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.\" ========================================================================
.\"
.IX Title "SSL_CONF_cmd 3"
.TH SSL_CONF_cmd 3 "2019-12-20" "1.0.2u" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
SSL_CONF_cmd \- send configuration command
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #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);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The function \fBSSL_CONF_cmd()\fR performs configuration operation \fBcmd\fR with
optional parameter \fBvalue\fR on \fBctx\fR. Its purpose is to simplify application
configuration of \fB\s-1SSL_CTX\s0\fR or \fB\s-1SSL\s0\fR structures by providing a common
framework for command line options or configuration files.
.PP
\&\fBSSL_CONF_cmd_value_type()\fR returns the type of value that \fBcmd\fR refers to.
.PP
The function \fBSSL_CONF_finish()\fR must be called after all configuration
operations have been completed. It is used to finalise any operations
or to process defaults.
.SH "SUPPORTED COMMAND LINE COMMANDS"
.IX Header "SUPPORTED COMMAND LINE COMMANDS"
Currently supported \fBcmd\fR names for command lines (i.e. when the
flag \fB\s-1SSL_CONF_CMDLINE\s0\fR is set) are listed below. Note: all \fBcmd\fR names
are case sensitive. Unless otherwise stated commands can be used by
both clients and servers and the \fBvalue\fR parameter is not used. The default
prefix for command line commands is \fB\-\fR and that is reflected below.
.IP "\fB\-sigalgs\fR" 4
.IX Item "-sigalgs"
This sets the supported signature algorithms for \s-1TLS\s0 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.
.Sp
The \fBvalue\fR argument should be a colon separated list of signature algorithms
in order of decreasing preference of the form \fBalgorithm+hash\fR. \fBalgorithm\fR
is one of \fB\s-1RSA\s0\fR, \fB\s-1DSA\s0\fR or \fB\s-1ECDSA\s0\fR and \fBhash\fR is a supported algorithm
\&\s-1OID\s0 short name such as \fB\s-1SHA1\s0\fR, \fB\s-1SHA224\s0\fR, \fB\s-1SHA256\s0\fR, \fB\s-1SHA384\s0\fR of \fB\s-1SHA512\s0\fR.
Note: algorithm and hash names are case sensitive.
.Sp
If this option is not set then all signature algorithms supported by the
OpenSSL library are permissible.
.IP "\fB\-client_sigalgs\fR" 4
.IX Item "-client_sigalgs"
This sets the supported signature algorithms associated with client
authentication for \s-1TLS\s0 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.
.Sp
The syntax of \fBvalue\fR is identical to \fB\-sigalgs\fR. If not set then
the value set for \fB\-sigalgs\fR will be used instead.
.IP "\fB\-curves\fR" 4
.IX Item "-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.
.Sp
The \fBvalue\fR argument is a colon separated list of curves. The curve can be
either the \fB\s-1NIST\s0\fR name (e.g. \fBP\-256\fR) or an OpenSSL \s-1OID\s0 name (e.g
\&\fBprime256v1\fR). Curve names are case sensitive.
.IP "\fB\-named_curve\fR" 4
.IX Item "-named_curve"
This sets the temporary curve used for ephemeral \s-1ECDH\s0 modes. Only used by
servers
.Sp
The \fBvalue\fR argument is a curve name or the special value \fBauto\fR which
picks an appropriate curve based on client and server preferences. The curve
can be either the \fB\s-1NIST\s0\fR name (e.g. \fBP\-256\fR) or an OpenSSL \s-1OID\s0 name
(e.g \fBprime256v1\fR). Curve names are case sensitive.
.IP "\fB\-cipher\fR" 4
.IX Item "-cipher"
Sets the cipher suite list to \fBvalue\fR. Note: syntax checking of \fBvalue\fR is
currently not performed unless a \fB\s-1SSL\s0\fR or \fB\s-1SSL_CTX\s0\fR structure is
associated with \fBcctx\fR.
.IP "\fB\-cert\fR" 4
.IX Item "-cert"
Attempts to use the file \fBvalue\fR as the certificate for the appropriate
context. It currently uses \fBSSL_CTX_use_certificate_chain_file()\fR if an \fB\s-1SSL_CTX\s0\fR
structure is set or \fBSSL_use_certificate_file()\fR with filetype \s-1PEM\s0 if an \fB\s-1SSL\s0\fR
structure is set. This option is only supported if certificate operations
are permitted.
