security/keys/request_key_auth.c

   1 /* Request key authorisation token key definition.
   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/security/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 #include <keys/user-type.h>
  22
  23 static int request_key_auth_preparse(struct key_preparsed_payload *);
  24 static void request_key_auth_free_preparse(struct key_preparsed_payload *);
  25 static int request_key_auth_instantiate(struct key *,
  26                                         struct key_preparsed_payload *);
  27 static void request_key_auth_describe(const struct key *, struct seq_file *);
  28 static void request_key_auth_revoke(struct key *);
  29 static void request_key_auth_destroy(struct key *);
  30 static long request_key_auth_read(const struct key *, char __user *, size_t);
  31
  32 /*
  33  * The request-key authorisation key type definition.
  34  */
  35 struct key_type key_type_request_key_auth = {
  36         .name           = ".request_key_auth",
  37         .def_datalen    = sizeof(struct request_key_auth),
  38         .preparse       = request_key_auth_preparse,
  39         .free_preparse  = request_key_auth_free_preparse,
  40         .instantiate    = request_key_auth_instantiate,
  41         .describe       = request_key_auth_describe,
  42         .revoke         = request_key_auth_revoke,
  43         .destroy        = request_key_auth_destroy,
  44         .read           = request_key_auth_read,
  45 };
  46
  47 static int request_key_auth_preparse(struct key_preparsed_payload *prep)
  48 {
  49         return 0;
  50 }
  51
  52 static void request_key_auth_free_preparse(struct key_preparsed_payload *prep)
  53 {
  54 }
  55
  56 /*
  57  * Instantiate a request-key authorisation key.
  58  */
  59 static int request_key_auth_instantiate(struct key *key,
  60                                         struct key_preparsed_payload *prep)
  61 {
  62         key->payload.data[0] = (struct request_key_auth *)prep->data;
  63         return 0;
  64 }
  65
  66 /*
  67  * Describe an authorisation token.
  68  */
  69 static void request_key_auth_describe(const struct key *key,
  70                                       struct seq_file *m)
  71 {
  72         struct request_key_auth *rka = key->payload.data[0];
  73
  74         if (!rka)
  75                 return;
  76
  77         seq_puts(m, "key:");
  78         seq_puts(m, key->description);
  79         if (key_is_positive(key))
  80                 seq_printf(m, " pid:%d ci:%zu", rka->pid, rka->callout_len);
  81 }
  82
  83 /*
  84  * Read the callout_info data (retrieves the callout information).
  85  * - the key's semaphore is read-locked
  86  */
  87 static long request_key_auth_read(const struct key *key,
  88                                   char __user *buffer, size_t buflen)
  89 {
  90         struct request_key_auth *rka = key->payload.data[0];
  91         size_t datalen;
  92         long ret;
  93
  94         if (!rka)
  95                 return -EKEYREVOKED;
  96
  97         datalen = rka->callout_len;
  98         ret = datalen;
  99
 100         /* we can return the data as is */
 101         if (buffer && buflen > 0) {
 102                 if (buflen > datalen)
 103                         buflen = datalen;
 104
 105                 if (copy_to_user(buffer, rka->callout_info, buflen) != 0)
 106                         ret = -EFAULT;
 107         }
 108
 109         return ret;
 110 }
 111
 112 /*
 113  * Handle revocation of an authorisation token key.
 114  *
 115  * Called with the key sem write-locked.
 116  */
 117 static void request_key_auth_revoke(struct key *key)
 118 {
 119         struct request_key_auth *rka = key->payload.data[0];
 120
 121         kenter("{%d}", key->serial);
 122
 123         if (rka->cred) {
 124                 put_cred(rka->cred);
 125                 rka->cred = NULL;
 126         }
 127 }
 128
 129 /*
 130  * Destroy an instantiation authorisation token key.
 131  */
 132 static void request_key_auth_destroy(struct key *key)
 133 {
 134         struct request_key_auth *rka = key->payload.data[0];
 135
 136         kenter("{%d}", key->serial);
 137
 138         if (rka->cred) {
 139                 put_cred(rka->cred);
 140                 rka->cred = NULL;
 141         }
 142
 143         key_put(rka->target_key);
 144         key_put(rka->dest_keyring);
 145         kfree(rka->callout_info);
 146         kfree(rka);
 147 }
 148
 149 /*
 150  * Create an authorisation token for /sbin/request-key or whoever to gain
 151  * access to the caller's security data.
