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 <linux/slab.h>
  19 #include <asm/uaccess.h>
  20 #include "internal.h"
  21
  22 static int request_key_auth_instantiate(struct key *, const void *, size_t);
  23 static void request_key_auth_describe(const struct key *, struct seq_file *);
  24 static void request_key_auth_revoke(struct key *);
  25 static void request_key_auth_destroy(struct key *);
  26 static long request_key_auth_read(const struct key *, char __user *, size_t);
  27
  28 /*
  29  * the request-key authorisation key type definition
  30  */
  31 struct key_type key_type_request_key_auth = {
  32         .name           = ".request_key_auth",
  33         .def_datalen    = sizeof(struct request_key_auth),
  34         .instantiate    = request_key_auth_instantiate,
  35         .describe       = request_key_auth_describe,
  36         .revoke         = request_key_auth_revoke,
  37         .destroy        = request_key_auth_destroy,
  38         .read           = request_key_auth_read,
  39 };
  40
  41 /*****************************************************************************/
  42 /*
  43  * instantiate a request-key authorisation key
  44  */
  45 static int request_key_auth_instantiate(struct key *key,
  46                                         const void *data,
  47                                         size_t datalen)
  48 {
  49         key->payload.data = (struct request_key_auth *) data;
  50         return 0;
  51
  52 } /* end request_key_auth_instantiate() */
  53
  54 /*****************************************************************************/
  55 /*
  56  * reading a request-key authorisation key retrieves the callout information
  57  */
  58 static void request_key_auth_describe(const struct key *key,
  59                                       struct seq_file *m)
  60 {
  61         struct request_key_auth *rka = key->payload.data;
  62
  63         seq_puts(m, "key:");
  64         seq_puts(m, key->description);
  65         seq_printf(m, " pid:%d ci:%zu", rka->pid, rka->callout_len);
  66
  67 } /* end request_key_auth_describe() */
  68
  69 /*****************************************************************************/
  70 /*
  71  * read the callout_info data
  72  * - the key's semaphore is read-locked
  73  */
  74 static long request_key_auth_read(const struct key *key,
  75                                   char __user *buffer, size_t buflen)
  76 {
  77         struct request_key_auth *rka = key->payload.data;
  78         size_t datalen;
  79         long ret;
  80
  81         datalen = rka->callout_len;
  82         ret = datalen;
  83
  84         /* we can return the data as is */
  85         if (buffer && buflen > 0) {
  86                 if (buflen > datalen)
  87                         buflen = datalen;
  88
  89                 if (copy_to_user(buffer, rka->callout_info, buflen) != 0)
  90                         ret = -EFAULT;
  91         }
  92
  93         return ret;
  94
  95 } /* end request_key_auth_read() */
  96
  97 /*****************************************************************************/
  98 /*
  99  * handle revocation of an authorisation token key
 100  * - called with the key sem write-locked
 101  */
 102 static void request_key_auth_revoke(struct key *key)
 103 {
 104         struct request_key_auth *rka = key->payload.data;
 105
 106         kenter("{%d}", key->serial);
 107
 108         if (rka->cred) {
 109                 put_cred(rka->cred);
 110                 rka->cred = NULL;
 111         }
 112
 113 } /* end request_key_auth_revoke() */
 114
 115 /*****************************************************************************/
 116 /*
 117  * destroy an instantiation authorisation token key
 118  */
 119 static void request_key_auth_destroy(struct key *key)
 120 {
 121         struct request_key_auth *rka = key->payload.data;
 122
 123         kenter("{%d}", key->serial);
 124
 125         if (rka->cred) {
 126                 put_cred(rka->cred);
 127                 rka->cred = NULL;
 128         }
 129
 130         key_put(rka->target_key);
 131         key_put(rka->dest_keyring);
 132         kfree(rka->callout_info);
 133         kfree(rka);
 134
 135 } /* end request_key_auth_destroy() */
 136
 137 /*****************************************************************************/
 138 /*
 139  * create an authorisation token for /sbin/request-key or whoever to gain
 140  * access to the caller's security data
 141  */
 142 struct key *request_key_auth_new(struct key *target, const void *callout_info,
 143                                  size_t callout_len, struct key *dest_keyring)
 144 {
 145         struct request_key_auth *rka, *irka;
 146         const struct cred *cred = current->cred;
 147         struct key *authkey = NULL;
 148         char desc[20];
 149         int ret;
 150
 151         kenter("%d,", target->serial);
 152
 153         /* allocate a auth record */
