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Linux/security/keys/user_defined.c

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  1 /* user_defined.c: user defined key type
  2  *
  3  * Copyright (C) 2004 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 
 12 #include <linux/module.h>
 13 #include <linux/init.h>
 14 #include <linux/slab.h>
 15 #include <linux/seq_file.h>
 16 #include <linux/err.h>
 17 #include <keys/user-type.h>
 18 #include <asm/uaccess.h>
 19 #include "internal.h"
 20 
 21 static int logon_vet_description(const char *desc);
 22 
 23 /*
 24  * user defined keys take an arbitrary string as the description and an
 25  * arbitrary blob of data as the payload
 26  */
 27 struct key_type key_type_user = {
 28         .name           = "user",
 29         .instantiate    = user_instantiate,
 30         .update         = user_update,
 31         .match          = user_match,
 32         .revoke         = user_revoke,
 33         .destroy        = user_destroy,
 34         .describe       = user_describe,
 35         .read           = user_read,
 36 };
 37 
 38 EXPORT_SYMBOL_GPL(key_type_user);
 39 
 40 /*
 41  * This key type is essentially the same as key_type_user, but it does
 42  * not define a .read op. This is suitable for storing username and
 43  * password pairs in the keyring that you do not want to be readable
 44  * from userspace.
 45  */
 46 struct key_type key_type_logon = {
 47         .name                   = "logon",
 48         .instantiate            = user_instantiate,
 49         .update                 = user_update,
 50         .match                  = user_match,
 51         .revoke                 = user_revoke,
 52         .destroy                = user_destroy,
 53         .describe               = user_describe,
 54         .vet_description        = logon_vet_description,
 55 };
 56 EXPORT_SYMBOL_GPL(key_type_logon);
 57 
 58 /*
 59  * instantiate a user defined key
 60  */
 61 int user_instantiate(struct key *key, const void *data, size_t datalen)
 62 {
 63         struct user_key_payload *upayload;
 64         int ret;
 65 
 66         ret = -EINVAL;
 67         if (datalen <= 0 || datalen > 32767 || !data)
 68                 goto error;
 69 
 70         ret = key_payload_reserve(key, datalen);
 71         if (ret < 0)
 72                 goto error;
 73 
 74         ret = -ENOMEM;
 75         upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
 76         if (!upayload)
 77                 goto error;
 78 
 79         /* attach the data */
 80         upayload->datalen = datalen;
 81         memcpy(upayload->data, data, datalen);
 82         rcu_assign_keypointer(key, upayload);
 83         ret = 0;
 84 
 85 error:
 86         return ret;
 87 }
 88 
 89 EXPORT_SYMBOL_GPL(user_instantiate);
 90 
 91 /*
 92  * update a user defined key
 93  * - the key's semaphore is write-locked
 94  */
 95 int user_update(struct key *key, const void *data, size_t datalen)
 96 {
 97         struct user_key_payload *upayload, *zap;
 98         int ret;
 99 
100         ret = -EINVAL;
101         if (datalen <= 0 || datalen > 32767 || !data)
102                 goto error;
103 
104         /* construct a replacement payload */
105         ret = -ENOMEM;
106         upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
107         if (!upayload)
108                 goto error;
109 
110         upayload->datalen = datalen;
111         memcpy(upayload->data, data, datalen);
112 
113         /* check the quota and attach the new data */
114         zap = upayload;
115 
116         ret = key_payload_reserve(key, datalen);
117 
118         if (ret == 0) {
119                 /* attach the new data, displacing the old */
120                 zap = key->payload.data;
121                 rcu_assign_keypointer(key, upayload);
122                 key->expiry = 0;
123         }
124 
125         if (zap)
126                 kfree_rcu(zap, rcu);
127 
128 error:
129         return ret;
130 }
131 
132 EXPORT_SYMBOL_GPL(user_update);
133 
134 /*
135  * match users on their name
136  */
137 int user_match(const struct key *key, const void *description)
138 {
139         return strcmp(key->description, description) == 0;
140 }
141 
142 EXPORT_SYMBOL_GPL(user_match);
143 
144 /*
145  * dispose of the links from a revoked keyring
146  * - called with the key sem write-locked
147  */
148 void user_revoke(struct key *key)
149 {
150         struct user_key_payload *upayload = key->payload.data;
151 
152         /* clear the quota */
153         key_payload_reserve(key, 0);
154 
155         if (upayload) {
156                 rcu_assign_keypointer(key, NULL);
157                 kfree_rcu(upayload, rcu);
158         }
159 }
160 
161 EXPORT_SYMBOL(user_revoke);
162 
163 /*
164  * dispose of the data dangling from the corpse of a user key
165  */
166 void user_destroy(struct key *key)
167 {
168         struct user_key_payload *upayload = key->payload.data;
169 
170         kfree(upayload);
171 }
172 
173 EXPORT_SYMBOL_GPL(user_destroy);
174 
175 /*
176  * describe the user key
177  */
178 void user_describe(const struct key *key, struct seq_file *m)
179 {
180         seq_puts(m, key->description);
181         if (key_is_instantiated(key))
182                 seq_printf(m, ": %u", key->datalen);
183 }
184 
185 EXPORT_SYMBOL_GPL(user_describe);
186 
187 /*
188  * read the key data
189  * - the key's semaphore is read-locked
190  */
191 long user_read(const struct key *key, char __user *buffer, size_t buflen)
192 {
193         struct user_key_payload *upayload;
194         long ret;
195 
196         upayload = rcu_dereference_key(key);
197         ret = upayload->datalen;
198 
199         /* we can return the data as is */
200         if (buffer && buflen > 0) {
201                 if (buflen > upayload->datalen)
202                         buflen = upayload->datalen;
203 
204                 if (copy_to_user(buffer, upayload->data, buflen) != 0)
205                         ret = -EFAULT;
206         }
207 
208         return ret;
209 }
210 
211 EXPORT_SYMBOL_GPL(user_read);
212 
213 /* Vet the description for a "logon" key */
214 static int logon_vet_description(const char *desc)
215 {
216         char *p;
217 
218         /* require a "qualified" description string */
219         p = strchr(desc, ':');
220         if (!p)
221                 return -EINVAL;
222 
223         /* also reject description with ':' as first char */
224         if (p == desc)
225                 return -EINVAL;
226 
227         return 0;
228 }
229 

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