enoch/n2n
1
0
Fork 0
mirror of https://github.com/ntop/n2n.git synced 2024-09-19 16:41:11 +02:00
Code Issues Actions Packages Projects Releases 1 Wiki Activity
n2n/transform_aes.c
emanuele-f e989f475a1 Fix invalid initializations
2019-03-28 00:20:16 +01:00

742 lines
22 KiB
C
Raw Blame History

/**
* (C) 2007-18 - 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"
#include "n2n_transforms.h"
#if defined(N2N_HAVE_AES)
#include "openssl/aes.h"
#ifndef _MSC_VER
/* Not included in Visual Studio 2008 */
#include <strings.h> /* index() */
#endif
#define N2N_AES_NUM_SA 32 /* space for SAa */
#define N2N_AES_TRANSFORM_VERSION 1 /* version of the transform encoding */
#define N2N_AES_IVEC_SIZE 32 /* Enough space for biggest AES ivec */
typedef unsigned char n2n_aes_ivec_t[N2N_AES_IVEC_SIZE];
struct sa_aes
{
n2n_cipherspec_t spec; /* cipher spec parameters */
n2n_sa_t sa_id; /* security association index */
AES_KEY enc_key; /* tx key */
n2n_aes_ivec_t enc_ivec; /* tx CBC state */
AES_KEY dec_key; /* tx key */
n2n_aes_ivec_t dec_ivec; /* tx CBC state */
};
typedef struct sa_aes sa_aes_t;
/** Aes transform state data.
*
* With a key-schedule in place this will be populated with a number of
* SAs. Each SA has a lifetime and some opque data. The opaque data for aes
* consists of the SA number and key material.
*
*/
struct transop_aes
{
ssize_t tx_sa;
size_t num_sa;
sa_aes_t sa[N2N_AES_NUM_SA];
/* PSK mode only */
int psk_mode;
u_int8_t mac_sa[N2N_AES_NUM_SA][N2N_MAC_SIZE]; /* this is used as a key in the sa array */
uint8_t *encrypt_pwd;
uint32_t encrypt_pwd_len;
size_t sa_to_replace;
};
typedef struct transop_aes transop_aes_t;
static ssize_t aes_find_sa( const transop_aes_t * priv, const n2n_sa_t req_id );
static int setup_aes_key(transop_aes_t *priv, const uint8_t *keybuf, ssize_t pstat, size_t sa_num);
static int transop_deinit_aes( n2n_trans_op_t * arg )
{
transop_aes_t * priv = (transop_aes_t *)arg->priv;
size_t i;
if ( priv )
{
/* Memory was previously allocated */
for (i=0; i<N2N_AES_NUM_SA; ++i )
{
sa_aes_t * sa = &(priv->sa[i]);
sa->sa_id=0;
}
priv->num_sa=0;
priv->tx_sa=-1;
free(priv);
}
arg->priv=NULL; /* return to fully uninitialised state */
return 0;
}
/* Find the peer_mac sa */
static size_t aes_psk_get_peer_sa(transop_aes_t * priv, const u_int8_t * peer_mac) {
size_t i;
int found = 0;
/* Find the MAC sa */
for(i=0; i<priv->num_sa; i++) {
if(!memcmp(priv->mac_sa[i], peer_mac, N2N_MAC_SIZE)) {
found = 1;
break;
}
}
if(found)
return(i);
size_t new_sa = priv->sa_to_replace;
macstr_t mac_buf;
macaddr_str(mac_buf, peer_mac);
traceEvent(TRACE_DEBUG, "Assigning SA %u to %s", new_sa, mac_buf);
setup_aes_key(priv, priv->encrypt_pwd, priv->encrypt_pwd_len, new_sa);
priv->num_sa = max(priv->num_sa, new_sa + 1);
memcpy(priv->mac_sa[new_sa], peer_mac, N2N_MAC_SIZE);
priv->sa[new_sa].sa_id = new_sa;
/* Use sa_to_replace round-robin */
priv->sa_to_replace = (priv->sa_to_replace + 1) % N2N_AES_NUM_SA;
return new_sa;
}
static size_t aes_choose_tx_sa( transop_aes_t * priv, const u_int8_t * peer_mac ) {
if(!priv->psk_mode)
return priv->tx_sa; /* set in tick */
else
return aes_psk_get_peer_sa(priv, peer_mac);
}
