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 /* 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 seq_puts(m, "key:"); 70 seq_puts(m, key->description); 71 if (key_is_positive(key)) 72 seq_printf(m, " pid:%d ci:%zu", rka->pid, rka->callout_len); 73 } 74 75 /* 76 * Read the callout_info data (retrieves the callout information). 77 * - the key's semaphore is read-locked 78 */ 79 static long request_key_auth_read(const struct key *key, 80 char __user *buffer, size_t buflen) 81 { 82 struct request_key_auth *rka = dereference_key_locked(key); 83 size_t datalen; 84 long ret; 85 86 datalen = rka->callout_len; 87 ret = datalen; 88 89 /* we can return the data as is */ 90 if (buffer && buflen > 0) { 91 if (buflen > datalen) 92 buflen = datalen; 93 94 if (copy_to_user(buffer, rka->callout_info, buflen) != 0) 95 ret = -EFAULT; 96 } 97 98 return ret; 99 } 100 101 static void free_request_key_auth(struct request_key_auth *rka) 102 { 103 if (!rka) 104 return; 105 key_put(rka->target_key); 106 key_put(rka->dest_keyring); 107 if (rka->cred) 108 put_cred(rka->cred); 109 kfree(rka->callout_info); 110 kfree(rka); 111 } 112 113 /* 114 * Dispose of the request_key_auth record under RCU conditions 115 */ 116 static void request_key_auth_rcu_disposal(struct rcu_head *rcu) 117 { 118 struct request_key_auth *rka = 119 container_of(rcu, struct request_key_auth, rcu); 120 121 free_request_key_auth(rka); 122 } 123 124 /* 125 * Handle revocation of an authorisation token key. 126 * 127 * Called with the key sem write-locked. 128 */ 129 static void request_key_auth_revoke(struct key *key) 130 { 131 struct request_key_auth *rka = dereference_key_locked(key); 132 133 kenter("{%d}", key->serial); 134 rcu_assign_keypointer(key, NULL); 135 call_rcu(&rka->rcu, request_key_auth_rcu_disposal); 136 } 137 138 /* 139 * Destroy an instantiation authorisation token key. 140 */ 141 static void request_key_auth_destroy(struct key *key) 142 { 143 struct request_key_auth *rka = rcu_access_pointer(key->payload.rcu_data0); 144 145 kenter("{%d}", key->serial); 146 if (rka) { 147 rcu_assign_keypointer(key, NULL); 148 call_rcu(&rka->rcu, request_key_auth_rcu_disposal); 149 } 150 } 151 152 /* 153 * Create an authorisation token for /sbin/request-key or whoever to gain 154 * access to the caller's security data. 155 */ 156 struct key *request_key_auth_new(struct key *target, const char *op, 157 const void *callout_info, size_t callout_len, 158 struct key *dest_keyring) 159 { 160 struct request_key_auth *rka, *irka; 161 const struct cred *cred = current_cred(); 162 struct key *authkey = NULL; 163 char desc[20]; 164 int ret = -ENOMEM; 165 166 kenter("%d,", target->serial); 167 168 /* allocate a auth record */ 169 rka = kzalloc(sizeof(*rka), GFP_KERNEL); 170 if (!rka) 171 goto error; 172 rka->callout_info = kmemdup(callout_info, callout_len, GFP_KERNEL); 173 if (!rka->callout_info) 174 goto error_free_rka; 175 rka->callout_len = callout_len; 176 strlcpy(rka->op, op, sizeof(rka->op)); 177 178 /* see if the calling process is already servicing the key request of 179 * another process */ 180 if (cred->request_key_auth) { 181 /* it is - use that instantiation context here too */ 182 down_read(&cred->request_key_auth->sem); 183 184 /* if the auth key has been revoked, then the key we're 185 * servicing is already instantiated */ 186 if (test_bit(KEY_FLAG_REVOKED, 187 &cred->request_key_auth->flags)) { 188 up_read(&cred->request_key_auth->sem); 189 ret = -EKEYREVOKED; 190 goto error_free_rka; 191 } 192 193 irka = cred->request_key_auth->payload.data[0]; 194 rka->cred = get_cred(irka->cred); 195 rka->pid = irka->pid; 196 197 up_read(&cred->request_key_auth->sem); 198 } 199 else { 200 /* it isn't - use this process as the context */ 201 rka->cred = get_cred(cred); 202 rka->pid = current->pid; 203 } 204 205 rka->target_key = key_get(target); 206 rka->dest_keyring = key_get(dest_keyring); 207 208 /* allocate the auth key */ 209 sprintf(desc, "%x", target->serial); 210 211 authkey = key_alloc(&key_type_request_key_auth, desc, 212 cred->fsuid, cred->fsgid, cred, 213 KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH | KEY_POS_LINK | 214 KEY_USR_VIEW, KEY_ALLOC_NOT_IN_QUOTA, NULL); 215 if (IS_ERR(authkey)) { 216 ret = PTR_ERR(authkey); 217 goto error_free_rka; 218 } 219 220 /* construct the auth key */ 221 ret = key_instantiate_and_link(authkey, rka, 0, NULL, NULL); 222 if (ret < 0) 223 goto error_put_authkey; 224 225 kleave(" = {%d,%d}", authkey->serial, refcount_read(&authkey->usage)); 226 return authkey; 227 228 error_put_authkey: 229 key_put(authkey); 230 error_free_rka: 231 free_request_key_auth(rka); 232 error: 233 kleave("= %d", ret); 234 return ERR_PTR(ret); 235 } 236 237 /* 238 * Search the current process's keyrings for the authorisation key for 239 * instantiation of a key. 240 */ 241 struct key *key_get_instantiation_authkey(key_serial_t target_id) 242 { 243 char description[16]; 244 struct keyring_search_context ctx = { 245 .index_key.type = &key_type_request_key_auth, 246 .index_key.description = description, 247 .cred = current_cred(), 248 .match_data.cmp = key_default_cmp, 249 .match_data.raw_data = description, 250 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT, 251 .flags = (KEYRING_SEARCH_DO_STATE_CHECK | 252 KEYRING_SEARCH_RECURSE), 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 rcu_read_lock(); 260 authkey_ref = search_process_keyrings_rcu(&ctx); 261 rcu_read_unlock(); 262 263 if (IS_ERR(authkey_ref)) { 264 authkey = ERR_CAST(authkey_ref); 265 if (authkey == ERR_PTR(-EAGAIN)) 266 authkey = ERR_PTR(-ENOKEY); 267 goto error; 268 } 269 270 authkey = key_ref_to_ptr(authkey_ref); 271 if (test_bit(KEY_FLAG_REVOKED, &authkey->flags)) { 272 key_put(authkey); 273 authkey = ERR_PTR(-EKEYREVOKED); 274 } 275 276 error: 277 return authkey; 278 } 279