Provided by: libssl-doc_1.1.0g-2ubuntu4_all bug

NAME

       SSL_CONF_cmd_value_type, SSL_CONF_finish, 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);
        int SSL_CONF_finish(SSL_CONF_CTX *cctx);

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.

       The function SSL_CONF_finish() must be called after all configuration operations have been
       completed. It is used to finalise any operations or to process defaults.

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 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 value argument should be a colon separated list of signature algorithms in order
           of decreasing preference of the form algorithm+hash. 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.

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

       -client_sigalgs
           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 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.

       -curves
           This sets the supported elliptic curves. For clients the curves are sent using the
           supported curves extension. For servers it is used to determine which curve to use.
           This setting affects curves used for both signatures and key exchange, if applicable.

           The value argument is a colon separated list of curves. 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.

       -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 cipher suite list to value. Note: syntax checking of value is currently not
           performed unless a SSL or SSL_CTX structure is associated with cctx.

       -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.

       -min_protocol, -max_protocol
           Sets the minimum and maximum supported protocol.  Currently supported protocol values
           are SSLv3, TLSv1, TLSv1.1, TLSv1.2 for TLS and DTLSv1, DTLSv1.2 for DTLS, and None for
           no limit.  If the 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
           Disables protocol support for SSLv3, TLSv1.0, TLSv1.1 or TLSv1.2 by setting the
           corresponding options SSL_OP_NO_SSLv3, SSL_OP_NO_TLSv1, SSL_OP_NO_TLSv1_1 and
           SSL_OP_NO_TLSv1_2 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.

       -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.

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

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 cipher suite list to value. Note: syntax checking of value is currently not
           performed unless an SSL or SSL_CTX structure is associated with cctx.

       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.

       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.

       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 value argument should be a colon separated list of signature algorithms in order
           of decreasing preference of the form algorithm+hash. 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.

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

       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 with the client certificate.

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

       Curves
           This sets the supported elliptic curves. For clients the curves are sent using the
           supported curves extension. For servers it is used to determine which curve to use.
           This setting affects curves used for both signatures and key exchange, if applicable.

           The value argument is a colon separated list of curves. 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.

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

           Currently supported protocol values are SSLv3, TLSv1, TLSv1.1, TLSv1.2, 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, 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, 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.

           NoResumptionOnRenegotiation set SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION flag.
           Only used by servers.

           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.

       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.

       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_CTX_cmd() it is possible to query if a given 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 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_CTX_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.

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");

       Set automatic support for any elliptic curve for key exchange:

        SSL_CONF_cmd(ctx, "ECDHParameters", "Automatic");

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.

       SSL_CONF_finish() returns 1 for success and 0 for failure.

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

       SSL_CONF_cmd() was first added to OpenSSL 1.0.2

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

       SSL_CONF_TYPE_NONE was first added to 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.

COPYRIGHT

       Copyright 2012-2016 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>.