From 69664cf16af4f31cd54d77948a4baf9c7e0ca7b9 Mon Sep 17 00:00:00 2001 From: David Howells Date: Tue, 29 Apr 2008 01:01:31 -0700 Subject: keys: don't generate user and user session keyrings unless they're accessed Don't generate the per-UID user and user session keyrings unless they're explicitly accessed. This solves a problem during a login process whereby set*uid() is called before the SELinux PAM module, resulting in the per-UID keyrings having the wrong security labels. This also cures the problem of multiple per-UID keyrings sometimes appearing due to PAM modules (including pam_keyinit) setuiding and causing user_structs to come into and go out of existence whilst the session keyring pins the user keyring. This is achieved by first searching for extant per-UID keyrings before inventing new ones. The serial bound argument is also dropped from find_keyring_by_name() as it's not currently made use of (setting it to 0 disables the feature). Signed-off-by: David Howells Cc: Cc: Cc: Cc: Stephen Smalley Cc: James Morris Cc: Chris Wright Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- security/keys/process_keys.c | 142 +++++++++++++++++++++++++------------------ 1 file changed, 83 insertions(+), 59 deletions(-) (limited to 'security/keys/process_keys.c') diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c index c886a2bb792..5be6d018759 100644 --- a/security/keys/process_keys.c +++ b/security/keys/process_keys.c @@ -1,6 +1,6 @@ -/* process_keys.c: management of a process's keyrings +/* Management of a process's keyrings * - * Copyright (C) 2004-5 Red Hat, Inc. All Rights Reserved. + * Copyright (C) 2004-2005, 2008 Red Hat, Inc. All Rights Reserved. * Written by David Howells (dhowells@redhat.com) * * This program is free software; you can redistribute it and/or @@ -23,6 +23,9 @@ /* session keyring create vs join semaphore */ static DEFINE_MUTEX(key_session_mutex); +/* user keyring creation semaphore */ +static DEFINE_MUTEX(key_user_keyring_mutex); + /* the root user's tracking struct */ struct key_user root_key_user = { .usage = ATOMIC_INIT(3), @@ -33,78 +36,84 @@ struct key_user root_key_user = { .uid = 0, }; -/* the root user's UID keyring */ -struct key root_user_keyring = { - .usage = ATOMIC_INIT(1), - .serial = 2, - .type = &key_type_keyring, - .user = &root_key_user, - .sem = __RWSEM_INITIALIZER(root_user_keyring.sem), - .perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_ALL, - .flags = 1 << KEY_FLAG_INSTANTIATED, - .description = "_uid.0", -#ifdef KEY_DEBUGGING - .magic = KEY_DEBUG_MAGIC, -#endif -}; - -/* the root user's default session keyring */ -struct key root_session_keyring = { - .usage = ATOMIC_INIT(1), - .serial = 1, - .type = &key_type_keyring, - .user = &root_key_user, - .sem = __RWSEM_INITIALIZER(root_session_keyring.sem), - .perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_ALL, - .flags = 1 << KEY_FLAG_INSTANTIATED, - .description = "_uid_ses.0", -#ifdef KEY_DEBUGGING - .magic = KEY_DEBUG_MAGIC, -#endif -}; - /*****************************************************************************/ /* - * allocate the keyrings to be associated with a UID + * install user and user session keyrings for a particular UID */ -int alloc_uid_keyring(struct user_struct *user, - struct task_struct *ctx) +static int install_user_keyrings(struct task_struct *tsk) { + struct user_struct *user = tsk->user; struct key *uid_keyring, *session_keyring; char buf[20]; int ret; - /* concoct a default session keyring */ - sprintf(buf, "_uid_ses.%u", user->uid); + kenter("%p{%u}", user, user->uid); - session_keyring = keyring_alloc(buf, user->uid, (gid_t) -1, ctx, - KEY_ALLOC_IN_QUOTA, NULL); - if (IS_ERR(session_keyring)) { - ret = PTR_ERR(session_keyring); - goto error; + if (user->uid_keyring) { + kleave(" = 0 [exist]"); + return 0; } - /* and a UID specific keyring, pointed to by the default session - * keyring */ - sprintf(buf, "_uid.%u", user->uid); + mutex_lock(&key_user_keyring_mutex); + ret = 0; - uid_keyring = keyring_alloc(buf, user->uid, (gid_t) -1, ctx, - KEY_ALLOC_IN_QUOTA, session_keyring); - if (IS_ERR(uid_keyring)) { - key_put(session_keyring); - ret = PTR_ERR(uid_keyring); - goto error; + if (!user->uid_keyring) { + /* get the UID-specific keyring + * - there may be one in existence already as it may have been + * pinned by a session, but the user_struct pointing to it + * may have been destroyed by setuid */ + sprintf(buf, "_uid.%u", user->uid); + + 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, + NULL); + if (IS_ERR(uid_keyring)) { + ret = PTR_ERR(uid_keyring); + goto error; + } + } + + /* get a default session keyring (which might also exist + * already) */ + sprintf(buf, "_uid_ses.%u", user->uid); + + session_keyring = find_keyring_by_name(buf, true); + if (IS_ERR(session_keyring)) { + session_keyring = + keyring_alloc(buf, user->uid, (gid_t) -1, + tsk, KEY_ALLOC_IN_QUOTA, NULL); + if (IS_ERR(session_keyring)) { + ret = PTR_ERR(session_keyring); + goto error_release; + } + + /* we install a link from the user session keyring to + * the user keyring */ + ret = key_link(session_keyring, uid_keyring); + if (ret < 0) + goto error_release_both; + } + + /* install the keyrings */ + user->uid_keyring = uid_keyring; + user->session_keyring = session_keyring; } - /* install the keyrings */ - user->uid_keyring = uid_keyring; - user->session_keyring = session_keyring; - ret = 0; + mutex_unlock(&key_user_keyring_mutex); + kleave(" = 0"); + return 0; +error_release_both: + key_put(session_keyring); +error_release: + key_put(uid_keyring); error: + mutex_unlock(&key_user_keyring_mutex); + kleave(" = %d", ret); return ret; - -} /* end alloc_uid_keyring() */ +} /*****************************************************************************/ /* @@ -481,7 +490,7 @@ key_ref_t search_process_keyrings(struct key_type *type, } } /* or search the user-session keyring */ - else { + else if (context->user->session_keyring) { key_ref = keyring_search_aux( make_key_ref(context->user->session_keyring, 1), context, type, description, match); @@ -614,6 +623,9 @@ key_ref_t lookup_user_key(struct task_struct *context, key_serial_t id, if (!context->signal->session_keyring) { /* always install a session keyring upon access if one * doesn't exist yet */ + ret = install_user_keyrings(context); + if (ret < 0) + goto error; ret = install_session_keyring( context, context->user->session_keyring); if (ret < 0) @@ -628,12 +640,24 @@ key_ref_t lookup_user_key(struct task_struct *context, key_serial_t id, break; case KEY_SPEC_USER_KEYRING: + if (!context->user->uid_keyring) { + ret = install_user_keyrings(context); + if (ret < 0) + goto error; + } + key = context->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 (ret < 0) + goto error; + } + key = context->user->session_keyring; atomic_inc(&key->usage); key_ref = make_key_ref(key, 1); @@ -744,7 +768,7 @@ long join_session_keyring(const char *name) mutex_lock(&key_session_mutex); /* look for an existing keyring of this name */ - keyring = find_keyring_by_name(name, 0); + 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, -- cgit v1.2.3