capability.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * AppArmor security module
  4 *
  5 * This file contains AppArmor capability mediation functions
  6 *
  7 * Copyright (C) 1998-2008 Novell/SUSE
  8 * Copyright 2009-2010 Canonical Ltd.
  9 */
 10
 11#include <linux/capability.h>
 12#include <linux/errno.h>
 13#include <linux/gfp.h>
 14#include <linux/security.h>
 15#include <linux/timekeeping.h>
 16
 17#include "include/apparmor.h"
 18#include "include/capability.h"
 19#include "include/cred.h"
 20#include "include/policy.h"
 21#include "include/audit.h"
 22
 23/*
 24 * Table of capability names: we generate it from capabilities.h.
 25 */
 26#include "capability_names.h"
 27
 28struct aa_sfs_entry aa_sfs_entry_caps[] = {
 29	AA_SFS_FILE_STRING("mask", AA_SFS_CAPS_MASK),
 30	AA_SFS_FILE_BOOLEAN("extended", 1),
 31	{ }
 32};
 33
 34struct audit_cache {
 35	const struct cred *ad_subj_cred;
 36	/* Capabilities go from 0 to CAP_LAST_CAP */
 37	u64 ktime_ns_expiration[CAP_LAST_CAP+1];
 38};
 39
 40static DEFINE_PER_CPU(struct audit_cache, audit_cache);
 41
 42/**
 43 * audit_cb - call back for capability components of audit struct
 44 * @ab: audit buffer   (NOT NULL)
 45 * @va: audit struct to audit data from  (NOT NULL)
 46 */
 47static void audit_cb(struct audit_buffer *ab, void *va)
 48{
 49	struct common_audit_data *sa = va;
 50
 51	audit_log_format(ab, " capname=");
 52	audit_log_untrustedstring(ab, capability_names[sa->u.cap]);
 53}
 54
 55/**
 56 * audit_caps - audit a capability
 57 * @ad: audit data
 58 * @profile: profile being tested for confinement (NOT NULL)
 59 * @cap: capability tested
 60 * @error: error code returned by test
 61 *
 62 * Do auditing of capability and handle, audit/complain/kill modes switching
 63 * and duplicate message elimination.
 64 *
 65 * Returns: 0 or ad->error on success,  error code on failure
 66 */
 67static int audit_caps(struct apparmor_audit_data *ad, struct aa_profile *profile,
 68		      int cap, int error)
 69{
 70	const u64 AUDIT_CACHE_TIMEOUT_NS = 1000*1000*1000; /* 1 second */
 71
 72	struct aa_ruleset *rules = profile->label.rules[0];
 73	struct audit_cache *ent;
 74	int type = AUDIT_APPARMOR_AUTO;
 75
 76	ad->error = error;
 77
 78	if (likely(!error)) {
 79		/* test if auditing is being forced */
 80		if (likely((AUDIT_MODE(profile) != AUDIT_ALL) &&
 81			   !cap_raised(rules->caps.audit, cap)))
 82			return 0;
 83		type = AUDIT_APPARMOR_AUDIT;
 84	} else if (KILL_MODE(profile) ||
 85		   cap_raised(rules->caps.kill, cap)) {
 86		type = AUDIT_APPARMOR_KILL;
 87	} else if (cap_raised(rules->caps.quiet, cap) &&
 88		   AUDIT_MODE(profile) != AUDIT_NOQUIET &&
 89		   AUDIT_MODE(profile) != AUDIT_ALL) {
 90		/* quiet auditing */
 91		return error;
 92	}
 93
 94	/* Do simple duplicate message elimination */
 95	ent = &get_cpu_var(audit_cache);
 96	/* If the capability was never raised the timestamp check would also catch that */
 97	if (ad->subj_cred == ent->ad_subj_cred && ktime_get_ns() <= ent->ktime_ns_expiration[cap]) {
 98		put_cpu_var(audit_cache);
 99		if (COMPLAIN_MODE(profile))
100			return complain_error(error);
101		return error;
102	} else {
103		put_cred(ent->ad_subj_cred);
104		ent->ad_subj_cred = get_cred(ad->subj_cred);
105		ent->ktime_ns_expiration[cap] = ktime_get_ns() + AUDIT_CACHE_TIMEOUT_NS;
106	}
107	put_cpu_var(audit_cache);
108
109	return aa_audit(type, profile, ad, audit_cb);
