services/cap_grp/cap_grp.c

/*-
 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 *
 * Copyright (c) 2013 The FreeBSD Foundation
 * All rights reserved.
 *
 * This software was developed by Pawel Jakub Dawidek under sponsorship from
 * the FreeBSD Foundation.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD: stable/12/lib/libcasper/services/cap_grp/cap_grp.c 331146 2018-03-18 19:50:32Z oshogbo $");

#include <sys/dnv.h>
#include <sys/nv.h>
#include <sys/param.h>

#include <assert.h>
#include <errno.h>
#include <grp.h>
#include <stdlib.h>
#include <string.h>

#include <libcasper.h>
#include <libcasper_service.h>

#include "cap_grp.h"

static struct group ggrp;
static char *gbuffer;
static size_t gbufsize;

static int
group_resize(void)
{
	char *buf;

	if (gbufsize == 0)
		gbufsize = 1024;
	else
		gbufsize *= 2;

	buf = gbuffer;
	gbuffer = realloc(buf, gbufsize);
	if (gbuffer == NULL) {
		free(buf);
		gbufsize = 0;
		return (ENOMEM);
	}
	memset(gbuffer, 0, gbufsize);

	return (0);
}

static int
group_unpack_string(const nvlist_t *nvl, const char *fieldname, char **fieldp,
    char **bufferp, size_t *bufsizep)
{
	const char *str;
	size_t len;

	str = nvlist_get_string(nvl, fieldname);
	len = strlcpy(*bufferp, str, *bufsizep);
	if (len >= *bufsizep)
		return (ERANGE);
	*fieldp = *bufferp;
	*bufferp += len + 1;
	*bufsizep -= len + 1;

	return (0);
}

static int
group_unpack_members(const nvlist_t *nvl, char ***fieldp, char **bufferp,
    size_t *bufsizep)
{
	const char *mem;
	char **outstrs, *str, nvlname[64];
	size_t nmem, datasize, strsize;
	unsigned int ii;
	int n;

	if (!nvlist_exists_number(nvl, "gr_nmem")) {
		datasize = _ALIGNBYTES + sizeof(char *);
		if (datasize >= *bufsizep)
			return (ERANGE);
		outstrs = (char **)_ALIGN(*bufferp);
		outstrs[0] = NULL;
		*fieldp = outstrs;
		*bufferp += datasize;
		*bufsizep -= datasize;
		return (0);
	}

	nmem = (size_t)nvlist_get_number(nvl, "gr_nmem");
	datasize = _ALIGNBYTES + sizeof(char *) * (nmem + 1);
	for (ii = 0; ii < nmem; ii++) {
		n = snprintf(nvlname, sizeof(nvlname), "gr_mem[%u]", ii);
		assert(n > 0 && n < (int)sizeof(nvlname));
		mem = dnvlist_get_string(nvl, nvlname, NULL);
		if (mem == NULL)
			return (EINVAL);
		datasize += strlen(mem) + 1;
	}

	if (datasize >= *bufsizep)
		return (ERANGE);

	outstrs = (char **)_ALIGN(*bufferp);
	str = (char *)outstrs + sizeof(char *) * (nmem + 1);
	for (ii = 0; ii < nmem; ii++) {
		n = snprintf(nvlname, sizeof(nvlname), "gr_mem[%u]", ii);
		assert(n > 0 && n < (int)sizeof(nvlname));
		mem = nvlist_get_string(nvl, nvlname);
		strsize = strlen(mem) + 1;
		memcpy(str, mem, strsize);
		outstrs[ii] = str;
		str += strsize;
	}
	assert(ii == nmem);
	outstrs[ii] = NULL;

	*fieldp = outstrs;
	*bufferp += datasize;
	*bufsizep -= datasize;

	return (0);
}

static int
group_unpack(const nvlist_t *nvl, struct group *grp, char *buffer,
    size_t bufsize)
{
	int error;

	if (!nvlist_exists_string(nvl, "gr_name"))
		return (EINVAL);

	memset(grp, 0, sizeof(*grp));

	error = group_unpack_string(nvl, "gr_name", &grp->gr_name, &buffer,
	    &bufsize);
	if (error != 0)
		return (error);
	error = group_unpack_string(nvl, "gr_passwd", &grp->gr_passwd, &buffer,
	    &bufsize);
	if (error != 0)
		return (error);
	grp->gr_gid = (gid_t)nvlist_get_number(nvl, "gr_gid");
	error = group_unpack_members(nvl, &grp->gr_mem, &buffer, &bufsize);
	if (error != 0)
		return (error);

