Provided by: libssl-doc_1.1.1f-1ubuntu2.24_all bug

NAME

       SSL_CONF_cmd_value_type, SSL_CONF_cmd - send configuration command

SYNOPSIS

        #include <openssl/ssl.h>

        int SSL_CONF_cmd(SSL_CONF_CTX *cctx, const char *cmd, const char *value);
        int SSL_CONF_cmd_value_type(SSL_CONF_CTX *cctx, const char *cmd);

DESCRIPTION

       The function SSL_CONF_cmd() performs configuration operation cmd with optional parameter value on ctx.
       Its purpose is to simplify application configuration of SSL_CTX or SSL structures by providing a common
       framework for command line options or configuration files.

       SSL_CONF_cmd_value_type() returns the type of value that cmd refers to.

SUPPORTED COMMAND LINE COMMANDS

       Currently supported cmd names for command lines (i.e. when the flag SSL_CONF_CMDLINE is set) are listed
       below. Note: all cmd names are case sensitive. Unless otherwise stated commands can be used by both
       clients and servers and the value parameter is not used. The default prefix for command line commands is
       - and that is reflected below.

       -sigalgs
           This sets the supported signature algorithms for TLSv1.2 and TLSv1.3.  For clients this value is used
           directly  for the supported signature algorithms extension. For servers it is used to determine which
           signature algorithms to support.

           The value argument should be a colon separated list of signature algorithms in  order  of  decreasing
           preference  of the form algorithm+hash or signature_scheme. algorithm is one of RSA, DSA or ECDSA and
           hash is a supported algorithm OID short name such as SHA1, SHA224, SHA256, SHA384 of  SHA512.   Note:
           algorithm  and  hash  names  are  case  sensitive.   signature_scheme is one of the signature schemes
           defined in TLSv1.3,  specified  using  the  IETF  name,  e.g.,  ecdsa_secp256r1_sha256,  ed25519,  or
           rsa_pss_pss_sha256.

           If  this  option  is  not  set  then  all  signature  algorithms supported by the OpenSSL library are
           permissible.

           Note: algorithms which specify a PKCS#1 v1.5 signature scheme (either by using RSA as  the  algorithm
           or by using one of the rsa_pkcs1_* identifiers) are ignored in TLSv1.3 and will not be negotiated.

       -client_sigalgs
           This  sets  the  supported signature algorithms associated with client authentication for TLSv1.2 and
           TLSv1.3.  For servers the value is used in the signature_algorithms  field  of  a  CertificateRequest
           message.   For  clients  it  is  used  to  determine which signature algorithm to use with the client
           certificate.  If a server does not request a certificate this option has no effect.

           The syntax of value is identical to -sigalgs. If not set then the value set for -sigalgs will be used
           instead.

       -groups
           This sets the supported groups.  For  clients,  the  groups  are  sent  using  the  supported  groups
           extension.  For servers, it is used to determine which group to use. This setting affects groups used
           for signatures (in TLSv1.2 and earlier) and key exchange. The first group listed will  also  be  used
           for the key_share sent by a client in a TLSv1.3 ClientHello.

           The  value  argument is a colon separated list of groups. The group can be either the NIST name (e.g.
           P-256), some other commonly used name where applicable (e.g. X25519) or  an  OpenSSL  OID  name  (e.g
           prime256v1).  Group names are case sensitive. The list should be in order of preference with the most
           preferred group first.

       -curves
           This is a synonym for the "-groups" command.

       -named_curve
           This sets the temporary curve used for ephemeral ECDH modes. Only used by servers

           The value argument is a curve name or the special value auto which picks an appropriate  curve  based
           on  client  and  server preferences. The curve can be either the NIST name (e.g. P-256) or an OpenSSL
           OID name (e.g prime256v1). Curve names are case sensitive.

       -cipher
           Sets the TLSv1.2 and below ciphersuite list to value. This list will be combined with any  configured
           TLSv1.3  ciphersuites.  Note:  syntax  checking  of  value is currently not performed unless a SSL or
           SSL_CTX structure is associated with cctx.

       -ciphersuites
           Sets the available ciphersuites for TLSv1.3 to value. This is a simple colon (":") separated list  of
           TLSv1.3  ciphersuite  names in order of preference. This list will be combined any configured TLSv1.2
           and below ciphersuites.  See ciphers(1) for more information.

