4155796c5575730d74d746a5e4d9fdf0ad2529ab
1 /*
2 * $Id$
3 *
4 * A simple interface to executing programs from other programs, using an
5 * optimized and safe popen()-like implementation. It is considered safe
6 * in that no shell needs to be spawned and the environment passed to the
7 * execve()'d program is essentially empty.
8 *
9 *
10 * The code in this file is a derivative of popen.c which in turn was taken
11 * from "Advanced Programming for the Unix Environment" by W. Richard Stevens.
12 *
13 * Care has been taken to make sure the functions are async-safe. The one
14 * function which isn't is np_runcmd_init() which it doesn't make sense to
15 * call twice anyway, so the api as a whole should be considered async-safe.
16 *
17 */
19 #define NAGIOSPLUG_API_C 1
21 /** includes **/
22 #include "runcmd.h"
23 #ifdef HAVE_SYS_WAIT_H
24 # include <sys/wait.h>
25 #endif
27 /** macros **/
28 #ifndef WEXITSTATUS
29 # define WEXITSTATUS(stat_val) ((unsigned)(stat_val) >> 8)
30 #endif
32 #ifndef WIFEXITED
33 # define WIFEXITED(stat_val) (((stat_val) & 255) == 0)
34 #endif
36 /* 4.3BSD Reno <signal.h> doesn't define SIG_ERR */
37 #if defined(SIG_IGN) && !defined(SIG_ERR)
38 # define SIG_ERR ((Sigfunc *)-1)
39 #endif
41 /* This variable must be global, since there's no way the caller
42 * can forcibly slay a dead or ungainly running program otherwise.
43 * Multithreading apps and plugins can initialize it (via NP_RUNCMD_INIT)
44 * in an async safe manner PRIOR to calling np_runcmd() for the first time.
45 *
46 * The check for initialized values is atomic and can
47 * occur in any number of threads simultaneously. */
48 static pid_t *np_pids = NULL;
50 /* Try sysconf(_SC_OPEN_MAX) first, as it can be higher than OPEN_MAX.
51 * If that fails and the macro isn't defined, we fall back to an educated
52 * guess. There's no guarantee that our guess is adequate and the program
53 * will die with SIGSEGV if it isn't and the upper boundary is breached. */
54 #ifdef _SC_OPEN_MAX
55 static long maxfd = 0;
56 #elif defined(OPEN_MAX)
57 # define maxfd OPEN_MAX
58 #else /* sysconf macro unavailable, so guess (may be wildly inaccurate) */
59 # define maxfd 256
60 #endif
63 /** prototypes **/
64 static int np_runcmd_open(const char *, int *, int *)
65 __attribute__((__nonnull__(1, 2, 3)));
67 static int np_fetch_output(int, output *, int)
68 __attribute__((__nonnull__(2)));
70 static int np_runcmd_close(int);
72 /* prototype imported from utils.h */
73 extern void die (int, const char *, ...)