.IP "\fB\-key\fR" 4
.IX Item "-key"
Attempts to use the file \fBvalue\fR as the private key for the appropriate
context. This option is only supported if certificate operations
are permitted. Note: if no \fB\-key\fR option is set then a private key is
not loaded: it does not currently use the \fB\-cert\fR file.
.IP "\fB\-dhparam\fR" 4
.IX Item "-dhparam"
Attempts to use the file \fBvalue\fR as the set of temporary \s-1DH\s0 parameters for
the appropriate context. This option is only supported if certificate
operations are permitted.
.IP "\fB\-no_ssl2\fR, \fB\-no_ssl3\fR, \fB\-no_tls1\fR, \fB\-no_tls1_1\fR, \fB\-no_tls1_2\fR" 4
.IX Item "-no_ssl2, -no_ssl3, -no_tls1, -no_tls1_1, -no_tls1_2"
Disables protocol support for SSLv2, SSLv3, TLSv1.0, TLSv1.1 or TLSv1.2
by setting the corresponding options \fBSSL_OP_NO_SSLv2\fR, \fBSSL_OP_NO_SSLv3\fR,
\&\fBSSL_OP_NO_TLSv1\fR, \fBSSL_OP_NO_TLSv1_1\fR and \fBSSL_OP_NO_TLSv1_2\fR respectively.
.IP "\fB\-bugs\fR" 4
.IX Item "-bugs"
Various bug workarounds are set, same as setting \fB\s-1SSL_OP_ALL\s0\fR.
.IP "\fB\-no_comp\fR" 4
.IX Item "-no_comp"
Disables support for \s-1SSL/TLS\s0 compression, same as setting \fB\s-1SSL_OP_NO_COMPRESS\s0\fR.
.IP "\fB\-no_ticket\fR" 4
.IX Item "-no_ticket"
Disables support for session tickets, same as setting \fB\s-1SSL_OP_NO_TICKET\s0\fR.
.IP "\fB\-serverpref\fR" 4
.IX Item "-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 \fB\s-1SSL_OP_CIPHER_SERVER_PREFERENCE\s0\fR. Only used by servers.
.IP "\fB\-no_resumption_on_reneg\fR" 4
.IX Item "-no_resumption_on_reneg"
set \s-1SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION\s0 flag. Only used by servers.
.IP "\fB\-legacyrenegotiation\fR" 4
.IX Item "-legacyrenegotiation"
permits the use of unsafe legacy renegotiation. Equivalent to setting
\&\fB\s-1SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION\s0\fR.
.IP "\fB\-legacy_server_connect\fR, \fB\-no_legacy_server_connect\fR" 4
.IX Item "-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 \fB\s-1SSL_OP_LEGACY_SERVER_CONNECT\s0\fR.
Set by default.
.IP "\fB\-strict\fR" 4
.IX Item "-strict"
enables strict mode protocol handling. Equivalent to setting
\&\fB\s-1SSL_CERT_FLAG_TLS_STRICT\s0\fR.
.IP "\fB\-debug_broken_protocol\fR" 4
.IX Item "-debug_broken_protocol"
disables various checks and permits several kinds of broken protocol behaviour
for testing purposes: it should \fB\s-1NEVER\s0\fR be used in anything other than a test
environment. Only supported if OpenSSL is configured with
\&\fB\-DOPENSSL_SSL_DEBUG_BROKEN_PROTOCOL\fR.
.SH "SUPPORTED CONFIGURATION FILE COMMANDS"
.IX Header "SUPPORTED CONFIGURATION FILE COMMANDS"
Currently supported \fBcmd\fR names for configuration files (i.e. when the
flag \fB\s-1SSL_CONF_FLAG_FILE\s0\fR is set) are listed below. All configuration file
\&\fBcmd\fR names and are case insensitive so \fBsignaturealgorithms\fR is recognised
as well as \fBSignatureAlgorithms\fR. Unless otherwise stated the \fBvalue\fR names
are also case insensitive.
.PP
Note: the command prefix (if set) alters the recognised \fBcmd\fR values.