 152  */
 153 struct key *request_key_auth_new(struct key *target, const void *callout_info,
 154                                  size_t callout_len, struct key *dest_keyring)
 155 {
 156         struct request_key_auth *rka, *irka;
 157         const struct cred *cred = current->cred;
 158         struct key *authkey = NULL;
 159         char desc[20];
 160         int ret;
 161
 162         kenter("%d,", target->serial);
 163
 164         /* allocate a auth record */
 165         rka = kmalloc(sizeof(*rka), GFP_KERNEL);
 166         if (!rka) {
 167                 kleave(" = -ENOMEM");
 168                 return ERR_PTR(-ENOMEM);
 169         }
 170         rka->callout_info = kmalloc(callout_len, GFP_KERNEL);
 171         if (!rka->callout_info) {
 172                 kleave(" = -ENOMEM");
 173                 kfree(rka);
 174                 return ERR_PTR(-ENOMEM);
 175         }
 176
 177         /* see if the calling process is already servicing the key request of
 178          * another process */
 179         if (cred->request_key_auth) {
 180                 /* it is - use that instantiation context here too */
 181                 down_read(&cred->request_key_auth->sem);
 182
 183                 /* if the auth key has been revoked, then the key we're
 184                  * servicing is already instantiated */
 185                 if (test_bit(KEY_FLAG_REVOKED, &cred->request_key_auth->flags))
 186                         goto auth_key_revoked;
 187
 188                 irka = cred->request_key_auth->payload.data[0];
 189                 rka->cred = get_cred(irka->cred);
 190                 rka->pid = irka->pid;
 191
 192                 up_read(&cred->request_key_auth->sem);
 193         }
 194         else {
 195                 /* it isn't - use this process as the context */
 196                 rka->cred = get_cred(cred);
 197                 rka->pid = current->pid;
 198         }
 199
 200         rka->target_key = key_get(target);
 201         rka->dest_keyring = key_get(dest_keyring);
 202         memcpy(rka->callout_info, callout_info, callout_len);
 203         rka->callout_len = callout_len;
 204
 205         /* allocate the auth key */
 206         sprintf(desc, "%x", target->serial);
 207
 208         authkey = key_alloc(&key_type_request_key_auth, desc,
 209                             cred->fsuid, cred->fsgid, cred,
 210                             KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH |
 211                             KEY_USR_VIEW, KEY_ALLOC_NOT_IN_QUOTA, NULL);
 212         if (IS_ERR(authkey)) {
 213                 ret = PTR_ERR(authkey);
 214                 goto error_alloc;
 215         }
 216
 217         /* construct the auth key */
 218         ret = key_instantiate_and_link(authkey, rka, 0, NULL, NULL);
 219         if (ret < 0)
 220                 goto error_inst;
 221
 222         kleave(" = {%d,%d}", authkey->serial, atomic_read(&authkey->usage));
 223         return authkey;
 224
 225 auth_key_revoked:
 226         up_read(&cred->request_key_auth->sem);
 227         kfree(rka->callout_info);
 228         kfree(rka);
 229         kleave("= -EKEYREVOKED");
 230         return ERR_PTR(-EKEYREVOKED);
 231
 232 error_inst:
 233         key_revoke(authkey);
 234         key_put(authkey);
 235 error_alloc:
 236         key_put(rka->target_key);
 237         key_put(rka->dest_keyring);
 238         kfree(rka->callout_info);
 239         kfree(rka);
 240         kleave("= %d", ret);
 241         return ERR_PTR(ret);
 242 }
 243
 244 /*
 245  * Search the current process's keyrings for the authorisation key for
 246  * instantiation of a key.
 247  */
 248 struct key *key_get_instantiation_authkey(key_serial_t target_id)
 249 {
 250         char description[16];
 251         struct keyring_search_context ctx = {
 252                 .index_key.type         = &key_type_request_key_auth,
 253                 .index_key.description  = description,
 254                 .cred                   = current_cred(),
 255                 .match_data.cmp         = key_default_cmp,
 256                 .match_data.raw_data    = description,
 257                 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
 258                 .flags                  = KEYRING_SEARCH_DO_STATE_CHECK,
 259         };
 260         struct key *authkey;
 261         key_ref_t authkey_ref;
 262
 263         ctx.index_key.desc_len = sprintf(description, "%x", target_id);
 264
 265         authkey_ref = search_process_keyrings(&ctx);
 266
 267         if (IS_ERR(authkey_ref)) {
 268                 authkey = ERR_CAST(authkey_ref);
 269                 if (authkey == ERR_PTR(-EAGAIN))
 270                         authkey = ERR_PTR(-ENOKEY);
 271                 goto error;
 272         }
 273
 274         authkey = key_ref_to_ptr(authkey_ref);
 275         if (test_bit(KEY_FLAG_REVOKED, &authkey->flags)) {
 276                 key_put(authkey);
 277                 authkey = ERR_PTR(-EKEYREVOKED);
 278         }
 279
 280 error:
 281         return authkey;
 282 }