From 8bbf4976b59fc9fc2861e79cab7beb3f6d647640 Mon Sep 17 00:00:00 2001 From: David Howells Date: Fri, 14 Nov 2008 10:39:14 +1100 Subject: KEYS: Alter use of key instantiation link-to-keyring argument Alter the use of the key instantiation and negation functions' link-to-keyring arguments. Currently this specifies a keyring in the target process to link the key into, creating the keyring if it doesn't exist. This, however, can be a problem for copy-on-write credentials as it means that the instantiating process can alter the credentials of the requesting process. This patch alters the behaviour such that: (1) If keyctl_instantiate_key() or keyctl_negate_key() are given a specific keyring by ID (ringid >= 0), then that keyring will be used. (2) If keyctl_instantiate_key() or keyctl_negate_key() are given one of the special constants that refer to the requesting process's keyrings (KEY_SPEC_*_KEYRING, all <= 0), then: (a) If sys_request_key() was given a keyring to use (destringid) then the key will be attached to that keyring. (b) If sys_request_key() was given a NULL keyring, then the key being instantiated will be attached to the default keyring as set by keyctl_set_reqkey_keyring(). (3) No extra link will be made. Decision point (1) follows current behaviour, and allows those instantiators who've searched for a specifically named keyring in the requestor's keyring so as to partition the keys by type to still have their named keyrings. Decision point (2) allows the requestor to make sure that the key or keys that get produced by request_key() go where they want, whilst allowing the instantiator to request that the key is retained. This is mainly useful for situations where the instantiator makes a secondary request, the key for which should be retained by the initial requestor: +-----------+ +--------------+ +--------------+ | | | | | | | Requestor |------->| Instantiator |------->| Instantiator | | | | | | | +-----------+ +--------------+ +--------------+ request_key() request_key() This might be useful, for example, in Kerberos, where the requestor requests a ticket, and then the ticket instantiator requests the TGT, which someone else then has to go and fetch. The TGT, however, should be retained in the keyrings of the requestor, not the first instantiator. To make this explict an extra special keyring constant is also added. Signed-off-by: David Howells Reviewed-by: James Morris Signed-off-by: James Morris --- security/keys/process_keys.c | 88 +++++++++++++++++++++++++++----------------- 1 file changed, 54 insertions(+), 34 deletions(-) (limited to 'security/keys/process_keys.c') diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c index 5be6d018759a..1c793b7090a7 100644 --- a/security/keys/process_keys.c +++ b/security/keys/process_keys.c @@ -40,9 +40,9 @@ struct key_user root_key_user = { /* * install user and user session keyrings for a particular UID */ -static int install_user_keyrings(struct task_struct *tsk) +int install_user_keyrings(void) { - struct user_struct *user = tsk->user; + struct user_struct *user = current->user; struct key *uid_keyring, *session_keyring; char buf[20]; int ret; @@ -67,7 +67,7 @@ static int install_user_keyrings(struct task_struct *tsk) uid_keyring = find_keyring_by_name(buf, true); if (IS_ERR(uid_keyring)) { uid_keyring = keyring_alloc(buf, user->uid, (gid_t) -1, - tsk, KEY_ALLOC_IN_QUOTA, + current, KEY_ALLOC_IN_QUOTA, NULL); if (IS_ERR(uid_keyring)) { ret = PTR_ERR(uid_keyring); @@ -83,7 +83,8 @@ static int install_user_keyrings(struct task_struct *tsk) if (IS_ERR(session_keyring)) { session_keyring = keyring_alloc(buf, user->uid, (gid_t) -1, - tsk, KEY_ALLOC_IN_QUOTA, NULL); + current, KEY_ALLOC_IN_QUOTA, + NULL); if (IS_ERR(session_keyring)) { ret = PTR_ERR(session_keyring); goto error_release; @@ -146,8 +147,9 @@ void switch_uid_keyring(struct user_struct *new_user) /* * install a fresh thread keyring, discarding the old one */ -int install_thread_keyring(struct task_struct *tsk) +int install_thread_keyring(void) { + struct task_struct *tsk = current; struct key *keyring, *old; char buf[20]; int ret; @@ -178,8 +180,9 @@ error: /* * make sure a process keyring is installed */ -int install_process_keyring(struct task_struct *tsk) +int install_process_keyring(void) { + struct task_struct *tsk = current; struct key *keyring; char buf[20]; int ret; @@ -218,9 +221,9 @@ error: * install a session keyring, discarding the old one * - if a keyring is not supplied, an empty one is invented */ -static int install_session_keyring(struct task_struct *tsk, - struct key *keyring) +static int install_session_keyring(struct key *keyring) { + struct task_struct *tsk = current; unsigned long flags; struct key *old; char buf[20]; @@ -572,93 +575,91 @@ static int lookup_user_key_possessed(const struct key *key, const void *target) * - don't create special keyrings unless so requested * - partially constructed keys aren't found unless requested */ -key_ref_t lookup_user_key(struct task_struct *context, key_serial_t id, - int create, int partial, key_perm_t perm) +key_ref_t lookup_user_key(key_serial_t id, int create, int partial, + key_perm_t perm) { + struct request_key_auth *rka; + struct task_struct *t = current; key_ref_t key_ref, skey_ref; struct key *key; int ret; - if (!context) - context = current; - key_ref = ERR_PTR(-ENOKEY); switch (id) { case KEY_SPEC_THREAD_KEYRING: - if (!context->thread_keyring) { + if (!t->thread_keyring) { if (!create) goto error; - ret = install_thread_keyring(context); + ret = install_thread_keyring(); if (ret < 0) { key = ERR_PTR(ret); goto error; } } - key = context->thread_keyring; + key = t->thread_keyring; atomic_inc(&key->usage); key_ref = make_key_ref(key, 1); break; case KEY_SPEC_PROCESS_KEYRING: - if (!context->signal->process_keyring) { + if (!t->signal->process_keyring) { if (!create) goto error; - ret = install_process_keyring(context); + ret = install_process_keyring(); if (ret < 0) { key = ERR_PTR(ret); goto error; } } - key = context->signal->process_keyring; + key = t->signal->process_keyring; atomic_inc(&key->usage); key_ref = make_key_ref(key, 1); break; case KEY_SPEC_SESSION_KEYRING: - if (!context->signal->session_keyring) { + if (!t->signal->session_keyring) { /* always install a session keyring upon access if one * doesn't exist yet */ - ret = install_user_keyrings(context); + ret = install_user_keyrings(); if (ret < 0) goto error; - ret = install_session_keyring( - context, context->user->session_keyring); + ret = install_session_keyring(t->user->session_keyring); if (ret < 0) goto error; } rcu_read_lock(); - key = rcu_dereference(context->signal->session_keyring); + key = rcu_dereference(t->signal->session_keyring); atomic_inc(&key->usage); rcu_read_unlock(); key_ref = make_key_ref(key, 1); break; case KEY_SPEC_USER_KEYRING: - if (!context->user->uid_keyring) { - ret = install_user_keyrings(context); + if (!t->user->uid_keyring) { + ret = install_user_keyrings(); if (ret < 0) goto error; } - key = context->user->uid_keyring; + key = t->user->uid_keyring; atomic_inc(&key->usage); key_ref = make_key_ref(key, 1); break; case KEY_SPEC_USER_SESSION_KEYRING: - if (!context->user->session_keyring) { - ret = install_user_keyrings(context); + if (!t->user->session_keyring) { + ret = install_user_keyrings(); if (ret < 0) goto error; } - key = context->user->session_keyring; + key = t->user->session_keyring; atomic_inc(&key->usage); key_ref = make_key_ref(key, 1); break; @@ -669,7 +670,7 @@ key_ref_t lookup_user_key(struct task_struct *context, key_serial_t id, goto error; case KEY_SPEC_REQKEY_AUTH_KEY: - key = context->request_key_auth; + key = t->request_key_auth; if (!key) goto error; @@ -677,6 +678,25 @@ key_ref_t lookup_user_key(struct task_struct *context, key_serial_t