 154         rka = kmalloc(sizeof(*rka), GFP_KERNEL);
 155         if (!rka) {
 156                 kleave(" = -ENOMEM");
 157                 return ERR_PTR(-ENOMEM);
 158         }
 159         rka->callout_info = kmalloc(callout_len, GFP_KERNEL);
 160         if (!rka->callout_info) {
 161                 kleave(" = -ENOMEM");
 162                 kfree(rka);
 163                 return ERR_PTR(-ENOMEM);
 164         }
 165
 166         /* see if the calling process is already servicing the key request of
 167          * another process */
 168         if (cred->request_key_auth) {
 169                 /* it is - use that instantiation context here too */
 170                 down_read(&cred->request_key_auth->sem);
 171
 172                 /* if the auth key has been revoked, then the key we're
 173                  * servicing is already instantiated */
 174                 if (test_bit(KEY_FLAG_REVOKED, &cred->request_key_auth->flags))
 175                         goto auth_key_revoked;
 176
 177                 irka = cred->request_key_auth->payload.data;
 178                 rka->cred = get_cred(irka->cred);
 179                 rka->pid = irka->pid;
 180
 181                 up_read(&cred->request_key_auth->sem);
 182         }
 183         else {
 184                 /* it isn't - use this process as the context */
 185                 rka->cred = get_cred(cred);
 186                 rka->pid = current->pid;
 187         }
 188
 189         rka->target_key = key_get(target);
 190         rka->dest_keyring = key_get(dest_keyring);
 191         memcpy(rka->callout_info, callout_info, callout_len);
 192         rka->callout_len = callout_len;
 193
 194         /* allocate the auth key */
 195         sprintf(desc, "%x", target->serial);
 196
 197         authkey = key_alloc(&key_type_request_key_auth, desc,
 198                             cred->fsuid, cred->fsgid, cred,
 199                             KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH |
 200                             KEY_USR_VIEW, KEY_ALLOC_NOT_IN_QUOTA);
 201         if (IS_ERR(authkey)) {
 202                 ret = PTR_ERR(authkey);
 203                 goto error_alloc;
 204         }
 205
 206         /* construct the auth key */
 207         ret = key_instantiate_and_link(authkey, rka, 0, NULL, NULL);
 208         if (ret < 0)
 209                 goto error_inst;
 210
 211         kleave(" = {%d,%d}", authkey->serial, atomic_read(&authkey->usage));
 212         return authkey;
 213
 214 auth_key_revoked:
 215         up_read(&cred->request_key_auth->sem);
 216         kfree(rka->callout_info);
 217         kfree(rka);
 218         kleave("= -EKEYREVOKED");
 219         return ERR_PTR(-EKEYREVOKED);
 220
 221 error_inst:
 222         key_revoke(authkey);
 223         key_put(authkey);
 224 error_alloc:
 225         key_put(rka->target_key);
 226         key_put(rka->dest_keyring);
 227         kfree(rka->callout_info);
 228         kfree(rka);
 229         kleave("= %d", ret);
 230         return ERR_PTR(ret);
 231
 232 } /* end request_key_auth_new() */
 233
 234 /*****************************************************************************/
 235 /*
 236  * see if an authorisation key is associated with a particular key
 237  */
 238 static int key_get_instantiation_authkey_match(const struct key *key,
 239                                                const void *_id)
 240 {
 241         struct request_key_auth *rka = key->payload.data;
 242         key_serial_t id = (key_serial_t)(unsigned long) _id;
 243
 244         return rka->target_key->serial == id;
 245
 246 } /* end key_get_instantiation_authkey_match() */
 247
 248 /*****************************************************************************/
 249 /*
 250  * get the authorisation key for instantiation of a specific key if attached to
 251  * the current process's keyrings
 252  * - this key is inserted into a keyring and that is set as /sbin/request-key's
 253  *   session keyring
 254  * - a target_id of zero specifies any valid token
 255  */
 256 struct key *key_get_instantiation_authkey(key_serial_t target_id)
 257 {
 258         const struct cred *cred = current_cred();
 259         struct key *authkey;
 260         key_ref_t authkey_ref;
 261
 262         authkey_ref = search_process_keyrings(
 263                 &key_type_request_key_auth,
 264                 (void *) (unsigned long) target_id,
 265                 key_get_instantiation_authkey_match,
 266                 cred);
 267
 268         if (IS_ERR(authkey_ref)) {
 269                 authkey = ERR_CAST(authkey_ref);
 270                 goto error;
 271         }
 272
 273         authkey = key_ref_to_ptr(authkey_ref);
 274         if (test_bit(KEY_FLAG_REVOKED, &authkey->flags)) {
 275                 key_put(authkey);
 276                 authkey = ERR_PTR(-EKEYREVOKED);
 277         }
 278
 279 error:
 280         return authkey;
 281
 282 } /* end key_get_instantiation_authkey() */