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diff --git a/src/lib/evloop/procmon.c b/src/lib/evloop/procmon.c
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+/* Copyright (c) 2011-2018, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file procmon.c
+ * \brief Process-termination monitor functions
+ **/
+
+#include "common/procmon.h"
+
+#include "lib/log/torlog.h"
+#include "lib/log/util_bug.h"
+#include "lib/log/win32err.h"
+#include "lib/malloc/util_malloc.h"
+#include "lib/string/parse_int.h"
+
+#ifdef HAVE_SIGNAL_H
+#include <signal.h>
+#endif
+#ifdef HAVE_ERRNO_H
+#include <errno.h>
+#endif
+
+#ifdef _WIN32
+#include <winsock2.h>
+#include <windows.h>
+#endif
+
+#if (0 == SIZEOF_PID_T) && defined(_WIN32)
+/* Windows does not define pid_t sometimes, but _getpid() returns an int.
+ * Everybody else needs to have a pid_t. */
+typedef int pid_t;
+#define PID_T_FORMAT "%d"
+#elif (SIZEOF_PID_T == SIZEOF_INT) || (SIZEOF_PID_T == SIZEOF_SHORT)
+#define PID_T_FORMAT "%d"
+#elif (SIZEOF_PID_T == SIZEOF_LONG)
+#define PID_T_FORMAT "%ld"
+#elif (SIZEOF_PID_T == 8)
+#define PID_T_FORMAT "%"PRId64
+#else
+#error Unknown: SIZEOF_PID_T
+#endif /* (0 == SIZEOF_PID_T) && defined(_WIN32) || ... */
+
+/* Define to 1 if process-termination monitors on this OS and Libevent
+ version must poll for process termination themselves. */
+#define PROCMON_POLLS 1
+/* Currently we need to poll in some way on all systems. */
+
+#ifdef PROCMON_POLLS
+static void tor_process_monitor_poll_cb(periodic_timer_t *ev,
+ void *procmon_);
+#endif
+
+/* This struct may contain pointers into the original process
+ * specifier string, but it should *never* contain anything which
+ * needs to be freed. */
+/* DOCDOC parsed_process_specifier_t */
+struct parsed_process_specifier_t {
+ pid_t pid;
+};
+
+/** Parse the process specifier given in <b>process_spec</b> into
+ * *<b>ppspec</b>. Return 0 on success; return -1 and store an error
+ * message into *<b>msg</b> on failure. The caller must not free the
+ * returned error message. */
+static int
+parse_process_specifier(const char *process_spec,
+ struct parsed_process_specifier_t *ppspec,
+ const char **msg)
+{
+ long pid_l;
+ int pid_ok = 0;
+ char *pspec_next;
+
+ /* If we're lucky, long will turn out to be large enough to hold a
+ * PID everywhere that Tor runs. */
+ pid_l = tor_parse_long(process_spec, 10, 1, LONG_MAX, &pid_ok, &pspec_next);
+
+ /* Reserve room in the ‘process specifier’ for additional
+ * (platform-specific) identifying information beyond the PID, to
+ * make our process-existence checks a bit less racy in a future
+ * version. */
+ if ((*pspec_next != 0) && (*pspec_next != ' ') && (*pspec_next != ':')) {
+ pid_ok = 0;
+ }
+
+ ppspec->pid = (pid_t)(pid_l);
+ if (!pid_ok || (pid_l != (long)(ppspec->pid))) {
+ *msg = "invalid PID";
+ goto err;
+ }
+
+ return 0;
+ err:
+ return -1;
+}
+
+/* DOCDOC tor_process_monitor_t */
+struct tor_process_monitor_t {
+ /** Log domain for warning messages. */
+ log_domain_mask_t log_domain;
+
+ /** All systems: The best we can do in general is poll for the
+ * process's existence by PID periodically, and hope that the kernel
+ * doesn't reassign the same PID to another process between our
+ * polls. */
+ pid_t pid;
+
+#ifdef _WIN32
+ /** Windows-only: Should we poll hproc? If false, poll pid
+ * instead. */
+ int poll_hproc;
+
+ /** Windows-only: Get a handle to the process (if possible) and
+ * periodically check whether the process we have a handle to has
+ * ended. */
+ HANDLE hproc;
+ /* XXXX We should have Libevent watch hproc for us,
+ * if/when some version of Libevent can be told to do so. */
+#endif /* defined(_WIN32) */
+
