From: Daniel Mack <dan...@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 <dan...@zonque.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
drivers/misc/kdbus/policy.c | 617 ++++++++++++++++++++++++++++++++++++++++++++
drivers/misc/kdbus/policy.h | 60 +++++
2 files changed, 677 insertions(+)
create mode 100644 drivers/misc/kdbus/policy.c
create mode 100644 drivers/misc/kdbus/policy.h
diff --git a/drivers/misc/kdbus/policy.c b/drivers/misc/kdbus/policy.c
new file mode 100644
index 000000000000..66bce57eb5e6
--- /dev/null
+++ b/drivers/misc/kdbus/policy.c
@@ -0,0 +1,617 @@
+/*
+ * Copyright (C) 2013-2014 Kay Sievers
+ * Copyright (C) 2013-2014 Greg Kroah-Hartman <gre...@linuxfoundation.org>
+ * Copyright (C) 2013-2014 Daniel Mack <dan...@zonque.org>
+ * Copyright (C) 2013-2014 David Herrmann <dh.herrm...@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_cache_entry - a cached entry
+ * @conn_a: Connection A
+ * @conn_b: Connection B
+ * @owner: Owner of policy-entry that produced this cache-entry
+ * @hentry: The hash table entry for the database's entries_hash
+ */
+struct kdbus_policy_db_cache_entry {
+ struct kdbus_conn *conn_a;
+ struct kdbus_conn *conn_b;
+ const void *owner;
+ struct hlist_node hentry;
+};
+
+/**
+ * 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, bool wildcard)
+{
+ struct kdbus_policy_db_entry *e, *found = NULL;
+
+ hash_for_each_possible(db->entries_hash, e, hentry, hash)
+ if (strcmp(e->name, name) == 0 && !e->wildcard)
+ return e;
+
+ if (wildcard) {
+ const char *tmp;
+ char *dot;
+
+ tmp = kstrdup(name, GFP_KERNEL);
+ if (!tmp)
+ return NULL;
+
+ dot = strrchr(tmp, '.');
+ if (!dot)
+ goto exit_free;
+
+ *dot = '\0';
+ hash = kdbus_str_hash(tmp);
+
+ hash_for_each_possible(db->entries_hash, e, hentry, hash)
+ if (strcmp(e->name, tmp) == 0 && e->wildcard) {
+ found = e;
+ /* never "break;" in hash_for_each() */
+ goto exit_free;
+ }
+
+exit_free:
+ kfree(tmp);
+ }
+
+ return found;
+}
+
+/**
+ * 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_cache_entry *ce;
+ struct kdbus_policy_db_entry *e;
+ struct hlist_node *tmp;
+ unsigned int i;
+
+ BUG_ON(!db);
+
+ /* 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);
+
+ /* purge cache */
+ mutex_lock(&db->cache_lock);
+ hash_for_each_safe(db->talk_access_hash, i, tmp, ce, hentry) {
+ hash_del(&ce->hentry);
+ kfree(ce);
+ }
+ mutex_unlock(&db->cache_lock);
+}
+
+/**
+ * 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);
+ hash_init(db->talk_access_hash);
+ init_rwsem(&db->entries_rwlock);
+ mutex_init(&db->cache_lock);
+}
+
+static int kdbus_policy_check_access(const struct kdbus_policy_db_entry *e,
+ const struct cred *cred,
+ unsigned int access)
+{
+ struct kdbus_policy_db_entry_access *a;
+ struct group_info *group_info;
+ int i;
+
+ if (!e)
+ return -EPERM;
+
+ group_info = cred->group_info;
+
+ list_for_each_entry(a, &e->access_list, list) {
+ if (a->access >= access) {
+ switch (a->type) {
+ case KDBUS_POLICY_ACCESS_USER:
+ if (uid_eq(cred->uid, a->uid))
+ return 0;
+ break;
+ case KDBUS_POLICY_ACCESS_GROUP:
+ if (gid_eq(cred->gid, a->gid))
+ return 0;
+
+ for (i = 0; i < group_info->ngroups; i++) {
+ kgid_t gid = GROUP_AT(group_info, i);
+
+ if (gid_eq(gid, a->gid))
+ return 0;
+ }
+
+ break;
+ case KDBUS_POLICY_ACCESS_WORLD:
+ return 0;
+ }
+ }
+ }
+
+ return -EPERM;
+}
+
+/**
+ * kdbus_policy_check_own_access() - check whether a connection is allowed
+ * to own a name
+ * @db: The policy database
+ * @conn: The connection to check
+ * @name: The name to check
