request_key_auth.c 6.8 KB
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/* Request key authorisation token key definition.
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 *
 * Copyright (C) 2005 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.
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 *
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 * See Documentation/security/keys-request-key.txt
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 */

#include <linux/module.h>
#include <linux/sched.h>
#include <linux/err.h>
#include <linux/seq_file.h>
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#include <linux/slab.h>
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#include <asm/uaccess.h>
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#include "internal.h"
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#include <keys/user-type.h>
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static int request_key_auth_preparse(struct key_preparsed_payload *);
static void request_key_auth_free_preparse(struct key_preparsed_payload *);
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static int request_key_auth_instantiate(struct key *,
					struct key_preparsed_payload *);
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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_revoke(struct key *);
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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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 */
struct key_type key_type_request_key_auth = {
	.name		= ".request_key_auth",
	.def_datalen	= sizeof(struct request_key_auth),
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	.preparse	= request_key_auth_preparse,
	.free_preparse	= request_key_auth_free_preparse,
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	.instantiate	= request_key_auth_instantiate,
	.describe	= request_key_auth_describe,
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	.revoke		= request_key_auth_revoke,
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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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static int request_key_auth_preparse(struct key_preparsed_payload *prep)
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{
	return 0;
}

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static void request_key_auth_free_preparse(struct key_preparsed_payload *prep)
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{
}

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/*
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 * Instantiate a request-key authorisation key.
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 */
static int request_key_auth_instantiate(struct key *key,
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					struct key_preparsed_payload *prep)
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{
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	key->payload.data = (struct request_key_auth *)prep->data;
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	return 0;
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}
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/*
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 * Describe an authorisation token.
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 */
static void request_key_auth_describe(const struct key *key,
				      struct seq_file *m)
{
	struct request_key_auth *rka = key->payload.data;

	seq_puts(m, "key:");
	seq_puts(m, key->description);
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	if (key_is_instantiated(key))
		seq_printf(m, " pid:%d ci:%zu", rka->pid, rka->callout_len);
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}
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/*
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 * Read the callout_info data (retrieves the callout information).
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 * - the key's semaphore is read-locked
 */
static long request_key_auth_read(const struct key *key,
				  char __user *buffer, size_t buflen)
{
	struct request_key_auth *rka = key->payload.data;
	size_t datalen;
	long ret;

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	datalen = rka->callout_len;
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	ret = datalen;

	/* we can return the data as is */
	if (buffer && buflen > 0) {
		if (buflen > datalen)
			buflen = datalen;

		if (copy_to_user(buffer, rka->callout_info, buflen) != 0)
			ret = -EFAULT;
	}

	return ret;
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}
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/*
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 * Handle revocation of an authorisation token key.
 *
 * Called with the key sem write-locked.
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 */
static void request_key_auth_revoke(struct key *key)
{
	struct request_key_auth *rka = key->payload.data;

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

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	if (rka->cred) {
		put_cred(rka->cred);
		rka->cred = NULL;
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	}
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}
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/*
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 * Destroy an instantiation authorisation token key.
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 */
static void request_key_auth_destroy(struct key *key)
{
	struct request_key_auth *rka = key->payload.data;

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

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	if (rka->cred) {
		put_cred(rka->cred);
		rka->cred = NULL;
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	}

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	key_put(rka->target_key);
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	key_put(rka->dest_keyring);
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	kfree(rka->callout_info);
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	kfree(rka);
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}
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/*
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 * Create an authorisation token for /sbin/request-key or whoever to gain
 * 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 void *callout_info,
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				 size_t callout_len, struct key *dest_keyring)
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{
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	struct request_key_auth *rka, *irka;
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	const struct cred *cred = current->cred;
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	struct key *authkey = NULL;
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	char desc[20];
	int ret;

	kenter("%d,", target->serial);

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	/* allocate a auth record */
	rka = kmalloc(sizeof(*rka), GFP_KERNEL);
	if (!rka) {
		kleave(" = -ENOMEM");
		return ERR_PTR(-ENOMEM);
	}
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	rka->callout_info = kmalloc(callout_len, GFP_KERNEL);
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	if (!rka->callout_info) {
		kleave(" = -ENOMEM");
		kfree(rka);
		return ERR_PTR(-ENOMEM);
	}
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	/* see if the calling process is already servicing the key request of
	 * another process */
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	if (cred->request_key_auth) {
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		/* it is - use that instantiation context here too */
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		down_read(&cred->request_key_auth->sem);
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		/* if the auth key has been revoked, then the key we're
		 * servicing is already instantiated */
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		if (test_bit(KEY_FLAG_REVOKED, &cred->request_key_auth->flags))
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			goto auth_key_revoked;

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		irka = cred->request_key_auth->payload.data;
		rka->cred = get_cred(irka->cred);
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		rka->pid = irka->pid;
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		up_read(&cred->request_key_auth->sem);
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	}
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	else {
		/* it isn't - use this process as the context */
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		rka->cred = get_cred(cred);
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		rka->pid = current->pid;
	}

	rka->target_key = key_get(target);
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	rka->dest_keyring = key_get(dest_keyring);
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	memcpy(rka->callout_info, callout_info, callout_len);
	rka->callout_len = callout_len;
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	/* allocate the auth key */
	sprintf(desc, "%x", target->serial);

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	authkey = key_alloc(&key_type_request_key_auth, desc,
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			    cred->fsuid, cred->fsgid, cred,
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			    KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH |
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			    KEY_USR_VIEW, KEY_ALLOC_NOT_IN_QUOTA);
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	if (IS_ERR(authkey)) {
		ret = PTR_ERR(authkey);
		goto error_alloc;
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	}

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	/* construct the auth key */
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	ret = key_instantiate_and_link(authkey, rka, 0, NULL, NULL);
	if (ret < 0)
		goto error_inst;
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	kleave(" = {%d,%d}", authkey->serial, atomic_read(&authkey->usage));
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	return authkey;

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auth_key_revoked:
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	up_read(&cred->request_key_auth->sem);
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	kfree(rka->callout_info);
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	kfree(rka);
	kleave("= -EKEYREVOKED");
	return ERR_PTR(-EKEYREVOKED);

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error_inst:
	key_revoke(authkey);
	key_put(authkey);
error_alloc:
	key_put(rka->target_key);
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	key_put(rka->dest_keyring);
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	kfree(rka->callout_info);
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	kfree(rka);
	kleave("= %d", ret);
	return ERR_PTR(ret);
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}
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/*
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 * Search the current process's keyrings for the authorisation key for
 * instantiation of a key.
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 */
struct key *key_get_instantiation_authkey(key_serial_t target_id)
{
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	char description[16];
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	struct keyring_search_context ctx = {
		.index_key.type		= &key_type_request_key_auth,
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		.index_key.description	= description,
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		.cred			= current_cred(),
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		.match			= user_match,
		.match_data		= description,
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		.flags			= KEYRING_SEARCH_LOOKUP_DIRECT,
	};
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	struct key *authkey;
	key_ref_t authkey_ref;

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	sprintf(description, "%x", target_id);

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	authkey_ref = search_process_keyrings(&ctx);
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	if (IS_ERR(authkey_ref)) {
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		authkey = ERR_CAST(authkey_ref);
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		if (authkey == ERR_PTR(-EAGAIN))
			authkey = ERR_PTR(-ENOKEY);
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		goto error;
	}
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	authkey = key_ref_to_ptr(authkey_ref);
	if (test_bit(KEY_FLAG_REVOKED, &authkey->flags)) {
		key_put(authkey);
		authkey = ERR_PTR(-EKEYREVOKED);
	}
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error:
	return authkey;
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}