uiserver.texi
No OneTemporary
Actions

Size

23 KB

Subscribers

None

uiserver.texi
View Options

	@c uiserver.texi -- mode: texinfo; coding: latin-1; --
	@c Specification of the UI server protocol.
	@c To be included by gpgme.texi

	@node UI Server Protocol
	@appendix The GnuPG UI Server Protocol
	@cindex UI server
	@cindex user interface server


	This section specifies the protocol used between clients and a User
	Interface Server (UI server). This protocol helps to build a system
	where all cryptographic operations are done by a server and the server
	is responsible for all dialogs. Although @acronym{GPGME} has no direct
	support for this protocol it is believed that servers will utilize the
	@acronym{GPGME} library; thus having the specification included in this
	manual is an appropriate choice. This protocol should be referenced as
	`The GnuPG UI Server Protocol'.

	@noindent
	A server needs to implement these commands:@footnote{In all examples we
	assume that the connection has already been established; see the Assuan
	manual for details.}

	@menu
	* UI Server Encrypt:: Encrypt a message.
	* UI Server Sign:: Sign a message.
	* UI Server Decrypt:: Decrypt a message.
	* UI Server Verify:: Verify a message.
	* UI Server Set Input Files:: Specifying the input files to operate on.
	* UI Server Sign/Encrypt Files:: Encrypting and signing files.
	* UI Server Verify/Decrypt Files:: Decrypting and verifying files.
	* UI Server Import/Export Keys:: Managing certificates.
	* UI Server Checksum Files:: Create and verify checksums for files.
	* Miscellaneous UI Server Commands:: Commands not related to a specific operation.
	@end menu



	@node UI Server Encrypt
	@section UI Server: Encrypt a Message

	Before encryption can be done the recipients must be set using the
	command:

	@deffn Command RECIPIENT @var{string}

	Set the recipient for the encryption. @var{string} is an RFC-2822
	recipient name ("mailbox" as per section 3.4). This command may or may
	not check the recipient for validity right away; if it does not all
	recipients are expected to be checked at the time of the @code{ENCRYPT}
	command. All @code{RECIPIENT} commands are cumulative until a
	successful @code{ENCRYPT} command or until a @code{RESET} command.
	Linefeeds are obviously not allowed in @var{string} and should be folded
	into spaces (which are equivalent).
	@end deffn

	@noindent
	To tell the server the source and destination of the data, the next two
	commands are to be used:

	@deffn Command INPUT FD=@var{n}
	Set the file descriptor for the message to be encrypted to @var{n}. The
	message send to the server is binary encoded.

	GpgOL is a Windows only program, thus @var{n} is not a libc file
	descriptor but a regular system handle. Given that the Assuan
	connection works over a socket, it is not possible to use regular
	inheritance to make the file descriptor available to the server.
	Thus @code{DuplicateHandle} needs to be used to duplicate a handle
	to the server process. This is the reason that the server needs to
	implement the @code{GETINFO pid} command. Sending this command a second
	time replaces the file descriptor set by the last one.
	@c If @var{n} is not given, this commands uses the
	@c %last file descriptor passed to the application.
	@c %@xref{fun-assuan_sendfd, ,the assuan_sendfd function,assuan,the
	@c %Libassuan manual}, on how to do descriptor passing.
	@end deffn

	@deffn Command OUTPUT FD=@var{n} [--binary]
	Set the file descriptor to be used for the output (i.e. the encrypted
	message) to @var{n}. If the option @code{--binary} is given the
	output shall be in binary format; if not given, the output for OpenPGP
	needs to be ASCII armored and for CMS Base-64 encoded. For details on
	the file descriptor, see the @code{INPUT} command.
	@end deffn

	@noindent
	The setting of the recipients, the data source and destination may
	happen in any order, even intermixed. If this has been done the actual
	encryption operation is called using:

	@deffn Command ENCRYPT -@w{}-protocol=@var{name}

	This command reads the plaintext from the file descriptor set by the
	@code{INPUT} command, encrypts it and writes the ciphertext to the file
	descriptor set by the @code{OUTPUT} command. The server may (and
	should) overlap reading and writing. The recipients used for the
	encryption are all the recipients set so far. If any recipient is not
	usable the server should take appropriate measures to notify the user
	about the problem and may cancel the operation by returning an error
	code. The used file descriptors are void after this command; the
	recipient list is only cleared if the server returns success.