static ssize_t aes_choose_rx_sa( transop_aes_t * priv, const u_int8_t * peer_mac, ssize_t sa_rx) {
if(!priv->psk_mode)
return aes_find_sa(priv, sa_rx);
else
/* NOTE the sa_rx of the packet is ignored in this case */
return aes_psk_get_peer_sa(priv, peer_mac);
}
#define TRANSOP_AES_VER_SIZE 1 /* Support minor variants in encoding in one module. */
#define TRANSOP_AES_NONCE_SIZE 4
#define TRANSOP_AES_SA_SIZE 4
#define AES256_KEY_BYTES (256/8)
#define AES192_KEY_BYTES (192/8)
#define AES128_KEY_BYTES (128/8)
/* Return the best acceptable AES key size (in bytes) given an input keysize.
*
* The value returned will be one of AES128_KEY_BYTES, AES192_KEY_BYTES or
* AES256_KEY_BYTES.
*/
static size_t aes_best_keysize(size_t numBytes)
{
if (numBytes >= AES256_KEY_BYTES )
{
return AES256_KEY_BYTES;
}
else if (numBytes >= AES192_KEY_BYTES)
{
return AES192_KEY_BYTES;
}
else
{
return AES128_KEY_BYTES;
}
}
/** The aes packet format consists of:
*
* - a 8-bit aes encoding version in clear text
* - a 32-bit SA number in clear text
* - ciphertext encrypted from a 32-bit nonce followed by the payload.
*
* [V|SSSS|nnnnDDDDDDDDDDDDDDDDDDDDD]
* |<------ 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)
{
int len2=-1;
transop_aes_t * priv = (transop_aes_t *)arg->priv;
uint8_t assembly[N2N_PKT_BUF_SIZE];
uint32_t * pnonce;
if ( (in_len + TRANSOP_AES_NONCE_SIZE) <= N2N_PKT_BUF_SIZE )
{
if ( (in_len + TRANSOP_AES_NONCE_SIZE + TRANSOP_AES_SA_SIZE + TRANSOP_AES_VER_SIZE) <= out_len )
{
int len=-1;
size_t idx=0;
sa_aes_t * sa;
size_t tx_sa_num = 0;
/* The transmit sa is periodically updated */
tx_sa_num = aes_choose_tx_sa( priv, peer_mac );
sa = &(priv->sa[tx_sa_num]); /* Proper Tx SA index */
traceEvent( TRACE_DEBUG, "encode_aes %lu with SA %lu.", in_len, sa->sa_id );
/* Encode the aes format version. */
encode_uint8( outbuf, &idx, N2N_AES_TRANSFORM_VERSION );
/* Encode the security association (SA) number */
encode_uint32( outbuf, &idx, sa->sa_id );
/* Encrypt the assembly contents and write the ciphertext after the SA. */
len = in_len + TRANSOP_AES_NONCE_SIZE;
/* The assembly buffer is a source for encrypting data. The nonce is
* written in first followed by the packet payload. The whole
* contents of assembly are encrypted. */
pnonce = (uint32_t *)assembly;
*pnonce = rand();
memcpy( assembly + TRANSOP_AES_NONCE_SIZE, inbuf, in_len );
/* Need at least one encrypted byte at the end for the padding. */
len2 = ( (len / AES_BLOCK_SIZE) + 1) * AES_BLOCK_SIZE; /* Round up to next whole AES adding at least one byte. */
assembly[ len2-1 ]=(len2-len);
traceEvent( TRACE_DEBUG, "padding = %u", assembly[ len2-1 ] );
memset( &(sa->enc_ivec), 0, sizeof(sa->enc_ivec) );
AES_cbc_encrypt( assembly, /* source */
outbuf + TRANSOP_AES_VER_SIZE + TRANSOP_AES_SA_SIZE, /* dest */
len2, /* enc size */
&(sa->enc_key), sa->enc_ivec, 1 /* encrypt */ );
len2 += TRANSOP_AES_VER_SIZE + TRANSOP_AES_SA_SIZE; /* size of data carried in UDP. */
}
else
{
traceEvent( TRACE_ERROR, "encode_aes outbuf too small." );
}
}
else
{
traceEvent( TRACE_ERROR, "encode_aes inbuf too big to encrypt." );
}
return len2;
}
/* Search through the array of SAs to find the one with the required ID.
