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/pid.h> 13 #include <linux/proc_fs.h> 14 #include <linux/seq_file.h> 15 #include <linux/slab.h> 16 #include <linux/uaccess.h> 17 #include "internal.h" 18 #include <keys/request_key_auth-type.h> 19 20 static int request_key_auth_preparse(struct key_preparsed_payload *); 21 static void request_key_auth_free_preparse(struct key_preparsed_payload *); 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 *, size_t); 28 static void request_key_auth_rcu_disposal(struct rcu_head *); 29 30 /* 31 * The request-key authorisation key type definition. 32 */ 33 struct key_type key_type_request_key_auth = { 34 .name = ".request_key_auth", 35 .def_datalen = sizeof(struct request_key_auth), 36 .preparse = request_key_auth_preparse, 37 .free_preparse = request_key_auth_free_preparse, 38 .instantiate = request_key_auth_instantiate, 39 .describe = request_key_auth_describe, 40 .revoke = request_key_auth_revoke, 41 .destroy = request_key_auth_destroy, 42 .read = request_key_auth_read, 43 }; 44 45 static int request_key_auth_preparse(struct key_preparsed_payload *prep) 46 { 47 return 0; 48 } 49 50 static void request_key_auth_free_preparse(struct key_preparsed_payload *prep) 51 { 52 } 53 54 /* 55 * Instantiate a request-key authorisation key. 56 */ 57 static int request_key_auth_instantiate(struct key *key, 58 struct key_preparsed_payload *prep) 59 { 60 rcu_assign_keypointer(key, (struct request_key_auth *)prep->data); 61 return 0; 62 } 63 64 /* 65 * Describe an authorisation token. 66 */ 67 static void request_key_auth_describe(const struct key *key, 68 struct seq_file *m) 69 { 70 struct request_key_auth *rka = dereference_key_rcu(key); 71 72 if (!rka) 73 return; 74 75 seq_puts(m, "key:"); 76 seq_puts(m, key->description); 77 if (key_is_positive(key)) 78 seq_printf(m, " pid:%d ci:%zu", 79 pid_nr_ns(rka->pid, 80 proc_pid_ns(file_inode(m->file)->i_sb)), 81 rka->callout_len); 82 } 83 84 /* 85 * Read the callout_info data (retrieves the callout information). 86 * - the key's semaphore is read-locked 87 */ 88 static long request_key_auth_read(const struct key *key, 89 char *buffer, size_t buflen) 90 { 91 struct request_key_auth *rka = dereference_key_locked(key); 92 size_t datalen; 93 long ret; 94 95 if (!rka) 96 return -EKEYREVOKED; 97 98 datalen = rka->callout_len; 99 ret = datalen; 100 101 /* we can return the data as is */ 102 if (buffer && buflen > 0) { 103 if (buflen > datalen) 104 buflen = datalen; 105 106 memcpy(buffer, rka->callout_info, buflen); 107 } 108 109 return ret; 110 } 111 112 static void free_request_key_auth(struct request_key_auth *rka) 113 { 114 if (!rka) 115 return; 116 key_put(rka->target_key); 117 key_put(rka->dest_keyring); 118 if (rka->cred) 119 put_cred(rka->cred); 120 kfree(rka->callout_info); 121 put_pid(rka->pid); 122 kfree(rka); 123 } 124 125 /* 126 * Take a reference to the request-key authorisation payload so callers can 127 * drop authkey->sem before doing operations that may sleep. 128 */ 129 struct request_key_auth *request_key_auth_get(struct key *authkey) 130 { 131 struct request_key_auth *rka; 132 133 down_read(&authkey->sem); 134 rka = dereference_key_locked(authkey); 135 if (rka && !test_bit(KEY_FLAG_REVOKED, &authkey->flags)) 136 refcount_inc(&rka->usage); 137 else 138 rka = NULL; 139 up_read(&authkey->sem); 140 141 return rka; 142 } 143 144 void request_key_auth_put(struct request_key_auth *rka) 145 { 146 if (rka && refcount_dec_and_test(&rka->usage)) 147 call_rcu(&rka->rcu, request_key_auth_rcu_disposal); 148 } 149 150 /* 151 * Dispose of the request_key_auth record under RCU conditions 152 */ 153 static void request_key_auth_rcu_disposal(struct rcu_head *rcu) 154 { 155 struct request_key_auth *rka = 156 container_of(rcu, struct request_key_auth, rcu); 157 158 free_request_key_auth(rka); 159 } 160 161 /* 162 * Handle revocation of an authorisation token key. 163 * 164 * Called with the key sem write-locked. 