433 lines
16 KiB
Text
433 lines
16 KiB
Text
=pod
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=head1 NAME
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SSL_CONF_cmd - send configuration command
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=head1 SYNOPSIS
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#include <openssl/ssl.h>
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int SSL_CONF_cmd(SSL_CONF_CTX *cctx, const char *cmd, const char *value);
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int SSL_CONF_cmd_value_type(SSL_CONF_CTX *cctx, const char *cmd);
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int SSL_CONF_finish(SSL_CONF_CTX *cctx);
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=head1 DESCRIPTION
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The function SSL_CONF_cmd() performs configuration operation B<cmd> with
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optional parameter B<value> on B<ctx>. Its purpose is to simplify application
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configuration of B<SSL_CTX> or B<SSL> structures by providing a common
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framework for command line options or configuration files.
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SSL_CONF_cmd_value_type() returns the type of value that B<cmd> refers to.
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The function SSL_CONF_finish() must be called after all configuration
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operations have been completed. It is used to finalise any operations
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or to process defaults.
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=head1 SUPPORTED COMMAND LINE COMMANDS
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Currently supported B<cmd> names for command lines (i.e. when the
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flag B<SSL_CONF_CMDLINE> is set) are listed below. Note: all B<cmd> names
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are case sensitive. Unless otherwise stated commands can be used by
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both clients and servers and the B<value> parameter is not used. The default
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prefix for command line commands is B<-> and that is reflected below.
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=over 4
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=item B<-sigalgs>
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This sets the supported signature algorithms for TLS v1.2. For clients this
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value is used directly for the supported signature algorithms extension. For
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servers it is used to determine which signature algorithms to support.
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The B<value> argument should be a colon separated list of signature algorithms
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in order of decreasing preference of the form B<algorithm+hash>. B<algorithm>
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is one of B<RSA>, B<DSA> or B<ECDSA> and B<hash> is a supported algorithm
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OID short name such as B<SHA1>, B<SHA224>, B<SHA256>, B<SHA384> of B<SHA512>.
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Note: algorithm and hash names are case sensitive.
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If this option is not set then all signature algorithms supported by the
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OpenSSL library are permissible.
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=item B<-client_sigalgs>
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This sets the supported signature algorithms associated with client
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authentication for TLS v1.2. For servers the value is used in the supported
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signature algorithms field of a certificate request. For clients it is
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used to determine which signature algorithm to with the client certificate.
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If a server does not request a certificate this option has no effect.
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The syntax of B<value> is identical to B<-sigalgs>. If not set then
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the value set for B<-sigalgs> will be used instead.
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=item B<-curves>
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This sets the supported elliptic curves. For clients the curves are
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sent using the supported curves extension. For servers it is used
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to determine which curve to use. This setting affects curves used for both
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signatures and key exchange, if applicable.
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The B<value> argument is a colon separated list of curves. The curve can be
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either the B<NIST> name (e.g. B<P-256>) or an OpenSSL OID name (e.g
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B<prime256v1>). Curve names are case sensitive.
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=item B<-named_curve>
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This sets the temporary curve used for ephemeral ECDH modes. Only used by
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servers
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The B<value> argument is a curve name or the special value B<auto> which
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picks an appropriate curve based on client and server preferences. The curve
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can be either the B<NIST> name (e.g. B<P-256>) or an OpenSSL OID name
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(e.g B<prime256v1>). Curve names are case sensitive.
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=item B<-cipher>
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Sets the cipher suite list to B<value>. Note: syntax checking of B<value> is
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currently not performed unless a B<SSL> or B<SSL_CTX> structure is
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associated with B<cctx>.
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=item B<-cert>
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Attempts to use the file B<value> as the certificate for the appropriate
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context. It currently uses SSL_CTX_use_certificate_chain_file() if an B<SSL_CTX>
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structure is set or SSL_use_certificate_file() with filetype PEM if an B<SSL>
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structure is set. This option is only supported if certificate operations
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are permitted.
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=item B<-key>
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Attempts to use the file B<value> as the private key for the appropriate
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context. This option is only supported if certificate operations
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are permitted. Note: if no B<-key> option is set then a private key is
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not loaded: it does not currently use the B<-cert> file.
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=item B<-dhparam>
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Attempts to use the file B<value> as the set of temporary DH parameters for
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the appropriate context. This option is only supported if certificate
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operations are permitted.
