security/keys/request_key_auth.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* Request key authorisation token key definition.
   3  *
   4  * Copyright (C) 2005 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  *
   7  * See Documentation/security/keys/request-key.rst
   8  */
   9
  10 #include <linux/sched.h>
  11 #include <linux/err.h>
  12 #include <linux/seq_file.h>
  13 #include <linux/slab.h>
  14 #include <linux/uaccess.h>
  15 #include "internal.h"
  16 #include <keys/request_key_auth-type.h>
  17
  18 static int request_key_auth_preparse(struct key_preparsed_payload *);
  19 static void request_key_auth_free_preparse(struct key_preparsed_payload *);
  20 static int request_key_auth_instantiate(struct key *,
  21                                         struct key_preparsed_payload *);
  22 static void request_key_auth_describe(const struct key *, struct seq_file *);
  23 static void request_key_auth_revoke(struct key *);
  24 static void request_key_auth_destroy(struct key *);
  25 static long request_key_auth_read(const struct key *, char __user *, size_t);
  26
  27 /*
  28  * The request-key authorisation key type definition.
  29  */
  30 struct key_type key_type_request_key_auth = {
  31         .name           = ".request_key_auth",
  32         .def_datalen    = sizeof(struct request_key_auth),
  33         .preparse       = request_key_auth_preparse,
  34         .free_preparse  = request_key_auth_free_preparse,
  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 static int request_key_auth_preparse(struct key_preparsed_payload *prep)
  43 {
  44         return 0;
  45 }
  46
  47 static void request_key_auth_free_preparse(struct key_preparsed_payload *prep)
  48 {
  49 }
  50
  51 /*
  52  * Instantiate a request-key authorisation key.
  53  */
  54 static int request_key_auth_instantiate(struct key *key,
  55                                         struct key_preparsed_payload *prep)
  56 {
  57         rcu_assign_keypointer(key, (struct request_key_auth *)prep->data);
  58         return 0;
  59 }
  60
  61 /*
  62  * Describe an authorisation token.
  63  */
  64 static void request_key_auth_describe(const struct key *key,
  65                                       struct seq_file *m)
  66 {
  67         struct request_key_auth *rka = dereference_key_rcu(key);
  68
  69         seq_puts(m, "key:");
  70         seq_puts(m, key->description);
  71         if (key_is_positive(key))
  72                 seq_printf(m, " pid:%d ci:%zu", rka->pid, rka->callout_len);
  73 }
  74
  75 /*
  76  * Read the callout_info data (retrieves the callout information).
  77  * - the key's semaphore is read-locked
  78  */
  79 static long request_key_auth_read(const struct key *key,
  80                                   char __user *buffer, size_t buflen)
  81 {
  82         struct request_key_auth *rka = dereference_key_locked(key);
  83         size_t datalen;
  84         long ret;
  85
  86         datalen = rka->callout_len;
  87         ret = datalen;
  88
  89         /* we can return the data as is */
  90         if (buffer && buflen > 0) {
  91                 if (buflen > datalen)
  92                         buflen = datalen;
  93
  94                 if (copy_to_user(buffer, rka->callout_info, buflen) != 0)
  95                         ret = -EFAULT;
  96         }
  97
  98         return ret;
  99 }
 100
 101 static void free_request_key_auth(struct request_key_auth *rka)
 102 {
 103         if (!rka)
 104                 return;
 105         key_put(rka->target_key);
 106         key_put(rka->dest_keyring);
 107         if (rka->cred)
 108                 put_cred(rka->cred);
 109         kfree(rka->callout_info);
 110         kfree(rka);
 111 }
 112
 113 /*
 114  * Dispose of the request_key_auth record under RCU conditions
 115  */
 116 static void request_key_auth_rcu_disposal(struct rcu_head *rcu)
 117 {
 118         struct request_key_auth *rka =
 119                 container_of(rcu, struct request_key_auth, rcu);
 120
 121         free_request_key_auth(rka);
 122 }
 123
 124 /*
 125  * Handle revocation of an authorisation token key.
 126  *
 127  * Called with the key sem write-locked.
 128  */
 129 static void request_key_auth_revoke(struct key *key)
 130 {
 131         struct request_key_auth *rka = dereference_key_locked(key);
 132
 133         kenter("{%d}", key->serial);
 134         rcu_assign_keypointer(key, NULL);
 135         call_rcu(&rka->rcu, request_key_auth_rcu_disposal);
 136 }
 137
 138 /*
 139  * Destroy an instantiation authorisation token key.
 140  */
 141 static void request_key_auth_destroy(struct key *key)
 142 {
 143         struct request_key_auth *rka = rcu_access_pointer(key->payload.rcu_data0);
 144
 145         kenter("{%d}", key->serial);
 146         if (rka) {
 147                 rcu_assign_keypointer(key, NULL);
 148                 call_rcu(&rka->rcu, request_key_auth_rcu_disposal);
 149         }
 150 }
 151
 152 /*
 153  * Create an authorisation token for /sbin/request-key or whoever to gain
 154  * access to the caller's security data.
