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/*
* PKCS #5 (Password-based Encryption)
* Copyright (c) 2009, Jouni Malinen <j@w1.fi>
*
* This software may be distributed under the terms of the BSD license.
* See README for more details.
*/
#include "includes.h"
#include "common.h"
#include "crypto/crypto.h"
#include "crypto/md5.h"
#include "asn1.h"
#include "pkcs5.h"
struct pkcs5_params {
enum pkcs5_alg {
PKCS5_ALG_UNKNOWN,
PKCS5_ALG_MD5_DES_CBC
} alg;
u8 salt[8];
size_t salt_len;
unsigned int iter_count;
};
static enum pkcs5_alg pkcs5_get_alg(struct asn1_oid *oid)
{
if (oid->len == 7 &&
oid->oid[0] == 1 /* iso */ &&
oid->oid[1] == 2 /* member-body */ &&
oid->oid[2] == 840 /* us */ &&
oid->oid[3] == 113549 /* rsadsi */ &&
oid->oid[4] == 1 /* pkcs */ &&
oid->oid[5] == 5 /* pkcs-5 */ &&
oid->oid[6] == 3 /* pbeWithMD5AndDES-CBC */)
return PKCS5_ALG_MD5_DES_CBC;
return PKCS5_ALG_UNKNOWN;
}
static int pkcs5_get_params(const u8 *enc_alg, size_t enc_alg_len,
struct pkcs5_params *params)
{
struct asn1_hdr hdr;
const u8 *enc_alg_end, *pos, *end;
struct asn1_oid oid;
char obuf[80];
/* AlgorithmIdentifier */
enc_alg_end = enc_alg + enc_alg_len;
os_memset(params, 0, sizeof(*params));
if (asn1_get_oid(enc_alg, enc_alg_end - enc_alg, &oid, &pos)) {
wpa_printf(MSG_DEBUG, "PKCS #5: Failed to parse OID "
"(algorithm)");
return -1;
}
asn1_oid_to_str(&oid, obuf, sizeof(obuf));
wpa_printf(MSG_DEBUG, "PKCS #5: encryption algorithm %s", obuf);
params->alg = pkcs5_get_alg(&oid);
if (params->alg == PKCS5_ALG_UNKNOWN) {
wpa_printf(MSG_INFO, "PKCS #5: unsupported encryption "
"algorithm %s", obuf);
return -1;
}
/*
* PKCS#5, Section 8
* PBEParameter ::= SEQUENCE {
* salt OCTET STRING SIZE(8),
* iterationCount INTEGER }
*/
if (asn1_get_next(pos, enc_alg_end - pos, &hdr) < 0 ||
hdr.class != ASN1_CLASS_UNIVERSAL ||
hdr.tag != ASN1_TAG_SEQUENCE) {
wpa_printf(MSG_DEBUG, "PKCS #5: Expected SEQUENCE "
"(PBEParameter) - found class %d tag 0x%x",
hdr.class, hdr.tag);
return -1;
}
pos = hdr.payload;
end = hdr.payload + hdr.length;
/* salt OCTET STRING SIZE(8) */
if (asn1_get_next(pos, end - pos, &hdr) < 0 ||
hdr.class != ASN1_CLASS_UNIVERSAL ||
hdr.tag != ASN1_TAG_OCTETSTRING ||
hdr.length != 8) {
wpa_printf(MSG_DEBUG, "PKCS #5: Expected OCTETSTRING SIZE(8) "
"(salt) - found class %d tag 0x%x size %d",
hdr.class, hdr.tag, hdr.length);
return -1;
}
pos = hdr.payload + hdr.length;
os_memcpy(params->salt, hdr.payload, hdr.length);
params->salt_len = hdr.length;
wpa_hexdump(MSG_DEBUG, "PKCS #5: salt",
params->salt, params->salt_len);
/* iterationCount INTEGER */
if (asn1_get_next(pos, end - pos, &hdr) < 0 ||
hdr.class != ASN1_CLASS_UNIVERSAL || hdr.tag != ASN1_TAG_INTEGER) {
wpa_printf(MSG_DEBUG, "PKCS #5: Expected INTEGER - found "
"class %d tag 0x%x", hdr.class, hdr.tag);