       -cert
           Attempts to use the file value as the certificate for the  appropriate  context.  It  currently  uses
           SSL_CTX_use_certificate_chain_file()  if  an  SSL_CTX  structure is set or SSL_use_certificate_file()
           with filetype PEM if an SSL structure is set. This option is only supported if certificate operations
           are permitted.

       -key
           Attempts to use the file value as the private key for the appropriate context. This  option  is  only
           supported  if certificate operations are permitted. Note: if no -key option is set then a private key
           is not loaded unless the flag SSL_CONF_FLAG_REQUIRE_PRIVATE is set.

       -dhparam
           Attempts to use the file value as the set of temporary DH parameters  for  the  appropriate  context.
           This option is only supported if certificate operations are permitted.

       -record_padding
           Attempts  to pad TLSv1.3 records so that they are a multiple of value in length on send. A value of 0
           or 1 turns off padding. Otherwise, the value must be >1 or <=16384.

       -no_renegotiation
           Disables   all   attempts   at   renegotiation   in   TLSv1.2   and   earlier,   same   as    setting
           SSL_OP_NO_RENEGOTIATION.

       -min_protocol, -max_protocol
           Sets  the  minimum  and  maximum  supported protocol.  Currently supported protocol values are SSLv3,
           TLSv1, TLSv1.1, TLSv1.2, TLSv1.3 for TLS and DTLSv1, DTLSv1.2 for DTLS, and None for  no  limit.   If
           either  bound  is  not  specified  then  only the other bound applies, if specified.  To restrict the
           supported protocol versions use these commands rather than the deprecated alternative commands below.

       -no_ssl3, -no_tls1, -no_tls1_1, -no_tls1_2, -no_tls1_3
           Disables  protocol  support  for  SSLv3,  TLSv1.0,  TLSv1.1,  TLSv1.2  or  TLSv1.3  by  setting   the
           corresponding  options  SSL_OP_NO_SSLv3,  SSL_OP_NO_TLSv1,  SSL_OP_NO_TLSv1_1,  SSL_OP_NO_TLSv1_2 and
           SSL_OP_NO_TLSv1_3  respectively.  These  options  are  deprecated,  instead  use  -min_protocol   and
           -max_protocol.

       -bugs
           Various bug workarounds are set, same as setting SSL_OP_ALL.

       -comp
           Enables  support  for  SSL/TLS compression, same as clearing SSL_OP_NO_COMPRESSION.  This command was
           introduced in OpenSSL 1.1.0.  As of OpenSSL 1.1.0, compression is off by default.

       -no_comp
           Disables support for SSL/TLS compression, same  as  setting  SSL_OP_NO_COMPRESSION.   As  of  OpenSSL
           1.1.0, compression is off by default.

       -no_ticket
           Disables support for session tickets, same as setting SSL_OP_NO_TICKET.

       -serverpref
           Use  server  and not client preference order when determining which cipher suite, signature algorithm
           or elliptic curve to use for an incoming connection.  Equivalent to  SSL_OP_CIPHER_SERVER_PREFERENCE.
           Only used by servers.

       -prioritize_chacha
           Prioritize  ChaCha  ciphers  when the client has a ChaCha20 cipher at the top of its preference list.
           This usually indicates a client without AES hardware acceleration (e.g. mobile) is in use. Equivalent
           to SSL_OP_PRIORITIZE_CHACHA.  Only used by servers. Requires -serverpref.

       -no_resumption_on_reneg
           set SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION flag. Only used by servers.

       -legacyrenegotiation
           permits    the    use    of    unsafe     legacy     renegotiation.     Equivalent     to     setting
           SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION.

       -legacy_server_connect, -no_legacy_server_connect
           permits  or  prohibits the use of unsafe legacy renegotiation for OpenSSL clients only. Equivalent to
           setting or clearing SSL_OP_LEGACY_SERVER_CONNECT.  Set by default.

       -allow_no_dhe_kex
           In TLSv1.3 allow a non-(ec)dhe based key exchange mode on resumption. This means that there  will  be
           no forward secrecy for the resumed session.

       -strict
           enables strict mode protocol handling. Equivalent to setting SSL_CERT_FLAG_TLS_STRICT.

