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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         .preparse               = user_preparse,
 30         .free_preparse          = user_free_preparse,
 31         .instantiate            = generic_key_instantiate,
 32         .update                 = user_update,
 33         .revoke                 = user_revoke,
 34         .destroy                = user_destroy,
 35         .describe               = user_describe,
 36         .read                   = user_read,
 37 };
 38 
 39 EXPORT_SYMBOL_GPL(key_type_user);
 40 
 41 /*
 42  * This key type is essentially the same as key_type_user, but it does
 43  * not define a .read op. This is suitable for storing username and
 44  * password pairs in the keyring that you do not want to be readable
 45  * from userspace.
 46  */
 47 struct key_type key_type_logon = {
 48         .name                   = "logon",
 49         .preparse               = user_preparse,
 50         .free_preparse          = user_free_preparse,
 51         .instantiate            = generic_key_instantiate,
 52         .update                 = user_update,
 53         .revoke                 = user_revoke,
 54         .destroy                = user_destroy,
 55         .describe               = user_describe,
 56         .vet_description        = logon_vet_description,
 57 };
 58 EXPORT_SYMBOL_GPL(key_type_logon);
 59 
 60 /*
 61  * Preparse a user defined key payload
 62  */
 63 int user_preparse(struct key_preparsed_payload *prep)
 64 {
 65         struct user_key_payload *upayload;
 66         size_t datalen = prep->datalen;
 67 
 68         if (datalen <= 0 || datalen > 32767 || !prep->data)
 69                 return -EINVAL;
 70 
 71         upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
 72         if (!upayload)
 73                 return -ENOMEM;
 74 
 75         /* attach the data */
 76         prep->quotalen = datalen;
 77         prep->payload.data[0] = upayload;
 78         upayload->datalen = datalen;
 79         memcpy(upayload->data, prep->data, datalen);
 80         return 0;
 81 }
 82 EXPORT_SYMBOL_GPL(user_preparse);
 83 
 84 /*
 85  * Free a preparse of a user defined key payload
 86  */
 87 void user_free_preparse(struct key_preparsed_payload *prep)
 88 {
 89         kfree(prep->payload.data[0]);
 90 }
 91 EXPORT_SYMBOL_GPL(user_free_preparse);
 92 
 93 /*
 94  * update a user defined key
 95  * - the key's semaphore is write-locked
 96  */
 97 int user_update(struct key *key, struct key_preparsed_payload *prep)
 98 {
 99         struct user_key_payload *zap = NULL;
100         int ret;
101 
102         /* check the quota and attach the new data */
103         ret = key_payload_reserve(key, prep->datalen);
104         if (ret < 0)
105                 return ret;
106 
107         /* attach the new data, displacing the old */
108         key->expiry = prep->expiry;
109         if (!test_bit(KEY_FLAG_NEGATIVE, &key->flags))
110                 zap = rcu_dereference_key(key);
111         rcu_assign_keypointer(key, prep->payload.data[0]);
112         prep->payload.data[0] = NULL;
113 
114         if (zap)
115                 kfree_rcu(zap, rcu);
116         return ret;
117 }
118 EXPORT_SYMBOL_GPL(user_update);
119 
120 /*
121  * dispose of the links from a revoked keyring
122  * - called with the key sem write-locked
123  */
124 void user_revoke(struct key *key)
125 {
126         struct user_key_payload *upayload = key->payload.data[0];
127 
128         /* clear the quota */
129         key_payload_reserve(key, 0);
130 
131         if (upayload) {
132                 rcu_assign_keypointer(key, NULL);
133                 kfree_rcu(upayload, rcu);
134         }
135 }
136 
137 EXPORT_SYMBOL(user_revoke);
138 
139 /*
140  * dispose of the data dangling from the corpse of a user key
141  */
142 void user_destroy(struct key *key)
143 {
144         struct user_key_payload *upayload = key->payload.data[0];
145 
146         kfree(upayload);
147 }
148 
149 EXPORT_SYMBOL_GPL(user_destroy);
150 
151 /*
152  * describe the user key
153  */
154 void user_describe(const struct key *key, struct seq_file *m)
155 {
156         seq_puts(m, key->description);
157         if (key_is_instantiated(key))
158                 seq_printf(m, ": %u", key->datalen);
159 }
160 
161 EXPORT_SYMBOL_GPL(user_describe);
162 
163 /*
164  * read the key data
165  * - the key's semaphore is read-locked
166  */
167 long user_read(const struct key *key, char __user *buffer, size_t buflen)
168 {
169         const struct user_key_payload *upayload;
170         long ret;
171 
172         upayload = user_key_payload(key);
173         ret = upayload->datalen;
174 
175         /* we can return the data as is */
176         if (buffer && buflen > 0) {
177                 if (buflen > upayload->datalen)
178                         buflen = upayload->datalen;
179 
180                 if (copy_to_user(buffer, upayload->data, buflen) != 0)
181                         ret = -EFAULT;
182         }
183 
184         return ret;
185 }
186 
187 EXPORT_SYMBOL_GPL(user_read);
188 
189 /* Vet the description for a "logon" key */
190 static int logon_vet_description(const char *desc)
191 {
192         char *p;
193 
194         /* require a "qualified" description string */
195         p = strchr(desc, ':');
196         if (!p)
197                 return -EINVAL;
198 
199         /* also reject description with ':' as first char */
200         if (p == desc)
201                 return -EINVAL;
202 
203         return 0;
204 }
205 

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