74 __attribute__((__noreturn__,__format__(__printf__, 2, 3)));
77 /* this function is NOT async-safe. It is exported so multithreaded
78 * plugins (or other apps) can call it prior to running any commands
79 * through this api and thus achieve async-safeness throughout the api */
80 void np_runcmd_init(void)
81 {
82 #ifndef maxfd
83 if(!maxfd && (maxfd = sysconf(_SC_OPEN_MAX)) < 0) {
84 /* possibly log or emit a warning here, since there's no
85 * guarantee that our guess at maxfd will be adequate */
86 maxfd = 256;
87 }
88 #endif
90 if(!np_pids) np_pids = calloc(maxfd, sizeof(pid_t));
91 }
94 /* Start running a command */
95 static int
96 np_runcmd_open(const char *cmdstring, int *pfd, int *pfderr)
97 {
98 char *env[2];
99 char *cmd = NULL;
100 char **argv = NULL;
101 char *str;
102 int argc;
103 size_t cmdlen;
104 pid_t pid;
105 #ifdef RLIMIT_CORE
106 struct rlimit limit;
107 #endif
109 int i = 0;
111 if(!np_pids) NP_RUNCMD_INIT;
113 env[0] = strdup("LC_ALL=C");
114 env[1] = '\0';
116 /* if no command was passed, return with no error */
117 if (cmdstring == NULL)
118 return -1;
120 /* make copy of command string so strtok() doesn't silently modify it */
121 /* (the calling program may want to access it later) */
122 cmdlen = strlen(cmdstring);
123 if((cmd = malloc(cmdlen + 1)) == NULL) return -1;
124 memcpy(cmd, cmdstring, cmdlen);
125 cmd[cmdlen] = '\0';
127 /* This is not a shell, so we don't handle "???" */
128 if (strstr (cmdstring, "\"")) return -1;
130 /* allow single quotes, but only if non-whitesapce doesn't occur on both sides */
131 if (strstr (cmdstring, " ' ") || strstr (cmdstring, "'''"))
132 return -1;
134 /* each arg must be whitespace-separated, so args can be a maximum
135 * of (len / 2) + 1. We add 1 extra to the mix for NULL termination */
136 argc = (cmdlen >> 1) + 2;
137 argv = calloc(sizeof(char *), argc);
139 if (argv == NULL) {
140 printf (_("Could not malloc argv array in popen()\n"));
141 return -1;
142 }
144 /* get command arguments (stupidly, but fairly quickly) */
145 while (cmd) {
146 str = cmd;
147 str += strspn (str, " \t\r\n"); /* trim any leading whitespace */
149 if (strstr (str, "'") == str) { /* handle SIMPLE quoted strings */
150 str++;
151 if (!strstr (str, "'")) return -1; /* balanced? */
152 cmd = 1 + strstr (str, "'");
153 str[strcspn (str, "'")] = 0;
154 }
155 else {
156 if (strpbrk (str, " \t\r\n")) {
157 cmd = 1 + strpbrk (str, " \t\r\n");
158 str[strcspn (str, " \t\r\n")] = 0;
159 }
160 else {
161 cmd = NULL;
162 }
163 }
165 if (cmd && strlen (cmd) == strspn (cmd, " \t\r\n"))
166 cmd = NULL;
168 argv[i++] = str;
169 }
171 if (pipe(pfd) < 0 || pipe(pfderr) < 0 || (pid = fork()) < 0)
172 return -1; /* errno set by the failing function */
174 /* child runs exceve() and _exit. */
175 if (pid == 0) {
176 #ifdef RLIMIT_CORE
177 /* the program we execve shouldn't leave core files */
178 getrlimit (RLIMIT_CORE, &limit);
179 limit.rlim_cur = 0;
180 setrlimit (RLIMIT_CORE, &limit);
181 #endif
182 close (pfd[0]);
183 if (pfd[1] != STDOUT_FILENO) {
184 dup2 (pfd[1], STDOUT_FILENO);
185 close (pfd[1]);
186 }
187 close (pfderr[0]);
188 if (pfderr[1] != STDERR_FILENO) {
189 dup2 (pfderr[1], STDERR_FILENO);
190 close (pfderr[1]);
191 }
193 /* close all descriptors in np_pids[]
194 * This is executed in a separate address space (pure child),
195 * so we don't have to worry about async safety */
196 for (i = 0; i < maxfd; i++)
197 if(np_pids[i] > 0)