.IP "\fBCipherString\fR" 4
.IX Item "CipherString"
Sets the cipher suite list to \fBvalue\fR. Note: syntax checking of \fBvalue\fR is
currently not performed unless an \fB\s-1SSL\s0\fR or \fB\s-1SSL_CTX\s0\fR structure is
associated with \fBcctx\fR.
.IP "\fBCertificate\fR" 4
.IX Item "Certificate"
Attempts to use the file \fBvalue\fR as the certificate for the appropriate
context. It currently uses \fBSSL_CTX_use_certificate_chain_file()\fR if an \fB\s-1SSL_CTX\s0\fR
structure is set or \fBSSL_use_certificate_file()\fR with filetype \s-1PEM\s0 if an \fB\s-1SSL\s0\fR
structure is set. This option is only supported if certificate operations
are permitted.
.IP "\fBPrivateKey\fR" 4
.IX Item "PrivateKey"
Attempts to use the file \fBvalue\fR as the private key for the appropriate
context. This option is only supported if certificate operations
are permitted. Note: if no \fB\-key\fR option is set then a private key is
not loaded: it does not currently use the \fBCertificate\fR file.
.IP "\fBServerInfoFile\fR" 4
.IX Item "ServerInfoFile"
Attempts to use the file \fBvalue\fR in the \*(L"serverinfo\*(R" extension using the
function SSL_CTX_use_serverinfo_file.
.IP "\fBDHParameters\fR" 4
.IX Item "DHParameters"
Attempts to use the file \fBvalue\fR as the set of temporary \s-1DH\s0 parameters for
the appropriate context. This option is only supported if certificate
operations are permitted.
.IP "\fBSignatureAlgorithms\fR" 4
.IX Item "SignatureAlgorithms"
This sets the supported signature algorithms for \s-1TLS\s0 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.
.Sp
The \fBvalue\fR argument should be a colon separated list of signature algorithms
in order of decreasing preference of the form \fBalgorithm+hash\fR. \fBalgorithm\fR
is one of \fB\s-1RSA\s0\fR, \fB\s-1DSA\s0\fR or \fB\s-1ECDSA\s0\fR and \fBhash\fR is a supported algorithm
\&\s-1OID\s0 short name such as \fB\s-1SHA1\s0\fR, \fB\s-1SHA224\s0\fR, \fB\s-1SHA256\s0\fR, \fB\s-1SHA384\s0\fR of \fB\s-1SHA512\s0\fR.
Note: algorithm and hash names are case sensitive.
.Sp
If this option is not set then all signature algorithms supported by the
OpenSSL library are permissible.
.IP "\fBClientSignatureAlgorithms\fR" 4
.IX Item "ClientSignatureAlgorithms"
This sets the supported signature algorithms associated with client
authentication for \s-1TLS\s0 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.
.Sp
The syntax of \fBvalue\fR is identical to \fBSignatureAlgorithms\fR. If not set then
the value set for \fBSignatureAlgorithms\fR will be used instead.
.IP "\fBCurves\fR" 4
.IX Item "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.
.Sp
The \fBvalue\fR argument is a colon separated list of curves. The curve can be
either the \fB\s-1NIST\s0\fR name (e.g. \fBP\-256\fR) or an OpenSSL \s-1OID\s0 name (e.g
\&\fBprime256v1\fR). Curve names are case sensitive.
.IP "\fBECDHParameters\fR" 4
.IX Item "ECDHParameters"
This sets the temporary curve used for ephemeral \s-1ECDH\s0 modes. Only used by
servers
.Sp
The \fBvalue\fR argument is a curve name or the special value \fBAutomatic\fR which
picks an appropriate curve based on client and server preferences. The curve
can be either the \fB\s-1NIST\s0\fR name (e.g. \fBP\-256\fR) or an OpenSSL \s-1OID\s0 name
(e.g \fBprime256v1\fR). Curve names are case sensitive.
.IP "\fBProtocol\fR" 4
.IX Item "Protocol"
The supported versions of the \s-1SSL\s0 or \s-1TLS\s0 protocol.
.Sp
The \fBvalue\fR argument is a comma separated list of supported protocols to
enable or disable. If an protocol is preceded by \fB\-\fR that version is disabled.
