apparmor/parser/af_unix.cc

/*
 *   Copyright (c) 2014
 *   Canonical, Ltd. (All rights reserved)
 *
 *   This program is free software; you can redistribute it and/or
 *   modify it under the terms of version 2 of the GNU General Public
 *   License published by the Free Software Foundation.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, contact Novell, Inc. or Canonical
 *   Ltd.
 */

#include <stdlib.h>
#include <string.h>
#include <sys/apparmor.h>

#include <iomanip>
#include <string>
#include <sstream>

#include "common_optarg.h"
#include "network.h"
#include "parser.h"
#include "profile.h"
#include "af_unix.h"

/* See unix(7) for autobind address definition */
#define autobind_address_pattern "\\x00[0-9a-f][0-9a-f][0-9a-f][0-9a-f][0-9a-f]";

int parse_unix_perms(const char *str_perms, perms_t *perms, int fail)
{
	return parse_X_perms("unix", AA_VALID_NET_PERMS, str_perms, perms, fail);
}


static struct supported_cond supported_conds[] = {
	{ "addr", true, false, false, either_cond },
	{ NULL, false, false, false, local_cond },	/* sentinel */
};

void unix_rule::move_conditionals(struct cond_entry *conds)
{
	struct cond_entry *ent;

	list_for_each(conds, ent) {

		if (!cond_check(supported_conds, ent, false, "unix") &&
		    !move_base_cond(ent, false)) {
			yyerror("unix rule: invalid conditional '%s'\n",
				ent->name);
			continue;
		}
		if (strcmp(ent->name, "addr") == 0) {
			move_conditional_value("unix socket", &addr, ent);
			if (addr[0] != '@' &&
			    !(strcmp(addr, "none") == 0 ||
			      strcmp(addr, "auto") == 0))
				yyerror("unix rule: invalid value for addr='%s'\n", addr);
		}

		/* TODO: add conditionals for
		 *   listen queue length
		 *   attrs that can be read/set
		 *   ops that can be read/set
		 * allow in on
		 *   type, protocol
		 * local label match, and set
		 */
	}
}

void unix_rule::move_peer_conditionals(struct cond_entry *conds)
{
	struct cond_entry *ent;

	list_for_each(conds, ent) {
		if (!cond_check(supported_conds, ent, true, "unix") &&
		    !move_base_cond(ent, true)) {
			yyerror("unix rule: invalid peer conditional '%s'\n",
				ent->name);
			continue;
		}
		if (strcmp(ent->name, "addr") == 0) {
			move_conditional_value("unix", &peer_addr, ent);
			if ((peer_addr[0] != '@') &&
			    !(strcmp(peer_addr, "none") == 0 ||
			      strcmp(peer_addr, "auto") == 0))
				yyerror("unix rule: invalid value for addr='%s'\n", peer_addr);
		}
	}
}

unix_rule::unix_rule(unsigned int type_p, audit_t audit_p, rule_mode_t rule_mode_p):
	af_rule(AF_UNIX), addr(NULL), peer_addr(NULL)
{
	if (type_p != 0xffffffff) {
		sock_type_n = type_p;
		sock_type = strdup(net_find_type_name(type_p));
		if (!sock_type)
			yyerror("socket rule: invalid socket type '%d'", type_p);
	}
	perms = AA_VALID_NET_PERMS;
	audit = audit_p;
	rule_mode = rule_mode_p;
}

unix_rule::unix_rule(perms_t perms_p, struct cond_entry *conds,
		     struct cond_entry *peer_conds):
	af_rule(AF_UNIX), addr(NULL), peer_addr(NULL)
{
	move_conditionals(conds);
	move_peer_conditionals(peer_conds);

	if (perms_p) {
		perms = perms_p;
		if (perms & ~AA_VALID_NET_PERMS)
			yyerror("perms contains invalid permissions for unix socket rules\n");
		else if ((perms & ~AA_PEER_NET_PERMS) && has_peer_conds())
			yyerror("unix socket 'create', 'shutdown', 'setattr', 'getattr', 'bind', 'listen', 'setopt', and/or 'getopt' accesses cannot be used with peer socket conditionals\n");
	} else {
		perms = AA_VALID_NET_PERMS;
	}

	free_cond_list(conds);
	free_cond_list(peer_conds);

