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 */
aa_alloc_task_context(gfp_t flags)38 struct 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 */
aa_free_task_context(struct aa_task_cxt * cxt)47 void 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 */
aa_dup_task_context(struct aa_task_cxt * new,const struct aa_task_cxt * old)63 void 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 */
aa_replace_current_profile(struct aa_profile * profile)77 int 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 */
aa_set_current_onexec(struct aa_profile * profile)119 int 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 */
aa_set_current_hat(struct aa_profile * profile,u64 token)145 int 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 */
aa_restore_previous_profile(u64 token)183 int 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 }
217