1 files changed, 303 insertions, 0 deletions
diff --git a/security/apparmor/task.c b/security/apparmor/task.c
new file mode 100644
index 0000000000..0d7af707cc
--- /dev/null
+++ b/security/apparmor/task.c
@@ -0,0 +1,303 @@
+// 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_cred_label(__task_cred(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;
+	struct apparmor_audit_data *ad = aad(sa);
+
+	if (ad->request & AA_PTRACE_PERM_MASK) {
+		audit_log_format(ab, " requested_mask=\"%s\"",
+				 audit_ptrace_mask(ad->request));
+
+		if (ad->denied & AA_PTRACE_PERM_MASK) {
+			audit_log_format(ab, " denied_mask=\"%s\"",
+					 audit_ptrace_mask(ad->denied));
+		}
+	}
+	audit_log_format(ab, " peer=");
+	aa_label_xaudit(ab, labels_ns(ad->subj_label), ad->peer,
+			FLAGS_NONE, GFP_ATOMIC);
+}
+
+/* assumes check for RULE_MEDIATES is already done */
+/* TODO: conditionals */
+static int profile_ptrace_perm(const struct cred *cred,
+			       struct aa_profile *profile,
+			       struct aa_label *peer, u32 request,
+			       struct apparmor_audit_data *ad)
+{
+	struct aa_ruleset *rules = list_first_entry(&profile->rules,
+						    typeof(*rules), list);
+	struct aa_perms perms = { };
+
+	ad->subj_cred = cred;
+	ad->peer = peer;
+	aa_profile_match_label(profile, rules, peer, AA_CLASS_PTRACE, request,
+			       &perms);
+	aa_apply_modes_to_perms(profile, &perms);
+	return aa_check_perms(profile, &perms, request, ad, audit_ptrace_cb);
+}
+
+static int profile_tracee_perm(const struct cred *cred,
+			       struct aa_profile *tracee,
+			       struct aa_label *tracer, u32 request,
+			       struct apparmor_audit_data *ad)
+{
+	if (profile_unconfined(tracee) || unconfined(tracer) ||
+	    !ANY_RULE_MEDIATES(&tracee->rules, AA_CLASS_PTRACE))
+		return 0;
+
+	return profile_ptrace_perm(cred, tracee, tracer, request, ad);
+}
+
+static int profile_tracer_perm(const struct cred *cred,
+			       struct aa_profile *tracer,
+			       struct aa_label *tracee, u32 request,
+			       struct apparmor_audit_data *ad)
+{
+	if (profile_unconfined(tracer))
+		return 0;
+
+	if (ANY_RULE_MEDIATES(&tracer->rules, AA_CLASS_PTRACE))
+		return profile_ptrace_perm(cred, tracer, tracee, request, ad);
+
+	/* profile uses the old style capability check for ptrace */
+	if (&tracer->label == tracee)
+		return 0;
+
+	ad->subj_label = &tracer->label;
+	ad->peer = tracee;
+	ad->request = 0;
+	ad->error = aa_capable(cred, &tracer->label, CAP_SYS_PTRACE,
+			       CAP_OPT_NONE);
+
+	return aa_audit(AUDIT_APPARMOR_AUTO, tracer, ad, 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(const struct cred *tracer_cred, struct aa_label *tracer,
+		  const struct cred *tracee_cred, struct aa_label *tracee,
+		  u32 request)
+{
+	struct aa_profile *profile;
+	u32 xrequest = request << PTRACE_PERM_SHIFT;
+	DEFINE_AUDIT_DATA(sa, LSM_AUDIT_DATA_NONE, AA_CLASS_PTRACE, OP_PTRACE);
+
+	return xcheck_labels(tracer, tracee, profile,
+			profile_tracer_perm(tracer_cred, profile, tracee,
+					    request, &sa),
+			profile_tracee_perm(tracee_cred, profile, tracer,
+					    xrequest, &sa));
+}