path: root/lib/libcrypto/man/ENGINE_ctrl.3

.\" $OpenBSD: ENGINE_ctrl.3,v 1.5 2022/01/15 23:38:50 jsg Exp $
.\" content checked up to:
.\" OpenSSL ENGINE_add 1f13ad31 Dec 25 17:50:39 2017 +0800
.\"
.\" Copyright (c) 2018 Ingo Schwarze <schwarze@openbsd.org>
.\"
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.Dd $Mdocdate: January 15 2022 $
.Dt ENGINE_CTRL 3
.Os
.Sh NAME
.Nm ENGINE_ctrl ,
.Nm ENGINE_cmd_is_executable ,
.Nm ENGINE_ctrl_cmd ,
.Nm ENGINE_ctrl_cmd_string ,
.Nm ENGINE_set_ctrl_function ,
.Nm ENGINE_get_ctrl_function ,
.Nm ENGINE_set_cmd_defns ,
.Nm ENGINE_get_cmd_defns
.Nd control commands for ENGINE objects
.Sh SYNOPSIS
.In openssl/engine.h
.Ft int
.Fo ENGINE_ctrl
.Fa "ENGINE *e"
.Fa "int cmd"
.Fa "long i"
.Fa "void *p"
.Fa "void (*f)(void)"
.Fc
.Ft int
.Fo ENGINE_cmd_is_executable
.Fa "ENGINE *e"
.Fa "int cmd"
.Fc
.Ft int
.Fo ENGINE_ctrl_cmd
.Fa "ENGINE *e"
.Fa "const char *cmd_name"
.Fa "long i"
.Fa "void *p"
.Fa "void (*f)(void)"
.Fa "int cmd_optional"
.Fc
.Ft int
.Fo ENGINE_ctrl_cmd_string
.Fa "ENGINE *e"
.Fa "const char *cmd_name"
.Fa "const char *arg"
.Fa "int cmd_optional"
.Fc
.Ft typedef int
.Fo (*ENGINE_CTRL_FUNC_PTR)
.Fa "ENGINE *e"
.Fa "int cmd"
.Fa "long i"
.Fa "void *p"
.Fa "void (*f)(void)"
.Fc
.Ft int
.Fo ENGINE_set_ctrl_function
.Fa "ENGINE *e"
.Fa "ENGINE_CTRL_FUNC_PTR ctrl_f"
.Fc
.Ft ENGINE_CTRL_FUNC_PTR
.Fo ENGINE_get_ctrl_function
.Fa "const ENGINE *e"
.Fc
.Ft int
.Fo ENGINE_set_cmd_defns
.Fa "ENGINE *e"
.Fa "const ENGINE_CMD_DEFN *defns"
.Fc
.Ft const ENGINE_CMD_DEFN *
.Fo ENGINE_get_cmd_defns
.Fa "const ENGINE *e"
.Fc
.Sh DESCRIPTION
.Fn ENGINE_ctrl
calls the built-in or user-defined
.Fa cmd
for the engine
.Fa e ,
passing the arguments
.Fa i
and
.Fa p .
.Pp
User-defined commands can be used before
.Xr ENGINE_init 3
to provide data required for initialization
or at any time to modify the behaviour of an engine.
.Pp
Most built-in commands operate on user-defined commands installed with
.Fn ENGINE_set_cmd_defns ,
either using the
.Fa p
argument to indicate the user-defined command with the command name
.Fa cmd_name
or using the
.Fa i
argument to indicate the user-defined command with the command number
.Fa cmd_num .
The
.Fa cmd
arguments to call the built-in commands are as follows:
.Bl -tag -width Ds
.It Dv ENGINE_CTRL_GET_CMD_FLAGS
Return the
.Fa cmd_flags
of the user-defined command with the number
.Fa i ,
or a number less than or equal to 0 if an error occurs or
the command number does not exist.
A return value of 0 indicates failure if
.Fa e
is
.Dv NULL
or has a reference count of 0, or success if
.Fa e
is valid.
.It Dv ENGINE_CTRL_GET_CMD_FROM_NAME
Return the positive command number
of the user-defined command with the name
.Fa p ,
or a number less than or equal to 0 if an error occurs or no
matching name is found.
.It Dv ENGINE_CTRL_GET_DESC_FROM_CMD
Copy the description of the user-defined command with the number
.Fa i
into the buffer
.Fa p
and NUL-terminate it.
It is the responsibility of the caller to make sure that the buffer
.Fa p
is large enough, either by calling
.Dv ENGINE_CTRL_GET_DESC_LEN_FROM_CMD
first or using knowledge about the array passed to
.Fn ENGINE_set_cmd_defns .