	@noindent
	Because GpgOL uses a streaming mode of operation the server is not
	allowed to auto select the protocol and must obey to the mandatory
	@var{protocol} parameter:

	@table @code
	@item OpenPGP
	Use the OpenPGP protocol (RFC-2440).
	@item CMS
	Use the CMS (PKCS#7) protocol (RFC-3852).
	@end table

	@end deffn

	To support automagically selection of the protocol depending on the
	selected keys, the server MAY implement the command:

	@deffn Command PREP_ENCRYPT [-@w{}-protocol=@var{name}] [-@w{}-expect-sign]

	This commands considers all recipients set so far and decides whether it
	is able to take input and start the actual encryption. This is kind of
	a dry-run @command{ENCRYPT} without requiring or using the input and
	output file descriptors. The server shall cache the result of any user
	selection to avoid asking this again when the actual @command{ENCRYPT}
	command is send. The @option{--protocol} option is optional; if it is
	not given, the server should allow the user to select the protocol to be
	used based on the recipients given or by any other means.

	If @option{--expect-sign} is given the server should expect that the
	message will also be signed and use this hint to present a unified
	recipient and signer selection dialog if possible and desired. A
	selected signer should then be cached for the expected SIGN command
	(which is expected in the same session but possible on another
	connection).

	If this command is given again before a successful @command{ENCRYPT}
	command, the second one takes effect.

	Before sending the OK response the server shall tell the client the
	protocol to be used (either the one given by the argument or the one
	selected by the user) by means of a status line:
	@end deffn

	@deffn {Status line} PROTOCOL @var{name}
	Advise the client to use the protocol @var{name} for the
	@command{ENCRYPT} command. The valid protocol names are listed under
	the description of the @command{ENCRYPT} command. The server shall emit
	exactly one PROTOCOL status line.
	@end deffn

	@noindent
	Here is an example of a complete encryption sequence; client lines are
	indicated by a @sc{c:}, server responses by @sc{c:}:

	@smallexample
	@group
	@clnt RESET
	@srvr OK
	@clnt RECIPIENT foo@@example.net
	@srvr OK
	@clnt RECIPIENT bar@@example.com
	@srvr OK
	@clnt PREP_ENCRYPT
	@srvr S PROTOCOL OpenPGP
	@srvr OK
	@clnt INPUT FD=17
	@srvr OK
	@clnt OUTPUT FD=18
	@srvr OK
	@clnt ENCRYPT
	@srvr OK
	@end group
	@end smallexample



	@node UI Server Sign
	@section UI Server: Sign a Message

	The server needs to implement opaque signing as well as detached
	signing. Due to the nature of OpenPGP messages it is always required to
	send the entire message to the server; sending just the hash is not
	possible. The following two commands are required to set the input and
	output file descriptors:

	@deffn Command INPUT FD=@var{n}
	Set the file descriptor for the message to be signed to @var{n}. The
	message send to the server is binary encoded. For details on the file
	descriptor, see the description of @code{INPUT} in the @code{ENCRYPT}
	section.
	@end deffn

	@deffn Command OUTPUT FD=@var{n} [--binary]
	Set the file descriptor to be used for the output. The output is
	either the complete signed message or in case of a detached signature
	just that detached signature. If the option @code{--binary} is given
	the output shall be in binary format; if not given, the output for
	OpenPGP needs to be ASCII armored and for CMS Base-64 encoded. For
	details on the file descriptor, see the @code{INPUT} command.
	@end deffn

	@noindent
	To allow the server the selection of a non-default signing key the
	client may optionally use the @code{SENDER} command, see @ref{command
	SENDER}.

	@noindent
	The signing operation is then initiated by:

	@deffn Command SIGN -@w{}-protocol=@var{name} [-@w{}-detached]
	Sign the data set with the @code{INPUT} command and write it to the sink
	set by OUTPUT. @var{name} is the signing protocol used for the
	message. For a description of the allowed protocols see the
	@code{ENCRYPT} command. With option @code{--detached} given, a detached
	signature is created; this is actually the usual way the command is
	used.
	@end deffn

	@noindent
	The client expects the server to send at least this status information
	before the final OK response:

	@deffn {Status line} MICALG @var{string}
	The @var{string} represents the hash algorithm used to create the
	signature. It is used with MOSS style signature messages and defined by
	PGP/MIME (RFC-3156) and S/MIME (RFC-3851). The GPGME library has a
	supporting function @code{gpgme_hash_algo_name} to return the algorithm
	name as a string. This string needs to be lowercased and for OpenPGP
	prefixed with "@code{pgp-}".
	@end deffn



	@node UI Server Decrypt
	@section UI Server: Decrypt a Message

	Decryption may include the verification of OpenPGP messages. This is
	due to the often used combined signing/encryption modus of OpenPGP. The
	client may pass an option to the server to inhibit the signature
	verification. The following two commands are required to set the input
	and output file descriptors:

