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 static struct key_acl request_key_auth_acl = { 28 .usage = REFCOUNT_INIT(1), 29 .nr_ace = 2, 30 .possessor_viewable = true, 31 .aces = { 32 KEY_POSSESSOR_ACE(KEY_ACE_VIEW | KEY_ACE_READ | KEY_ACE_SEARCH | 33 KEY_ACE_LINK), 34 KEY_OWNER_ACE(KEY_ACE_VIEW), 35 } 36 }; 37 38 /* 39 * The request-key authorisation key type definition. 40 */ 41 struct key_type key_type_request_key_auth = { 42 .name = ".request_key_auth", 43 .def_datalen = sizeof(struct request_key_auth), 44 .preparse = request_key_auth_preparse, 45 .free_preparse = request_key_auth_free_preparse, 46 .instantiate = request_key_auth_instantiate, 47 .describe = request_key_auth_describe, 48 .revoke = request_key_auth_revoke, 49 .destroy = request_key_auth_destroy, 50 .read = request_key_auth_read, 51 }; 52 53 static int request_key_auth_preparse(struct key_preparsed_payload *prep) 54 { 55 return 0; 56 } 57 58 static void request_key_auth_free_preparse(struct key_preparsed_payload *prep) 59 { 60 } 61 62 /* 63 * Instantiate a request-key authorisation key. 64 */ 65 static int request_key_auth_instantiate(struct key *key, 66 struct key_preparsed_payload *prep) 67 { 68 rcu_assign_keypointer(key, (struct request_key_auth *)prep->data); 69 return 0; 70 } 71 72 /* 73 * Describe an authorisation token. 74 */ 75 static void request_key_auth_describe(const struct key *key, 76 struct seq_file *m) 77 { 78 struct request_key_auth *rka = dereference_key_rcu(key); 79 80 seq_puts(m, "key:"); 81 seq_puts(m, key->description); 82 if (key_is_positive(key)) 83 seq_printf(m, " pid:%d ci:%zu", rka->pid, rka->callout_len); 84 } 85 86 /* 87 * Read the callout_info data (retrieves the callout information). 88 * - the key's semaphore is read-locked 89 */ 90 static long request_key_auth_read(const struct key *key, 91 char __user *buffer, size_t buflen) 92 { 93 struct request_key_auth *rka = dereference_key_locked(key); 94 size_t datalen; 95 long ret; 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 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 kfree(rka); 122 } 123 124 /* 125 * Dispose of the request_key_auth record under RCU conditions 126 */ 127 static void request_key_auth_rcu_disposal(struct rcu_head *rcu) 128 { 129 struct request_key_auth *rka = 130 container_of(rcu, struct request_key_auth, rcu); 131 132 free_request_key_auth(rka); 133 } 134 135 /* 136 * Handle revocation of an authorisation token key. 137 * 138 * Called with the key sem write-locked. 139 */ 140 static void request_key_auth_revoke(struct key *key) 141 { 142 struct request_key_auth *rka = dereference_key_locked(key); 143 144 kenter("{%d}", key->serial); 145 rcu_assign_keypointer(key, NULL); 146 call_rcu(&rka->rcu, request_key_auth_rcu_disposal); 147 } 148 149 /* 150 * Destroy an instantiation authorisation token key. 151 */ 152 static void request_key_auth_destroy(struct key *key) 153 { 154 struct request_key_auth *rka = rcu_access_pointer(key->payload.rcu_data0); 155 156 kenter("{%d}", key->serial); 157 if (rka) { 158 rcu_assign_keypointer(key, NULL); 159 call_rcu(&rka->rcu, request_key_auth_rcu_disposal); 160 } 161 } 162 163 /* 164 * Create an authorisation token for /sbin/request-key or whoever to gain 165 * access to the caller's security data. 166 */ 167 struct key *request_key_auth_new(struct key *target, const char *op, 168 const void *callout_info, size_t callout_len, 