| 1 | /* |
| 2 | * Copyright (C) 2008 Felix Fietkau <nbd@openwrt.org> |
| 3 | * |
| 4 | * This program is free software; you can redistribute it and/or modify |
| 5 | * it under the terms of the GNU General Public License version 2 |
| 6 | * as published by the Free Software Foundation |
| 7 | * |
| 8 | * This program is distributed in the hope that it will be useful, |
| 9 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 10 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 11 | * GNU General Public License for more details. |
| 12 | */ |
| 13 | |
| 14 | #include <stddef.h> |
| 15 | #include <stdint.h> |
| 16 | #include <stdlib.h> |
| 17 | #include <stdbool.h> |
| 18 | #include <string.h> |
| 19 | #include <unistd.h> |
| 20 | #include <stdio.h> |
| 21 | #include "ead.h" |
| 22 | |
| 23 | #include "sha1.c" |
| 24 | #include "aes.c" |
| 25 | |
| 26 | #if EAD_DEBUGLEVEL >= 1 |
| 27 | #define DEBUG(n, format, ...) do { \ |
| 28 | if (EAD_DEBUGLEVEL >= n) \ |
| 29 | fprintf(stderr, format, ##__VA_ARGS__); \ |
| 30 | } while (0); |
| 31 | |
| 32 | #else |
| 33 | #define DEBUG(n, format, ...) do {} while(0) |
| 34 | #endif |
| 35 | |
| 36 | |
| 37 | static uint32_t aes_enc_ctx[AES_PRIV_SIZE]; |
| 38 | static uint32_t aes_dec_ctx[AES_PRIV_SIZE]; |
| 39 | static uint32_t ead_rx_iv; |
| 40 | static uint32_t ead_tx_iv; |
| 41 | static uint32_t ivofs_vec; |
| 42 | static unsigned int ivofs_idx = 0; |
| 43 | static uint32_t W[80]; /* work space for sha1 */ |
| 44 | |
| 45 | #define EAD_ENC_PAD 64 |
| 46 | |
| 47 | void |
| 48 | ead_set_key(unsigned char *skey) |
| 49 | { |
| 50 | uint32_t *ivp = (uint32_t *)skey; |
| 51 | |
| 52 | memset(aes_enc_ctx, 0, sizeof(aes_enc_ctx)); |
| 53 | memset(aes_dec_ctx, 0, sizeof(aes_dec_ctx)); |
| 54 | |
| 55 | /* first 32 bytes of skey are used as aes key for |
| 56 | * encryption and decryption */ |
| 57 | rijndaelKeySetupEnc(aes_enc_ctx, skey); |
| 58 | rijndaelKeySetupDec(aes_dec_ctx, skey); |
| 59 | |
| 60 | /* the following bytes are used as initialization vector for messages |
| 61 | * (highest byte cleared to avoid overflow) */ |
| 62 | ivp += 8; |
| 63 | ead_rx_iv = ntohl(*ivp) & 0x00ffffff; |
| 64 | ead_tx_iv = ead_rx_iv; |
| 65 | |
| 66 | /* the last bytes are used to feed the random iv increment */ |
| 67 | ivp++; |
| 68 | ivofs_vec = *ivp; |
| 69 | } |
| 70 | |
| 71 | |
| 72 | static bool |
| 73 | ead_check_rx_iv(uint32_t iv) |
| 74 | { |
| 75 | if (iv <= ead_rx_iv) |
| 76 | return false; |
| 77 | |
| 78 | if (iv > ead_rx_iv + EAD_MAX_IV_INCR) |
| 79 | return false; |
| 80 | |
| 81 | ead_rx_iv = iv; |
| 82 | return true; |
| 83 | } |
| 84 | |
| 85 | |
| 86 | static uint32_t |
| 87 | ead_get_tx_iv(void) |
| 88 | { |
| 89 | unsigned int ofs; |
| 90 | |
| 91 | ofs = 1 + ((ivofs_vec >> 2 * ivofs_idx) & 0x3); |
| 92 | ivofs_idx = (ivofs_idx + 1) % 16; |