165 */ 166 static void request_key_auth_revoke(struct key *key) 167 { 168 struct request_key_auth *rka = dereference_key_locked(key); 169 170 kenter("{%d}", key->serial); 171 if (!rka) 172 return; 173 rcu_assign_keypointer(key, NULL); 174 request_key_auth_put(rka); 175 } 176 177 /* 178 * Destroy an instantiation authorisation token key. 179 */ 180 static void request_key_auth_destroy(struct key *key) 181 { 182 struct request_key_auth *rka = rcu_access_pointer(key->payload.rcu_data0); 183 184 kenter("{%d}", key->serial); 185 if (rka) { 186 rcu_assign_keypointer(key, NULL); 187 request_key_auth_put(rka); 188 } 189 } 190 191 /* 192 * Create an authorisation token for /sbin/request-key or whoever to gain 193 * access to the caller's security data. 194 */ 195 struct key *request_key_auth_new(struct key *target, const char *op, 196 const void *callout_info, size_t callout_len, 197 struct key *dest_keyring) 198 { 199 struct request_key_auth *rka, *irka; 200 const struct cred *cred = current_cred(); 201 struct key *authkey = NULL; 202 char desc[20]; 203 int ret = -ENOMEM; 204 205 kenter("%d,", target->serial); 206 207 /* allocate a auth record */ 208 rka = kzalloc_obj(*rka); 209 if (!rka) 210 goto error; 211 refcount_set(&rka->usage, 1); 212 rka->callout_info = kmemdup(callout_info, callout_len, GFP_KERNEL); 213 if (!rka->callout_info) 214 goto error_free_rka; 215 rka->callout_len = callout_len; 216 strscpy(rka->op, op, sizeof(rka->op)); 217 218 /* see if the calling process is already servicing the key request of 219 * another process */ 220 if (cred->request_key_auth) { 221 /* it is - use that instantiation context here too */ 222 down_read(&cred->request_key_auth->sem); 223 224 /* if the auth key has been revoked, then the key we're 225 * servicing is already instantiated */ 226 if (test_bit(KEY_FLAG_REVOKED, 227 &cred->request_key_auth->flags)) { 228 up_read(&cred->request_key_auth->sem); 229 ret = -EKEYREVOKED; 230 goto error_free_rka; 231 } 232 233 irka = cred->request_key_auth->payload.data[0]; 234 rka->cred = get_cred(irka->cred); 235 rka->pid = get_pid(irka->pid); 236 237 up_read(&cred->request_key_auth->sem); 238 } 239 else { 240 /* it isn't - use this process as the context */ 241 rka->cred = get_cred(cred); 242 rka->pid = get_pid(task_pid(current)); 243 } 244 245 rka->target_key = key_get(target); 246 rka->dest_keyring = key_get(dest_keyring); 247 248 /* allocate the auth key */ 249 sprintf(desc, "%x", target->serial); 250 251 authkey = key_alloc(&key_type_request_key_auth, desc, 252 cred->fsuid, cred->fsgid, cred, 253 KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH | KEY_POS_LINK | 254 KEY_USR_VIEW, KEY_ALLOC_NOT_IN_QUOTA, NULL); 255 if (IS_ERR(authkey)) { 256 ret = PTR_ERR(authkey); 257 goto error_free_rka; 258 } 259 260 /* construct the auth key */ 261 ret = key_instantiate_and_link(authkey, rka, 0, NULL, NULL); 262 if (ret < 0) 263 goto error_put_authkey; 264 265 kleave(" = {%d,%d}", authkey->serial, refcount_read(&authkey->usage)); 266 return authkey; 267 268 error_put_authkey: 269 key_put(authkey); 270 error_free_rka: 271 free_request_key_auth(rka); 272 error: 273 kleave("= %d", ret); 274 return ERR_PTR(ret); 275 } 276 277 /* 278 * Search the current process's keyrings for the authorisation key for 279 * instantiation of a key. 280 */ 281 struct key *key_get_instantiation_authkey(key_serial_t target_id) 282 { 283 char description[16]; 284 struct keyring_search_context ctx = { 285 .index_key.type = &key_type_request_key_auth, 286 .index_key.description = description, 287 .cred = current_cred(), 288 .match_data.cmp = key_default_cmp, 289 .match_data.raw_data = description, 290 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT, 291 .flags = (KEYRING_SEARCH_DO_STATE_CHECK | 292 KEYRING_SEARCH_RECURSE), 293 }; 294 struct key *authkey; 295 key_ref_t authkey_ref; 296 297 ctx.index_key.desc_len = sprintf(description, "%x", target_id); 298 299 rcu_read_lock(); 300 authkey_ref = search_process_keyrings_rcu(&ctx); 301 rcu_read_unlock(); 302 303 if (IS_ERR(authkey_ref)) { 304 authkey = ERR_CAST(authkey_ref); 305 if (authkey == ERR_PTR(-EAGAIN)) 306 authkey = ERR_PTR(-ENOKEY); 307 goto error; 308 } 309 310 authkey = key_ref_to_ptr(authkey_ref); 311 if (test_bit(KEY_FLAG_REVOKED, &authkey->flags)) { 312 key_put(authkey); 313 authkey = ERR_PTR(-EKEYREVOKED); 314 } 315 316 error: 317 return authkey; 318 } 319