mm, oom: do not rely on TIF_MEMDIE for memory reserves access

[linux/fpc-iii.git] / security / keys / request_key.c

/* Request a key from userspace
 *
 * Copyright (C) 2004-2007 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.
 *
 * See Documentation/security/keys/request-key.rst
 */

#include <linux/module.h>
#include <linux/sched.h>
#include <linux/kmod.h>
#include <linux/err.h>
#include <linux/keyctl.h>
#include <linux/slab.h>
#include "internal.h"

#define key_negative_timeout    60      /* default timeout on a negative key's existence */

/**
 * complete_request_key - Complete the construction of a key.
 * @cons: The key construction record.
 * @error: The success or failute of the construction.
 *
 * Complete the attempt to construct a key.  The key will be negated
 * if an error is indicated.  The authorisation key will be revoked
 * unconditionally.
 */
void complete_request_key(struct key_construction *cons, int error)
{
        kenter("{%d,%d},%d", cons->key->serial, cons->authkey->serial, error);

        if (error < 0)
                key_negate_and_link(cons->key, key_negative_timeout, NULL,
                                    cons->authkey);
        else
                key_revoke(cons->authkey);

        key_put(cons->key);
        key_put(cons->authkey);
        kfree(cons);
}
EXPORT_SYMBOL(complete_request_key);

/*
 * Initialise a usermode helper that is going to have a specific session
 * keyring.
 *
 * This is called in context of freshly forked kthread before kernel_execve(),
 * so we can simply install the desired session_keyring at this point.
 */
static int umh_keys_init(struct subprocess_info *info, struct cred *cred)
{
        struct key *keyring = info->data;

        return install_session_keyring_to_cred(cred, keyring);
}

/*
 * Clean up a usermode helper with session keyring.
 */
static void umh_keys_cleanup(struct subprocess_info *info)
{
        struct key *keyring = info->data;
        key_put(keyring);
}

/*
 * Call a usermode helper with a specific session keyring.
 */
static int call_usermodehelper_keys(const char *path, char **argv, char **envp,
                                        struct key *session_keyring, int wait)
{
        struct subprocess_info *info;

        info = call_usermodehelper_setup(path, argv, envp, GFP_KERNEL,
                                          umh_keys_init, umh_keys_cleanup,
                                          session_keyring);
        if (!info)
                return -ENOMEM;

        key_get(session_keyring);
        return call_usermodehelper_exec(info, wait);
}

/*
 * Request userspace finish the construction of a key
 * - execute "/sbin/request-key <op> <key> <uid> <gid> <keyring> <keyring> <keyring>"
 */
static int call_sbin_request_key(struct key_construction *cons,
                                 const char *op,
                                 void *aux)
{
        static char const request_key[] = "/sbin/request-key";
        const struct cred *cred = current_cred();
        key_serial_t prkey, sskey;
        struct key *key = cons->key, *authkey = cons->authkey, *keyring,
                *session;
        char *argv[9], *envp[3], uid_str[12], gid_str[12];
        char key_str[12], keyring_str[3][12];
        char desc[20];
        int ret, i;

        kenter("{%d},{%d},%s", key->serial, authkey->serial, op);

        ret = install_user_keyrings();
        if (ret < 0)
                goto error_alloc;

        /* allocate a new session keyring */
        sprintf(desc, "_req.%u", key->serial);

        cred = get_current_cred();
        keyring = keyring_alloc(desc, cred->fsuid, cred->fsgid, cred,
                                KEY_POS_ALL | KEY_USR_VIEW | KEY_USR_READ,
                                KEY_ALLOC_QUOTA_OVERRUN, NULL, NULL);
        put_cred(cred);
        if (IS_ERR(keyring)) {
                ret = PTR_ERR(keyring);
                goto error_alloc;
        }

        /* attach the auth key to the session keyring */
        ret = key_link(keyring, authkey);
        if (ret < 0)
                goto error_link;

        /* record the UID and GID */
        sprintf(uid_str, "%d", from_kuid(&init_user_ns, cred->fsuid));
        sprintf(gid_str, "%d", from_kgid(&init_user_ns, cred->fsgid));

        /* we say which key is under construction */
        sprintf(key_str, "%d", key->serial);

        /* we specify the process's default keyrings */
        sprintf(keyring_str[0], "%d",
                cred->thread_keyring ? cred->thread_keyring->serial : 0);

        prkey = 0;
        if (cred->process_keyring)
                prkey = cred->process_keyring->serial;
        sprintf(keyring_str[1], "%d", prkey);

        rcu_read_lock();
        session = rcu_dereference(cred->session_keyring);
        if (!session)
                session = cred->user->session_keyring;
        sskey = session->serial;
        rcu_read_unlock();

        sprintf(keyring_str[2], "%d", sskey);