id, key_ref = make_key_ref(key, 1); break; + case KEY_SPEC_REQUESTOR_KEYRING: + if (!t->request_key_auth) + goto error; + + down_read(&t->request_key_auth->sem); + if (t->request_key_auth->flags & KEY_FLAG_REVOKED) { + key_ref = ERR_PTR(-EKEYREVOKED); + key = NULL; + } else { + rka = t->request_key_auth->payload.data; + key = rka->dest_keyring; + atomic_inc(&key->usage); + } + up_read(&t->request_key_auth->sem); + if (!key) + goto error; + key_ref = make_key_ref(key, 1); + break; + default: key_ref = ERR_PTR(-EINVAL); if (id < 1) @@ -725,7 +745,7 @@ key_ref_t lookup_user_key(struct task_struct *context, key_serial_t id, goto invalid_key; /* check the permissions */ - ret = key_task_permission(key_ref, context, perm); + ret = key_task_permission(key_ref, t, perm); if (ret < 0) goto invalid_key; @@ -754,7 +774,7 @@ long join_session_keyring(const char *name) /* if no name is provided, install an anonymous keyring */ if (!name) { - ret = install_session_keyring(tsk, NULL); + ret = install_session_keyring(NULL); if (ret < 0) goto error; @@ -784,7 +804,7 @@ long join_session_keyring(const char *name) } /* we've got a keyring - now to install it */ - ret = install_session_keyring(tsk, keyring); + ret = install_session_keyring(keyring); if (ret < 0) goto error2; -- cgit v1.2.3 From b6dff3ec5e116e3af6f537d4caedcad6b9e5082a Mon Sep 17 00:00:00 2001 From: David Howells Date: Fri, 14 Nov 2008 10:39:16 +1100 Subject: CRED: Separate task security context from task_struct Separate the task security context from task_struct. At this point, the security data is temporarily embedded in the task_struct with two pointers pointing to it. Note that the Alpha arch is altered as it refers to (E)UID and (E)GID in entry.S via asm-offsets. With comment fixes Signed-off-by: Marc Dionne Signed-off-by: David Howells Acked-by: James Morris Acked-by: Serge Hallyn Signed-off-by: James Morris --- security/keys/process_keys.c | 98 +++++++++++++++++++++++--------------------- 1 file changed, 51 insertions(+), 47 deletions(-) (limited to 'security/keys/process_keys.c') diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c index 1c793b7090a7..b0904cdda2e7 100644 --- a/security/keys/process_keys.c +++ b/security/keys/process_keys.c @@ -42,7 +42,7 @@ struct key_user root_key_user = { */ int install_user_keyrings(void) { - struct user_struct *user = current->user; + struct user_struct *user = current->cred->user; struct key *uid_keyring, *session_keyring; char buf[20]; int ret; @@ -156,7 +156,7 @@ int install_thread_keyring(void) sprintf(buf, "_tid.%u", tsk->pid); - keyring = keyring_alloc(buf, tsk->uid, tsk->gid, tsk, + keyring = keyring_alloc(buf, tsk->cred->uid, tsk->cred->gid, tsk, KEY_ALLOC_QUOTA_OVERRUN, NULL); if (IS_ERR(keyring)) { ret = PTR_ERR(keyring); @@ -164,8 +164,8 @@ int install_thread_keyring(void) } task_lock(tsk); - old = tsk->thread_keyring; - tsk->thread_keyring = keyring; + old = tsk->cred->thread_keyring; + tsk->cred->thread_keyring = keyring; task_unlock(tsk); ret = 0; @@ -192,7 +192,7 @@ int install_process_keyring(void) if (!tsk->signal->process_keyring) { sprintf(buf, "_pid.%u", tsk->tgid); - keyring = keyring_alloc(buf, tsk->uid, tsk->gid, tsk, + keyring = keyring_alloc(buf, tsk->cred->uid, tsk->cred->gid, tsk, KEY_ALLOC_QUOTA_OVERRUN, NULL); if (IS_ERR(keyring)) { ret = PTR_ERR(keyring); @@ -238,7 +238,7 @@ static int install_session_keyring(struct key *keyring) if (tsk->signal->session_keyring) flags = KEY_ALLOC_IN_QUOTA; - keyring = keyring_alloc(buf, tsk->uid, tsk->gid, tsk, + keyring = keyring_alloc(buf, tsk->cred->uid, tsk->cred->gid, tsk, flags, NULL); if (IS_ERR(keyring)) return PTR_ERR(keyring); @@ -292,14 +292,14 @@ int copy_thread_group_keys(struct task_struct *tsk) */ int copy_keys(unsigned long clone_flags, struct task_struct *tsk) { - key_check(tsk->thread_keyring); - key_check(tsk->request_key_auth); + key_check(tsk->cred->thread_keyring); + key_check(tsk->cred->request_key_auth); /* no thread keyring yet */ - tsk->thread_keyring = NULL; + tsk->cred->thread_keyring = NULL; /* copy the request_key() authorisation for this thread */ - key_get(tsk->request_key_auth); + key_get(tsk->cred->request_key_auth); return 0; @@ -322,8 +322,8 @@ void exit_thread_group_keys(struct signal_struct *tg) */ void exit_keys(struct task_struct *tsk) { - key_put(tsk->thread_keyring); - key_put(tsk->request_key_auth); + key_put(tsk->cred->thread_keyring); + key_put(tsk->cred->request_key_auth); } /* end exit_keys() */ @@ -337,8 +337,8 @@ int exec_keys(struct task_struct *tsk) /* newly exec'd tasks don't get a thread keyring */ task_lock(tsk); - old = tsk->thread_keyring; - tsk->thread_keyring = NULL; + old = tsk->cred->thread_keyring; + tsk->cred->thread_keyring = NULL; task_unlock(tsk); key_put(old); @@ -373,10 +373,11 @@ int suid_keys(struct task_struct *tsk) void key_fsuid_changed(struct task_struct *tsk) { /* update the ownership of the thread keyring */ - if (tsk->thread_keyring) { - down_write(&tsk->thread_keyring->sem); - tsk->thread_keyring->uid = tsk->fsuid; - up_write(&tsk->thread_keyring->sem); + BUG_ON(!tsk->cred); + if (tsk->cred->thread_keyring) { + down_write(&tsk->cred->thread_keyring->sem); + tsk->cred->thread_keyring->uid = tsk->cred->fsuid; + up_write(&tsk->cred->thread_keyring->sem); } } /* end key_fsuid_changed() */ @@ -388,10 +389,11 @@ void key_fsuid_changed(struct task_struct *tsk) void key_fsgid_changed(struct task_struct *tsk) { /* update the ownership of the thread keyring */ - if (tsk->thread_keyring) { - down_write(&tsk->thread_keyring->sem); - tsk->thread_keyring->gid = tsk->fsgid; - up_write(&tsk->thread_keyring->sem); + BUG_ON(!tsk->cred); + if (tsk->cred->thread_keyring) { + down_write(&tsk->cred->thread_keyring->sem); + tsk->cred->thread_keyring->gid = tsk->cred->fsgid; + up_write(&tsk->cred->thread_keyring->sem); } } /* end key_fsgid_changed() */ @@ -426,9 +428,9 @@ key_ref_t search_process_keyrings(struct key_type *type, err = ERR_PTR(-EAGAIN); /* search the thread keyring first */ - if (context->thread_keyring) { + if (context->cred->thread_keyring) { key_ref = keyring_search_aux( - make_key_ref(context->thread_keyring, 1), + make_key_ref(context->cred->thread_keyring, 1), context, type, description, match); if (!IS_ERR(key_ref)) goto found; @@ -493,9 +495,9 @@ key_ref_t search_process_keyrings(struct key_type *type, } } /* or search the user-session keyring */ - else if (context->user->session_keyring) { + else if (context->cred->user->session_keyring) { key_ref = keyring_search_aux( - make_key_ref(context->user->session_keyring, 1), + make_key_ref(context->cred->user->session_keyring, 1), context, type, description, match); if (!IS_ERR(key_ref)) goto found; @@ -517,20 +519,20 @@ key_ref_t search_process_keyrings(struct key_type *type, * search the keyrings of the process mentioned there * - we don't permit access to request_key auth keys via this method */ - if (context->request_key_auth && + if (context->cred->request_key_auth && context == current && type != &key_type_request_key_auth ) { /* defend against the auth key being revoked */ - down_read(&context->request_key_auth->sem); + down_read(&context->cred->request_key_auth->sem); - if (key_validate(context->request_key_auth) == 0) { - rka = context->request_key_auth->payload.data; + if (key_validate(context->cred->request_key_auth) == 0) { + rka = context->cred->request_key_auth->payload.data; key_ref = search_process_keyrings(type, description, match, rka->context); - up_read(&context->request_key_auth->sem); + up_read(&context->cred->request_key_auth->sem); if (!IS_ERR(key_ref)) goto found; @@ -547,7 +549,7 @@ key_ref_t search_process_keyrings(struct key_type *type, break; } } else { - up_read(&context->request_key_auth->sem); + up_read(&context->cred->request_key_auth->sem); } } @@ -580,15 +582,16 @@ key_ref_t lookup_user_key(key_serial_t id, int create, int partial, { struct request_key_auth *rka; struct task_struct *t = current; - key_ref_t key_ref, skey_ref; + struct cred *cred = t->cred; struct key *key; + key_ref_t key_ref, skey_ref; int ret; key_ref = ERR_PTR(-ENOKEY); switch (id) { case KEY_SPEC_THREAD_KEYRING: - if (!t->thread_keyring) { + if (!cred->thread_keyring) { if (!create) goto error; @@ -599,7 +602,7 @@ key_ref_t lookup_user_key(key_serial_t id, int create, int partial, } } - key = t->thread_keyring; + key = cred->thread_keyring; atomic_inc(&key->usage); key_ref = make_key_ref(key, 1); break; @@ -628,7 +631,8 @@ key_ref_t lookup_user_key(key_serial_t id, int create, int partial, ret = install_user_keyrings(); if (ret < 0) goto error; - ret = install_session_keyring(t->user->session_keyring); + ret = install_session_keyring( + cred->user->session_keyring); if (ret < 0) goto error; } @@ -641,25 +645,25 @@ key_ref_t lookup_user_key(key_serial_t id, int create, int partial, break; case KEY_SPEC_USER_KEYRING: - if (!t->user->uid_keyring) { + if (!cred->user->uid_keyring) { ret = install_user_keyrings(); if (ret < 0) goto error; } - key = t->user->uid_keyring; + key = cred->user->uid_keyring; atomic_inc(&key->usage); key_ref = make_key_ref(key, 1); break; case KEY_SPEC_USER_SESSION_KEYRING: - if (!t->user->session_keyring) { + if (!cred->user->session_keyring) { ret = install_user_keyrings(); if (ret < 0) goto error; } - key = t->user->session_keyring; + key = cred->user->session_keyring; atomic_inc(&key->usage); key_ref = make_key_ref(key, 1); break; @@ -670,7 +674,7 @@ key_ref_t lookup_user_key(key_serial_t id, int create, int partial, goto error; case KEY_SPEC_REQKEY_AUTH_KEY: - key = t->request_key_auth; + key = cred->request_key_auth; if (!key) goto error; @@ -679,19 +683,19 @@ key_ref_t lookup_user_key(key_serial_t id, int create, int partial, break; case KEY_SPEC_REQUESTOR_KEYRING: - if (!t->request_key_auth) + if (!cred->request_key_auth) goto error; - down_read(&t->request_key_auth->sem); - if (t->request_key_auth->flags & KEY_FLAG_REVOKED) { + down_read(&cred->request_key_auth->sem); + if (cred->request_key_auth->flags & KEY_FLAG_REVOKED) { key_ref = ERR_PTR(-EKEYREVOKED); key = NULL; } else { - rka = t->request_key_auth->payload.data; + rka = cred->request_key_auth->payload.data; key = rka->dest_keyring; atomic_inc(&key->usage); } - up_read(&t->request_key_auth->sem); + up_read(&cred->request_key_auth->sem); if (!key) goto error; key_ref = make_key_ref(key, 1); @@ -791,7 +795,7 @@ long join_session_keyring(const char *name) keyring = find_keyring_by_name(name, false); if (PTR_ERR(keyring) == -ENOKEY) { /* not found - try and create a new one */ - keyring = keyring_alloc(name, tsk->uid, tsk->gid, tsk, + keyring = keyring_alloc(name, tsk->cred->uid, tsk->cred->gid, tsk, KEY_ALLOC_IN_QUOTA, NULL); if (IS_ERR(keyring)) { ret = PTR_ERR(keyring); -- cgit v1.2.3 From 86a264abe542cfececb4df129bc45a0338d8cdb9 Mon Sep 17 00:00:00 2001 From: David Howells Date: Fri, 14 Nov 2008 10:39:18 +1100 Subject: CRED: Wrap current->cred and a few other accessors Wrap current->cred and a few other accessors to hide their actual implementation. Signed-off-by: David Howells Acked-by: James Morris Acked-by: Serge Hallyn Signed-off-by: James Morris --- security/keys/process_keys.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'security/keys/process_keys.c') diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c index b0904cdda2e7..ce8ac6073d57 100644 --- a/security/keys/process_keys.c +++ b/security/keys/process_keys.c @@ -582,7 +582,7 @@ key_ref_t lookup_user_key(key_serial_t id, int create, int partial, { struct request_key_auth *rka; struct task_struct *t = current; - struct cred *cred = t->cred; + struct cred *cred = current_cred(); struct key *key; key_ref_t key_ref, skey_ref; int ret; -- cgit v1.2.3 From c69e8d9c01db2adc503464993c358901c9af9de4 Mon Sep 17 00:00:00 2001 From: David Howells Date: Fri, 14 Nov 2008 10:39:19 +1100 Subject: CRED: Use RCU to access another task's creds and to release a task's own creds Use RCU to access another task's creds and to release a task's own creds. This means that it will be possible for the credentials of a task to be replaced without another task (a) requiring a full lock to read them, and (b) seeing deallocated memory. Signed-off-by: David Howells Acked-by: James Morris Acked-by: Serge Hallyn Signed-off-by: James Morris --- security/keys/process_keys.c | 24 ++++++++++++++---------- 1 file changed, 14 insertions(+), 10 deletions(-) (limited to 'security/keys/process_keys.c') diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c index ce8ac6073d57..212601ebaa46 100644 --- a/security/keys/process_keys.c +++ b/security/keys/process_keys.c @@ -412,10 +412,13 @@ key_ref_t search_process_keyrings(struct key_type *type, struct task_struct *context) { struct request_key_auth *rka; + struct cred *cred; key_ref_t key_ref, ret, err; might_sleep(); + cred = get_task_cred(context); + /* we want to return -EAGAIN or -ENOKEY if any of the keyrings were * searchable, but we failed to find a key or we found a negative key; * otherwise we want to return a sample error (probably -EACCES) if @@ -428,9 +431,9 @@ key_ref_t search_process_keyrings(struct key_type *type, err = ERR_PTR(-EAGAIN); /* search the thread keyring first */ - if (context->cred->thread_keyring) { + if (cred->thread_keyring) { key_ref = keyring_search_aux( - make_key_ref(context->cred->thread_keyring, 1), + make_key_ref(cred->thread_keyring, 1), context, type, description, match); if (!IS_ERR(key_ref)) goto found; @@ -495,9 +498,9 @@ key_ref_t search_process_keyrings(struct key_type *type, } } /* or search the user-session keyring */ - else if (context->cred->user->session_keyring) { + else if (cred->user->session_keyring) { key_ref = keyring_search_aux( - make_key_ref(context->cred->user->session_keyring, 1), + make_key_ref(cred->user->session_keyring, 1), context, type, description, match); if (!IS_ERR(key_ref)) goto found; @@ -519,20 +522,20 @@ key_ref_t search_process_keyrings(struct key_type *type, * search the keyrings of the process mentioned there * - we don't permit access to request_key auth keys via this method */ - if (context->cred->request_key_auth && + if (cred->request_key_auth && context == current && type != &key_type_request_key_auth ) { /* defend against the auth key being revoked */ - down_read(&context->cred->request_key_auth->sem); + down_read(&cred->request_key_auth->sem); - if (key_validate(context->cred->request_key_auth) == 0) { - rka = context->cred->request_key_auth->payload.data; + if (key_validate(cred->request_key_auth) == 0) { + rka = cred->request_key_auth->payload.data; key_ref = search_process_keyrings(type, description, match, rka->context); - up_read(&context->cred->request_key_auth->sem); + up_read(&cred->request_key_auth->sem); if (!IS_ERR(key_ref)) goto found; @@ -549,7 +552,7 @@ key_ref_t search_process_keyrings(struct key_type *type, break; } } else { - up_read(&context->cred->request_key_auth->sem); + up_read(&cred->request_key_auth->sem); } } @@ -557,6 +560,7 @@ key_ref_t search_process_keyrings(struct key_type *type, key_ref = ret ? ret : err; found: + put_cred(cred); return key_ref; } /* end search_process_keyrings() */ -- cgit v1.2.3 From bb952bb98a7e479262c7eb25d5592545a3af147d Mon Sep 17 00:00:00 2001 From: David Howells Date: Fri, 14 Nov 2008 10:39:20 +1100 Subject: CRED: Separate per-task-group keyrings from signal_struct Separate per-task-group keyrings from signal_struct and dangle their anchor from the cred struct rather than the signal_struct. Signed-off-by: David Howells Reviewed-by: James Morris Signed-off-by: James Morris --- security/keys/process_keys.c | 100 +++++++++++++++++-------------------------- 1 file changed, 40 insertions(+), 60 deletions(-) (limited to 'security/keys/process_keys.c') diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c index 212601ebaa46..70ee93406f30 100644 --- a/security/keys/process_keys.c +++ b/security/keys/process_keys.c @@ -189,7 +189,7 @@ int install_process_keyring(void) might_sleep(); - if (!tsk->signal->process_keyring) { + if (!tsk->cred->tgcred->process_keyring) { sprintf(buf, "_pid.