+ *
+ * Return: 0 if the connection is allowed to own the name, -EPERM otherwise
+ */
+int kdbus_policy_check_own_access(struct kdbus_policy_db *db,
+ const struct kdbus_conn *conn,
+ const char *name)
+{
+ const struct kdbus_policy_db_entry *e;
+ int ret;
+
+ down_read(&db->entries_rwlock);
+ e = kdbus_policy_lookup(db, name, kdbus_str_hash(name), true);
+ ret = kdbus_policy_check_access(e, conn->cred, KDBUS_POLICY_OWN);
+ up_read(&db->entries_rwlock);
+
+ return ret;
+}
+
+/**
+ * kdbus_policy_check_talk_access() - check if one connection is allowed
+ * to send a message to another connection
+ * @db: The policy database
+ * @conn_src: The source connection
+ * @conn_dst: The destination connection
+ *
+ * Return: 0 if access is granted, -EPERM if not, negative errno on failure
+ */
+int kdbus_policy_check_talk_access(struct kdbus_policy_db *db,
+ struct kdbus_conn *conn_src,
+ struct kdbus_conn *conn_dst)
+{
+ struct kdbus_policy_db_cache_entry *ce;
+ struct kdbus_name_entry *name_entry;
+ unsigned int hash = 0;
+ const void *owner;
+ int ret;
+
+ /*
+ * If there was a positive match for these two connections before,
+ * there's an entry in the hash table for them.
+ */
+ hash ^= hash_ptr(conn_src, KDBUS_POLICY_HASH_SIZE);
+ hash ^= hash_ptr(conn_dst, KDBUS_POLICY_HASH_SIZE);
+
+ mutex_lock(&db->cache_lock);
+ hash_for_each_possible(db->talk_access_hash, ce, hentry, hash)
+ if (ce->conn_a == conn_src && ce->conn_b == conn_dst) {
+ mutex_unlock(&db->cache_lock);
+ return 0;
+ }
+ mutex_unlock(&db->cache_lock);
+
+ /*
+ * Otherwise, walk the connection list and store a hash-table entry if
+ * send access is granted.
+ */
+
+ down_read(&db->entries_rwlock);
+
+ ret = -EPERM;
+ mutex_lock(&conn_dst->lock);
+ list_for_each_entry(name_entry, &conn_dst->names_list, conn_entry) {
+ u32 hash = kdbus_str_hash(name_entry->name);
+ const struct kdbus_policy_db_entry *e;
+
+ e = kdbus_policy_lookup(db, name_entry->name, hash, true);
+ if (kdbus_policy_check_access(e, conn_src->cred,
+ KDBUS_POLICY_TALK) == 0) {
+ owner = e->owner;
+ ret = 0;
+ break;
+ }
+ }
+ mutex_unlock(&conn_dst->lock);
+
+ if (ret >= 0) {
+ ret = -ENOMEM;
+ ce = kmalloc(sizeof(*ce), GFP_KERNEL);
+ if (ce) {
+ ce->conn_a = conn_src;
+ ce->conn_b = conn_dst;
+ ce->owner = owner;
+ INIT_HLIST_NODE(&ce->hentry);
+
+ mutex_lock(&db->cache_lock);
+ hash_add(db->talk_access_hash, &ce->hentry, hash);
+ mutex_unlock(&db->cache_lock);
+
+ ret = 0;
+ }
+ }
+
+ up_read(&db->entries_rwlock);
+
+ return ret;
+}
+
+/**
+ * kdbus_policy_check_see_access_unlocked() - Check whether a connection is
+ * allowed to see a given name
+ * @db: The policy database
+ * @conn: The connection performing the lookup
+ * @name: The name
+ *
+ * Return: 0 if permission to see the name is granted, -EPERM otherwise
+ */
+int kdbus_policy_check_see_access_unlocked(struct kdbus_policy_db *db,
+ struct kdbus_conn *conn,
+ const char *name)
+{
+ const struct kdbus_policy_db_entry *e;
+
+ e = kdbus_policy_lookup(db, name, kdbus_str_hash(name), true);
+ return kdbus_policy_check_access(e, conn->cred, KDBUS_POLICY_SEE);
+}
+
+static void __kdbus_policy_remove_owner_cache(struct kdbus_policy_db *db,
+ const void *owner)
+{
+ struct kdbus_policy_db_cache_entry *ce;
+ struct hlist_node *tmp;
+ int i;
+
+ mutex_lock(&db->cache_lock);
+ hash_for_each_safe(db->talk_access_hash, i, tmp, ce, hentry)
+ if (ce->owner == owner) {
+ hash_del(&ce->hentry);
+ kfree(ce);
+ }
+ mutex_unlock(&db->cache_lock);
+}
+
+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);