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=item B<-no_ssl2>, B<-no_ssl3>, B<-no_tls1>, B<-no_tls1_1>, B<-no_tls1_2>
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Disables protocol support for SSLv2, SSLv3, TLS 1.0, TLS 1.1 or TLS 1.2
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by setting the corresponding options B<SSL_OP_NO_SSL2>, B<SSL_OP_NO_SSL3>,
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B<SSL_OP_NO_TLS1>, B<SSL_OP_NO_TLS1_1> and B<SSL_OP_NO_TLS1_2> respectively.
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=item B<-bugs>
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Various bug workarounds are set, same as setting B<SSL_OP_ALL>.
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=item B<-no_comp>
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Disables support for SSL/TLS compression, same as setting B<SSL_OP_NO_COMPRESS>.
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=item B<-no_ticket>
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Disables support for session tickets, same as setting B<SSL_OP_NO_TICKET>.
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=item B<-serverpref>
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Use server and not client preference order when determining which cipher suite,
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signature algorithm or elliptic curve to use for an incoming connection.
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Equivalent to B<SSL_OP_CIPHER_SERVER_PREFERENCE>. Only used by servers.
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=item B<-no_resumption_on_reneg>
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set SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION flag. Only used by servers.
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=item B<-legacyrenegotiation>
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permits the use of unsafe legacy renegotiation. Equivalent to setting
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B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION>.
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=item B<-legacy_server_connect>, B<-no_legacy_server_connect>
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permits or prohibits the use of unsafe legacy renegotiation for OpenSSL
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clients only. Equivalent to setting or clearing B<SSL_OP_LEGACY_SERVER_CONNECT>.
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Set by default.
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=item B<-strict>
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enables strict mode protocol handling. Equivalent to setting
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B<SSL_CERT_FLAG_TLS_STRICT>.
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=item B<-debug_broken_protocol>
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disables various checks and permits several kinds of broken protocol behaviour
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for testing purposes: it should B<NEVER> be used in anything other than a test
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environment. Only supported if OpenSSL is configured with
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B<-DOPENSSL_SSL_DEBUG_BROKEN_PROTOCOL>.
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=back
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=head1 SUPPORTED CONFIGURATION FILE COMMANDS
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Currently supported B<cmd> names for configuration files (i.e. when the
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flag B<SSL_CONF_FLAG_FILE> is set) are listed below. All configuration file
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B<cmd> names and are case insensitive so B<signaturealgorithms> is recognised
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as well as B<SignatureAlgorithms>. Unless otherwise stated the B<value> names
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are also case insensitive.
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Note: the command prefix (if set) alters the recognised B<cmd> values.
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=over 4
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=item B<CipherString>
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Sets the cipher suite list to B<value>. Note: syntax checking of B<value> is
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currently not performed unless an B<SSL> or B<SSL_CTX> structure is
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associated with B<cctx>.
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=item B<Certificate>
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Attempts to use the file B<value> as the certificate for the appropriate
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context. It currently uses SSL_CTX_use_certificate_chain_file() if an B<SSL_CTX>
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structure is set or SSL_use_certificate_file() with filetype PEM if an B<SSL>
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structure is set. This option is only supported if certificate operations
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are permitted.
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=item B<PrivateKey>
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Attempts to use the file B<value> as the private key for the appropriate
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context. This option is only supported if certificate operations
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are permitted. Note: if no B<-key> option is set then a private key is
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not loaded: it does not currently use the B<Certificate> file.
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=item B<DHParameters>
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Attempts to use the file B<value> as the set of temporary DH parameters for
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the appropriate context. This option is only supported if certificate
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operations are permitted.
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=item B<SignatureAlgorithms>
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This sets the supported signature algorithms for TLS v1.2. For clients this
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value is used directly for the supported signature algorithms extension. For
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servers it is used to determine which signature algorithms to support.
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The B<value> argument should be a colon separated list of signature algorithms
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in order of decreasing preference of the form B<algorithm+hash>. B<algorithm>
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is one of B<RSA>, B<DSA> or B<ECDSA> and B<hash> is a supported algorithm
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OID short name such as B<SHA1>, B<SHA224>, B<SHA256>, B<SHA384> of B<SHA512>.
