wireshark/wsutil/privileges.c

/* privileges.c
 * Routines for handling privileges, e.g. set-UID and set-GID on UNIX.
 *
 * Wireshark - Network traffic analyzer
 * By Gerald Combs <gerald@wireshark.org>
 * Copyright 2006 Gerald Combs
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 */

#include "config.h"
#define WS_LOG_DOMAIN LOG_DOMAIN_WSUTIL

#if defined(HAVE_SETRESUID) || defined(HAVE_SETREGUID)
#define _GNU_SOURCE /* Otherwise [sg]etres[gu]id won't be defined on Linux */
#endif

#include <glib.h>

#include "privileges.h"
#include <wsutil/ws_assert.h>
#include <wsutil/wslog.h>

#ifdef _WIN32
#include <windows.h>
#include <wchar.h>
#include <tchar.h>

/*
 * Called when the program starts, to save whatever credential information
 * we'll need later, and to do whatever other specialized platform-dependent
 * initialization we want.
 */
void
init_process_policies(void)
{
	/*
	 * If we have SetProcessDEPPolicy(), turn "data execution
	 * prevention" on - i.e., if the MMU lets you set execute
	 * permission on a per-page basis, turn execute permission
	 * off on most data pages.  SetProcessDEPPolicy() fails on
	 * 64-bit Windows (it's *always* on there), but if it fails,
	 * we don't care (we did our best), so we don't check for
	 * errors.
	 *
	 */
	SetProcessDEPPolicy(PROCESS_DEP_ENABLE);
}

/*
 * For now, we say the program wasn't started with special privileges.
 * There are ways of running programs with credentials other than those
 * for the session in which it's run, but I don't know whether that'd be
 * done with Wireshark/TShark or not.
 */
gboolean
started_with_special_privs(void)
{
	return FALSE;
}

/*
 * For now, we say the program isn't running with special privileges.
 * There are ways of running programs with credentials other than those
 * for the session in which it's run, but I don't know whether that'd be
 * done with Wireshark/TShark or not.
 */
gboolean
running_with_special_privs(void)
{
	return FALSE;
}

/*
 * For now, we don't do anything when asked to relinquish special privileges.
 */
void
relinquish_special_privs_perm(void)
{
}

/*
 * Get the current username.  String must be g_free()d after use.
 */
gchar *
get_cur_username(void) {
	gchar *username;
	username = g_strdup("UNKNOWN");
	return username;
}

/*
 * Get the current group.  String must be g_free()d after use.
 */
gchar *
get_cur_groupname(void) {
	gchar *groupname;
	groupname = g_strdup("UNKNOWN");
	return groupname;
}

#else /* _WIN32 */

#include <sys/types.h>

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#ifdef HAVE_PWD_H
#include <pwd.h>
#endif

#ifdef HAVE_GRP_H
#include <grp.h>
#endif

#include <string.h>
#include <errno.h>

static uid_t ruid, euid;
static gid_t rgid, egid;
static gboolean init_process_policies_called = FALSE;

/*
 * Called when the program starts, to save whatever credential information
 * we'll need later, and to do whatever other specialized platform-dependent
 * initialization we want.
 *
 * The credential information we'll need later on UNIX is the real and
 * effective UID and GID.
 *
 * XXX - do any UN*Xes have opt-in "no execute on data pages by default"
 * permission?  This would be the place to request it.
 */
void
init_process_policies(void)
{
	ruid = getuid();
	euid = geteuid();
	rgid = getgid();
	egid = getegid();

	init_process_policies_called = TRUE;
}

/*
 * "Started with special privileges" means "started out set-UID or set-GID",
 * or run as the root user or group.
 */
gboolean
started_with_special_privs(void)
{
	ws_assert(init_process_policies_called);
#ifdef HAVE_ISSETUGID
	return issetugid();
#else
	return (ruid != euid || rgid != egid || ruid == 0 || rgid == 0);
#endif
}

/*
 * Return TRUE if the real, effective, or saved (if we can check it) user
 * ID or group are 0.
 */
gboolean
running_with_special_privs(void)
{
#ifdef HAVE_SETRESUID
	uid_t ru, eu, su;
#endif
#ifdef HAVE_SETRESGID
	gid_t rg, eg, sg;
#endif

#ifdef HAVE_SETRESUID
	getresuid(&ru, &eu, &su);
	if (ru == 0 || eu == 0 || su == 0)
		return TRUE;
#else
	if (getuid() == 0 || geteuid() == 0)
		return TRUE;
#endif
#ifdef HAVE_SETRESGID
	getresgid(&rg, &eg, &sg);
	if (rg == 0 || eg == 0 || sg == 0)
		return TRUE;
#else
	if (getgid() == 0 || getegid() == 0)
		return TRUE;
#endif
	return FALSE;
}

/*
 * Permanently relinquish  set-UID and set-GID privileges.
 * If error, abort since we probably shouldn't continue
 * with elevated privileges.
 * Note that if this error occurs when dumpcap is called from
 * wireshark or tshark, the message seen will be
 * "Child dumpcap process died:". This is obscure but we'll
 *   consider it acceptable since it should be highly unlikely
 *   that this error will occur.
 */

static void
setxid_fail(const gchar *str)
{
	ws_error("Attempt to relinquish privileges failed [%s()] - aborting: %s\n",
		str, g_strerror(errno));
}

void
relinquish_special_privs_perm(void)
{
	/*
	 * If we were started with special privileges, set the
	 * real and effective group and user IDs to the original
	 * values of the real and effective group and user IDs.
	 * If we're not, don't bother - doing so seems to mung
	 * our group set, at least in Mac OS X 10.5.
	 *
	 * (Set the effective UID last - that takes away our
	 * rights to set anything else.)
	 */
	if (started_with_special_privs()) {
#ifdef HAVE_SETRESGID
		if (setresgid(rgid, rgid, rgid) == -1) {setxid_fail("setresgid");}
#else
		if (setgid(rgid)                == -1) {setxid_fail("setgid"); }
		if (setegid(rgid)               == -1) {setxid_fail("setegid");}
#endif

#ifdef HAVE_SETRESUID
		if (setresuid(ruid, ruid, ruid) == -1) {setxid_fail("setresuid");}
#else
		if (setuid(ruid)                == -1) {setxid_fail("setuid"); }
		if (seteuid(ruid)               == -1) {setxid_fail("seteuid");}
#endif
	}
}

/*
 * Get the current username.  String must be g_free()d after use.
 */
gchar *
get_cur_username(void) {
	gchar *username;
	struct passwd *pw = getpwuid(getuid());

	if (pw) {
		username = g_strdup(pw->pw_name);
	} else {
		username = g_strdup("UNKNOWN");
	}
	endpwent();
	return username;
}

/*
 * Get the current group.  String must be g_free()d after use.
 */
gchar *
get_cur_groupname(void) {
	gchar *groupname;
	struct group *gr = getgrgid(getgid());

	if (gr) {
		groupname = g_strdup(gr->gr_name);
	} else {
		groupname = g_strdup("UNKNOWN");
	}
	endgrent();
	return groupname;
}

#endif /* _WIN32 */

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