1 /*****************************************************************************
2 *
3 * Nagios run command utilities
4 *
5 * License: GPL
6 * Copyright (c) 2005-2006 Nagios Plugins Development Team
7 *
8 * Last Modified: $Date$
9 *
10 * Description :
11 *
12 * A simple interface to executing programs from other programs, using an
13 * optimized and safe popen()-like implementation. It is considered safe
14 * in that no shell needs to be spawned and the environment passed to the
15 * execve()'d program is essentially empty.
16 *
17 * The code in this file is a derivative of popen.c which in turn was taken
18 * from "Advanced Programming for the Unix Environment" by W. Richard Stevens.
19 *
20 * Care has been taken to make sure the functions are async-safe. The one
21 * function which isn't is cmd_init() which it doesn't make sense to
22 * call twice anyway, so the api as a whole should be considered async-safe.
23 *
24 *
25 * This program is free software: you can redistribute it and/or modify
26 * it under the terms of the GNU General Public License as published by
27 * the Free Software Foundation, either version 3 of the License, or
28 * (at your option) any later version.
29 *
30 * This program is distributed in the hope that it will be useful,
31 * but WITHOUT ANY WARRANTY; without even the implied warranty of
32 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
33 * GNU General Public License for more details.
34 *
35 * You should have received a copy of the GNU General Public License
36 * along with this program. If not, see <http://www.gnu.org/licenses/>.
37 *
38 * $Id$
39 *
40 *****************************************************************************/
42 #define NAGIOSPLUG_API_C 1
44 /** includes **/
45 #include "common.h"
46 #include "utils_cmd.h"
47 #include "utils_base.h"
49 #ifdef HAVE_SYS_WAIT_H
50 # include <sys/wait.h>
51 #endif
53 /** macros **/
54 #ifndef WEXITSTATUS
55 # define WEXITSTATUS(stat_val) ((unsigned)(stat_val) >> 8)
56 #endif
58 #ifndef WIFEXITED
59 # define WIFEXITED(stat_val) (((stat_val) & 255) == 0)
60 #endif
62 /* 4.3BSD Reno <signal.h> doesn't define SIG_ERR */
63 #if defined(SIG_IGN) && !defined(SIG_ERR)
64 # define SIG_ERR ((Sigfunc *)-1)
65 #endif
67 /* This variable must be global, since there's no way the caller
68 * can forcibly slay a dead or ungainly running program otherwise.
69 * Multithreading apps and plugins can initialize it (via CMD_INIT)
70 * in an async safe manner PRIOR to calling cmd_run() or cmd_run_array()
71 * for the first time.
72 *
73 * The check for initialized values is atomic and can
74 * occur in any number of threads simultaneously. */
75 static pid_t *_cmd_pids = NULL;
77 /* Try sysconf(_SC_OPEN_MAX) first, as it can be higher than OPEN_MAX.
78 * If that fails and the macro isn't defined, we fall back to an educated
79 * guess. There's no guarantee that our guess is adequate and the program
80 * will die with SIGSEGV if it isn't and the upper boundary is breached. */
81 #ifdef _SC_OPEN_MAX
82 static long maxfd = 0;
83 #elif defined(OPEN_MAX)
84 # define maxfd OPEN_MAX
85 #else /* sysconf macro unavailable, so guess (may be wildly inaccurate) */
86 # define maxfd 256
87 #endif
90 /** prototypes **/
91 static int _cmd_open (char *const *, int *, int *)
92 __attribute__ ((__nonnull__ (1, 2, 3)));
94 static int _cmd_fetch_output (int, output *, int)
95 __attribute__ ((__nonnull__ (2)));
97 static int _cmd_close (int);
99 /* prototype imported from utils.h */
100 extern void die (int, const char *, ...)
