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 np_runcmd_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 "runcmd.h"
46 #ifdef HAVE_SYS_WAIT_H
47 # include <sys/wait.h>
48 #endif
50 /** macros **/
51 #ifndef WEXITSTATUS
52 # define WEXITSTATUS(stat_val) ((unsigned)(stat_val) >> 8)
53 #endif
55 #ifndef WIFEXITED
56 # define WIFEXITED(stat_val) (((stat_val) & 255) == 0)
57 #endif
59 /* 4.3BSD Reno <signal.h> doesn't define SIG_ERR */
60 #if defined(SIG_IGN) && !defined(SIG_ERR)
61 # define SIG_ERR ((Sigfunc *)-1)
62 #endif
64 /* This variable must be global, since there's no way the caller
65 * can forcibly slay a dead or ungainly running program otherwise.
66 * Multithreading apps and plugins can initialize it (via NP_RUNCMD_INIT)
67 * in an async safe manner PRIOR to calling np_runcmd() for the first time.
68 *
69 * The check for initialized values is atomic and can
70 * occur in any number of threads simultaneously. */
71 static pid_t *np_pids = NULL;
73 /* Try sysconf(_SC_OPEN_MAX) first, as it can be higher than OPEN_MAX.
74 * If that fails and the macro isn't defined, we fall back to an educated
75 * guess. There's no guarantee that our guess is adequate and the program
76 * will die with SIGSEGV if it isn't and the upper boundary is breached. */
77 #ifdef _SC_OPEN_MAX
78 static long maxfd = 0;
79 #elif defined(OPEN_MAX)
80 # define maxfd OPEN_MAX
81 #else /* sysconf macro unavailable, so guess (may be wildly inaccurate) */
82 # define maxfd 256
83 #endif
86 /** prototypes **/
87 static int np_runcmd_open(const char *, int *, int *)
88 __attribute__((__nonnull__(1, 2, 3)));
90 static int np_fetch_output(int, output *, int)
91 __attribute__((__nonnull__(2)));
93 static int np_runcmd_close(int);
95 /* prototype imported from utils.h */
96 extern void die (int, const char *, ...)
97 __attribute__((__noreturn__,__format__(__printf__, 2, 3)));
100 /* this function is NOT async-safe. It is exported so multithreaded
101 * plugins (or other apps) can call it prior to running any commands
102 * through this api and thus achieve async-safeness throughout the api */
103 void np_runcmd_init(void)
104 {
105 #ifndef maxfd
106 if(!maxfd && (maxfd = sysconf(_SC_OPEN_MAX)) < 0) {
107 /* possibly log or emit a warning here, since there's no
108 * guarantee that our guess at maxfd will be adequate */
109 maxfd = 256;
110 }
111 #endif
113 if(!np_pids) np_pids = calloc(maxfd, sizeof(pid_t));
114 }
117 /* Start running a command */
118 static int
119 np_runcmd_open(const char *cmdstring, int *pfd, int *pfderr)
120 {
121 char *env[2];
122 char *cmd = NULL;
123 char **argv = NULL;
124 char *str;
125 int argc;
126 size_t cmdlen;
127 pid_t pid;
128 #ifdef RLIMIT_CORE
129 struct rlimit limit;
130 #endif
132 int i = 0;
134 if(!np_pids) NP_RUNCMD_INIT;
136 env[0] = strdup("LC_ALL=C");
137 env[1] = '\0';
139 /* if no command was passed, return with no error */
140 if (cmdstring == NULL)
141 return -1;
143 /* make copy of command string so strtok() doesn't silently modify it */
144 /* (the calling program may want to access it later) */
145 cmdlen = strlen(cmdstring);
146 if((cmd = malloc(cmdlen + 1)) == NULL) return -1;
147 memcpy(cmd, cmdstring, cmdlen);
148 cmd[cmdlen] = '\0';
150 /* This is not a shell, so we don't handle "???" */
151 if (strstr (cmdstring, "\"")) return -1;
153 /* allow single quotes, but only if non-whitesapce doesn't occur on both sides */
154 if (strstr (cmdstring, " ' ") || strstr (cmdstring, "'''"))
155 return -1;
157 /* each arg must be whitespace-separated, so args can be a maximum
158 * of (len / 2) + 1. We add 1 extra to the mix for NULL termination */
159 argc = (cmdlen >> 1) + 2;
160 argv = calloc(sizeof(char *), argc);
162 if (argv == NULL) {
163 printf ("%s\n", _("Could not malloc argv array in popen()"));
164 return -1;
165 }
167 /* get command arguments (stupidly, but fairly quickly) */
168 while (cmd) {
169 str = cmd;
170 str += strspn (str, " \t\r\n"); /* trim any leading whitespace */
172 if (strstr (str, "'") == str) { /* handle SIMPLE quoted strings */
173 str++;
174 if (!strstr (str, "'")) return -1; /* balanced? */
175 cmd = 1 + strstr (str, "'");
176 str[strcspn (str, "'")] = 0;
177 }
178 else {
179 if (strpbrk (str, " \t\r\n")) {
180 cmd = 1 + strpbrk (str, " \t\r\n");
181 str[strcspn (str, " \t\r\n")] = 0;
182 }
183 else {
184 cmd = NULL;
185 }
186 }