       -anti_replay, -no_anti_replay
           Switches  replay  protection,  on  or  off  respectively.  With  replay  protection  on, OpenSSL will
           automatically detect if a session ticket has been used more than once, TLSv1.3 has  been  negotiated,
           and  early  data  is  enabled on the server. A full handshake is forced if a session ticket is used a
           second or subsequent time. Anti-Replay is on by default unless overridden by a configuration file and
           is only used  by  servers.  Anti-replay  measures  are  required  for  compliance  with  the  TLSv1.3
           specification.  Some  applications may be able to mitigate the replay risks in other ways and in such
           cases the built-in OpenSSL functionality is not required. Switching off anti-replay is equivalent  to
           SSL_OP_NO_ANTI_REPLAY.

SUPPORTED CONFIGURATION FILE COMMANDS

       Currently  supported cmd names for configuration files (i.e. when the flag SSL_CONF_FLAG_FILE is set) are
       listed below. All configuration file cmd names are case insensitive so signaturealgorithms is  recognised
       as well as SignatureAlgorithms. Unless otherwise stated the value names are also case insensitive.

       Note: the command prefix (if set) alters the recognised cmd values.

       CipherString
           Sets  the  ciphersuite  list  for  TLSv1.2  and  below  to value. This list will be combined with any
           configured TLSv1.3 ciphersuites. Note: syntax checking of value is currently not performed unless  an
           SSL or SSL_CTX structure is associated with cctx.

       Ciphersuites
           Sets  the available ciphersuites for TLSv1.3 to value. This is a simple colon (":") separated list of
           TLSv1.3 ciphersuite names in order of preference. This list will be combined any  configured  TLSv1.2
           and below ciphersuites.  See ciphers(1) for more information.

       Certificate
           Attempts  to  use  the  file  value as the certificate for the appropriate context. It currently uses
           SSL_CTX_use_certificate_chain_file() if an SSL_CTX structure  is  set  or  SSL_use_certificate_file()
           with filetype PEM if an SSL structure is set. This option is only supported if certificate operations
           are permitted.

       PrivateKey
           Attempts  to  use  the file value as the private key for the appropriate context. This option is only
           supported if certificate operations are permitted. Note: if  no  PrivateKey  option  is  set  then  a
           private key is not loaded unless the SSL_CONF_FLAG_REQUIRE_PRIVATE is set.

       ChainCAFile, ChainCAPath, VerifyCAFile, VerifyCAPath
           These  options  indicate  a  file  or  directory  used  for  building certificate chains or verifying
           certificate chains. These options are only supported if certificate operations are permitted.

       RequestCAFile
           This option indicates a file containing a set of certificates in PEM form.  The subject names of  the
           certificates  are  sent  to  the  peer  in  the  certificate_authorities  extension  for  TLS 1.3 (in
           ClientHello or CertificateRequest) or in a certificate request for previous versions or TLS.

       ServerInfoFile
           Attempts  to  use   the   file   value   in   the   "serverinfo"   extension   using   the   function
           SSL_CTX_use_serverinfo_file.

       DHParameters
           Attempts  to  use  the  file value as the set of temporary DH parameters for the appropriate context.
           This option is only supported if certificate operations are permitted.

       RecordPadding
           Attempts to pad TLSv1.3 records so that they are a multiple of value in length on send. A value of  0
           or 1 turns off padding. Otherwise, the value must be >1 or <=16384.

       SignatureAlgorithms
           This sets the supported signature algorithms for TLSv1.2 and TLSv1.3.  For clients this value is used
           directly  for the supported signature algorithms extension. For servers it is used to determine which
           signature algorithms to support.

           The value argument should be a colon separated list of signature algorithms in  order  of  decreasing
           preference  of the form algorithm+hash or signature_scheme. algorithm is one of RSA, DSA or ECDSA and
           hash is a supported algorithm OID short name such as SHA1, SHA224, SHA256, SHA384 of  SHA512.   Note:
           algorithm  and  hash  names  are  case  sensitive.   signature_scheme is one of the signature schemes
           defined in TLSv1.3,  specified  using  the  IETF  name,  e.g.,  ecdsa_secp256r1_sha256,  ed25519,  or
           rsa_pss_pss_sha256.

           If  this  option  is  not  set  then  all  signature  algorithms supported by the OpenSSL library are
           permissible.

           Note: algorithms which specify a PKCS#1 v1.5 signature scheme (either by using RSA as  the  algorithm
           or by using one of the rsa_pkcs1_* identifiers) are ignored in TLSv1.3 and will not be negotiated.

       ClientSignatureAlgorithms
           This  sets  the  supported signature algorithms associated with client authentication for TLSv1.2 and
           TLSv1.3.  For servers the value is used in the signature_algorithms  field  of  a  CertificateRequest
           message.   For  clients  it  is  used  to  determine which signature algorithm to use with the client
           certificate.  If a server does not request a certificate this option has no effect.