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Note: algorithm and hash names are case sensitive.
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If this option is not set then all signature algorithms supported by the
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OpenSSL library are permissible.
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=item B<ClientSignatureAlgorithms>
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This sets the supported signature algorithms associated with client
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authentication for TLS v1.2. For servers the value is used in the supported
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signature algorithms field of a certificate request. For clients it is
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used to determine which signature algorithm to with the client certificate.
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The syntax of B<value> is identical to B<SignatureAlgorithms>. If not set then
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the value set for B<SignatureAlgorithms> will be used instead.
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=item B<Curves>
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This sets the supported elliptic curves. For clients the curves are
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sent using the supported curves extension. For servers it is used
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to determine which curve to use. This setting affects curves used for both
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signatures and key exchange, if applicable.
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The B<value> argument is a colon separated list of curves. The curve can be
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either the B<NIST> name (e.g. B<P-256>) or an OpenSSL OID name (e.g
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B<prime256v1>). Curve names are case sensitive.
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=item B<ECDHParameters>
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This sets the temporary curve used for ephemeral ECDH modes. Only used by
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servers
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The B<value> argument is a curve name or the special value B<Automatic> which
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picks an appropriate curve based on client and server preferences. The curve
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can be either the B<NIST> name (e.g. B<P-256>) or an OpenSSL OID name
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(e.g B<prime256v1>). Curve names are case sensitive.
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=item B<Protocol>
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The supported versions of the SSL or TLS protocol.
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The B<value> argument is a comma separated list of supported protocols to
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enable or disable. If an protocol is preceded by B<-> that version is disabled.
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All versions are enabled by default, though applications may choose to
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explicitly disable some. Currently supported protocol values are B<SSLv2>,
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B<SSLv3>, B<TLSv1>, B<TLSv1.1> and B<TLSv1.2>. The special value B<ALL> refers
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to all supported versions.
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=item B<Options>
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The B<value> argument is a comma separated list of various flags to set.
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If a flag string is preceded B<-> it is disabled. See the
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B<SSL_CTX_set_options> function for more details of individual options.
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Each option is listed below. Where an operation is enabled by default
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the B<-flag> syntax is needed to disable it.
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B<SessionTicket>: session ticket support, enabled by default. Inverse of
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B<SSL_OP_NO_TICKET>: that is B<-SessionTicket> is the same as setting
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B<SSL_OP_NO_TICKET>.
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B<Compression>: SSL/TLS compression support, enabled by default. Inverse
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of B<SSL_OP_NO_COMPRESSION>.
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B<EmptyFragments>: use empty fragments as a countermeasure against a
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SSL 3.0/TLS 1.0 protocol vulnerability affecting CBC ciphers. It
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is set by default. Inverse of B<SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS>.
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B<Bugs>: enable various bug workarounds. Same as B<SSL_OP_ALL>.
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B<DHSingle>: enable single use DH keys, set by default. Inverse of
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B<SSL_OP_DH_SINGLE>. Only used by servers.
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B<ECDHSingle> enable single use ECDH keys, set by default. Inverse of
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B<SSL_OP_ECDH_SINGLE>. Only used by servers.
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B<ServerPreference> use server and not client preference order when
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determining which cipher suite, signature algorithm or elliptic curve
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to use for an incoming connection. Equivalent to
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B<SSL_OP_CIPHER_SERVER_PREFERENCE>. Only used by servers.
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B<NoResumptionOnRenegotiation> set
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B<SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION> flag. Only used by servers.
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B<UnsafeLegacyRenegotiation> permits the use of unsafe legacy renegotiation.
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Equivalent to B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION>.
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B<UnsafeLegacyServerConnect> permits the use of unsafe legacy renegotiation
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for OpenSSL clients only. Equivalent to B<SSL_OP_LEGACY_SERVER_CONNECT>.
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Set by default.
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=back
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=head1 SUPPORTED COMMAND TYPES
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The function SSL_CONF_cmd_value_type() currently returns one of the following
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types:
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=over 4
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=item B<SSL_CONF_TYPE_UNKNOWN>
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The B<cmd> string is unrecognised, this return value can be use to flag
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syntax errors.
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=item B<SSL_CONF_TYPE_STRING>
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The value is a string without any specific structure.
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=item B<SSL_CONF_TYPE_FILE>
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The value is a file name.
