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_replace_current_profile - replace the current tasks profiles
 73 * @profile: new profile  (NOT NULL)
 74 *
 75 * Returns: 0 or error on failure
 76 */
 77int aa_replace_current_profile(struct aa_profile *profile)
 78{
 79	struct aa_task_cxt *cxt = current_cred()->security;
 80	struct cred *new;
 81	BUG_ON(!profile);
 82
 83	if (cxt->profile == profile)
 84		return 0;
 85
 86	new  = prepare_creds();
 87	if (!new)
 88		return -ENOMEM;
 89
 90	cxt = new->security;
 91	if (unconfined(profile) || (cxt->profile->ns != profile->ns)) {
 92		/* if switching to unconfined or a different profile namespace
 93		 * clear out context state
 94		 */
 95		aa_put_profile(cxt->previous);
 96		aa_put_profile(cxt->onexec);
 97		cxt->previous = NULL;
 98		cxt->onexec = NULL;
 99		cxt->token = 0;
100	}
101	/* be careful switching cxt->profile, when racing replacement it
102	 * is possible that cxt->profile->replacedby is the reference keeping
103	 * @profile valid, so make sure to get its reference before dropping
104	 * the reference on cxt->profile */
105	aa_get_profile(profile);
106	aa_put_profile(cxt->profile);
107	cxt->profile = profile;
108
109	commit_creds(new);
110	return 0;
111}
112
113/**
114 * aa_set_current_onexec - set the tasks change_profile to happen onexec
115 * @profile: system profile to set at exec  (MAYBE NULL to clear value)
116 *
117 * Returns: 0 or error on failure
118 */
119int aa_set_current_onexec(struct aa_profile *profile)
120{
121	struct aa_task_cxt *cxt;
122	struct cred *new = prepare_creds();
123	if (!new)
124		return -ENOMEM;
125
126	cxt = new->security;
127	aa_get_profile(profile);
128	aa_put_profile(cxt->onexec);
129	cxt->onexec = profile;
130
131	commit_creds(new);
132	return 0;
133}
134
135/**
136 * aa_set_current_hat - set the current tasks hat
137 * @profile: profile to set as the current hat  (NOT NULL)
138 * @token: token value that must be specified to change from the hat
139 *
140 * Do switch of tasks hat.  If the task is currently in a hat
141 * validate the token to match.
142 *
143 * Returns: 0 or error on failure
144 */
145int aa_set_current_hat(struct aa_profile *profile, u64 token)
146{
147	struct aa_task_cxt *cxt;
148	struct cred *new = prepare_creds();
149	if (!new)
150		return -ENOMEM;
151	BUG_ON(!profile);
152
153	cxt = new->security;
154	if (!cxt->previous) {
155		/* transfer refcount */
156		cxt->previous = cxt->profile;
157		cxt->token = token;
158	} else if (cxt->token == token) {
159		aa_put_profile(cxt->profile);
160	} else {
161		/* previous_profile && cxt->token != token */
162		abort_creds(new);
163		return -EACCES;
164	}
165	cxt->profile = aa_get_profile(aa_newest_version(profile));
166	/* clear exec on switching context */
167	aa_put_profile(cxt->onexec);
168	cxt->onexec = NULL;
169
170	commit_creds(new);
171	return 0;
172}
173
174/**
175 * aa_restore_previous_profile - exit from hat context restoring the profile
176 * @token: the token that must be matched to exit hat context
177 *
178 * Attempt to return out of a hat to the previous profile.  The token
179 * must match the stored token value.
180 *
181 * Returns: 0 or error of failure
182 */
183int aa_restore_previous_profile(u64 token)
184{
185	struct aa_task_cxt *cxt;
186	struct cred *new = prepare_creds();
187	if (!new)
188		return -ENOMEM;
189
190	cxt = new->security;
191	if (cxt->token != token) {
192		abort_creds(new);
193		return -EACCES;
194	}
195	/* ignore restores when there is no saved profile */
196	if (!cxt->previous) {
197		abort_creds(new);
198		return 0;
199	}
200
201	aa_put_profile(cxt->profile);
202	cxt->profile = aa_newest_version(cxt->previous);
203	BUG_ON(!cxt->profile);
204	if (unlikely(cxt->profile != cxt->previous)) {
205		aa_get_profile(cxt->profile);
206		aa_put_profile(cxt->previous);
207	}
208	/* clear exec && prev information when restoring to previous context */
209	cxt->previous = NULL;
210	cxt->token = 0;
211	aa_put_profile(cxt->onexec);
212	cxt->onexec = NULL;
213
214	commit_creds(new);
215	return 0;
216}