From f7e47677e39a03057dcced2016c92a9c868693ec Mon Sep 17 00:00:00 2001 From: David Howells Date: Tue, 14 Jan 2020 17:07:11 +0000 Subject: watch_queue: Add a key/keyring notification facility Add a key/keyring change notification facility whereby notifications about changes in key and keyring content and attributes can be received. Firstly, an event queue needs to be created: pipe2(fds, O_NOTIFICATION_PIPE); ioctl(fds[1], IOC_WATCH_QUEUE_SET_SIZE, 256); then a notification can be set up to report notifications via that queue: struct watch_notification_filter filter = { .nr_filters = 1, .filters = { [0] = { .type = WATCH_TYPE_KEY_NOTIFY, .subtype_filter[0] = UINT_MAX, }, }, }; ioctl(fds[1], IOC_WATCH_QUEUE_SET_FILTER, &filter); keyctl_watch_key(KEY_SPEC_SESSION_KEYRING, fds[1], 0x01); After that, records will be placed into the queue when events occur in which keys are changed in some way. Records are of the following format: struct key_notification { struct watch_notification watch; __u32 key_id; __u32 aux; } *n; Where: n->watch.type will be WATCH_TYPE_KEY_NOTIFY. n->watch.subtype will indicate the type of event, such as NOTIFY_KEY_REVOKED. n->watch.info & WATCH_INFO_LENGTH will indicate the length of the record. n->watch.info & WATCH_INFO_ID will be the second argument to keyctl_watch_key(), shifted. n->key will be the ID of the affected key. n->aux will hold subtype-dependent information, such as the key being linked into the keyring specified by n->key in the case of NOTIFY_KEY_LINKED. Note that it is permissible for event records to be of variable length - or, at least, the length may be dependent on the subtype. Note also that the queue can be shared between multiple notifications of various types. Signed-off-by: David Howells Reviewed-by: James Morris --- Documentation/security/keys/core.rst | 57 +++++++++++++++++++++ include/linux/key.h | 3 ++ include/uapi/linux/keyctl.h | 2 + include/uapi/linux/watch_queue.h | 28 +++++++++- security/keys/Kconfig | 9 ++++ security/keys/compat.c | 3 ++ security/keys/gc.c | 5 ++ security/keys/internal.h | 30 ++++++++++- security/keys/key.c | 38 +++++++++----- security/keys/keyctl.c | 99 ++++++++++++++++++++++++++++++++++-- security/keys/keyring.c | 20 +++++--- security/keys/request_key.c | 4 +- 12 files changed, 270 insertions(+), 28 deletions(-) diff --git a/Documentation/security/keys/core.rst b/Documentation/security/keys/core.rst index d9b0b859018b..6cff2b5f88ed 100644 --- a/Documentation/security/keys/core.rst +++ b/Documentation/security/keys/core.rst @@ -1026,6 +1026,63 @@ The keyctl syscall functions are: written into the output buffer. Verification returns 0 on success. + * Watch a key or keyring for changes:: + + long keyctl(KEYCTL_WATCH_KEY, key_serial_t key, int queue_fd, + const struct watch_notification_filter *filter); + + This will set or remove a watch for changes on the specified key or + keyring. + + "key" is the ID of the key to be watched. + + "queue_fd" is a file descriptor referring to an open "/dev/watch_queue" + which manages the buffer into which notifications will be delivered. + + "filter" is either NULL to remove a watch or a filter specification to + indicate what events are required from the key. + + See Documentation/watch_queue.rst for more information. + + Note that only one watch may be emplaced for any particular { key, + queue_fd } combination. + + Notification records look like:: + + struct key_notification { + struct watch_notification watch; + __u32 key_id; + __u32 aux; + }; + + In this, watch::type will be "WATCH_TYPE_KEY_NOTIFY" and subtype will be + one of:: + + NOTIFY_KEY_INSTANTIATED + NOTIFY_KEY_UPDATED + NOTIFY_KEY_LINKED + NOTIFY_KEY_UNLINKED + NOTIFY_KEY_CLEARED + NOTIFY_KEY_REVOKED + NOTIFY_KEY_INVALIDATED + NOTIFY_KEY_SETATTR + + Where these indicate a key being instantiated/rejected, updated, a link + being made in a keyring, a link being removed from a keyring, a keyring + being cleared, a key being revoked, a key being invalidated or a key + having one of its attributes changed (user, group, perm, timeout, + restriction). + + If a watched key is deleted, a basic watch_notification will be issued + with "type" set to WATCH_TYPE_META and "subtype" set to + watch_meta_removal_notification. The watchpoint ID will be set in the + "info" field. + + This needs to be configured by enabling: + + "Provide key/keyring change notifications" (KEY_NOTIFICATIONS) + + Kernel Services =============== diff --git a/include/linux/key.h b/include/linux/key.h index 6cf8e71cf8b7..b99b40db08fc 100644 --- a/include/linux/key.h +++ b/include/linux/key.h @@ -176,6 +176,9 @@ struct key { struct list_head graveyard_link; struct rb_node serial_node; }; +#ifdef CONFIG_KEY_NOTIFICATIONS + struct watch_list *watchers; /* Entities watching this key for changes */ +#endif struct rw_semaphore sem; /* change vs change sem */ struct key_user *user; /* owner of this key */ void *security; /* security data for this key */ diff --git a/include/uapi/linux/keyctl.h b/include/uapi/linux/keyctl.h index ed3d5893830d..4c8884eea808 100644 --- a/include/uapi/linux/keyctl.h +++ b/include/uapi/linux/keyctl.h @@ -69,6 +69,7 @@ #define KEYCTL_RESTRICT_KEYRING 29 /* Restrict keys allowed to link to a keyring */ #define KEYCTL_MOVE 30 /* Move keys between keyrings */ #define KEYCTL_CAPABILITIES 31 /* Find capabilities of keyrings subsystem */ +#define KEYCTL_WATCH_KEY 32 /* Watch a key or ring of keys for changes */ /* keyctl structures */ struct keyctl_dh_params { @@ -130,5 +131,6 @@ struct keyctl_pkey_params { #define KEYCTL_CAPS0_MOVE 0x80 /* KEYCTL_MOVE supported */ #define KEYCTL_CAPS1_NS_KEYRING_NAME 0x01 /* Keyring names are per-user_namespace */ #define KEYCTL_CAPS1_NS_KEY_TAG 0x02 /* Key indexing can include a namespace tag */ +#define KEYCTL_CAPS1_NOTIFICATIONS 0x04 /* Keys generate watchable notifications */ #endif /* _LINUX_KEYCTL_H */ diff --git a/include/uapi/linux/watch_queue.h b/include/uapi/linux/watch_queue.h index 3a5790f1f05d..c3d8320b5d3a 100644 --- a/include/uapi/linux/watch_queue.h +++ b/include/uapi/linux/watch_queue.h @@ -13,7 +13,8 @@ enum watch_notification_type { WATCH_TYPE_META = 0, /* Special record */ - WATCH_TYPE__NR = 1 + WATCH_TYPE_KEY_NOTIFY = 1, /* Key change event notification */ + WATCH_TYPE__NR = 2 }; enum watch_meta_notification_subtype { @@ -75,4 +76,29 @@ struct watch_notification_removal { __u64 id; /* Type-dependent identifier */ }; +/* + * Type of key/keyring change notification. + */ +enum key_notification_subtype { + NOTIFY_KEY_INSTANTIATED = 0, /* Key was instantiated (aux is error code) */ + NOTIFY_KEY_UPDATED = 1, /* Key was updated */ + NOTIFY_KEY_LINKED = 2, /* Key (aux) was added to watched keyring */ + NOTIFY_KEY_UNLINKED = 3, /* Key (aux) was removed from watched keyring */ + NOTIFY_KEY_CLEARED = 4, /* Keyring was cleared */ + NOTIFY_KEY_REVOKED = 5, /* Key was