initial versions of the runcmd framework by andreas

git-svn-id: https://nagiosplug.svn.sourceforge.net/svnroot/nagiosplug/nagiosplug/trunk@1197 f882894a-f735-0410-b71e-b25c423dba1c

plugins/runcmd.c

@@ -0,0 +1,339 @@
+/*
+ * $Id$
+ *
+ * A simple interface to executing programs from other programs, using an
+ * optimized and safe popen()-like implementation. It is considered safe
+ * in that no shell needs to be spawned and the environment passed to the
+ * execve()'d program is essentially empty.
+ *
+ *
+ * The code in this file is a derivative of popen.c which in turn was taken
+ * from "Advanced Programming for the Unix Environment" by W. Richard Stevens.
+ *
+ * Care has been taken to make sure the functions are async-safe. The one
+ * function which isn't is np_runcmd_init() which it doesn't make sense to
+ * call twice anyway, so the api as a whole should be considered async-safe.
+ *
+ */
+
+/** includes **/
+#include "runcmd.h"
+#ifdef HAVE_SYS_WAIT_H
+# include <sys/wait.h>
+#endif
+
+/** macros **/
+#ifndef WEXITSTATUS
+# define WEXITSTATUS(stat_val) ((unsigned)(stat_val) >> 8)
+#endif
+
+#ifndef WIFEXITED
+# define WIFEXITED(stat_val) (((stat_val) & 255) == 0)
+#endif
+
+/* 4.3BSD Reno <signal.h> doesn't define SIG_ERR */
+#if defined(SIG_IGN) && !defined(SIG_ERR)
+# define SIG_ERR ((Sigfunc *)-1)
+#endif
+
+/* This variable must be global, since there's no way the caller
+ * can forcibly slay a dead or ungainly running program otherwise.
+ * Multithreading apps and plugins can initialize it (via NP_RUNCMD_INIT)
+ * in an async safe manner PRIOR to calling np_runcmd() for the first time.
+ *
+ * The check for initialized values is atomic and can
+ * occur in any number of threads simultaneously. */
+static pid_t *np_pids = NULL;
+
+/* If OPEN_MAX isn't defined, we try the sysconf syscall first.
+ * If that fails, we fall back to an educated guess which is accurate
+ * on Linux and some other systems. There's no guarantee that our guess is
+ * adequate and the program will die with SIGSEGV if it isn't and the
+ * upper boundary is breached. */
+#ifdef OPEN_MAX
+# define maxfd OPEN_MAX
+#else
+# ifndef _SC_OPEN_MAX /* sysconf macro unavailable, so guess */
+#  define maxfd 256
+# else
+static int maxfd = 0;
+# endif /* _SC_OPEN_MAX */
+#endif /* OPEN_MAX */
+
+
+/** prototypes **/
+static int np_runcmd_open(const char *, int *, int *)
+	__attribute__((__nonnull__(1, 2, 3)));
+
+static int np_fetch_output(int, output *, int)
+	__attribute__((__nonnull__(2)));
+
+static int np_runcmd_close(int);
+
+/* imported from utils.h */
+extern void die (int, const char *, ...)
+	__attribute__((__noreturn__,__format__(__printf__, 2, 3)));
+
+
+/* this function is NOT async-safe. It is exported so multithreaded
+ * plugins (or other apps) can call it prior to running any commands
+ * through this api and thus achieve async-safeness throughout the api */
+void np_runcmd_init(void)
+{
+#if !defined(OPEN_MAX) && defined(_SC_OPEN_MAX)
+	if(!maxfd) {
+		if((maxfd = sysconf(_SC_OPEN_MAX)) < 0) {
+			/* possibly log or emit a warning here, since there's no
+			 * guarantee that our guess at maxfd will be adequate */
+			maxfd = 256;
+		}
+	}
+#endif
+
+	if(!np_pids) np_pids = calloc(maxfd, sizeof(pid_t));
+}
+
+
+/* Start running a command */
+static int
+np_runcmd_open(const char *cmdstring, int *pfd, int *pfderr)
+{
+	char *env[2];
+	char *cmd = NULL;
+	char **argv = NULL;
+	char *str;
+	int argc;
+	size_t cmdlen;
+	pid_t pid;
+#ifdef RLIMIT_CORE
+	struct rlimit limit;
+#endif
+
+	int i = 0;
+
+	if(!np_pids) NP_RUNCMD_INIT;
+
+	env[0] = strdup("LC_ALL=C");
+	env[1] = '\0';
+
+	/* if no command was passed, return with no error */
+	if (cmdstring == NULL)
+		return -1;
+
+	/* make copy of command string so strtok() doesn't silently modify it */
+	/* (the calling program may want to access it later) */
+	cmdlen = strlen(cmdstring);
+	cmd = malloc(cmdlen + 1);
+	if (cmd == NULL) return -1;
+	memcpy(cmd, cmdstring, cmdlen);
+
+	/* This is not a shell, so we don't handle "???" */
+	if (strstr (cmdstring, "\"")) return -1;
+
+	/* allow single quotes, but only if non-whitesapce doesn't occur on both sides */
+	if (strstr (cmdstring, " ' ") || strstr (cmdstring, "'''"))
+		return -1;
+
+	/* each arg must be whitespace-separated, so args can be a maximum
+	 * of (len / 2) + 1. We add 1 extra to the mix for NULL termination */
+	argc = (cmdlen >> 1) + 2;
+	argv = calloc(sizeof(char *), argc);
+
+	if (argv == NULL) {
+		printf (_("Could not malloc argv array in popen()\n"));
+		return -1;
+	}
+
