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.\" ========================================================================
.\"
.IX Title "SSL_CTX_SET_CIPHER_LIST 3"
.TH SSL_CTX_SET_CIPHER_LIST 3 "2023-09-11" "1.1.1w" "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_cipher_list, SSL_set_cipher_list, SSL_CTX_set_ciphersuites, SSL_set_ciphersuites \&\- choose list of available SSL_CIPHERs
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/ssl.h>
\&
\& int SSL_CTX_set_cipher_list(SSL_CTX *ctx, const char *str);
\& int SSL_set_cipher_list(SSL *ssl, const char *str);
\&
\& int SSL_CTX_set_ciphersuites(SSL_CTX *ctx, const char *str);
\& int SSL_set_ciphersuites(SSL *s, const char *str);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fISSL_CTX_set_cipher_list()\fR sets the list of available ciphers (TLSv1.2 and below)
for \fBctx\fR using the control string \fBstr\fR. The format of the string is described
in \fIciphers\fR\|(1). The list of ciphers is inherited by all
\&\fBssl\fR objects created from \fBctx\fR. This function does not impact TLSv1.3
ciphersuites. Use \fISSL_CTX_set_ciphersuites()\fR to configure those.
.PP
\&\fISSL_set_cipher_list()\fR sets the list of ciphers (TLSv1.2 and below) only for
\&\fBssl\fR.
.PP
\&\fISSL_CTX_set_ciphersuites()\fR is used to configure the available TLSv1.3
ciphersuites for \fBctx\fR. This is a simple colon (\*(L":\*(R") separated list of TLSv1.3
ciphersuite names in order of preference. Valid TLSv1.3 ciphersuite names are:
.IP "\s-1TLS_AES_128_GCM_SHA256\s0" 4
.IX Item "TLS_AES_128_GCM_SHA256"
.PD 0
.IP "\s-1TLS_AES_256_GCM_SHA384\s0" 4
.IX Item "TLS_AES_256_GCM_SHA384"
.IP "\s-1TLS_CHACHA20_POLY1305_SHA256\s0" 4
.IX Item "TLS_CHACHA20_POLY1305_SHA256"
.IP "\s-1TLS_AES_128_CCM_SHA256\s0" 4
.IX Item "TLS_AES_128_CCM_SHA256"
.IP "\s-1TLS_AES_128_CCM_8_SHA256\s0" 4
.IX Item "TLS_AES_128_CCM_8_SHA256"
.PD
.PP
An empty list is permissible. The default value for the this setting is:
.PP
\&\*(L"\s-1TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256\*(R"\s0
.PP
\&\fISSL_set_ciphersuites()\fR is the same as \fISSL_CTX_set_ciphersuites()\fR except it
configures the ciphersuites for \fBssl\fR.
.SH "NOTES"
.IX Header "NOTES"
The control string \fBstr\fR for \fISSL_CTX_set_cipher_list()\fR and
\&\fISSL_set_cipher_list()\fR should be universally usable and not depend
on details of the library configuration (ciphers compiled in). Thus no
syntax checking takes place. Items that are not recognized, because the
corresponding ciphers are not compiled in or because they are mistyped,
are simply ignored. Failure is only flagged if no ciphers could be collected
at all.
.PP
It should be noted, that inclusion of a cipher to be used into the list is
a necessary condition. On the client side, the inclusion into the list is
also sufficient unless the security level excludes it. On the server side,
additional restrictions apply. All ciphers have additional requirements.
\&\s-1ADH\s0 ciphers don't need a certificate, but DH-parameters must have been set.
All other ciphers need a corresponding certificate and key.
.PP
A \s-1RSA\s0 cipher can only be chosen, when a \s-1RSA\s0 certificate is available.
\&\s-1RSA\s0 ciphers using \s-1DHE\s0 need a certificate and key and additional DH-parameters
(see \fISSL_CTX_set_tmp_dh_callback\fR\|(3)).
.PP
A \s-1DSA\s0 cipher can only be chosen, when a \s-1DSA\s0 certificate is available.
\&\s-1DSA\s0 ciphers always use \s-1DH\s0 key exchange and therefore need DH-parameters
(see \fISSL_CTX_set_tmp_dh_callback\fR\|(3)).
.PP
When these conditions are not met for any cipher in the list (e.g. a
client only supports export \s-1RSA\s0 ciphers with an asymmetric key length
of 512 bits and the server is not configured to use temporary \s-1RSA\s0
keys), the \*(L"no shared cipher\*(R" (\s-1SSL_R_NO_SHARED_CIPHER\s0) error is generated
and the handshake will fail.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fISSL_CTX_set_cipher_list()\fR and \fISSL_set_cipher_list()\fR return 1 if any cipher
could be selected and 0 on complete failure.
.PP
\&\fISSL_CTX_set_ciphersuites()\fR and \fISSL_set_ciphersuites()\fR return 1 if the requested
ciphersuite list was configured, and 0 otherwise.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fIssl\fR\|(7), \fISSL_get_ciphers\fR\|(3),
\&\fISSL_CTX_use_certificate\fR\|(3),
\&\fISSL_CTX_set_tmp_dh_callback\fR\|(3),
\&\fIciphers\fR\|(1)
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2000\-2019 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the OpenSSL license (the \*(L"License\*(R").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file \s-1LICENSE\s0 in the source distribution or at
<https://www.openssl.org/source/license.html>.