revoked */ + NOTIFY_KEY_INVALIDATED = 6, /* Key was invalidated */ + NOTIFY_KEY_SETATTR = 7, /* Key's attributes got changed */ +}; + +/* + * Key/keyring notification record. + * - watch.type = WATCH_TYPE_KEY_NOTIFY + * - watch.subtype = enum key_notification_type + */ +struct key_notification { + struct watch_notification watch; + __u32 key_id; /* The key/keyring affected */ + __u32 aux; /* Per-type auxiliary data */ +}; + #endif /* _UAPI_LINUX_WATCH_QUEUE_H */ diff --git a/security/keys/Kconfig b/security/keys/Kconfig index 47c041563d41..d4dc5ea208af 100644 --- a/security/keys/Kconfig +++ b/security/keys/Kconfig @@ -116,3 +116,12 @@ config KEY_DH_OPERATIONS in the kernel. If you are unsure as to whether this is required, answer N. + +config KEY_NOTIFICATIONS + bool "Provide key/keyring change notifications" + depends on KEYS && WATCH_QUEUE + help + This option provides support for getting change notifications on keys + and keyrings on which the caller has View permission. This makes use + of the /dev/watch_queue misc device to handle the notification + buffer and provides KEYCTL_WATCH_KEY to enable/disable watches. diff --git a/security/keys/compat.c b/security/keys/compat.c index b975f8f11124..6ee9d8f6a4a5 100644 --- a/security/keys/compat.c +++ b/security/keys/compat.c @@ -156,6 +156,9 @@ COMPAT_SYSCALL_DEFINE5(keyctl, u32, option, case KEYCTL_CAPABILITIES: return keyctl_capabilities(compat_ptr(arg2), arg3); + case KEYCTL_WATCH_KEY: + return keyctl_watch_key(arg2, arg3, arg4); + default: return -EOPNOTSUPP; } diff --git a/security/keys/gc.c b/security/keys/gc.c index 671dd730ecfc..3c90807476eb 100644 --- a/security/keys/gc.c +++ b/security/keys/gc.c @@ -131,6 +131,11 @@ static noinline void key_gc_unused_keys(struct list_head *keys) kdebug("- %u", key->serial); key_check(key); +#ifdef CONFIG_KEY_NOTIFICATIONS + remove_watch_list(key->watchers, key->serial); + key->watchers = NULL; +#endif + /* Throw away the key data if the key is instantiated */ if (state == KEY_IS_POSITIVE && key->type->destroy) key->type->destroy(key); diff --git a/security/keys/internal.h b/security/keys/internal.h index 6d0ca48ae9a5..28e17f4f3328 100644 --- a/security/keys/internal.h +++ b/security/keys/internal.h @@ -15,6 +15,7 @@ #include #include #include +#include #include #include #include @@ -99,7 +100,8 @@ extern int __key_link_begin(struct key *keyring, const struct keyring_index_key *index_key, struct assoc_array_edit **_edit); extern int __key_link_check_live_key(struct key *keyring, struct key *key); -extern void __key_link(struct key *key, struct assoc_array_edit **_edit); +extern void __key_link(struct key *keyring, struct key *key, + struct assoc_array_edit **_edit); extern void __key_link_end(struct key *keyring, const struct keyring_index_key *index_key, struct assoc_array_edit *edit); @@ -183,6 +185,23 @@ extern int key_task_permission(const key_ref_t key_ref, const struct cred *cred, key_perm_t perm); +static inline void notify_key(struct key *key, + enum key_notification_subtype subtype, u32 aux) +{ +#ifdef CONFIG_KEY_NOTIFICATIONS + struct key_notification n = { + .watch.type = WATCH_TYPE_KEY_NOTIFY, + .watch.subtype = subtype, + .watch.info = watch_sizeof(n), + .key_id = key_serial(key), + .aux = aux, + }; + + post_watch_notification(key->watchers, &n.watch, current_cred(), + n.key_id); +#endif +} + /* * Check to see whether permission is granted to use a key in the desired way. */ @@ -333,6 +352,15 @@ static inline long keyctl_pkey_e_d_s(int op, extern long keyctl_capabilities(unsigned char __user *_buffer, size_t buflen); +#ifdef CONFIG_KEY_NOTIFICATIONS +extern long keyctl_watch_key(key_serial_t, int, int); +#else +static inline long keyctl_watch_key(key_serial_t key_id, int watch_fd, int watch_id) +{ + return -EOPNOTSUPP; +} +#endif + /* * Debugging key validation */ diff --git a/security/keys/key.c b/security/keys/key.c index e959b3c96b48..e282c6179b21 100644 --- a/security/keys/key.c +++ b/security/keys/key.c @@ -444,6 +444,7 @@ static int __key_instantiate_and_link(struct key *key, /* mark the key as being instantiated */ atomic_inc(&key->user->nikeys); mark_key_instantiated(key, 0); + notify_key(key, NOTIFY_KEY_INSTANTIATED, 0); if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags)) awaken = 1; @@ -453,7 +454,7 @@ static int __key_instantiate_and_link(struct key *key, if (test_bit(KEY_FLAG_KEEP, &keyring->flags)) set_bit(KEY_FLAG_KEEP, &key->flags); - __key_link(key, _edit); + __key_link(keyring, key, _edit); } /* disable the authorisation key */ @@ -601,6 +602,7 @@ int key_reject_and_link(struct key *key, /* mark the key as being negatively instantiated */ atomic_inc(&key->user->nikeys); mark_key_instantiated(key, -error); + notify_key(key, NOTIFY_KEY_INSTANTIATED, -error); key->expiry = ktime_get_real_seconds() + timeout; key_schedule_gc(key->expiry + key_gc_delay); @@ -611,7 +613,7 @@ int key_reject_and_link(struct key *key, /* and link it into the destination keyring */ if (keyring && link_ret == 0) - __key_link(key, &edit); + __key_link(keyring, key, &edit); /* disable the authorisation key */ if (authkey) @@ -764,9 +766,11 @@ static inline key_ref_t __key_update(key_ref_t key_ref, down_write(&key->sem); ret = key->type->update(key, prep); - if (ret == 0) + if (ret == 0) { /* Updating a negative key positively instantiates it */ mark_key_instantiated(key, 0); + notify_key(key, NOTIFY_KEY_UPDATED, 0); + } up_write(&key->sem); @@ -1023,9 +1027,11 @@ int key_update(key_ref_t key_ref, const void *payload, size_t plen) down_write(&key->sem); ret = key->type->update(key, &prep); - if (ret == 0) + if (ret == 0) { /* Updating a negative key positively instantiates it */ mark_key_instantiated(key, 0); + notify_key(key, NOTIFY_KEY_UPDATED, 0); + } up_write(&key->sem); @@ -1057,15 +1063,17 @@ void key_revoke(struct key *key) * instantiated */ down_write_nested(&key->sem, 1); - if (!test_and_set_bit(KEY_FLAG_REVOKED, &key->flags) && - key->type->revoke) - key->type->revoke(key); - - /* set the death time to no more than the expiry time */ - time = ktime_get_real_seconds(); - if (key->revoked_at == 0 || key->revoked_at > time) { - key->revoked_at = time; - key_schedule_gc(key->revoked_at + key_gc_delay); + if (!test_and_set_bit(KEY_FLAG_REVOKED, &key->flags)) { + notify_key(key, NOTIFY_KEY_REVOKED, 0); + if (key->type->revoke) + key->type->revoke(key); + + /* set the death time to no more than the expiry time */ + time = ktime_get_real_seconds(); + if (key->revoked_at == 0 || key->revoked_at > time) { + key->revoked_at = time; + key_schedule_gc(key->revoked_at + key_gc_delay); + } } up_write(&key->sem); @@ -1087,8 +1095,10 @@ void key_invalidate(struct key *key) if (!test_bit(KEY_FLAG_INVALIDATED, &key->flags)) { down_write_nested(&key->sem, 1); - if (!test_and_set_bit(KEY_FLAG_INVALIDATED, &key->flags)) + if (!test_and_set_bit(KEY_FLAG_INVALIDATED, &key->flags)) { + notify_key(key, NOTIFY_KEY_INVALIDATED, 0); key_schedule_gc_links(); + } up_write(&key->sem); } } diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c index 5e01192e222a..7d8de1c9a478 100644 --- a/security/keys/keyctl.c +++ b/security/keys/keyctl.c @@ -37,7 +37,9 @@ static const unsigned char keyrings_capabilities[2] = { KEYCTL_CAPS0_MOVE ), [1] = (KEYCTL_CAPS1_NS_KEYRING_NAME | - KEYCTL_CAPS1_NS_KEY_TAG), + KEYCTL_CAPS1_NS_KEY_TAG | + (IS_ENABLED(CONFIG_KEY_NOTIFICATIONS) ? KEYCTL_CAPS1_NOTIFICATIONS : 0) + ), }; static int key_get_type_from_user(char *type, @@ -1039,6 +1041,7 @@ long keyctl_chown_key(key_serial_t id, uid_t user, gid_t group) if (group != (gid_t) -1) key->gid = gid; + notify_key(key, NOTIFY_KEY_SETATTR, 0); ret = 0; error_put: @@ -1089,6 +1092,7 @@ long keyctl_setperm_key(key_serial_t id, key_perm_t perm) /* if we're not the sysadmin, we can only change a key that we own */ if (capable(CAP_SYS_ADMIN) || uid_eq(key->uid, current_fsuid())) { key->perm = perm; + notify_key(key, NOTIFY_KEY_SETATTR, 0); ret = 0; } @@ -1480,10 +1484,12 @@ long keyctl_set_timeout(key_serial_t id, unsigned timeout) okay: key = key_ref_to_ptr(key_ref); ret = 0; - if (test_bit(KEY_FLAG_KEEP, &key->flags)) + if (test_bit(KEY_FLAG_KEEP, &key->flags)) { ret = -EPERM; - else + } else { key_set_timeout(key, timeout); + notify_key(key, NOTIFY_KEY_SETATTR, 0); + } key_put(key); error: @@ -1757,6 +1763,90 @@ error: return ret; } +#ifdef CONFIG_KEY_NOTIFICATIONS +/* + * Watch for changes to a key. + * + * The caller must have View permission to watch a key or keyring. + */ +long keyctl_watch_key(key_serial_t id, int watch_queue_fd, int watch_id) +{ + struct watch_queue *wqueue; + struct watch_list *wlist = NULL; + struct watch *watch = NULL; + struct key *key; + key_ref_t key_ref; + long ret; + + if (watch_id < -1 || watch_id > 0xff) + return -EINVAL; + + key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE, KEY_NEED_VIEW); + if (IS_ERR(key_ref)) + return PTR_ERR(key_ref); + key = key_ref_to_ptr(key_ref); + + wqueue = get_watch_queue(watch_queue_fd); + if (IS_ERR(wqueue)) { + ret = PTR_ERR(wqueue); + goto err_key; + } + + if (watch_id >= 0) { + ret = -ENOMEM; + if (!key->watchers) { + wlist = kzalloc(sizeof(*wlist), GFP_KERNEL); + if (!wlist) + goto err_wqueue; + init_watch_list(wlist, NULL); + } + + watch = kzalloc(sizeof(*watch), GFP_KERNEL); + if (!watch) + goto err_wlist; + + init_watch(watch, wqueue); + watch->id = key->serial; + watch->info_id = (u32)watch_id << WATCH_INFO_ID__SHIFT; + + ret = security_watch_key(key); + if (ret < 0) + goto err_watch; + + down_write(&key->sem); + if (!key->watchers) { + key->watchers = wlist; + wlist = NULL; + } + + ret = add_watch_to_object(watch, key->watchers); + up_write(&key->sem); + + if (ret == 0) + watch = NULL; + } else { + ret = -EBADSLT; + if (key->watchers) { + down_write(&key->sem); + ret = remove_watch_from_object(key->watchers, + wqueue, key_serial(key), + false); + up_write(&key->sem); + } + } + +err_watch: + kfree(watch); +err_wlist: + kfree(wlist); +err_wqueue: + put_watch_queue(wqueue); +err_key: + key_put(key); + return ret; +} +#endif /* CONFIG_KEY_NOTIFICATIONS */ + /* * Get keyrings subsystem capabilities. */ @@ -1926,6 +2016,9 @@ SYSCALL_DEFINE5(keyctl, int, option, unsigned long, arg2, unsigned long, arg3, case KEYCTL_CAPABILITIES: return keyctl_capabilities((unsigned char __user *)arg2, (size_t)arg3); + case