*
* @return array index where found or -1 if not found
*/
static ssize_t aes_find_sa( const transop_aes_t * priv, const n2n_sa_t req_id )
{
size_t i;
for (i=0; i < priv->num_sa; ++i)
{
const sa_aes_t * sa=NULL;
sa = &(priv->sa[i]);
if (req_id == sa->sa_id)
{
return i;
}
}
return -1;
}
/** The aes packet format consists of:
*
* - a 8-bit aes encoding version in clear text
* - a 32-bit SA number in clear text
* - ciphertext encrypted from a 32-bit nonce followed by the payload.
*
* [V|SSSS|nnnnDDDDDDDDDDDDDDDDDDDDD]
* |<------ encrypted ------>|
*/
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)
{
int len=0;
transop_aes_t * priv = (transop_aes_t *)arg->priv;
uint8_t assembly[N2N_PKT_BUF_SIZE];
if ( ( (in_len - (TRANSOP_AES_VER_SIZE + TRANSOP_AES_SA_SIZE)) <= N2N_PKT_BUF_SIZE ) /* Cipher text fits in assembly */
&& (in_len >= (TRANSOP_AES_VER_SIZE + TRANSOP_AES_SA_SIZE + TRANSOP_AES_NONCE_SIZE) ) /* Has at least version, SA and nonce */
)
{
n2n_sa_t sa_rx;
ssize_t sa_idx=-1;
size_t rem=in_len;
size_t idx=0;
uint8_t aes_enc_ver=0;
/* Get the encoding version to make sure it is supported */
decode_uint8( &aes_enc_ver, inbuf, &rem, &idx );
if ( N2N_AES_TRANSFORM_VERSION == aes_enc_ver )
{
/* Get the SA number and make sure we are decrypting with the right one. */
decode_uint32( &sa_rx, inbuf, &rem, &idx );
sa_idx = aes_choose_rx_sa(priv, peer_mac, sa_rx);
if ( sa_idx >= 0 )
{
sa_aes_t * sa = &(priv->sa[sa_idx]);
traceEvent( TRACE_DEBUG, "decode_aes %lu with SA %lu.", in_len, sa_rx, sa->sa_id );
len = (in_len - (TRANSOP_AES_VER_SIZE + TRANSOP_AES_SA_SIZE));
if ( 0 == (len % AES_BLOCK_SIZE ) )
{
uint8_t padding;
memset( &(sa->dec_ivec), 0, sizeof(sa->dec_ivec) );
AES_cbc_encrypt( (inbuf + TRANSOP_AES_VER_SIZE + TRANSOP_AES_SA_SIZE),
assembly, /* destination */
len,
&(sa->dec_key),
sa->dec_ivec, 0 /* decrypt */ );
/* last byte is how much was padding: max value should be
* AES_BLOCKSIZE-1 */
padding = assembly[ len-1 ] & 0xff;
if ( len >= (padding + TRANSOP_AES_NONCE_SIZE))
{
/* strictly speaking for this to be an ethernet packet
* it is going to need to be even bigger; but this is
* enough to prevent segfaults. */
traceEvent( TRACE_DEBUG, "padding = %u", padding );
len -= padding;
len -= TRANSOP_AES_NONCE_SIZE; /* size of ethernet packet */
/* Step over 4-byte random nonce value */
memcpy( outbuf,
assembly + TRANSOP_AES_NONCE_SIZE,
len );
}
else
{
traceEvent( TRACE_WARNING, "UDP payload decryption failed." );
}
}
else
{
traceEvent( TRACE_WARNING, "Encrypted length %d is not a multiple of AES_BLOCK_SIZE (%d)", len, AES_BLOCK_SIZE );
len = 0;
}
}
else
{
/* Wrong security association; drop the packet as it is undecodable. */