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=item B<SSL_CONF_TYPE_DIR>
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The value is a directory name.
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=back
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=head1 NOTES
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The order of operations is significant. This can be used to set either defaults
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or values which cannot be overridden. For example if an application calls:
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SSL_CONF_cmd(ctx, "Protocol", "-SSLv2");
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SSL_CONF_cmd(ctx, userparam, uservalue);
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it will disable SSLv2 support by default but the user can override it. If
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however the call sequence is:
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SSL_CONF_cmd(ctx, userparam, uservalue);
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SSL_CONF_cmd(ctx, "Protocol", "-SSLv2");
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SSLv2 is B<always> disabled and attempt to override this by the user are
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ignored.
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By checking the return code of SSL_CTX_cmd() it is possible to query if a
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given B<cmd> is recognised, this is useful is SSL_CTX_cmd() values are
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mixed with additional application specific operations.
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For example an application might call SSL_CTX_cmd() and if it returns
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-2 (unrecognised command) continue with processing of application specific
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commands.
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Applications can also use SSL_CTX_cmd() to process command lines though the
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utility function SSL_CTX_cmd_argv() is normally used instead. One way
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to do this is to set the prefix to an appropriate value using
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SSL_CONF_CTX_set1_prefix(), pass the current argument to B<cmd> and the
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following argument to B<value> (which may be NULL).
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In this case if the return value is positive then it is used to skip that
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number of arguments as they have been processed by SSL_CTX_cmd(). If -2 is
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returned then B<cmd> is not recognised and application specific arguments
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can be checked instead. If -3 is returned a required argument is missing
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and an error is indicated. If 0 is returned some other error occurred and
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this can be reported back to the user.
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The function SSL_CONF_cmd_value_type() can be used by applications to
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check for the existence of a command or to perform additional syntax
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checking or translation of the command value. For example if the return
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value is B<SSL_CONF_TYPE_FILE> an application could translate a relative
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pathname to an absolute pathname.
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=head1 EXAMPLES
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Set supported signature algorithms:
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SSL_CONF_cmd(ctx, "SignatureAlgorithms", "ECDSA+SHA256:RSA+SHA256:DSA+SHA256");
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Enable all protocols except SSLv3 and SSLv2:
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SSL_CONF_cmd(ctx, "Protocol", "ALL,-SSLv3,-SSLv2");
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Only enable TLSv1.2:
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SSL_CONF_cmd(ctx, "Protocol", "-ALL,TLSv1.2");
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Disable TLS session tickets:
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SSL_CONF_cmd(ctx, "Options", "-SessionTicket");
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Set supported curves to P-256, P-384:
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SSL_CONF_cmd(ctx, "Curves", "P-256:P-384");
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Set automatic support for any elliptic curve for key exchange:
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SSL_CONF_cmd(ctx, "ECDHParameters", "Automatic");
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=head1 RETURN VALUES
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SSL_CONF_cmd() returns 1 if the value of B<cmd> is recognised and B<value> is
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B<NOT> used and 2 if both B<cmd> and B<value> are used. In other words it
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returns the number of arguments processed. This is useful when processing
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command lines.
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A return value of -2 means B<cmd> is not recognised.
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A return value of -3 means B<cmd> is recognised and the command requires a
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value but B<value> is NULL.
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A return code of 0 indicates that both B<cmd> and B<value> are valid but an
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error occurred attempting to perform the operation: for example due to an
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error in the syntax of B<value> in this case the error queue may provide
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additional information.
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SSL_CONF_finish() returns 1 for success and 0 for failure.
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=head1 SEE ALSO
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L<SSL_CONF_CTX_new(3)|SSL_CONF_CTX_new(3)>,
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L<SSL_CONF_CTX_set_flags(3)|SSL_CONF_CTX_set_flags(3)>,
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L<SSL_CONF_CTX_set1_prefix(3)|SSL_CONF_CTX_set1_prefix(3)>,
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L<SSL_CONF_CTX_set_ssl_ctx(3)|SSL_CONF_CTX_set_ssl_ctx(3)>,
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L<SSL_CONF_cmd_argv(3)|SSL_CONF_cmd_argv(3)>
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=head1 HISTORY
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SSL_CONF_cmd() was first added to OpenSSL 1.0.2
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=cut
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