%u", tsk->tgid); keyring = keyring_alloc(buf, tsk->cred->uid, tsk->cred->gid, tsk, @@ -200,12 +200,12 @@ int install_process_keyring(void) } /* attach keyring */ - spin_lock_irq(&tsk->sighand->siglock); - if (!tsk->signal->process_keyring) { - tsk->signal->process_keyring = keyring; + spin_lock_irq(&tsk->cred->tgcred->lock); + if (!tsk->cred->tgcred->process_keyring) { + tsk->cred->tgcred->process_keyring = keyring; keyring = NULL; } - spin_unlock_irq(&tsk->sighand->siglock); + spin_unlock_irq(&tsk->cred->tgcred->lock); key_put(keyring); } @@ -235,11 +235,11 @@ static int install_session_keyring(struct key *keyring) sprintf(buf, "_ses.%u", tsk->tgid); flags = KEY_ALLOC_QUOTA_OVERRUN; - if (tsk->signal->session_keyring) + if (tsk->cred->tgcred->session_keyring) flags = KEY_ALLOC_IN_QUOTA; - keyring = keyring_alloc(buf, tsk->cred->uid, tsk->cred->gid, tsk, - flags, NULL); + keyring = keyring_alloc(buf, tsk->cred->uid, tsk->cred->gid, + tsk, flags, NULL); if (IS_ERR(keyring)) return PTR_ERR(keyring); } @@ -248,10 +248,10 @@ static int install_session_keyring(struct key *keyring) } /* install the keyring */ - spin_lock_irq(&tsk->sighand->siglock); - old = tsk->signal->session_keyring; - rcu_assign_pointer(tsk->signal->session_keyring, keyring); - spin_unlock_irq(&tsk->sighand->siglock); + spin_lock_irq(&tsk->cred->tgcred->lock); + old = tsk->cred->tgcred->session_keyring; + rcu_assign_pointer(tsk->cred->tgcred->session_keyring, keyring); + spin_unlock_irq(&tsk->cred->tgcred->lock); /* we're using RCU on the pointer, but there's no point synchronising * on it if it didn't previously point to anything */ @@ -264,28 +264,6 @@ static int install_session_keyring(struct key *keyring) } /* end install_session_keyring() */ -/*****************************************************************************/ -/* - * copy the keys in a thread group for fork without CLONE_THREAD - */ -int copy_thread_group_keys(struct task_struct *tsk) -{ - key_check(current->thread_group->session_keyring); - key_check(current->thread_group->process_keyring); - - /* no process keyring yet */ - tsk->signal->process_keyring = NULL; - - /* same session keyring */ - rcu_read_lock(); - tsk->signal->session_keyring = - key_get(rcu_dereference(current->signal->session_keyring)); - rcu_read_unlock(); - - return 0; - -} /* end copy_thread_group_keys() */ - /*****************************************************************************/ /* * copy the keys for fork @@ -305,17 +283,6 @@ int copy_keys(unsigned long clone_flags, struct task_struct *tsk) } /* end copy_keys() */ -/*****************************************************************************/ -/* - * dispose of thread group keys upon thread group destruction - */ -void exit_thread_group_keys(struct signal_struct *tg) -{ - key_put(tg->session_keyring); - key_put(tg->process_keyring); - -} /* end exit_thread_group_keys() */ - /*****************************************************************************/ /* * dispose of per-thread keys upon thread exit @@ -344,10 +311,10 @@ int exec_keys(struct task_struct *tsk) key_put(old); /* discard the process keyring from a newly exec'd task */ - spin_lock_irq(&tsk->sighand->siglock); - old = tsk->signal->process_keyring; - tsk->signal->process_keyring = NULL; - spin_unlock_irq(&tsk->sighand->siglock); + spin_lock_irq(&tsk->cred->tgcred->lock); + old = tsk->cred->tgcred->process_keyring; + tsk->cred->tgcred->process_keyring = NULL; + spin_unlock_irq(&tsk->cred->tgcred->lock); key_put(old); @@ -452,9 +419,9 @@ key_ref_t search_process_keyrings(struct key_type *type, } /* search the process keyring second */ - if (context->signal->process_keyring) { + if (cred->tgcred->process_keyring) { key_ref = keyring_search_aux( - make_key_ref(context->signal->process_keyring, 1), + make_key_ref(cred->tgcred->process_keyring, 1), context, type, description, match); if (!IS_ERR(key_ref)) goto found; @@ -473,11 +440,11 @@ key_ref_t search_process_keyrings(struct key_type *type, } /* search the session keyring */ - if (context->signal->session_keyring) { + if (cred->tgcred->session_keyring) { rcu_read_lock(); key_ref = keyring_search_aux( make_key_ref(rcu_dereference( - context->signal->session_keyring), + cred->tgcred->session_keyring), 1), context, type, description, match); rcu_read_unlock(); @@ -586,11 +553,13 @@ key_ref_t lookup_user_key(key_serial_t id, int create, int partial, { struct request_key_auth *rka; struct task_struct *t = current; - struct cred *cred = current_cred(); + struct cred *cred; struct key *key; key_ref_t key_ref, skey_ref; int ret; +try_again: + cred = get_current_cred(); key_ref = ERR_PTR(-ENOKEY); switch (id) { @@ -604,6 +573,7 @@ key_ref_t lookup_user_key(key_serial_t id, int create, int partial, key = ERR_PTR(ret); goto error; } + goto reget_creds; } key = cred->thread_keyring; @@ -612,7 +582,7 @@ key_ref_t lookup_user_key(key_serial_t id, int create, int partial, break; case KEY_SPEC_PROCESS_KEYRING: - if (!t->signal->process_keyring) { + if (!cred->tgcred->process_keyring) { if (!create) goto error; @@ -621,15 +591,16 @@ key_ref_t lookup_user_key(key_serial_t id, int create, int partial, key = ERR_PTR(ret); goto error; } + goto reget_creds; } - key = t->signal->process_keyring; + key = cred->tgcred->process_keyring; atomic_inc(&key->usage); key_ref = make_key_ref(key, 1); break; case KEY_SPEC_SESSION_KEYRING: - if (!t->signal->session_keyring) { + if (!cred->tgcred->session_keyring) { /* always install a session keyring upon access if one * doesn't exist yet */ ret = install_user_keyrings(); @@ -639,10 +610,11 @@ key_ref_t lookup_user_key(key_serial_t id, int create, int partial, cred->user->session_keyring); if (ret < 0) goto error; + goto reget_creds; } rcu_read_lock(); - key = rcu_dereference(t->signal->session_keyring); + key = rcu_dereference(cred->tgcred->session_keyring); atomic_inc(&key->usage); rcu_read_unlock(); key_ref = make_key_ref(key, 1); @@ -758,6 +730,7 @@ key_ref_t lookup_user_key(key_serial_t id, int create, int partial, goto invalid_key; error: + put_cred(cred); return key_ref; invalid_key: @@ -765,6 +738,12 @@ invalid_key: key_ref = ERR_PTR(ret); goto error; + /* if we attempted to install a keyring, then it may have caused new + * creds to be installed */ +reget_creds: + put_cred(cred); + goto try_again; + } /* end lookup_user_key() */ /*****************************************************************************/ @@ -777,6 +756,7 @@ invalid_key: long join_session_keyring(const char *name) { struct task_struct *tsk = current; + struct cred *cred = current->cred; struct key *keyring; long ret; @@ -787,7 +767,7 @@ long join_session_keyring(const char *name) goto error; rcu_read_lock(); - ret = rcu_dereference(tsk->signal->session_keyring)->serial; + ret = rcu_dereference(cred->tgcred->session_keyring)->serial; rcu_read_unlock(); goto error; } @@ -799,7 +779,7 @@ long join_session_keyring(const char *name) keyring = find_keyring_by_name(name, false); if (PTR_ERR(keyring) == -ENOKEY) { /* not found - try and create a new one */ - keyring = keyring_alloc(name, tsk->cred->uid, tsk->cred->gid, tsk, + keyring = keyring_alloc(name, cred->uid, cred->gid, tsk, KEY_ALLOC_IN_QUOTA, NULL); if (IS_ERR(keyring)) { ret = PTR_ERR(keyring); -- cgit v1.2.3 From d84f4f992cbd76e8f39c488cf0c5d123843923b1 