traceEvent( TRACE_ERROR, "decode_aes SA number %lu not found.", sa_rx );
/* REVISIT: should be able to load a new SA at this point to complete the decoding. */
}
}
else
{
/* Wrong security association; drop the packet as it is undecodable. */
traceEvent( TRACE_ERROR, "decode_aes unsupported aes version %u.", aes_enc_ver );
/* REVISIT: should be able to load a new SA at this point to complete the decoding. */
}
}
else
{
traceEvent( TRACE_ERROR, "decode_aes inbuf wrong size (%ul) to decrypt.", in_len );
}
return len;
}
/* NOTE: the caller should adjust priv->num_sa accordingly */
static int setup_aes_key(transop_aes_t *priv, const uint8_t *keybuf, ssize_t pstat, size_t sa_num) {
/* pstat is number of bytes read into keybuf. */
sa_aes_t * sa = &(priv->sa[sa_num]);
size_t aes_keysize_bytes;
size_t aes_keysize_bits;
uint8_t * padded_keybuf;
/* Clear out any old possibly longer key matter. */
memset( &(sa->enc_key), 0, sizeof(sa->enc_key) );
memset( &(sa->dec_key), 0, sizeof(sa->dec_key) );
memset( &(sa->enc_ivec), 0, sizeof(sa->enc_ivec) );
memset( &(sa->dec_ivec), 0, sizeof(sa->dec_ivec) );
aes_keysize_bytes = aes_best_keysize(pstat);
aes_keysize_bits = 8 * aes_keysize_bytes;
/* The aes_keysize_bytes may differ from pstat, possibly pad */
padded_keybuf = calloc(1, aes_keysize_bytes);
if(!padded_keybuf)
return(1);
memcpy(padded_keybuf, keybuf, pstat);
/* Use N2N_MAX_KEYSIZE because the AES key needs to be of fixed
* size. If fewer bits specified then the rest will be
* zeroes. AES acceptable key sizes are 128, 192 and 256
* bits. */
AES_set_encrypt_key(padded_keybuf, aes_keysize_bits, &(sa->enc_key));
AES_set_decrypt_key(padded_keybuf, aes_keysize_bits, &(sa->dec_key));
/* Leave ivecs set to all zeroes */
traceEvent( TRACE_DEBUG, "transop_addspec_aes sa_id=%u, %u bits data=%s.\n",
priv->sa[sa_num].sa_id, aes_keysize_bits, keybuf);
free(padded_keybuf);
return(0);
}
/*
* priv: pointer to transform state
* keybuf: buffer holding the key
* pstat: length of keybuf
*/
static void add_aes_key(transop_aes_t *priv, uint8_t *keybuf, ssize_t pstat) {
setup_aes_key(priv, keybuf, pstat, priv->num_sa);
++(priv->num_sa);
}
static int transop_addspec_aes( n2n_trans_op_t * arg, const n2n_cipherspec_t * cspec )
{
int retval = 1;
ssize_t pstat=-1;
transop_aes_t * priv = (transop_aes_t *)arg->priv;
uint8_t keybuf[N2N_MAX_KEYSIZE];
if ( priv->num_sa < N2N_AES_NUM_SA )
{
const char * op = (const char *)cspec->opaque;
const char * sep = index( op, '_' );
if ( sep )
{
char tmp[256];
size_t s;
s = sep - op;
memcpy( tmp, cspec->opaque, s );
tmp[s]=0;
s = strlen(sep+1); /* sep is the _ which might be immediately followed by NULL */
