184 lines
4.3 KiB
C
184 lines
4.3 KiB
C
/*
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* AppArmor security module
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*
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* This file contains AppArmor task related definitions and mediation
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*
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* Copyright 2017 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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* 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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#include "include/cred.h"
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#include "include/task.h"
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/**
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* aa_get_task_label - Get another task's label
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* @task: task to query (NOT NULL)
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*
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* Returns: counted reference to @task's label
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*/
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struct aa_label *aa_get_task_label(struct task_struct *task)
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{
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struct aa_label *p;
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rcu_read_lock();
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p = aa_get_newest_label(__aa_task_raw_label(task));
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rcu_read_unlock();
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return p;
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}
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/**
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* aa_replace_current_label - replace the current tasks label
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* @label: new label (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_label(struct aa_label *label)
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{
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struct aa_label *old = aa_current_raw_label();
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struct aa_task_ctx *ctx = task_ctx(current);
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struct cred *new;
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AA_BUG(!label);
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if (old == label)
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return 0;
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if (current_cred() != current_real_cred())
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return -EBUSY;
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new = prepare_creds();
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if (!new)
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return -ENOMEM;
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if (ctx->nnp && label_is_stale(ctx->nnp)) {
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struct aa_label *tmp = ctx->nnp;
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ctx->nnp = aa_get_newest_label(tmp);
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aa_put_label(tmp);
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}
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if (unconfined(label) || (labels_ns(old) != labels_ns(label)))
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/*
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* if switching to unconfined or a different label namespace
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* clear out context state
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*/
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aa_clear_task_ctx_trans(task_ctx(current));
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/*
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* be careful switching cred label, when racing replacement it
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* is possible that the cred labels's->proxy->label is the reference
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* keeping @label valid, so make sure to get its reference before
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* dropping the reference on the cred's label
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*/
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aa_get_label(label);
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aa_put_label(cred_label(new));
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cred_label(new) = label;
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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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* @label: system label to set at exec (MAYBE NULL to clear value)
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* @stack: whether stacking should be done
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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_label *label, bool stack)
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{
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struct aa_task_ctx *ctx = task_ctx(current);
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aa_get_label(label);
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aa_put_label(ctx->onexec);
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ctx->onexec = label;
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ctx->token = stack;
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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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* @label: label 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_label *label, u64 token)
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{
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struct aa_task_ctx *ctx = task_ctx(current);
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struct cred *new;
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new = prepare_creds();
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if (!new)
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return -ENOMEM;
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AA_BUG(!label);
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if (!ctx->previous) {
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/* transfer refcount */
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ctx->previous = cred_label(new);
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ctx->token = token;
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} else if (ctx->token == token) {
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aa_put_label(cred_label(new));
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} else {
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/* previous_profile && ctx->token != token */
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abort_creds(new);
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return -EACCES;
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}
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cred_label(new) = aa_get_newest_label(label);
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/* clear exec on switching context */
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aa_put_label(ctx->onexec);
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ctx->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_label - exit from hat context restoring previous label
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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 label. 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_label(u64 token)
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{
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struct aa_task_ctx *ctx = task_ctx(current);
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struct cred *new;
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if (ctx->token != token)
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return -EACCES;
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/* ignore restores when there is no saved label */
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if (!ctx->previous)
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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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aa_put_label(cred_label(new));
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cred_label(new) = aa_get_newest_label(ctx->previous);
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AA_BUG(!cred_label(new));
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/* clear exec && prev information when restoring to previous context */
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aa_clear_task_ctx_trans(ctx);
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commit_creds(new);
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return 0;
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}
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