Mon Sep 17 00:00:00 2001 From: David Howells Date: Fri, 14 Nov 2008 10:39:23 +1100 Subject: CRED: Inaugurate COW credentials Inaugurate copy-on-write credentials management. This uses RCU to manage the credentials pointer in the task_struct with respect to accesses by other tasks. A process may only modify its own credentials, and so does not need locking to access or modify its own credentials. A mutex (cred_replace_mutex) is added to the task_struct to control the effect of PTRACE_ATTACHED on credential calculations, particularly with respect to execve(). With this patch, the contents of an active credentials struct may not be changed directly; rather a new set of credentials must be prepared, modified and committed using something like the following sequence of events: struct cred *new = prepare_creds(); int ret = blah(new); if (ret < 0) { abort_creds(new); return ret; } return commit_creds(new); There are some exceptions to this rule: the keyrings pointed to by the active credentials may be instantiated - keyrings violate the COW rule as managing COW keyrings is tricky, given that it is possible for a task to directly alter the keys in a keyring in use by another task. To help enforce this, various pointers to sets of credentials, such as those in the task_struct, are declared const. The purpose of this is compile-time discouragement of altering credentials through those pointers. Once a set of credentials has been made public through one of these pointers, it may not be modified, except under special circumstances: (1) Its reference count may incremented and decremented. (2) The keyrings to which it points may be modified, but not replaced. The only safe way to modify anything else is to create a replacement and commit using the functions described in Documentation/credentials.txt (which will be added by a later patch). This patch and the preceding patches have been tested with the LTP SELinux testsuite. This patch makes several logical sets of alteration: (1) execve(). This now prepares and commits credentials in various places in the security code rather than altering the current creds directly. (2) Temporary credential overrides. do_coredump() and sys_faccessat() now prepare their own credentials and temporarily override the ones currently on the acting thread, whilst preventing interference from other threads by holding cred_replace_mutex on the thread being dumped. This will be replaced in a future patch by something that hands down the credentials directly to the functions being called, rather than altering the task's objective credentials. (3) LSM interface. A number of functions have been changed, added or removed: (*) security_capset_check(), ->capset_check() (*) security_capset_set(), ->capset_set() Removed in favour of security_capset(). (*) security_capset(), ->capset() New. This is passed a pointer to the new creds, a pointer to the old creds and the proposed capability sets. It should fill in the new creds or return an error. All pointers, barring the pointer to the new creds, are now const. (*) security_bprm_apply_creds(), ->bprm_apply_creds() Changed; now returns a value, which will cause the process to be killed if it's an error. (*) security_task_alloc(), ->task_alloc_security() Removed in favour of security_prepare_creds(). (*) security_cred_free(), ->cred_free() New. Free security data attached to cred->security. (*) security_prepare_creds(), ->cred_prepare() New. Duplicate any security data attached to cred->security. (*) security_commit_creds(), ->cred_commit() New. Apply any security effects for the upcoming installation of new security by commit_creds(). (*) security_task_post_setuid(), ->task_post_setuid() Removed in favour of security_task_fix_setuid(). (*) security_task_fix_setuid(), ->task_fix_setuid() Fix up the proposed new credentials for setuid(). This is used by cap_set_fix_setuid() to implicitly adjust capabilities in line with setuid() changes. Changes are made to the new credentials, rather than the task itself as in security_task_post_setuid(). (*) security_task_reparent_to_init(), ->task_reparent_to_init() Removed. Instead the task being reparented to init is referred directly to init's credentials. NOTE! This results in the loss of some state: SELinux's osid no longer records the sid of the thread that forked it. (*) security_key_alloc(), ->key_alloc() (*) security_key_permission(), ->key_permission() Changed. These now take cred pointers rather than task pointers to refer to the security context. (4) sys_capset(). This has been simplified and uses less locking. The LSM functions it calls have been merged. (5) reparent_to_kthreadd(). This gives the current thread the same credentials as init by simply using commit_thread() to point that way. (6) __sigqueue_alloc() and switch_uid() __sigqueue_alloc() can't stop the target task from changing its creds beneath it, so this function gets a reference to the currently applicable user_struct which it then passes into the sigqueue struct it returns if successful. switch_uid() is now called from commit_creds(), and possibly should be folded into that. commit_creds() should take care of protecting __sigqueue_alloc(). (7) [sg]et[ug]id() and co and [sg]et_current_groups. The set functions now all use prepare_creds(), commit_creds() and abort_creds() to build and check a new set of credentials before applying it. security_task_set[ug]id() is called inside the prepared section. This guarantees that nothing else will affect the creds until we've finished. The calling of set_dumpable() has been moved into commit_creds(). Much of the functionality of set_user() has been moved into commit_creds(). The get functions all simply access the data directly. (8) security_task_prctl() and cap_task_prctl(). security_task_prctl() has been modified to return -ENOSYS if it doesn't want to handle a function, or otherwise return the return value directly rather than through an argument. Additionally, cap_task_prctl() now prepares a new set of credentials, even if it doesn't end up using it. (9) Keyrings. A number of changes have been made to the keyrings code: (a) switch_uid_keyring(), copy_keys(), exit_keys() and suid_keys() have all been dropped and built in to the credentials functions directly. They may want separating out again later. (b) key_alloc() and search_process_keyrings() now take a cred pointer rather than a task pointer to specify the security context. (c) copy_creds() gives a new thread within the same thread group a new thread keyring if its parent had one, otherwise it discards the thread keyring. (d) The authorisation key now points directly to the credentials to extend the search into rather pointing to the task that carries them. (e) Installing thread, process or session keyrings causes a new set of credentials to be created, even though it's not strictly necessary for process or session keyrings (they're shared). (10) Usermode helper. The usermode helper code now carries a cred struct pointer in its subprocess_info struct instead of a new session keyring pointer. This set of credentials is derived from init_cred and installed on the new process after it has been cloned. call_usermodehelper_setup() allocates the new credentials and call_usermodehelper_freeinfo() discards them if they haven't been used. A special cred function (prepare_usermodeinfo_creds()) is provided specifically for call_usermodehelper_setup() to call. call_usermodehelper_setkeys() adjusts the credentials to sport the supplied keyring as the new session keyring. (11) SELinux. SELinux has a number of changes, in addition to those to support the LSM interface changes mentioned above: (a) selinux_setprocattr() no longer does its check for whether the current ptracer can access processes