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 *, 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 *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 memcpy(buffer, rka->callout_info, buflen); 101 } 102 103 return ret; 104 } 105 106 static void free_request_key_auth(struct request_key_auth *rka) 107 { 108 if (!rka) 109 return; 110 key_put(rka->target_key); 111 key_put(rka->dest_keyring); 112 if (rka->cred) 113 put_cred(rka->cred); 114 kfree(rka->callout_info); 115 kfree(rka); 116 } 117 118 /* 119 * Dispose of the request_key_auth record under RCU conditions 120 */ 121 static void request_key_auth_rcu_disposal(struct rcu_head *rcu) 122 { 123 struct request_key_auth *rka = 124 container_of(rcu, struct request_key_auth, rcu); 125 126 free_request_key_auth(rka); 127 } 128 129 /* 130 * Handle revocation of an authorisation token key. 131 * 132 * Called with the key sem write-locked. 133 */ 134 static void request_key_auth_revoke(struct key *key) 135 { 136 struct request_key_auth *rka = dereference_key_locked(key); 137 138 kenter("{%d}", key->serial); 139 rcu_assign_keypointer(key, NULL); 140 call_rcu(&rka->rcu, request_key_auth_rcu_disposal); 141 } 142 143 /* 144 * Destroy an instantiation authorisation token key. 145 */ 146 static void request_key_auth_destroy(struct key *key) 147 { 148 struct request_key_auth *rka = rcu_access_pointer(key->payload.rcu_data0); 149 150 kenter("{%d}", key->serial); 151 if (rka) { 152 rcu_assign_keypointer(key, NULL); 153 call_rcu(&rka->rcu, request_key_auth_rcu_disposal); 154 } 155 } 156 157 /* 158 * Create an authorisation token for /sbin/request-key or whoever to gain 159 * access to the caller's security data. 160 */ 161 struct key *request_key_auth_new(struct key *target, const char *op, 162 const void *callout_info, size_t callout_len, 163 struct key *dest_keyring) 164 { 165 struct request_key_auth *rka, *irka; 166 const struct cred *cred = current_cred(); 167 struct key *authkey = NULL; 168 char desc[20]; 169 int ret = -ENOMEM; 170 171 kenter("%d,", target->serial); 172 173 /* allocate a auth record */ 174 rka = kzalloc(sizeof(*rka), GFP_KERNEL); 175 if (!rka) 176 goto error; 177 rka->callout_info = kmemdup(callout_info, callout_len, GFP_KERNEL); 178 if (!rka->callout_info) 179 goto error_free_rka; 180 rka->callout_len = callout_len; 181 strscpy(rka->op, op, sizeof(rka->op)); 182 183 /* see if the calling process is already servicing the key request of 184 * another process */ 185 if (cred->request_key_auth) { 186 /* it is - use that instantiation context here too */ 187 down_read(&cred->request_key_auth->sem); 188 189 /* if the auth key has been revoked, then the key we're 190 * servicing is already instantiated */ 191 if (test_bit(KEY_FLAG_REVOKED, 192 &cred->request_key_auth->flags)) { 193 up_read(&cred->request_key_auth->sem); 194 ret = -EKEYREVOKED; 195 goto error_free_rka; 196 } 197 198 irka = cred->request_key_auth->payload.data[0]; 199 rka->cred = get_cred(irka->cred); 200 rka->pid = irka->pid; 201 202 up_read(&cred->request_key_auth->sem); 203 } 204 else { 205 /* it isn't - use this process as the context */ 206 rka->cred = get_cred(cred); 207 rka->pid = current->pid; 208 } 209 210 rka->target_key = key_get(target); 211 rka->dest_keyring = key_get(dest_keyring); 212 213 /* allocate the auth key */ 214 sprintf(desc, "%x", target->serial); 215 216 authkey = key_alloc(&key_type_request_key_auth, desc, 217 cred->fsuid, cred->fsgid, cred, 218 KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH | KEY_POS_LINK | 219 KEY_USR_VIEW, KEY_ALLOC_NOT_IN_QUOTA, NULL); 220 if (IS_ERR(authkey)) { 221 ret = PTR_ERR(authkey); 222 goto error_free_rka; 223 } 224 225 /* construct the auth key */ 226 ret = key_instantiate_and_link(authkey, rka, 0, NULL, NULL); 227 if (ret < 0) 228 goto error_put_authkey; 229 230 kleave(" = {%d,%d}", authkey->serial, refcount_read(&authkey->usage)); 231 return authkey; 232 233 error_put_authkey: 234 key_put(authkey); 235 error_free_rka: 236 free_request_key_auth(rka); 237 error: 238 kleave("= %d", ret); 239 return ERR_PTR(ret); 240 } 241 242 /* 243 * Search the current process's keyrings for the authorisation key for 244 * instantiation of a key. 245 */ 246 struct key *key_get_instantiation_authkey(key_serial_t target_id) 247 { 248 char description[16]; 249 struct keyring_search_context ctx = { 250 .index_key.type = &key_type_request_key_auth, 251 .index_key.description = description, 252 .cred = current_cred(), 253 .match_data.cmp = key_default_cmp, 254 .match_data.raw_data = description, 255 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT, 256 .flags = (KEYRING_SEARCH_DO_STATE_CHECK | 257 KEYRING_SEARCH_RECURSE), 258 }; 259 struct key *authkey; 260 key_ref_t authkey_ref; 261 262 ctx.index_key.desc_len = sprintf(description, "%x", target_id); 263 264 rcu_read_lock(); 265 authkey_ref = search_process_keyrings_rcu(&ctx); 266 rcu_read_unlock(); 267 268 if (IS_ERR(authkey_ref)) { 269 authkey = ERR_CAST(authkey_ref); 270 if (authkey == ERR_PTR(-EAGAIN)) 271 authkey = ERR_PTR(-ENOKEY); 272 goto error; 273 } 274 275 authkey = key_ref_to_ptr(authkey_ref); 276 if (test_bit(KEY_FLAG_REVOKED, &authkey->flags)) { 277 key_put(authkey); 278 authkey = ERR_PTR(-EKEYREVOKED); 279 } 280 281 error: 282 return authkey; 283 } 284