priv->sa[priv->num_sa].spec = *cspec;
priv->sa[priv->num_sa].sa_id = strtoul(tmp, NULL, 10);
memset( keybuf, 0, N2N_MAX_KEYSIZE );
pstat = n2n_parse_hex( keybuf, N2N_MAX_KEYSIZE, sep+1, s );
if ( pstat > 0 )
{
add_aes_key(priv, keybuf, pstat);
retval = 0;
}
}
else
{
traceEvent( TRACE_ERROR, "transop_addspec_aes : bad key data - missing '_'.\n");
}
}
else
{
traceEvent( TRACE_ERROR, "transop_addspec_aes : full.\n");
}
return retval;
}
static n2n_tostat_t transop_tick_aes( n2n_trans_op_t * arg, time_t now )
{
transop_aes_t * priv = (transop_aes_t *)arg->priv;
size_t i;
int found=0;
n2n_tostat_t r;
memset( &r, 0, sizeof(r) );
traceEvent( TRACE_DEBUG, "transop_aes tick num_sa=%u now=%lu", priv->num_sa, now );
for ( i=0; i < priv->num_sa; ++i )
{
if ( 0 == validCipherSpec( &(priv->sa[i].spec), now ) )
{
time_t remaining = priv->sa[i].spec.valid_until - now;
traceEvent( TRACE_INFO, "transop_aes choosing tx_sa=%u (valid for %lu sec)", priv->sa[i].sa_id, remaining );
priv->tx_sa=i;
found=1;
break;
}
else
{
traceEvent( TRACE_DEBUG, "transop_aes tick rejecting sa=%u %lu -> %lu",
priv->sa[i].sa_id, priv->sa[i].spec.valid_from, priv->sa[i].spec.valid_until );
}
}
if ( 0==found)
{
traceEvent( TRACE_INFO, "transop_aes no keys are currently valid. Keeping tx_sa=%u", priv->tx_sa );
}
else
{
r.can_tx = 1;
r.tx_spec.t = N2N_TRANSFORM_ID_AESCBC;
r.tx_spec = priv->sa[priv->tx_sa].spec;
}
return r;
}
static n2n_tostat_t transop_tick_aes_psk(n2n_trans_op_t * arg, time_t now) {
transop_aes_t * priv = (transop_aes_t *)arg->priv;
n2n_tostat_t r;
memset(&r, 0, sizeof(r));
// Always tx
r.can_tx = 1;
r.tx_spec.t = N2N_TRANSFORM_ID_AESCBC;
r.tx_spec = priv->sa[priv->tx_sa].spec;
return r;
}
int transop_aes_init( n2n_trans_op_t * ttt )
{
int retval = 1;
transop_aes_t * priv = NULL;
if ( ttt->priv )
{
transop_deinit_aes( ttt );
}
memset( ttt, 0, sizeof( n2n_trans_op_t ) );
priv = (transop_aes_t *) calloc(1, sizeof(transop_aes_t));
if ( NULL != priv )
{
size_t i;
sa_aes_t * sa=NULL;
/* install the private structure. */
ttt->priv = priv;
priv->num_sa=0;
priv->tx_sa=0; /* We will use this sa index for encoding. */
priv->psk_mode = 0;
ttt->transform_id = N2N_TRANSFORM_ID_AESCBC;
ttt->addspec = transop_addspec_aes;
ttt->tick = transop_tick_aes; /* chooses a new tx_sa */
ttt->deinit = transop_deinit_aes;
ttt->fwd = transop_encode_aes;
ttt->rev = transop_decode_aes;
for(i=0; i<N2N_AES_NUM_SA; ++i)
{
sa = &(priv->sa[i]);
sa->sa_id=0;
memset( &(sa->spec), 0, sizeof(n2n_cipherspec_t) );
memset( &(sa->enc_key), 0, sizeof(sa->enc_key) );
memset( &(sa->enc_ivec), 0, sizeof(sa->enc_ivec) );
memset( &(sa->dec_key), 0, sizeof(sa->dec_key) );
memset( &(sa->dec_ivec), 0, sizeof(sa->dec_ivec) );