           The syntax of value is  identical  to  SignatureAlgorithms.  If  not  set  then  the  value  set  for
           SignatureAlgorithms will be used instead.

       Groups
           This  sets  the  supported  groups.  For  clients,  the  groups  are  sent using the supported groups
           extension. For servers, it is used to determine which group to use. This setting affects groups  used
           for  signatures  (in  TLSv1.2 and earlier) and key exchange. The first group listed will also be used
           for the key_share sent by a client in a TLSv1.3 ClientHello.

           The value argument is a colon separated list of groups. The group can be either the NIST  name  (e.g.
           P-256),  some  other  commonly  used  name where applicable (e.g. X25519) or an OpenSSL OID name (e.g
           prime256v1). Group names are case sensitive. The list should be in order of preference with the  most
           preferred group first.

       Curves
           This is a synonym for the "Groups" command.

       MinProtocol
           This sets the minimum supported SSL, TLS or DTLS version.

           Currently supported protocol values are SSLv3, TLSv1, TLSv1.1, TLSv1.2, TLSv1.3, DTLSv1 and DTLSv1.2.
           The value None will disable the limit.

       MaxProtocol
           This sets the maximum supported SSL, TLS or DTLS version.

           Currently supported protocol values are SSLv3, TLSv1, TLSv1.1, TLSv1.2, TLSv1.3, DTLSv1 and DTLSv1.2.
           The value None will disable the limit.

       Protocol
           This can be used to enable or disable certain versions of the SSL, TLS or DTLS protocol.

           The  value  argument  is  a  comma  separated list of supported protocols to enable or disable.  If a
           protocol is preceded by - that version is disabled.

           All protocol versions are enabled by default.  You need to disable at least one protocol version  for
           this  setting  have  any  effect.   Only  enabling  some protocol versions does not disable the other
           protocol versions.

           Currently supported protocol values are SSLv3, TLSv1, TLSv1.1, TLSv1.2, TLSv1.3, DTLSv1 and DTLSv1.2.
           The special value ALL refers to all supported versions.

           This can't enable protocols that are disabled using  MinProtocol  or  MaxProtocol,  but  can  disable
           protocols that are still allowed by them.

           The  Protocol  command  is  fragile  and  deprecated; do not use it.  Use MinProtocol and MaxProtocol
           instead.  If you do use Protocol, make sure that the resulting range  of  enabled  protocols  has  no
           "holes", e.g. if TLS 1.0 and TLS 1.2 are both enabled, make sure to also leave TLS 1.1 enabled.

       Options
           The value argument is a comma separated list of various flags to set.  If a flag string is preceded -
           it is disabled.  See the SSL_CTX_set_options(3) function for more details of individual options.

           Each  option  is listed below. Where an operation is enabled by default the -flag syntax is needed to
           disable it.

           SessionTicket: session ticket support, enabled by  default.  Inverse  of  SSL_OP_NO_TICKET:  that  is
           -SessionTicket is the same as setting SSL_OP_NO_TICKET.

           Compression: SSL/TLS compression support, enabled by default. Inverse of SSL_OP_NO_COMPRESSION.

           EmptyFragments:  use  empty  fragments  as  a  countermeasure  against  a  SSL  3.0/TLS  1.0 protocol
           vulnerability    affecting    CBC    ciphers.    It    is    set    by    default.     Inverse     of
           SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS.

           Bugs: enable various bug workarounds. Same as SSL_OP_ALL.

           DHSingle:  enable  single  use  DH  keys,  set  by default. Inverse of SSL_OP_DH_SINGLE. Only used by
           servers.

           ECDHSingle: enable single use ECDH keys, set by default. Inverse of SSL_OP_ECDH_SINGLE. Only used  by
           servers.

           ServerPreference:  use  server  and  not client preference order when determining which cipher suite,
           signature  algorithm  or  elliptic  curve  to  use  for  an  incoming  connection.    Equivalent   to
           SSL_OP_CIPHER_SERVER_PREFERENCE. Only used by servers.

           PrioritizeChaCha:  prioritizes ChaCha ciphers when the client has a ChaCha20 cipher at the top of its
           preference  list.  This  usually   indicates   a   mobile   client   is   in   use.   Equivalent   to
           SSL_OP_PRIORITIZE_CHACHA.  Only used by servers.