        /* set up a minimal environment */
        i = 0;
        envp[i++] = "HOME=/";
        envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
        envp[i] = NULL;

        /* set up the argument list */
        i = 0;
        argv[i++] = (char *)request_key;
        argv[i++] = (char *) op;
        argv[i++] = key_str;
        argv[i++] = uid_str;
        argv[i++] = gid_str;
        argv[i++] = keyring_str[0];
        argv[i++] = keyring_str[1];
        argv[i++] = keyring_str[2];
        argv[i] = NULL;

        /* do it */
        ret = call_usermodehelper_keys(request_key, argv, envp, keyring,
                                       UMH_WAIT_PROC);
        kdebug("usermode -> 0x%x", ret);
        if (ret >= 0) {
                /* ret is the exit/wait code */
                if (test_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags) ||
                    key_validate(key) < 0)
                        ret = -ENOKEY;
                else
                        /* ignore any errors from userspace if the key was
                         * instantiated */
                        ret = 0;
        }

error_link:
        key_put(keyring);

error_alloc:
        complete_request_key(cons, ret);
        kleave(" = %d", ret);
        return ret;
}

/*
 * Call out to userspace for key construction.
 *
 * Program failure is ignored in favour of key status.
 */
static int construct_key(struct key *key, const void *callout_info,
                         size_t callout_len, void *aux,
                         struct key *dest_keyring)
{
        struct key_construction *cons;
        request_key_actor_t actor;
        struct key *authkey;
        int ret;

        kenter("%d,%p,%zu,%p", key->serial, callout_info, callout_len, aux);

        cons = kmalloc(sizeof(*cons), GFP_KERNEL);
        if (!cons)
                return -ENOMEM;

        /* allocate an authorisation key */
        authkey = request_key_auth_new(key, callout_info, callout_len,
                                       dest_keyring);
        if (IS_ERR(authkey)) {
                kfree(cons);
                ret = PTR_ERR(authkey);
                authkey = NULL;
        } else {
                cons->authkey = key_get(authkey);
                cons->key = key_get(key);

                /* make the call */
                actor = call_sbin_request_key;
                if (key->type->request_key)
                        actor = key->type->request_key;

                ret = actor(cons, "create", aux);

                /* check that the actor called complete_request_key() prior to
                 * returning an error */
                WARN_ON(ret < 0 &&
                        !test_bit(KEY_FLAG_REVOKED, &authkey->flags));
                key_put(authkey);
        }

        kleave(" = %d", ret);
        return ret;
}

/*
 * Get the appropriate destination keyring for the request.
 *
 * The keyring selected is returned with an extra reference upon it which the
 * caller must release.
 */
static void construct_get_dest_keyring(struct key **_dest_keyring)
{
        struct request_key_auth *rka;
        const struct cred *cred = current_cred();
        struct key *dest_keyring = *_dest_keyring, *authkey;

        kenter("%p", dest_keyring);

        /* find the appropriate keyring */
        if (dest_keyring) {
                /* the caller supplied one */
                key_get(dest_keyring);
        } else {
                /* use a default keyring; falling through the cases until we
                 * find one that we actually have */
                switch (cred->jit_keyring) {
                case KEY_REQKEY_DEFL_DEFAULT:
                case KEY_REQKEY_DEFL_REQUESTOR_KEYRING:
                        if (cred->request_key_auth) {
                                authkey = cred->request_key_auth;
                                down_read(&authkey->sem);
                                rka = authkey->payload.data[0];
                                if (!test_bit(KEY_FLAG_REVOKED,
                                              &authkey->flags))
                                        dest_keyring =
                                                key_get(rka->dest_keyring);
                                up_read(&authkey->sem);
                                if (dest_keyring)
                                        break;
                        }

                case KEY_REQKEY_DEFL_THREAD_KEYRING:
                        dest_keyring = key_get(cred->thread_keyring);
                        if (dest_keyring)
                                break;

                case KEY_REQKEY_DEFL_PROCESS_KEYRING:
                        dest_keyring = key_get(cred->process_keyring);
                        if (dest_keyring)
                                break;

                case KEY_REQKEY_DEFL_SESSION_KEYRING:
                        rcu_read_lock();
                        dest_keyring = key_get(
                                rcu_dereference(cred->session_keyring));
                        rcu_read_unlock();