+ /* XXXX On Linux, we can and should receive the 22nd
+ * (space-delimited) field (‘starttime’) of /proc/$PID/stat from the
+ * owning controller and store it, and poll once in a while to see
+ * whether it has changed -- if so, the kernel has *definitely*
+ * reassigned the owning controller's PID and we should exit. On
+ * FreeBSD, we can do the same trick using either the 8th
+ * space-delimited field of /proc/$PID/status on the seven FBSD
+ * systems whose admins have mounted procfs, or the start-time field
+ * of the process-information structure returned by kvmgetprocs() on
+ * any system. The latter is ickier. */
+
+ /* XXXX On FreeBSD (and possibly other kqueue systems), we can and
+ * should arrange to receive EVFILT_PROC NOTE_EXIT notifications for
+ * pid, so we don't have to do such a heavyweight poll operation in
+ * order to avoid the PID-reassignment race condition. (We would
+ * still need to poll our own kqueue periodically until some version
+ * of Libevent 2.x learns to receive these events for us.) */
+
+ /** A Libevent event structure, to either poll for the process's
+ * existence or receive a notification when the process ends. */
+ periodic_timer_t *e;
+
+ /** A callback to be called when the process ends. */
+ tor_procmon_callback_t cb;
+ void *cb_arg; /**< A user-specified pointer to be passed to cb. */
+};
+
+/** Verify that the process specifier given in <b>process_spec</b> is
+ * syntactically valid. Return 0 on success; return -1 and store an
+ * error message into *<b>msg</b> on failure. The caller must not
+ * free the returned error message. */
+int
+tor_validate_process_specifier(const char *process_spec,
+ const char **msg)
+{
+ struct parsed_process_specifier_t ppspec;
+
+ tor_assert(msg != NULL);
+ *msg = NULL;
+
+ return parse_process_specifier(process_spec, &ppspec, msg);
+}
+
+/* DOCDOC poll_interval_tv */
+static const struct timeval poll_interval_tv = {15, 0};
+
+/** Create a process-termination monitor for the process specifier
+ * given in <b>process_spec</b>. Return a newly allocated
+ * tor_process_monitor_t on success; return NULL and store an error
+ * message into *<b>msg</b> on failure. The caller must not free
+ * the returned error message.
+ *
+ * When the monitored process terminates, call
+ * <b>cb</b>(<b>cb_arg</b>).
+ */
+tor_process_monitor_t *
+tor_process_monitor_new(struct event_base *base,
+ const char *process_spec,
+ log_domain_mask_t log_domain,
+ tor_procmon_callback_t cb, void *cb_arg,
+ const char **msg)
+{
+ tor_process_monitor_t *procmon = tor_malloc_zero(
+ sizeof(tor_process_monitor_t));
+ struct parsed_process_specifier_t ppspec;
+
+ tor_assert(msg != NULL);
+ *msg = NULL;
+
+ if (procmon == NULL) {
+ *msg = "out of memory";
+ goto err;
+ }
+
+ procmon->log_domain = log_domain;
+
+ if (parse_process_specifier(process_spec, &ppspec, msg))
+ goto err;
+
+ procmon->pid = ppspec.pid;
+
+#ifdef _WIN32
+ procmon->hproc = OpenProcess(PROCESS_QUERY_INFORMATION | SYNCHRONIZE,
+ FALSE,
+ procmon->pid);
+
+ if (procmon->hproc != NULL) {
+ procmon->poll_hproc = 1;
+ log_info(procmon->log_domain, "Successfully opened handle to process "
+ PID_T_FORMAT"; "
+ "monitoring it.",
+ procmon->pid);
+ } else {
+ /* If we couldn't get a handle to the process, we'll try again the
+ * first time we poll. */
+ log_info(procmon->log_domain, "Failed to open handle to process "
+ PID_T_FORMAT"; will "
+ "try again later.",
+ procmon->pid);
+ }
+#endif /* defined(_WIN32) */
+
+ procmon->cb = cb;
+ procmon->cb_arg = cb_arg;
+
+#ifdef PROCMON_POLLS
+ procmon->e = periodic_timer_new(base,
+ &poll_interval_tv,
+ tor_process_monitor_poll_cb, procmon);
+#else /* !(defined(PROCMON_POLLS)) */
+#error OOPS?
