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keys: don't generate user and user session keyrings unless they're accessed

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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 <dhowells@redhat.com>
Cc: <kwc@citi.umich.edu>
Cc: <arunsr@cse.iitk.ac.in>
Cc: <dwalsh@redhat.com>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: James Morris <jmorris@namei.org>
Cc: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Howells
2008-04-29 01:01:31 -07:00
committed by Linus Torvalds
parent 6b79ccb514
commit 69664cf16a
7 changed files with 99 additions and 148 deletions
Download Patch File Download Diff File Expand all files Collapse all files

148
security/keys/process_keys.c
View File

@@ -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);
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;
}
/* install the keyrings */
user->uid_keyring = uid_keyring;
user->session_keyring = session_keyring;
mutex_lock(&key_user_keyring_mutex);
ret = 0;
error:
return ret;
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);
} /* end alloc_uid_keyring() */
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;
}
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;
}
/*****************************************************************************/
/*
@@ -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,