                        if (dest_keyring)
                                break;

                case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
                        dest_keyring =
                                key_get(cred->user->session_keyring);
                        break;

                case KEY_REQKEY_DEFL_USER_KEYRING:
                        dest_keyring = key_get(cred->user->uid_keyring);
                        break;

                case KEY_REQKEY_DEFL_GROUP_KEYRING:
                default:
                        BUG();
                }
        }

        *_dest_keyring = dest_keyring;
        kleave(" [dk %d]", key_serial(dest_keyring));
        return;
}

/*
 * Allocate a new key in under-construction state and attempt to link it in to
 * the requested keyring.
 *
 * May return a key that's already under construction instead if there was a
 * race between two thread calling request_key().
 */
static int construct_alloc_key(struct keyring_search_context *ctx,
                               struct key *dest_keyring,
                               unsigned long flags,
                               struct key_user *user,
                               struct key **_key)
{
        struct assoc_array_edit *edit;
        struct key *key;
        key_perm_t perm;
        key_ref_t key_ref;
        int ret;

        kenter("%s,%s,,,",
               ctx->index_key.type->name, ctx->index_key.description);

        *_key = NULL;
        mutex_lock(&user->cons_lock);

        perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
        perm |= KEY_USR_VIEW;
        if (ctx->index_key.type->read)
                perm |= KEY_POS_READ;
        if (ctx->index_key.type == &key_type_keyring ||
            ctx->index_key.type->update)
                perm |= KEY_POS_WRITE;

        key = key_alloc(ctx->index_key.type, ctx->index_key.description,
                        ctx->cred->fsuid, ctx->cred->fsgid, ctx->cred,
                        perm, flags, NULL);
        if (IS_ERR(key))
                goto alloc_failed;

        set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);

        if (dest_keyring) {
                ret = __key_link_begin(dest_keyring, &ctx->index_key, &edit);
                if (ret < 0)
                        goto link_prealloc_failed;
        }

        /* attach the key to the destination keyring under lock, but we do need
         * to do another check just in case someone beat us to it whilst we
         * waited for locks */
        mutex_lock(&key_construction_mutex);

        key_ref = search_process_keyrings(ctx);
        if (!IS_ERR(key_ref))
                goto key_already_present;

        if (dest_keyring)
                __key_link(key, &edit);

        mutex_unlock(&key_construction_mutex);
        if (dest_keyring)
                __key_link_end(dest_keyring, &ctx->index_key, edit);
        mutex_unlock(&user->cons_lock);
        *_key = key;
        kleave(" = 0 [%d]", key_serial(key));
        return 0;

        /* the key is now present - we tell the caller that we found it by
         * returning -EINPROGRESS  */
key_already_present:
        key_put(key);
        mutex_unlock(&key_construction_mutex);
        key = key_ref_to_ptr(key_ref);
        if (dest_keyring) {
                ret = __key_link_check_live_key(dest_keyring, key);
                if (ret == 0)
                        __key_link(key, &edit);
                __key_link_end(dest_keyring, &ctx->index_key, edit);
                if (ret < 0)
                        goto link_check_failed;
        }
        mutex_unlock(&user->cons_lock);
        *_key = key;
        kleave(" = -EINPROGRESS [%d]", key_serial(key));
        return -EINPROGRESS;

link_check_failed:
        mutex_unlock(&user->cons_lock);
        key_put(key);
        kleave(" = %d [linkcheck]", ret);
        return ret;

link_prealloc_failed:
        mutex_unlock(&user->cons_lock);
        key_put(key);
        kleave(" = %d [prelink]", ret);
        return ret;

alloc_failed:
        mutex_unlock(&user->cons_lock);
        kleave(" = %ld", PTR_ERR(key));
        return PTR_ERR(key);
}

/*
 * Commence key construction.
 */
static struct key *construct_key_and_link(struct keyring_search_context *ctx,
                                          const char *callout_info,
                                          size_t callout_len,
                                          void *aux,
                                          struct key *dest_keyring,
                                          unsigned long flags)
{
        struct key_user *user;
        struct key *key;
        int ret;

        kenter("");

        if (ctx->index_key.type == &key_type_keyring)
                return ERR_PTR(-EPERM);

        user = key_user_lookup(current_fsuid());
        if (!user)
                return ERR_PTR(-ENOMEM);

        construct_get_dest_keyring(&dest_keyring);

        ret = construct_alloc_key(ctx, dest_keyring, flags, user, &key);
        key_user_put(user);

        if (ret == 0) {
                ret = construct_key(key, callout_info, callout_len, aux,
                                    dest_keyring);
                if (ret < 0) {
                        kdebug("cons failed");
                        goto construction_failed;
                }
        } else if (ret == -EINPROGRESS) {
                ret = 0;
        } else {
                goto couldnt_alloc_key;
        }

        key_put(dest_keyring);
        kleave(" = key %d", key_serial(key));
        return key;

construction_failed:
        key_negate_and_link(key, key_negative_timeout, NULL, NULL);
        key_put(key);
couldnt_alloc_key:
        key_put(dest_keyring);
        kleave(" = %d", ret);
        return ERR_PTR(ret);
}

