add SSL_CONF functions and documentation

doc/ssl/SSL_CONF_cmd.pod

diff --git a/doc/ssl/SSL_CONF_cmd.pod b/doc/ssl/SSL_CONF_cmd.pod
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+=pod
+
+=head1 NAME
+
+SSL_CONF_cmd - send configuration command
+
+=head1 SYNOPSIS
+
+ #include <openssl/ssl.h>
+
+ int SSL_CONF_cmd(SSL_CONF_CTX *cctx, const char *cmd, const char *value);
+
+=head1 DESCRIPTION
+
+The function SSL_CONF_cmd() performs configuration operation B<cmd> with
+optional parameter B<value> on B<ctx>. Its purpose is to simplify application
+configuration of B<SSL_CTX> or B<SSL> structures by providing a common
+framework for configuration files or command line options.
+
+=head1 SUPPORTED CONFIGURATION FILE COMMANDS
+
+Currently supported B<cmd> names for configuration files (i.e. when the
+flag B<SSL_CONF_FLAG_FILE> is set) are listed below. All configuration file
+B<cmd> names and are case insensitive so B<signaturealgorithms> is recognised
+as well as B<SignatureAlgorithms>. Unless otherwise states the B<value> names
+are also case insensitive.
+
+Note: the command prefix (if set) alters the recognised B<cmd> values.
+
+=over 4
+
+=item B<CipherSuite>
+
+Sets the cipher suite list to B<value>. Note: syntax checking of B<value> is
+currently not performed unless a B<SSL> or B<SSL_CTX> structure is 
+associated with B<cctx>.
+
+=item B<SignatureAlgorithms>
+
+This sets the supported signature algorithms for TLS v1.2. 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 B<value> argument should be a colon separated list of signature algorithms
+in order of decreasing preference of the form B<algorithm+hash>. B<algorithm>
+is one of B<RSA>, B<DSA> or B<ECDSA> and B<hash> is a supported algorithm
+OID short name such as B<SHA1>, B<SHA224>, B<SHA256>, B<SHA384> of B<SHA512>.
+Note: algorithm and hash names are case sensitive.
+
+If this option is not set then all signature algorithms supported by the
+OpenSSL library are permissible.
+
+=item B<ClientSignatureAlgorithms>
+
+This sets the supported signature algorithms associated with client
+authentication for TLS v1.2. For servers the value is used in the supported
+signature algorithms field of a certificate request. For clients it is
+used to determine which signature algorithm to use for the client certificate.
+
+The syntax of B<value> is identical to B<SignatureAlgorithms>. If not set then
+the value set for B<SignatureAlgorithms> will be used instead.
+
+=item B<Curves>
+
+This sets the supported elliptic curves. For servers the curves are
+sent using the supported curves extension to TLS. For clients the it is used
+to determine which curve to use. This affects curves used for both signatures
+and key exchange.
+
+The B<value> argument is a colon separated list of curves. The curve can be
+either the B<NIST> name (e.g. B<P-256>) or an OpenSSL OID name (e.g
+B<prime256v1>). Curve names are case sensitive.
+
+=item B<ECDHParameters>
+
+This sets the temporary curve used for ephemeral ECDH modes.
+
+The B<value> argument is a curve name or the special value B<Automatic> which
+automatically picks an appropriate curve based on client and server
+preferences. The curve can be either the B<NIST> name (e.g. B<P-256>) or an
+OpenSSL OID name (e.g B<prime256v1>). Curve names are case sensitive.
+
+=item B<Protocol>
+
+The supported versions of the SSL or TLS protocol.
+
+The B<value> argument is a comma separated list of supported protocols to
+enable or disable. If an protocol is preceded by B<-> that version is disabled.
+All versions are enabled by default, though applications may choose to
+explicitly disable some version. Currently supported protocol
+values are B<SSLv2>, B<SSLv3>, B<TLSv1>, B<TLSv1.1> and B<TLSv1.2>. The
+special value B<ALL> refers to all supported versions.
+
+=item B<Options>
+
+The B<value> argument is a comma separated list of various flags to set.
