security/apparmor/context.c

   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  */
  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  */
  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  */
  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  */
  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  */
 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  */
 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  */
 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 }