}

ostream &unix_rule::dump_local(ostream &os)
{
	af_rule::dump_local(os);
	if (addr)
		os << " addr='" << addr << "'";
	return os;
}

ostream &unix_rule::dump_peer(ostream &os)
{
	af_rule::dump_peer(os);
	if (peer_addr)
		os << " addr='" << peer_addr << "'";
	return os;
}


int unix_rule::expand_variables(void)
{
	int error = af_rule::expand_variables();
	if (error)
		return error;
	error = expand_entry_variables(&addr);
	if (error)
		return error;
	filter_slashes(addr);
	error = expand_entry_variables(&peer_addr);
	if (error)
		return error;
	filter_slashes(peer_addr);

	return 0;
}


void unix_rule::warn_once(const char *name)
{
	rule_t::warn_once(name, "extended network unix socket rules not enforced");
}

static void writeu16(std::ostringstream &o, int v)
{
	u16 tmp = htobe16((u16) v);
	u8 *byte1 = (u8 *)&tmp;
	u8 *byte2 = byte1 + 1;

	o << "\\x" << std::setfill('0') << std::setw(2) << std::hex << static_cast<unsigned int>(*byte1);
	o << "\\x" << std::setfill('0') << std::setw(2) << std::hex << static_cast<unsigned int>(*byte2);
}

#define CMD_ADDR	1
#define CMD_LISTEN	2
#define CMD_ACCEPT	3
#define CMD_OPT		4

void unix_rule::downgrade_rule(Profile &prof) {
	perms_t mask = (perms_t) -1;

	if (!prof.net.allow && !prof.alloc_net_table())
		yyerror(_("Memory allocation error."));
	if (sock_type_n != -1)
		mask = 1 << sock_type_n;
	if (rule_mode != RULE_DENY) {
		prof.net.allow[AF_UNIX] |= mask;
		if (audit == AUDIT_FORCE)
			prof.net.audit[AF_UNIX] |= mask;
	} else {
		/* deny rules have to be dropped because the downgrade makes
		 * the rule less specific meaning it will make the profile more
		 * restrictive and may end up denying accesses that might be
		 * allowed by the profile.
		 */
		if (parseopts.warn & WARN_RULE_NOT_ENFORCED)
			rule_t::warn_once(prof.name, "deny unix socket rule not enforced, can't be downgraded to generic network rule\n");
	}
}

void unix_rule::write_to_prot(std::ostringstream &buffer)
{
	int c = features_supports_networkv8 ? AA_CLASS_NETV8 : AA_CLASS_NET;

	buffer << "\\x" << std::setfill('0') << std::setw(2) << std::hex << c;
	writeu16(buffer, AF_UNIX);
	if (sock_type)
		writeu16(buffer, sock_type_n);
	else
		buffer << "..";
	if (proto)
		writeu16(buffer, proto_n);
	else
		buffer << "..";
}

bool unix_rule::write_addr(std::ostringstream &buffer, const char *addr)
{
	std::string buf;
	pattern_t ptype;

	if (addr) {
		int pos;
		if (strcmp(addr, "none") == 0) {
			/* anonymous */
			buffer << "\\x01";
		} else if (strcmp(addr, "auto") == 0) {
			/* autobind - special autobind rule written already
			 * just generate pattern that matches autobind
			 * generated addresses.
			 */
			buffer << autobind_address_pattern;
		} else {
			/* skip leading @ */
			ptype = convert_aaregex_to_pcre(addr + 1, 0, glob_null, buf, &pos);
			if (ptype == ePatternInvalid)
				return false;
			/* kernel starts abstract with \0 */
			buffer << "\\x00";
			buffer << buf;
		}
	} else
		/* match any addr or anonymous */
		buffer << ".*";

	/* todo: change to out of band separator */
	buffer << "\\x00";

	return true;
}

bool unix_rule::write_label(std::ostringstream &buffer, const char *label)
{
	std::string buf;
	pattern_t ptype;

	if (label) {
		int pos;
		ptype = convert_aaregex_to_pcre(label, 0, glob_default, buf, &pos);
		if (ptype == ePatternInvalid)
			return false;
		/* kernel starts abstract with \0 */
		buffer << buf;
	} else
		buffer << default_match_pattern;

	return true;
}

/* General Layout
 *
 * Local socket end point perms
 * CLASS_NET  AF  TYPE PROTO  local (addr\0label) \0 cmd cmd_option
 *          ^   ^           ^                       ^              ^
 *          |   |           |                       |              |
 *  stub perm   |           |                       |              |
 *              |           |                       |              |
 *  sub stub perm           |                       |              |
 *                          |                       |              |
 *                create perm                       |              |
 *                                                  |              |
 *                                                  |              |
 *                         bind, accept, get/set attr              |
 *                                                                 |
 *                                          listen, set/get opt perm
 *
 *
 * peer socket end point perms
 * CLASS_NET  AF  TYPE PROTO  local(addr\0label\0) cmd_addr peer(addr\0label )
 *                                                                          ^
 *                                                                          |
 *                                           send/receive connect/accept perm
 *
 * NOTE: accept is encoded twice, locally to check if a socket is allowed
 *       to accept, and then as a pair to test that it can accept the pair.
 */
int unix_rule::gen_policy_re(Profile &prof)
{
	std::ostringstream buffer;
	std::string buf;

	perms_t mask = perms;