169 struct key *dest_keyring) 170 { 171 struct request_key_auth *rka, *irka; 172 const struct cred *cred = current_cred(); 173 struct key *authkey = NULL; 174 char desc[20]; 175 int ret = -ENOMEM; 176 177 kenter("%d,", target->serial); 178 179 /* allocate a auth record */ 180 rka = kzalloc(sizeof(*rka), GFP_KERNEL); 181 if (!rka) 182 goto error; 183 rka->callout_info = kmemdup(callout_info, callout_len, GFP_KERNEL); 184 if (!rka->callout_info) 185 goto error_free_rka; 186 rka->callout_len = callout_len; 187 strlcpy(rka->op, op, sizeof(rka->op)); 188 189 /* see if the calling process is already servicing the key request of 190 * another process */ 191 if (cred->request_key_auth) { 192 /* it is - use that instantiation context here too */ 193 down_read(&cred->request_key_auth->sem); 194 195 /* if the auth key has been revoked, then the key we're 196 * servicing is already instantiated */ 197 if (test_bit(KEY_FLAG_REVOKED, 198 &cred->request_key_auth->flags)) { 199 up_read(&cred->request_key_auth->sem); 200 ret = -EKEYREVOKED; 201 goto error_free_rka; 202 } 203 204 irka = cred->request_key_auth->payload.data[0]; 205 rka->cred = get_cred(irka->cred); 206 rka->pid = irka->pid; 207 208 up_read(&cred->request_key_auth->sem); 209 } 210 else { 211 /* it isn't - use this process as the context */ 212 rka->cred = get_cred(cred); 213 rka->pid = current->pid; 214 } 215 216 rka->target_key = key_get(target); 217 rka->dest_keyring = key_get(dest_keyring); 218 219 /* allocate the auth key */ 220 sprintf(desc, "%x", target->serial); 221 222 authkey = key_alloc(&key_type_request_key_auth, desc, 223 cred->fsuid, cred->fsgid, cred, 224 &request_key_auth_acl, 225 KEY_ALLOC_NOT_IN_QUOTA, NULL); 226 if (IS_ERR(authkey)) { 227 ret = PTR_ERR(authkey); 228 goto error_free_rka; 229 } 230 231 /* construct the auth key */ 232 ret = key_instantiate_and_link(authkey, rka, 0, NULL, NULL); 233 if (ret < 0) 234 goto error_put_authkey; 235 236 kleave(" = {%d,%d}", authkey->serial, refcount_read(&authkey->usage)); 237 return authkey; 238 239 error_put_authkey: 240 key_put(authkey); 241 error_free_rka: 242 free_request_key_auth(rka); 243 error: 244 kleave("= %d", ret); 245 return ERR_PTR(ret); 246 } 247 248 /* 249 * Search the current process's keyrings for the authorisation key for 250 * instantiation of a key. 251 */ 252 struct key *key_get_instantiation_authkey(key_serial_t target_id) 253 { 254 char description[16]; 255 struct keyring_search_context ctx = { 256 .index_key.type = &key_type_request_key_auth, 257 .index_key.description = description, 258 .cred = current_cred(), 259 .match_data.cmp = key_default_cmp, 260 .match_data.raw_data = description, 261 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT, 262 .flags = (KEYRING_SEARCH_DO_STATE_CHECK | 263 KEYRING_SEARCH_RECURSE), 264 }; 265 struct key *authkey; 266 key_ref_t authkey_ref; 267 268 ctx.index_key.desc_len = sprintf(description, "%x", target_id); 269 270 rcu_read_lock(); 271 authkey_ref = search_process_keyrings_rcu(&ctx); 272 rcu_read_unlock(); 273 274 if (IS_ERR(authkey_ref)) { 275 authkey = ERR_CAST(authkey_ref); 276 if (authkey == ERR_PTR(-EAGAIN)) 277 authkey = ERR_PTR(-ENOKEY); 278 goto error; 279 } 280 281 authkey = key_ref_to_ptr(authkey_ref); 282 if (test_bit(KEY_FLAG_REVOKED, &authkey->flags)) { 283 key_put(authkey); 284 authkey = ERR_PTR(-EKEYREVOKED); 285 } 286 287 error: 288 return authkey; 289 } 290