	@deffn Command INPUT FD=@var{n}
	Set the file descriptor for the message to be decrypted to @var{n}. The
	message send to the server is either binary encoded or --- in the case
	of OpenPGP --- ASCII armored. For details on the file descriptor, see
	the description of @code{INPUT} in the @code{ENCRYPT} section.
	@end deffn

	@deffn Command OUTPUT FD=@var{n}
	Set the file descriptor to be used for the output. The output is binary
	encoded. For details on the file descriptor, see the description of
	@code{INPUT} in the @code{ENCRYPT} section.
	@end deffn

	@noindent
	The decryption is started with the command:

	@deffn Command DECRYPT -@w{}-protocol=@var{name} [-@w{}-no-verify]
	@var{name} is the encryption protocol used for the message. For a
	description of the allowed protocols see the @code{ENCRYPT} command.
	This argument is mandatory. If the option @option{--no-verify} is given,
	the server should not try to verify a signature, in case the input data
	is an OpenPGP combined message.
	@end deffn


	@node UI Server Verify
	@section UI Server: Verify a Message

	The server needs to support the verification of opaque signatures as
	well as detached signatures. The kind of input sources controls what
	kind message is to be verified.

	@deffn Command MESSAGE FD=@var{n}
	This command is used with detached signatures to set the file descriptor
	for the signed data to @var{n}. The data is binary encoded (used
	verbatim). For details on the file descriptor, see the description of
	@code{INPUT} in the @code{ENCRYPT} section.
	@end deffn

	@deffn Command INPUT FD=@var{n}
	Set the file descriptor for the opaque message or the signature part of
	a detached signature to @var{n}. The message send to the server is
	either binary encoded or -- in the case of OpenPGP -- ASCII armored.
	For details on the file descriptor, see the description of @code{INPUT}
	in the @code{ENCRYPT} section.
	@end deffn

	@deffn Command OUTPUT FD=@var{n}
	Set the file descriptor to be used for the output. The output is binary
	encoded and only used for opaque signatures. For details on the file
	descriptor, see the description of @code{INPUT} in the @code{ENCRYPT}
	section.
	@end deffn

	@noindent
	The verification is then started using:

	@deffn Command VERIFY -@w{}-protocol=@var{name} [-@w{}-silent]
	@var{name} is the signing protocol used for the message. For a
	description of the allowed protocols see the @code{ENCRYPT} command.
	This argument is mandatory. Depending on the combination of
	@code{MESSAGE} @code{INPUT} and @code{OUTPUT} commands, the server needs
	to select the appropriate verification mode:

	@table @asis
	@item MESSAGE and INPUT
	This indicates a detached signature. Output data is not applicable.
	@item INPUT
	This indicates an opaque signature. As no output command has been given,
	the server is only required to check the signature.
	@item INPUT and OUTPUT
	This indicates an opaque signature. The server shall write the signed
	data to the file descriptor set by the output command. This data shall
	even be written if the signatures can't be verified.
	@end table
	@end deffn

	With @option{--silent} the server shall not display any dialog; this is
	for example used by the client to get the content of opaque signed
	messages. The client expects the server to send at least this status
	information before the final OK response:

	@deffn {Status line} SIGSTATUS @var{flag} @var{displaystring}
	Returns the status for the signature and a short string explaining the
	status. Valid values for @var{flag} are:

	@table @code
	@item none
	The message has a signature but it could not not be verified due to a
	missing key.
	@item green
	The signature is fully valid.
	@item yellow
	The signature is valid but additional information was shown regarding the
	validity of the key.
	@item red
	The signature is not valid.
	@end table

	@var{displaystring} is a percent-and-plus-encoded string with a short
	human readable description of the status. For example

	@smallexample
	S SIGSTATUS green Good+signature+from+Keith+Moon+<keith@@example.net>
	@end smallexample

	Note that this string needs to fit into an Assuan line and should be
	short enough to be displayed as short one-liner on the clients window.
	As usual the encoding of this string is UTF-8 and it should be send in
	its translated form.

	The server shall send one status line for every signature found on the
	message.


	@end deffn


	@node UI Server Set Input Files
	@section UI Server: Specifying the input files to operate on.

	All file related UI server commands operate on a number of input files
	or directories, specified by one or more @code{FILE} commands:

	@deffn Command FILE @var{name} [--continued]
	Add the file or directory @var{name} to the list of pathnames to be
	processed by the server. The parameter @var{name} must be an absolute
	path name (including the drive letter) and is percent espaced (in
	particular, the characters %, = and white space characters are always
	escaped). The option @code{--continued} is present for all but the
	last @code{FILE} command.
	@end deffn


	@node UI Server Sign/Encrypt Files
	@section UI Server: Encrypting and signing files.