KEYCTL_WATCH_KEY: + return keyctl_watch_key((key_serial_t)arg2, (int)arg3, (int)arg4); + default: return -EOPNOTSUPP; } diff --git a/security/keys/keyring.c b/security/keys/keyring.c index 5ca620d31cd3..14abfe765b7e 100644 --- a/security/keys/keyring.c +++ b/security/keys/keyring.c @@ -1056,12 +1056,14 @@ int keyring_restrict(key_ref_t keyring_ref, const char *type, down_write(&keyring->sem); down_write(&keyring_serialise_restrict_sem); - if (keyring->restrict_link) + if (keyring->restrict_link) { ret = -EEXIST; - else if (keyring_detect_restriction_cycle(keyring, restrict_link)) + } else if (keyring_detect_restriction_cycle(keyring, restrict_link)) { ret = -EDEADLK; - else + } else { keyring->restrict_link = restrict_link; + notify_key(keyring, NOTIFY_KEY_SETATTR, 0); + } up_write(&keyring_serialise_restrict_sem); up_write(&keyring->sem); @@ -1362,12 +1364,14 @@ int __key_link_check_live_key(struct key *keyring, struct key *key) * holds at most one link to any given key of a particular type+description * combination. */ -void __key_link(struct key *key, struct assoc_array_edit **_edit) +void __key_link(struct key *keyring, struct key *key, + struct assoc_array_edit **_edit) { __key_get(key); assoc_array_insert_set_object(*_edit, keyring_key_to_ptr(key)); assoc_array_apply_edit(*_edit); *_edit = NULL; + notify_key(keyring, NOTIFY_KEY_LINKED, key_serial(key)); } /* @@ -1451,7 +1455,7 @@ int key_link(struct key *keyring, struct key *key) if (ret == 0) ret = __key_link_check_live_key(keyring, key); if (ret == 0) - __key_link(key, &edit); + __key_link(keyring, key, &edit); error_end: __key_link_end(keyring, &key->index_key, edit); @@ -1483,7 +1487,7 @@ static int __key_unlink_begin(struct key *keyring, struct key *key, struct assoc_array_edit *edit; BUG_ON(*_edit != NULL); - + edit = assoc_array_delete(&keyring->keys, &keyring_assoc_array_ops, &key->index_key); if (IS_ERR(edit)) @@ -1503,6 +1507,7 @@ static void __key_unlink(struct key *keyring, struct key *key, struct assoc_array_edit **_edit) { assoc_array_apply_edit(*_edit); + notify_key(keyring, NOTIFY_KEY_UNLINKED, key_serial(key)); *_edit = NULL; key_payload_reserve(keyring, keyring->datalen - KEYQUOTA_LINK_BYTES); } @@ -1621,7 +1626,7 @@ int key_move(struct key *key, goto error; __key_unlink(from_keyring, key, &from_edit); - __key_link(key, &to_edit); + __key_link(to_keyring, key, &to_edit); error: __key_link_end(to_keyring, &key->index_key, to_edit); __key_unlink_end(from_keyring, key, from_edit); @@ -1655,6 +1660,7 @@ int keyring_clear(struct key *keyring) } else { if (edit) assoc_array_apply_edit(edit); + notify_key(keyring, NOTIFY_KEY_CLEARED, 0); key_payload_reserve(keyring, 0); ret = 0; } diff --git a/security/keys/request_key.c b/security/keys/request_key.c index 957b9e3e1492..e1b9f1a80676 100644 --- a/security/keys/request_key.c +++ b/security/keys/request_key.c @@ -418,7 +418,7 @@ static int construct_alloc_key(struct keyring_search_context *ctx, goto key_already_present; if (dest_keyring) - __key_link(key, &edit); + __key_link(dest_keyring, key, &edit); mutex_unlock(&key_construction_mutex); if (dest_keyring) @@ -437,7 +437,7 @@ key_already_present: if (dest_keyring) { ret = __key_link_check_live_key(dest_keyring, key); if (ret == 0) - __key_link(key, &edit); + __key_link(dest_keyring, key, &edit); __key_link_end(dest_keyring, &ctx->index_key, edit); if (ret < 0) goto link_check_failed; -- cgit v1.2.3-70-g09d2