/* Management of a process's keyrings
 *
 * 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
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/keyctl.h>
#include <linux/fs.h>
#include <linux/err.h>
#include <linux/mutex.h>
#include <linux/user_namespace.h>
#include <asm/uaccess.h>
#include "internal.h"

/* 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),
        .cons_lock      = __MUTEX_INITIALIZER(root_key_user.cons_lock),
        .lock           = __SPIN_LOCK_UNLOCKED(root_key_user.lock),
        .nkeys          = ATOMIC_INIT(2),
        .nikeys         = ATOMIC_INIT(2),
        .uid            = 0,
        .user_ns        = &init_user_ns,
};

/*****************************************************************************/
/*
 * install user and user session keyrings for a particular UID
 */
int install_user_keyrings(void)
{
        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) {
                kleave(" = 0 [exist]");
                return 0;
        }

        mutex_lock(&key_user_keyring_mutex);
        ret = 0;

        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,
                                                    cred, 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,
                                              cred, 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;
}

/*
 * install a fresh thread keyring directly to new credentials
 */
int install_thread_keyring_to_cred(struct cred *new)
{
        struct key *keyring;

        keyring = keyring_alloc("_tid", new->uid, new->gid, new,
                                KEY_ALLOC_QUOTA_OVERRUN, NULL);
        if (IS_ERR(keyring))
                return PTR_ERR(keyring);

        new->thread_keyring = keyring;
        return 0;
}

/*
 * install a fresh thread keyring, discarding the old one
 */
static int install_thread_keyring(void)
{
        struct cred *new;
        int ret;

        new = prepare_creds();
        if (!new)
                return -ENOMEM;

        BUG_ON(new->thread_keyring);

        ret = install_thread_keyring_to_cred(new);
        if (ret < 0) {
                abort_creds(new);
                return ret;
        }

        return commit_creds(new);
}

/*
 * 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;

        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;
}

/*
 * make sure a process keyring is installed
 * - we
 */
static int install_process_keyring(void)
{
        struct cred *new;
        int ret;

        new = prepare_creds();
        if (!new)
                return -ENOMEM;

        ret = install_process_keyring_to_cred(new);
        if (ret < 0) {
                abort_creds(new);
                return ret != -EEXIST ?: 0;
        }

        return commit_creds(new);
}

/*
 * install a session keyring directly to a credentials struct
 */
static int install_session_keyring_to_cred(struct cred *cred,
                                           struct key *keyring)
{
        unsigned long flags;
        struct key *old;

        might_sleep();

        /* create an empty session keyring */
        if (!keyring) {
                flags = KEY_ALLOC_QUOTA_OVERRUN;
                if (cred->tgcred->session_keyring)
                        flags = KEY_ALLOC_IN_QUOTA;

                keyring = keyring_alloc("_ses", cred->uid, cred->gid,
                                        cred, flags, NULL);
                if (IS_ERR(keyring))
                        return PTR_ERR(keyring);
        } else {
                atomic_inc(&keyring->usage);
        }

        /* install the keyring */
        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 */
        if (old) {
                synchronize_rcu();
                key_put(old);
        }

        return 0;
}

/*
 * 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 key *keyring)
{
        struct cred *new;
        int ret;

        new = prepare_creds();
        if (!new)
                return -ENOMEM;

        ret = install_session_keyring_to_cred(new, NULL);
        if (ret < 0) {
                abort_creds(new);
                return ret;
        }

        return commit_creds(new);
}

/*****************************************************************************/
/*
 * the filesystem user ID changed
 */
void key_fsuid_changed(struct task_struct *tsk)
{
        /* update the ownership of the thread keyring */
        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() */

/*****************************************************************************/
/*
 * the filesystem group ID changed
 */
void key_fsgid_changed(struct task_struct *tsk)
{
        /* update the ownership of the thread keyring */
        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() */

/*****************************************************************************/
/*
 * search the process keyrings for the first matching key
 * - we use the supplied match function to see if the description (or other
 *   feature of interest) matches
 * - we return -EAGAIN if we didn't find any matching key
 * - we return -ENOKEY if we found only negative matching keys
 */
key_ref_t search_process_keyrings(struct key_type *type,
                                  const void *description,
                                  key_match_func_t match,
                                  const struct cred *cred)
{
        struct request_key_auth *rka;
        key_ref_t key_ref, ret, err;

        might_sleep();

