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![David Howells](/assets/img/avatar_default.png)
This fixes five bugs in the key management syscall interface: (1) add_key() returns 0 rather than EINVAL if the key type is "". Checking the key type isn't "" should be left to lookup_user_key(). (2) request_key() returns ENOKEY rather than EPERM if the key type begins with a ".". lookup_user_key() can't do this because internal key types begin with a ".". (3) Key revocation always returns 0, even if it fails. (4) Key read can return EAGAIN rather than EACCES under some circumstances. A key is permitted to by read by a process if it doesn't grant read access, but it does grant search access and it is in the process's keyrings. That search returns EAGAIN if it fails, and this needs translating to EACCES. (5) request_key() never adds the new key to the destination keyring if one is supplied. The wrong macro was being used to test for an error condition: PTR_ERR() will always return true, whether or not there's an error; this should've been IS_ERR(). Signed-Off-By: David Howells <dhowells@redhat.com> Signed-Off-By: Linus Torvalds <torvalds@osdl.org>
474 lines
12 KiB
C
474 lines
12 KiB
C
/* request_key.c: request a key from userspace
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*
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* Copyright (C) 2004-5 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/module.h>
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#include <linux/sched.h>
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#include <linux/kmod.h>
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#include <linux/err.h>
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#include <linux/keyctl.h>
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#include "internal.h"
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struct key_construction {
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struct list_head link; /* link in construction queue */
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struct key *key; /* key being constructed */
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};
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/* when waiting for someone else's keys, you get added to this */
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DECLARE_WAIT_QUEUE_HEAD(request_key_conswq);
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/*****************************************************************************/
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/*
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* request userspace finish the construction of a key
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* - execute "/sbin/request-key <op> <key> <uid> <gid> <keyring> <keyring> <keyring> <info>"
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*/
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static int call_request_key(struct key *key,
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const char *op,
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const char *callout_info)
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{
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struct task_struct *tsk = current;
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key_serial_t prkey, sskey;
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struct key *session_keyring, *rkakey;
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char *argv[10], *envp[3], uid_str[12], gid_str[12];
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char key_str[12], keyring_str[3][12];
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int ret, i;
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kenter("{%d},%s,%s", key->serial, op, callout_info);
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/* generate a new session keyring with an auth key in it */
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session_keyring = request_key_auth_new(key, &rkakey);
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if (IS_ERR(session_keyring)) {
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ret = PTR_ERR(session_keyring);
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goto error;
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}
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/* record the UID and GID */
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sprintf(uid_str, "%d", current->fsuid);
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sprintf(gid_str, "%d", current->fsgid);
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/* we say which key is under construction */
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sprintf(key_str, "%d", key->serial);
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/* we specify the process's default keyrings */
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sprintf(keyring_str[0], "%d",
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tsk->thread_keyring ? tsk->thread_keyring->serial : 0);
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prkey = 0;
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if (tsk->signal->process_keyring)
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prkey = tsk->signal->process_keyring->serial;
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sprintf(keyring_str[1], "%d", prkey);
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if (tsk->signal->session_keyring) {
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rcu_read_lock();
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sskey = rcu_dereference(tsk->signal->session_keyring)->serial;
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rcu_read_unlock();
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}
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else {
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sskey = tsk->user->session_keyring->serial;
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}
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sprintf(keyring_str[2], "%d", sskey);
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/* set up a minimal environment */
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i = 0;
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envp[i++] = "HOME=/";
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envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
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envp[i] = NULL;
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/* set up the argument list */
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i = 0;
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argv[i++] = "/sbin/request-key";
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argv[i++] = (char *) op;
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argv[i++] = key_str;
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argv[i++] = uid_str;
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argv[i++] = gid_str;
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argv[i++] = keyring_str[0];
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argv[i++] = keyring_str[1];
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argv[i++] = keyring_str[2];
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argv[i++] = (char *) callout_info;
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argv[i] = NULL;
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/* do it */
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ret = call_usermodehelper_keys(argv[0], argv, envp, session_keyring, 1);
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/* dispose of the special keys */
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key_revoke(rkakey);
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key_put(rkakey);
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key_put(session_keyring);
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error:
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kleave(" = %d", ret);
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return ret;
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} /* end call_request_key() */
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/*****************************************************************************/
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/*
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* call out to userspace for the key
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* - called with the construction sem held, but the sem is dropped here
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* - we ignore program failure and go on key status instead
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*/
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static struct key *__request_key_construction(struct key_type *type,
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const char *description,
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const char *callout_info)
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{
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struct key_construction cons;
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struct timespec now;
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struct key *key;
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int ret, negated;
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kenter("%s,%s,%s", type->name, description, callout_info);
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/* create a key and add it to the queue */
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key = key_alloc(type, description,
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current->fsuid, current->fsgid, KEY_USR_ALL, 0);
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if (IS_ERR(key))
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goto alloc_failed;
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set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
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cons.key = key;
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list_add_tail(&cons.link, &key->user->consq);
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/* we drop the construction sem here on behalf of the caller */
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up_write(&key_construction_sem);
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/* make the call */
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ret = call_request_key(key, "create", callout_info);