with the new SID inside the lock that covers getting the ptracer's SID. Whilst this lock ensures that the check is done with the ptracer pinned, the result is only valid until the lock is released, so there's no point doing it inside the lock. (12) is_single_threaded(). This function has been extracted from selinux_setprocattr() and put into a file of its own in the lib/ directory as join_session_keyring() now wants to use it too. The code in SELinux just checked to see whether a task shared mm_structs with other tasks (CLONE_VM), but that isn't good enough. We really want to know if they're part of the same thread group (CLONE_THREAD). (13) nfsd. The NFS server daemon now has to use the COW credentials to set the credentials it is going to use. It really needs to pass the credentials down to the functions it calls, but it can't do that until other patches in this series have been applied. Signed-off-by: David Howells Acked-by: James Morris Signed-off-by: James Morris --- security/keys/process_keys.c | 333 +++++++++++++++++++++---------------------- 1 file changed, 164 insertions(+), 169 deletions(-) (limited to 'security/keys/process_keys.c') diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c index 70ee93406f30..df329f684a65 100644 --- a/security/keys/process_keys.c +++ b/security/keys/process_keys.c @@ -42,11 +42,15 @@ struct key_user root_key_user = { */ int install_user_keyrings(void) { - struct user_struct *user = current->cred->user; + struct user_struct *user; + const struct cred *cred; struct key *uid_keyring, *session_keyring; char buf[20]; int ret; + cred = current_cred(); + user = cred->user; + kenter("%p{%u}", user, user->uid); if (user->uid_keyring) { @@ -67,7 +71,7 @@ int install_user_keyrings(void) uid_keyring = find_keyring_by_name(buf, true); if (IS_ERR(uid_keyring)) { uid_keyring = keyring_alloc(buf, user->uid, (gid_t) -1, - current, KEY_ALLOC_IN_QUOTA, + cred, KEY_ALLOC_IN_QUOTA, NULL); if (IS_ERR(uid_keyring)) { ret = PTR_ERR(uid_keyring); @@ -83,8 +87,7 @@ int install_user_keyrings(void) if (IS_ERR(session_keyring)) { session_keyring = keyring_alloc(buf, user->uid, (gid_t) -1, - current, KEY_ALLOC_IN_QUOTA, - NULL); + cred, KEY_ALLOC_IN_QUOTA, NULL); if (IS_ERR(session_keyring)) { ret = PTR_ERR(session_keyring); goto error_release; @@ -116,142 +119,128 @@ error: return ret; } -/*****************************************************************************/ /* - * deal with the UID changing + * install a fresh thread keyring directly to new credentials */ -void switch_uid_keyring(struct user_struct *new_user) +int install_thread_keyring_to_cred(struct cred *new) { -#if 0 /* do nothing for now */ - struct key *old; - - /* switch to the new user's session keyring if we were running under - * root's default session keyring */ - if (new_user->uid != 0 && - current->session_keyring == &root_session_keyring - ) { - atomic_inc(&new_user->session_keyring->usage); - - task_lock(current); - old = current->session_keyring; - current->session_keyring = new_user->session_keyring; - task_unlock(current); + struct key *keyring; - key_put(old); - } -#endif + keyring = keyring_alloc("_tid", new->uid, new->gid, new, + KEY_ALLOC_QUOTA_OVERRUN, NULL); + if (IS_ERR(keyring)) + return PTR_ERR(keyring); -} /* end switch_uid_keyring() */ + new->thread_keyring = keyring; + return 0; +} -/*****************************************************************************/ /* * install a fresh thread keyring, discarding the old one */ -int install_thread_keyring(void) +static int install_thread_keyring(void) { - struct task_struct *tsk = current; - struct key *keyring, *old; - char buf[20]; + struct cred *new; int ret; - sprintf(buf, "_tid.%u", tsk->pid); + new = prepare_creds(); + if (!new) + return -ENOMEM; - keyring = keyring_alloc(buf, tsk->cred->uid, tsk->cred->gid, tsk, - KEY_ALLOC_QUOTA_OVERRUN, NULL); - if (IS_ERR(keyring)) { - ret = PTR_ERR(keyring); - goto error; + BUG_ON(new->thread_keyring); + + ret = install_thread_keyring_to_cred(new); + if (ret < 0) { + abort_creds(new); + return ret; } - task_lock(tsk); - old = tsk->cred->thread_keyring; - tsk->cred->thread_keyring = keyring; - task_unlock(tsk); + return commit_creds(new); +} - ret = 0; +/* + * install a process keyring directly to a credentials struct + * - returns -EEXIST if there was already a process keyring, 0 if one installed, + * and other -ve on any other error + */ +int install_process_keyring_to_cred(struct cred *new) +{ + struct key *keyring; + int ret; - key_put(old); -error: + if (new->tgcred->process_keyring) + return -EEXIST; + + keyring = keyring_alloc("_pid", new->uid, new->gid, + new, KEY_ALLOC_QUOTA_OVERRUN, NULL); + if (IS_ERR(keyring)) + return PTR_ERR(keyring); + + spin_lock_irq(&new->tgcred->lock); + if (!new->tgcred->process_keyring) { + new->tgcred->process_keyring = keyring; + keyring = NULL; + ret = 0; + } else { + ret = -EEXIST; + } + spin_unlock_irq(&new->tgcred->lock); + key_put(keyring); return ret; +} -} /* end install_thread_keyring() */ - -/*****************************************************************************/ /* * make sure a process keyring is installed + * - we */ -int install_process_keyring(void) +static int install_process_keyring(void) { - struct task_struct *tsk = current; - struct key *keyring; - char buf[20]; + struct cred *new; int ret; - might_sleep(); - - if (!tsk->cred->tgcred->process_keyring) { - sprintf(buf, "_pid.%u", tsk->tgid); - - keyring = keyring_alloc(buf, tsk->cred->uid, tsk->cred->gid, tsk, - KEY_ALLOC_QUOTA_OVERRUN, NULL); - if (IS_ERR(keyring)) { - ret = PTR_ERR(keyring); - goto error; - } - - /* attach keyring */ - spin_lock_irq(&tsk->cred->tgcred->lock); - if (!tsk->cred->tgcred->process_keyring) { - tsk->cred->tgcred->process_keyring = keyring; - keyring = NULL; - } - spin_unlock_irq(&tsk->cred->tgcred->lock); + new = prepare_creds(); + if (!new) + return -ENOMEM; - key_put(keyring); + ret = install_process_keyring_to_cred(new); + if (ret < 0) { + abort_creds(new); + return ret != -EEXIST ?: 0; } - ret = 0; -error: - return ret; - -} /* end install_process_keyring() */ + return commit_creds(new); +} -/*****************************************************************************/ /* - * install a session keyring, discarding the old one - * - if a keyring is not supplied, an empty one is invented + * install a session keyring directly to a credentials struct */ -static int install_session_keyring(struct key *keyring) +static int install_session_keyring_to_cred(struct cred *cred, + struct key *keyring) { - struct task_struct *tsk = current; unsigned long flags; struct key *old; - char buf[20]; might_sleep(); /* create an empty session keyring */ if (!keyring) { - sprintf(buf, "_ses.