int SSL_CTX_set1_curves(SSL_CTX *ctx, int *clist, int clistlen);
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| 26 | int SSL_CTX_set1_curves_list(SSL_CTX *ctx, char *list);
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| 27 |
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| 28 | int SSL_set1_curves(SSL *ssl, int *clist, int clistlen);
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| 29 | int SSL_set1_curves_list(SSL *ssl, char *list);
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| 30 |
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| 31 | int SSL_get1_curves(SSL *ssl, int *curves);
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| 32 | int SSL_get_shared_curve(SSL *s, int n);
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| 33 |
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| 34 | =head1 DESCRIPTION
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| 35 |
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| 36 | For all of the functions below that set the supported groups there must be at
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| 37 | least one group in the list. A number of these functions identify groups via a
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| 38 | unique integer NID value. However, support for some groups may be added by
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| 39 | external providers. In this case there will be no NID assigned for the group.
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| 40 | When setting such groups applications should use the "list" form of these
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| 41 | functions (i.e. SSL_CTX_set1_groups_list() and SSL_set1_groups_list).
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| 42 |
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| 43 | SSL_CTX_set1_groups() sets the supported groups for B<ctx> to B<glistlen>
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| 44 | groups in the array B<glist>. The array consist of all NIDs of groups in
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| 45 | preference order. For a TLS client the groups are used directly in the
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| 46 | supported groups extension. For a TLS server the groups are used to
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| 47 | determine the set of shared groups. Currently supported groups for
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| 48 | B<TLSv1.3> are B<NID_X9_62_prime256v1>, B<NID_secp384r1>, B<NID_secp521r1>,
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| 49 | B<NID_X25519>, B<NID_X448>, B<NID_ffdhe2048>, B<NID_ffdhe3072>,
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| 50 | B<NID_ffdhe4096>, B<NID_ffdhe6144> and B<NID_ffdhe8192>.
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| 51 |
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| 52 | SSL_CTX_set1_groups_list() sets the supported groups for B<ctx> to
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| 53 | string B<list>. The string is a colon separated list of group NIDs or
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| 54 | names, for example "P-521:P-384:P-256:X25519:ffdhe2048". Currently supported
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| 55 | groups for B<TLSv1.3> are B<P-256>, B<P-384>, B<P-521>, B<X25519>, B<X448>,
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| 56 | B<ffdhe2048>, B<ffdhe3072>, B<ffdhe4096>, B<ffdhe6144>, B<ffdhe8192>. Support
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| 57 | for other groups may be added by external providers.
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| 58 |
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| 59 | SSL_set1_groups() and SSL_set1_groups_list() are similar except they set
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| 60 | supported groups for the SSL structure B<ssl>.
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| 61 |
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| 62 | SSL_get1_groups() returns the set of supported groups sent by a client
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| 63 | in the supported groups extension. It returns the total number of
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| 64 | supported groups. The B<groups> parameter can be B<NULL> to simply
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| 65 | return the number of groups for memory allocation purposes. The
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| 66 | B<groups> array is in the form of a set of group NIDs in preference
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| 67 | order. It can return zero if the client did not send a supported groups
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| 68 | extension. If a supported group NID is unknown then the value is set to the
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| 69 | bitwise OR of TLSEXT_nid_unknown (0x1000000) and the id of the group.
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| 70 |
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| 71 | SSL_get_shared_group() returns the NID of the shared group B<n> for a
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| 72 | server-side SSL B<ssl>. If B<n> is -1 then the total number of shared groups is
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| 73 | returned, which may be zero. Other than for diagnostic purposes,
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| 74 | most applications will only be interested in the first shared group
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| 75 | so B<n> is normally set to zero. If the value B<n> is out of range,
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| 76 | NID_undef is returned. If the NID for the shared group is unknown then the value
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| 77 | is set to the bitwise OR of TLSEXT_nid_unknown (0x1000000) and the id of the
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| 78 | group.
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| 79 |
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| 80 | SSL_get_negotiated_group() returns the NID of the negotiated group used for
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| 81 | the handshake key exchange process. For TLSv1.3 connections this typically
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| 82 | reflects the state of the current connection, though in the case of PSK-only
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| 83 | resumption, the returned value will be from a previous connection. For earlier
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| 84 | TLS versions, when a session has been resumed, it always reflects the group
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| 85 | used for key exchange during the initial handshake (otherwise it is from the
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| 86 | current, non-resumption, connection). This can be called by either client or
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| 87 | server. If the NID for the shared group is unknown then the value is set to the
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| 88 | bitwise OR of TLSEXT_nid_unknown (0x1000000) and the id of the group.
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| 89 |
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| 90 | All these functions are implemented as macros.
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| 91 |
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| 92 | The curve functions are synonyms for the equivalently named group functions and
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| 93 | are identical in every respect. They exist because, prior to TLS1.3, there was
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| 94 | only the concept of supported curves. In TLS1.3 this was renamed to supported
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| 95 | groups, and extended to include Diffie Hellman groups. The group functions
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| 96 | should be used in preference.
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| 97 |
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| 98 | =head1 NOTES
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| 99 |
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| 100 | If an application wishes to make use of several of these functions for
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| 101 | configuration purposes either on a command line or in a file it should
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| 102 | consider using the SSL_CONF interface instead of manually parsing options.
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| 103 |
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| 104 | =head1 RETURN VALUES
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| 105 |
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| 106 | SSL_CTX_set1_groups(), SSL_CTX_set1_groups_list(), SSL_set1_groups() and
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| 107 | SSL_set1_groups_list(), return 1 for success and 0 for failure.
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| 108 |
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| 109 | SSL_get1_groups() returns the number of groups, which may be zero.
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| 110 |
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| 111 | SSL_get_shared_group() returns the NID of shared group B<n> or NID_undef if there
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| 112 | is no shared group B<n>; or the total number of shared groups if B<n>
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| 113 | is -1.
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| 114 |
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| 115 | When called on a client B<ssl>, SSL_get_shared_group() has no meaning and
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| 116 | returns -1.
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| 117 |
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| 118 | SSL_get_negotiated_group() returns the NID of the negotiated group used for
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| 119 | key exchange, or NID_undef if there was no negotiated group.
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| 120 |
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| 121 | =head1 SEE ALSO
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| 122 |
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| 123 | L<ssl(7)>,
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| 124 | L<SSL_CTX_add_extra_chain_cert(3)>
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| 125 |
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| 126 | =head1 HISTORY
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| 127 |
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| 128 | The curve functions were added in OpenSSL 1.0.2. The equivalent group
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| 129 | functions were added in OpenSSL 1.1.1. The SSL_get_negotiated_group() function
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| 130 | was added in OpenSSL 3.0.0.
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| 131 |
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| 132 | =head1 COPYRIGHT
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| 133 |
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| 134 | Copyright 2013-2021 The OpenSSL Project Authors. All Rights Reserved.
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| 135 |
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| 136 | Licensed under the Apache License 2.0 (the "License"). You may not use
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| 137 | this file except in compliance with the License. You can obtain a copy
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| 138 | in the file LICENSE in the source distribution or at
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| 139 | L<https://www.openssl.org/source/license.html>.
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| 140 |
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| 141 | =cut
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