1 The server uses a protocol provided by libassuan to communicate with the
2 client. An OK response is returned when a command succeeds or ERR along with
3 an error code and description, if not. When a command requests data for
4 retrieval (e.g., GET) the output is prefixed with D then a single SPACE then
5 the actual data followed by a response. Read the libassuan docs for more info
11 OPEN <filename> [<key>]
12 Opens <filename> using <key>. If the filename is not found on the
13 file-system, then a new document will be created. If the file is found, it
14 is looked for in the file cache for an existing key. When found and no key
15 was specified, the cached key will be used for decryption (if encrypted).
16 When not found, pinentry(1) will be used to retrieve the key (see OPTIONS
17 below). You can also open a different file using the same connection. When
18 using an empty or NULL key and you want to avoid the pinentry dialog, set
19 PINENTRY to 0 (see OPTIONS below).
23 Writes the XML document to disk. The file written to is the file that was
24 opened using the OPEN command. If <key> is not specified then the
25 currently cached key will be used. If the file is a new file or the file
26 isn't found in the file cache, <key> will be used. If <key> is not
27 specified then pinentry(1) will be used to retrieve the key (see OPTIONS
28 below). If you want to use and empty key and want to avoid the pinentry
29 dialog, set PINENTRY to 0 (see OPTIONS below).
33 An OK response is returned if the specified file is found in the file
37 CLEARCACHE [<filename>]
38 Clears a file cache entry. This will forget the timeout and key for all or
39 the specified file. Always returns an OK response.
42 CACHETIMEOUT <seconds> <filename>
43 Specify the number of seconds the specified file will be cached. -1 will
44 keep the cache entry forever, 0 will require the key each time the OPEN or
45 SAVE commands are used. Also see the "cache_timeout" configuration
46 parameter. Returns ERR if the filename isn't cached or if the timeout is
47 invalid. OK otherwise.
50 LIST [[!]element[<TAB>[!]element[...]]]
51 If no element path is given then a list of root elements is returned with
52 the data response. If given, then all reachable elements for the
53 specified element path are returned. Each element in the path is prefixed
54 with the literal '!' character when the element contains no "target"
55 attribute (See THE TARGET ATTRIBUTE below).
58 REALPATH [!]element[<TAB>[!]element[...]]
59 Resolves all "target" attributes of the specified element path and returns
60 the result with a data response.
63 STORE [!]element[[<TAB>[!]element[...]]<TAB>[content]]
64 Creates a new element tree or modifies the content of an existing element
65 path. If only a single element is specified, a new root element is
66 created. Otherwise, elements are TAB delimited and the content will be set
67 to the last TAB delimited argument. If no content is specified after the
68 last TAB then the content for the last specified element will be removed
69 or empty if creating a new element.
71 The only restriction of element names is that they not begin with a
72 punctuation character (the literal '!' character is an exception) or digit
73 and not contain any whitespace. There is no whitespace between the TAB
74 delimited elements. It is recommended that the value be base 64 encoded to
75 prevent XML and pwmd parsing errors.
77 PWMD reads the element path from the client via the Assuan INQUIRE
78 protocol response. The STORE command is sent by itself without arguments,
79 then the server responds with INQUIRE. The client then sends the element
80 path prefixed with a "D " data response. The element path may extend
81 multiple lines but each must be prefixed with the data "D " response. When
82 finished, the client sends "END" on an empty line. This is needed so an
83 element path and value can be more than 1000 bytes long, the Assuan
87 DELETE [!]element[<TAB>[!]element[...]]
88 Removes an element tree from the specified element path.
91 GET [!]element[<TAB>[!]element[...]]
92 Retrieves the content or text node of the specified element path. The data
93 is returned with a data response.
96 ATTR SET|GET|DELETE|LIST [<attribute>] [!]<arg1> [!][arg2]
97 ATTR SET attribute [!]element[<TAB>[!]element[...]] attribute_value
98 Stores or updates an attribute value of an element path.
100 ATTR DELETE attribute [!]element[<TAB>[!]element[...]]
101 Removes an attribute from an element path.
103 ATTR LIST [!]element[<TAB>[!]element[...]]
104 Gets a list of attributes from an element path.
106 ATTR GET attribute [!]element[<TAB>[!]element[...]]
107 Gets the value of an attribute from an element path.
109 The "name" attribute (case sensitive) cannot be removed with ATTR DELETE
110 if the element path is the root element. Although it can be SET to change
111 the root element name.
113 Also see THE TARGET ATTRIBUTE below.
116 XPATH <expression>[<TAB>[value]]
117 Evaluates an XPath expression. If no value argument is specified, it is
118 assumed the expression is a request to return a result. Otherwise, the
119 result is set to the value argument and the document is updated. If there
120 is no value after the <TAB> character, the value is assumed to be empty
121 and the document is updated.
