security/keys/request_key_auth.c

   1 /* request_key_auth.c: request key authorisation controlling key def
   2  *
   3  * Copyright (C) 2005 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  *
  11  * See Documentation/keys-request-key.txt
  12  */
  13
  14 #include <linux/module.h>
  15 #include <linux/sched.h>
  16 #include <linux/err.h>
  17 #include <linux/seq_file.h>
  18 #include <asm/uaccess.h>
  19 #include "internal.h"
  20
  21 static int request_key_auth_instantiate(struct key *, const void *, size_t);
  22 static void request_key_auth_describe(const struct key *, struct seq_file *);
  23 static void request_key_auth_revoke(struct key *);
  24 static void request_key_auth_destroy(struct key *);
  25 static long request_key_auth_read(const struct key *, char __user *, size_t);
  26
  27 /*
  28  * the request-key authorisation key type definition
  29  */
  30 struct key_type key_type_request_key_auth = {
  31         .name           = ".request_key_auth",
  32         .def_datalen    = sizeof(struct request_key_auth),
  33         .instantiate    = request_key_auth_instantiate,
  34         .describe       = request_key_auth_describe,
  35         .revoke         = request_key_auth_revoke,
  36         .destroy        = request_key_auth_destroy,
  37         .read           = request_key_auth_read,
  38 };
  39
  40 /*****************************************************************************/
  41 /*
  42  * instantiate a request-key authorisation key
  43  */
  44 static int request_key_auth_instantiate(struct key *key,
  45                                         const void *data,
  46                                         size_t datalen)
  47 {
  48         key->payload.data = (struct request_key_auth *) data;
  49         return 0;
  50
  51 } /* end request_key_auth_instantiate() */
  52
  53 /*****************************************************************************/
  54 /*
  55  * reading a request-key authorisation key retrieves the callout information
  56  */
  57 static void request_key_auth_describe(const struct key *key,
  58                                       struct seq_file *m)
  59 {
  60         struct request_key_auth *rka = key->payload.data;
  61
  62         seq_puts(m, "key:");
  63         seq_puts(m, key->description);
  64         seq_printf(m, " pid:%d ci:%zu", rka->pid, strlen(rka->callout_info));
  65
  66 } /* end request_key_auth_describe() */
  67
  68 /*****************************************************************************/
  69 /*
  70  * read the callout_info data
  71  * - the key's semaphore is read-locked
  72  */
  73 static long request_key_auth_read(const struct key *key,
  74                                   char __user *buffer, size_t buflen)
  75 {
  76         struct request_key_auth *rka = key->payload.data;
  77         size_t datalen;
  78         long ret;
  79
  80         datalen = strlen(rka->callout_info);
  81         ret = datalen;
  82
  83         /* we can return the data as is */
  84         if (buffer && buflen > 0) {
  85                 if (buflen > datalen)
  86                         buflen = datalen;
  87
  88                 if (copy_to_user(buffer, rka->callout_info, buflen) != 0)
  89                         ret = -EFAULT;
  90         }
  91
  92         return ret;
  93
  94 } /* end request_key_auth_read() */
  95
  96 /*****************************************************************************/
  97 /*
  98  * handle revocation of an authorisation token key
  99  * - called with the key sem write-locked
 100  */
 101 static void request_key_auth_revoke(struct key *key)
 102 {
 103         struct request_key_auth *rka = key->payload.data;
 104
 105         kenter("{%d}", key->serial);
 106
 107         if (rka->context) {
 108                 put_task_struct(rka->context);
 109                 rka->context = NULL;
 110         }
 111
 112 } /* end request_key_auth_revoke() */
 113
 114 /*****************************************************************************/
 115 /*
 116  * destroy an instantiation authorisation token key
 117  */
 118 static void request_key_auth_destroy(struct key *key)
 119 {
 120         struct request_key_auth *rka = key->payload.data;
 121
 122         kenter("{%d}", key->serial);
 123
 124         if (rka->context) {
 125                 put_task_struct(rka->context);
 126                 rka->context = NULL;
 127         }
 128
 129         key_put(rka->target_key);
 130         kfree(rka);
 131
 132 } /* end request_key_auth_destroy() */
 133
 134 /*****************************************************************************/
 135 /*
 136  * create an authorisation token for /sbin/request-key or whoever to gain
 137  * access to the caller's security data
 138  */
 139 struct key *request_key_auth_new(struct key *target, const char *callout_info)