        /* 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
         * none of the keyrings were searchable
         *
         * in terms of priority: success > -ENOKEY > -EAGAIN > other error
         */
        key_ref = NULL;
        ret = NULL;
        err = ERR_PTR(-EAGAIN);

        /* search the thread keyring first */
        if (cred->thread_keyring) {
                key_ref = keyring_search_aux(
                        make_key_ref(cred->thread_keyring, 1),
                        cred, type, description, match);
                if (!IS_ERR(key_ref))
                        goto found;

                switch (PTR_ERR(key_ref)) {
                case -EAGAIN: /* no key */
                        if (ret)
                                break;
                case -ENOKEY: /* negative key */
                        ret = key_ref;
                        break;
                default:
                        err = key_ref;
                        break;
                }
        }

        /* search the process keyring second */
        if (cred->tgcred->process_keyring) {
                key_ref = keyring_search_aux(
                        make_key_ref(cred->tgcred->process_keyring, 1),
                        cred, type, description, match);
                if (!IS_ERR(key_ref))
                        goto found;

                switch (PTR_ERR(key_ref)) {
                case -EAGAIN: /* no key */
                        if (ret)
                                break;
                case -ENOKEY: /* negative key */
                        ret = key_ref;
                        break;
                default:
                        err = key_ref;
                        break;
                }
        }

        /* search the session keyring */
        if (cred->tgcred->session_keyring) {
                rcu_read_lock();
                key_ref = keyring_search_aux(
                        make_key_ref(rcu_dereference(
                                             cred->tgcred->session_keyring),
                                     1),
                        cred, type, description, match);
                rcu_read_unlock();

                if (!IS_ERR(key_ref))
                        goto found;

                switch (PTR_ERR(key_ref)) {
                case -EAGAIN: /* no key */
                        if (ret)
                                break;
                case -ENOKEY: /* negative key */
                        ret = key_ref;
                        break;
                default:
                        err = key_ref;
                        break;
                }
        }
        /* or search the user-session keyring */
        else if (cred->user->session_keyring) {
                key_ref = keyring_search_aux(
                        make_key_ref(cred->user->session_keyring, 1),
                        cred, type, description, match);
                if (!IS_ERR(key_ref))
                        goto found;

                switch (PTR_ERR(key_ref)) {
                case -EAGAIN: /* no key */
                        if (ret)
                                break;
                case -ENOKEY: /* negative key */
                        ret = key_ref;
                        break;
                default:
                        err = key_ref;
                        break;
                }
        }

        /* if this process has an instantiation authorisation key, then we also
         * search the keyrings of the process mentioned there
         * - we don't permit access to request_key auth keys via this method
         */
        if (cred->request_key_auth &&
            cred == current_cred() &&
            type != &key_type_request_key_auth
            ) {
                /* defend against the auth key being revoked */
                down_read(&cred->request_key_auth->sem);

                if (key_validate(cred->request_key_auth) == 0) {
                        rka = cred->request_key_auth->payload.data;

                        key_ref = search_process_keyrings(type, description,
                                                          match, rka->cred);

                        up_read(&cred->request_key_auth->sem);

                        if (!IS_ERR(key_ref))
                                goto found;

                        switch (PTR_ERR(key_ref)) {
                        case -EAGAIN: /* no key */
                                if (ret)
                                        break;
                        case -ENOKEY: /* negative key */
                                ret = key_ref;
                                break;
                        default:
                                err = key_ref;
                                break;
                        }
                } else {
                        up_read(&cred->request_key_auth->sem);
                }
        }

        /* no key - decide on the error we're going to go for */
        key_ref = ret ? ret : err;

found:
        return key_ref;

} /* end search_process_keyrings() */

/*****************************************************************************/
/*
 * see if the key we're looking at is the target key
 */
static int lookup_user_key_possessed(const struct key *key, const void *target)
{
        return key == target;

} /* end lookup_user_key_possessed() */

/*****************************************************************************/
/*
 * lookup a key given a key ID from userspace with a given permissions mask
 * - don't create special keyrings unless so requested
 * - partially constructed keys aren't found unless requested
 */
key_ref_t lookup_user_key(key_serial_t id, int create, int partial,
                          key_perm_t perm)
{
        struct request_key_auth *rka;
        const 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) {
        case KEY_SPEC_THREAD_KEYRING:
                if (!cred->thread_keyring) {
                        if (!create)
                                goto error;

