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New upstream version 3.1.1

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billchenchina 2022-11-15 08:50:35 +08:00
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commit e7b41df57b
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src/transform_aes.c Normal file
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/**
* (C) 2007-22 - ntop.org and contributors
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3 of the License, or
* (at your option) any later version.
*
* 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.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not see see <http://www.gnu.org/licenses/>
*
*/
#include "n2n.h"
// size of random value prepended to plaintext defaults to AES BLOCK_SIZE;
// gradually abandoning security, lower values could be chosen;
// however, minimum transmission size with cipher text stealing scheme is one
// block; as network packets should be longer anyway, only low level programmer
// might encounter an issue with lower values here
#define AES_PREAMBLE_SIZE (AES_BLOCK_SIZE)
// cts/cbc mode is being used with random value prepended to plaintext
// instead of iv so, actual iv is aes_null_iv
const uint8_t aes_null_iv[AES_IV_SIZE] = { 0 };
typedef struct transop_aes {
aes_context_t *ctx;
} transop_aes_t;
static int transop_deinit_aes (n2n_trans_op_t *arg) {
transop_aes_t *priv = (transop_aes_t *)arg->priv;
if(priv->ctx)
aes_deinit(priv->ctx);
if(priv)
free(priv);
return 0;
}
// the aes packet format consists of
//
// - a random AES_PREAMBLE_SIZE-sized value prepended to plaintext
// encrypted together with the...
// - ... payload data
//
// [VV|DDDDDDDDDDDDDDDDDDDDD]
// | <---- encrypted ----> |
//
static int transop_encode_aes (n2n_trans_op_t *arg,
uint8_t *outbuf,
size_t out_len,
const uint8_t *inbuf,
size_t in_len,
const uint8_t *peer_mac) {
transop_aes_t *priv = (transop_aes_t *)arg->priv;
// the assembly buffer is a source for encrypting data
// the whole contents of assembly are encrypted
uint8_t assembly[N2N_PKT_BUF_SIZE];
size_t idx = 0;
int padded_len;
uint8_t padding;
uint8_t buf[AES_BLOCK_SIZE];
if(in_len <= N2N_PKT_BUF_SIZE) {
if((in_len + AES_PREAMBLE_SIZE + AES_BLOCK_SIZE) <= out_len) {
traceEvent(TRACE_DEBUG, "transop_encode_aes %lu bytes plaintext", in_len);
// full block sized random value (128 bit)
encode_uint64(assembly, &idx, n2n_rand());
encode_uint64(assembly, &idx, n2n_rand());
// adjust for maybe differently chosen AES_PREAMBLE_SIZE
idx = AES_PREAMBLE_SIZE;
// the plaintext data
encode_buf(assembly, &idx, inbuf, in_len);
// round up to next whole AES block size
padded_len = (((idx - 1) / AES_BLOCK_SIZE) + 1) * AES_BLOCK_SIZE;
padding = (padded_len-idx);
// pad the following bytes with zero, fixed length (AES_BLOCK_SIZE) seems to compile
// to slightly faster code than run-time dependant 'padding'
memset(assembly + idx, 0, AES_BLOCK_SIZE);
aes_cbc_encrypt(outbuf, assembly, padded_len, aes_null_iv, priv->ctx);
if(padding) {
// exchange last two cipher blocks
memcpy(buf, outbuf+padded_len - AES_BLOCK_SIZE, AES_BLOCK_SIZE);
memcpy(outbuf + padded_len - AES_BLOCK_SIZE, outbuf + padded_len - 2 * AES_BLOCK_SIZE, AES_BLOCK_SIZE);
memcpy(outbuf + padded_len - 2 * AES_BLOCK_SIZE, buf, AES_BLOCK_SIZE);
}
} else
traceEvent(TRACE_ERROR, "transop_encode_aes outbuf too small");
} else
traceEvent(TRACE_ERROR, "transop_encode_aes inbuf too big to encrypt");
return idx;
}
// see transop_encode_aes for packet format
static int transop_decode_aes (n2n_trans_op_t *arg,
uint8_t *outbuf,
size_t out_len,
const uint8_t *inbuf,
size_t in_len,
const uint8_t *peer_mac) {
transop_aes_t *priv = (transop_aes_t *)arg->priv;
uint8_t assembly[N2N_PKT_BUF_SIZE];
uint8_t rest;
size_t penultimate_block;
uint8_t buf[AES_BLOCK_SIZE];
int len = -1;
