1 /* script.c -- script routines for vlock, the VT locking program for linux
3 * This program is copyright (C) 2007 Frank Benkstein, and is free
4 * software which is freely distributable under the terms of the
5 * GNU General Public License version 2, included as the file COPYING in this
6 * distribution. It is NOT public domain software, and any
7 * redistribution not permitted by the GNU General Public License is
8 * expressly forbidden without prior written permission from
13 /* Scripts are executables that are run as unprivileged child processes of
14 * vlock. They communicate with vlock through stdin and stdout.
16 * When dependencies are retrieved they are launched once for each dependency
17 * and should print the names of the plugins they depend on on stdout one per
18 * line. The dependency requested is given as a single command line argument.
20 * In hook mode the script is called once with "hooks" as a single command line
21 * argument. It should not exit until its stdin closes. The hook that should
22 * be executed is written to its stdin on a single line.
24 * Currently there is no way for a script to communicate errors or even success
25 * to vlock. If it exits it will linger as a zombie until the plugin is
29 #if !defined(__FreeBSD__) && !defined(_GNU_SOURCE)
38 #include <sys/select.h>
51 static bool init_script(struct plugin
*p
);
52 static void destroy_script(struct plugin
*p
);
53 static bool call_script_hook(struct plugin
*p
, const char *hook_name
);
55 struct plugin_type
*script
= &(struct plugin_type
){
57 .destroy
= destroy_script
,
58 .call_hook
= call_script_hook
,
63 /* The pipe file descriptor that is connected to the script's stdin. */
65 /* The PID of the script. */
69 /* Get the dependency from the script. */
70 static bool get_dependency(const char *path
, const char *dependency_name
,
71 struct list
*dependency_list
);
72 /* Launch the script creating a new script_context. No error detection aborts
74 static struct script_context
*launch_script(const char *path
);
76 bool init_script(struct plugin
*p
)
80 if (asprintf(&path
, "%s/%s", VLOCK_SCRIPT_DIR
, p
->name
) < 0) {
85 /* Test for access. This must be done manually because vlock most likely
86 * runs as a setuid executable and would otherwise override restrictions.
88 * Also there is currently no error detection in case exec() fails later.
90 if (access(path
, X_OK
) < 0) {
97 /* Get the dependency information. */
98 for (size_t i
= 0; i
< nr_dependencies
; i
++)
99 if (!get_dependency(path
, dependency_names
[i
], p
->dependencies
[i
]))
102 /* Launch the script. */
103 p
->context
= launch_script(path
);
105 if (p
->context
!= NULL
) {
116 static void destroy_script(struct plugin
*p
)
118 struct script_context
*context
= p
->context
;
120 if (context
!= NULL
) {
121 /* Close the pipe. */
122 (void) close(context
->fd
);
124 /* Kill the child process. */
125 if (!wait_for_death(context
->pid
, 0, 500000L))
126 ensure_death(context
->pid
);
132 /* Invoke the hook by writing it on a single line to the scripts stdin. */
133 static bool call_script_hook(struct plugin
*s
, const char *hook_name
)
135 static const char newline
= '\n';
136 struct script_context
*context
= s
->context
;
137 ssize_t hook_name_length
= strlen(hook_name
);
139 struct sigaction act
;
140 struct sigaction oldact
;
142 /* When writing to a pipe when the read end is closed the kernel invariably
143 * sends SIGPIPE. Ignore it. */
144 (void) sigemptyset(&(act
.sa_mask
));
145 act
.sa_flags
= SA_RESTART
;
146 act
.sa_handler
= SIG_IGN
;
147 (void) sigaction(SIGPIPE
, &act
, &oldact
);
149 /* Send hook name and a newline through the pipe. */
150 length
= write(context
->fd
, hook_name
, hook_name_length
