From d720024e94de4e8b7f10ee83c532926f3ad5d708 Mon Sep 17 00:00:00 2001 From: Michael LeMay Date: Thu, 22 Jun 2006 14:47:17 -0700 Subject: [PATCH] [PATCH] selinux: add hooks for key subsystem Introduce SELinux hooks to support the access key retention subsystem within the kernel. Incorporate new flask headers from a modified version of the SELinux reference policy, with support for the new security class representing retained keys. Extend the "key_alloc" security hook with a task parameter representing the intended ownership context for the key being allocated. Attach security information to root's default keyrings within the SELinux initialization routine. Has passed David's testsuite. Signed-off-by: Michael LeMay Signed-off-by: David Howells Signed-off-by: James Morris Acked-by: Chris Wright Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/keys.txt | 29 +++++++++ include/linux/key.h | 18 ++++-- include/linux/security.h | 10 +-- kernel/user.c | 2 +- security/dummy.c | 2 +- security/keys/key.c | 8 +-- security/keys/keyring.c | 5 +- security/keys/process_keys.c | 15 ++--- security/keys/request_key.c | 6 +- security/keys/request_key_auth.c | 2 +- security/selinux/hooks.c | 64 ++++++++++++++++++++ security/selinux/include/av_perm_to_string.h | 6 ++ security/selinux/include/av_permissions.h | 8 +++ security/selinux/include/class_to_string.h | 1 + security/selinux/include/flask.h | 1 + security/selinux/include/objsec.h | 5 ++ 16 files changed, 155 insertions(+), 27 deletions(-) diff --git a/Documentation/keys.txt b/Documentation/keys.txt index aaa01b0e3ee..70302001270 100644 --- a/Documentation/keys.txt +++ b/Documentation/keys.txt @@ -19,6 +19,7 @@ This document has the following sections: - Key overview - Key service overview - Key access permissions + - SELinux support - New procfs files - Userspace system call interface - Kernel services @@ -232,6 +233,34 @@ For changing the ownership, group ID or permissions mask, being the owner of the key or having the sysadmin capability is sufficient. +=============== +SELINUX SUPPORT +=============== + +The security class "key" has been added to SELinux so that mandatory access +controls can be applied to keys created within various contexts. This support +is preliminary, and is likely to change quite significantly in the near future. +Currently, all of the basic permissions explained above are provided in SELinux +as well; SE Linux is simply invoked after all basic permission checks have been +performed. + +Each key is labeled with the same context as the task to which it belongs. +Typically, this is the same task that was running when the key was created. +The default keyrings are handled differently, but in a way that is very +intuitive: + + (*) The user and user session keyrings that are created when the user logs in + are currently labeled with the context of the login manager. + + (*) The keyrings associated with new threads are each labeled with the context + of their associated thread, and both session and process keyrings are + handled similarly. + +Note, however, that the default keyrings associated with the root user are +labeled with the default kernel context, since they are created early in the +boot process, before root has a chance to log in. + + ================ NEW PROCFS FILES ================ diff --git a/include/linux/key.h b/include/linux/key.h index cbf464ad958..8c275d12ef6 100644 --- a/include/linux/key.h +++ b/include/linux/key.h @@ -241,8 +241,9 @@ extern void unregister_key_type(struct key_type *ktype); extern struct key *key_alloc(struct key_type *type, const char *desc, - uid_t uid, gid_t gid, key_perm_t perm, - int not_in_quota); + uid_t uid, gid_t gid, + struct task_struct *ctx, + key_perm_t perm, int not_in_quota); extern int key_payload_reserve(struct key *key, size_t datalen); extern int key_instantiate_and_link(struct key *key, const void *data, @@ -292,7 +293,9 @@ extern int key_unlink(struct key *keyring, struct key *key); extern struct key *keyring_alloc(const char *description, uid_t uid, gid_t gid, - int not_in_quota, struct key *dest); + struct task_struct *ctx, + int not_in_quota, + struct key *dest); extern int keyring_clear(struct key *keyring); @@ -313,7 +316,8 @@ extern void keyring_replace_payload(struct key *key, void *replacement); * the userspace interface */ extern struct key root_user_keyring, root_session_keyring; -extern int alloc_uid_keyring(struct user_struct *user); +extern int alloc_uid_keyring(struct user_struct *user, + struct task_struct *ctx); extern void switch_uid_keyring(struct user_struct *new_user); extern int copy_keys(unsigned long clone_flags, struct task_struct *tsk); extern int copy_thread_group_keys(struct task_struct *tsk); @@ -342,7 +346,7 @@ extern void key_init(void); #define make_key_ref(k) ({ NULL; }) #define key_ref_to_ptr(k) ({ NULL; }) #define is_key_possessed(k) 0 -#define alloc_uid_keyring(u) 0 +#define alloc_uid_keyring(u,c) 0 #define switch_uid_keyring(u) do { } while(0) #define __install_session_keyring(t, k) ({ NULL; }) #define copy_keys(f,t) 0 @@ -355,6 +359,10 @@ extern void key_init(void); #define key_fsgid_changed(t) do { } while(0) #define key_init() do { } while(0) +/* Initial keyrings */ +extern struct key root_user_keyring; +extern struct key root_session_keyring; + #endif /* CONFIG_KEYS */ #endif /* __KERNEL__ */ #endif /* _LINUX_KEY_H */ diff --git a/include/linux/security.h b/include/linux/security.h index 4dfb1b84a9b..47722d35553 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -1313,7 +1313,7 @@ struct security_operations { /* key management security hooks */ #ifdef CONFIG_KEYS - int (*key_alloc)(struct key *key); + int (*key_alloc)(struct key *key, struct task_struct *tsk); void (*key_free)(struct key *key); int (*key_permission)(key_ref_t key_ref, struct task_struct *context, @@ -3008,9 +3008,10 @@ static inline int security_xfrm_policy_lookup(struct xfrm_policy *xp, u32 sk_sid #ifdef CONFIG_KEYS #ifdef CONFIG_SECURITY -static inline int security_key_alloc(struct key *key) +static inline int security_key_alloc(struct key *key, + struct task_struct *tsk) { - return security_ops->key_alloc(key); + return security_ops->key_alloc(key, tsk); } static inline void security_key_free(struct key *key) @@ -3027,7 +3028,8 @@ static inline int security_key_permission(key_ref_t key_ref, #else -static inline int security_key_alloc(struct key *key) +static inline int security_key_alloc(struct key *key, + struct task_struct *tsk) { return 0; } diff --git a/kernel/user.c b/kernel/user.c index 4b1eb745afa..6408c042429 100644 --- a/kernel/user.c +++ b/kernel/user.c @@ -148,7 +148,7 @@ struct user_struct * alloc_uid(uid_t uid) new->mq_bytes = 0; new->locked_shm = 0; - if (alloc_uid_keyring(new) < 0) { + if (alloc_uid_keyring(new, current) < 0) { kmem_cache_free(uid_cachep, new); return NULL; } diff --git a/security/dummy.c b/security/dummy.c index 64f6da0f422..6de4a4a5eb1 100644 --- a/security/dummy.c +++ b/security/dummy.c @@ -860,7 +860,7 @@ static int dummy_setprocattr(struct task_struct *p, char *name, void *value, siz } #ifdef CONFIG_KEYS -static inline int dummy_key_alloc(struct key *key) +static inline int dummy_key_alloc(struct key *key, struct task_struct *ctx) { return 0; } diff --git a/security/keys/key.c b/security/keys/key.c index 3fdc49c6a02..14a15abb773 100644 --- a/security/keys/key.c +++ b/security/keys/key.c @@ -247,8 +247,8 @@ static inline void key_alloc_serial(struct key *key) * instantiate the key or discard it before returning */ struct key *key_alloc(struct key_type *type, const char *desc, - uid_t uid, gid_t gid, key_perm_t perm, - int not_in_quota) + uid_t uid, gid_t gid, struct task_struct *ctx, + key_perm_t perm, int not_in_quota) { struct key_user *user = NULL; struct key *key; @@ -318,7 +318,7 @@ struct key *key_alloc(struct key_type *type, const char *desc, #endif /* let the security module know about the key */ - ret = security_key_alloc(key); + ret = security_key_alloc(key, ctx); if (ret < 0) goto security_error; @@ -822,7 +822,7 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref, /* allocate a new key */ key = key_alloc(ktype, description, current->fsuid, current->fsgid, - perm, not_in_quota); + current, perm, not_in_quota); if (IS_ERR(key)) { key_ref = ERR_PTR(PTR_ERR(key)); goto error_3; diff --git a/security/keys/keyring.c b/security/keys/keyring.c index bffa924c1f8..1357207fc9d 100644 --- a/security/keys/keyring.c +++ b/security/keys/keyring.c @@ -240,13 +240,14 @@ static long keyring_read(const struct key *keyring, * allocate a keyring and link into the destination keyring */ struct key *keyring_alloc(const char *description, uid_t uid, gid_t gid, - int not_in_quota, struct key *dest) + struct task_struct *ctx, int not_in_quota, + struct key *dest) { struct key *keyring; int ret; keyring = key_alloc(&key_type_keyring, description, - uid, gid, + uid, gid, ctx, (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_ALL, not_in_quota); diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c index 217a0bef3c8..a50a91332fe 100644 --- a/security/keys/process_keys.c +++ b/security/keys/process_keys.c @@ -67,7 +67,8 @@ struct key root_session_keyring = { /* * allocate the keyrings to be associated with a UID */ -int alloc_uid_keyring(struct user_struct *user) +int alloc_uid_keyring(struct user_struct *user, + struct task_struct *ctx) { struct key *uid_keyring, *session_keyring; char buf[20]; @@ -76,7 +77,7 @@ int alloc_uid_keyring(struct user_struct *user) /* concoct a default session keyring */ sprintf(buf, "_uid_ses.%u", user->uid); - session_keyring = keyring_alloc(buf, user->uid, (gid_t) -1, 0, NULL); + session_keyring = keyring_alloc(buf, user->uid, (gid_t) -1, ctx, 0, NULL); if (IS_ERR(session_keyring)) { ret = PTR_ERR(session_keyring); goto error; @@ -86,7 +87,7 @@ int alloc_uid_keyring(struct user_struct *user) * keyring */ sprintf(buf, "_uid.%u", user->uid); - uid_keyring = keyring_alloc(buf, user->uid, (gid_t) -1, 0, + uid_keyring = keyring_alloc(buf, user->uid, (gid_t) -1, ctx, 0, session_keyring); if (IS_ERR(uid_keyring)) { key_put(session_keyring); @@ -143,7 +144,7 @@ int install_thread_keyring(struct task_struct *tsk) sprintf(buf, "_tid.%u", tsk->pid); - keyring = keyring_alloc(buf, tsk->uid, tsk->gid, 1, NULL); + keyring = keyring_alloc(buf, tsk->uid, tsk->gid, tsk, 1, NULL); if (IS_ERR(keyring)) { ret = PTR_ERR(keyring); goto error; @@ -177,7 +178,7 @@ int install_process_keyring(struct task_struct *tsk) if (!tsk->signal->process_keyring) { sprintf(buf, "_pid.