+	/* get command arguments (stupidly, but fairly quickly) */
+	while (cmd) {
+		str = cmd;
+		str += strspn (str, " \t\r\n"); /* trim any leading whitespace */
+
+		if (strstr (str, "'") == str) {	/* handle SIMPLE quoted strings */
+			str++;
+			if (!strstr (str, "'")) return -1;	/* balanced? */
+			cmd = 1 + strstr (str, "'");
+			str[strcspn (str, "'")] = 0;
+		}
+		else {
+			if (strpbrk (str, " \t\r\n")) {
+				cmd = 1 + strpbrk (str, " \t\r\n");
+				str[strcspn (str, " \t\r\n")] = 0;
+			}
+			else {
+				cmd = NULL;
+			}
+		}
+
+		if (cmd && strlen (cmd) == strspn (cmd, " \t\r\n"))
+			cmd = NULL;
+
+		argv[i++] = str;
+	}
+
+	if (pipe(pfd) < 0 || pipe(pfderr) < 0 || (pid = fork()) < 0)
+		return -1; /* errno set by the failing function */
+
+	/* child runs exceve() and _exit. */
+	if (pid == 0) {
+#ifdef 	RLIMIT_CORE
+		/* the program we execve shouldn't leave core files */
+		getrlimit (RLIMIT_CORE, &limit);
+		limit.rlim_cur = 0;
+		setrlimit (RLIMIT_CORE, &limit);
+#endif
+		close (pfd[0]);
+		if (pfd[1] != STDOUT_FILENO) {
+			dup2 (pfd[1], STDOUT_FILENO);
+			close (pfd[1]);
+		}
+		close (pfderr[0]);
+		if (pfderr[1] != STDERR_FILENO) {
+			dup2 (pfderr[1], STDERR_FILENO);
+			close (pfderr[1]);
+		}
+
+		/* close all descriptors in np_pids[]
+		 * This is executed in a separate address space (pure child),
+		 * so we don't have to worry about async safety */
+		for (i = 0; i < maxfd; i++)
+			if(np_pids[i] > 0)
+				close (i);
+
+		execve (argv[0], argv, env);
+		_exit (0);
+	}
+
+	/* parent picks up execution here */
+	/* close childs descriptors in our address space */
+	close(pfd[1]);
+	close(pfderr[1]);
+
+	/* tag our file's entry in the pid-list and return it */
+	np_pids[pfd[0]] = pid;
+
+	return pfd[0];
+}
+
+
+static int
+np_runcmd_close(int fd)
+{
+	int status;
+	pid_t pid;
+
+	/* make sure this fd was opened by popen() */
+	if(fd < 0 || fd > maxfd || !np_pids || (pid = np_pids[fd]) == 0)
+		return -1;
+
+	np_pids[fd] = 0;
+	if (close (fd) == -1) return -1;
+
+	/* EINTR is ok (sort of), everything else is bad */
+	while (waitpid (pid, &status, 0) < 0)
+		if (errno != EINTR) return -1;
+
+	/* return child's termination status */
+	return (WIFEXITED(status)) ? WEXITSTATUS(status) : -1;
+}
+
+
+void
+popen_timeout_alarm_handler (int signo)
+{
+	size_t i;
+
+	if (signo == SIGALRM)
+		puts(_("CRITICAL - Plugin timed out while executing system call\n"));
+
+	if(np_pids) for(i = 0; i < maxfd; i++) {
+		if(np_pids[i] != 0) kill(np_pids[i], SIGKILL);
+	}
+
+	exit (STATE_CRITICAL);
+}
+
+
+static int
+np_fetch_output(int fd, output *op, int flags)
+{
+	size_t len = 0, i = 0;
+	size_t rsf = 6, ary_size = 0; /* rsf = right shift factor, dec'ed uncond once */
+	char *buf = NULL;
+	int ret;
+	char tmpbuf[4096];
+
+	op->buf = NULL;
+	op->buflen = 0;
+	while((ret = read(fd, tmpbuf, sizeof(tmpbuf))) > 0) {
+		len = (size_t)ret;
+		op->buf = realloc(op->buf, op->buflen + len + 1);
+		memcpy(op->buf + op->buflen, tmpbuf, len);
+		op->buflen += len;
+		i++;
+	}
+
+	if(ret < 0) {
+		printf("read() returned %d: %s\n", ret, strerror(errno));
+		return ret;
+	}
+
+	if(!op->buf || !op->buflen) return 0;
+
+	/* some plugins may want to keep output unbroken */
+	if(flags & RUNCMD_NO_ARRAYS)
+		return op->buflen;
+
+	/* and some may want both (*sigh*) */
+	if(flags & RUNCMD_NO_ASSOC) {
+		buf = malloc(op->buflen);
+		memcpy(buf, op->buf, op->buflen);
+	}
+	else buf = op->buf;
+
+	op->line = NULL;
+	op->lens = NULL;
+	len = i = 0;
+	while(i < op->buflen) {
+		/* make sure we have enough memory */
+		if(len >= ary_size) {
+			ary_size = op->buflen >> --rsf;
+			op->line = realloc(op->line, ary_size * sizeof(char *));
+			op->lens = realloc(op->lens, ary_size * sizeof(size_t));
+		}
+
+		/* set the pointer to the string */
+		op->line[len] = &buf[i];
+
+		/* hop to next newline or end of buffer */
+		while(buf[i] != '\n' && i < op->buflen) i++;
+		buf[i] = '\0';
+
+		/* calculate the string length using pointer difference */
+		op->lens[len] = (size_t)&buf[i] - (size_t)op->line[len];
+		
+		len++;
+		i++;
+	}
+
+	return len;
+}
+
+
+int
+np_runcmd(const char *cmd, output *out, output *err, int flags)
+{
+	int fd, pfd_out[2], pfd_err[2];
+
+	/* initialize the structs */
+	if(out) memset(out, 0, sizeof(output));
+	if(err) memset(err, 0, sizeof(output));
+
+	if((fd = np_runcmd_open(cmd, pfd_out, pfd_err)) == -1)
+		die (STATE_UNKNOWN, _("Could not open pipe: %s\n"), cmd);
+
+	if(out) out->lines = np_fetch_output(pfd_out[0], out, flags);
+	if(err) err->lines = np_fetch_output(pfd_err[0], err, flags);
+
+	return np_runcmd_close(fd);
+}

