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/*
* AppArmor security module
*
* This file contains AppArmor task related definitions and mediation
*
* Copyright 2017 Canonical Ltd.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation, version 2 of the
* License.
*
* TODO
* If a task uses change_hat it currently does not return to the old
* cred or task context but instead creates a new one. Ideally the task
* should return to the previous cred if it has not been modified.
*/
#include "include/cred.h"
#include "include/task.h"
/**
* aa_get_task_label - Get another task's label
* @task: task to query (NOT NULL)
*
* Returns: counted reference to @task's label
*/
struct aa_label *aa_get_task_label(struct task_struct *task)
{
struct aa_label *p;
rcu_read_lock();
p = aa_get_newest_label(__aa_task_raw_label(task));
rcu_read_unlock();
return p;
}
/**
* aa_replace_current_label - replace the current tasks label
* @label: new label (NOT NULL)
*
* Returns: 0 or error on failure
*/
int aa_replace_current_label(struct aa_label *label)
{
struct aa_label *old = aa_current_raw_label();
struct aa_task_ctx *ctx = task_ctx(current);
struct cred *new;
AA_BUG(!label);
if (old == label)
return 0;
if (current_cred() != current_real_cred())
return -EBUSY;
new = prepare_creds();
if (!new)
return -ENOMEM;
if (ctx->nnp && label_is_stale(ctx->nnp)) {
struct aa_label *tmp = ctx->nnp;
ctx->nnp = aa_get_newest_label(tmp);
aa_put_label(tmp);
}
if (unconfined(label) || (labels_ns(old) != labels_ns(label)))
/*
* if switching to unconfined or a different label namespace
* clear out context state
*/
aa_clear_task_ctx_trans(task_ctx(current));
/*
* be careful switching cred label, when racing replacement it
* is possible that the cred labels's->proxy->label is the reference
* keeping @label valid, so make sure to get its reference before
* dropping the reference on the cred's label
*/
aa_get_label(label);
aa_put_label(cred_label(new));
cred_label(new) = label;
commit_creds(new);
return 0;
}
/**
* aa_set_current_onexec - set the tasks change_profile to happen onexec
* @label: system label to set at exec (MAYBE NULL to clear value)
* @stack: whether stacking should be done
* Returns: 0 or error on failure
*/
int aa_set_current_onexec(struct aa_label *label, bool stack)
{
struct aa_task_ctx *ctx = task_ctx(current);
aa_get_label(label);
aa_put_label(ctx->onexec);
ctx->onexec = label;
ctx->token = stack;
return 0;
}
/**
* aa_set_current_hat - set the current tasks hat
* @label: label to set as the current hat (NOT NULL)
* @token: token value that must be specified to change from the hat
*
* Do switch of tasks hat. If the task is currently in a hat
* validate the token to match.
*
* Returns: 0 or error on failure
*/
int aa_set_current_hat(struct aa_label *label, u64 token)
{
struct aa_task_ctx *ctx = task_ctx(current);
struct cred *new;
new = prepare_creds();
if (!new)
return -ENOMEM;
AA_BUG(!label);
if (!ctx->previous) {
/* transfer refcount */
ctx->previous = cred_label(new);
ctx->token = token;
} else if (ctx->token == token) {
aa_put_label(cred_label(new));
} else {
/* previous_profile && ctx->token != token */
abort_creds(new);
return -EACCES;
}
cred_label(new) = aa_get_newest_label(label);
/* clear exec on switching context */
aa_put_label(ctx->onexec);
ctx->onexec = NULL;
commit_creds(new);
return 0;
}
/**
* aa_restore_previous_label - exit from hat context restoring previous label
* @token: the token that must be matched to exit hat context
*
* Attempt to return out of a hat to the previous label. The token
* must match the stored token value.
*
* Returns: 0 or error of failure
*/
int aa_restore_previous_label(u64 token)
{
struct aa_task_ctx *ctx = task_ctx(current);
struct cred *new;
if (ctx->token != token)
return -EACCES;
/* ignore restores when there is no saved label */
if (!ctx->previous)
return 0;
new = prepare_creds();
if (!new)
return -ENOMEM;
aa_put_label(cred_label(new));
cred_label(new) = aa_get_newest_label(ctx->previous);
AA_BUG(!cred_label(new));
/* clear exec && prev information when restoring to previous context */
aa_clear_task_ctx_trans(ctx);
commit_creds(new);
return 0;
}
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