101 __attribute__ ((__noreturn__, __format__ (__printf__, 2, 3)));
104 /* this function is NOT async-safe. It is exported so multithreaded
105 * plugins (or other apps) can call it prior to running any commands
106 * through this api and thus achieve async-safeness throughout the api */
107 void
108 cmd_init (void)
109 {
110 #ifndef maxfd
111 if (!maxfd && (maxfd = sysconf (_SC_OPEN_MAX)) < 0) {
112 /* possibly log or emit a warning here, since there's no
113 * guarantee that our guess at maxfd will be adequate */
114 maxfd = 256;
115 }
116 #endif
118 if (!_cmd_pids)
119 _cmd_pids = calloc (maxfd, sizeof (pid_t));
120 }
123 /* Start running a command, array style */
124 static int
125 _cmd_open (char *const *argv, int *pfd, int *pfderr)
126 {
127 char *env[2];
128 pid_t pid;
129 #ifdef RLIMIT_CORE
130 struct rlimit limit;
131 #endif
133 int i = 0;
135 /* if no command was passed, return with no error */
136 if (argv == NULL)
137 return -1;
139 if (!_cmd_pids)
140 CMD_INIT;
142 env[0] = strdup ("LC_ALL=C");
143 env[1] = '\0';
145 if (pipe (pfd) < 0 || pipe (pfderr) < 0 || (pid = fork ()) < 0)
146 return -1; /* errno set by the failing function */
148 /* child runs exceve() and _exit. */
149 if (pid == 0) {
150 #ifdef RLIMIT_CORE
151 /* the program we execve shouldn't leave core files */
152 getrlimit (RLIMIT_CORE, &limit);
153 limit.rlim_cur = 0;
154 setrlimit (RLIMIT_CORE, &limit);
155 #endif
156 close (pfd[0]);
157 if (pfd[1] != STDOUT_FILENO) {
158 dup2 (pfd[1], STDOUT_FILENO);
159 close (pfd[1]);
160 }
161 close (pfderr[0]);
162 if (pfderr[1] != STDERR_FILENO) {
163 dup2 (pfderr[1], STDERR_FILENO);
164 close (pfderr[1]);
165 }
167 /* close all descriptors in _cmd_pids[]
168 * This is executed in a separate address space (pure child),
169 * so we don't have to worry about async safety */
170 for (i = 0; i < maxfd; i++)
171 if (_cmd_pids[i] > 0)
172 close (i);
174 execve (argv[0], argv, env);
175 _exit (STATE_UNKNOWN);
176 }
178 /* parent picks up execution here */
179 /* close childs descriptors in our address space */
180 close (pfd[1]);
181 close (pfderr[1]);
183 /* tag our file's entry in the pid-list and return it */
184 _cmd_pids[pfd[0]] = pid;
186 return pfd[0];
187 }
189 static int
190 _cmd_close (int fd)
191 {
192 int status;
193 pid_t pid;
195 /* make sure the provided fd was opened */
196 if (fd < 0 || fd > maxfd || !_cmd_pids || (pid = _cmd_pids[fd]) == 0)
197 return -1;
199 _cmd_pids[fd] = 0;
200 if (close (fd) == -1)
201 return -1;
203 /* EINTR is ok (sort of), everything else is bad */
204 while (waitpid (pid, &status, 0) < 0)
205 if (errno != EINTR)
206 return -1;
208 /* return child's termination status */
209 return (WIFEXITED (status)) ? WEXITSTATUS (status) : -1;
210 }
213 static int
214 _cmd_fetch_output (int fd, output * op, int flags)
215 {
216 size_t len = 0, i = 0, lineno = 0;
217 size_t rsf = 6, ary_size = 0; /* rsf = right shift factor, dec'ed uncond once */
218 char *buf = NULL;
219 int ret;
220 char tmpbuf[4096];
222 op->buf = NULL;
223 op->buflen = 0;
224 while ((ret = read (fd, tmpbuf, sizeof (tmpbuf))) > 0) {
225 len = (size_t) ret;
226 op->buf = realloc (op->buf, op->buflen + len + 1);
227 memcpy (op->buf + op->buflen, tmpbuf, len);
228 op->buflen += len;
229 i++;
230 }
232 if (ret < 0) {
233 printf ("read() returned %d: %s\n", ret, strerror (errno));
234 return ret;
235 }
237 /* some plugins may want to keep output unbroken, and some commands
238 * will yield no output, so return here for those */
239 if (flags & CMD_NO_ARRAYS || !op->buf || !op->buflen)