	return (0);
}

static int
cap_getgrcommon_r(cap_channel_t *chan, const char *cmd, const char *name,
    gid_t gid, struct group *grp, char *buffer, size_t bufsize,
    struct group **result)
{
	nvlist_t *nvl;
	bool getgr_r;
	int error;

	nvl = nvlist_create(0);
	nvlist_add_string(nvl, "cmd", cmd);
	if (strcmp(cmd, "getgrent") == 0 || strcmp(cmd, "getgrent_r") == 0) {
		/* Add nothing. */
	} else if (strcmp(cmd, "getgrnam") == 0 ||
	    strcmp(cmd, "getgrnam_r") == 0) {
		nvlist_add_string(nvl, "name", name);
	} else if (strcmp(cmd, "getgrgid") == 0 ||
	    strcmp(cmd, "getgrgid_r") == 0) {
		nvlist_add_number(nvl, "gid", (uint64_t)gid);
	} else {
		abort();
	}
	nvl = cap_xfer_nvlist(chan, nvl);
	if (nvl == NULL) {
		assert(errno != 0);
		*result = NULL;
		return (errno);
	}
	error = (int)nvlist_get_number(nvl, "error");
	if (error != 0) {
		nvlist_destroy(nvl);
		*result = NULL;
		return (error);
	}

	if (!nvlist_exists_string(nvl, "gr_name")) {
		/* Not found. */
		nvlist_destroy(nvl);
		*result = NULL;
		return (0);
	}

	getgr_r = (strcmp(cmd, "getgrent_r") == 0 ||
	    strcmp(cmd, "getgrnam_r") == 0 || strcmp(cmd, "getgrgid_r") == 0);

	for (;;) {
		error = group_unpack(nvl, grp, buffer, bufsize);
		if (getgr_r || error != ERANGE)
			break;
		assert(buffer == gbuffer);
		assert(bufsize == gbufsize);
		error = group_resize();
		if (error != 0)
			break;
		/* Update pointers after resize. */
		buffer = gbuffer;
		bufsize = gbufsize;
	}

	nvlist_destroy(nvl);

	if (error == 0)
		*result = grp;
	else
		*result = NULL;

	return (error);
}

static struct group *
cap_getgrcommon(cap_channel_t *chan, const char *cmd, const char *name,
    gid_t gid)
{
	struct group *result;
	int error, serrno;

	serrno = errno;

	error = cap_getgrcommon_r(chan, cmd, name, gid, &ggrp, gbuffer,
	    gbufsize, &result);
	if (error != 0) {
		errno = error;
		return (NULL);
	}

	errno = serrno;

	return (result);
}

struct group *
cap_getgrent(cap_channel_t *chan)
{

	return (cap_getgrcommon(chan, "getgrent", NULL, 0));
}

struct group *
cap_getgrnam(cap_channel_t *chan, const char *name)
{

	return (cap_getgrcommon(chan, "getgrnam", name, 0));
}

struct group *
cap_getgrgid(cap_channel_t *chan, gid_t gid)
{

	return (cap_getgrcommon(chan, "getgrgid", NULL, gid));
}

int
cap_getgrent_r(cap_channel_t *chan, struct group *grp, char *buffer,
    size_t bufsize, struct group **result)
{

	return (cap_getgrcommon_r(chan, "getgrent_r", NULL, 0, grp, buffer,
	    bufsize, result));
}

int
cap_getgrnam_r(cap_channel_t *chan, const char *name, struct group *grp,
    char *buffer, size_t bufsize, struct group **result)
{

	return (cap_getgrcommon_r(chan, "getgrnam_r", name, 0, grp, buffer,
	    bufsize, result));
}

int
cap_getgrgid_r(cap_channel_t *chan, gid_t gid, struct group *grp, char *buffer,
    size_t bufsize, struct group **result)
{

	return (cap_getgrcommon_r(chan, "getgrgid_r", NULL, gid, grp, buffer,
	    bufsize, result));
}

int
cap_setgroupent(cap_channel_t *chan, int stayopen)
{
	nvlist_t *nvl;

	nvl = nvlist_create(0);
	nvlist_add_string(nvl, "cmd", "setgroupent");
	nvlist_add_bool(nvl, "stayopen", stayopen != 0);
	nvl = cap_xfer_nvlist(chan, nvl);
	if (nvl == NULL)
		return (0);
	if (nvlist_get_number(nvl, "error") != 0) {
		errno = nvlist_get_number(nvl, "error");
		nvlist_destroy(nvl);
		return (0);
	}
	nvlist_destroy(nvl);