%u", tsk->tgid); - keyring = keyring_alloc(buf, tsk->uid, tsk->gid, 1, NULL); + keyring = keyring_alloc(buf, tsk->uid, tsk->gid, tsk, 1, NULL); if (IS_ERR(keyring)) { ret = PTR_ERR(keyring); goto error; @@ -217,7 +218,7 @@ static int install_session_keyring(struct task_struct *tsk, if (!keyring) { sprintf(buf, "_ses.%u", tsk->tgid); - keyring = keyring_alloc(buf, tsk->uid, tsk->gid, 1, NULL); + keyring = keyring_alloc(buf, tsk->uid, tsk->gid, tsk, 1, NULL); if (IS_ERR(keyring)) return PTR_ERR(keyring); } @@ -717,7 +718,7 @@ long join_session_keyring(const char *name) keyring = find_keyring_by_name(name, 0); if (PTR_ERR(keyring) == -ENOKEY) { /* not found - try and create a new one */ - keyring = keyring_alloc(name, tsk->uid, tsk->gid, 0, NULL); + keyring = keyring_alloc(name, tsk->uid, tsk->gid, tsk, 0, NULL); if (IS_ERR(keyring)) { ret = PTR_ERR(keyring); goto error2; diff --git a/security/keys/request_key.c b/security/keys/request_key.c index f030a0ccbb9..eab66a06ca5 100644 --- a/security/keys/request_key.c +++ b/security/keys/request_key.c @@ -48,7 +48,8 @@ static int call_sbin_request_key(struct key *key, /* allocate a new session keyring */ sprintf(desc, "_req.%u", key->serial); - keyring = keyring_alloc(desc, current->fsuid, current->fsgid, 1, NULL); + keyring = keyring_alloc(desc, current->fsuid, current->fsgid, + current, 1, NULL); if (IS_ERR(keyring)) { ret = PTR_ERR(keyring); goto error_alloc; @@ -137,7 +138,8 @@ static struct key *__request_key_construction(struct key_type *type, /* create a key and add it to the queue */ key = key_alloc(type, description, - current->fsuid, current->fsgid, KEY_POS_ALL, 0); + current->fsuid, current->fsgid, + current, KEY_POS_ALL, 0); if (IS_ERR(key)) goto alloc_failed; diff --git a/security/keys/request_key_auth.c b/security/keys/request_key_auth.c index cce6ba6b032..0ecc2e8d2bd 100644 --- a/security/keys/request_key_auth.c +++ b/security/keys/request_key_auth.c @@ -148,7 +148,7 @@ struct key *request_key_auth_new(struct key *target, const char *callout_info) sprintf(desc, "%x", target->serial); authkey = key_alloc(&key_type_request_key_auth, desc, - current->fsuid, current->fsgid, + current->fsuid, current->fsgid, current, KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH | KEY_USR_VIEW, 1); if (IS_ERR(authkey)) { diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 54adc9d31e9..524915dfda6 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -4252,6 +4252,57 @@ static int selinux_setprocattr(struct task_struct *p, return size; } +#ifdef CONFIG_KEYS + +static int selinux_key_alloc(struct key *k, struct task_struct *tsk) +{ + struct task_security_struct *tsec = tsk->security; + struct key_security_struct *ksec; + + ksec = kzalloc(sizeof(struct key_security_struct), GFP_KERNEL); + if (!ksec) + return -ENOMEM; + + ksec->obj = k; + ksec->sid = tsec->sid; + k->security = ksec; + + return 0; +} + +static void selinux_key_free(struct key *k) +{ + struct key_security_struct *ksec = k->security; + + k->security = NULL; + kfree(ksec); +} + +static int selinux_key_permission(key_ref_t key_ref, + struct task_struct *ctx, + key_perm_t perm) +{ + struct key *key; + struct task_security_struct *tsec; + struct key_security_struct *ksec; + + key = key_ref_to_ptr(key_ref); + + tsec = ctx->security; + ksec = key->security; + + /* if no specific