 155  */
 156 struct key *request_key_auth_new(struct key *target, const char *op,
 157                                  const void *callout_info, size_t callout_len,
 158                                  struct key *dest_keyring)
 159 {
 160         struct request_key_auth *rka, *irka;
 161         const struct cred *cred = current_cred();
 162         struct key *authkey = NULL;
 163         char desc[20];
 164         int ret = -ENOMEM;
 165
 166         kenter("%d,", target->serial);
 167
 168         /* allocate a auth record */
 169         rka = kzalloc(sizeof(*rka), GFP_KERNEL);
 170         if (!rka)
 171                 goto error;
 172         rka->callout_info = kmemdup(callout_info, callout_len, GFP_KERNEL);
 173         if (!rka->callout_info)
 174                 goto error_free_rka;
 175         rka->callout_len = callout_len;
 176         strlcpy(rka->op, op, sizeof(rka->op));
 177
 178         /* see if the calling process is already servicing the key request of
 179          * another process */
 180         if (cred->request_key_auth) {
 181                 /* it is - use that instantiation context here too */
 182                 down_read(&cred->request_key_auth->sem);
 183
 184                 /* if the auth key has been revoked, then the key we're
 185                  * servicing is already instantiated */
 186                 if (test_bit(KEY_FLAG_REVOKED,
 187                              &cred->request_key_auth->flags)) {
 188                         up_read(&cred->request_key_auth->sem);
 189                         ret = -EKEYREVOKED;
 190                         goto error_free_rka;
 191                 }
 192
 193                 irka = cred->request_key_auth->payload.data[0];
 194                 rka->cred = get_cred(irka->cred);
 195                 rka->pid = irka->pid;
 196
 197                 up_read(&cred->request_key_auth->sem);
 198         }
 199         else {
 200                 /* it isn't - use this process as the context */
 201                 rka->cred = get_cred(cred);
 202                 rka->pid = current->pid;
 203         }
 204
 205         rka->target_key = key_get(target);
 206         rka->dest_keyring = key_get(dest_keyring);
 207
 208         /* allocate the auth key */
 209         sprintf(desc, "%x", target->serial);
 210
 211         authkey = key_alloc(&key_type_request_key_auth, desc,
 212                             cred->fsuid, cred->fsgid, cred,
 213                             KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH | KEY_POS_LINK |
 214                             KEY_USR_VIEW, KEY_ALLOC_NOT_IN_QUOTA, NULL);
 215         if (IS_ERR(authkey)) {
 216                 ret = PTR_ERR(authkey);
 217                 goto error_free_rka;
 218         }
 219
 220         /* construct the auth key */
 221         ret = key_instantiate_and_link(authkey, rka, 0, NULL, NULL);
 222         if (ret < 0)
 223                 goto error_put_authkey;
 224
 225         kleave(" = {%d,%d}", authkey->serial, refcount_read(&authkey->usage));
 226         return authkey;
 227
 228 error_put_authkey:
 229         key_put(authkey);
 230 error_free_rka:
 231         free_request_key_auth(rka);
 232 error:
 233         kleave("= %d", ret);
 234         return ERR_PTR(ret);
 235 }
 236
 237 /*
 238  * Search the current process's keyrings for the authorisation key for
 239  * instantiation of a key.
 240  */
 241 struct key *key_get_instantiation_authkey(key_serial_t target_id)
 242 {
 243         char description[16];
 244         struct keyring_search_context ctx = {
 245                 .index_key.type         = &key_type_request_key_auth,
 246                 .index_key.description  = description,
 247                 .cred                   = current_cred(),
 248                 .match_data.cmp         = key_default_cmp,
 249                 .match_data.raw_data    = description,
 250                 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
 251                 .flags                  = (KEYRING_SEARCH_DO_STATE_CHECK |
 252                                            KEYRING_SEARCH_RECURSE),
 253         };
 254         struct key *authkey;
 255         key_ref_t authkey_ref;
 256
 257         ctx.index_key.desc_len = sprintf(description, "%x", target_id);
 258
 259         rcu_read_lock();
 260         authkey_ref = search_process_keyrings_rcu(&ctx);
 261         rcu_read_unlock();
 262
 263         if (IS_ERR(authkey_ref)) {
 264                 authkey = ERR_CAST(authkey_ref);
 265                 if (authkey == ERR_PTR(-EAGAIN))
 266                         authkey = ERR_PTR(-ENOKEY);
 267                 goto error;
 268         }
 269
 270         authkey = key_ref_to_ptr(authkey_ref);
 271         if (test_bit(KEY_FLAG_REVOKED, &authkey->flags)) {
 272                 key_put(authkey);
 273                 authkey = ERR_PTR(-EKEYREVOKED);
 274         }
 275
 276 error:
 277         return authkey;
 278 }