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         if (!rka)
  70                 return;
  71
  72         seq_puts(m, "key:");
  73         seq_puts(m, key->description);
  74         if (key_is_positive(key))
  75                 seq_printf(m, " pid:%d ci:%zu", rka->pid, rka->callout_len);
  76 }
  77
  78 /*
  79  * Read the callout_info data (retrieves the callout information).
  80  * - the key's semaphore is read-locked
  81  */
  82 static long request_key_auth_read(const struct key *key,
  83                                   char __user *buffer, size_t buflen)
  84 {
  85         struct request_key_auth *rka = dereference_key_locked(key);
  86         size_t datalen;
  87         long ret;
  88
  89         if (!rka)
  90                 return -EKEYREVOKED;
  91
  92         datalen = rka->callout_len;
  93         ret = datalen;
  94
  95         /* we can return the data as is */
  96         if (buffer && buflen > 0) {
  97                 if (buflen > datalen)
  98                         buflen = datalen;
  99
 100                 if (copy_to_user(buffer, rka->callout_info, buflen) != 0)
 101                         ret = -EFAULT;
 102         }
 103
 104         return ret;
 105 }
 106
 107 static void free_request_key_auth(struct request_key_auth *rka)
 108 {
 109         if (!rka)
 110                 return;
 111         key_put(rka->target_key);
 112         key_put(rka->dest_keyring);
 113         if (rka->cred)
 114                 put_cred(rka->cred);
 115         kfree(rka->callout_info);
 116         kfree(rka);
 117 }
 118
 119 /*
 120  * Dispose of the request_key_auth record under RCU conditions
 121  */
 122 static void request_key_auth_rcu_disposal(struct rcu_head *rcu)
 123 {
 124         struct request_key_auth *rka =
 125                 container_of(rcu, struct request_key_auth, rcu);
 126
 127         free_request_key_auth(rka);
 128 }
 129
 130 /*
 131  * Handle revocation of an authorisation token key.
 132  *
 133  * Called with the key sem write-locked.
 134  */
 135 static void request_key_auth_revoke(struct key *key)
 136 {
 137         struct request_key_auth *rka = dereference_key_locked(key);
 138
 139         kenter("{%d}", key->serial);
 140         rcu_assign_keypointer(key, NULL);
 141         call_rcu(&rka->rcu, request_key_auth_rcu_disposal);
 142 }
 143
 144 /*
 145  * Destroy an instantiation authorisation token key.
 146  */
 147 static void request_key_auth_destroy(struct key *key)
 148 {
 149         struct request_key_auth *rka = rcu_access_pointer(key->payload.rcu_data0);
 150
 151         kenter("{%d}", key->serial);
 152         if (rka) {
 153                 rcu_assign_keypointer(key, NULL);
 154                 call_rcu(&rka->rcu, request_key_auth_rcu_disposal);
 155         }
 156 }
 157
 158 /*
 159  * Create an authorisation token for /sbin/request-key or whoever to gain
 160  * access to the caller's security data.
 161  */
 162 struct key *request_key_auth_new(struct key *target, const char *op,
 163                                  const void *callout_info, size_t callout_len,
 164                                  struct key *dest_keyring)
 165 {
 166         struct request_key_auth *rka, *irka;
 167         const struct cred *cred = current_cred();
 168         struct key *authkey = NULL;
 169         char desc[20];
 170         int ret = -ENOMEM;
 171
 172         kenter("%d,", target->serial);
 173
 174         /* allocate a auth record */
 175         rka = kzalloc(sizeof(*rka), GFP_KERNEL);
 176         if (!rka)
 177                 goto error;
 178         rka->callout_info = kmemdup(callout_info, callout_len, GFP_KERNEL);
 179         if (!rka->callout_info)
 180                 goto error_free_rka;
 181         rka->callout_len = callout_len;
 182         strlcpy(rka->op, op, sizeof(rka->op));
 183
 184         /* see if the calling process is already servicing the key request of
 185          * another process */
 186         if (cred->request_key_auth) {
 187                 /* it is - use that instantiation context here too */
 188                 down_read(&cred->request_key_auth->sem);
 189
 190                 /* if the auth key has been revoked, then the key we're
 191                  * servicing is already instantiated */
 192                 if (test_bit(KEY_FLAG_REVOKED,
 193                              &cred->request_key_auth->flags)) {
 194                         up_read(&cred->request_key_auth->sem);
 195                         ret = -EKEYREVOKED;
 196                         goto error_free_rka;
 197                 }
 198
 199                 irka = cred->request_key_auth->payload.data[0];
 200                 rka->cred = get_cred(irka->cred);
 201                 rka->pid = irka->pid;
 202
 203                 up_read(&cred->request_key_auth->sem);
 204         }
 205         else {
 206                 /* it isn't - use this process as the context */
 207                 rka->cred = get_cred(cred);
 208                 rka->pid = current->pid;
 209         }
 210
 211         rka->target_key = key_get(target);
 212         rka->dest_keyring = key_get(dest_keyring);
 213
 214         /* allocate the auth key */
 215         sprintf(desc, "%x", target->serial);
 216
 217         authkey = key_alloc(&key_type_request_key_auth, desc,
 218                             cred->fsuid, cred->fsgid, cred,
 219                             KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH | KEY_POS_LINK |
 220                             KEY_USR_VIEW, KEY_ALLOC_NOT_IN_QUOTA, NULL);
 221         if (IS_ERR(authkey)) {
 222                 ret = PTR_ERR(authkey);
 223                 goto error_free_rka;
 224         }
 225
 226         /* construct the auth key */
 227         ret = key_instantiate_and_link(authkey, rka, 0, NULL, NULL);
 228         if (ret < 0)
 229                 goto error_put_authkey;
 230
 231         kleave(" = {%d,%d}", authkey->serial, refcount_read(&authkey->usage));
 232         return authkey;
 233
 234 error_put_authkey:
 235         key_put(authkey);
 236 error_free_rka:
 237         free_request_key_auth(rka);
 238 error:
 239         kleave("= %d", ret);
 240         return ERR_PTR(ret);
 241 }
 242
 243 /*
 244  * Search the current process's keyrings for the authorisation key for
 245  * instantiation of a key.
 246  */
 247 struct key *key_get_instantiation_authkey(key_serial_t target_id)
 248 {
 249         char description[16];
 250         struct keyring_search_context ctx = {
 251                 .index_key.type         = &key_type_request_key_auth,
 252                 .index_key.description  = description,
 253                 .cred                   = current_cred(),
 254                 .match_data.cmp         = key_default_cmp,
 255                 .match_data.raw_data    = description,
 256                 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
 257                 .flags                  = (KEYRING_SEARCH_DO_STATE_CHECK |
 258                                            KEYRING_SEARCH_RECURSE),
 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         rcu_read_lock();
 266         authkey_ref = search_process_keyrings_rcu(&ctx);
 267         rcu_read_unlock();
 268
 269         if (IS_ERR(authkey_ref)) {
 270                 authkey = ERR_CAST(authkey_ref);
 271                 if (authkey == ERR_PTR(-EAGAIN))
 272                         authkey = ERR_PTR(-ENOKEY);
 273                 goto error;
 274         }
 275
 276         authkey = key_ref_to_ptr(authkey_ref);
 277         if (test_bit(KEY_FLAG_REVOKED, &authkey->flags)) {
 278                 key_put(authkey);
 279                 authkey = ERR_PTR(-EKEYREVOKED);
 280         }
 281
 282 error:
 283         return authkey;
 284 }