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Subject[PATCH 11/13] kdbus: add policy database implementation
Date
From: Daniel Mack <daniel@zonque.org>

This patch adds the policy database implementation.

A policy databases restrict the possibilities of connections to own,
see and talk to well-known names. It can be associated with a bus
(through a policy holder connection) or a custom endpoint.

By default, buses have an empty policy database that is augmented on
demand when a policy holder connection is instantiated.

Policies are set through KDBUS_CMD_HELLO (when creating a policy
holder connection), KDBUS_CMD_CONN_UPDATE (when updating a policy
holder connection), KDBUS_CMD_EP_MAKE (creating a custom endpoint)
or KDBUS_CMD_EP_UPDATE (updating a custom endpoint). In all cases,
the name and policy access information is stored in items of type
KDBUS_ITEM_NAME and KDBUS_ITEM_POLICY_ACCESS.

See Documentation/kdbus.txt for more details.

Signed-off-by: Daniel Mack <daniel@zonque.org>
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Djalal Harouni <tixxdz@opendz.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
ipc/kdbus/policy.c | 481 +++++++++++++++++++++++++++++++++++++++++++++++++++++
ipc/kdbus/policy.h | 51 ++++++
2 files changed, 532 insertions(+)
create mode 100644 ipc/kdbus/policy.c
create mode 100644 ipc/kdbus/policy.h