110}
111
112/**
113 * profile_capable - test if profile allows use of capability @cap
114 * @profile: profile being enforced    (NOT NULL, NOT unconfined)
115 * @cap: capability to test if allowed
116 * @opts: CAP_OPT_NOAUDIT bit determines whether audit record is generated
117 * @ad: audit data (NOT NULL)
118 *
119 * Returns: 0 if allowed else -EPERM
120 */
121static int profile_capable(struct aa_profile *profile, int cap,
122			   unsigned int opts, struct apparmor_audit_data *ad)
123{
124	struct aa_ruleset *rules = profile->label.rules[0];
125	aa_state_t state;
126	int error;
127
128	state = RULE_MEDIATES(rules, ad->class);
129	if (state) {
130		struct aa_perms perms = { };
131		u32 request;
132
133		/* caps broken into 256 x 32 bit permission chunks */
134		state = aa_dfa_next(rules->policy->dfa, state, cap >> 5);
135		request = 1 << (cap & 0x1f);
136		perms = *aa_lookup_perms(rules->policy, state);
137		aa_apply_modes_to_perms(profile, &perms);
138
139		if (opts & CAP_OPT_NOAUDIT) {
140			if (perms.complain & request)
141				ad->info = "optional: no audit";
142			else
143				ad = NULL;
144		}
145		return aa_check_perms(profile, &perms, request, ad,
146				      audit_cb);
147	}
148
149	/* fallback to old caps mediation that doesn't support conditionals */
150	if (cap_raised(rules->caps.allow, cap) &&
151	    !cap_raised(rules->caps.denied, cap))
152		error = 0;
153	else
154		error = -EPERM;
155
156	if (opts & CAP_OPT_NOAUDIT) {
157		if (!COMPLAIN_MODE(profile))
158			return error;
159		/* audit the cap request in complain mode but note that it
160		 * should be optional.
161		 */
162		ad->info = "optional: no audit";
163	}
164
165	return audit_caps(ad, profile, cap, error);
166}
167
168/**
169 * aa_capable - test permission to use capability
170 * @subj_cred: cred we are testing capability against
171 * @label: label being tested for capability (NOT NULL)
172 * @cap: capability to be tested
173 * @opts: CAP_OPT_NOAUDIT bit determines whether audit record is generated
174 *
175 * Look up capability in profile capability set.
176 *
177 * Returns: 0 on success, or else an error code.
178 */
179int aa_capable(const struct cred *subj_cred, struct aa_label *label,
180	       int cap, unsigned int opts)
181{
182	struct aa_profile *profile;
183	int error = 0;
184	DEFINE_AUDIT_DATA(ad, LSM_AUDIT_DATA_CAP, AA_CLASS_CAP, OP_CAPABLE);
185
186	ad.subj_cred = subj_cred;
187	ad.common.u.cap = cap;
188	error = fn_for_each_confined(label, profile,
189			profile_capable(profile, cap, opts, &ad));
190
191	return error;
192}
193
194kernel_cap_t aa_profile_capget(struct aa_profile *profile)
195{
196	struct aa_ruleset *rules = profile->label.rules[0];
197	aa_state_t state;
198
199	state = RULE_MEDIATES(rules, AA_CLASS_CAP);
200	if (state) {
201		kernel_cap_t caps = CAP_EMPTY_SET;
202		int i;
203
204		/* caps broken into up to 256, 32 bit permission chunks */
205		for (i = 0; i < (CAP_LAST_CAP >> 5); i++) {
206			struct aa_perms perms = { };
207			aa_state_t tmp;
208
209			tmp = aa_dfa_next(rules->policy->dfa, state, i);
210			perms = *aa_lookup_perms(rules->policy, tmp);
211			aa_apply_modes_to_perms(profile, &perms);
212			caps.val |= ((u64)(perms.allow)) << (i * 5);
213			caps.val |= ((u64)(perms.complain)) << (i * 5);
214		}
215		return caps;
216	}
217
218	/* fallback to old caps */
219	if (COMPLAIN_MODE(profile))
220		return CAP_FULL_SET;
221
222	return rules->caps.allow;
223}