240 return op->buflen;
242 /* and some may want both */
243 if (flags & CMD_NO_ASSOC) {
244 buf = malloc (op->buflen);
245 memcpy (buf, op->buf, op->buflen);
246 }
247 else
248 buf = op->buf;
250 op->line = NULL;
251 op->lens = NULL;
252 i = 0;
253 while (i < op->buflen) {
254 /* make sure we have enough memory */
255 if (lineno >= ary_size) {
256 /* ary_size must never be zero */
257 do {
258 ary_size = op->buflen >> --rsf;
259 } while (!ary_size);
261 op->line = realloc (op->line, ary_size * sizeof (char *));
262 op->lens = realloc (op->lens, ary_size * sizeof (size_t));
263 }
265 /* set the pointer to the string */
266 op->line[lineno] = &buf[i];
268 /* hop to next newline or end of buffer */
269 while (buf[i] != '\n' && i < op->buflen)
270 i++;
271 buf[i] = '\0';
273 /* calculate the string length using pointer difference */
274 op->lens[lineno] = (size_t) & buf[i] - (size_t) op->line[lineno];
276 lineno++;
277 i++;
278 }
280 return lineno;
281 }
284 int
285 cmd_run (const char *cmdstring, output * out, output * err, int flags)
286 {
287 int fd, pfd_out[2], pfd_err[2];
288 int i = 0, argc;
289 size_t cmdlen;
290 char **argv = NULL;
291 char *cmd = NULL;
292 char *str = NULL;
294 if (cmdstring == NULL)
295 return -1;
297 /* initialize the structs */
298 if (out)
299 memset (out, 0, sizeof (output));
300 if (err)
301 memset (err, 0, sizeof (output));
303 /* make copy of command string so strtok() doesn't silently modify it */
304 /* (the calling program may want to access it later) */
305 cmdlen = strlen (cmdstring);
306 if ((cmd = malloc (cmdlen + 1)) == NULL)
307 return -1;
308 memcpy (cmd, cmdstring, cmdlen);
309 cmd[cmdlen] = '\0';
311 /* This is not a shell, so we don't handle "???" */
312 if (strstr (cmdstring, "\"")) return -1;
314 /* allow single quotes, but only if non-whitesapce doesn't occur on both sides */
315 if (strstr (cmdstring, " ' ") || strstr (cmdstring, "'''"))
316 return -1;
318 /* each arg must be whitespace-separated, so args can be a maximum
319 * of (len / 2) + 1. We add 1 extra to the mix for NULL termination */
320 argc = (cmdlen >> 1) + 2;
321 argv = calloc (sizeof (char *), argc);
323 if (argv == NULL) {
324 printf ("%s\n", _("Could not malloc argv array in popen()"));
325 return -1;
326 }
328 /* get command arguments (stupidly, but fairly quickly) */
329 while (cmd) {
330 str = cmd;
331 str += strspn (str, " \t\r\n"); /* trim any leading whitespace */
333 if (strstr (str, "'") == str) { /* handle SIMPLE quoted strings */
334 str++;
335 if (!strstr (str, "'"))
336 return -1; /* balanced? */
337 cmd = 1 + strstr (str, "'");
338 str[strcspn (str, "'")] = 0;
339 }
340 else {
341 if (strpbrk (str, " \t\r\n")) {
342 cmd = 1 + strpbrk (str, " \t\r\n");
343 str[strcspn (str, " \t\r\n")] = 0;
344 }
345 else {
346 cmd = NULL;
347 }
348 }
350 if (cmd && strlen (cmd) == strspn (cmd, " \t\r\n"))
351 cmd = NULL;
353 argv[i++] = str;
354 }
356 return cmd_run_array (argv, out, err, flags);
357 }
359 int
360 cmd_run_array (char *const *argv, output * out, output * err, int flags)
361 {
362 int fd, pfd_out[2], pfd_err[2];
364 /* initialize the structs */
365 if (out)
366 memset (out, 0, sizeof (output));
367 if (err)
368 memset (err, 0, sizeof (output));
370 if ((fd = _cmd_open (argv, pfd_out, pfd_err)) == -1)
371 die (STATE_UNKNOWN, _("Could not open pipe: %s\n"), argv[0]);
373 if (out)
374 out->lines = _cmd_fetch_output (pfd_out[0], out, flags);
375 if (err)
376 err->lines = _cmd_fetch_output (pfd_err[0], err, flags);
378 return _cmd_close (fd);
379 }