diff --git a/ipc/kdbus/policy.c b/ipc/kdbus/policy.c
new file mode 100644
index 000000000000..0b60f5f381bf
--- /dev/null
+++ b/ipc/kdbus/policy.c
@@ -0,0 +1,481 @@
+/*
+ * Copyright (C) 2013-2014 Kay Sievers
+ * Copyright (C) 2013-2014 Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+ * Copyright (C) 2013-2014 Daniel Mack <daniel@zonque.org>
+ * Copyright (C) 2013-2014 David Herrmann <dh.herrmann@gmail.com>
+ * Copyright (C) 2013-2014 Linux Foundation
+ * Copyright (C) 2014 Djalal Harouni
+ *
+ * kdbus is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU Lesser General Public License as published by the
+ * Free Software Foundation; either version 2.1 of the License, or (at
+ * your option) any later version.
+ */
+
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/mutex.h>
+#include <linux/sched.h>
+#include <linux/sizes.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+
+#include "bus.h"
+#include "connection.h"
+#include "domain.h"
+#include "item.h"
+#include "names.h"
+#include "policy.h"
+
+#define KDBUS_POLICY_HASH_SIZE 64
+
+/**
+ * struct kdbus_policy_db_entry_access - a database entry access item
+ * @type: One of KDBUS_POLICY_ACCESS_* types
+ * @access: Access to grant. One of KDBUS_POLICY_*
+ * @uid: For KDBUS_POLICY_ACCESS_USER, the global uid
+ * @gid: For KDBUS_POLICY_ACCESS_GROUP, the global gid
+ * @list: List entry item for the entry's list
+ *
+ * This is the internal version of struct kdbus_policy_db_access.
+ */
+struct kdbus_policy_db_entry_access {
+ u8 type; /* USER, GROUP, WORLD */
+ u8 access; /* OWN, TALK, SEE */
+ union {
+ kuid_t uid; /* global uid */
+ kgid_t gid; /* global gid */
+ };
+ struct list_head list;
+};
+
+/**
+ * struct kdbus_policy_db_entry - a policy database entry
+ * @name: The name to match the policy entry against
+ * @hentry: The hash entry for the database's entries_hash
+ * @access_list: List head for keeping tracks of the entry's
+ * access items.
+ * @owner: The owner of this entry. Can be a kdbus_conn or
+ * a kdbus_ep object.
+ * @wildcard: The name is a wildcard, such as ending on '.*'
+ */
+struct kdbus_policy_db_entry {
+ char *name;
+ struct hlist_node hentry;
+ struct list_head access_list;
+ const void *owner;
+ bool wildcard:1;
+};
+
+static void kdbus_policy_entry_free(struct kdbus_policy_db_entry *e)
+{
+ struct kdbus_policy_db_entry_access *a, *tmp;
+
+ list_for_each_entry_safe(a, tmp, &e->access_list, list) {
+ list_del(&a->list);
+ kfree(a);
+ }
+
+ kfree(e->name);
+ kfree(e);
+}
+
+static const struct kdbus_policy_db_entry *
+kdbus_policy_lookup(struct kdbus_policy_db *db, const char *name, u32 hash)
+{
+ struct kdbus_policy_db_entry *e;
+ const char *dot;
+ size_t len;
+
+ /* find exact match */
+ hash_for_each_possible(db->entries_hash, e, hentry, hash)
+ if (strcmp(e->name, name) == 0 && !e->wildcard)
+ return e;
+
+ /* find wildcard match */
+
+ dot = strrchr(name, '.');
+ if (!dot)
+ return NULL;
+
+ len = dot - name;
+ hash = kdbus_strnhash(name, len);
+
+ hash_for_each_possible(db->entries_hash, e, hentry, hash)
+ if (e->wildcard && !strncmp(e->name, name, len) &&
+ !e->name[len])
+ return e;
+
+ return NULL;
+}
+
+/**
+ * kdbus_policy_db_clear - release all memory from a policy db
+ * @db: The policy database
+ */
+void kdbus_policy_db_clear(struct kdbus_policy_db *db)
+{
+ struct kdbus_policy_db_entry *e;
+ struct hlist_node *tmp;
+ unsigned int i;
+
+ /* purge entries */
+ down_write(&db->entries_rwlock);
+ hash_for_each_safe(db->entries_hash, i, tmp, e, hentry) {
+ hash_del(&e->hentry);
+ kdbus_policy_entry_free(e);
+ }
+ up_write(&db->entries_rwlock);
+}
+
+/**
+ * kdbus_policy_db_init() - initialize a new policy database
+ * @db: The location of the database
+ *
+ * This initializes a new policy-db. The underlying memory must have been
+ * cleared to zero by the caller.
+ */
+void kdbus_policy_db_init(struct kdbus_policy_db *db)
+{
+ hash_init(db->entries_hash);
+ init_rwsem(&db->entries_rwlock);
+}
+
+/**
+ * kdbus_policy_query_unlocked() - Query the policy database
+ * @db: Policy database
+ * @cred: Credentials to test against
+ * @name: Name to query
+ * @hash: Hash value of @name
+ *
+ * Same as kdbus_policy_query() but requires the caller to lock the policy
+ * database against concurrent writes.
+ *
+ * Return: The highest KDBUS_POLICY_* access type found, or -EPERM if none.
+ */
+int kdbus_policy_query_unlocked(struct kdbus_policy_db *db,
+ const struct cred *cred, const char *name,
+ unsigned int hash)
+{
+ struct kdbus_policy_db_entry_access *a;
+ const struct kdbus_policy_db_entry *e;
+ int i, highest = -EPERM;
+
+ e = kdbus_policy_lookup(db, name, hash);
