Initial commit

package/network/services/ead/src/ead-crypt.c

@@ -0,0 +1,179 @@
+/*
+ * Copyright (C) 2008 Felix Fietkau <nbd@nbd.name>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <stddef.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+#include <unistd.h>
+#include <stdio.h>
+#include "ead.h"
+
+#include "sha1.c"
+#include "aes.c"
+
+#if EAD_DEBUGLEVEL >= 1
+#define DEBUG(n, format, ...) do { \
+	if (EAD_DEBUGLEVEL >= n) \
+		fprintf(stderr, format, ##__VA_ARGS__); \
+} while (0);
+
+#else
+#define DEBUG(n, format, ...) do {} while(0)
+#endif
+
+
+static uint32_t aes_enc_ctx[AES_PRIV_SIZE];
+static uint32_t aes_dec_ctx[AES_PRIV_SIZE];
+static uint32_t ead_rx_iv;
+static uint32_t ead_tx_iv;
+static uint32_t ivofs_vec;
+static unsigned int ivofs_idx = 0;
+static uint32_t W[80]; /* work space for sha1 */
+
+#define EAD_ENC_PAD	64
+
+void
+ead_set_key(unsigned char *skey)
+{
+	uint32_t *ivp = (uint32_t *)skey;
+
+	memset(aes_enc_ctx, 0, sizeof(aes_enc_ctx));
+	memset(aes_dec_ctx, 0, sizeof(aes_dec_ctx));
+
+	/* first 32 bytes of skey are used as aes key for
+	 * encryption and decryption */
+	rijndaelKeySetupEnc(aes_enc_ctx, skey);
+	rijndaelKeySetupDec(aes_dec_ctx, skey);
+
+	/* the following bytes are used as initialization vector for messages
+	 * (highest byte cleared to avoid overflow) */
+	ivp += 8;
+	ead_rx_iv = ntohl(*ivp) & 0x00ffffff;
+	ead_tx_iv = ead_rx_iv;
+
+	/* the last bytes are used to feed the random iv increment */
+	ivp++;
+	ivofs_vec = *ivp;
+}
+
+
+static bool
+ead_check_rx_iv(uint32_t iv)
+{
+	if (iv <= ead_rx_iv)
+		return false;
+
+	if (iv > ead_rx_iv + EAD_MAX_IV_INCR)
+		return false;
+
+	ead_rx_iv = iv;
+	return true;
+}
+
+
+static uint32_t
+ead_get_tx_iv(void)
+{
+	unsigned int ofs;
+
+	ofs = 1 + ((ivofs_vec >> 2 * ivofs_idx) & 0x3);
+	ivofs_idx = (ivofs_idx + 1) % 16;
+	ead_tx_iv += ofs;
+
+	return ead_tx_iv;
+}
+
+static void
+ead_hash_message(struct ead_msg_encrypted *enc, uint32_t *hash, int len)
+{
+	unsigned char *data = (unsigned char *) enc;
+
+	/* hash the packet with the stored hash part initialized to zero */
+	sha_init(hash);
+	memset(enc->hash, 0, sizeof(enc->hash));
+	while (len > 0) {
+		sha_transform(hash, data, W);
+		len -= 64;
+		data += 64;
+	}
+}
+
+void
+ead_encrypt_message(struct ead_msg *msg, unsigned int len)
+{
+	struct ead_msg_encrypted *enc = EAD_DATA(msg, enc);
+	unsigned char *data = (unsigned char *) enc;
+	uint32_t hash[5];
+	int enclen, i;
+
+	len += sizeof(struct ead_msg_encrypted);
+	enc->pad = (EAD_ENC_PAD - (len % EAD_ENC_PAD)) % EAD_ENC_PAD;
+	enclen = len + enc->pad;
+	msg->len = htonl(enclen);
+	enc->iv = htonl(ead_get_tx_iv());
+
+	ead_hash_message(enc, hash, enclen);
+	for (i = 0; i < 5; i++)
+		enc->hash[i] = htonl(hash[i]);
+	DEBUG(2, "SHA1 generate (0x%08x), len=%d\n", enc->hash[0], enclen);
+
+	while (enclen > 0) {
+		rijndaelEncrypt(aes_enc_ctx, data, data);
+		data += 16;
+		enclen -= 16;
+	}
+}
+
+int
+ead_decrypt_message(struct ead_msg *msg)
+{
+	struct ead_msg_encrypted *enc = EAD_DATA(msg, enc);
+	unsigned char *data = (unsigned char *) enc;
+	uint32_t hash_old[5], hash_new[5];
+	int len = ntohl(msg->len);
+	int i, enclen = len;
+
+	if (!len || (len % EAD_ENC_PAD > 0))
+		return 0;
+
+	while (len > 0) {
+		rijndaelDecrypt(aes_dec_ctx, data, data);
+		data += 16;
+		len -= 16;
+	}
+
+	data = (unsigned char *) enc;
+
+	if (enc->pad >= EAD_ENC_PAD) {
+		DEBUG(2, "Invalid padding length\n");
+		return 0;
+	}
+
+	if (!ead_check_rx_iv(ntohl(enc->iv))) {
+		DEBUG(2, "RX IV mismatch (0x%08x <> 0x%08x)\n", ead_rx_iv, ntohl(enc->iv));
+		return 0;
+	}
+
+	for (i = 0; i < 5; i++)
+		hash_old[i] = ntohl(enc->hash[i]);
+	ead_hash_message(enc, hash_new, enclen);
+	if (memcmp(hash_old, hash_new, sizeof(hash_old)) != 0) {
+		DEBUG(2, "SHA1 mismatch (0x%08x != 0x%08x), len=%d\n", hash_old[0], hash_new[0], enclen);
+		return 0;
+	}
+
+	enclen -= enc->pad + sizeof(struct ead_msg_encrypted);
+	return enclen;
+}