188 if (cmd && strlen (cmd) == strspn (cmd, " \t\r\n"))
189 cmd = NULL;
191 argv[i++] = str;
192 }
194 if (pipe(pfd) < 0 || pipe(pfderr) < 0 || (pid = fork()) < 0)
195 return -1; /* errno set by the failing function */
197 /* child runs exceve() and _exit. */
198 if (pid == 0) {
199 #ifdef RLIMIT_CORE
200 /* the program we execve shouldn't leave core files */
201 getrlimit (RLIMIT_CORE, &limit);
202 limit.rlim_cur = 0;
203 setrlimit (RLIMIT_CORE, &limit);
204 #endif
205 close (pfd[0]);
206 if (pfd[1] != STDOUT_FILENO) {
207 dup2 (pfd[1], STDOUT_FILENO);
208 close (pfd[1]);
209 }
210 close (pfderr[0]);
211 if (pfderr[1] != STDERR_FILENO) {
212 dup2 (pfderr[1], STDERR_FILENO);
213 close (pfderr[1]);
214 }
216 /* close all descriptors in np_pids[]
217 * This is executed in a separate address space (pure child),
218 * so we don't have to worry about async safety */
219 for (i = 0; i < maxfd; i++)
220 if(np_pids[i] > 0)
221 close (i);
223 execve (argv[0], argv, env);
224 _exit (STATE_UNKNOWN);
225 }
227 /* parent picks up execution here */
228 /* close childs descriptors in our address space */
229 close(pfd[1]);
230 close(pfderr[1]);
232 /* tag our file's entry in the pid-list and return it */
233 np_pids[pfd[0]] = pid;
235 return pfd[0];
236 }
239 static int
240 np_runcmd_close(int fd)
241 {
242 int status;
243 pid_t pid;
245 /* make sure this fd was opened by popen() */
246 if(fd < 0 || fd > maxfd || !np_pids || (pid = np_pids[fd]) == 0)
247 return -1;
249 np_pids[fd] = 0;
250 if (close (fd) == -1) return -1;
252 /* EINTR is ok (sort of), everything else is bad */
253 while (waitpid (pid, &status, 0) < 0)
254 if (errno != EINTR) return -1;
256 /* return child's termination status */
257 return (WIFEXITED(status)) ? WEXITSTATUS(status) : -1;
258 }
261 void
262 popen_timeout_alarm_handler (int signo)
263 {
264 size_t i;
266 if (signo == SIGALRM)
267 puts(_("CRITICAL - Plugin timed out while executing system call\n"));
269 if(np_pids) for(i = 0; i < maxfd; i++) {
270 if(np_pids[i] != 0) kill(np_pids[i], SIGKILL);
271 }
273 exit (STATE_CRITICAL);
274 }
277 static int
278 np_fetch_output(int fd, output *op, int flags)
279 {
280 size_t len = 0, i = 0, lineno = 0;
281 size_t rsf = 6, ary_size = 0; /* rsf = right shift factor, dec'ed uncond once */
282 char *buf = NULL;
283 int ret;
284 char tmpbuf[4096];
286 op->buf = NULL;
287 op->buflen = 0;
288 while((ret = read(fd, tmpbuf, sizeof(tmpbuf))) > 0) {
289 len = (size_t)ret;
290 op->buf = realloc(op->buf, op->buflen + len + 1);
291 memcpy(op->buf + op->buflen, tmpbuf, len);
292 op->buflen += len;
293 i++;
294 }
296 if(ret < 0) {
297 printf("read() returned %d: %s\n", ret, strerror(errno));
298 return ret;
299 }
301 /* some plugins may want to keep output unbroken, and some commands
302 * will yield no output, so return here for those */
303 if(flags & RUNCMD_NO_ARRAYS || !op->buf || !op->buflen)
304 return op->buflen;
306 /* and some may want both */
307 if(flags & RUNCMD_NO_ASSOC) {
308 buf = malloc(op->buflen);
309 memcpy(buf, op->buf, op->buflen);
310 }
311 else buf = op->buf;
313 op->line = NULL;
314 op->lens = NULL;
315 i = 0;
316 while(i < op->buflen) {
317 /* make sure we have enough memory */
318 if(lineno >= ary_size) {
319 /* ary_size must never be zero */
320 do {
321 ary_size = op->buflen >> --rsf;
322 } while(!ary_size);
324 op->line = realloc(op->line, ary_size * sizeof(char *));
325 op->lens = realloc(op->lens, ary_size * sizeof(size_t));
326 }
328 /* set the pointer to the string */
329 op->line[lineno] = &buf[i];
331 /* hop to next newline or end of buffer */
332 while(buf[i] != '\n' && i < op->buflen) i++;
333 buf[i] = '\0';
335 /* calculate the string length using pointer difference */
336 op->lens[lineno] = (size_t)&buf[i] - (size_t)op->line[lineno];
338 lineno++;
339 i++;
340 }
342 return lineno;
343 }
346 int
347 np_runcmd(const char *cmd, output *out, output *err, int flags)
348 {
349 int fd, pfd_out[2], pfd_err[2];
351 /* initialize the structs */
352 if(out) memset(out, 0, sizeof(output));
353 if(err) memset(err, 0, sizeof(output));
355 if((fd = np_runcmd_open(cmd, pfd_out, pfd_err)) == -1)
356 die (STATE_UNKNOWN, _("Could not open pipe: %s\n"), cmd);
358 if(out) out->lines = np_fetch_output(pfd_out[0], out, flags);
359 if(err) err->lines = np_fetch_output(pfd_err[0], err, flags);
361 return np_runcmd_close(fd);
362 }