if(((in_len - AES_PREAMBLE_SIZE) <= N2N_PKT_BUF_SIZE) /* cipher text fits in assembly */
&& (in_len >= AES_PREAMBLE_SIZE) /* has at least random number */
&& (in_len >= AES_BLOCK_SIZE)) { /* minimum size requirement for cipher text stealing */
traceEvent(TRACE_DEBUG, "transop_decode_aes %lu bytes ciphertext", in_len);
rest = in_len % AES_BLOCK_SIZE;
if(rest) { /* cipher text stealing */
penultimate_block = ((in_len / AES_BLOCK_SIZE) - 1) * AES_BLOCK_SIZE;
// everything normal up to penultimate block
memcpy(assembly, inbuf, penultimate_block);
// prepare new penultimate block in buf
aes_ecb_decrypt(buf, inbuf + penultimate_block, priv->ctx);
memcpy(buf, inbuf + in_len - rest, rest);
// former penultimate block becomes new ultimate block
memcpy(assembly + penultimate_block + AES_BLOCK_SIZE, inbuf + penultimate_block, AES_BLOCK_SIZE);
// write new penultimate block from buf
memcpy(assembly + penultimate_block, buf, AES_BLOCK_SIZE);
// regular cbc decryption of the re-arranged ciphertext
aes_cbc_decrypt(assembly, assembly, in_len + AES_BLOCK_SIZE - rest, aes_null_iv, priv->ctx);
// check for expected zero padding and give a warning otherwise
if(memcmp(assembly + in_len, aes_null_iv, AES_BLOCK_SIZE - rest)) {
traceEvent(TRACE_WARNING, "transop_decode_aes payload decryption failed with unexpected cipher text stealing padding");
return -1;
}
} else {
// regular cbc decryption on multiple block-sized payload
aes_cbc_decrypt(assembly, inbuf, in_len, aes_null_iv, priv->ctx);
}
len = in_len - AES_PREAMBLE_SIZE;
memcpy(outbuf, assembly + AES_PREAMBLE_SIZE, len);
} else
traceEvent(TRACE_ERROR, "transop_decode_aes inbuf wrong size (%ul) to decrypt", in_len);
return len;
}
static int setup_aes_key (transop_aes_t *priv, const uint8_t *password, ssize_t password_len) {
unsigned char key_mat[32]; /* maximum aes key length, equals hash length */
unsigned char *key;
size_t key_size;
// let the user choose the degree of encryption:
// long input passwords will pick AES192 or AES256 with more robust but expensive encryption
// the input password always gets hashed to make a more unpredictable use of the key space
// just think of usually reset MSB of ASCII coded password bytes
pearson_hash_256(key_mat, password, password_len);
// the length-dependant scheme for key setup was discussed on github:
// https://github.com/ntop/n2n/issues/101 -- as no iv encryption required
// anymore, the key-size trigger values were roughly halved
if(password_len >= 33) {
key_size = AES256_KEY_BYTES; /* 256 bit */
} else if(password_len >= 23) {
key_size = AES192_KEY_BYTES; /* 192 bit */
} else {
key_size = AES128_KEY_BYTES; /* 128 bit */
}
// and use the last key-sized part of the hash as aes key
key = key_mat + sizeof(key_mat) - key_size;
// setup the key and have corresponding context created
if(aes_init (key, key_size, &(priv->ctx))) {
traceEvent(TRACE_ERROR, "setup_aes_key %u-bit key setup unsuccessful", key_size * 8);
return -1;
}
traceEvent(TRACE_DEBUG, "setup_aes_key %u-bit key setup completed", key_size * 8);
return 0;
}
static void transop_tick_aes (n2n_trans_op_t *arg, time_t now) {
// no tick action
}
// AES initialization function
int n2n_transop_aes_init (const n2n_edge_conf_t *conf, n2n_trans_op_t *ttt) {
transop_aes_t *priv;
const u_char *encrypt_key = (const u_char *)conf->encrypt_key;
size_t encrypt_key_len = strlen(conf->encrypt_key);
memset(ttt, 0, sizeof(*ttt));
ttt->transform_id = N2N_TRANSFORM_ID_AES;
ttt->tick = transop_tick_aes;
ttt->deinit = transop_deinit_aes;
ttt->fwd = transop_encode_aes;
ttt->rev = transop_decode_aes;
priv = (transop_aes_t*)calloc(1, sizeof(transop_aes_t));
if(!priv) {
traceEvent(TRACE_ERROR, "n2n_transop_aes_init cannot allocate transop_aes_t memory");
return -1;
}
ttt->priv = priv;
// setup the cipher and key
return setup_aes_key(priv, encrypt_key, encrypt_key_len);
}