Add relationships to function documentation.
[asterisk/asterisk.git] / funcs / func_aes.c
1 /*
2  * Asterisk -- An open source telephony toolkit.
3  *
4  * Copyright (C) 2009, Digium, Inc.
5  *
6  * See http://www.asterisk.org for more information about
7  * the Asterisk project. Please do not directly contact
8  * any of the maintainers of this project for assistance;
9  * the project provides a web site, mailing lists and IRC
10  * channels for your use.
11  *
12  * This program is free software, distributed under the terms of
13  * the GNU General Public License Version 2. See the LICENSE file
14  * at the top of the source tree.
15  */
16
17 /*! \file
18  *
19  * \brief AES encryption/decryption dialplan functions
20  *
21  * \author David Vossel <dvossel@digium.com>
22  * \ingroup functions
23  */
24
25 /*** MODULEINFO
26         <use>crypto</use>
27  ***/
28
29 #include "asterisk.h"
30
31 ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
32
33 #include "asterisk/module.h"
34 #include "asterisk/pbx.h"
35 #include "asterisk/app.h"
36 #include "asterisk/crypto.h"
37
38 #define AES_BLOCK_SIZE 16
39
40 /*** DOCUMENTATION
41         <function name="AES_ENCRYPT" language="en_US">
42                 <synopsis>
43                         Encrypt a string with AES given a 16 character key.
44                 </synopsis>
45                 <syntax>
46                         <parameter name="key" required="true">
47                                 <para>AES Key</para>
48                         </parameter>
49                         <parameter name="string" required="true">
50                                 <para>Input string</para>
51                         </parameter>
52                 </syntax>
53                 <description>
54                         <para>Returns an AES encrypted string encoded in base64.</para>
55                 </description>
56                 <see-also>
57                         <ref type="function">AES_DECRYPT</ref>
58                         <ref type="function">BASE64_ENCODE</ref>
59                         <ref type="function">BASE64_DECODE</ref>
60                 </see-also>
61         </function>
62         <function name="AES_DECRYPT" language="en_US">
63                 <synopsis>
64                         Decrypt a string encoded in base64 with AES given a 16 character key.
65                 </synopsis>
66                 <syntax>
67                         <parameter name="key" required="true">
68                                 <para>AES Key</para>
69                         </parameter>
70                         <parameter name="string" required="true">
71                                 <para>Input string.</para>
72                         </parameter>
73                 </syntax>
74                 <description>
75                         <para>Returns the plain text string.</para>
76                 </description>
77                 <see-also>
78                         <ref type="function">AES_ENCRYPT</ref>
79                         <ref type="function">BASE64_ENCODE</ref>
80                         <ref type="function">BASE64_DECODE</ref>
81                 </see-also>
82         </function>
83  ***/
84
85
86 static int aes_helper(struct ast_channel *chan, const char *cmd, char *data,
87                char *buf, size_t len)
88 {
89         unsigned char curblock[AES_BLOCK_SIZE] = { 0, };
90         char *tmp;
91         char *tmpP;
92         int data_len, encrypt;
93         ast_aes_encrypt_key ecx;                        /*  AES 128 Encryption context */
94         ast_aes_decrypt_key dcx;
95
96         AST_DECLARE_APP_ARGS(args,
97                 AST_APP_ARG(key);
98                 AST_APP_ARG(data);
99         );
100
101         AST_STANDARD_APP_ARGS(args, data);
102
103         if (ast_strlen_zero(args.data) || ast_strlen_zero(args.key)) {
104                 ast_log(LOG_WARNING, "Syntax: %s(<key>,<data>) - missing argument!\n", cmd);
105                 return -1;
106         }
107
108         if (strlen(args.key) != AES_BLOCK_SIZE) {        /* key must be of 16 characters in length, 128 bits */
109                 ast_log(LOG_WARNING, "Syntax: %s(<key>,<data>) - <key> parameter must be exactly 16 characters!\n", cmd);
110                 return -1;
111         }
112
113         ast_aes_set_encrypt_key((unsigned char *) args.key, &ecx);   /* encryption:  plaintext -> encryptedtext -> base64 */
114         ast_aes_set_decrypt_key((unsigned char *) args.key, &dcx);   /* decryption:  base64 -> encryptedtext -> plaintext */
115         tmp = ast_calloc(1, len);                     /* requires a tmp buffer for the base64 decode */
116         tmpP = tmp;
117         encrypt = strcmp("AES_DECRYPT", cmd);           /* -1 if encrypting, 0 if decrypting */
118
119         if (encrypt) {                                  /* if decrypting first decode src to base64 */
120                 ast_copy_string(tmp, args.data, len);
121                 data_len = strlen(tmp);
122         } else {
123                 data_len = ast_base64decode((unsigned char *) tmp, args.data, len);
124         }
125
126         if (data_len >= len) {                        /* make sure to not go over buffer len */
127                 ast_log(LOG_WARNING, "Syntax: %s(<keys>,<data>) - <data> exceeds buffer length.  Result may be truncated!\n", cmd);
128                 data_len = len - 1;
129         }
130
131         while (data_len > 0) {
132                 memset(curblock, 0, AES_BLOCK_SIZE);
133                 memcpy(curblock, tmpP, (data_len < AES_BLOCK_SIZE) ? data_len : AES_BLOCK_SIZE);
134                 if (encrypt) {
135                         ast_aes_encrypt(curblock, (unsigned char *) tmpP, &ecx);
136                 } else {
137                         ast_aes_decrypt(curblock, (unsigned char *) tmpP, &dcx);
138                 }
139                 tmpP += AES_BLOCK_SIZE;
140                 data_len -= AES_BLOCK_SIZE;
141         }
142
143         if (encrypt) {                            /* if encrypting encode result to base64 */
144                 ast_base64encode(buf, (unsigned char *) tmp, strlen(tmp), len);
145         } else {
146                 memcpy(buf, tmp, len);
147         }
148         ast_free(tmp);
149
150         return 0;
151 }
152
153 static struct ast_custom_function aes_encrypt_function = {
154         .name = "AES_ENCRYPT",
155         .read = aes_helper,
156 };
157
158 static struct ast_custom_function aes_decrypt_function = {
159         .name = "AES_DECRYPT",
160         .read = aes_helper,
161 };
162
163 static int unload_module(void)
164 {
165         int res = ast_custom_function_unregister(&aes_decrypt_function);
166         return res | ast_custom_function_unregister(&aes_encrypt_function);
167 }
168
169 static int load_module(void)
170 {
171         int res = ast_custom_function_register(&aes_decrypt_function);
172         res |= ast_custom_function_register(&aes_encrypt_function);
173         return res ? AST_MODULE_LOAD_DECLINE : AST_MODULE_LOAD_SUCCESS;
174 }
175
176 AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_DEFAULT, "AES dialplan functions",
177                 .load = load_module,
178                 .unload = unload_module,
179                 .nonoptreq = "res_crypto",
180         );