/**
 * request_key_and_link - Request a key and cache it in a keyring.
 * @type: The type of key we want.
 * @description: The searchable description of the key.
 * @callout_info: The data to pass to the instantiation upcall (or NULL).
 * @callout_len: The length of callout_info.
 * @aux: Auxiliary data for the upcall.
 * @dest_keyring: Where to cache the key.
 * @flags: Flags to key_alloc().
 *
 * A key matching the specified criteria is searched for in the process's
 * keyrings and returned with its usage count incremented if found.  Otherwise,
 * if callout_info is not NULL, a key will be allocated and some service
 * (probably in userspace) will be asked to instantiate it.
 *
 * If successfully found or created, the key will be linked to the destination
 * keyring if one is provided.
 *
 * Returns a pointer to the key if successful; -EACCES, -ENOKEY, -EKEYREVOKED
 * or -EKEYEXPIRED if an inaccessible, negative, revoked or expired key was
 * found; -ENOKEY if no key was found and no @callout_info was given; -EDQUOT
 * if insufficient key quota was available to create a new key; or -ENOMEM if
 * insufficient memory was available.
 *
 * If the returned key was created, then it may still be under construction,
 * and wait_for_key_construction() should be used to wait for that to complete.
 */
struct key *request_key_and_link(struct key_type *type,
                                 const char *description,
                                 const void *callout_info,
                                 size_t callout_len,
                                 void *aux,
                                 struct key *dest_keyring,
                                 unsigned long flags)
{
        struct keyring_search_context ctx = {
                .index_key.type         = type,
                .index_key.description  = description,
                .cred                   = current_cred(),
                .match_data.cmp         = key_default_cmp,
                .match_data.raw_data    = description,
                .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
                .flags                  = (KEYRING_SEARCH_DO_STATE_CHECK |
                                           KEYRING_SEARCH_SKIP_EXPIRED),
        };
        struct key *key;
        key_ref_t key_ref;
        int ret;

        kenter("%s,%s,%p,%zu,%p,%p,%lx",
               ctx.index_key.type->name, ctx.index_key.description,
               callout_info, callout_len, aux, dest_keyring, flags);

        if (type->match_preparse) {
                ret = type->match_preparse(&ctx.match_data);
                if (ret < 0) {
                        key = ERR_PTR(ret);
                        goto error;
                }
        }

        /* search all the process keyrings for a key */
        key_ref = search_process_keyrings(&ctx);

        if (!IS_ERR(key_ref)) {
                key = key_ref_to_ptr(key_ref);
                if (dest_keyring) {
                        construct_get_dest_keyring(&dest_keyring);
                        ret = key_link(dest_keyring, key);
                        key_put(dest_keyring);
                        if (ret < 0) {
                                key_put(key);
                                key = ERR_PTR(ret);
                                goto error_free;
                        }
                }
        } else if (PTR_ERR(key_ref) != -EAGAIN) {
                key = ERR_CAST(key_ref);
        } else  {
                /* the search failed, but the keyrings were searchable, so we
                 * should consult userspace if we can */
                key = ERR_PTR(-ENOKEY);
                if (!callout_info)
                        goto error_free;

                key = construct_key_and_link(&ctx, callout_info, callout_len,
                                             aux, dest_keyring, flags);
        }

error_free:
        if (type->match_free)
                type->match_free(&ctx.match_data);
error:
        kleave(" = %p", key);
        return key;
}

/**
 * wait_for_key_construction - Wait for construction of a key to complete
 * @key: The key being waited for.
 * @intr: Whether to wait interruptibly.
 *
 * Wait for a key to finish being constructed.
 *
 * Returns 0 if successful; -ERESTARTSYS if the wait was interrupted; -ENOKEY
 * if the key was negated; or -EKEYREVOKED or -EKEYEXPIRED if the key was
 * revoked or expired.
 */
int wait_for_key_construction(struct key *key, bool intr)
{
        int ret;

        ret = wait_on_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT,
                          intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
        if (ret)
                return -ERESTARTSYS;
        if (test_bit(KEY_FLAG_NEGATIVE, &key->flags)) {
                smp_rmb();
                return key->reject_error;
        }
        return key_validate(key);
}
EXPORT_SYMBOL(wait_for_key_construction);

