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