198 close (i);
200 execve (argv[0], argv, env);
201 _exit (0);
202 }
204 /* parent picks up execution here */
205 /* close childs descriptors in our address space */
206 close(pfd[1]);
207 close(pfderr[1]);
209 /* tag our file's entry in the pid-list and return it */
210 np_pids[pfd[0]] = pid;
212 return pfd[0];
213 }
216 static int
217 np_runcmd_close(int fd)
218 {
219 int status;
220 pid_t pid;
222 /* make sure this fd was opened by popen() */
223 if(fd < 0 || fd > maxfd || !np_pids || (pid = np_pids[fd]) == 0)
224 return -1;
226 np_pids[fd] = 0;
227 if (close (fd) == -1) return -1;
229 /* EINTR is ok (sort of), everything else is bad */
230 while (waitpid (pid, &status, 0) < 0)
231 if (errno != EINTR) return -1;
233 /* return child's termination status */
234 return (WIFEXITED(status)) ? WEXITSTATUS(status) : -1;
235 }
238 void
239 popen_timeout_alarm_handler (int signo)
240 {
241 size_t i;
243 if (signo == SIGALRM)
244 puts(_("CRITICAL - Plugin timed out while executing system call\n"));
246 if(np_pids) for(i = 0; i < maxfd; i++) {
247 if(np_pids[i] != 0) kill(np_pids[i], SIGKILL);
248 }
250 exit (STATE_CRITICAL);
251 }
254 static int
255 np_fetch_output(int fd, output *op, int flags)
256 {
257 size_t len = 0, i = 0, lineno = 0;
258 size_t rsf = 6, ary_size = 0; /* rsf = right shift factor, dec'ed uncond once */
259 char *buf = NULL;
260 int ret;
261 char tmpbuf[4096];
263 op->buf = NULL;
264 op->buflen = 0;
265 while((ret = read(fd, tmpbuf, sizeof(tmpbuf))) > 0) {
266 len = (size_t)ret;
267 op->buf = realloc(op->buf, op->buflen + len + 1);
268 memcpy(op->buf + op->buflen, tmpbuf, len);
269 op->buflen += len;
270 i++;
271 }
273 if(ret < 0) {
274 printf("read() returned %d: %s\n", ret, strerror(errno));
275 return ret;
276 }
278 /* some plugins may want to keep output unbroken, and some commands
279 * will yield no output, so return here for those */
280 if(flags & RUNCMD_NO_ARRAYS || !op->buf || !op->buflen)
281 return op->buflen;
283 /* and some may want both */
284 if(flags & RUNCMD_NO_ASSOC) {
285 buf = malloc(op->buflen);
286 memcpy(buf, op->buf, op->buflen);
287 }
288 else buf = op->buf;
290 op->line = NULL;
291 op->lens = NULL;
292 i = 0;
293 while(i < op->buflen) {
294 /* make sure we have enough memory */
295 if(lineno >= ary_size) {
296 /* ary_size must never be zero */
297 do {
298 ary_size = op->buflen >> --rsf;
299 } while(!ary_size);
301 op->line = realloc(op->line, ary_size * sizeof(char *));
302 op->lens = realloc(op->lens, ary_size * sizeof(size_t));
303 }
305 /* set the pointer to the string */
306 op->line[lineno] = &buf[i];
308 /* hop to next newline or end of buffer */
309 while(buf[i] != '\n' && i < op->buflen) i++;
310 buf[i] = '\0';
312 /* calculate the string length using pointer difference */
313 op->lens[lineno] = (size_t)&buf[i] - (size_t)op->line[lineno];
315 lineno++;
316 i++;
317 }
319 return lineno;
320 }
323 int
324 np_runcmd(const char *cmd, output *out, output *err, int flags)
325 {
326 int fd, pfd_out[2], pfd_err[2];
328 /* initialize the structs */
329 if(out) memset(out, 0, sizeof(output));
330 if(err) memset(err, 0, sizeof(output));
332 if((fd = np_runcmd_open(cmd, pfd_out, pfd_err)) == -1)
333 die (STATE_UNKNOWN, _("Could not open pipe: %s\n"), cmd);
335 if(out) out->lines = np_fetch_output(pfd_out[0], out, flags);
336 if(err) err->lines = np_fetch_output(pfd_err[0], err, flags);
338 return np_runcmd_close(fd);
339 }