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if (ret < 0)
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goto request_failed;
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/* if the key wasn't instantiated, then we want to give an error */
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ret = -ENOKEY;
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if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
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goto request_failed;
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down_write(&key_construction_sem);
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list_del(&cons.link);
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up_write(&key_construction_sem);
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/* also give an error if the key was negatively instantiated */
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check_not_negative:
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if (test_bit(KEY_FLAG_NEGATIVE, &key->flags)) {
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key_put(key);
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key = ERR_PTR(-ENOKEY);
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}
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out:
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kleave(" = %p", key);
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return key;
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request_failed:
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/* it wasn't instantiated
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* - remove from construction queue
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* - mark the key as dead
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*/
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negated = 0;
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down_write(&key_construction_sem);
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list_del(&cons.link);
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/* check it didn't get instantiated between the check and the down */
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if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
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set_bit(KEY_FLAG_NEGATIVE, &key->flags);
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set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
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negated = 1;
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}
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clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
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up_write(&key_construction_sem);
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if (!negated)
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goto check_not_negative; /* surprisingly, the key got
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* instantiated */
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/* set the timeout and store in the session keyring if we can */
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now = current_kernel_time();
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key->expiry = now.tv_sec + key_negative_timeout;
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if (current->signal->session_keyring) {
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struct key *keyring;
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rcu_read_lock();
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keyring = rcu_dereference(current->signal->session_keyring);
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atomic_inc(&keyring->usage);
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rcu_read_unlock();
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key_link(keyring, key);
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key_put(keyring);
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}
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key_put(key);
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/* notify anyone who was waiting */
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wake_up_all(&request_key_conswq);
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key = ERR_PTR(ret);
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goto out;
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alloc_failed:
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up_write(&key_construction_sem);
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goto out;
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} /* end __request_key_construction() */
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/*****************************************************************************/
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/*
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* call out to userspace to request the key
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* - we check the construction queue first to see if an appropriate key is
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* already being constructed by userspace
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*/
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static struct key *request_key_construction(struct key_type *type,
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const char *description,
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struct key_user *user,
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const char *callout_info)
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{
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struct key_construction *pcons;
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struct key *key, *ckey;
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DECLARE_WAITQUEUE(myself, current);
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kenter("%s,%s,{%d},%s",
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type->name, description, user->uid, callout_info);
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/* see if there's such a key under construction already */
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down_write(&key_construction_sem);
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list_for_each_entry(pcons, &user->consq, link) {
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ckey = pcons->key;
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if (ckey->type != type)
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continue;
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if (type->match(ckey, description))
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goto found_key_under_construction;
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}
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/* see about getting userspace to construct the key */
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key = __request_key_construction(type, description, callout_info);
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error:
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kleave(" = %p", key);
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return key;
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/* someone else has the same key under construction
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* - we want to keep an eye on their key
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*/
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found_key_under_construction:
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atomic_inc(&ckey->usage);
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up_write(&key_construction_sem);
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/* wait for the key to be completed one way or another */
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add_wait_queue(&request_key_conswq, &myself);
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for (;;) {
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set_current_state(TASK_INTERRUPTIBLE);
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if (!test_bit(KEY_FLAG_USER_CONSTRUCT, &ckey->flags))
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break;
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if (signal_pending(current))
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break;
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schedule();
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}
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set_current_state(TASK_RUNNING);
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remove_wait_queue(&request_key_conswq, &myself);
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/* we'll need to search this process's keyrings to see if the key is
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* now there since we can't automatically assume it's also available
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* there */
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key_put(ckey);
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ckey = NULL;
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key = NULL; /* request a retry */
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goto error;
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} /* end request_key_construction() */
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/*****************************************************************************/
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/*
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* link a freshly minted key to an appropriate destination keyring
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*/
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static void request_key_link(struct key *key, struct key *dest_keyring)
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{
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struct task_struct *tsk = current;
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struct key *drop = NULL;
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kenter("{%d},%p", key->serial, dest_keyring);
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/* find the appropriate keyring */
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if (!dest_keyring) {
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switch (tsk->jit_keyring) {
