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