           NoResumptionOnRenegotiation:  set  SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION  flag.  Only used by
           servers.

           NoRenegotiation: disables all attempts at renegotiation in  TLSv1.2  and  earlier,  same  as  setting
           SSL_OP_NO_RENEGOTIATION.

           UnsafeLegacyRenegotiation:   permits   the   use  of  unsafe  legacy  renegotiation.   Equivalent  to
           SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION.

           UnsafeLegacyServerConnect: permits the use of unsafe legacy renegotiation for OpenSSL  clients  only.
           Equivalent to SSL_OP_LEGACY_SERVER_CONNECT.  Set by default.

           EncryptThenMac:    use    encrypt-then-mac    extension,    enabled    by    default.    Inverse   of
           SSL_OP_NO_ENCRYPT_THEN_MAC:    that    is,    -EncryptThenMac    is    the    same     as     setting
           SSL_OP_NO_ENCRYPT_THEN_MAC.

           AllowNoDHEKEX:  In TLSv1.3 allow a non-(ec)dhe based key exchange mode on resumption. This means that
           there will be no forward secrecy for the resumed session. Equivalent to SSL_OP_ALLOW_NO_DHE_KEX.

           MiddleboxCompat: If set then dummy Change Cipher Spec (CCS) messages are sent in  TLSv1.3.  This  has
           the  effect  of  making  TLSv1.3  look  more  like TLSv1.2 so that middleboxes that do not understand
           TLSv1.3 will not drop the connection. This option is set by default. A future version of OpenSSL  may
           not set this by default. Equivalent to SSL_OP_ENABLE_MIDDLEBOX_COMPAT.

           AntiReplay: If set then OpenSSL will automatically detect if a session ticket has been used more than
           once,  TLSv1.3  has  been  negotiated,  and  early data is enabled on the server. A full handshake is
           forced if a session ticket is used a second or subsequent time. This option is set by default and  is
           only  used  by  servers.  Anti-replay measures are required to comply with the TLSv1.3 specification.
           Some applications may be able to mitigate the replay risks in other ways and in such cases the built-
           in  OpenSSL  functionality  is  not  required.   Disabling  anti-replay  is  equivalent  to   setting
           SSL_OP_NO_ANTI_REPLAY.

       VerifyMode
           The value argument is a comma separated list of flags to set.

           Peer enables peer verification: for clients only.

           Request requests but does not require a certificate from the client.  Servers only.

           Require  requests  and requires a certificate from the client: an error occurs if the client does not
           present a certificate. Servers only.

           Once requests a certificate from a client only on the initial  connection:  not  when  renegotiating.
           Servers only.

           RequestPostHandshake configures the connection to support requests but does not require a certificate
           from the client post-handshake. A certificate will not be requested during the initial handshake. The
           server  application  must  provide a mechanism to request a certificate post-handshake. Servers only.
           TLSv1.3 only.

           RequiresPostHandshake configures the connection to support requests and requires a  certificate  from
           the  client  post-handshake:  an  error  occurs  if  the  client  does  not  present a certificate. A
           certificate will not be requested during the initial handshake. The server application must provide a
           mechanism to request a certificate post-handshake. Servers only. TLSv1.3 only.

       ClientCAFile, ClientCAPath
           A file or directory of certificates in PEM format whose names are used as the set of acceptable names
           for client CAs. Servers only. This option is only supported if certificate operations are permitted.

SUPPORTED COMMAND TYPES

       The function SSL_CONF_cmd_value_type() currently returns one of the following types:

       SSL_CONF_TYPE_UNKNOWN
           The cmd string is unrecognised, this return value can be use to flag syntax errors.

       SSL_CONF_TYPE_STRING
           The value is a string without any specific structure.

       SSL_CONF_TYPE_FILE
           The value is a file name.

       SSL_CONF_TYPE_DIR
           The value is a directory name.

       SSL_CONF_TYPE_NONE
           The value string is not used e.g. a command line option which doesn't take an argument.

NOTES

       The order of operations is significant. This can be used to set either defaults or values which cannot be
       overridden. For example if an application calls:

        SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
        SSL_CONF_cmd(ctx, userparam, uservalue);

       it will disable SSLv3 support by default but the user can override it. If however the call sequence is:

        SSL_CONF_cmd(ctx, userparam, uservalue);
        SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");

       SSLv3 is always disabled and attempt to override this by the user are ignored.