Currently supported protocol values are \fBSSLv2\fR, \fBSSLv3\fR, \fBTLSv1\fR,
\&\fBTLSv1.1\fR and \fBTLSv1.2\fR.
All protocol versions other than \fBSSLv2\fR are enabled by default.
To avoid inadvertent enabling of \fBSSLv2\fR, when SSLv2 is disabled, it is not
possible to enable it via the \fBProtocol\fR command.
.IP "\fBOptions\fR" 4
.IX Item "Options"
The \fBvalue\fR argument is a comma separated list of various flags to set.
If a flag string is preceded \fB\-\fR it is disabled. See the
\&\fBSSL_CTX_set_options\fR function for more details of individual options.
.Sp
Each option is listed below. Where an operation is enabled by default
the \fB\-flag\fR syntax is needed to disable it.
.Sp
\&\fBSessionTicket\fR: session ticket support, enabled by default. Inverse of
\&\fB\s-1SSL_OP_NO_TICKET\s0\fR: that is \fB\-SessionTicket\fR is the same as setting
\&\fB\s-1SSL_OP_NO_TICKET\s0\fR.
.Sp
\&\fBCompression\fR: \s-1SSL/TLS\s0 compression support, enabled by default. Inverse
of \fB\s-1SSL_OP_NO_COMPRESSION\s0\fR.
.Sp
\&\fBEmptyFragments\fR: use empty fragments as a countermeasure against a
\&\s-1SSL 3.0/TLS 1.0\s0 protocol vulnerability affecting \s-1CBC\s0 ciphers. It
is set by default. Inverse of \fB\s-1SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS\s0\fR.
.Sp
\&\fBBugs\fR: enable various bug workarounds. Same as \fB\s-1SSL_OP_ALL\s0\fR.
.Sp
\&\fBDHSingle\fR: enable single use \s-1DH\s0 keys, set by default. Inverse of
\&\fB\s-1SSL_OP_DH_SINGLE\s0\fR. Only used by servers.
.Sp
\&\fBECDHSingle\fR enable single use \s-1ECDH\s0 keys, set by default. Inverse of
\&\fB\s-1SSL_OP_ECDH_SINGLE\s0\fR. Only used by servers.
.Sp
\&\fBServerPreference\fR 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
\&\fB\s-1SSL_OP_CIPHER_SERVER_PREFERENCE\s0\fR. Only used by servers.
.Sp
\&\fBNoResumptionOnRenegotiation\fR set
\&\fB\s-1SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION\s0\fR flag. Only used by servers.
.Sp
\&\fBUnsafeLegacyRenegotiation\fR permits the use of unsafe legacy renegotiation.
Equivalent to \fB\s-1SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION\s0\fR.
.Sp
\&\fBUnsafeLegacyServerConnect\fR permits the use of unsafe legacy renegotiation
for OpenSSL clients only. Equivalent to \fB\s-1SSL_OP_LEGACY_SERVER_CONNECT\s0\fR.
Set by default.
.SH "SUPPORTED COMMAND TYPES"
.IX Header "SUPPORTED COMMAND TYPES"
The function \fBSSL_CONF_cmd_value_type()\fR currently returns one of the following
types:
.IP "\fB\s-1SSL_CONF_TYPE_UNKNOWN\s0\fR" 4
.IX Item "SSL_CONF_TYPE_UNKNOWN"
The \fBcmd\fR string is unrecognised, this return value can be use to flag
syntax errors.
.IP "\fB\s-1SSL_CONF_TYPE_STRING\s0\fR" 4
.IX Item "SSL_CONF_TYPE_STRING"
The value is a string without any specific structure.
.IP "\fB\s-1SSL_CONF_TYPE_FILE\s0\fR" 4
.IX Item "SSL_CONF_TYPE_FILE"
The value is a file name.
.IP "\fB\s-1SSL_CONF_TYPE_DIR\s0\fR" 4
.IX Item "SSL_CONF_TYPE_DIR"
The value is a directory name.
