1/*
  2 * AppArmor security module
  3 *
  4 * This file contains AppArmor functions used to manipulate object security
  5 * contexts.
  6 *
  7 * Copyright (C) 1998-2008 Novell/SUSE
  8 * Copyright 2009-2010 Canonical Ltd.
  9 *
 10 * This program is free software; you can redistribute it and/or
 11 * modify it under the terms of the GNU General Public License as
 12 * published by the Free Software Foundation, version 2 of the
 13 * License.
 14 *
 15 *
 16 * AppArmor sets confinement on every task, via the the aa_task_cxt and
 17 * the aa_task_cxt.profile, both of which are required and are not allowed
 18 * to be NULL.  The aa_task_cxt is not reference counted and is unique
 19 * to each cred (which is reference count).  The profile pointed to by
 20 * the task_cxt is reference counted.
 21 *
 22 * TODO
 23 * If a task uses change_hat it currently does not return to the old
 24 * cred or task context but instead creates a new one.  Ideally the task
 25 * should return to the previous cred if it has not been modified.
 26 *
 27 */
 28
 29#include "include/context.h"
 30#include "include/policy.h"
 31
 32/**
 33 * aa_alloc_task_context - allocate a new task_cxt
 34 * @flags: gfp flags for allocation
 35 *
 36 * Returns: allocated buffer or NULL on failure
 37 */
 38struct aa_task_cxt *aa_alloc_task_context(gfp_t flags)
 39{
 40	return kzalloc(sizeof(struct aa_task_cxt), flags);
 41}
 42
 43/**
 44 * aa_free_task_context - free a task_cxt
 45 * @cxt: task_cxt to free (MAYBE NULL)
 46 */
 47void aa_free_task_context(struct aa_task_cxt *cxt)
 48{
 49	if (cxt) {
 50		aa_put_profile(cxt->profile);
 51		aa_put_profile(cxt->previous);
 52		aa_put_profile(cxt->onexec);
 53
 54		kzfree(cxt);
 55	}
 56}
 57
 58/**
 59 * aa_dup_task_context - duplicate a task context, incrementing reference counts
 60 * @new: a blank task context      (NOT NULL)
 61 * @old: the task context to copy  (NOT NULL)
 62 */
 63void aa_dup_task_context(struct aa_task_cxt *new, const struct aa_task_cxt *old)
 64{
 65	*new = *old;
 66	aa_get_profile(new->profile);
 67	aa_get_profile(new->previous);
 68	aa_get_profile(new->onexec);
 69}
 70
 71/**
 72 * aa_get_task_profile - Get another task's profile
 73 * @task: task to query  (NOT NULL)
 74 *
 75 * Returns: counted reference to @task's profile
 76 */
 77struct aa_profile *aa_get_task_profile(struct task_struct *task)
 78{
 79	struct aa_profile *p;
 80
 81	rcu_read_lock();
 82	p = aa_get_profile(__aa_task_profile(task));
 83	rcu_read_unlock();
 84
 85	return p;
 86}
 87
 88/**
 89 * aa_replace_current_profile - replace the current tasks profiles
 90 * @profile: new profile  (NOT NULL)
 91 *
 92 * Returns: 0 or error on failure
 93 */
 94int aa_replace_current_profile(struct aa_profile *profile)
 95{
 96	struct aa_task_cxt *cxt = current_cxt();
 97	struct cred *new;
 98	BUG_ON(!profile);
 99
100	if (cxt->profile == profile)
101		return 0;
102
103	new  = prepare_creds();
104	if (!new)
105		return -ENOMEM;
106
107	cxt = cred_cxt(new);
108	if (unconfined(profile) || (cxt->profile->ns != profile->ns))
109		/* if switching to unconfined or a different profile namespace
110		 * clear out context state
111		 */
112		aa_clear_task_cxt_trans(cxt);
113
114	/* be careful switching cxt->profile, when racing replacement it
115	 * is possible that cxt->profile->replacedby->profile is the reference
116	 * keeping @profile valid, so make sure to get its reference before
117	 * dropping the reference on cxt->profile */
118	aa_get_profile(profile);
119	aa_put_profile(cxt->profile);
120	cxt->profile = profile;
121
122	commit_creds(new);
123	return 0;
124}
125
126/**
127 * aa_set_current_onexec - set the tasks change_profile to happen onexec
128 * @profile: system profile to set at exec  (MAYBE NULL to clear value)
129 *
130 * Returns: 0 or error on failure
131 */
132int aa_set_current_onexec(struct aa_profile *profile)
133{
134	struct aa_task_cxt *cxt;
135	struct cred *new = prepare_creds();
136	if (!new)
137		return -ENOMEM;
138
139	cxt = cred_cxt(new);
140	aa_get_profile(profile);
141	aa_put_profile(cxt->onexec);
142	cxt->onexec = profile;
143
144	commit_creds(new);
145	return 0;
146}
147
148/**
149 * aa_set_current_hat - set the current tasks hat
150 * @profile: profile to set as the current hat  (NOT NULL)
151 * @token: token value that must be specified to change from the hat
152 *
153 * Do switch of tasks hat.  If the task is currently in a hat
154 * validate the token to match.
155 *
156 * Returns: 0 or error on failure
157 */
158int aa_set_current_hat(struct aa_profile *profile, u64 token)
159{
160	struct aa_task_cxt *cxt;
161	struct cred *new = prepare_creds();
162	if (!new)
163		return -ENOMEM;
164	BUG_ON(!profile);
165
166	cxt = cred_cxt(new);
167	if (!cxt->previous) {
168		/* transfer refcount */
169		cxt->previous = cxt->profile;
170		cxt->token = token;
171	} else if (cxt->token == token) {
172		aa_put_profile(cxt->profile);
173	} else {
174		/* previous_profile && cxt->token != token */
175		abort_creds(new);
176		return -EACCES;
177	}
178	cxt->profile = aa_get_newest_profile(profile);
179	/* clear exec on switching context */
180	aa_put_profile(cxt->onexec);
181	cxt->onexec = NULL;
182
183	commit_creds(new);
184	return 0;
185}
186
187/**
188 * aa_restore_previous_profile - exit from hat context restoring the profile
189 * @token: the token that must be matched to exit hat context
190 *
191 * Attempt to return out of a hat to the previous profile.  The token
192 * must match the stored token value.
193 *
194 * Returns: 0 or error of failure
195 */
196int aa_restore_previous_profile(u64 token)
197{
198	struct aa_task_cxt *cxt;
199	struct cred *new = prepare_creds();
200	if (!new)
201		return -ENOMEM;
202
203	cxt = cred_cxt(new);
204	if (cxt->token != token) {
205		abort_creds(new);
206		return -EACCES;
207	}
208	/* ignore restores when there is no saved profile */
209	if (!cxt->previous) {
210		abort_creds(new);
211		return 0;
212	}
213
214	aa_put_profile(cxt->profile);
215	cxt->profile = aa_get_newest_profile(cxt->previous);
216	BUG_ON(!cxt->profile);
217	/* clear exec && prev information when restoring to previous context */
218	aa_clear_task_cxt_trans(cxt);
219
220	commit_creds(new);
221	return 0;
222}