+If a flag string is preceded B<-> it is disabled. See the
+B<SSL_CTX_set_options> function for more details of individual options.
+
+Each option is listed below. Where an operation is enabled by default
+the B<-flag> syntax is needed to disable it.
+
+B<SessionTicket>: session ticket support, enabled by default. Inverse of
+B<SSL_OP_NO_TICKET>: that is B<-SessionTicket> is the same as setting
+B<SSL_OP_NO_TICKET>.
+
+B<Compression>: SSL/TLS compression support, enabled by default. Inverse
+of B<SSL_OP_NO_COMPRESSION>.
+
+B<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 B<SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS>.
+
+B<Bugs> enable various bug workarounds. Same as B<SSL_OP_ALL>.
+
+B<DHSingle> enable single use DH keys, set by default. Inverse of
+B<SSL_OP_DH_SINGLE>. Only used by servers.
+
+B<ECDHSingle> enable single use ECDH keys, set by default. Inverse of
+B<SSL_OP_ECDH_SINGLE>. Only used by servers.
+
+B<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
+B<SSL_OP_CIPHER_SERVER_PREFERENCE>. Only used by servers.
+
+B<UnsafeLegacyRenegotiation> permits the use of unsafe legacy renegotiation.
+Equivalent to B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION>.
+
+B<UnsafeLegacyServerConnect> permits the use of unsafe legacy renegotiation
+for OpenSSL clients only. Equivalent to B<SSL_OP_LEGACY_SERVER_CONNECT>.
+Set by default.
+
+=back
+
+=head1 SUPPORTED COMMAND LINE COMMANDS
+
+Currently supported B<cmd> names for command lines (i.e. when the
+flag B<SSL_CONF_CMDLINE> is set) are listed below. Note: all B<cmd> names
+and are case sensitive. Unless otherwise stated the B<value> parameter is
+noh used. The default prefix for command line commands is B<-> and that is
+reflected below.
+
+=over 4
+
+=item B<-sigalgs>
+
+Sets the supported signature algorithms to B<value>. Equivalent to the
+B<SignatureAlgorithms> file command.
+
+=item B<-client_sigalgs>
+
+Sets the supported client signature algorithms to B<value>. Equivalent to the
+B<ClientSignatureAlgorithms> file command.
+
+=item B<-curves>
+
+Sets supported elliptic curves to B<value>. Equivalent to B<Curves> file
+command.
+
+=item B<-named_curve>
+
+Sets supported ECDH parameters to B<value>. For automatic curve selection
+B<value> should be set to B<auto>, otherwise the command is identical to
+the B<ECDHParameters> file command.
+
+=item B<-cipher>
+
+Sets the cipher suite list to B<value>. Note: syntax checking of B<value> is
+currently not performed unless a B<SSL> or B<SSL_CTX> structure is 
+associated with B<cctx>.
+
+=item B<-no_ssl2>, B<-no_ssl3>, B<-no_tls1>, B<-no_tls1_1>, B<-no_tls1_2>
+
+Disables protocol support for SSLv2, SSLv3, TLS 1.0, TLS 1.1 or TLS 1.2 
+by setting the corresponding options B<SSL_OP_NO_SSL2>, B<SSL_OP_NO_SSL3>,
+B<SSL_OP_NO_TLS1> B<SSL_OP_NO_TLS1_1> and B<SSL_OP_NO_TLS1_2> respectively.
+
+=item B<-bugs>
+
+Various bug workarounds are set, same as setting B<SSL_OP_ALL>.
+
+=item B<-no_comp>
+
+Disables support for SSL/TLS compression, same as setting B<SSL_OP_NO_COMPRESS>.
+
+=item B<-no_ticket>
+
+Disables support for session tickets, same as setting B<SSL_OP_NO_TICKET>.
+
+=item B<-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 B<SSL_OP_CIPHER_SERVER_PREFERENCE>. Only used by servers.
+
+=item B<-legacyrenegotiation>
+
+permits the use of unsafe legacy renegotiation. Equivalent to setting
+B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION>.
