![David Howells](/assets/img/avatar_default.png)
Make it possible for a running process (such as gssapid) to be able to instantiate a key, as was requested by Trond Myklebust for NFS4. The patch makes the following changes: (1) A new, optional key type method has been added. This permits a key type to intercept requests at the point /sbin/request-key is about to be spawned and do something else with them - passing them over the rpc_pipefs files or netlink sockets for instance. The uninstantiated key, the authorisation key and the intended operation name are passed to the method. (2) The callout_info is no longer passed as an argument to /sbin/request-key to prevent unauthorised viewing of this data using ps or by looking in /proc/pid/cmdline. This means that the old /sbin/request-key program will not work with the patched kernel as it will expect to see an extra argument that is no longer there. A revised keyutils package will be made available tomorrow. (3) The callout_info is now attached to the authorisation key. Reading this key will retrieve the information. (4) A new field has been added to the task_struct. This holds the authorisation key currently active for a thread. Searches now look here for the caller's set of keys rather than looking for an auth key in the lowest level of the session keyring. This permits a thread to be servicing multiple requests at once and to switch between them. Note that this is per-thread, not per-process, and so is usable in multithreaded programs. The setting of this field is inherited across fork and exec. (5) A new keyctl function (KEYCTL_ASSUME_AUTHORITY) has been added that permits a thread to assume the authority to deal with an uninstantiated key. Assumption is only permitted if the authorisation key associated with the uninstantiated key is somewhere in the thread's keyrings. This function can also clear the assumption. (6) A new magic key specifier has been added to refer to the currently assumed authorisation key (KEY_SPEC_REQKEY_AUTH_KEY). (7) Instantiation will only proceed if the appropriate authorisation key is assumed first. The assumed authorisation key is discarded if instantiation is successful. (8) key_validate() is moved from the file of request_key functions to the file of permissions functions. (9) The documentation is updated. From: <Valdis.Kletnieks@vt.edu> Build fix. Signed-off-by: David Howells <dhowells@redhat.com> Cc: Trond Myklebust <trond.myklebust@fys.uio.no> Cc: Alexander Zangerl <az@bond.edu.au> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
226 lines
6.1 KiB
C
226 lines
6.1 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 <asm/uaccess.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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static long request_key_auth_read(const struct key *, char __user *, size_t);
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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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.read = request_key_auth_read,
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};
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/*****************************************************************************/
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/*
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* instantiate a request-key authorisation key
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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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key->payload.data = (struct request_key_auth *) data;
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return 0;
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} /* end request_key_auth_instantiate() */
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/*****************************************************************************/
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/*
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* reading a request-key authorisation key retrieves the callout information
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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 ci:%zu", rka->pid, strlen(rka->callout_info));
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} /* end request_key_auth_describe() */
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/*****************************************************************************/
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/*
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* read the callout_info data
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* - the key's semaphore is read-locked
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*/
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static long request_key_auth_read(const struct key *key,
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char __user *buffer, size_t buflen)
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{
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struct request_key_auth *rka = key->payload.data;
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size_t datalen;
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long ret;
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datalen = strlen(rka->callout_info);
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ret = datalen;
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/* we can return the data as is */
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if (buffer && buflen > 0) {
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if (buflen > datalen)
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buflen = datalen;
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if (copy_to_user(buffer, rka->callout_info, buflen) != 0)
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ret = -EFAULT;
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}
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return ret;
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} /* end request_key_auth_read() */
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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 an authorisation token for /sbin/request-key or whoever to gain
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* access to the caller's security data
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*/
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struct key *request_key_auth_new(struct key *target, const char *callout_info)
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{
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struct request_key_auth *rka, *irka;
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struct key *authkey = 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 auth record */
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rka = kmalloc(sizeof(*rka), GFP_KERNEL);
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if (!rka) {
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kleave(" = -ENOMEM");
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return ERR_PTR(-ENOMEM);
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}
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/* see if the calling process is already servicing the key request of
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* another process */
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if (current->request_key_auth) {
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/* it is - use that instantiation context here too */
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irka = current->request_key_auth->payload.data;
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rka->context = irka->context;
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rka->pid = irka->pid;
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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(target);
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rka->callout_info = callout_info;
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/* allocate the auth key */
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sprintf(desc, "%x", target->serial);
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authkey = key_alloc(&key_type_request_key_auth, desc,
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current->fsuid, current->fsgid,
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KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH |
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KEY_USR_VIEW, 1);
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if (IS_ERR(authkey)) {
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ret = PTR_ERR(authkey);
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goto error_alloc;
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}
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/* construct and attach to the keyring */
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ret = key_instantiate_and_link(authkey, rka, 0, NULL, NULL);
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if (ret < 0)
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goto error_inst;
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kleave(" = {%d})", authkey->serial);
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return authkey;
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error_inst:
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key_revoke(authkey);
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key_put(authkey);
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error_alloc:
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key_put(rka->target_key);
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kfree(rka);
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kleave("= %d", ret);
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return ERR_PTR(ret);
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} /* end request_key_auth_new() */
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/*****************************************************************************/
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/*
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* see if an authorisation key is associated with a particular key
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*/
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static int key_get_instantiation_authkey_match(const struct key *key,
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const void *_id)
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{
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struct request_key_auth *rka = key->payload.data;
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key_serial_t id = (key_serial_t)(unsigned long) _id;
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return rka->target_key->serial == id;
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} /* end key_get_instantiation_authkey_match() */
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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 key *authkey;
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key_ref_t authkey_ref;
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authkey_ref = search_process_keyrings(
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&key_type_request_key_auth,
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(void *) (unsigned long) target_id,
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key_get_instantiation_authkey_match,
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current);
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if (IS_ERR(authkey_ref)) {
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authkey = ERR_PTR(PTR_ERR(authkey_ref));
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goto error;
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}
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authkey = key_ref_to_ptr(authkey_ref);
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if (test_bit(KEY_FLAG_REVOKED, &authkey->flags)) {
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key_put(authkey);
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authkey = ERR_PTR(-EKEYREVOKED);
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}
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error:
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return authkey;
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} /* end key_get_instantiation_authkey() */
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