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eac931254d
AppArmor split out task oriented controls to their own logical file a while ago. Ptrace mediation is better grouped with task than ipc, so move it. Signed-off-by: John Johansen <john.johansen@canonical.com>
294 lines
7.2 KiB
C
294 lines
7.2 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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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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* 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 <linux/gfp.h>
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#include <linux/ptrace.h>
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#include "include/audit.h"
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#include "include/cred.h"
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#include "include/policy.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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set_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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set_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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set_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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/**
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* audit_ptrace_mask - convert mask to permission string
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* @mask: permission mask to convert
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*
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* Returns: pointer to static string
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*/
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static const char *audit_ptrace_mask(u32 mask)
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{
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switch (mask) {
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case MAY_READ:
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return "read";
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case MAY_WRITE:
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return "trace";
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case AA_MAY_BE_READ:
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return "readby";
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case AA_MAY_BE_TRACED:
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return "tracedby";
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}
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return "";
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}
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/* call back to audit ptrace fields */
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static void audit_ptrace_cb(struct audit_buffer *ab, void *va)
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{
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struct common_audit_data *sa = va;
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if (aad(sa)->request & AA_PTRACE_PERM_MASK) {
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audit_log_format(ab, " requested_mask=\"%s\"",
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audit_ptrace_mask(aad(sa)->request));
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if (aad(sa)->denied & AA_PTRACE_PERM_MASK) {
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audit_log_format(ab, " denied_mask=\"%s\"",
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audit_ptrace_mask(aad(sa)->denied));
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}
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}
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audit_log_format(ab, " peer=");
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aa_label_xaudit(ab, labels_ns(aad(sa)->label), aad(sa)->peer,
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FLAGS_NONE, GFP_ATOMIC);
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}
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/* assumes check for PROFILE_MEDIATES is already done */
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/* TODO: conditionals */
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static int profile_ptrace_perm(struct aa_profile *profile,
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struct aa_label *peer, u32 request,
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struct common_audit_data *sa)
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{
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struct aa_perms perms = { };
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aad(sa)->peer = peer;
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aa_profile_match_label(profile, peer, AA_CLASS_PTRACE, request,
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&perms);
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aa_apply_modes_to_perms(profile, &perms);
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return aa_check_perms(profile, &perms, request, sa, audit_ptrace_cb);
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}
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static int profile_tracee_perm(struct aa_profile *tracee,
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struct aa_label *tracer, u32 request,
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struct common_audit_data *sa)
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{
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if (profile_unconfined(tracee) || unconfined(tracer) ||
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!PROFILE_MEDIATES(tracee, AA_CLASS_PTRACE))
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return 0;
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return profile_ptrace_perm(tracee, tracer, request, sa);
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}
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static int profile_tracer_perm(struct aa_profile *tracer,
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struct aa_label *tracee, u32 request,
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struct common_audit_data *sa)
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{
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if (profile_unconfined(tracer))
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return 0;
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if (PROFILE_MEDIATES(tracer, AA_CLASS_PTRACE))
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return profile_ptrace_perm(tracer, tracee, request, sa);
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/* profile uses the old style capability check for ptrace */
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if (&tracer->label == tracee)
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return 0;
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aad(sa)->label = &tracer->label;
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aad(sa)->peer = tracee;
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aad(sa)->request = 0;
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aad(sa)->error = aa_capable(&tracer->label, CAP_SYS_PTRACE,
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CAP_OPT_NONE);
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return aa_audit(AUDIT_APPARMOR_AUTO, tracer, sa, audit_ptrace_cb);
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}
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/**
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* aa_may_ptrace - test if tracer task can trace the tracee
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* @tracer: label of the task doing the tracing (NOT NULL)
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* @tracee: task label to be traced
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* @request: permission request
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*
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* Returns: %0 else error code if permission denied or error
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*/
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int aa_may_ptrace(struct aa_label *tracer, struct aa_label *tracee,
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u32 request)
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{
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struct aa_profile *profile;
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u32 xrequest = request << PTRACE_PERM_SHIFT;
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DEFINE_AUDIT_DATA(sa, LSM_AUDIT_DATA_NONE, OP_PTRACE);
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return xcheck_labels(tracer, tracee, profile,
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profile_tracer_perm(profile, tracee, request, &sa),
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profile_tracee_perm(profile, tracer, xrequest, &sa));
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}
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