plugins/runcmd.h

@@ -0,0 +1,39 @@
+/*
+ * $Id$
+ * 
+ * Author: Andreas Ericsson <ae@op5.se>
+ *
+ * Copyright: GNU GPL v2 or any later version.
+ * 
+ */
+
+#ifndef NAGIOSPLUG_RUNCMD_H
+#define NAGIOSPLUG_RUNCMD_H
+
+#include "common.h"
+
+/** types **/
+struct output {
+	char *buf;     /* output buffer */
+	size_t buflen; /* output buffer content length */
+	char **line;   /* array of lines (points to buf) */
+	size_t *lens;  /* string lengths */
+	size_t lines;  /* lines of output */
+};
+
+typedef struct output output;
+
+/** prototypes **/
+int np_runcmd(const char *, output *, output *, int);
+void popen_timeout_alarm_handler(int)
+	__attribute__((__noreturn__));
+
+/* only multi-threaded plugins need to bother with this */
+void np_runcmd_init(void);
+#define NP_RUNCMD_INIT np_runcmd_init()
+
+/* possible flags for np_runcmd()'s fourth argument */
+#define RUNCMD_NO_ARRAYS 0x01 /* don't populate arrays at all */
+#define RUNCMD_NO_ASSOC 0x02  /* output.line won't point to buf */
+
+#endif /* NAGIOSPLUG_RUNCMD_H */