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