+
+=item B<-legacy_server_connect>, B<-no_legacy_server_connect>
+
+permits or prohibits the use of unsafe legacy renegotiation for OpenSSL
+clients only. Equivalent to setting or clearing B<SSL_OP_LEGACY_SERVER_CONNECT>.
+Set by default.
+
+=item B<-strict>
+
+enables strict mode protocol handling. Equivalent to setting
+B<SSL_CERT_FLAG_TLS_STRICT>.
+
+=item B<-debug_broken_protocol>
+
+disables various checks and permits several kinds of broken protocol behaviour
+for testing purposes: it should B<NEVER> be used in anything other than a test
+environment. Only supported if OpenSSL is configured with
+B<-DOPENSSL_SSL_DEBUG_BROKEN_PROTOCOL>.
+
+=back
+
+=head1 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", "-SSLv2");
+ SSL_CONF_cmd(ctx, userparam, uservalue);
+
+it will disable SSLv2 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", "-SSLv2");
+
+SSLv2 is B<always> disabled and attempt to override this by the user are
+ignored.
+
+By checking the return code of SSL_CTX_cmd() it is possible to query if a
+given B<cmd> is recognised, this is useful is SSL_CTX_cmd() values are
+mixed with additional application specific operations.
+
+For example an application might call SSL_CTX_cmd() and if it returns
+-2 (unrecognised command) continue with processing of application specific
+commands.
+
+Applications can also use SSL_CTX_cmd() to process command lines though the
+utility function SSL_CTX_cmd_argv() is normally used instead. One way
+to do this is to check for an initial prefix ("-", "--" or "--ssl-" for example)
+on a command argument and pass the rest to B<cmd>. The following argument
+is passed to B<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_CTX_cmd(). If -2 is
+returned then B<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.
+
+=head1 EXAMPLES
+
+Set supported signature algorithms:
+
+ SSL_CONF_cmd(ctx, "SignatureAlgorithms", "ECDSA+SHA256:RSA+SHA256:DSA+SHA256");
+
+Enable all protocols except SSLv3 and SSLv2:
+
+ SSL_CONF_cmd(ctx, "Protocol", "ALL,-SSLv3,-SSLv2");
+
+Only enable TLSv1.2:
+
+ SSL_CONF_cmd(ctx, "Protocol", "-ALL,TLSv1.2");
+
+Disable TLS session tickets:
+
+ SSL_CONF_cmd(ctx, "Options", "-SessionTicket");
+
+Set supported curves to P-256, P-384:
+
+ SSL_CONF_cmd(ctx, "Curves", "P-256:P-384");
+
+Set automatic support for any elliptic curve for key exchange:
+
+ SSL_CONF_cmd(ctx, "ECDHParameters", "Automatic");
+
+=head1 RETURN VALUES
+
+SSL_CONF_cmd() return 1 if the value of B<cmd> is recognised and B<value> is
+B<NOT> used and 2 if both B<cmd> and B<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 B<cmd> is not recognised.
+
+A return value of -3 means B<cmd> is recognised and the command requires a
+value but B<value> is NULL.
+
+A return code of 0 indicates that both B<cmd> and B<value> are valid but an
+error occurred attempting to perform the operation: for example due to an
+error in the syntax of B<value> in this case the error queue may provide
+additional information.
+
+=head1 SEE ALSO
+
+L<SSL_CONF_CTX_new(3)|SSL_CONF_CTX_new(3)>,
+L<SSL_CONF_CTX_set_flags(3)|SSL_CONF_CTX_set_flags(3)>,
+L<SSL_CONF_CTX_set1_prefix(3)|SSL_CONF_CTX_set1_prefix(3)>,
+L<SSL_CONF_CTX_set_ssl_ctx(3)|SSL_CONF_CTX_set_ssl_ctx(3)>,
+L<SSL_CONF_cmd_argv(3)|SSL_CONF_cmd_argv(3)>
+
+=head1 HISTORY
+
+SSL_CONF_cmd() was first added to OpenSSL 1.1.0
+
+=cut