	return (1);
}

int
cap_setgrent(cap_channel_t *chan)
{
	nvlist_t *nvl;

	nvl = nvlist_create(0);
	nvlist_add_string(nvl, "cmd", "setgrent");
	nvl = cap_xfer_nvlist(chan, nvl);
	if (nvl == NULL)
		return (0);
	if (nvlist_get_number(nvl, "error") != 0) {
		errno = nvlist_get_number(nvl, "error");
		nvlist_destroy(nvl);
		return (0);
	}
	nvlist_destroy(nvl);

	return (1);
}

void
cap_endgrent(cap_channel_t *chan)
{
	nvlist_t *nvl;

	nvl = nvlist_create(0);
	nvlist_add_string(nvl, "cmd", "endgrent");
	/* Ignore any errors, we have no way to report them. */
	nvlist_destroy(cap_xfer_nvlist(chan, nvl));
}

int
cap_grp_limit_cmds(cap_channel_t *chan, const char * const *cmds, size_t ncmds)
{
	nvlist_t *limits, *nvl;
	unsigned int i;

	if (cap_limit_get(chan, &limits) < 0)
		return (-1);
	if (limits == NULL) {
		limits = nvlist_create(0);
	} else {
		if (nvlist_exists_nvlist(limits, "cmds"))
			nvlist_free_nvlist(limits, "cmds");
	}
	nvl = nvlist_create(0);
	for (i = 0; i < ncmds; i++)
		nvlist_add_null(nvl, cmds[i]);
	nvlist_move_nvlist(limits, "cmds", nvl);
	return (cap_limit_set(chan, limits));
}

int
cap_grp_limit_fields(cap_channel_t *chan, const char * const *fields,
    size_t nfields)
{
	nvlist_t *limits, *nvl;
	unsigned int i;

	if (cap_limit_get(chan, &limits) < 0)
		return (-1);
	if (limits == NULL) {
		limits = nvlist_create(0);
	} else {
		if (nvlist_exists_nvlist(limits, "fields"))
			nvlist_free_nvlist(limits, "fields");
	}
	nvl = nvlist_create(0);
	for (i = 0; i < nfields; i++)
		nvlist_add_null(nvl, fields[i]);
	nvlist_move_nvlist(limits, "fields", nvl);
	return (cap_limit_set(chan, limits));
}

int
cap_grp_limit_groups(cap_channel_t *chan, const char * const *names,
    size_t nnames, const gid_t *gids, size_t ngids)
{
	nvlist_t *limits, *groups;
	unsigned int i;
	char nvlname[64];
	int n;

	if (cap_limit_get(chan, &limits) < 0)
		return (-1);
	if (limits == NULL) {
		limits = nvlist_create(0);
	} else {
		if (nvlist_exists_nvlist(limits, "groups"))
			nvlist_free_nvlist(limits, "groups");
	}
	groups = nvlist_create(0);
	for (i = 0; i < ngids; i++) {
		n = snprintf(nvlname, sizeof(nvlname), "gid%u", i);
		assert(n > 0 && n < (int)sizeof(nvlname));
		nvlist_add_number(groups, nvlname, (uint64_t)gids[i]);
	}
	for (i = 0; i < nnames; i++) {
		n = snprintf(nvlname, sizeof(nvlname), "gid%u", i);
		assert(n > 0 && n < (int)sizeof(nvlname));
		nvlist_add_string(groups, nvlname, names[i]);
	}
	nvlist_move_nvlist(limits, "groups", groups);
	return (cap_limit_set(chan, limits));
}

/*
 * Service functions.
 */
static bool
grp_allowed_cmd(const nvlist_t *limits, const char *cmd)
{

	if (limits == NULL)
		return (true);

	/*
	 * If no limit was set on allowed commands, then all commands
	 * are allowed.
	 */
	if (!nvlist_exists_nvlist(limits, "cmds"))
		return (true);

	limits = nvlist_get_nvlist(limits, "cmds");
	return (nvlist_exists_null(limits, cmd));
}

static int
grp_allowed_cmds(const nvlist_t *oldlimits, const nvlist_t *newlimits)
{
	const char *name;
	void *cookie;
	int type;

	cookie = NULL;
	while ((name = nvlist_next(newlimits, &type, &cookie)) != NULL) {
		if (type != NV_TYPE_NULL)
			return (EINVAL);
		if (!grp_allowed_cmd(oldlimits, name))
			return (ENOTCAPABLE);
	}

	return (0);
}

static bool
grp_allowed_group(const nvlist_t *limits, const char *gname, gid_t gid)
{
	const char *name;
	void *cookie;
	int type;

	if (limits == NULL)
		return (true);

