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Diffstat (limited to 'static/freebsd/man3/SSL_CTX_set_tmp_dh_callback.3')
| -rw-r--r-- | static/freebsd/man3/SSL_CTX_set_tmp_dh_callback.3 | 183 |
1 files changed, 183 insertions, 0 deletions
diff --git a/static/freebsd/man3/SSL_CTX_set_tmp_dh_callback.3 b/static/freebsd/man3/SSL_CTX_set_tmp_dh_callback.3 new file mode 100644 index 00000000..fd7a7423 --- /dev/null +++ b/static/freebsd/man3/SSL_CTX_set_tmp_dh_callback.3 @@ -0,0 +1,183 @@ +.\" -*- mode: troff; coding: utf-8 -*- +.\" Automatically generated by Pod::Man v6.0.2 (Pod::Simple 3.45) +.\" +.\" Standard preamble: +.\" ======================================================================== +.de Sp \" Vertical space (when we can't use .PP) +.if t .sp .5v +.if n .sp +.. +.de Vb \" Begin verbatim text +.ft CW +.nf +.ne \\$1 +.. +.de Ve \" End verbatim text +.ft R +.fi +.. +.\" \*(C` and \*(C' are quotes in nroff, nothing in troff, for use with C<>. +.ie n \{\ +. ds C` "" +. ds C' "" +'br\} +.el\{\ +. ds C` +. ds C' +'br\} +.\" +.\" Escape single quotes in literal strings from groff's Unicode transform. +.ie \n(.g .ds Aq \(aq +.el .ds Aq ' +.\" +.\" If the F register is >0, we'll generate index entries on stderr for +.\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index +.\" entries marked with X<> in POD. Of course, you'll have to process the +.\" output yourself in some meaningful fashion. +.\" +.\" Avoid warning from groff about undefined register 'F'. +.de IX +.. +.nr rF 0 +.if \n(.g .if rF .nr rF 1 +.if (\n(rF:(\n(.g==0)) \{\ +. if \nF \{\ +. de IX +. tm Index:\\$1\t\\n%\t"\\$2" +.. +. if !\nF==2 \{\ +. nr % 0 +. nr F 2 +. \} +. \} +.\} +.rr rF +.\" +.\" Required to disable full justification in groff 1.23.0. +.if n .ds AD l +.\" ======================================================================== +.\" +.IX Title "SSL_CTX_SET_TMP_DH_CALLBACK 3ossl" +.TH SSL_CTX_SET_TMP_DH_CALLBACK 3ossl 2026-04-07 3.5.6 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 +SSL_CTX_set_dh_auto, SSL_set_dh_auto, SSL_CTX_set0_tmp_dh_pkey, +SSL_set0_tmp_dh_pkey, SSL_CTX_set_tmp_dh_callback, SSL_CTX_set_tmp_dh, +SSL_set_tmp_dh_callback, SSL_set_tmp_dh +\&\- handle DH keys for ephemeral key exchange +.SH SYNOPSIS +.IX Header "SYNOPSIS" +.Vb 1 +\& #include <openssl/ssl.h> +\& +\& long SSL_CTX_set_dh_auto(SSL_CTX *ctx, int onoff); +\& long SSL_set_dh_auto(SSL *s, int onoff); +\& int SSL_CTX_set0_tmp_dh_pkey(SSL_CTX *ctx, EVP_PKEY *dhpkey); +\& int SSL_set0_tmp_dh_pkey(SSL *s, EVP_PKEY *dhpkey); +.Ve +.PP +The following functions have been deprecated since OpenSSL 3.0, and can be +hidden entirely by defining \fBOPENSSL_API_COMPAT\fR with a suitable version value, +see \fBopenssl_user_macros\fR\|(7): +.PP +.Vb 4 +\& void SSL_CTX_set_tmp_dh_callback(SSL_CTX *ctx, +\& DH *(*tmp_dh_callback)(SSL *ssl, int is_export, +\& int keylength)); +\& long SSL_CTX_set_tmp_dh(SSL_CTX *ctx, DH *dh); +\& +\& void SSL_set_tmp_dh_callback(SSL *ctx, +\& DH *(*tmp_dh_callback)(SSL *ssl, int is_export, +\& int keylength)); +\& long SSL_set_tmp_dh(SSL *ssl, DH *dh); +.Ve +.SH DESCRIPTION +.IX Header "DESCRIPTION" +The functions described on this page are relevant for servers only. +.PP +Some ciphersuites may use ephemeral Diffie\-Hellman (DH) key exchange. In these +cases, the session data is negotiated using the ephemeral/temporary DH key and +the key supplied and certified by the certificate chain is only used for +signing. Anonymous ciphers (without a permanent server key) also use ephemeral +DH keys. +.PP +Using ephemeral DH key exchange yields forward secrecy as the connection +can only be decrypted when the DH key is known. By generating a temporary +DH key inside the server application that is lost when the application +is left, it becomes impossible for an attacker to decrypt past sessions, +even if they get hold of the normal (certified) key, as this key was +only used for signing. +.PP +In order to perform a DH key exchange the server must use a DH group +(DH parameters) and generate a DH key. The server will always generate +a new DH key