       By checking the return code of SSL_CONF_cmd() it is possible to query if a given cmd is recognised,  this
       is useful if SSL_CONF_cmd() values are mixed with additional application specific operations.

       For example an application might call SSL_CONF_cmd() and if it returns -2 (unrecognised command) continue
       with processing of application specific commands.

       Applications  can  also  use  SSL_CONF_cmd()  to  process  command  lines  though  the  utility  function
       SSL_CONF_cmd_argv() is normally used instead. One way to do this is to set the prefix to  an  appropriate
       value  using  SSL_CONF_CTX_set1_prefix(),  pass the current argument to cmd and the following argument to
       value (which may be NULL).

       In this case if the return value is positive then it is used to skip that number  of  arguments  as  they
       have  been  processed  by  SSL_CONF_cmd().  If  -2 is returned then cmd is not recognised and application
       specific arguments can be checked instead. If -3 is returned a required argument is missing and an  error
       is indicated. If 0 is returned some other error occurred and this can be reported back to the user.

       The  function  SSL_CONF_cmd_value_type()  can  be  used  by  applications to check for the existence of a
       command or to perform additional syntax checking or translation of the command value. For example if  the
       return  value  is  SSL_CONF_TYPE_FILE  an  application could translate a relative pathname to an absolute
       pathname.

RETURN VALUES

       SSL_CONF_cmd() returns 1 if the value of cmd is recognised and value is NOT used and 2 if  both  cmd  and
       value  are  used.  In  other  words  it  returns  the  number of arguments processed. This is useful when
       processing command lines.

       A return value of -2 means cmd is not recognised.

       A return value of -3 means cmd is recognised and the command requires a value but value is NULL.

       A return code of 0 indicates that both cmd and value are  valid  but  an  error  occurred  attempting  to
       perform  the  operation:  for example due to an error in the syntax of value in this case the error queue
       may provide additional information.

EXAMPLES

       Set supported signature algorithms:

        SSL_CONF_cmd(ctx, "SignatureAlgorithms", "ECDSA+SHA256:RSA+SHA256:DSA+SHA256");

       There are various ways to select the supported protocols.

       This set the minimum protocol version to TLSv1, and so disables SSLv3.  This is the  recommended  way  to
       disable protocols.

        SSL_CONF_cmd(ctx, "MinProtocol", "TLSv1");

       The following also disables SSLv3:

        SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");

       The  following  will  first  enable  all protocols, and then disable SSLv3.  If no protocol versions were
       disabled before this has the same effect as "-SSLv3", but if some versions were disables  this  will  re-
       enable them before disabling SSLv3.

        SSL_CONF_cmd(ctx, "Protocol", "ALL,-SSLv3");

       Only enable TLSv1.2:

        SSL_CONF_cmd(ctx, "MinProtocol", "TLSv1.2");
        SSL_CONF_cmd(ctx, "MaxProtocol", "TLSv1.2");

       This also only enables TLSv1.2:

        SSL_CONF_cmd(ctx, "Protocol", "-ALL,TLSv1.2");

       Disable TLS session tickets:

        SSL_CONF_cmd(ctx, "Options", "-SessionTicket");

       Enable compression:

        SSL_CONF_cmd(ctx, "Options", "Compression");

       Set supported curves to P-256, P-384:

        SSL_CONF_cmd(ctx, "Curves", "P-256:P-384");

SEE ALSO

       SSL_CONF_CTX_new(3), SSL_CONF_CTX_set_flags(3), SSL_CONF_CTX_set1_prefix(3), SSL_CONF_CTX_set_ssl_ctx(3),
       SSL_CONF_cmd_argv(3), SSL_CTX_set_options(3)

HISTORY

       The SSL_CONF_cmd() function was added in OpenSSL 1.0.2.

       The  SSL_OP_NO_SSL2  option  doesn't  have  effect  since  1.1.0, but the macro is retained for backwards
       compatibility.

       The SSL_CONF_TYPE_NONE was added in OpenSSL 1.1.0. In earlier versions of OpenSSL passing a command which
       didn't take an argument would return SSL_CONF_TYPE_UNKNOWN.

       MinProtocol and MaxProtocol where added in OpenSSL 1.1.0.

       AllowNoDHEKEX and PrioritizeChaCha were added in OpenSSL 1.1.1.

COPYRIGHT

       Copyright 2012-2019 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the OpenSSL license (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>.

1.1.1f                                             2025-02-05                                 SSL_CONF_CMD(3SSL)