%u", tsk->tgid); - flags = KEY_ALLOC_QUOTA_OVERRUN; - if (tsk->cred->tgcred->session_keyring) + if (cred->tgcred->session_keyring) flags = KEY_ALLOC_IN_QUOTA; - keyring = keyring_alloc(buf, tsk->cred->uid, tsk->cred->gid, - tsk, flags, NULL); + keyring = keyring_alloc("_ses", cred->uid, cred->gid, + cred, flags, NULL); if (IS_ERR(keyring)) return PTR_ERR(keyring); - } - else { + } else { atomic_inc(&keyring->usage); } /* install the keyring */ - spin_lock_irq(&tsk->cred->tgcred->lock); - old = tsk->cred->tgcred->session_keyring; - rcu_assign_pointer(tsk->cred->tgcred->session_keyring, keyring); - spin_unlock_irq(&tsk->cred->tgcred->lock); + spin_lock_irq(&cred->tgcred->lock); + old = cred->tgcred->session_keyring; + rcu_assign_pointer(cred->tgcred->session_keyring, keyring); + spin_unlock_irq(&cred->tgcred->lock); /* we're using RCU on the pointer, but there's no point synchronising * on it if it didn't previously point to anything */ @@ -261,38 +250,29 @@ static int install_session_keyring(struct key *keyring) } return 0; +} -} /* end install_session_keyring() */ - -/*****************************************************************************/ /* - * copy the keys for fork + * install a session keyring, discarding the old one + * - if a keyring is not supplied, an empty one is invented */ -int copy_keys(unsigned long clone_flags, struct task_struct *tsk) +static int install_session_keyring(struct key *keyring) { - key_check(tsk->cred->thread_keyring); - key_check(tsk->cred->request_key_auth); - - /* no thread keyring yet */ - tsk->cred->thread_keyring = NULL; - - /* copy the request_key() authorisation for this thread */ - key_get(tsk->cred->request_key_auth); - - return 0; + struct cred *new; + int ret; -} /* end copy_keys() */ + new = prepare_creds(); + if (!new) + return -ENOMEM; -/*****************************************************************************/ -/* - * dispose of per-thread keys upon thread exit - */ -void exit_keys(struct task_struct *tsk) -{ - key_put(tsk->cred->thread_keyring); - key_put(tsk->cred->request_key_auth); + ret = install_session_keyring_to_cred(new, NULL); + if (ret < 0) { + abort_creds(new); + return ret; + } -} /* end exit_keys() */ + return commit_creds(new); +} /*****************************************************************************/ /* @@ -300,38 +280,41 @@ void exit_keys(struct task_struct *tsk) */ int exec_keys(struct task_struct *tsk) { - struct key *old; + struct thread_group_cred *tgcred = NULL; + struct cred *new; - /* newly exec'd tasks don't get a thread keyring */ - task_lock(tsk); - old = tsk->cred->thread_keyring; - tsk->cred->thread_keyring = NULL; - task_unlock(tsk); +#ifdef CONFIG_KEYS + tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL); + if (!tgcred) + return -ENOMEM; +#endif - key_put(old); + new = prepare_creds(); + if (new < 0) + return -ENOMEM; - /* discard the process keyring from a newly exec'd task */ - spin_lock_irq(&tsk->cred->tgcred->lock); - old = tsk->cred->tgcred->process_keyring; - tsk->cred->tgcred->process_keyring = NULL; - spin_unlock_irq(&tsk->cred->tgcred->lock); + /* newly exec'd tasks don't get a thread keyring */ + key_put(new->thread_keyring); + new->thread_keyring = NULL; - key_put(old); + /* create a new per-thread-group creds for all this set of threads to + * share */ + memcpy(tgcred, new->tgcred, sizeof(struct thread_group_cred)); - return 0; + atomic_set(&tgcred->usage, 1); + spin_lock_init(&tgcred->lock); -} /* end exec_keys() */ + /* inherit the session keyring; new process keyring */ + key_get(tgcred->session_keyring); + tgcred->process_keyring = NULL; -/*****************************************************************************/ -/* - * deal with SUID programs - * - we might want to make this invent a new session keyring - */ -int suid_keys(struct task_struct *tsk) -{ + release_tgcred(new); + new->tgcred = tgcred; + + commit_creds(new); return 0; -} /* end suid_keys() */ +} /* end exec_keys() */ /*****************************************************************************/ /* @@ -376,16 +359,13 @@ void key_fsgid_changed(struct task_struct *tsk) key_ref_t search_process_keyrings(struct key_type *type, const void *description, key_match_func_t match, - struct task_struct *context) + const struct cred *cred) { struct request_key_auth *rka; - struct cred *cred; key_ref_t key_ref, ret, err; might_sleep(); - cred = get_task_cred(context); - /* we want to return -EAGAIN or -ENOKEY if any of the keyrings were * searchable, but we failed to find a key or we found a negative key; * otherwise we want to return a sample error (probably -EACCES) if @@ -401,7 +381,7 @@ key_ref_t search_process_keyrings(struct key_type *type, if (cred->thread_keyring) { key_ref = keyring_search_aux( make_key_ref(cred->thread_keyring, 1), - context, type, description, match); + cred, type, description, match); if (!IS_ERR(key_ref)) goto found; @@ -422,7 +402,7 @@ key_ref_t search_process_keyrings(struct key_type *type, if (cred->tgcred->process_keyring) { key_ref = keyring_search_aux( make_key_ref(cred->tgcred->process_keyring, 1), - context, type, description, match); + cred, type, description, match); if (!IS_ERR(key_ref)) goto found; @@ -446,7 +426,7 @@ key_ref_t search_process_keyrings(struct key_type *type, make_key_ref(rcu_dereference( cred->tgcred->session_keyring), 1), - context, type, description, match); + cred, type, description, match); rcu_read_unlock(); if (!IS_ERR(key_ref)) @@ -468,7 +448,7 @@ key_ref_t search_process_keyrings(struct key_type *type, else if (cred->user->session_keyring) { key_ref = keyring_search_aux( make_key_ref(cred->user->session_keyring, 1), - context, type, description, match); + cred, type, description, match); if (!IS_ERR(key_ref)) goto found; @@ -490,7 +470,7 @@ key_ref_t search_process_keyrings(struct key_type *type, * - we don't permit access to request_key auth keys via this method */ if (cred->request_key_auth && - context == current && + cred == current_cred() && type != &key_type_request_key_auth ) { /* defend against the auth key being revoked */ @@ -500,7 +480,7 @@ key_ref_t search_process_keyrings(struct key_type *type, rka = cred->request_key_auth->payload.data; key_ref = search_process_keyrings(type, description, - match, rka->context); + match, rka->cred); up_read(&cred->request_key_auth->sem); @@ -527,7 +507,6 @@ key_ref_t search_process_keyrings(struct key_type *type, key_ref = ret ? ret : err; found: - put_cred(cred); return key_ref; } /* end search_process_keyrings() */ @@ -552,8 +531,7 @@ key_ref_t lookup_user_key(key_serial_t id, int create, int partial, key_perm_t perm) { struct request_key_auth *rka; - struct task_struct *t = current; - struct cred *cred; + const struct cred *cred; struct key *key; key_ref_t key_ref, skey_ref; int ret; @@ -608,6 +586,7 @@ try_again: goto error; ret = install_session_keyring( cred->user->session_keyring); + if (ret < 0) goto error; goto reget_creds; @@ -693,7 +672,7 @@ try_again: /* check to see if we possess the key */ skey_ref = search_process_keyrings(key->type, key, lookup_user_key_possessed, - current); + cred); if (!IS_ERR(skey_ref)) { key_put(key); @@ -725,7 +704,7 @@ try_again: goto invalid_key; /* check the permissions */ - ret = key_task_permission(key_ref, t, perm); + ret = key_task_permission(key_ref, cred, perm); if (ret < 0) goto invalid_key; @@ -755,21 +734,33 @@ reget_creds: */ long join_session_keyring(const char *name) { - struct task_struct *tsk = current; - struct cred *cred = current->cred; + const struct cred *old; + struct cred *new; struct key *keyring; - long ret; + long ret, serial; + + /* only permit this if there's a single thread in the thread group - + * this avoids us having to adjust the creds on all threads and risking + * ENOMEM */ + if (!is_single_threaded(current)) + return -EMLINK; + + new = prepare_creds(); + if (!new) + return -ENOMEM; + old = current_cred(); /* if no name is provided, install an anonymous keyring */ if (!name) { - ret = install_session_keyring(NULL); + ret = install_session_keyring_to_cred(new, NULL); if (ret < 0) goto error; - rcu_read_lock(); - ret = rcu_dereference(cred->tgcred->session_keyring)->serial; - rcu_read_unlock(); - goto error; + serial = new->tgcred->session_keyring->serial; + ret = commit_creds(new); + if (ret == 0) + ret = serial; + goto okay; } /* allow the user to join or create a named keyring */ @@ -779,29 +770,33 @@ long join_session_keyring(const char *name) keyring = find_keyring_by_name(name, false); if (PTR_ERR(keyring) == -ENOKEY) { /* not found - try and create a new one */ - keyring = keyring_alloc(name, cred->uid, cred->gid, tsk, + keyring = keyring_alloc(name, old->uid, old->gid, old, KEY_ALLOC_IN_QUOTA, NULL); if (IS_ERR(keyring)) { ret = PTR_ERR(keyring); goto error2; } - } - else if (IS_ERR(keyring)) { + } else if (IS_ERR(keyring)) { ret = PTR_ERR(keyring); goto error2; } /* we've got a keyring - now to install it */ - ret = install_session_keyring(keyring); + ret = install_session_keyring_to_cred(new, keyring); if (ret < 0) goto error2; + commit_creds(new); + mutex_unlock(&key_session_mutex); + ret = keyring->serial; key_put(keyring); +okay: + return ret; error2: mutex_unlock(&key_session_mutex); error: + abort_creds(new); return ret; - -} /* end join_session_keyring() */ +} -- cgit v1.2.3 From a6f76f23d297f70e2a6b3ec607f7aeeea9e37e8d Mon Sep 17 00:00:00 2001 From: David Howells Date: Fri, 14 Nov 2008 10:39:24 +1100 Subject: CRED: Make execve() take advantage of copy-on-write credentials Make execve() take advantage of copy-on-write credentials, allowing it to set up the credentials in advance, and then commit the whole lot after the point of no return. This patch and the preceding patches have been tested with the LTP SELinux testsuite. This patch makes several logical sets of alteration: (1) execve(). The credential bits from struct linux_binprm are, for the most part, replaced with a single credentials pointer (bprm->cred). This means that all the creds can be calculated in advance and then applied at the point of no return with no possibility of failure. I would like to replace bprm->cap_effective with: cap_isclear(bprm->cap_effective) but this seems impossible due to special behaviour for processes of pid 1 (they always retain their parent's capability masks where normally they'd be changed - see cap_bprm_set_creds()). The following sequence of events now happens: (a) At the start of do_execve, the current task's cred_exec_mutex is locked to prevent PTRACE_ATTACH from obsoleting the calculation of creds that we make. (a) prepare_exec_creds() is then called to make a copy of the current task's credentials and prepare it. This copy is then assigned to bprm->cred. This renders security_bprm_alloc() and security_bprm_free() unnecessary, and so they've been removed. (b) The determination of unsafe execution is now performed immediately after (a) rather than later on in the code. The result is stored in bprm->unsafe for future reference. (c) prepare_binprm() is called, possibly multiple times. (i) This applies the result of set[ug]id binaries to the new creds attached to bprm->cred. Personality bit clearance is recorded, but now deferred on the basis that the exec procedure may yet fail. (ii) This then calls the new security_bprm_set_creds(). This should calculate the new LSM and capability credentials into *bprm->cred. This folds together security_bprm_set() and parts of security_bprm_apply_creds() (these two have been removed). Anything that might fail must be done at this point. (iii) bprm->cred_prepared is set to 1. bprm->cred_prepared is 0 on the first pass of the security calculations, and 1 on all subsequent passes. This allows SELinux in (ii) to base its calculations only on the initial script and not on the interpreter. (d) flush_old_exec() is called to commit the task to execution. This performs the following steps with regard to credentials: (i) Clear pdeath_signal and set dumpable on certain circumstances that may not be covered by commit_creds(). (ii) Clear any bits in current->personality that were deferred from (c.i). (e) install_exec_creds() [compute_creds() as was] is called to install the new credentials. This performs the following steps with regard to credentials: (i) Calls security_bprm_committing_creds() to apply any security requirements, such as flushing unauthorised files in SELinux, that must be done before the credentials are changed. This is made up of bits of security_bprm_apply_creds() and security_bprm_post_apply_creds(), both of which have been removed. This function is not allowed to fail; anything that might fail must have been done in (c.ii). (ii) Calls commit_creds() to apply the new credentials in a single assignment (more or less). Possibly pdeath_signal and dumpable should be part of struct creds. (iii) Unlocks the task's cred_replace_mutex, thus allowing PTRACE_ATTACH to take place. (iv) Clears The bprm->cred pointer as the credentials it was holding are now immutable. (v) Calls security_bprm_committed_creds() to apply any security alterations that must be done after the creds have been changed. SELinux uses this to flush signals and signal handlers. (f) If an error occurs before (d.i), bprm_free() will call abort_creds() to destroy the proposed new credentials and will then unlock cred_replace_mutex. No changes to the credentials will have been made. (2) LSM interface. A number of functions have been changed, added or removed: (*) security_bprm_alloc(), ->bprm_alloc_security() (*) security_bprm_free(), ->bprm_free_security() Removed in favour of preparing new credentials and modifying those. (*) security_bprm_apply_creds(), ->bprm_apply_creds() (*) security_bprm_post_apply_creds(), ->bprm_post_apply_creds() Removed; split between security_bprm_set_creds(), security_bprm_committing_creds() and security_bprm_committed_creds(). (*) security_bprm_set(), ->bprm_set_security() Removed; folded into security_bprm_set_creds(). (*) security_bprm_set_creds(), ->bprm_set_creds() New. The new credentials in bprm->creds should be checked and set up as appropriate. bprm->cred_prepared is 0 on the first call, 1 on the second and subsequent calls. (*) security_bprm_committing_creds(), ->bprm_committing_creds() (*) security_bprm_committed_creds(), ->bprm_committed_creds() New. Apply the security effects of the new credentials. This includes closing unauthorised files in SELinux. This function may not fail. When the former is called, the creds haven't yet been applied to the process; when the latter is called, they have. The former may access bprm->cred, the latter may not. (3) SELinux. SELinux has a number of changes, in addition to those to support the LSM interface changes mentioned above: (a) The bprm_security_struct struct has been removed in favour of using the credentials-under-construction approach. (c) flush_unauthorized_files() now takes a cred pointer and passes it on to inode_has_perm(), file_has_perm() and dentry_open(). Signed-off-by: David Howells Acked-by: James Morris Acked-by: Serge Hallyn Signed-off-by: James Morris --- security/keys/process_keys.c | 42 ------------------------------------------ 1 file changed, 42 deletions(-) (limited to 'security/keys/process_keys.c') diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c index df329f684a65..2f5d89e92b85 100644 --- a/security/keys/process_keys.c +++ b/security/keys/process_keys.c @@ -274,48 +274,6 @@ static int install_session_keyring(struct key *keyring) return commit_creds(new); } -/*****************************************************************************/ -/* - * deal with execve() - */ -int exec_keys(struct task_struct *tsk) -{ - struct thread_group_cred *tgcred = NULL; - struct cred *new; - -#ifdef CONFIG_KEYS - tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL); - if (!tgcred) - return -ENOMEM; -#endif - - new = prepare_creds(); - if (new < 0) - return -ENOMEM; - - /* newly exec'd tasks don't get a thread keyring */ - key_put(new->thread_keyring); - new->thread_keyring = NULL; - - /* create a new per-thread-group creds for all this set of threads to - * share */ - memcpy(tgcred, new->tgcred, sizeof(struct thread_group_cred)); - - atomic_set(&tgcred->usage, 1); - spin_lock_init(&tgcred->lock); - - /* inherit the session keyring; new process keyring */ - key_get(tgcred->session_keyring); - tgcred->process_keyring = NULL; - - release_tgcred(new); - new->tgcred = tgcred; - - commit_creds(new); - return 0; - -} /* end exec_keys() */ - /*****************************************************************************/ /* * the filesystem user ID changed -- cgit v1.2.3