	/*
	 * If no limit was set on allowed groups, then all groups are allowed.
	 */
	if (!nvlist_exists_nvlist(limits, "groups"))
		return (true);

	limits = nvlist_get_nvlist(limits, "groups");
	cookie = NULL;
	while ((name = nvlist_next(limits, &type, &cookie)) != NULL) {
		switch (type) {
		case NV_TYPE_NUMBER:
			if (gid != (gid_t)-1 &&
			    nvlist_get_number(limits, name) == (uint64_t)gid) {
				return (true);
			}
			break;
		case NV_TYPE_STRING:
			if (gname != NULL &&
			    strcmp(nvlist_get_string(limits, name),
			    gname) == 0) {
				return (true);
			}
			break;
		default:
			abort();
		}
	}

	return (false);
}

static int
grp_allowed_groups(const nvlist_t *oldlimits, const nvlist_t *newlimits)
{
	const char *name, *gname;
	void *cookie;
	gid_t gid;
	int type;

	cookie = NULL;
	while ((name = nvlist_next(newlimits, &type, &cookie)) != NULL) {
		switch (type) {
		case NV_TYPE_NUMBER:
			gid = (gid_t)nvlist_get_number(newlimits, name);
			gname = NULL;
			break;
		case NV_TYPE_STRING:
			gid = (gid_t)-1;
			gname = nvlist_get_string(newlimits, name);
			break;
		default:
			return (EINVAL);
		}
		if (!grp_allowed_group(oldlimits, gname, gid))
			return (ENOTCAPABLE);
	}

	return (0);
}

static bool
grp_allowed_field(const nvlist_t *limits, const char *field)
{

	if (limits == NULL)
		return (true);

	/*
	 * If no limit was set on allowed fields, then all fields are allowed.
	 */
	if (!nvlist_exists_nvlist(limits, "fields"))
		return (true);

	limits = nvlist_get_nvlist(limits, "fields");
	return (nvlist_exists_null(limits, field));
}

static int
grp_allowed_fields(const nvlist_t *oldlimits, const nvlist_t *newlimits)
{
	const char *name;
	void *cookie;
	int type;

	cookie = NULL;
	while ((name = nvlist_next(newlimits, &type, &cookie)) != NULL) {
		if (type != NV_TYPE_NULL)
			return (EINVAL);
		if (!grp_allowed_field(oldlimits, name))
			return (ENOTCAPABLE);
	}

	return (0);
}

static bool
grp_pack(const nvlist_t *limits, const struct group *grp, nvlist_t *nvl)
{
	char nvlname[64];
	int n;

	if (grp == NULL)
		return (true);

	/*
	 * If either name or GID is allowed, we allow it.
	 */
	if (!grp_allowed_group(limits, grp->gr_name, grp->gr_gid))
		return (false);

	if (grp_allowed_field(limits, "gr_name"))
		nvlist_add_string(nvl, "gr_name", grp->gr_name);
	else
		nvlist_add_string(nvl, "gr_name", "");
	if (grp_allowed_field(limits, "gr_passwd"))
		nvlist_add_string(nvl, "gr_passwd", grp->gr_passwd);
	else
		nvlist_add_string(nvl, "gr_passwd", "");
	if (grp_allowed_field(limits, "gr_gid"))
		nvlist_add_number(nvl, "gr_gid", (uint64_t)grp->gr_gid);
	else
		nvlist_add_number(nvl, "gr_gid", (uint64_t)-1);
	if (grp_allowed_field(limits, "gr_mem") && grp->gr_mem[0] != NULL) {
		unsigned int ngroups;

		for (ngroups = 0; grp->gr_mem[ngroups] != NULL; ngroups++) {
			n = snprintf(nvlname, sizeof(nvlname), "gr_mem[%u]",
			    ngroups);
			assert(n > 0 && n < (ssize_t)sizeof(nvlname));
			nvlist_add_string(nvl, nvlname, grp->gr_mem[ngroups]);
		}
		nvlist_add_number(nvl, "gr_nmem", (uint64_t)ngroups);
	}

	return (true);
}

static int
grp_getgrent(const nvlist_t *limits, const nvlist_t *nvlin __unused,
    nvlist_t *nvlout)
{
	struct group *grp;

	for (;;) {
		errno = 0;
		grp = getgrent();
		if (errno != 0)
			return (errno);
		if (grp_pack(limits, grp, nvlout))
			return (0);
	}