/**
 * request_key - Request a key and wait for construction
 * @type: Type of key.
 * @description: The searchable description of the key.
 * @callout_info: The data to pass to the instantiation upcall (or NULL).
 *
 * As for request_key_and_link() except that it does not add the returned key
 * to a keyring if found, new keys are always allocated in the user's quota,
 * the callout_info must be a NUL-terminated string and no auxiliary data can
 * be passed.
 *
 * Furthermore, it then works as wait_for_key_construction() to wait for the
 * completion of keys undergoing construction with a non-interruptible wait.
 */
struct key *request_key(struct key_type *type,
                        const char *description,
                        const char *callout_info)
{
        struct key *key;
        size_t callout_len = 0;
        int ret;

        if (callout_info)
                callout_len = strlen(callout_info);
        key = request_key_and_link(type, description, callout_info, callout_len,
                                   NULL, NULL, KEY_ALLOC_IN_QUOTA);
        if (!IS_ERR(key)) {
                ret = wait_for_key_construction(key, false);
                if (ret < 0) {
                        key_put(key);
                        return ERR_PTR(ret);
                }
        }
        return key;
}
EXPORT_SYMBOL(request_key);

/**
 * request_key_with_auxdata - Request a key with auxiliary data for the upcaller
 * @type: The type of key we want.
 * @description: The searchable description of the key.
 * @callout_info: The data to pass to the instantiation upcall (or NULL).
 * @callout_len: The length of callout_info.
 * @aux: Auxiliary data for the upcall.
 *
 * As for request_key_and_link() except that it does not add the returned key
 * to a keyring if found and new keys are always allocated in the user's quota.
 *
 * Furthermore, it then works as wait_for_key_construction() to wait for the
 * completion of keys undergoing construction with a non-interruptible wait.
 */
struct key *request_key_with_auxdata(struct key_type *type,
                                     const char *description,
                                     const void *callout_info,
                                     size_t callout_len,
                                     void *aux)
{
        struct key *key;
        int ret;

        key = request_key_and_link(type, description, callout_info, callout_len,
                                   aux, NULL, KEY_ALLOC_IN_QUOTA);
        if (!IS_ERR(key)) {
                ret = wait_for_key_construction(key, false);
                if (ret < 0) {
                        key_put(key);
                        return ERR_PTR(ret);
                }
        }
        return key;
}
EXPORT_SYMBOL(request_key_with_auxdata);

/*
 * request_key_async - Request a key (allow async construction)
 * @type: Type of key.
 * @description: The searchable description of the key.
 * @callout_info: The data to pass to the instantiation upcall (or NULL).
 * @callout_len: The length of callout_info.
 *
 * As for request_key_and_link() except that it does not add the returned key
 * to a keyring if found, new keys are always allocated in the user's quota and
 * no auxiliary data can be passed.
 *
 * The caller should call wait_for_key_construction() to wait for the
 * completion of the returned key if it is still undergoing construction.
 */
struct key *request_key_async(struct key_type *type,
                              const char *description,
                              const void *callout_info,
                              size_t callout_len)
{
        return request_key_and_link(type, description, callout_info,
                                    callout_len, NULL, NULL,
                                    KEY_ALLOC_IN_QUOTA);
}
EXPORT_SYMBOL(request_key_async);

/*
 * request a key with auxiliary data for the upcaller (allow async construction)
 * @type: Type of key.
 * @description: The searchable description of the key.
 * @callout_info: The data to pass to the instantiation upcall (or NULL).
 * @callout_len: The length of callout_info.
 * @aux: Auxiliary data for the upcall.
 *
 * As for request_key_and_link() except that it does not add the returned key
 * to a keyring if found and new keys are always allocated in the user's quota.
 *
 * The caller should call wait_for_key_construction() to wait for the
 * completion of the returned key if it is still undergoing construction.
 */
struct key *request_key_async_with_auxdata(struct key_type *type,
                                           const char *description,
                                           const void *callout_info,
                                           size_t callout_len,
                                           void *aux)
{
        return request_key_and_link(type, description, callout_info,
                                    callout_len, aux, NULL, KEY_ALLOC_IN_QUOTA);
}
EXPORT_SYMBOL(request_key_async_with_auxdata);