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

diff --git a/plugins/runcmd.c b/plugins/runcmd.c
new file mode 100644 (file)
index 0000000..14300ee
--- /dev/null
+++ b/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);
+}

diff --git a/plugins/runcmd.h b/plugins/runcmd.h
new file mode 100644 (file)
index 0000000..35ebc25
--- /dev/null
+++ b/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 */