From d7ccdaa17aab12a49f5e9e327b55167c4af26bf8 Mon Sep 17 00:00:00 2001 From: David Howells Date: Fri, 30 Aug 2013 15:37:54 +0100 Subject: [PATCH 1/2] KEYS: Implement a big key type that can save to tmpfs Implement a big key type that can save its contents to tmpfs and thus swapspace when memory is tight. This is useful for Kerberos ticket caches. Signed-off-by: David Howells Tested-by: Simo Sorce --- include/keys/big_key-type.h | 25 ++++++ include/linux/key.h | 1 + security/keys/Kconfig | 11 +++ security/keys/Makefile | 1 + security/keys/big_key.c | 204 ++++++++++++++++++++++++++++++++++++++++++++ 5 files changed, 242 insertions(+) create mode 100644 include/keys/big_key-type.h create mode 100644 security/keys/big_key.c diff --git a/include/keys/big_key-type.h b/include/keys/big_key-type.h new file mode 100644 index 0000000..d69bc8a --- /dev/null +++ b/include/keys/big_key-type.h @@ -0,0 +1,25 @@ +/* Big capacity key type. + * + * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version + * 2 of the License, or (at your option) any later version. + */ + +#ifndef _KEYS_BIG_KEY_TYPE_H +#define _KEYS_BIG_KEY_TYPE_H + +#include + +extern struct key_type key_type_big_key; + +extern int big_key_instantiate(struct key *key, struct key_preparsed_payload *prep); +extern void big_key_revoke(struct key *key); +extern void big_key_destroy(struct key *key); +extern void big_key_describe(const struct key *big_key, struct seq_file *m); +extern long big_key_read(const struct key *key, char __user *buffer, size_t buflen); + +#endif /* _KEYS_BIG_KEY_TYPE_H */ diff --git a/include/linux/key.h b/include/linux/key.h index 2417f78..010dbb6 100644 --- a/include/linux/key.h +++ b/include/linux/key.h @@ -201,6 +201,7 @@ struct key { unsigned long value; void __rcu *rcudata; void *data; + void *data2[2]; } payload; struct assoc_array keys; }; diff --git a/security/keys/Kconfig b/security/keys/Kconfig index 15e0dfe..b563622 100644 --- a/security/keys/Kconfig +++ b/security/keys/Kconfig @@ -20,6 +20,17 @@ config KEYS If you are unsure as to whether this is required, answer N. +config BIG_KEYS + tristate "Large payload keys" + depends on KEYS + depends on TMPFS + help + This option provides support for holding large keys within the kernel + (for example Kerberos ticket caches). The data may be stored out to + swapspace by tmpfs. + + If you are unsure as to whether this is required, answer N. + config TRUSTED_KEYS tristate "TRUSTED KEYS" depends on KEYS && TCG_TPM diff --git a/security/keys/Makefile b/security/keys/Makefile index 504aaa0..c487c77 100644 --- a/security/keys/Makefile +++ b/security/keys/Makefile @@ -22,5 +22,6 @@ obj-$(CONFIG_SYSCTL) += sysctl.o # # Key types # +obj-$(CONFIG_BIG_KEYS) += big_key.o obj-$(CONFIG_TRUSTED_KEYS) += trusted.o obj-$(CONFIG_ENCRYPTED_KEYS) += encrypted-keys/ diff --git a/security/keys/big_key.c b/security/keys/big_key.c new file mode 100644 index 0000000..5f9defc --- /dev/null +++ b/security/keys/big_key.c @@ -0,0 +1,204 @@ +/* Large capacity key type + * + * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public Licence + * as published by the Free Software Foundation; either version + * 2 of the Licence, or (at your option) any later version. + */ + +#include +#include +#include +#include +#include +#include +#include +#include + +MODULE_LICENSE("GPL"); + +/* + * If the data is under this limit, there's no point creating a shm file to + * hold it as the permanently