+ if (!e)
+ return -EPERM;
+
+ list_for_each_entry(a, &e->access_list, list) {
+ if ((int)a->access <= highest)
+ continue;
+
+ switch (a->type) {
+ case KDBUS_POLICY_ACCESS_USER:
+ if (uid_eq(cred->euid, a->uid))
+ highest = a->access;
+ break;
+ case KDBUS_POLICY_ACCESS_GROUP:
+ if (gid_eq(cred->egid, a->gid)) {
+ highest = a->access;
+ break;
+ }
+
+ for (i = 0; i < cred->group_info->ngroups; i++) {
+ kgid_t gid = GROUP_AT(cred->group_info, i);
+
+ if (gid_eq(gid, a->gid)) {
+ highest = a->access;
+ break;
+ }
+ }
+
+ break;
+ case KDBUS_POLICY_ACCESS_WORLD:
+ highest = a->access;
+ break;
+ }
+
+ /* OWN is the highest possible policy */
+ if (highest >= KDBUS_POLICY_OWN)
+ break;
+ }
+
+ return highest;
+}
+
+/**
+ * kdbus_policy_query() - Query the policy database
+ * @db: Policy database
+ * @cred: Credentials to test against
+ * @name: Name to query
+ * @hash: Hash value of @name
+ *
+ * Query the policy database @db for the access rights of @cred to the name
+ * @name. The access rights of @cred are returned, or -EPERM if no access is
+ * granted.
+ *
+ * This call effectively searches for the highest access-right granted to
+ * @cred. The caller should really cache those as policy lookups are rather
+ * expensive.
+ *
+ * Return: The highest KDBUS_POLICY_* access type found, or -EPERM if none.
+ */
+int kdbus_policy_query(struct kdbus_policy_db *db, const struct cred *cred,
+ const char *name, unsigned int hash)
+{
+ int ret;
+
+ down_read(&db->entries_rwlock);
+ ret = kdbus_policy_query_unlocked(db, cred, name, hash);
+ up_read(&db->entries_rwlock);
+
+ return ret;
+}
+
+static void __kdbus_policy_remove_owner(struct kdbus_policy_db *db,
+ const void *owner)
+{
+ struct kdbus_policy_db_entry *e;
+ struct hlist_node *tmp;
+ int i;
+
+ hash_for_each_safe(db->entries_hash, i, tmp, e, hentry)
+ if (e->owner == owner) {
+ hash_del(&e->hentry);
+ kdbus_policy_entry_free(e);
+ }
+}
+
+/**
+ * kdbus_policy_remove_owner() - remove all entries related to a connection
+ * @db: The policy database
+ * @owner: The connection which items to remove
+ */
+void kdbus_policy_remove_owner(struct kdbus_policy_db *db,
+ const void *owner)
+{
+ down_write(&db->entries_rwlock);
+ __kdbus_policy_remove_owner(db, owner);
+ up_write(&db->entries_rwlock);
+}
+
+/*
+ * Convert user provided policy access to internal kdbus policy
+ * access
+ */
+static struct kdbus_policy_db_entry_access *
+kdbus_policy_make_access(const struct kdbus_policy_access *uaccess)
+{
+ int ret;
+ struct kdbus_policy_db_entry_access *a;
+
+ a = kzalloc(sizeof(*a), GFP_KERNEL);
+ if (!a)
+ return ERR_PTR(-ENOMEM);
+
+ ret = -EINVAL;
+ switch (uaccess->access) {
+ case KDBUS_POLICY_SEE:
+ case KDBUS_POLICY_TALK:
+ case KDBUS_POLICY_OWN:
+ a->access = uaccess->access;
+ break;
+ default:
+ goto err;
+ }
+
+ switch (uaccess->type) {
+ case KDBUS_POLICY_ACCESS_USER:
+ a->uid = make_kuid(current_user_ns(), uaccess->id);
+ if (!uid_valid(a->uid))
+ goto err;
+
+ break;
+ case KDBUS_POLICY_ACCESS_GROUP:
+ a->gid = make_kgid(current_user_ns(), uaccess->id);
+ if (!gid_valid(a->gid))
+ goto err;
+
+ break;
+ case KDBUS_POLICY_ACCESS_WORLD:
+ break;
+ default:
+ goto err;
+ }
+
+ a->type = uaccess->type;
+
+ return a;
+
+err:
+ kfree(a);
+ return ERR_PTR(ret);
+}
+
+/**
+ * kdbus_policy_set() - set a connection's policy rules
+ * @db: The policy database
+ * @items: A list of kdbus_item elements that contain both
+ * names and access rules to set.
+ * @items_size: The total size of the items.
+ * @max_policies: The maximum number of policy entries to allow.
+ * Pass 0 for no limit.
+ * @allow_wildcards: Boolean value whether wildcard entries (such
+ * ending on '.*') should be allowed.
+ * @owner: The owner of the new policy items.
+ *
+ * This function sets a new set of policies for a given owner. The names and
+ * access rules are gathered by walking the list of items passed in as
+ * argument. An item of type KDBUS_ITEM_NAME is expected before any number of
+ * KDBUS_ITEM_POLICY_ACCESS items. If there are more repetitions of this
+ * pattern than denoted in @max_policies, -EINVAL is returned.
+ *
+ * In order to allow atomic replacement of rules, the function first removes
+ * all entries that have been created for the given owner previously.
+ *
+ * Callers to this function must make sur that the owner is a custom
+ * endpoint, or if the endpoint is a default endpoint, then it must be
+ * either a policy holder or an activator.
+ *
+ * Return: 0 on success, negative errno on failure.
+ */
+int kdbus_policy_set(struct kdbus_policy_db *db,
+ const struct kdbus_item *items,
+ size_t items_size,
+ size_t max_policies,