The return value is the number of bytes written
.Em including
the terminating NUL byte, or a number less than or equal to 0
if an error occurs.
.It Dv ENGINE_CTRL_GET_DESC_LEN_FROM_CMD
Return the length in bytes
.Em excluding
the terminating NUL byte
of the description of the user-defined command with the number
.Fa i ,
or a number less than or equal to 0 if an error occurs.
A return value of 0 indicates failure if
.Fa e
is
.Dv NULL
or has a reference count of 0, or success if
.Fa e
is valid.
.It Dv ENGINE_CTRL_GET_FIRST_CMD_TYPE
Return the positive command number
of the first user-defined command installed with
.Fn ENGINE_set_cmd_defns
or a number less than or equal to 0 if an error occurs or no
user-defined command has been installed.
.It Dv ENGINE_CTRL_GET_NAME_FROM_CMD
Copy the name of the user-defined command with the number
.Fa i
into the buffer
.Fa p
and NUL-terminate it.
It is the responsibility of the caller to make sure that the buffer
.Fa p
is large enough, either by calling
.Dv ENGINE_CTRL_GET_NAME_LEN_FROM_CMD
first or using knowledge about the array passed to
.Fn ENGINE_set_cmd_defns .
The return value is the number of bytes written
.Em including
the terminating NUL byte, or a number less than or equal to 0
if an error occurs.
.It Dv ENGINE_CTRL_GET_NAME_LEN_FROM_CMD
Return the length in bytes
.Em excluding
the terminating NULL byte
of the name of the user-defined command with the number
.Fa i ,
or a number less than or equal to 0 if an error occurs.
A return value of 0 indicates failure if
.Fa e
is
.Dv NULL
or has a reference count of 0, or success if
.Fa e
is valid.
.It Dv ENGINE_CTRL_GET_NEXT_CMD_TYPE
Return the positive command number of the next user-defined command
after the user-defined command with the number
.Fa i ,
or a number less than or equal to 0 if an error occurs or if
.Fa i
is the last user-defined command.
Together with
.Dv ENGINE_CTRL_GET_FIRST_CMD_TYPE ,
this can be used to iterate the user-defined commands installed with
.Fn ENGINE_set_cmd_defns .
.It Dv ENGINE_CTRL_HAS_CTRL_FUNCTION
Return 1 if
.Fa e
has its own
.Fa ctrl_f
installed with
.Fn ENGINE_set_ctrl_function
or 0 otherwise.
.El
.Pp
.Fn ENGINE_ctrl_cmd
translates the
.Fa cmd_name
of a user-defined command to a
.Fa cmd
number and calls
.Fn ENGINE_ctrl
on it.
If
.Fa cmd_optional
is non-zero, lack of a
.Fa ctrl_f
in
.Fa e
and translation failure with
.Dv ENGINE_CTRL_GET_CMD_FROM_NAME
are considered success, and the command has no effect.
Otherwise, these problems cause
.Fn ENGINE_ctrl_cmd
to fail.
.Pp
Neither
.Fn ENGINE_ctrl
nor
.Fn ENGINE_ctrl_cmd
ever call the
.Fa f
callback, but merely pass it on as an argument to the engine-specific
.Fa ctrl_f
control function.
It is up to
.Fa ctrl_f
how to use it, or alternatively to ignore it as well.
.Pp
.Fn ENGINE_ctrl_cmd_string
translates the
.Fa cmd_name
of a user-defined command to a
.Fa cmd
number.
If that command has the
.Dv ENGINE_CMD_FLAG_NO_INPUT
flag set,
.Fa arg
must be
.Dv NULL
and
.Fn ENGINE_ctrl
is called with
.Fa i
set to 0 and
.Fa p
set to
.Dv NULL .
Otherwise,
.Fa arg
must not be
.Dv NULL .
If the command accepts string input,
.Fa i
is set to 0 and
.Fa arg
is passed as the
.Fa p
argument to
.Fn ENGINE_ctrl .
Otherwise,
.Fa arg
is converted with
.Xr strtol 3
and passed as the
.Fa i
argument to
.Fn ENGINE_ctrl ,
setting
.Fa p
to
.Dv NULL .
.Pp
.Fn ENGINE_set_ctrl_function
installs
.Fa ctrl_f
as the engine-specific control function for
.Fa e .
Future calls to
.Fn ENGINE_ctrl
will call that function, passing on their arguments unchanged, if the
.Fa cmd
is not built-in to the library or if the
.Dv ENGINE_FLAGS_MANUAL_CMD_CTRL
flag is set in
.Fa e .
Let the
.Fa ctrl_f
return positive values on success or negative values on failure.