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case KEY_REQKEY_DEFL_DEFAULT:
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case KEY_REQKEY_DEFL_THREAD_KEYRING:
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dest_keyring = tsk->thread_keyring;
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if (dest_keyring)
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break;
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case KEY_REQKEY_DEFL_PROCESS_KEYRING:
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dest_keyring = tsk->signal->process_keyring;
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if (dest_keyring)
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break;
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case KEY_REQKEY_DEFL_SESSION_KEYRING:
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rcu_read_lock();
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dest_keyring = key_get(
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rcu_dereference(tsk->signal->session_keyring));
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rcu_read_unlock();
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drop = dest_keyring;
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if (dest_keyring)
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break;
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case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
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dest_keyring = current->user->session_keyring;
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break;
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case KEY_REQKEY_DEFL_USER_KEYRING:
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dest_keyring = current->user->uid_keyring;
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break;
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case KEY_REQKEY_DEFL_GROUP_KEYRING:
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default:
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BUG();
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}
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}
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/* and attach the key to it */
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key_link(dest_keyring, key);
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key_put(drop);
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kleave("");
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} /* end request_key_link() */
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/*****************************************************************************/
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/*
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* request a key
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* - search the process's keyrings
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* - check the list of keys being created or updated
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* - call out to userspace for a key if supplementary info was provided
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* - cache the key in an appropriate keyring
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*/
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struct key *request_key_and_link(struct key_type *type,
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const char *description,
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const char *callout_info,
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struct key *dest_keyring)
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{
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struct key_user *user;
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struct key *key;
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kenter("%s,%s,%s,%p",
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type->name, description, callout_info, dest_keyring);
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/* search all the process keyrings for a key */
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key = search_process_keyrings(type, description, type->match, current);
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if (PTR_ERR(key) == -EAGAIN) {
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/* the search failed, but the keyrings were searchable, so we
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* should consult userspace if we can */
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key = ERR_PTR(-ENOKEY);
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if (!callout_info)
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goto error;
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/* - get hold of the user's construction queue */
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user = key_user_lookup(current->fsuid);
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if (!user)
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goto nomem;
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do {
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if (signal_pending(current))
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goto interrupted;
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/* ask userspace (returns NULL if it waited on a key
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* being constructed) */
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key = request_key_construction(type, description,
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user, callout_info);
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if (key)
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break;
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/* someone else made the key we want, so we need to
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* search again as it might now be available to us */
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key = search_process_keyrings(type, description,
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type->match, current);
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} while (PTR_ERR(key) == -EAGAIN);
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key_user_put(user);
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/* link the new key into the appropriate keyring */
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if (!IS_ERR(key))
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request_key_link(key, dest_keyring);
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}
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error:
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kleave(" = %p", key);
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return key;
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nomem:
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key = ERR_PTR(-ENOMEM);
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goto error;
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interrupted:
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key_user_put(user);
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key = ERR_PTR(-EINTR);
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goto error;
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} /* end request_key_and_link() */
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/*****************************************************************************/
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/*
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* request a key
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* - search the process's keyrings
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* - check the list of keys being created or updated
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* - call out to userspace for a key if supplementary info was provided
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*/
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struct key *request_key(struct key_type *type,
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const char *description,
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const char *callout_info)
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{
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return request_key_and_link(type, description, callout_info, NULL);
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} /* end request_key() */
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EXPORT_SYMBOL(request_key);
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/*****************************************************************************/
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/*
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* validate a key
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*/
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int key_validate(struct key *key)
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{
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struct timespec now;
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int ret = 0;
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if (key) {
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/* check it's still accessible */
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ret = -EKEYREVOKED;
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if (test_bit(KEY_FLAG_REVOKED, &key->flags) ||
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test_bit(KEY_FLAG_DEAD, &key->flags))
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goto error;
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/* check it hasn't expired */
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ret = 0;
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if (key->expiry) {
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now = current_kernel_time();
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if (now.tv_sec >= key->expiry)
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ret = -EKEYEXPIRED;
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}
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}
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error:
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return ret;
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} /* end key_validate() */
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EXPORT_SYMBOL(key_validate);
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