permissions are requested, we skip the + permission check. No serious, additional covert channels + appear to be created. */ + if (perm == 0) + return 0; + + return avc_has_perm(tsec->sid, ksec->sid, + SECCLASS_KEY, perm, NULL); +} + +#endif + static struct security_operations selinux_ops = { .ptrace = selinux_ptrace, .capget = selinux_capget, @@ -4406,6 +4457,12 @@ static struct security_operations selinux_ops = { .xfrm_state_delete_security = selinux_xfrm_state_delete, .xfrm_policy_lookup = selinux_xfrm_policy_lookup, #endif + +#ifdef CONFIG_KEYS + .key_alloc = selinux_key_alloc, + .key_free = selinux_key_free, + .key_permission = selinux_key_permission, +#endif }; static __init int selinux_init(void) @@ -4441,6 +4498,13 @@ static __init int selinux_init(void) } else { printk(KERN_INFO "SELinux: Starting in permissive mode\n"); } + +#ifdef CONFIG_KEYS + /* Add security information to initial keyrings */ + security_key_alloc(&root_user_keyring, current); + security_key_alloc(&root_session_keyring, current); +#endif + return 0; } diff --git a/security/selinux/include/av_perm_to_string.h b/security/selinux/include/av_perm_to_string.h index 70ee65a5881..bc020bde6c8 100644 --- a/security/selinux/include/av_perm_to_string.h +++ b/security/selinux/include/av_perm_to_string.h @@ -242,3 +242,9 @@ S_(SECCLASS_PACKET, PACKET__SEND, "send") S_(SECCLASS_PACKET, PACKET__RECV, "recv") S_(SECCLASS_PACKET, PACKET__RELABELTO, "relabelto") + S_(SECCLASS_KEY, KEY__VIEW, "view") + S_(SECCLASS_KEY, KEY__READ, "read") + S_(SECCLASS_KEY, KEY__WRITE, "write") + S_(SECCLASS_KEY, KEY__SEARCH, "search") + S_(SECCLASS_KEY, KEY__LINK, "link") + S_(SECCLASS_KEY, KEY__SETATTR, "setattr") diff --git a/security/selinux/include/av_permissions.h b/security/selinux/include/av_permissions.h index 1d9cf3d306b..1205227a3a3 100644 --- a/security/selinux/include/av_permissions.h +++ b/security/selinux/include/av_permissions.h @@ -959,3 +959,11 @@ #define PACKET__SEND 0x00000001UL #define PACKET__RECV 0x00000002UL #define PACKET__RELABELTO 0x00000004UL + +#define KEY__VIEW 0x00000001UL +#define KEY__READ 0x00000002UL +#define KEY__WRITE 0x00000004UL +#define KEY__SEARCH 0x00000008UL +#define KEY__LINK 0x00000010UL +#define KEY__SETATTR 0x00000020UL + diff --git a/security/selinux/include/class_to_string.h b/security/selinux/include/class_to_string.h index 3aec75fee4f..24303b61309 100644 --- a/security/selinux/include/class_to_string.h +++ b/security/selinux/include/class_to_string.h @@ -60,3 +60,4 @@ S_("netlink_kobject_uevent_socket") S_("appletalk_socket") S_("packet") + S_("key") diff --git a/security/selinux/include/flask.h b/security/selinux/include/flask.h index a0eb9e281d1..95887aed2a6 100644 --- a/security/selinux/include/flask.h +++ b/security/selinux/include/flask.h @@ -62,6 +62,7 @@ #define SECCLASS_NETLINK_KOBJECT_UEVENT_SOCKET 55 #define SECCLASS_APPLETALK_SOCKET 56 #define SECCLASS_PACKET 57 +#define SECCLASS_KEY 58 /* * Security identifier indices for initial entities diff --git a/security/selinux/include/objsec.h b/security/selinux/include/objsec.h index 54c03077888..8f5547ad185 100644 --- a/security/selinux/include/objsec.h +++ b/security/selinux/include/objsec.h @@ -99,6 +99,11 @@ struct sk_security_struct { u32 peer_sid; /* SID of peer */ }; +struct key_security_struct { + struct key *obj; /* back pointer */ + u32 sid; /* SID of key */ +}; + extern unsigned int selinux_checkreqprot; #endif /* _SELINUX_OBJSEC_H_ */ -- 2.20.1