| 93 | ead_tx_iv += ofs; |
| 94 | |
| 95 | return ead_tx_iv; |
| 96 | } |
| 97 | |
| 98 | static void |
| 99 | ead_hash_message(struct ead_msg_encrypted *enc, uint32_t *hash, int len) |
| 100 | { |
| 101 | unsigned char *data = (unsigned char *) enc; |
| 102 | |
| 103 | /* hash the packet with the stored hash part initialized to zero */ |
| 104 | sha_init(hash); |
| 105 | memset(enc->hash, 0, sizeof(enc->hash)); |
| 106 | while (len > 0) { |
| 107 | sha_transform(hash, data, W); |
| 108 | len -= 64; |
| 109 | data += 64; |
| 110 | } |
| 111 | } |
| 112 | |
| 113 | void |
| 114 | ead_encrypt_message(struct ead_msg *msg, unsigned int len) |
| 115 | { |
| 116 | struct ead_msg_encrypted *enc = EAD_DATA(msg, enc); |
| 117 | unsigned char *data = (unsigned char *) enc; |
| 118 | uint32_t hash[5]; |
| 119 | int enclen, i; |
| 120 | |
| 121 | len += sizeof(struct ead_msg_encrypted); |
| 122 | enc->pad = (EAD_ENC_PAD - (len % EAD_ENC_PAD)) % EAD_ENC_PAD; |
| 123 | enclen = len + enc->pad; |
| 124 | msg->len = htonl(enclen); |
| 125 | enc->iv = htonl(ead_get_tx_iv()); |
| 126 | |
| 127 | ead_hash_message(enc, hash, enclen); |
| 128 | for (i = 0; i < 5; i++) |
| 129 | enc->hash[i] = htonl(hash[i]); |
| 130 | DEBUG(2, "SHA1 generate (0x%08x), len=%d\n", enc->hash[0], enclen); |
| 131 | |
| 132 | while (enclen > 0) { |
| 133 | rijndaelEncrypt(aes_enc_ctx, data, data); |
| 134 | data += 16; |
| 135 | enclen -= 16; |
| 136 | } |
| 137 | } |
| 138 | |
| 139 | int |
| 140 | ead_decrypt_message(struct ead_msg *msg) |
| 141 | { |
| 142 | struct ead_msg_encrypted *enc = EAD_DATA(msg, enc); |
| 143 | unsigned char *data = (unsigned char *) enc; |
| 144 | uint32_t hash_old[5], hash_new[5]; |
| 145 | int len = ntohl(msg->len); |
| 146 | int i, enclen = len; |
| 147 | |
| 148 | if (!len || (len % EAD_ENC_PAD > 0)) |
| 149 | return 0; |
| 150 | |
| 151 | while (len > 0) { |
| 152 | rijndaelDecrypt(aes_dec_ctx, data, data); |
| 153 | data += 16; |
| 154 | len -= 16; |
| 155 | } |
| 156 | |
| 157 | data = (unsigned char *) enc; |
| 158 | |
| 159 | if (enc->pad >= EAD_ENC_PAD) { |
| 160 | DEBUG(2, "Invalid padding length\n"); |
| 161 | return 0; |
| 162 | } |
| 163 | |
| 164 | if (!ead_check_rx_iv(ntohl(enc->iv))) { |
| 165 | DEBUG(2, "RX IV mismatch (0x%08x <> 0x%08x)\n", ead_rx_iv, ntohl(enc->iv)); |
| 166 | return 0; |
| 167 | } |
| 168 | |
| 169 | for (i = 0; i < 5; i++) |
| 170 | hash_old[i] = ntohl(enc->hash[i]); |
| 171 | ead_hash_message(enc, hash_new, enclen); |
| 172 | if (memcmp(hash_old, hash_new, sizeof(hash_old)) != 0) { |
| 173 | DEBUG(2, "SHA1 mismatch (0x%08x != 0x%08x), len=%d\n", hash_old[0], hash_new[0], enclen); |
| 174 | return 0; |
| 175 | } |
| 176 | |
| 177 | enclen -= enc->pad + sizeof(struct ead_msg_encrypted); |
| 178 | return enclen; |
| 179 | } |
| 180 | |