	/* always generate a downgraded rule. This doesn't change generated
	 * policy size and allows the binary policy to be loaded against
	 * older kernels and be enforced to the best of the old network
	 * rules ability
	 */
	downgrade_rule(prof);
	if (!features_supports_unix) {
		if (features_supports_network || features_supports_networkv8) {
			/* only warn if we are building against a kernel
			 * that requires downgrading */
			if (parseopts.warn & WARN_RULE_DOWNGRADED)
				rule_t::warn_once(prof.name, "downgrading extended network unix socket rule to generic network rule\n");
			/* TODO: add ability to abort instead of downgrade */
			return RULE_OK;
		} else {
			warn_once(prof.name);
		}
		return RULE_NOT_SUPPORTED;
	}

	write_to_prot(buffer);
	if ((mask & AA_NET_CREATE) && !has_peer_conds()) {
		buf = buffer.str();
		if (!prof.policy.rules->add_rule(buf.c_str(), rule_mode == RULE_DENY,
						 map_perms(AA_NET_CREATE),
						 map_perms(audit == AUDIT_FORCE ? AA_NET_CREATE : 0),
						 parseopts))
			goto fail;
		mask &= ~AA_NET_CREATE;
	}

	/* write special pattern for autobind? Will not grant bind
	 * on any specific address
	 */
	if ((mask & AA_NET_BIND) && (!addr || (strcmp(addr, "auto") == 0))) {
		std::ostringstream tmp;

		tmp << buffer.str();
		/* todo: change to out of band separator */
		/* skip addr, its 0 length */
		tmp << "\\x00";
		/* local label option */
		if (!write_label(tmp, label))
			goto fail;
		/* separator */
		tmp << "\\x00";

		buf = tmp.str();
		if (!prof.policy.rules->add_rule(buf.c_str(), rule_mode == RULE_DENY,
						 map_perms(AA_NET_BIND),
						 map_perms(audit == AUDIT_FORCE ? AA_NET_BIND : 0),
						 parseopts))
			goto fail;
		/* clear if auto, else generic need to generate addr below */
		if (addr)
			mask &= ~AA_NET_BIND;
	}

	if (mask) {
		/* local addr */
		if (!write_addr(buffer, addr))
			goto fail;
		/* local label option */
		if (!write_label(buffer, label))
			goto fail;
		/* separator */
		buffer << "\\x00";

		/* create already masked off */
		int local_mask = has_peer_conds() ? AA_NET_ACCEPT :
					AA_LOCAL_NET_PERMS & ~AA_LOCAL_NET_CMD;
		if (mask & local_mask) {
			buf = buffer.str();
			if (!prof.policy.rules->add_rule(buf.c_str(), rule_mode == RULE_DENY,
							 map_perms(mask & local_mask),
							 map_perms(audit == AUDIT_FORCE ? mask & local_mask : 0),
							 parseopts))
				goto fail;
		}

		if ((mask & AA_NET_LISTEN) && !has_peer_conds()) {
			std::ostringstream tmp(buffer.str());
			tmp.seekp(0, ios_base::end);
			tmp << "\\x" << std::setfill('0') << std::setw(2) << std::hex << CMD_LISTEN;
			/* TODO: backlog conditional: for now match anything*/
			tmp << "..";
			buf = tmp.str();
			if (!prof.policy.rules->add_rule(buf.c_str(), rule_mode == RULE_DENY,
							 map_perms(AA_NET_LISTEN),
							 map_perms(audit == AUDIT_FORCE ? AA_NET_LISTEN : 0),
							 parseopts))
				goto fail;
		}
		if ((mask & AA_NET_OPT) && !has_peer_conds()) {
			std::ostringstream tmp(buffer.str());
			tmp.seekp(0, ios_base::end);
			tmp << "\\x" << std::setfill('0') << std::setw(2) << std::hex << CMD_OPT;
			/* TODO: sockopt conditional: for now match anything */
			tmp << "..";
			buf = tmp.str();
			if (!prof.policy.rules->add_rule(buf.c_str(), rule_mode == RULE_DENY,
							 map_perms(AA_NET_OPT),
							 map_perms(audit == AUDIT_FORCE ? AA_NET_OPT : 0),
							 parseopts))
				goto fail;
		}
		mask &= ~AA_LOCAL_NET_PERMS | AA_NET_ACCEPT;
	} /* if (mask) */

	if (mask & AA_PEER_NET_PERMS) {
		/* cmd selector */
		buffer << "\\x" << std::setfill('0') << std::setw(2) << std::hex << CMD_ADDR;

		/* local addr */
		if (!write_addr(buffer, peer_addr))
			goto fail;
		/* local label option */
		if (!write_label(buffer, peer_label))
			goto fail;

		buf = buffer.str();
		if (!prof.policy.rules->add_rule(buf.c_str(), rule_mode == RULE_DENY, map_perms(perms & AA_PEER_NET_PERMS), map_perms(audit == AUDIT_FORCE ? perms & AA_PEER_NET_PERMS : 0), parseopts))
			goto fail;
	}

	return RULE_OK;

fail:
	return RULE_ERROR;
}