	First, the input files need to be specified by one or more
	@code{FILE} commands. Afterwards, the actual operation is requested:

	@deffn Command ENCRYPT_FILES --nohup
	@deffnx Command SIGN_FILES --nohup
	@deffnx Command ENCRYPT_SIGN_FILES --nohup
	Request that the files specified by @code{FILE} are encrypted and/or
	signed. The command selects the default action. The UI server may
	allow the user to change this default afterwards interactively, and
	even abort the operation or complete it only on some of the selected
	files and directories.

	What it means to encrypt or sign a file or directory is specific to
	the preferences of the user, the functionality the UI server provides,
	and the selected protocol. Typically, for each input file a new file
	is created under the original filename plus a protocol specific
	extension (like @code{.gpg} or @code{.sig}), which contain the
	encrypted/signed file or a detached signature. For directories, the
	server may offer multiple options to the user (for example ignore or
	process recursively).

	The @code{ENCRYPT_SIGN_FILES} command requests a combined sign and
	encrypt operation. It may not be available for all protocols (for
	example, it is available for OpenPGP but not for CMS).

	The option @code{--nohup} is mandatory. It is currently unspecified
	what should happen if @code{--nohup} is not present. Because
	@code{--nohup} is present, the server always returns @code{OK}
	promptly, and completes the operation asynchronously.
	@end deffn


	@node UI Server Verify/Decrypt Files
	@section UI Server: Decrypting and verifying files.

	First, the input files need to be specified by one or more
	@code{FILE} commands. Afterwards, the actual operation is requested:

	@deffn Command DECRYPT_FILES --nohup
	@deffnx Command VERIFY_FILES --nohup
	@deffnx Command DECRYPT_VERIFY_FILES --nohup
	Request that the files specified by @code{FILE} are decrypted and/or
	verified. The command selects the default action. The UI server may
	allow the user to change this default afterwards interactively, and
	even abort the operation or complete it only on some of the selected
	files and directories.

	What it means to decrypt or verify a file or directory is specific to
	the preferences of the user, the functionality the UI server provides,
	and the selected protocol. Typically, for decryption, a new file is
	created for each input file under the original filename minus a
	protocol specific extension (like @code{.gpg}) which contains the
	original plaintext. For verification a status is displayed for each
	signed input file, indicating if it is signed, and if yes, if the
	signature is valid. For files that are signed and encrypted, the
	@code{VERIFY} command transiently decrypts the file to verify the
	enclosed signature. For directories, the server may offer multiple
	options to the user (for example ignore or process recursively).

	The option @code{--nohup} is mandatory. It is currently unspecified
	what should happen if @code{--nohup} is not present. Because
	@code{--nohup} is present, the server always returns @code{OK}
	promptly, and completes the operation asynchronously.
	@end deffn


	@node UI Server Import/Export Keys
	@section UI Server: Managing certificates.

	First, the input files need to be specified by one or more
	@code{FILE} commands. Afterwards, the actual operation is requested:

	@deffn Command IMPORT_FILES --nohup
	Request that the certificates contained in the files specified by
	@code{FILE} are imported into the local certificate databases.

	For directories, the server may offer multiple options to the user
	(for example ignore or process recursively).

	The option @code{--nohup} is mandatory. It is currently unspecified
	what should happen if @code{--nohup} is not present. Because
	@code{--nohup} is present, the server always returns @code{OK}
	promptly, and completes the operation asynchronously.
	@end deffn

	FIXME: It may be nice to support an @code{EXPORT} command as well,
	which is enabled by the context menu of the background of a directory.


	@node UI Server Checksum Files
	@section UI Server: Create and verify checksums for files.

	First, the input files need to be specified by one or more
	@code{FILE} commands. Afterwards, the actual operation is requested:

	@deffn Command CHECKSUM_CREATE_FILES --nohup
	Request that checksums are created for the files specifed by
	@code{FILE}. The choice of checksum algorithm and the destination
	storage and format for the created checksums depend on the preferences
	of the user and the functionality provided by the UI server. For
	directories, the server may offer multiple options to the user (for
	example ignore or process recursively).