resident metadata for the shmem fs will be at + * least as large as the data. + */ +#define BIG_KEY_FILE_THRESHOLD (sizeof(struct inode) + sizeof(struct dentry)) + +/* + * big_key defined keys take an arbitrary string as the description and an + * arbitrary blob of data as the payload + */ +struct key_type key_type_big_key = { + .name = "big_key", + .def_lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT, + .instantiate = big_key_instantiate, + .match = user_match, + .revoke = big_key_revoke, + .destroy = big_key_destroy, + .describe = big_key_describe, + .read = big_key_read, +}; + +/* + * Instantiate a big key + */ +int big_key_instantiate(struct key *key, struct key_preparsed_payload *prep) +{ + struct path *path = (struct path *)&key->payload.data2; + struct file *file; + ssize_t written; + size_t datalen = prep->datalen; + int ret; + + ret = -EINVAL; + if (datalen <= 0 || datalen > 1024 * 1024 || !prep->data) + goto error; + + /* Set an arbitrary quota */ + ret = key_payload_reserve(key, 16); + if (ret < 0) + goto error; + + key->type_data.x[1] = datalen; + + if (datalen > BIG_KEY_FILE_THRESHOLD) { + /* Create a shmem file to store the data in. This will permit the data + * to be swapped out if needed. + * + * TODO: Encrypt the stored data with a temporary key. + */ + file = shmem_file_setup("", datalen, 0); + if (IS_ERR(file)) + goto err_quota; + + written = kernel_write(file, prep->data, prep->datalen, 0); + if (written != datalen) { + if (written >= 0) + ret = -ENOMEM; + goto err_fput; + } + + /* Pin the mount and dentry to the key so that we can open it again + * later + */ + *path = file->f_path; + path_get(path); + fput(file); + } else { + /* Just store the data in a buffer */ + void *data = kmalloc(datalen, GFP_KERNEL); + if (!data) { + ret = -ENOMEM; + goto err_quota; + } + + key->payload.data = memcpy(data, prep->data, prep->datalen); + } + return 0; + +err_fput: + fput(file); +err_quota: + key_payload_reserve(key, 0); +error: + return ret; +} + +/* + * dispose of the links from a revoked keyring + * - called with the key sem write-locked + */ +void big_key_revoke(struct key *key) +{ + struct path *path = (struct path *)&key->payload.data2; + + /* clear the quota */ + key_payload_reserve(key, 0); + if (key_is_instantiated(key) && key->type_data.x[1] > BIG_KEY_FILE_THRESHOLD) + vfs_truncate(path, 0); +} + +/* + * dispose of the data dangling from the corpse of a big_key key + */ +void big_key_destroy(struct key *key) +{ + if (key->type_data.x[1] > BIG_KEY_FILE_THRESHOLD) { + struct path *path = (struct path *)&key->payload.data2; + path_put(path); + path->mnt = NULL; + path->dentry = NULL; + } else { + kfree(key->payload.data); + key->payload.data = NULL; + } +} + +/* + * describe the big_key key + */ +void big_key_describe(const struct key *key, struct seq_file *m) +{ + unsigned long datalen = key->type_data.x[1]; + + seq_puts(m, key->description); + + if (key_is_instantiated(key)) + seq_printf(m, ": %lu [%s]", + datalen, + datalen > BIG_KEY_FILE_THRESHOLD ? "file" : "buff"); +} + +/* + * read the key data + * - the key's semaphore is read-locked + */ +long big_key_read(const struct key *key, char __user *buffer, size_t buflen) +{ + unsigned long datalen = key->type_data.x[1]; + long ret; + + if (!buffer || buflen < datalen) + return datalen; + + if (datalen > BIG_KEY_FILE_THRESHOLD) { + struct path *path = (struct path *)&key->payload.data2; + struct file *file; + loff_t