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/user-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 = key->payload.data[0];
  73
  74         seq_puts(m, "key:");
  75         seq_puts(m, key->description);
  76         if (key_is_instantiated(key))
  77                 seq_printf(m, " pid:%d ci:%zu", rka->pid, rka->callout_len);
  78 }
  79
  80 /*
  81  * Read the callout_info data (retrieves the callout information).
  82  * - the key's semaphore is read-locked
  83  */
  84 static long request_key_auth_read(const struct key *key,
  85                                   char __user *buffer, size_t buflen)
  86 {
  87         struct request_key_auth *rka = key->payload.data[0];
  88         size_t datalen;
  89         long ret;
  90
  91         datalen = rka->callout_len;
  92         ret = datalen;
  93
  94         /* we can return the data as is */
  95         if (buffer && buflen > 0) {
  96                 if (buflen > datalen)
  97                         buflen = datalen;
  98
  99                 if (copy_to_user(buffer, rka->callout_info, buflen) != 0)
 100                         ret = -EFAULT;
 101         }
 102
 103         return ret;
 104 }
 105
 106 /*
 107  * Handle revocation of an authorisation token key.
 108  *
 109  * Called with the key sem write-locked.
 110  */
 111 static void request_key_auth_revoke(struct key *key)
 112 {
 113         struct request_key_auth *rka = key->payload.data[0];
 114
 115         kenter("{%d}", key->serial);
 116
 117         if (rka->cred) {
 118                 put_cred(rka->cred);
 119                 rka->cred = NULL;
 120         }
 121 }
 122
 123 static void free_request_key_auth(struct request_key_auth *rka)
 124 {
 125         if (!rka)
 126                 return;
 127         key_put(rka->target_key);
 128         key_put(rka->dest_keyring);
 129         if (rka->cred)
 130                 put_cred(rka->cred);
 131         kfree(rka->callout_info);
 132         kfree(rka);
 133 }
 134
 135 /*
 136  * Destroy an instantiation authorisation token key.
 137  */
 138 static void request_key_auth_destroy(struct key *key)
 139 {
 140         struct request_key_auth *rka = key->payload.data[0];
 141
 142         kenter("{%d}", key->serial);
 143
 144         free_request_key_auth(rka);
 145 }
 146
 147 /*
 148  * Create an authorisation token for /sbin/request-key or whoever to gain
 149  * access to the caller's security data.
 150  */
 151 struct key *request_key_auth_new(struct key *target, const void *callout_info,
 152                                  size_t callout_len, struct key *dest_keyring)
 153 {
 154         struct request_key_auth *rka, *irka;
 155         const struct cred *cred = current->cred;
 156         struct key *authkey = NULL;
 157         char desc[20];
 158         int ret = -ENOMEM;
 159
 160         kenter("%d,", target->serial);
 161
 162         /* allocate a auth record */
 163         rka = kzalloc(sizeof(*rka), GFP_KERNEL);
 164         if (!rka)
 165                 goto error;
 166         rka->callout_info = kmalloc(callout_len, GFP_KERNEL);
 167         if (!rka->callout_info)
 168                 goto error_free_rka;
 169
 170         /* see if the calling process is already servicing the key request of
 171          * another process */
 172         if (cred->request_key_auth) {
 173                 /* it is - use that instantiation context here too */
 174                 down_read(&cred->request_key_auth->sem);
 175
 176                 /* if the auth key has been revoked, then the key we're
 177                  * servicing is already instantiated */
 178                 if (test_bit(KEY_FLAG_REVOKED,
 179                              &cred->request_key_auth->flags)) {
 180                         up_read(&cred->request_key_auth->sem);
 181                         ret = -EKEYREVOKED;
 182                         goto error_free_rka;
 183                 }
 184
 185                 irka = cred->request_key_auth->payload.data[0];
 186                 rka->cred = get_cred(irka->cred);
 187                 rka->pid = irka->pid;
 188
 189                 up_read(&cred->request_key_auth->sem);
 190         }
 191         else {
 192                 /* it isn't - use this process as the context */
 193                 rka->cred = get_cred(cred);
 194                 rka->pid = current->pid;
 195         }
 196
 197         rka->target_key = key_get(target);
 198         rka->dest_keyring = key_get(dest_keyring);
 199         memcpy(rka->callout_info, callout_info, callout_len);
 200         rka->callout_len = callout_len;
 201
 202         /* allocate the auth key */
 203         sprintf(desc, "%x", target->serial);
 204
 205         authkey = key_alloc(&key_type_request_key_auth, desc,
 206                             cred->fsuid, cred->fsgid, cred,
 207                             KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH |
 208                             KEY_USR_VIEW, KEY_ALLOC_NOT_IN_QUOTA, NULL);
 209         if (IS_ERR(authkey)) {
 210                 ret = PTR_ERR(authkey);
 211                 goto error_free_rka;
 212         }
 213
 214         /* construct the auth key */
 215         ret = key_instantiate_and_link(authkey, rka, 0, NULL, NULL);
 216         if (ret < 0)
 217                 goto error_put_authkey;
 218
 219         kleave(" = {%d,%d}", authkey->serial, refcount_read(&authkey->usage));
 220         return authkey;
 221
 222 error_put_authkey:
 223         key_put(authkey);
 224 error_free_rka:
 225         free_request_key_auth(rka);
 226 error:
 227         kleave("= %d", ret);
 228         return ERR_PTR(ret);
 229 }
 230
 231 /*
 232  * Search the current process's keyrings for the authorisation key for
 233  * instantiation of a key.
 234  */
 235 struct key *key_get_instantiation_authkey(key_serial_t target_id)
 236 {
 237         char description[16];
 238         struct keyring_search_context ctx = {
 239                 .index_key.type         = &key_type_request_key_auth,
 240                 .index_key.description  = description,
 241                 .cred                   = current_cred(),
 242                 .match_data.cmp         = key_default_cmp,
 243                 .match_data.raw_data    = description,
 244                 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
 245                 .flags                  = KEYRING_SEARCH_DO_STATE_CHECK,
 246         };
 247         struct key *authkey;
 248         key_ref_t authkey_ref;
 249
 250         sprintf(description, "%x", target_id);
 251
 252         authkey_ref = search_process_keyrings(&ctx);
 253
 254         if (IS_ERR(authkey_ref)) {
 255                 authkey = ERR_CAST(authkey_ref);
 256                 if (authkey == ERR_PTR(-EAGAIN))
 257                         authkey = ERR_PTR(-ENOKEY);
 258                 goto error;
 259         }
 260
 261         authkey = key_ref_to_ptr(authkey_ref);
 262         if (test_bit(KEY_FLAG_REVOKED, &authkey->flags)) {
 263                 key_put(authkey);
 264                 authkey = ERR_PTR(-EKEYREVOKED);
 265         }
 266
 267 error:
 268         return authkey;
 269 }