	The option @code{--nohup} is mandatory. It is currently unspecified
	what should happen if @code{--nohup} is not present. Because
	@code{--nohup} is present, the server always returns @code{OK}
	promptly, and completes the operation asynchronously.
	@end deffn


	@deffn Command CHECKSUM_VERIFY_FILES --nohup
	Request that checksums are created for the files specifed by
	@code{FILE} and verified against previously created and stored
	checksums. The choice of checksum algorithm and the source storage
	and format for previously created checksums depend on the preferences
	of the user and the functionality provided by the UI server. For
	directories, the server may offer multiple options to the user (for
	example ignore or process recursively).

	If the source storage of previously created checksums is available to
	the user through the Windows shell, this command may also accept such
	checksum files as @code{FILE} arguments. In this case, the UI server
	should instead verify the checksum of the referenced files as if they
	were given as INPUT files.

	The option @code{--nohup} is mandatory. It is currently unspecified
	what should happen if @code{--nohup} is not present. Because
	@code{--nohup} is present, the server always returns @code{OK}
	promptly, and completes the operation asynchronously.
	@end deffn




	@c
	@c M I S C E L L A N E O U S C O M M A N D S
	@c
	@node Miscellaneous UI Server Commands
	@section Miscellaneous UI Server Commands

	The server needs to implement the following commands which are not
	related to a specific command:

	@deffn Command GETINFO @var{what}
	This is a multi purpose command, commonly used to return a variety of
	information. The required subcommands as described by the @var{what}
	parameter are:

	@table @code
	@item pid
	Return the process id of the server in decimal notation using an Assuan
	data line.
	@end table
	@end deffn


	@noindent
	To allow the server to pop up the windows in the correct relation to the
	client, the client is advised to tell the server by sending the option:

	@deffn {Command option} window-id @var{number}
	The @var{number} represents the native window ID of the clients current
	window. On Windows systems this is a windows handle (@code{HWND}) and
	on X11 systems it is the @code{X Window ID}. The number needs to be
	given as a hexadecimal value so that it is easier to convey pointer
	values (e.g. @code{HWND}).
	@end deffn


	@noindent
	A client may want to fire up the certificate manager of the server. To
	do this it uses the Assuan command:

	@deffn Command START_KEYMANAGER
	The server shall pop up the main window of the key manager (aka
	certificate manager). The client expects that the key manager is brought
	into the foregound and that this command immediatley returns (does not
	wait until the key manager has been fully brought up).
	@end deffn

	@noindent
	A client may want to fire up the configuration dialog of the server. To
	do this it uses the Assuan command:

	@deffn Command START_CONFDIALOG
	The server shall pop up its configuration dialog. The client expects
	that this dialog is brought into the foregound and that this command
	immediatley returns (i.e. it does not wait until the dialog has been
	fully brought up).
	@end deffn

	@anchor{command SENDER}
	@noindent
	When doing an operation on a mail, it is useful to let the server know
	the address of the sender:

	@deffn Command SENDER [-@w{}-info] [-@w{}-protocol=@var{name}] @var{email}
	@var{email} is the plain ASCII encoded address ("addr-spec" as per
	RFC-2822) enclosed in angle brackets. The address set with this command
	is valid until a successful completion of the operation or until a
	@code{RESET} command. A second command overrides the effect of the
	first one; if @var{email} is not given and @option{--info} is not used,
	the server shall use the default signing key.

	If option @option{--info} is not given, the server shall also suggest a
	protocol to use for signing. The client may use this suggested protocol
	on its own discretion. The same status line as with PREP_ENCRYPT is
	used for this.

	The option @option{--protocol} may be used to give the server a hint on
	which signing protocol should be preferred.
	@end deffn

	@noindent
	To allow the UI-server to visually identify a running operation or to
	associate operations the server MAY support the command:

	@deffn Command SESSION @var{number} [@var{string}]
	The @var{number} is an arbitrary value, a server may use to associate
	simultaneous running sessions. It is a 32 bit unsigned integer with
	@code{0} as a special value indicating that no session association shall
	be done.

	If @var{string} is given, the server may use this as the title of a
	window or, in the case of an email operation, to extract the sender's
	address. The string may contain spaces; thus no plus-escaping is used.

	This command may be used at any time and overrides the effect of the
	last command. A @code{RESET} undoes the effect of this command.

	@end deffn

File Metadata

Mime Type: text/plain
Expires: Mon, Dec 23, 2:12 PM (16 h, 46 m)
Storage Engine: local-disk
Storage Format: Raw Data
Storage Handle: f9/c9/c31c2a538317a9a0f26837649d62

uiserver.texiNo OneTemporaryActions

uiserver.texiView Options

File Metadata

Event Timeline

uiserver.texi
No OneTemporary
Actions

uiserver.texi
View Options