                        ret = install_thread_keyring();
                        if (ret < 0) {
                                key = ERR_PTR(ret);
                                goto error;
                        }
                        goto reget_creds;
                }

                key = cred->thread_keyring;
                atomic_inc(&key->usage);
                key_ref = make_key_ref(key, 1);
                break;

        case KEY_SPEC_PROCESS_KEYRING:
                if (!cred->tgcred->process_keyring) {
                        if (!create)
                                goto error;

                        ret = install_process_keyring();
                        if (ret < 0) {
                                key = ERR_PTR(ret);
                                goto error;
                        }
                        goto reget_creds;
                }

                key = cred->tgcred->process_keyring;
                atomic_inc(&key->usage);
                key_ref = make_key_ref(key, 1);
                break;

        case KEY_SPEC_SESSION_KEYRING:
                if (!cred->tgcred->session_keyring) {
                        /* always install a session keyring upon access if one
                         * doesn't exist yet */
                        ret = install_user_keyrings();
                        if (ret < 0)
                                goto error;
                        ret = install_session_keyring(
                                cred->user->session_keyring);

                        if (ret < 0)
                                goto error;
                        goto reget_creds;
                }

                rcu_read_lock();
                key = rcu_dereference(cred->tgcred->session_keyring);
                atomic_inc(&key->usage);
                rcu_read_unlock();
                key_ref = make_key_ref(key, 1);
                break;

        case KEY_SPEC_USER_KEYRING:
                if (!cred->user->uid_keyring) {
                        ret = install_user_keyrings();
                        if (ret < 0)
                                goto error;
                }

                key = cred->user->uid_keyring;
                atomic_inc(&key->usage);
                key_ref = make_key_ref(key, 1);
                break;

        case KEY_SPEC_USER_SESSION_KEYRING:
                if (!cred->user->session_keyring) {
                        ret = install_user_keyrings();
                        if (ret < 0)
                                goto error;
                }

                key = cred->user->session_keyring;
                atomic_inc(&key->usage);
                key_ref = make_key_ref(key, 1);
                break;

        case KEY_SPEC_GROUP_KEYRING:
                /* group keyrings are not yet supported */
                key = ERR_PTR(-EINVAL);
                goto error;

        case KEY_SPEC_REQKEY_AUTH_KEY:
                key = cred->request_key_auth;
                if (!key)
                        goto error;

                atomic_inc(&key->usage);
                key_ref = make_key_ref(key, 1);
                break;

        case KEY_SPEC_REQUESTOR_KEYRING:
                if (!cred->request_key_auth)
                        goto error;

                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 = cred->request_key_auth->payload.data;
                        key = rka->dest_keyring;
                        atomic_inc(&key->usage);
                }
                up_read(&cred->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)
                        goto error;

                key = key_lookup(id);
                if (IS_ERR(key)) {
                        key_ref = ERR_CAST(key);
                        goto error;
                }

                key_ref = make_key_ref(key, 0);

                /* check to see if we possess the key */
                skey_ref = search_process_keyrings(key->type, key,
                                                   lookup_user_key_possessed,
                                                   cred);

                if (!IS_ERR(skey_ref)) {
                        key_put(key);
                        key_ref = skey_ref;
                }

                break;
        }

        if (!partial) {
                ret = wait_for_key_construction(key, true);
                switch (ret) {
                case -ERESTARTSYS:
                        goto invalid_key;
                default:
                        if (perm)
                                goto invalid_key;
                case 0:
                        break;
                }
        } else if (perm) {
                ret = key_validate(key);
                if (ret < 0)
                        goto invalid_key;
        }

        ret = -EIO;
        if (!partial && !test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
                goto invalid_key;

        /* check the permissions */
        ret = key_task_permission(key_ref, cred, perm);
        if (ret < 0)
                goto invalid_key;

error:
        put_cred(cred);
        return key_ref;

invalid_key:
        key_ref_put(key_ref);
        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() */

/*****************************************************************************/
/*
 * join the named keyring as the session keyring if possible, or attempt to
 * create a new one of that name if not
 * - if the name is NULL, an empty anonymous keyring is installed instead
 * - named session keyring joining is done with a semaphore held
 */
long join_session_keyring(const char *name)
{
        const struct cred *old;
        struct cred *new;
        struct key *keyring;
        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_to_cred(new, NULL);
                if (ret < 0)
                        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 */
        mutex_lock(&key_session_mutex);

        /* look for an existing keyring of this 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, 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)) {
                ret = PTR_ERR(keyring);
                goto error2;
        }

        /* we've got a keyring - now to install it */
        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;
}