124 IMPORT [!]element[<TAB>[!]element[...]] <content>
125 Like the STORE command (an INQUIRE), but the content argument is raw XML
126 data. The content is created as a child of the specified element path. If
127 an element of the element path does not exist, it is created.
129 Note that the new content must begin with an element node and not a text
130 node. Also note that an existing child node of the same element name as
131 the root node of the imported content will be overwritten.
135 Shows the in memory XML document with indenting. To dump a specific
136 element tree, use the XPATH command.
140 Locks the mutex associated with the opened file. This prevents other
141 clients from sending commands to the same opened file until the client
142 that sent this command either disconnects or sends the UNLOCK command.
146 Unlocks the mutex which was locked with the LOCK command.
150 Retrieves the process id of the server.
153 GETCONFIG [filename] <parameter>
154 Returns the value of a pwmd configuration variable with a data response.
155 If no file is open then the specified files value or the default ("global"
156 section) will be returned. If there is no such parameter defined,
157 GPG_ERR_NO_VALUE is returned.
160 OPTION <NAME>=<VALUE>
161 Sets an option NAME to VALUE. See OPTIONS below for available options.
165 Closes the connection disconnecting the client. Unless the SAVE command
166 had been sent, any changes to the document will be lost.
171 Commands that require a key that is neither cached nor specified will use
172 pinentry(1) to retrieve the key. Pinentry options can be set with the OPTION
173 command followed by the option name and value. Below are the available
176 NAME VALUE Description
177 ---------|----------|----------------------------------------------------
178 PINENTRY 0|1 When 0, disable use of pinentry. The default is 1.
179 TIMEOUT <integer> The number of seconds before the pinentry process
180 will terminate while waiting for a password. The
181 default is 20, 0 disables.
182 PATH <string> Full path to the pinentry binary. The default is
183 specified at compile time (/usr/bin/pinentry).
184 TTYNAME <string> Same as the --ttyname option to pinentry(1).
185 TTYTYPE <string> Same as the --ttytype option to pinentry(1).
186 DISPLAY <string> Same as the --display option to pinentry(1).
187 LC_CTYPE <string> Same as the --lc-ctype option to pinentry(1).
188 LC_MESSAGES <string> Same as the --lc-messages option to pinentry(1).
189 TITLE <string> Sets the title string of the dialog.
190 PROMPT <string> Sets the prompt string of the dialog.
191 DESC <string> Sets the error or description string of the dialog.
192 ITERATIONS <integer> The number of encryption iterations to do when the
193 SAVE command is sent. When used, the configured
194 value will be updated to this value for the opened
195 file, or the "global" default if no file has been
196 opened yet. When setting this option before opening
197 a file, this option is reset to the files setting
198 after opening. The CONFIG status message is sent
199 after receiving this command.
201 When pinentry is used with the SAVE command the key will be asked for
202 confirmation. If the confirmation fails, the process is started over again
203 until either the keys match or until Cancel is selected. The OPEN command will
204 only ask for the key once without retrying on failure. It is up to the client
205 to retry the OPEN command. Empty keys are allowed.
207 There is also a CLIENT option that contains other sub-options. The format is
208 OPTION CLIENT NAME=VALUE, where NAME is one of:
210 NAME VALUE Description
211 ---------|----------|----------------------------------------------------
212 NAME <string> Associates the thread ID of the connection with the
213 specified textual representation. Useful for
214 debugging log messages.
219 Some commands send a status message to the client when successful or as a
220 progress indicator. Status messages begin with a KEYWORD (see below) followed
221 by the status description. What messages are sent, and how often, depend on
222 configuration settings:
225 --------------------------------
244 KEYWORD OUTPUT FORMAT
245 ---------------------------------
246 CACHE <slots used> <slots available>
247 Sent to each client after the file cache changes.
248 ENCRYPT <iterations so far> <total iterations>
249 DECRYPT <iterations so far> <total iterations>
250 COMPRESS <bytes so far> <total bytes>
251 DECOMPRESS <bytes so far> <total bytes>
252 LOCKED When another thread owns the file/key cache mutex
253 lock, this is sent at some interval and the thread
254 will block until the lock can be obtained.
255 KEEPALIVE Sent to each client after every configured amount of
256 seconds. This lets the client know that the connection
257 is still active for commands that take a while to
259 CONFIG Sent to each client after the configuration file has
260 been reloaded or has had a value changed.
