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/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  * 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
  52 /*
  53  * Describe an authorisation token.
  54  */
  55 static void request_key_auth_describe(const struct key *key,
  56                                       struct seq_file *m)
  57 {
  58         struct request_key_auth *rka = key->payload.data;
  59
  60         seq_puts(m, "key:");
  61         seq_puts(m, key->description);
  62         seq_printf(m, " pid:%d ci:%zu", rka->pid, rka->callout_len);
  63 }
  64
  65 /*
  66  * Read the callout_info data (retrieves the callout information).
  67  * - the key's semaphore is read-locked
  68  */
  69 static long request_key_auth_read(const struct key *key,
  70                                   char __user *buffer, size_t buflen)
  71 {
  72         struct request_key_auth *rka = key->payload.data;
  73         size_t datalen;
  74         long ret;
  75
  76         datalen = rka->callout_len;
  77         ret = datalen;
  78
  79         /* we can return the data as is */
  80         if (buffer && buflen > 0) {
  81                 if (buflen > datalen)
  82                         buflen = datalen;
  83
  84                 if (copy_to_user(buffer, rka->callout_info, buflen) != 0)
  85                         ret = -EFAULT;
  86         }
  87
  88         return ret;
  89 }
  90
  91 /*
  92  * Handle revocation of an authorisation token key.
  93  *
  94  * Called with the key sem write-locked.
  95  */
  96 static void request_key_auth_revoke(struct key *key)
  97 {
  98         struct request_key_auth *rka = key->payload.data;
  99
 100         kenter("{%d}", key->serial);
 101
 102         if (rka->cred) {
 103                 put_cred(rka->cred);
 104                 rka->cred = NULL;
 105         }
 106 }
 107
 108 /*
 109  * Destroy an instantiation authorisation token key.
 110  */
 111 static void request_key_auth_destroy(struct key *key)
 112 {
 113         struct request_key_auth *rka = key->payload.data;
 114
 115         kenter("{%d}", key->serial);
 116
 117         if (rka->cred) {
 118                 put_cred(rka->cred);
 119                 rka->cred = NULL;
 120         }
 121
 122         key_put(rka->target_key);
 123         key_put(rka->dest_keyring);
 124         kfree(rka->callout_info);
 125         kfree(rka);
 126 }
 127
 128 /*
 129  * Create an authorisation token for /sbin/request-key or whoever to gain
 130  * access to the caller's security data.
 131  */
 132 struct key *request_key_auth_new(struct key *target, const void *callout_info,
 133                                  size_t callout_len, struct key *dest_keyring)
 134 {
 135         struct request_key_auth *rka, *irka;
 136         const struct cred *cred = current->cred;
 137         struct key *authkey = NULL;
 138         char desc[20];
 139         int ret;
 140
 141         kenter("%d,", target->serial);
 142
 143         /* allocate a auth record */
 144         rka = kmalloc(sizeof(*rka), GFP_KERNEL);
 145         if (!rka) {
 146                 kleave(" = -ENOMEM");
 147                 return ERR_PTR(-ENOMEM);
 148         }
 149         rka->callout_info = kmalloc(callout_len, GFP_KERNEL);
 150         if (!rka->callout_info) {
 151                 kleave(" = -ENOMEM");
 152                 kfree(rka);
 153                 return ERR_PTR(-ENOMEM);
 154         }
 155
 156         /* see if the calling process is already servicing the key request of
 157          * another process */
 158         if (cred->request_key_auth) {
 159                 /* it is - use that instantiation context here too */
 160                 down_read(&cred->request_key_auth->sem);
 161
 162                 /* if the auth key has been revoked, then the key we're
 163                  * servicing is already instantiated */
 164                 if (test_bit(KEY_FLAG_REVOKED, &cred->request_key_auth->flags))
 165                         goto auth_key_revoked;
 166
 167                 irka = cred->request_key_auth->payload.data;
 168                 rka->cred = get_cred(irka->cred);
 169                 rka->pid = irka->pid;
 170
 171                 up_read(&cred->request_key_auth->sem);
 172         }
 173         else {
 174                 /* it isn't - use this process as the context */
 175                 rka->cred = get_cred(cred);
 176                 rka->pid = current->pid;
 177         }
 178
 179         rka->target_key = key_get(target);
 180         rka->dest_keyring = key_get(dest_keyring);
 181         memcpy(rka->callout_info, callout_info, callout_len);
 182         rka->callout_len = callout_len;
 183
 184         /* allocate the auth key */
 185         sprintf(desc, "%x", target->serial);
 186
 187         authkey = key_alloc(&key_type_request_key_auth, desc,
 188                             cred->fsuid, cred->fsgid, cred,
 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 the auth key */
 197         ret = key_instantiate_and_link(authkey, rka, 0, NULL, NULL);
 198         if (ret < 0)
 199                 goto error_inst;
 200
 201         kleave(" = {%d,%d}", authkey->serial, atomic_read(&authkey->usage));
 202         return authkey;
 203
 204 auth_key_revoked:
 205         up_read(&cred->request_key_auth->sem);
 206         kfree(rka->callout_info);
 207         kfree(rka);
 208         kleave("= -EKEYREVOKED");
 209         return ERR_PTR(-EKEYREVOKED);
 210
 211 error_inst:
 212         key_revoke(authkey);
 213         key_put(authkey);
 214 error_alloc:
 215         key_put(rka->target_key);
 216         key_put(rka->dest_keyring);
 217         kfree(rka->callout_info);
 218         kfree(rka);
 219         kleave("= %d", ret);
 220         return ERR_PTR(ret);
 221 }
 222
 223 /*
 224  * See if an authorisation key is associated with a particular key.
 225  */
 226 static int key_get_instantiation_authkey_match(const struct key *key,
 227                                                const void *_id)
 228 {
 229         struct request_key_auth *rka = key->payload.data;
 230         key_serial_t id = (key_serial_t)(unsigned long) _id;
 231
 232         return rka->target_key->serial == id;
 233 }
 234
 235 /*
 236  * Search the current process's keyrings for the authorisation key for
 237  * instantiation of a key.
 238  */
 239 struct key *key_get_instantiation_authkey(key_serial_t target_id)
 240 {
 241         const struct cred *cred = current_cred();
 242         struct key *authkey;
 243         key_ref_t authkey_ref;
 244
 245         authkey_ref = search_process_keyrings(
 246                 &key_type_request_key_auth,
 247                 (void *) (unsigned long) target_id,
 248                 key_get_instantiation_authkey_match,
 249                 cred);
 250
 251         if (IS_ERR(authkey_ref)) {
 252                 authkey = ERR_CAST(authkey_ref);
 253                 goto error;
 254         }
 255
 256         authkey = key_ref_to_ptr(authkey_ref);
 257         if (test_bit(KEY_FLAG_REVOKED, &authkey->flags)) {
 258                 key_put(authkey);
 259                 authkey = ERR_PTR(-EKEYREVOKED);
 260         }
 261
 262 error:
 263         return authkey;
 264 }