security/apparmor/task.c - linux - Git at Google

 // 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
  */
 void 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;
 }

 /**
  * 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_cred: cred of task doing the tracing  (NOT NULL)
  * @tracer: label of the task doing the tracing  (NOT NULL)
  * @tracee_cred: cred of task to be traced
  * @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));
 }

 /* call back to audit ptrace fields */
 static void audit_ns_cb(struct audit_buffer *ab, void *va)
 {
 	struct apparmor_audit_data *ad = aad_of_va(va);

 	if (ad->request & AA_USERNS_CREATE)
 		audit_log_format(ab, " requested=\"userns_create\"");

 	if (ad->denied & AA_USERNS_CREATE)
 		audit_log_format(ab, " denied=\"userns_create\"");
 }

 int aa_profile_ns_perm(struct aa_profile *profile,
 		       struct apparmor_audit_data *ad,
 		       u32 request)
 {
 	struct aa_perms perms = { };
 	int error = 0;

 	ad->subj_label = &profile->label;
 	ad->request = request;

 	if (!profile_unconfined(profile)) {
 		struct aa_ruleset *rules = list_first_entry(&profile->rules,
 							    typeof(*rules),
 							    list);
 		aa_state_t state;

 		state = RULE_MEDIATES(rules, ad->class);
 		if (!state)
 			/* TODO: add flag to complain about unmediated */
 			return 0;
 		perms = *aa_lookup_perms(rules->policy, state);
 		aa_apply_modes_to_perms(profile, &perms);
 		error = aa_check_perms(profile, &perms, request, ad,
 				       audit_ns_cb);
 	}

 	return error;
 }
	// 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
	*/
	void 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;
	}

	/**
	* 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_cred: cred of task doing the tracing (NOT NULL)
	* @tracer: label of the task doing the tracing (NOT NULL)
	* @tracee_cred: cred of task to be traced
	* @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));
	}

	/* call back to audit ptrace fields */
	static void audit_ns_cb(struct audit_buffer ab, void va)
	{
	struct apparmor_audit_data *ad = aad_of_va(va);

	if (ad->request & AA_USERNS_CREATE)
	audit_log_format(ab, " requested=\"userns_create\"");

	if (ad->denied & AA_USERNS_CREATE)
	audit_log_format(ab, " denied=\"userns_create\"");
	}

	int aa_profile_ns_perm(struct aa_profile *profile,
	struct apparmor_audit_data *ad,
	u32 request)
	{
	struct aa_perms perms = { };
	int error = 0;

	ad->subj_label = &profile->label;
	ad->request = request;

	if (!profile_unconfined(profile)) {
	struct aa_ruleset *rules = list_first_entry(&profile->rules,
	typeof(*rules),
	list);
	aa_state_t state;

	state = RULE_MEDIATES(rules, ad->class);
	if (!state)
	/* TODO: add flag to complain about unmediated */
	return 0;
	perms = *aa_lookup_perms(rules->policy, state);
	aa_apply_modes_to_perms(profile, &perms);
	error = aa_check_perms(profile, &perms, request, ad,
	audit_ns_cb);
	}

	return error;
	}