![David Howells](/assets/img/avatar_default.png)
The attached patch adds documentation for the process by which request-key works, including how it permits helper processes to gain access to the requestor's keyrings. Signed-Off-By: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
184 lines
4.9 KiB
C
184 lines
4.9 KiB
C
/* request_key_auth.c: request key authorisation controlling key def
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*
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* Copyright (C) 2005 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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* See Documentation/keys-request-key.txt
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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/err.h>
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#include <linux/seq_file.h>
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#include "internal.h"
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static int request_key_auth_instantiate(struct key *, const void *, size_t);
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static void request_key_auth_describe(const struct key *, struct seq_file *);
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static void request_key_auth_destroy(struct key *);
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/*
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* the request-key authorisation key type definition
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*/
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struct key_type key_type_request_key_auth = {
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.name = ".request_key_auth",
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.def_datalen = sizeof(struct request_key_auth),
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.instantiate = request_key_auth_instantiate,
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.describe = request_key_auth_describe,
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.destroy = request_key_auth_destroy,
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};
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/*****************************************************************************/
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/*
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* instantiate a request-key authorisation record
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*/
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static int request_key_auth_instantiate(struct key *key,
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const void *data,
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size_t datalen)
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{
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struct request_key_auth *rka, *irka;
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struct key *instkey;
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int ret;
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ret = -ENOMEM;
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rka = kmalloc(sizeof(*rka), GFP_KERNEL);
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if (rka) {
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/* see if the calling process is already servicing the key
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* request of another process */
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instkey = key_get_instantiation_authkey(0);
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if (!IS_ERR(instkey)) {
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/* it is - use that instantiation context here too */
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irka = instkey->payload.data;
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rka->context = irka->context;
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rka->pid = irka->pid;
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key_put(instkey);
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}
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else {
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/* it isn't - use this process as the context */
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rka->context = current;
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rka->pid = current->pid;
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}
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rka->target_key = key_get((struct key *) data);
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key->payload.data = rka;
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ret = 0;
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}
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return ret;
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} /* end request_key_auth_instantiate() */
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/*****************************************************************************/
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/*
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*
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*/
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static void request_key_auth_describe(const struct key *key,
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struct seq_file *m)
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{
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struct request_key_auth *rka = key->payload.data;
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seq_puts(m, "key:");
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seq_puts(m, key->description);
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seq_printf(m, " pid:%d", rka->pid);
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} /* end request_key_auth_describe() */
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/*****************************************************************************/
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/*
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* destroy an instantiation authorisation token key
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*/
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static void request_key_auth_destroy(struct key *key)
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{
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struct request_key_auth *rka = key->payload.data;
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kenter("{%d}", key->serial);
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key_put(rka->target_key);
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kfree(rka);
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} /* end request_key_auth_destroy() */
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/*****************************************************************************/
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/*
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* create a session keyring to be for the invokation of /sbin/request-key and
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* stick an authorisation token in it
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*/
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struct key *request_key_auth_new(struct key *target, struct key **_rkakey)
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{
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struct key *keyring, *rkakey = NULL;
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char desc[20];
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int ret;
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kenter("%d,", target->serial);
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/* allocate a new session keyring */
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sprintf(desc, "_req.%u", target->serial);
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keyring = keyring_alloc(desc, current->fsuid, current->fsgid, 1, NULL);
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if (IS_ERR(keyring)) {
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kleave("= %ld", PTR_ERR(keyring));
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return keyring;
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}
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/* allocate the auth key */
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sprintf(desc, "%x", target->serial);
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rkakey = key_alloc(&key_type_request_key_auth, desc,
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current->fsuid, current->fsgid,
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KEY_POS_VIEW | KEY_USR_VIEW, 1);
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if (IS_ERR(rkakey)) {
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key_put(keyring);
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kleave("= %ld", PTR_ERR(rkakey));
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return rkakey;
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}
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/* construct and attach to the keyring */
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ret = key_instantiate_and_link(rkakey, target, 0, keyring, NULL);
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if (ret < 0) {
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key_revoke(rkakey);
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key_put(rkakey);
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key_put(keyring);
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kleave("= %d", ret);
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return ERR_PTR(ret);
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}
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*_rkakey = rkakey;
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kleave(" = {%d} ({%d})", keyring->serial, rkakey->serial);
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return keyring;
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} /* end request_key_auth_new() */
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/*****************************************************************************/
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/*
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* get the authorisation key for instantiation of a specific key if attached to
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* the current process's keyrings
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* - this key is inserted into a keyring and that is set as /sbin/request-key's
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* session keyring
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* - a target_id of zero specifies any valid token
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*/
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struct key *key_get_instantiation_authkey(key_serial_t target_id)
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{
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struct task_struct *tsk = current;
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struct key *instkey;
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/* we must have our own personal session keyring */
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if (!tsk->signal->session_keyring)
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return ERR_PTR(-EACCES);
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/* and it must contain a suitable request authorisation key
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* - lock RCU against session keyring changing
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*/
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rcu_read_lock();
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instkey = keyring_search_instkey(
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rcu_dereference(tsk->signal->session_keyring), target_id);
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rcu_read_unlock();
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return instkey;
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} /* end key_get_instantiation_authkey() */
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