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- // SPDX-License-Identifier: GPL-2.0-only
- /*
- * AppArmor security module
- *
- * This file contains AppArmor task related definitions and mediation
- *
- * Copyright 2017 Canonical Ltd.
- *
- * 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 <linux/gfp.h>
- #include <linux/ptrace.h>
- #include "include/audit.h"
- #include "include/cred.h"
- #include "include/policy.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));
- set_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;
- }
- set_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));
- set_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;
- }
- /**
- * audit_ptrace_mask - convert mask to permission string
- * @mask: permission mask to convert
- *
- * Returns: pointer to static string
- */
- static const char *audit_ptrace_mask(u32 mask)
- {
- switch (mask) {
- case MAY_READ:
- return "read";
- case MAY_WRITE:
- return "trace";
- case AA_MAY_BE_READ:
- return "readby";
- case AA_MAY_BE_TRACED:
- return "tracedby";
- }
- return "";
- }
- /* call back to audit ptrace fields */
- static void audit_ptrace_cb(struct audit_buffer *ab, void *va)
- {
- struct common_audit_data *sa = va;
- if (aad(sa)->request & AA_PTRACE_PERM_MASK) {
- audit_log_format(ab, " requested_mask=\"%s\"",
- audit_ptrace_mask(aad(sa)->request));
- if (aad(sa)->denied & AA_PTRACE_PERM_MASK) {
- audit_log_format(ab, " denied_mask=\"%s\"",
- audit_ptrace_mask(aad(sa)->denied));
- }
- }
- audit_log_format(ab, " peer=");
- aa_label_xaudit(ab, labels_ns(aad(sa)->label), aad(sa)->peer,
- FLAGS_NONE, GFP_ATOMIC);
- }
- /* assumes check for PROFILE_MEDIATES is already done */
- /* TODO: conditionals */
- static int profile_ptrace_perm(struct aa_profile *profile,
- struct aa_label *peer, u32 request,
- struct common_audit_data *sa)
- {
- struct aa_perms perms = { };
- aad(sa)->peer = peer;
- aa_profile_match_label(profile, peer, AA_CLASS_PTRACE, request,
- &perms);
- aa_apply_modes_to_perms(profile, &perms);
- return aa_check_perms(profile, &perms, request, sa, audit_ptrace_cb);
- }
- static int profile_tracee_perm(struct aa_profile *tracee,
- struct aa_label *tracer, u32 request,
- struct common_audit_data *sa)
- {
- if (profile_unconfined(tracee) || unconfined(tracer) ||
- !PROFILE_MEDIATES(tracee, AA_CLASS_PTRACE))
- return 0;
- return profile_ptrace_perm(tracee, tracer, request, sa);
- }
- static int profile_tracer_perm(struct aa_profile *tracer,
- struct aa_label *tracee, u32 request,
- struct common_audit_data *sa)
- {
- if (profile_unconfined(tracer))
- return 0;
- if (PROFILE_MEDIATES(tracer, AA_CLASS_PTRACE))
- return profile_ptrace_perm(tracer, tracee, request, sa);
- /* profile uses the old style capability check for ptrace */
- if (&tracer->label == tracee)
- return 0;
- aad(sa)->label = &tracer->label;
- aad(sa)->peer = tracee;
- aad(sa)->request = 0;
- aad(sa)->error = aa_capable(&tracer->label, CAP_SYS_PTRACE,
- CAP_OPT_NONE);
- return aa_audit(AUDIT_APPARMOR_AUTO, tracer, sa, audit_ptrace_cb);
- }
- /**
- * aa_may_ptrace - test if tracer task can trace the tracee
- * @tracer: label of the task doing the tracing (NOT NULL)
- * @tracee: task label to be traced
- * @request: permission request
- *
- * Returns: %0 else error code if permission denied or error
- */
- int aa_may_ptrace(struct aa_label *tracer, struct aa_label *tracee,
- u32 request)
- {
- struct aa_profile *profile;
- u32 xrequest = request << PTRACE_PERM_SHIFT;
- DEFINE_AUDIT_DATA(sa, LSM_AUDIT_DATA_NONE, OP_PTRACE);
- return xcheck_labels(tracer, tracee, profile,
- profile_tracer_perm(profile, tracee, request, &sa),
- profile_tracee_perm(profile, tracer, xrequest, &sa));
- }
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