pos; + + file = dentry_open(path, O_RDONLY, current_cred()); + if (IS_ERR(file)) + return PTR_ERR(file); + + pos = 0; + ret = vfs_read(file, buffer, datalen, &pos); + fput(file); + if (ret >= 0 && ret != datalen) + ret = -EIO; + } else { + ret = datalen; + if (copy_to_user(buffer, key->payload.data, datalen) != 0) + ret = -EFAULT; + } + + return ret; +} + +/* + * Module stuff + */ +static int __init big_key_init(void) +{ + return register_key_type(&key_type_big_key); +} + +static void __exit big_key_cleanup(void) +{ + unregister_key_type(&key_type_big_key); +} + +module_init(big_key_init); +module_exit(big_key_cleanup); -- 1.8.3.1 From 862e98313b10123fa4352117b0b0c0f5a530cefb Mon Sep 17 00:00:00 2001 From: David Howells Date: Fri, 30 Aug 2013 15:37:54 +0100 Subject: [PATCH 2/2] KEYS: Add per-user_namespace registers for persistent per-UID kerberos caches Add support for per-user_namespace registers of persistent per-UID kerberos caches held within the kernel. This allows the kerberos cache to be retained beyond the life of all a user's processes so that the user's cron jobs can work. The kerberos cache is envisioned as a keyring/key tree looking something like: struct user_namespace \___ .krb_cache keyring - The register \___ _krb.0 keyring - Root's Kerberos cache \___ _krb.5000 keyring - User 5000's Kerberos cache \___ _krb.5001 keyring - User 5001's Kerberos cache \___ tkt785 big_key - A ccache blob \___ tkt12345 big_key - Another ccache blob Or possibly: struct user_namespace \___ .krb_cache keyring - The register \___ _krb.0 keyring - Root's Kerberos cache \___ _krb.5000 keyring - User 5000's Kerberos cache \___ _krb.5001 keyring - User 5001's Kerberos cache \___ tkt785 keyring - A ccache \___ krbtgt/REDHAT.COM@REDHAT.COM big_key \___ http/REDHAT.COM@REDHAT.COM user \___ afs/REDHAT.COM@REDHAT.COM user \___ nfs/REDHAT.COM@REDHAT.COM user \___ krbtgt/KERNEL.ORG@KERNEL.ORG big_key \___ http/KERNEL.ORG@KERNEL.ORG big_key What goes into a particular Kerberos cache is entirely up to userspace. Kernel support is limited to giving you the Kerberos cache keyring that you want. The user asks for their Kerberos cache by: krb_cache = keyctl_get_krbcache(uid, dest_keyring); The uid is -1 or the user's own UID for the user's own cache or the uid of some other user's cache (requires CAP_SETUID). This permits rpc.gssd or whatever to mess with the cache. The cache returned is a keyring named "_krb." that the possessor can read, search, clear, invalidate, unlink from and add links to. Active LSMs get a chance to rule on whether the caller is permitted to make a link. Each uid's cache keyring is created when it first accessed and is given a timeout that is extended each time this function is called so that the keyring goes away after a while. The timeout is configurable by sysctl but defaults to three days. Each user_namespace struct gets a lazily-created keyring that serves as the register. The cache keyrings are added to it. This means that standard key search and garbage collection facilities are available. The user_namespace struct's register goes away when it does and anything left in it is then automatically gc'd. Signed-off-by: David Howells Tested-by: Simo Sorce cc: Serge E. Hallyn cc: Eric W. Biederman --- include/linux/user_namespace.h | 7 ++ include/uapi/linux/keyctl.h | 1 + kernel/user.c | 4 + kernel/user_namespace.c | 6 ++ security/keys/Kconfig | 17 +++++ security/keys/Makefile | 1 + security/keys/compat.c | 3 + security/keys/internal.h | 9 +++ security/keys/keyctl.c | 3 + security/keys/persistent.c | 169 +++++++++++++++++++++++++++++++++++++++++ security/keys/sysctl.c | 11 +++ 11 files changed, 231 insertions(+) create mode 100644 security/keys/persistent.c diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h index 4db2985..bb0639d 100644 --- a/include/linux/user_namespace.h +++ b/include/linux/user_namespace.h @@ -27,6 +27,13 @@ struct user_namespace { kuid_t owner; kgid_t group; unsigned int proc_inum; + + /* Register of per-UID persistent keyrings for this namespace */ +#ifdef CONFIG_PERSISTENT_KEYRINGS + struct key *persistent_keyring_register; + struct rw_semaphore persistent_keyring_register_sem; +#endif + }; extern struct user_namespace init_user_ns; diff --git a/include/uapi/linux/keyctl.h b/include/uapi/linux/keyctl.h index c9b7f4fa..840cb99 100644 --- a/include/uapi/linux/keyctl.h +++ b/include/uapi/linux/keyctl.h @@ -56,5 +56,6 @@ #define KEYCTL_REJECT 19 /* reject a partially constructed key */ #define KEYCTL_INSTANTIATE_IOV 20 /* instantiate a partially constructed key */ #define KEYCTL_INVALIDATE 21 /* invalidate a key */ +#define KEYCTL_GET_PERSISTENT 22 /* get a user's persistent keyring */ #endif /* _LINUX_KEYCTL_H */ diff --git a/kernel/user.c b/kernel/user.c index 5bbb919..a3a0dbf 100644 --- a/kernel/user.c +++ b/kernel/user.c @@ -51,6 +51,10 @@ struct user_namespace init_user_ns = { .owner = GLOBAL_ROOT_UID, .group = GLOBAL_ROOT_GID, .proc_inum = PROC_USER_INIT_INO, +#ifdef CONFIG_KEYS_KERBEROS_CACHE + .krb_cache_register_sem = + __RWSEM_INITIALIZER(init_user_ns.krb_cache_register_sem), +#endif }; EXPORT_SYMBOL_GPL(init_user_ns); diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index 13fb113..2dbc299 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -101,6 +101,9 @@ int create_user_ns(struct cred *new) set_cred_user_ns(new, ns); +#ifdef CONFIG_PERSISTENT_KEYRINGS + init_rwsem(&ns->persistent_keyring_register_sem); +#endif return 0; } @@ -130,6 +133,9 @@ void free_user_ns(struct user_namespace *ns) do { parent = ns->parent; +#ifdef CONFIG_PERSISTENT_KEYRINGS + key_put(ns->persistent_keyring_register); +#endif proc_free_inum(ns->proc_inum); kmem_cache_free(user_ns_cachep, ns); ns = parent; diff --git a/security/keys/Kconfig b/security/keys/Kconfig index b563622..53d8748 100644 --- a/security/keys/Kconfig +++ b/security/keys/Kconfig @@ -20,6 +20,23 @@ config KEYS If you are unsure as to whether this is required, answer N. +config PERSISTENT_KEYRINGS + bool "Enable register of persistent per-UID keyrings" + depends on KEYS + help + This option provides a register of persistent per-UID keyrings, + primarily aimed at Kerberos key storage. The keyrings are persistent + in the sense that they stay around after all processes of that UID + have exited, not that they survive the machine being rebooted. + + A particular keyring may be accessed by either the user whose keyring + it is or by a process with administrative privileges. The active + LSMs gets to rule on which admin-level processes get to access the + cache. + + Keyrings are created and added into the register upon demand and get + removed if they expire (a default timeout is set upon creation). + config BIG_KEYS tristate "Large payload keys" depends on KEYS diff --git a/security/keys/Makefile b/security/keys/Makefile index c487c77..dfb3a7b 100644 --- a/security/keys/Makefile +++ b/security/keys/Makefile @@ -18,6 +18,7 @@ obj-y := \ obj-$(CONFIG_KEYS_COMPAT) += compat.o obj-$(CONFIG_PROC_FS) += proc.o obj-$(CONFIG_SYSCTL) += sysctl.o +obj-$(CONFIG_PERSISTENT_KEYRINGS) += persistent.o # # Key types diff --git a/security/keys/compat.c b/security/keys/compat.c index d65fa7f..bbd32c7 100644 --- a/security/keys/compat.c +++ b/security/keys/compat.c @@ -138,6 +138,9 @@ asmlinkage long compat_sys_keyctl(u32 option, case KEYCTL_INVALIDATE: return keyctl_invalidate_key(arg2); + case KEYCTL_GET_PERSISTENT: + return keyctl_get_persistent(arg2, arg3); + default: return -EOPNOTSUPP; } diff --git a/security/keys/internal.h b/security/keys/internal.h index 581c6f6..80b2aac 100644 --- a/security/keys/internal.h +++ b/security/keys/internal.h @@ -255,6 +255,15 @@ extern long keyctl_invalidate_key(key_serial_t); extern long keyctl_instantiate_key_common(key_serial_t, const struct iovec *, unsigned, size_t, key_serial_t); +#ifdef CONFIG_PERSISTENT_KEYRINGS +extern long keyctl_get_persistent(uid_t, key_serial_t); +extern unsigned persistent_keyring_expiry; +#else +static inline long keyctl_get_persistent(uid_t uid, key_serial_t destring) +{ + return -EOPNOTSUPP; +} +#endif /* * Debugging key validation diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c index 33cfd27..cee72ce 100644 --- a/security/keys/keyctl.c +++ b/security/keys/keyctl.c @@ -1667,6 +1667,9 @@ SYSCALL_DEFINE5(keyctl, int, option, unsigned long, arg2, unsigned long, arg3, case KEYCTL_INVALIDATE: return keyctl_invalidate_key((key_serial_t) arg2); + case KEYCTL_GET_PERSISTENT: + return keyctl_get_persistent((uid_t)arg2, (key_serial_t)arg3); + default: return -EOPNOTSUPP; } diff --git a/security/keys/persistent.c b/security/keys/persistent.c new file mode 100644 index 0000000..631a022 --- /dev/null +++ b/security/keys/persistent.c @@ -0,0 +1,169 @@ +/* General persistent per-UID keyrings register + * + * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public Licence + * as published by the Free Software Foundation; either version + * 2 of the Licence, or (at your option) any later version. + */ + +#include +#include "internal.h" + +unsigned persistent_keyring_expiry = 3 * 24 * 3600; /* Expire after 3 days of non-use */ + +/* + * Create the persistent keyring register for the current user namespace. + * + * Called with the namespace's sem locked for writing. + */ +static int key_create_persistent_register(struct user_namespace *ns) +{ + struct key *reg = keyring_alloc(".persistent_register", + KUIDT_INIT(0), KGIDT_INIT(0), + current_cred(), + ((KEY_POS_ALL & ~KEY_POS_SETATTR) | + KEY_USR_VIEW | KEY_USR_READ), + KEY_ALLOC_NOT_IN_QUOTA, NULL); + if (IS_ERR(reg)) + return PTR_ERR(reg); + + ns->persistent_keyring_register = reg; + return 0; +} + +/* + * Create the persistent keyring for the specified user. + * + * Called with the namespace's sem locked for writing. + */ +static key_ref_t key_create_persistent(struct user_namespace *ns, kuid_t uid, + struct keyring_index_key *index_key) +{ + struct key *persistent; + key_ref_t reg_ref, persistent_ref; + + if (!ns->persistent_keyring_register) { + long err = key_create_persistent_register(ns); + if (err < 0) + return ERR_PTR(err); + } else { + reg_ref = make_key_ref(ns->persistent_keyring_register, true); + persistent_ref = find_key_to_update(reg_ref, index_key); + if (persistent_ref) + return persistent_ref; + } + + persistent = keyring_alloc(index_key->description, + uid, INVALID_GID, current_cred(), + ((KEY_POS_ALL & ~KEY_POS_SETATTR) | + KEY_USR_VIEW | KEY_USR_READ), + KEY_ALLOC_NOT_IN_QUOTA, + ns->persistent_keyring_register); + if (IS_ERR(persistent)) + return ERR_CAST(persistent); + + return make_key_ref(persistent, true); +} + +/* + * Get the persistent keyring for a specific UID and link it to the nominated + * keyring. + */ +static long key_get_persistent(struct user_namespace *ns, kuid_t uid, + key_ref_t dest_ref) +{ + struct keyring_index_key index_key; + struct key *persistent; + key_ref_t reg_ref, persistent_ref; + char buf[32]; + long ret; + + /* Look in the register if it exists */ + index_key.type = &key_type_keyring; + index_key.description = buf; + index_key.desc_len = sprintf(buf, "_persistent.%u", from_kuid(ns, uid)); + + if (ns->persistent_keyring_register) { + reg_ref = make_key_ref(ns->persistent_keyring_register, true); + down_read(&ns->persistent_keyring_register_sem); + persistent_ref = find_key_to_update(reg_ref, &index_key); + up_read(&ns->persistent_keyring_register_sem); + + if (persistent_ref) + goto found; + } + + /* It wasn't in the register, so we'll need to create it. We might + * also need to create the register. + */ + down_write(&ns->persistent_keyring_register_sem); + persistent_ref = key_create_persistent(ns, uid, &index_key); + up_write(&ns->persistent_keyring_register_sem); + if (!IS_ERR(persistent_ref)) + goto found; + + return PTR_ERR(persistent_ref); + +found: + ret = key_task_permission(persistent_ref, current_cred(), KEY_LINK); + if (ret == 0) { + persistent = key_ref_to_ptr(persistent_ref); + ret = key_link(key_ref_to_ptr(dest_ref), persistent); + if (ret == 0) { + key_set_timeout(persistent, persistent_keyring_expiry); + ret = persistent->serial; + } + } + + key_ref_put(persistent_ref); + return ret; +} + +/* + * Get the persistent keyring for a specific UID and link it to the nominated + * keyring. + */ +long keyctl_get_persistent(uid_t _uid, key_serial_t destid) +{ + struct user_namespace *ns = current_user_ns(); + key_ref_t dest_ref; + kuid_t uid; + long ret; + + /* -1 indicates the current user */ + if (_uid == (uid_t)-1) { + uid = current_uid(); + } else { + uid = make_kuid(ns, _uid); + if (!uid_valid(uid)) + return -EINVAL; + + /* You can only see your own persistent cache if you're not + * sufficiently privileged. + */ + if (!uid_eq(uid, current_uid()) && + /* uid_eq(uid, current_suid()) && */ + !uid_eq(uid, current_euid()) && + /* uid_eq(uid, current_fsuid()) && */ + !ns_capable(ns, CAP_SETUID)) + return -EPERM; + } + + /* There must be a destination keyring */ + dest_ref = lookup_user_key(destid, KEY_LOOKUP_CREATE, KEY_WRITE); + if (IS_ERR(dest_ref)) + return PTR_ERR(dest_ref); + if (key_ref_to_ptr(dest_ref)->type != &key_type_keyring) { + ret = -ENOTDIR; + goto out_put_dest; + } + + ret = key_get_persistent(ns, uid, dest_ref); + +out_put_dest: + key_ref_put(dest_ref); + return ret; +} diff --git a/security/keys/sysctl.c b/security/keys/sysctl.c index ee32d18..8c0af08 100644 --- a/security/keys/sysctl.c +++ b/security/keys/sysctl.c @@ -61,5 +61,16 @@ ctl_table key_sysctls[] = { .extra1 = (void *) &zero, .extra2 = (void *) &max, }, +#ifdef CONFIG_PERSISTENT_KEYRINGS + { + .procname = "persistent_keyring_expiry", + .data = &persistent_keyring_expiry, + .maxlen = sizeof(unsigned), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = (void *) &zero, + .extra2 = (void *) &max, + }, +#endif { } }; -- 1.8.3.1