261 CLIENTS Sent to each client after a client connects or
267 There is a special attribute "target" (case sensitive) that can be set with
268 ATTR SET. The value of this attribute is an element path that is located
269 somewhere else in the XML document and are alot like how XPath treats
270 entities, but are needed do to how pwmd commands are implemented. The syntax
273 ATTR SET target [!]element[<TAB>[!]element[..]] [!]element[<TAB>[!]element[..]]
274 arg1^^^^^^^^^^^^^^^^^^^^^^^^^^^ arg2^^^^^^^^^^^^^^^^^^^^^^^^^^^
276 If the element path of the "target" attribute (arg1) doesn't exist, it is
277 created. This is the only time the ATTR command will create elements.
279 When a protocol command requests <arg1> as the element path, the remaining
280 elements after the element with the "target" attribute will be appended to
281 <arg2>. This is useful if you have elements that share the same data. If the
282 target is modified, the other elements "pointing" to the target will have the
283 same content. To get the real or literal element and ignore any "target"
284 attributes, prefix an element with a '!' character. Here's an example:
288 C> D host1<TAB>username<TAB>original username
293 C> D host2<TAB>smtp<TAB>username<TAB>someuser
296 C> ATTR SET target host1<TAB>username host2<TAB>smtp<TAB>username
299 Now host1's "target" attribute will be used:
301 C> GET host1<TAB>username
305 If you want host1's username, prefix the element of the "target" attribute
308 C> GET host1<TAB>!username
309 S> D original username
312 The target value (arg2) element can also have a "target" attribute:
314 C> ATTR SET target new_account host1
316 C> GET new_account<TAB>username
320 The value of the "target" attribute may also be prefixed with a '!' to set the
321 target to the actual element path and not a target of the element path:
323 C> ATTR DELETE target !new_account
325 C> ATTR SET target new_account<TAB>username host1<TAB>!username
327 C> GET new_account<TAB>username
328 S> D original username
331 The "target" attribute is considered for all commands that support an element
332 path. If the target element has been renamed or deleted afterwards, the
335 Clients should be careful of creating target loops. See the "recursion_depth"
336 configuration parameter for details.
339 XML DOCUMENT STRUCTURE
340 ----------------------
341 When importing an XML data file with the -I command line option, the document
342 should have the following DTD:
344 <?xml version="1.0"?>
346 <!ELEMENT accounts (account*)>
347 <!ATTLIST account name CDATA #REQUIRED>
350 "accounts" is the document root element while each root element mentioned in
351 the protocol commands use the "account" element. So if you have a root element
352 "isp" to be shown with the LIST command ("LIST isp"), the document structure
361 The "accounts" and "account" elements are really only placeholders for the
362 element tree and probably should have been named "roots" and "root". The data
363 or content for every element node can really be anything and the server should
364 have been called xmld instead of pwmd.
366 The DUMP command can be useful to show the current document structure.
371 The key cache is protected with a mutex and is locked with each access. Each
372 cache entry also contains a mutex for the opened file and a reference count
373 which is adjusted each time a client connects or disconnects. This allows
374 client A to issue commands that aren't related to the file opened by client B.
375 The refcount is needed to prevent the mutex being overwritten when the entry
376 needs to be reset (CACHETIMEOUT for example) and there are any clients
379 The client_thread() uses an event to wait for the client FD to become ready
380 for reading. When ready, it uses the libassuan external IO loop functions to
381 prevent blocking letting other threads do their work.
383 When a key is required for the OPEN or SAVE commands, and OPTION PINENTRY=1,
384 pinentry(1) is used to retrieve the key. This is done by creating a pipe()
385 with the client_thread(), then pth_fork()'s the pinentry process which will
386 write the key or error to the pipe that client_thread() will read from. After
387 the read, the pinentry will have exited and client_thread() calls the
388 finalization function for the original command.
390 The KEEPALIVE status message is a PTH_EVENT_TIME event from server_loop(). It
391 uses a pth_msgport_t to write to other client threads. This is the same for
392 the CACHE and CONFIG status messages, except that pth_msgport_put() is called
393 from a client thread and sent to all other clients too. Each client thread
394 uses an PTH_EVENT_MSG event to wait for these messages.
396 ------------- ---------------
397 [server_loop]-_-_-_-[accept_thread]
398 ------------- ---------------
400 --------------------- ---------------
401 [adjust_timer_thread] [client_thread]<----------=====
402 --------------------- --------------- | | | =
404 ------------------ [command] | | =
405 [command finalize] --------- | | = pipe()
406 ------------------ | | | | =
418 There is also a library libpwmd which makes it easy for applications to use
419 the server. It supports it's own key retrieval and asynchronous interaction
420 with pwmd. It also includes a command line client for sending commands to
423 The latest version of both pwmd and libpwmd can be obtained from
424 http://bjk.sourceforge.net/pwmd/. Feel free to send me any questions, bug
425 reports, patches or feature requests.
427 Ben Kibbey <bjk@luxsci.net>