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AppArmor: contexts used in attaching policy to system objects
AppArmor contexts attach profiles and state to tasks, files, etc. when a direct profile reference is not sufficient. Signed-off-by: John Johansen <john.johansen@canonical.com> Signed-off-by: James Morris <jmorris@namei.org>
This commit is contained in:
John Johansen
James Morris
parent
67012e8209
commit
c75afcd153
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/*
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* AppArmor security module
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*
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* This file contains AppArmor functions used to manipulate object security
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* contexts.
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*
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* Copyright (C) 1998-2008 Novell/SUSE
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* Copyright 2009-2010 Canonical Ltd.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation, version 2 of the
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* License.
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*
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*
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* AppArmor sets confinement on every task, via the the aa_task_cxt and
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* the aa_task_cxt.profile, both of which are required and are not allowed
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* to be NULL. The aa_task_cxt is not reference counted and is unique
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* to each cred (which is reference count). The profile pointed to by
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* the task_cxt is reference counted.
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*
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* TODO
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* If a task uses change_hat it currently does not return to the old
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* cred or task context but instead creates a new one. Ideally the task
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* should return to the previous cred if it has not been modified.
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*
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*/
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#include "include/context.h"
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#include "include/policy.h"
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/**
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* aa_alloc_task_context - allocate a new task_cxt
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* @flags: gfp flags for allocation
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*
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* Returns: allocated buffer or NULL on failure
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*/
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struct aa_task_cxt *aa_alloc_task_context(gfp_t flags)
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{
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return kzalloc(sizeof(struct aa_task_cxt), flags);
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}
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/**
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* aa_free_task_context - free a task_cxt
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* @cxt: task_cxt to free (MAYBE NULL)
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*/
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void aa_free_task_context(struct aa_task_cxt *cxt)
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{
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if (cxt) {
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aa_put_profile(cxt->profile);
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aa_put_profile(cxt->previous);
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aa_put_profile(cxt->onexec);
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kzfree(cxt);
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}
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}
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/**
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* aa_dup_task_context - duplicate a task context, incrementing reference counts
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* @new: a blank task context (NOT NULL)
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* @old: the task context to copy (NOT NULL)
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*/
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void aa_dup_task_context(struct aa_task_cxt *new, const struct aa_task_cxt *old)
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{
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*new = *old;
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aa_get_profile(new->profile);
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aa_get_profile(new->previous);
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aa_get_profile(new->onexec);
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}
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/**
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* aa_replace_current_profile - replace the current tasks profiles
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* @profile: new profile (NOT NULL)
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*
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* Returns: 0 or error on failure
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*/
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int aa_replace_current_profile(struct aa_profile *profile)
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{
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struct aa_task_cxt *cxt = current_cred()->security;
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struct cred *new;
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BUG_ON(!profile);
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if (cxt->profile == profile)
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return 0;
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new = prepare_creds();
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if (!new)
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return -ENOMEM;
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cxt = new->security;
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if (unconfined(profile) || (cxt->profile->ns != profile->ns)) {
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/* if switching to unconfined or a different profile namespace
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* clear out context state
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*/
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aa_put_profile(cxt->previous);
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aa_put_profile(cxt->onexec);
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cxt->previous = NULL;
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cxt->onexec = NULL;
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cxt->token = 0;
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}
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/* be careful switching cxt->profile, when racing replacement it
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* is possible that cxt->profile->replacedby is the reference keeping
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* @profile valid, so make sure to get its reference before dropping
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* the reference on cxt->profile */
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aa_get_profile(profile);
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aa_put_profile(cxt->profile);
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cxt->profile = profile;
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commit_creds(new);
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return 0;
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}
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/**
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* aa_set_current_onexec - set the tasks change_profile to happen onexec
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* @profile: system profile to set at exec (MAYBE NULL to clear value)
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*
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* Returns: 0 or error on failure
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*/
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int aa_set_current_onexec(struct aa_profile *profile)
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{
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struct aa_task_cxt *cxt;
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struct cred *new = prepare_creds();
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if (!new)
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return -ENOMEM;
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cxt = new->security;
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aa_get_profile(profile);
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aa_put_profile(cxt->onexec);
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cxt->onexec = profile;
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commit_creds(new);
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return 0;
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}
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/**
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* aa_set_current_hat - set the current tasks hat
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* @profile: profile to set as the current hat (NOT NULL)
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* @token: token value that must be specified to change from the hat
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*
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* Do switch of tasks hat. If the task is currently in a hat
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* validate the token to match.
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*
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* Returns: 0 or error on failure
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*/
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int aa_set_current_hat(struct aa_profile *profile, u64 token)
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{
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struct aa_task_cxt *cxt;
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struct cred *new = prepare_creds();
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if (!new)
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return -ENOMEM;
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BUG_ON(!profile);
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cxt = new->security;
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if (!cxt->previous) {
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/* transfer refcount */
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cxt->previous = cxt->profile;
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cxt->token = token;
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} else if (cxt->token == token) {
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aa_put_profile(cxt->profile);
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} else {
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/* previous_profile && cxt->token != token */
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abort_creds(new);
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return -EACCES;
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}
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cxt->profile = aa_get_profile(aa_newest_version(profile));
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/* clear exec on switching context */
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aa_put_profile(cxt->onexec);
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cxt->onexec = NULL;
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commit_creds(new);
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return 0;
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}
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/**
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* aa_restore_previous_profile - exit from hat context restoring the profile
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* @token: the token that must be matched to exit hat context
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*
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* Attempt to return out of a hat to the previous profile. The token
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* must match the stored token value.