	/* NOTREACHED */
}

static int
grp_getgrnam(const nvlist_t *limits, const nvlist_t *nvlin, nvlist_t *nvlout)
{
	struct group *grp;
	const char *name;

	if (!nvlist_exists_string(nvlin, "name"))
		return (EINVAL);
	name = nvlist_get_string(nvlin, "name");
	assert(name != NULL);

	errno = 0;
	grp = getgrnam(name);
	if (errno != 0)
		return (errno);

	(void)grp_pack(limits, grp, nvlout);

	return (0);
}

static int
grp_getgrgid(const nvlist_t *limits, const nvlist_t *nvlin, nvlist_t *nvlout)
{
	struct group *grp;
	gid_t gid;

	if (!nvlist_exists_number(nvlin, "gid"))
		return (EINVAL);

	gid = (gid_t)nvlist_get_number(nvlin, "gid");

	errno = 0;
	grp = getgrgid(gid);
	if (errno != 0)
		return (errno);

	(void)grp_pack(limits, grp, nvlout);

	return (0);
}

static int
grp_setgroupent(const nvlist_t *limits __unused, const nvlist_t *nvlin,
    nvlist_t *nvlout __unused)
{
	int stayopen;

	if (!nvlist_exists_bool(nvlin, "stayopen"))
		return (EINVAL);

	stayopen = nvlist_get_bool(nvlin, "stayopen") ? 1 : 0;

	return (setgroupent(stayopen) == 0 ? EFAULT : 0);
}

static int
grp_setgrent(const nvlist_t *limits __unused, const nvlist_t *nvlin __unused,
    nvlist_t *nvlout __unused)
{

	setgrent();

	return (0);
}

static int
grp_endgrent(const nvlist_t *limits __unused, const nvlist_t *nvlin __unused,
    nvlist_t *nvlout __unused)
{

	endgrent();

	return (0);
}

static int
grp_limit(const nvlist_t *oldlimits, const nvlist_t *newlimits)
{
	const nvlist_t *limits;
	const char *name;
	void *cookie;
	int error, type;

	if (oldlimits != NULL && nvlist_exists_nvlist(oldlimits, "cmds") &&
	    !nvlist_exists_nvlist(newlimits, "cmds")) {
		return (ENOTCAPABLE);
	}
	if (oldlimits != NULL && nvlist_exists_nvlist(oldlimits, "fields") &&
	    !nvlist_exists_nvlist(newlimits, "fields")) {
		return (ENOTCAPABLE);
	}
	if (oldlimits != NULL && nvlist_exists_nvlist(oldlimits, "groups") &&
	    !nvlist_exists_nvlist(newlimits, "groups")) {
		return (ENOTCAPABLE);
	}

	cookie = NULL;
	while ((name = nvlist_next(newlimits, &type, &cookie)) != NULL) {
		if (type != NV_TYPE_NVLIST)
			return (EINVAL);
		limits = nvlist_get_nvlist(newlimits, name);
		if (strcmp(name, "cmds") == 0)
			error = grp_allowed_cmds(oldlimits, limits);
		else if (strcmp(name, "fields") == 0)
			error = grp_allowed_fields(oldlimits, limits);
		else if (strcmp(name, "groups") == 0)
			error = grp_allowed_groups(oldlimits, limits);
		else
			error = EINVAL;
		if (error != 0)
			return (error);
	}

	return (0);
}

static int
grp_command(const char *cmd, const nvlist_t *limits, nvlist_t *nvlin,
    nvlist_t *nvlout)
{
	int error;

	if (!grp_allowed_cmd(limits, cmd))
		return (ENOTCAPABLE);

	if (strcmp(cmd, "getgrent") == 0 || strcmp(cmd, "getgrent_r") == 0)
		error = grp_getgrent(limits, nvlin, nvlout);
	else if (strcmp(cmd, "getgrnam") == 0 || strcmp(cmd, "getgrnam_r") == 0)
		error = grp_getgrnam(limits, nvlin, nvlout);
	else if (strcmp(cmd, "getgrgid") == 0 || strcmp(cmd, "getgrgid_r") == 0)
		error = grp_getgrgid(limits, nvlin, nvlout);
	else if (strcmp(cmd, "setgroupent") == 0)
		error = grp_setgroupent(limits, nvlin, nvlout);
	else if (strcmp(cmd, "setgrent") == 0)
		error = grp_setgrent(limits, nvlin, nvlout);
	else if (strcmp(cmd, "endgrent") == 0)
		error = grp_endgrent(limits, nvlin, nvlout);
	else
		error = EINVAL;

	return (error);
}

CREATE_SERVICE("system.grp", grp_limit, grp_command, 0);