+ bool allow_wildcards,
+ const void *owner)
+{
+ struct kdbus_policy_db_entry_access *a;
+ struct kdbus_policy_db_entry *e, *p;
+ const struct kdbus_item *item;
+ struct hlist_node *tmp;
+ HLIST_HEAD(entries);
+ HLIST_HEAD(restore);
+ size_t count = 0;
+ int i, ret = 0;
+ u32 hash;
+
+ if (items_size > KDBUS_POLICY_MAX_SIZE)
+ return -E2BIG;
+
+ /* Walk the list of items and look for new policies */
+ e = NULL;
+ KDBUS_ITEMS_FOREACH(item, items, items_size) {
+ switch (item->type) {
+ case KDBUS_ITEM_NAME: {
+ size_t len;
+
+ if (max_policies && ++count > max_policies) {
+ ret = -E2BIG;
+ goto exit;
+ }
+
+ if (!kdbus_name_is_valid(item->str, true)) {
+ ret = -EINVAL;
+ goto exit;
+ }
+
+ e = kzalloc(sizeof(*e), GFP_KERNEL);
+ if (!e) {
+ ret = -ENOMEM;
+ goto exit;
+ }
+
+ INIT_LIST_HEAD(&e->access_list);
+ e->owner = owner;
+ hlist_add_head(&e->hentry, &entries);
+
+ e->name = kstrdup(item->str, GFP_KERNEL);
+ if (!e->name) {
+ ret = -ENOMEM;
+ goto exit;
+ }
+
+ /*
+ * If a supplied name ends with an '.*', cut off that
+ * part, only store anything before it, and mark the
+ * entry as wildcard.
+ */
+ len = strlen(e->name);
+ if (len > 2 &&
+ e->name[len - 3] == '.' &&
+ e->name[len - 2] == '*') {
+ if (!allow_wildcards) {
+ ret = -EINVAL;
+ goto exit;
+ }
+
+ e->name[len - 3] = '\0';
+ e->wildcard = true;
+ }
+
+ break;
+ }
+
+ case KDBUS_ITEM_POLICY_ACCESS:
+ if (!e) {
+ ret = -EINVAL;
+ goto exit;
+ }
+
+ a = kdbus_policy_make_access(&item->policy_access);
+ if (IS_ERR(a)) {
+ ret = PTR_ERR(a);
+ goto exit;
+ }
+
+ list_add_tail(&a->list, &e->access_list);
+ break;
+ }
+ }
+
+ down_write(&db->entries_rwlock);
+
+ /* remember previous entries to restore in case of failure */
+ hash_for_each_safe(db->entries_hash, i, tmp, e, hentry)
+ if (e->owner == owner) {
+ hash_del(&e->hentry);
+ hlist_add_head(&e->hentry, &restore);
+ }
+
+ hlist_for_each_entry_safe(e, tmp, &entries, hentry) {
+ /* prevent duplicates */
+ hash = kdbus_strhash(e->name);
+ hash_for_each_possible(db->entries_hash, p, hentry, hash)
+ if (strcmp(e->name, p->name) == 0 &&
+ e->wildcard == p->wildcard) {
+ ret = -EEXIST;
+ goto restore;
+ }
+
+ hlist_del(&e->hentry);
+ hash_add(db->entries_hash, &e->hentry, hash);
+ }
+
+restore:
+ /* if we failed, flush all entries we added so far */
+ if (ret < 0)
+ __kdbus_policy_remove_owner(db, owner);
+
+ /* if we failed, restore entries, otherwise release them */
+ hlist_for_each_entry_safe(e, tmp, &restore, hentry) {
+ hlist_del(&e->hentry);
+ if (ret < 0) {
+ hash = kdbus_strhash(e->name);
+ hash_add(db->entries_hash, &e->hentry, hash);
+ } else {
+ kdbus_policy_entry_free(e);
+ }
+ }
+
+ up_write(&db->entries_rwlock);
+
+exit:
+ hlist_for_each_entry_safe(e, tmp, &entries, hentry) {
+ hlist_del(&e->hentry);
+ kdbus_policy_entry_free(e);
+ }
+
+ return ret;
+}
diff --git a/ipc/kdbus/policy.h b/ipc/kdbus/policy.h
new file mode 100644
index 000000000000..c137dd996861
--- /dev/null
+++ b/ipc/kdbus/policy.h
@@ -0,0 +1,51 @@
+/*
+ * Copyright (C) 2013-2014 Kay Sievers
+ * Copyright (C) 2013-2014 Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+ * Copyright (C) 2013-2014 Daniel Mack <daniel@zonque.org>
+ * Copyright (C) 2013-2014 David Herrmann <dh.herrmann@gmail.com>
+ * Copyright (C) 2013-2014 Linux Foundation
+ *
+ * kdbus is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU Lesser General Public License as published by the
+ * Free Software Foundation; either version 2.1 of the License, or (at
+ * your option) any later version.
+ */
+
+#ifndef __KDBUS_POLICY_H
+#define __KDBUS_POLICY_H
+
+#include <linux/hashtable.h>
+#include <linux/rwsem.h>
+
+struct kdbus_conn;
+struct kdbus_item;
+
+/**
+ * struct kdbus_policy_db - policy database
+ * @entries_hash: Hashtable of entries
+ * @entries_lock: Mutex to protect the database's access entries
+ */
+struct kdbus_policy_db {
+ DECLARE_HASHTABLE(entries_hash, 6);
+ struct rw_semaphore entries_rwlock;
+};
+
+void kdbus_policy_db_init(struct kdbus_policy_db *db);
+void kdbus_policy_db_clear(struct kdbus_policy_db *db);
+
+int kdbus_policy_query_unlocked(struct kdbus_policy_db *db,
+ const struct cred *cred, const char *name,
+ unsigned int hash);
+int kdbus_policy_query(struct kdbus_policy_db *db, const struct cred *cred,
+ const char *name, unsigned int hash);
+
+void kdbus_policy_remove_owner(struct kdbus_policy_db *db,
+ const void *owner);
+int kdbus_policy_set(struct kdbus_policy_db *db,
+ const struct kdbus_item *items,
+ size_t items_size,
+ size_t max_policies,
+ bool allow_wildcards,
+ const void *owner);
+
+#endif
--
2.2.1


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