Avoid return values of 0 because they cause dangerous ambiguity.
In particular,
.Fn ENGINE_ctrl_cmd
and
.Fn ENGINE_ctrl_cmd_string
cannot be used with user-defined commands
that may return 0 on success.
.Pp
.Fn ENGINE_set_cmd_defns
install an array of command definitions in
.Fa e .
.Pp
The structure
.Vt ENGINE_CMD_DEFN
has the following fields:
.Bl -tag -width Ds
.It Fa "unsigned int cmd_num"
A positive, unique, monotonically increasing command number.
Avoid using numbers below
.Dv ENGINE_CMD_BASE .
.It Fa "const char *cmd_name"
The unique name of the command.
.It Fa "const char *cmd_desc"
A short description of the command.
.It Fa "unsigned int cmd_flags"
The bitwise OR of zero or more of the following flags:
.Bl -tag -width Ds
.It Dv ENGINE_CMD_FLAG_NUMERIC
The command uses
.Fa i .
.It Dv ENGINE_CMD_FLAG_STRING
The command uses
.Fa p .
.It Dv ENGINE_CMD_FLAG_NO_INPUT
The command neither uses
.Fa i
nor
.Fa p .
.It Dv ENGINE_CMD_FLAG_INTERNAL
This flag has no effect and is only provided for compatibility.
.El
.El
.Pp
The last element of
.Fa defns
does not specify a command, but must have a
.Fa cmd_num
of 0 and a
.Fa cmd_name
of
.Dv NULL
to indicate the end of the array.
.Sh RETURN VALUES
For
.Fn ENGINE_ctrl ,
positive return values indicate success and negative return values
indicate failure.
The meaning of a zero return value depends on the particular
.Fa cmd
and may indicate both success and failure, which is pathetic.
.Pp
Regardless of the
.Fa cmd ,
.Fn ENGINE_ctrl
returns 0 if
.Fa e
is
.Dv NULL
or has a reference count of 0.
This is quite unfortunate for commands like
.Dv ENGINE_CTRL_GET_CMD_FLAGS
where 0 may indicate success, so make sure
.Fa e
is valid before issuing a control command.
.Pp
For built-in commands except
.Dv ENGINE_CTRL_HAS_CTRL_FUNCTION ,
.Fn ENGINE_ctrl
returns \-1 if
.Dv ENGINE_FLAGS_MANUAL_CMD_CTRL
is set but no
.Fa ctrl_f
has been installed with
.Fn ENGINE_set_ctrl_function .
.Pp
For commands that are not built in,
.Fn ENGINE_ctrl
returns 0 if no
.Fa ctrl_f
has been installed with
.Fn ENGINE_set_ctrl_function .
.Pp
.Fn ENGINE_cmd_is_executable
returns 1 if the user-defined
.Fa cmd
is executable and has at least one of the flags
.Dv ENGINE_CMD_FLAG_NUMERIC ,
.Dv ENGINE_CMD_FLAG_STRING ,
and
.Dv ENGINE_CMD_FLAG_NO_INPUT
set, or 0 otherwise.
.Pp
.Fn ENGINE_ctrl_cmd
and
.Fn ENGINE_ctrl_cmd_string
return 1 on success or 0 on error.
.Pp
.Fn ENGINE_set_ctrl_function
and
.Fn ENGINE_set_cmd_defns
always return 1.
.Pp
.Fn ENGINE_get_ctrl_function
returns a pointer to the function
.Fa ctrl_f
installed with
.Fn ENGINE_set_ctrl_function ,
or
.Dv NULL
if none has been installed.
.Pp
.Fn ENGINE_get_cmd_defns
returns the array of command definitions installed in
.Fa e
or
.Dv NULL
if none is installed.
.Sh SEE ALSO
.Xr ENGINE_add 3 ,
.Xr ENGINE_init 3 ,
.Xr ENGINE_new 3 ,
.Xr ENGINE_register_RSA 3 ,
.Xr ENGINE_set_flags 3 ,
.Xr ENGINE_set_RSA 3
.Sh HISTORY
.Fn ENGINE_ctrl ,
.Fn ENGINE_set_ctrl_function ,
and
.Fn ENGINE_get_ctrl_function
first appeared in OpenSSL 0.9.7 and have been available since
.Ox 2.9 .
.Pp
.Fn ENGINE_cmd_is_executable ,
.Fn ENGINE_ctrl_cmd ,
.Fn ENGINE_ctrl_cmd_string ,
.Fn ENGINE_set_cmd_defns ,
and
.Fn ENGINE_get_cmd_defns
first appeared in OpenSSL 0.9.7 and have been available since
.Ox 3.2 .