 140 {
 141         struct request_key_auth *rka, *irka;
 142         struct key *authkey = NULL;
 143         char desc[20];
 144         int ret;
 145
 146         kenter("%d,", target->serial);
 147
 148         /* allocate a auth record */
 149         rka = kmalloc(sizeof(*rka), GFP_KERNEL);
 150         if (!rka) {
 151                 kleave(" = -ENOMEM");
 152                 return ERR_PTR(-ENOMEM);
 153         }
 154
 155         /* see if the calling process is already servicing the key request of
 156          * another process */
 157         if (current->request_key_auth) {
 158                 /* it is - use that instantiation context here too */
 159                 down_read(&current->request_key_auth->sem);
 160
 161                 /* if the auth key has been revoked, then the key we're
 162                  * servicing is already instantiated */
 163                 if (test_bit(KEY_FLAG_REVOKED,
 164                              &current->request_key_auth->flags))
 165                         goto auth_key_revoked;
 166
 167                 irka = current->request_key_auth->payload.data;
 168                 rka->context = irka->context;
 169                 rka->pid = irka->pid;
 170                 get_task_struct(rka->context);
 171
 172                 up_read(&current->request_key_auth->sem);
 173         }
 174         else {
 175                 /* it isn't - use this process as the context */
 176                 rka->context = current;
 177                 rka->pid = current->pid;
 178                 get_task_struct(rka->context);
 179         }
 180
 181         rka->target_key = key_get(target);
 182         rka->callout_info = callout_info;
 183
 184         /* allocate the auth key */
 185         sprintf(desc, "%x", target->serial);
 186
 187         authkey = key_alloc(&key_type_request_key_auth, desc,
 188                             current->fsuid, current->fsgid, current,
 189                             KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH |
 190                             KEY_USR_VIEW, KEY_ALLOC_NOT_IN_QUOTA);
 191         if (IS_ERR(authkey)) {
 192                 ret = PTR_ERR(authkey);
 193                 goto error_alloc;
 194         }
 195
 196         /* construct and attach to the keyring */
 197         ret = key_instantiate_and_link(authkey, rka, 0, NULL, NULL);
 198         if (ret < 0)
 199                 goto error_inst;
 200
 201         kleave(" = {%d}", authkey->serial);
 202         return authkey;
 203
 204 auth_key_revoked:
 205         up_read(&current->request_key_auth->sem);
 206         kfree(rka);
 207         kleave("= -EKEYREVOKED");
 208         return ERR_PTR(-EKEYREVOKED);
 209
 210 error_inst:
 211         key_revoke(authkey);
 212         key_put(authkey);
 213 error_alloc:
 214         key_put(rka->target_key);
 215         kfree(rka);
 216         kleave("= %d", ret);
 217         return ERR_PTR(ret);
 218
 219 } /* end request_key_auth_new() */
 220
 221 /*****************************************************************************/
 222 /*
 223  * see if an authorisation key is associated with a particular key
 224  */
 225 static int key_get_instantiation_authkey_match(const struct key *key,
 226                                                const void *_id)
 227 {
 228         struct request_key_auth *rka = key->payload.data;
 229         key_serial_t id = (key_serial_t)(unsigned long) _id;
 230
 231         return rka->target_key->serial == id;
 232
 233 } /* end key_get_instantiation_authkey_match() */
 234
 235 /*****************************************************************************/
 236 /*
 237  * get the authorisation key for instantiation of a specific key if attached to
 238  * the current process's keyrings
 239  * - this key is inserted into a keyring and that is set as /sbin/request-key's
 240  *   session keyring
 241  * - a target_id of zero specifies any valid token
 242  */
 243 struct key *key_get_instantiation_authkey(key_serial_t target_id)
 244 {
 245         struct key *authkey;
 246         key_ref_t authkey_ref;
 247
 248         authkey_ref = search_process_keyrings(
 249                 &key_type_request_key_auth,
 250                 (void *) (unsigned long) target_id,
 251                 key_get_instantiation_authkey_match,
 252                 current);
 253
 254         if (IS_ERR(authkey_ref)) {
 255                 authkey = ERR_PTR(PTR_ERR(authkey_ref));
 256                 goto error;
 257         }
 258
 259         authkey = key_ref_to_ptr(authkey_ref);
 260         if (test_bit(KEY_FLAG_REVOKED, &authkey->flags)) {
 261                 key_put(authkey);
 262                 authkey = ERR_PTR(-EKEYREVOKED);
 263         }
 264
 265 error:
 266         return authkey;
 267
 268 } /* end key_get_instantiation_authkey() */