+#endif /* defined(PROCMON_POLLS) */
+
+ return procmon;
+ err:
+ tor_process_monitor_free(procmon);
+ return NULL;
+}
+
+#ifdef PROCMON_POLLS
+/** Libevent callback to poll for the existence of the process
+ * monitored by <b>procmon_</b>. */
+static void
+tor_process_monitor_poll_cb(periodic_timer_t *event, void *procmon_)
+{
+ (void)event;
+ tor_process_monitor_t *procmon = (tor_process_monitor_t *)(procmon_);
+ int its_dead_jim;
+
+ tor_assert(procmon != NULL);
+
+#ifdef _WIN32
+ if (procmon->poll_hproc) {
+ DWORD exit_code;
+ if (!GetExitCodeProcess(procmon->hproc, &exit_code)) {
+ char *errmsg = format_win32_error(GetLastError());
+ log_warn(procmon->log_domain, "Error \"%s\" occurred while polling "
+ "handle for monitored process "PID_T_FORMAT"; assuming "
+ "it's dead.",
+ errmsg, procmon->pid);
+ tor_free(errmsg);
+ its_dead_jim = 1;
+ } else {
+ its_dead_jim = (exit_code != STILL_ACTIVE);
+ }
+ } else {
+ /* All we can do is try to open the process, and look at the error
+ * code if it fails again. */
+ procmon->hproc = OpenProcess(PROCESS_QUERY_INFORMATION | SYNCHRONIZE,
+ FALSE,
+ procmon->pid);
+
+ if (procmon->hproc != NULL) {
+ log_info(procmon->log_domain, "Successfully opened handle to monitored "
+ "process "PID_T_FORMAT".",
+ procmon->pid);
+ its_dead_jim = 0;
+ procmon->poll_hproc = 1;
+ } else {
+ DWORD err_code = GetLastError();
+ char *errmsg = format_win32_error(err_code);
+
+ /* When I tested OpenProcess's error codes on Windows 7, I
+ * received error code 5 (ERROR_ACCESS_DENIED) for PIDs of
+ * existing processes that I could not open and error code 87
+ * (ERROR_INVALID_PARAMETER) for PIDs that were not in use.
+ * Since the nonexistent-process error code is sane, I'm going
+ * to assume that all errors other than ERROR_INVALID_PARAMETER
+ * mean that the process we are monitoring is still alive. */
+ its_dead_jim = (err_code == ERROR_INVALID_PARAMETER);
+
+ if (!its_dead_jim)
+ log_info(procmon->log_domain, "Failed to open handle to monitored "
+ "process "PID_T_FORMAT", and error code %lu (%s) is not "
+ "'invalid parameter' -- assuming the process is still alive.",
+ procmon->pid,
+ err_code, errmsg);
+
+ tor_free(errmsg);
+ }
+ }
+#else /* !(defined(_WIN32)) */
+ /* Unix makes this part easy, if a bit racy. */
+ its_dead_jim = kill(procmon->pid, 0);
+ its_dead_jim = its_dead_jim && (errno == ESRCH);
+#endif /* defined(_WIN32) */
+
+ tor_log(its_dead_jim ? LOG_NOTICE : LOG_INFO,
+ procmon->log_domain, "Monitored process "PID_T_FORMAT" is %s.",
+ procmon->pid,
+ its_dead_jim ? "dead" : "still alive");
+
+ if (its_dead_jim) {
+ procmon->cb(procmon->cb_arg);
+ }
+}
+#endif /* defined(PROCMON_POLLS) */
+
+/** Free the process-termination monitor <b>procmon</b>. */
+void
+tor_process_monitor_free_(tor_process_monitor_t *procmon)
+{
+ if (procmon == NULL)
+ return;
+
+#ifdef _WIN32
+ if (procmon->hproc != NULL)
+ CloseHandle(procmon->hproc);
+#endif
+
+ if (procmon->e != NULL)
+ periodic_timer_free(procmon->e);
+
+ tor_free(procmon);
+}