.SH "NOTES"
.IX Header "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:
.PP
.Vb 2
\& SSL_CONF_cmd(ctx, "Protocol", "\-SSLv3");
\& SSL_CONF_cmd(ctx, userparam, uservalue);
.Ve
.PP
it will disable SSLv3 support by default but the user can override it. If
however the call sequence is:
.PP
.Vb 2
\& SSL_CONF_cmd(ctx, userparam, uservalue);
\& SSL_CONF_cmd(ctx, "Protocol", "\-SSLv3");
.Ve
.PP
then SSLv3 is \fBalways\fR disabled and attempt to override this by the user are
ignored.
.PP
By checking the return code of \fBSSL_CTX_cmd()\fR it is possible to query if a
given \fBcmd\fR is recognised, this is useful is \fBSSL_CTX_cmd()\fR values are
mixed with additional application specific operations.
.PP
For example an application might call \fBSSL_CTX_cmd()\fR and if it returns
\&\-2 (unrecognised command) continue with processing of application specific
commands.
.PP
Applications can also use \fBSSL_CTX_cmd()\fR to process command lines though the
utility function \fBSSL_CTX_cmd_argv()\fR is normally used instead. One way
to do this is to set the prefix to an appropriate value using
\&\fBSSL_CONF_CTX_set1_prefix()\fR, pass the current argument to \fBcmd\fR and the
following argument to \fBvalue\fR (which may be \s-1NULL\s0).
.PP
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 \fBSSL_CTX_cmd()\fR. If \-2 is
returned then \fBcmd\fR 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.
.PP
The function \fBSSL_CONF_cmd_value_type()\fR 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 \fB\s-1SSL_CONF_TYPE_FILE\s0\fR an application could translate a relative
pathname to an absolute pathname.
.SH "EXAMPLES"
.IX Header "EXAMPLES"
Set supported signature algorithms:
.PP
.Vb 1
\& SSL_CONF_cmd(ctx, "SignatureAlgorithms", "ECDSA+SHA256:RSA+SHA256:DSA+SHA256");
.Ve
.PP
Enable all protocols except SSLv3 and SSLv2:
.PP
.Vb 1
\& SSL_CONF_cmd(ctx, "Protocol", "ALL,\-SSLv3,\-SSLv2");
.Ve
.PP
Only enable TLSv1.2:
.PP
.Vb 1
\& SSL_CONF_cmd(ctx, "Protocol", "\-ALL,TLSv1.2");
.Ve
.PP
Disable \s-1TLS\s0 session tickets:
.PP
.Vb 1
\& SSL_CONF_cmd(ctx, "Options", "\-SessionTicket");
.Ve
.PP
Set supported curves to P\-256, P\-384:
.PP
.Vb 1
\& SSL_CONF_cmd(ctx, "Curves", "P\-256:P\-384");
.Ve
.PP
Set automatic support for any elliptic curve for key exchange:
.PP
.Vb 1
\& SSL_CONF_cmd(ctx, "ECDHParameters", "Automatic");
.Ve
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBSSL_CONF_cmd()\fR returns 1 if the value of \fBcmd\fR is recognised and \fBvalue\fR is
\&\fB\s-1NOT\s0\fR used and 2 if both \fBcmd\fR and \fBvalue\fR are used. In other words it
returns the number of arguments processed. This is useful when processing
command lines.
.PP
A return value of \-2 means \fBcmd\fR is not recognised.
.PP
A return value of \-3 means \fBcmd\fR is recognised and the command requires a
value but \fBvalue\fR is \s-1NULL.\s0
.PP
A return code of 0 indicates that both \fBcmd\fR and \fBvalue\fR are valid but an
error occurred attempting to perform the operation: for example due to an
error in the syntax of \fBvalue\fR in this case the error queue may provide
additional information.
.PP
\&\fBSSL_CONF_finish()\fR returns 1 for success and 0 for failure.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBSSL_CONF_CTX_new\fR\|(3),
\&\fBSSL_CONF_CTX_set_flags\fR\|(3),
\&\fBSSL_CONF_CTX_set1_prefix\fR\|(3),
\&\fBSSL_CONF_CTX_set_ssl_ctx\fR\|(3),
\&\fBSSL_CONF_cmd_argv\fR\|(3)
.SH "HISTORY"
.IX Header "HISTORY"
\&\fBSSL_CONF_cmd()\fR was first added to OpenSSL 1.0.2