during the negotiation. +.PP +As generating DH parameters is extremely time consuming, an application +should not generate the parameters on the fly. DH parameters can be reused, as +the actual key is newly generated during the negotiation. +.PP +Typically applications should use well known DH parameters that have built\-in +support in OpenSSL. The macros \fBSSL_CTX_set_dh_auto()\fR and \fBSSL_set_dh_auto()\fR +configure OpenSSL to use the default built\-in DH parameters for the \fBSSL_CTX\fR +and \fBSSL\fR objects respectively. Passing a value of 2 or 1 in the \fIonoff\fR +parameter switches it on. If the \fIonoff\fR parameter is set to 2, it will force +the DH key size to 1024 if the \fBSSL_CTX\fR or \fBSSL\fR security level +\&\fBSSL_CTX_set_security_level\fR\|(3) is 0 or 1. Passing a value of 0 switches +it off. The default setting is off. +.PP +If "auto" DH parameters are switched on then the parameters will be selected to +be consistent with the size of the key associated with the server\*(Aqs certificate. +If there is no certificate (e.g. for PSK ciphersuites), then it it will be +consistent with the size of the negotiated symmetric cipher key. +.PP +Applications may supply their own DH parameters instead of using the built\-in +values. This approach is discouraged and applications should in preference use +the built\-in parameter support described above. Applications wishing to supply +their own DH parameters should call \fBSSL_CTX_set0_tmp_dh_pkey()\fR or +\&\fBSSL_set0_tmp_dh_pkey()\fR to supply the parameters for the \fBSSL_CTX\fR or \fBSSL\fR +respectively. The parameters should be supplied in the \fIdhpkey\fR argument as +an \fBEVP_PKEY\fR containing DH parameters. Ownership of the \fIdhpkey\fR value is +passed to the \fBSSL_CTX\fR or \fBSSL\fR object as a result of this call, and so the +caller should not free it if the function call is successful. +.PP +The deprecated macros \fBSSL_CTX_set_tmp_dh()\fR and \fBSSL_set_tmp_dh()\fR do the same +thing as \fBSSL_CTX_set0_tmp_dh_pkey()\fR and \fBSSL_set0_tmp_dh_pkey()\fR except that the +DH parameters are supplied in a \fBDH\fR object instead in the \fIdh\fR argument, and +ownership of the \fBDH\fR object is retained by the application. Applications +should use "auto" parameters instead, or call \fBSSL_CTX_set0_tmp_dh_pkey()\fR or +\&\fBSSL_set0_tmp_dh_pkey()\fR as appropriate. +.PP +An application may instead specify the DH parameters via a callback function +using the functions \fBSSL_CTX_set_tmp_dh_callback()\fR or \fBSSL_set_tmp_dh_callback()\fR +to set the callback for the \fBSSL_CTX\fR or \fBSSL\fR object respectively. These +functions are deprecated. Applications should instead use "auto" parameters, or +specify the parameters via \fBSSL_CTX_set0_tmp_dh_pkey()\fR or \fBSSL_set0_tmp_dh_pkey()\fR +as appropriate. +.PP +The callback will be invoked during a connection when DH parameters are +required. The \fBSSL\fR object for the current connection is supplied as an +argument. Previous versions of OpenSSL used the \fBis_export\fR and \fBkeylength\fR +arguments to control parameter generation for export and non\-export +cipher suites. Modern OpenSSL does not support export ciphersuites and so these +arguments are unused and can be ignored by the callback. The callback should +return the parameters to be used in a DH object. Ownership of the DH object is +retained by the application and should later be freed. +.SH "RETURN VALUES" +.IX Header "RETURN VALUES" +All of these functions/macros return 1 for success or 0 on error. +.SH "SEE ALSO" +.IX Header "SEE ALSO" +\&\fBssl\fR\|(7), \fBSSL_CTX_set_cipher_list\fR\|(3), +\&\fBSSL_CTX_set_options\fR\|(3), +\&\fBopenssl\-ciphers\fR\|(1), \fBopenssl\-dhparam\fR\|(1) +.SH COPYRIGHT +.IX Header "COPYRIGHT" +Copyright 2001\-2025 The OpenSSL Project Authors. All Rights Reserved. +.PP +Licensed under the Apache License 2.0 (the "License"). You may not use +this file except in compliance with the License. You can obtain a copy +in the file LICENSE in the source distribution or at +<https://www.openssl.org/source/license.html>. |