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-rw-r--r--security/apparmor/task.c293
1 files changed, 293 insertions, 0 deletions
diff --git a/security/apparmor/task.c b/security/apparmor/task.c
new file mode 100644
index 000000000..503dc0877
--- /dev/null
+++ b/security/apparmor/task.c
@@ -0,0 +1,293 @@
+// 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));
+}