);
153 length
+= write(context
->fd
, &newline
, sizeof newline
);
155 /* Restore the previous SIGPIPE handler. */
156 (void) sigaction(SIGPIPE
, &oldact
, NULL
);
158 /* Scripts fail silently. */
159 return (length
== hook_name_length
+ 1);
162 static struct script_context
*launch_script(const char *path
)
165 struct script_context
*script
= malloc(sizeof *script
);
166 const char *argv
[] = { path
, "hooks", NULL
};
167 struct child_process child
= {
170 .stdin_fd
= REDIRECT_PIPE
,
171 .stdout_fd
= REDIRECT_DEV_NULL
,
172 .stderr_fd
= REDIRECT_DEV_NULL
,
179 if (!create_child(&child
)) {
186 script
->fd
= child
.stdin_fd
;
187 script
->pid
= child
.pid
;
189 fd_flags
= fcntl(script
->fd
, F_GETFL
, &fd_flags
);
191 if (fd_flags
!= -1) {
192 fd_flags
|= O_NONBLOCK
;
193 (void) fcntl(script
->fd
, F_SETFL
, fd_flags
);
199 static char *read_dependency(const char *path
, const char *dependency_name
);
200 static bool parse_dependency(char *data
, struct list
*dependency_list
);
202 /* Get the dependency from the script. */
203 static bool get_dependency(const char *path
, const char *dependency_name
,
204 struct list
*dependency_list
)
206 /* Read the dependency data. */
209 data
= read_dependency(path
, dependency_name
);
214 /* Parse the dependency data. */
215 bool result
= parse_dependency(data
, dependency_list
);
223 /* Read the dependency data by starting the script with the name of the
224 * dependency as a single command line argument. The script should then print
225 * the dependencies to its stdout one on per line. */
226 static char *read_dependency(const char *path
, const char *dependency_name
)
228 const char *argv
[] = { path
, dependency_name
, NULL
};
229 struct child_process child
= {
232 .stdin_fd
= REDIRECT_DEV_NULL
,
233 .stdout_fd
= REDIRECT_PIPE
,
234 .stderr_fd
= REDIRECT_DEV_NULL
,
237 struct timeval timeout
= {1, 0};
238 char *data
= calloc(1, sizeof *data
);
239 size_t data_length
= 0;
244 if (!create_child(&child
)) {
251 /* Read the dependency from the child. Reading fails if either the timeout
252 * elapses or more that LINE_MAX bytes are read. */
254 struct timeval t
= timeout
;
257 char buffer
[LINE_MAX
];
263 FD_SET(child
.stdout_fd
, &read_fds
);
265 /* t1 is before select. */
266 (void) gettimeofday(&t1
, NULL
);
268 if (select(child
.stdout_fd
+1, &read_fds
, NULL
, NULL
, &t
) != 1) {
274 /* t2 is after select. */
275 (void) gettimeofday(&t2
, NULL
);
277 /* Get the time that during select. */
278 timersub(&t2
, &t1
, &t2
);
280 /* This is very unlikely. */
281 if (timercmp(&t2
, &timeout
, >))
284 /* Reduce the timeout. */
285 timersub(&timeout
, &t2
, &timeout
);
287 /* Read dependency data from the script. */
288 length
= read(child
.stdout_fd
, buffer
, sizeof buffer
- 1);
290 /* Did the script close its stdin or exit? */
294 if (data_length
+length
+1 > LINE_MAX
) {
299 /* Grow the data string. */
300 data
= realloc(data
, data_length
+length
);
305 /* Append the buffer to the data string. */
306 strncpy(data
+data_length
, buffer
, length
);
307 data_length
+= length
;
310 /* Terminate the data string. */
311 data
[data_length
] = '\0';
313 /* Close the read end of the pipe. */
314 (void) close(child
.stdout_fd
);
315 /* Kill the script. */
316 if (!wait_for_death(child
.pid
, 0, 500000L))
317 ensure_death(child
.pid
);
325 (void) close(child
.stdout_fd
);
326 if (!wait_for_death(child
.pid
, 0, 500000L))
327 ensure_death(child
.pid
);
333 static bool parse_dependency(char *data
, struct list
*dependency_list
)
335 for (char *saveptr
, *token
= strtok_r(data
, " \r\n", &saveptr
);
337 token
= strtok_r(NULL
, " \r\n", &saveptr
)) {
338 char *s
= strdup(token
);
340 if (s
== NULL
|| !list_append(dependency_list
, s
))