+ __kdbus_policy_remove_owner_cache(db, owner);
+ up_write(&db->entries_rwlock);
+}
+
+/**
+ * kdbus_policy_purge_cache_for_conn() - remove all cached entries related to
+ * a connection
+ * @db: The policy database
+ * @conn: The connection which items to remove
+ */
+void kdbus_policy_purge_cache(struct kdbus_policy_db *db,
+ const struct kdbus_conn *conn)
+{
+ struct kdbus_policy_db_cache_entry *ce;
+ struct hlist_node *tmp;
+ int i;
+
+ mutex_lock(&db->cache_lock);
+ hash_for_each_safe(db->talk_access_hash, i, tmp, ce, hentry)
+ if (ce->conn_a == conn || ce->conn_b == conn) {
+ hash_del(&ce->hentry);
+ kfree(ce);
+ }
+ mutex_unlock(&db->cache_lock);
+}
+
+/*
+ * Convert user provided policy access to internal kdbus policy
+ * access
+ */
+static int
+kdbus_policy_make_access(const struct kdbus_policy_access *uaccess,
+ struct kdbus_policy_db_entry_access **entry)
+{
+ int ret;
+ struct kdbus_policy_db_entry_access *a;
+
+ a = kzalloc(sizeof(*a), GFP_KERNEL);
+ if (!a)
+ return -ENOMEM;
+
+ ret = -EINVAL;
+ 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;
+ }
+
+ a->type = uaccess->type;
+ a->access = uaccess->access;
+
+ *entry = a;
+
+ return 0;
+
+err:
+ kfree(a);
+ return 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.
+ *
+ * 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;
+ }
+
+ ret = kdbus_policy_make_access(&item->policy_access,
+ &a);
+ if (ret < 0)
+ 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_str_hash(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);
+ }
+
+ /* purge all cache-entries produced by previous rules */
+ __kdbus_policy_remove_owner_cache(db, owner);
+
+restore:
+ /* if we failed, flush all entries we added so far, but keep cache */
+ 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_str_hash(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/drivers/misc/kdbus/policy.h b/drivers/misc/kdbus/policy.h
new file mode 100644
index 000000000000..f4f6f044b4c1
--- /dev/null
+++ b/drivers/misc/kdbus/policy.h
@@ -0,0 +1,60 @@
+/*
+ * Copyright (C) 2013-2014 Kay Sievers
+ * Copyright (C) 2013-2014 Greg Kroah-Hartman <gre...@linuxfoundation.org>
+ * Copyright (C) 2013-2014 Daniel Mack <dan...@zonque.org>
+ * Copyright (C) 2013-2014 David Herrmann <dh.herrm...@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/mutex.h>
+#include <linux/rwsem.h>
+
+struct kdbus_conn;
+struct kdbus_item;
+
+/**
+ * struct kdbus_policy_db - policy database
+ * @entries_hash: Hashtable of entries
+ * @talk_access_hash: Hashtable of send access elements
+ * @entries_lock: Mutex to protect the database's access entries
+ * @cache_lock: Mutex to protect the database's cache
+ */
+struct kdbus_policy_db {
+ DECLARE_HASHTABLE(entries_hash, 6);
+ DECLARE_HASHTABLE(talk_access_hash, 6);
+ struct rw_semaphore entries_rwlock;
+ struct mutex cache_lock;
+};
+
+void kdbus_policy_db_init(struct kdbus_policy_db *db);
+void kdbus_policy_db_clear(struct kdbus_policy_db *db);
+
+int kdbus_policy_check_see_access_unlocked(struct kdbus_policy_db *db,
+ struct kdbus_conn *conn,
+ const char *name);
+int kdbus_policy_check_talk_access(struct kdbus_policy_db *db,
+ struct kdbus_conn *conn_src,
+ struct kdbus_conn *conn_dst);
+int kdbus_policy_check_own_access(struct kdbus_policy_db *db,
+ const struct kdbus_conn *conn,
+ const char *name);
+void kdbus_policy_purge_cache(struct kdbus_policy_db *db,
+ const struct kdbus_conn *conn);
+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
--
2.1.2
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