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*
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* Returns: 0 or error of failure
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*/
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int aa_restore_previous_profile(u64 token)
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{
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struct aa_task_cxt *cxt;
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struct cred *new = prepare_creds();
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if (!new)
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return -ENOMEM;
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cxt = new->security;
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if (cxt->token != token) {
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abort_creds(new);
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return -EACCES;
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}
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/* ignore restores when there is no saved profile */
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if (!cxt->previous) {
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abort_creds(new);
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return 0;
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}
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aa_put_profile(cxt->profile);
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cxt->profile = aa_newest_version(cxt->previous);
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BUG_ON(!cxt->profile);
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if (unlikely(cxt->profile != cxt->previous)) {
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aa_get_profile(cxt->profile);
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aa_put_profile(cxt->previous);
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}
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/* clear exec && prev information when restoring to previous context */
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cxt->previous = NULL;
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cxt->token = 0;
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aa_put_profile(cxt->onexec);
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cxt->onexec = NULL;
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commit_creds(new);
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return 0;
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}
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@ -0,0 +1,154 @@
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/*
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* AppArmor security module
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*
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* This file contains AppArmor contexts used to associate "labels" to objects.
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*
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* Copyright (C) 1998-2008 Novell/SUSE
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* Copyright 2009-2010 Canonical Ltd.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation, version 2 of the
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* License.
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*/
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#ifndef __AA_CONTEXT_H
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#define __AA_CONTEXT_H
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#include <linux/cred.h>
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#include <linux/slab.h>
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#include <linux/sched.h>
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#include "policy.h"
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/* struct aa_file_cxt - the AppArmor context the file was opened in
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* @perms: the permission the file was opened with
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*
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* The file_cxt could currently be directly stored in file->f_security
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* as the profile reference is now stored in the f_cred. However the
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* cxt struct will expand in the future so we keep the struct.
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*/
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struct aa_file_cxt {
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u16 allow;
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};
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/**
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* aa_alloc_file_context - allocate file_cxt
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* @gfp: gfp flags for allocation
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*
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* Returns: file_cxt or NULL on failure
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*/
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static inline struct aa_file_cxt *aa_alloc_file_context(gfp_t gfp)
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{
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return kzalloc(sizeof(struct aa_file_cxt), gfp);
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}
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/**
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* aa_free_file_context - free a file_cxt
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* @cxt: file_cxt to free (MAYBE_NULL)
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*/
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static inline void aa_free_file_context(struct aa_file_cxt *cxt)
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{
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if (cxt)
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kzfree(cxt);
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}
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/**
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* struct aa_task_cxt - primary label for confined tasks
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* @profile: the current profile (NOT NULL)
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* @exec: profile to transition to on next exec (MAYBE NULL)
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* @previous: profile the task may return to (MAYBE NULL)
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* @token: magic value the task must know for returning to @previous_profile
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*
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* Contains the task's current profile (which could change due to
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* change_hat). Plus the hat_magic needed during change_hat.
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*
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* TODO: make so a task can be confined by a stack of contexts
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*/
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struct aa_task_cxt {
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struct aa_profile *profile;
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struct aa_profile *onexec;
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struct aa_profile *previous;
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u64 token;
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};
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struct aa_task_cxt *aa_alloc_task_context(gfp_t flags);
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void aa_free_task_context(struct aa_task_cxt *cxt);
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void aa_dup_task_context(struct aa_task_cxt *new,
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const struct aa_task_cxt *old);
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int aa_replace_current_profile(struct aa_profile *profile);
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int aa_set_current_onexec(struct aa_profile *profile);
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int aa_set_current_hat(struct aa_profile *profile, u64 token);
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int aa_restore_previous_profile(u64 cookie);
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/**
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* __aa_task_is_confined - determine if @task has any confinement
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* @task: task to check confinement of (NOT NULL)
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*
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* If @task != current needs to be called in RCU safe critical section
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*/
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static inline bool __aa_task_is_confined(struct task_struct *task)
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{
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struct aa_task_cxt *cxt = __task_cred(task)->security;
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BUG_ON(!cxt || !cxt->profile);
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if (unconfined(aa_newest_version(cxt->profile)))
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return 0;
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return 1;
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}
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/**
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* aa_cred_profile - obtain cred's profiles
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* @cred: cred to obtain profiles from (NOT NULL)
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*
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* Returns: confining profile
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*
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* does NOT increment reference count
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*/
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static inline struct aa_profile *aa_cred_profile(const struct cred *cred)
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{
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struct aa_task_cxt *cxt = cred->security;
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BUG_ON(!cxt || !cxt->profile);
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return aa_newest_version(cxt->profile);
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}
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/**
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* __aa_current_profile - find the current tasks confining profile
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*
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* Returns: up to date confining profile or the ns unconfined profile (NOT NULL)
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*
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* This fn will not update the tasks cred to the most up to date version
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* of the profile so it is safe to call when inside of locks.
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*/
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static inline struct aa_profile *__aa_current_profile(void)
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{
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return aa_cred_profile(current_cred());
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}
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/**
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* aa_current_profile - find the current tasks confining profile and do updates
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*
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* Returns: up to date confining profile or the ns unconfined profile (NOT NULL)
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*
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* This fn will update the tasks cred structure if the profile has been
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* replaced. Not safe to call inside locks
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*/
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static inline struct aa_profile *aa_current_profile(void)
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{
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const struct aa_task_cxt *cxt = current_cred()->security;
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struct aa_profile *profile;
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BUG_ON(!cxt || !cxt->profile);
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profile = aa_newest_version(cxt->profile);
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/*
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* Whether or not replacement succeeds, use newest profile so
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* there is no need to update it after replacement.
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*/
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if (unlikely((cxt->profile != profile)))
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aa_replace_current_profile(profile);
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return profile;
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}
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#endif /* __AA_CONTEXT_H */
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