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/*
* Asterisk -- An open source telephony toolkit.
*
* Copyright (C) 2009, Digium, Inc.
*
* See http://www.asterisk.org for more information about
* the Asterisk project. Please do not directly contact
* any of the maintainers of this project for assistance;
* the project provides a web site, mailing lists and IRC
* channels for your use.
*
* This program is free software, distributed under the terms of
* the GNU General Public License Version 2. See the LICENSE file
* at the top of the source tree.
*/
/*! \file
*
* \brief AES encryption/decryption dialplan functions
*
* \author David Vossel <dvossel@digium.com>
* \ingroup functions
*/
#include "asterisk.h"
ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
#include "asterisk/module.h"
#include "asterisk/pbx.h"
#include "asterisk/app.h"
#include "asterisk/aes.h"
#include "asterisk/strings.h"
#define AES_BLOCK_SIZE 16
/*** DOCUMENTATION
<function name="AES_ENCRYPT" language="en_US">
<synopsis>
Encrypt a string with AES given a 16 character key.
</synopsis>
<syntax>
<parameter name="key" required="true">
<para>AES Key</para>
</parameter>
<parameter name="string" required="true">
<para>Input string</para>
</parameter>
</syntax>
<description>
<para>Returns an AES encrypted string encoded in base64.</para>
</description>
</function>
<function name="AES_DECRYPT" language="en_US">
<synopsis>
Decrypt a string encoded in base64 with AES given a 16 character key.
</synopsis>
<syntax>
<parameter name="key" required="true">
<para>AES Key</para>
</parameter>
<parameter name="string" required="true">
<para>Input string.</para>
</parameter>
</syntax>
<description>
<para>Returns the plain text string.</para>
</description>
</function>
***/
static int aes_helper(struct ast_channel *chan, const char *cmd, char *data,
char *buf, struct ast_str **str, ssize_t maxlen)
{
unsigned char curblock[AES_BLOCK_SIZE] = { 0, };
char *tmp = NULL;
char *tmpP;
int data_len, encrypt;
int keylen, len, tmplen, elen = 0;
ast_aes_encrypt_key ecx; /* AES 128 Encryption context */
ast_aes_decrypt_key dcx;
AST_DECLARE_APP_ARGS(args,
AST_APP_ARG(key);
AST_APP_ARG(data);
);
AST_STANDARD_APP_ARGS(args, data);
if (ast_strlen_zero(args.data) || ast_strlen_zero(args.key)) {
ast_log(LOG_WARNING, "Syntax: %s(<key>,<data>) - missing argument!\n", cmd);
return -1;
}
if ((keylen = strlen(args.key)) != AES_BLOCK_SIZE) { /* key must be of 16 characters in length, 128 bits */
ast_log(LOG_WARNING, "Syntax: %s(<key>,<data>) - <key> parameter must be exactly 16 characters%s!\n", cmd, keylen < 16 ? " - padding" : "");
return -1;
}
if (buf) {
len = maxlen;
} else if (maxlen == -1) {
len = ast_str_size(*str);
} else if (maxlen > 0) {
len = maxlen;
} else {
len = INT_MAX;
}
ast_debug(3, "len=%d\n", len);
encrypt = strcmp("AES_DECRYPT", cmd); /* -1 if encrypting, 0 if decrypting */
/* Round up the buffer to an even multiple of 16, plus 1 */
tmplen = (strlen(args.data) / 16 + 1) * 16 + 1;
tmp = ast_calloc(1, tmplen);
tmpP = tmp;
if (encrypt) { /* if decrypting first decode src to base64 */
/* encryption: plaintext -> encryptedtext -> base64 */
ast_aes_encrypt_key((unsigned char *) args.key, &ecx);
strcpy(tmp, args.data);
data_len = strlen(tmp);
} else {
/* decryption: base64 -> encryptedtext -> plaintext */
ast_aes_decrypt_key((unsigned char *) args.key, &dcx);
data_len = ast_base64decode((unsigned char *) tmp, args.data, tmplen);
}
if (data_len >= len) { /* make sure to not go over buffer len */
ast_log(LOG_WARNING, "Syntax: %s(<keys>,<data>) - <data> exceeds buffer length. Result may be truncated!\n", cmd);
data_len = len - 1;
}
while (data_len > 0) {
/* Tricky operation. We first copy the data into curblock, then
* the data is encrypted or decrypted and put back into the original
* buffer. */
memset(curblock, 0, AES_BLOCK_SIZE);
memcpy(curblock, tmpP, AES_BLOCK_SIZE);
if (encrypt) {
ast_aes_encrypt(curblock, (unsigned char *) tmpP, &ecx);
} else {
ast_aes_decrypt(curblock, (unsigned char *) tmpP, &dcx);
}
tmpP += AES_BLOCK_SIZE;
data_len -= AES_BLOCK_SIZE;
elen += AES_BLOCK_SIZE;
}
if (encrypt) { /* if encrypting encode result to base64 */
if (buf) {
ast_base64encode(buf, (unsigned char *) tmp, elen, len);
} else {
if (maxlen >= 0) {
ast_str_make_space(str, maxlen ? maxlen : elen * 4 / 3 + 2);
}
ast_base64encode(ast_str_buffer(*str), (unsigned char *) tmp, elen, ast_str_size(*str));
ast_str_update(*str);
}
} else {
if (buf) {
memcpy(buf, tmp, len);
} else {
ast_str_set(str, maxlen, "%s", tmp);
}
}
ast_free(tmp);
return 0;
}
static int aes_buf_helper(struct ast_channel *chan, const char *cmd, char *data,
char *buf, size_t maxlen)
{
return aes_helper(chan, cmd, data, buf, NULL, maxlen);
}
static int aes_str_helper(struct ast_channel *chan, const char *cmd, char *data,
struct ast_str **buf, ssize_t maxlen)
{
return aes_helper(chan, cmd, data, NULL, buf, maxlen);
}
static struct ast_custom_function aes_encrypt_function = {
.name = "AES_ENCRYPT",
.read = aes_buf_helper,
.read2 = aes_str_helper,
};
static struct ast_custom_function aes_decrypt_function = {
.name = "AES_DECRYPT",
.read = aes_buf_helper,
.read2 = aes_str_helper,
};
static int unload_module(void)
{
int res = ast_custom_function_unregister(&aes_decrypt_function);
return res | ast_custom_function_unregister(&aes_encrypt_function);
}
static int load_module(void)
{
int res = ast_custom_function_register(&aes_decrypt_function);
res |= ast_custom_function_register(&aes_encrypt_function);
return res ? AST_MODULE_LOAD_DECLINE : AST_MODULE_LOAD_SUCCESS;
}
AST_MODULE_INFO_STANDARD(ASTERISK_GPL_KEY, "AES dialplan functions");
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