return -1;
}
if (hdr.length == 1)
params->iter_count = *hdr.payload;
else if (hdr.length == 2)
params->iter_count = WPA_GET_BE16(hdr.payload);
else if (hdr.length == 4)
params->iter_count = WPA_GET_BE32(hdr.payload);
else {
wpa_hexdump(MSG_DEBUG, "PKCS #5: Unsupported INTEGER value "
" (iterationCount)",
hdr.payload, hdr.length);
return -1;
}
wpa_printf(MSG_DEBUG, "PKCS #5: iterationCount=0x%x",
params->iter_count);
if (params->iter_count == 0 || params->iter_count > 0xffff) {
wpa_printf(MSG_INFO, "PKCS #5: Unsupported "
"iterationCount=0x%x", params->iter_count);
return -1;
}
return 0;
}
static struct crypto_cipher * pkcs5_crypto_init(struct pkcs5_params *params,
const char *passwd)
{
unsigned int i;
u8 hash[MD5_MAC_LEN];
const u8 *addr[2];
size_t len[2];
if (params->alg != PKCS5_ALG_MD5_DES_CBC)
return NULL;
addr[0] = (const u8 *) passwd;
len[0] = os_strlen(passwd);
addr[1] = params->salt;
len[1] = params->salt_len;
if (md5_vector(2, addr, len, hash) < 0)
return NULL;
addr[0] = hash;
len[0] = MD5_MAC_LEN;
for (i = 1; i < params->iter_count; i++) {
if (md5_vector(1, addr, len, hash) < 0)
return NULL;
}
/* TODO: DES key parity bits(?) */
wpa_hexdump_key(MSG_DEBUG, "PKCS #5: DES key", hash, 8);
wpa_hexdump_key(MSG_DEBUG, "PKCS #5: DES IV", hash + 8, 8);
return crypto_cipher_init(CRYPTO_CIPHER_ALG_DES, hash + 8, hash, 8);
}
u8 * pkcs5_decrypt(const u8 *enc_alg, size_t enc_alg_len,
const u8 *enc_data, size_t enc_data_len,
const char *passwd, size_t *data_len)
{
struct crypto_cipher *ctx;
u8 *eb, pad;
struct pkcs5_params params;
unsigned int i;
if (pkcs5_get_params(enc_alg, enc_alg_len, &params) < 0) {
wpa_printf(MSG_DEBUG, "PKCS #5: Unsupported parameters");
return NULL;
}
ctx = pkcs5_crypto_init(&params, passwd);
if (ctx == NULL) {
wpa_printf(MSG_DEBUG, "PKCS #5: Failed to initialize crypto");
return NULL;
}
/* PKCS #5, Section 7 - Decryption process */
if (enc_data_len < 16 || enc_data_len % 8) {
wpa_printf(MSG_INFO, "PKCS #5: invalid length of ciphertext "
"%d", (int) enc_data_len);
crypto_cipher_deinit(ctx);
return NULL;
}
eb = os_malloc(enc_data_len);
if (eb == NULL) {
crypto_cipher_deinit(ctx);
return NULL;
}
if (crypto_cipher_decrypt(ctx, enc_data, eb, enc_data_len) < 0) {
wpa_printf(MSG_DEBUG, "PKCS #5: Failed to decrypt EB");
crypto_cipher_deinit(ctx);
os_free(eb);
return NULL;
}
crypto_cipher_deinit(ctx);
pad = eb[enc_data_len - 1];
if (pad > 8) {
wpa_printf(MSG_INFO, "PKCS #5: Invalid PS octet 0x%x", pad);
os_free(eb);
return NULL;
}
for (i = enc_data_len - pad; i < enc_data_len; i++) {
if (eb[i] != pad) {
wpa_hexdump(MSG_INFO, "PKCS #5: Invalid PS",
eb + enc_data_len - pad, pad);
os_free(eb);
return NULL;
}
}
wpa_hexdump_key(MSG_MSGDUMP, "PKCS #5: message M (encrypted key)",
eb, enc_data_len - pad);
*data_len = enc_data_len - pad;
return eb;
}