}
retval = 0;
}
else
{
memset( ttt, 0, sizeof(n2n_trans_op_t) );
traceEvent( TRACE_ERROR, "Failed to allocate priv for aes" );
}
return retval;
}
/* Setup AES in pre-shared key mode */
int transop_aes_setup_psk(n2n_trans_op_t *ttt,
n2n_sa_t sa_num,
uint8_t *encrypt_pwd,
uint32_t encrypt_pwd_len) {
static const u_int8_t broadcast_mac[6] = {0xff,0xff,0xff,0xff,0xff,0xff};
int retval = 1;
transop_aes_t *priv = (transop_aes_t *)ttt->priv;
if(ttt->priv) {
/* Replace the tick function with the PSK version of it */
ttt->tick = transop_tick_aes_psk;
priv->psk_mode = 1;
memset(priv->mac_sa, 0, sizeof(priv->mac_sa));
priv->encrypt_pwd = encrypt_pwd;
priv->encrypt_pwd_len = encrypt_pwd_len;
priv->num_sa=0;
priv->tx_sa=0;
/* Add the key to be used for broadcast */
add_aes_key(priv, priv->encrypt_pwd, priv->encrypt_pwd_len);
memcpy(priv->mac_sa[0], broadcast_mac, N2N_MAC_SIZE);
priv->sa_to_replace = priv->num_sa;
retval = 0;
} else
traceEvent(TRACE_ERROR, "AES priv is not allocated");
return retval;
}
#else /* #if defined(N2N_HAVE_AES) */
struct transop_aes
{
ssize_t tx_sa;
};
typedef struct transop_aes transop_aes_t;
static int transop_deinit_aes( n2n_trans_op_t * arg )
{
transop_aes_t * priv = (transop_aes_t *)arg->priv;
if ( priv )
{
free(priv);
}
arg->priv=NULL; /* return to fully uninitialised state */
return 0;
}
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 )
{
return -1;
}
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 )
{
return -1;
}
static int transop_addspec_aes( n2n_trans_op_t * arg, const n2n_cipherspec_t * cspec )
{
traceEvent( TRACE_DEBUG, "transop_addspec_aes AES not built into edge.\n");
return -1;
}
static n2n_tostat_t transop_tick_aes( n2n_trans_op_t * arg, time_t now )
{
n2n_tostat_t r;
memset( &r, 0, sizeof(r) );
return r;
}
int transop_aes_init( n2n_trans_op_t * ttt )
{
int retval = 1;
transop_aes_t * priv = NULL;
if ( ttt->priv )
{
transop_deinit_aes( ttt );
}
memset( ttt, 0, sizeof( n2n_trans_op_t ) );
priv = (transop_aes_t *) malloc( sizeof(transop_aes_t) );
if ( NULL != priv )
{
/* install the private structure. */
ttt->priv = priv;
priv->tx_sa=0; /* We will use this sa index for encoding. */
ttt->transform_id = N2N_TRANSFORM_ID_AESCBC;
ttt->addspec = transop_addspec_aes;
ttt->tick = transop_tick_aes; /* chooses a new tx_sa */
ttt->deinit = transop_deinit_aes;
ttt->fwd = transop_encode_aes;
ttt->rev = transop_decode_aes;
retval = 0;
}
else
{
memset( ttt, 0, sizeof(n2n_trans_op_t) );
traceEvent( TRACE_ERROR, "Failed to allocate priv for aes" );
}
return retval;
}
int transop_aes_setup_psk(n2n_trans_op_t *ttt,
n2n_sa_t sa_num,
uint8_t *encrypt_pwd,
uint32_t encrypt_pwd_len) {
return 0;
}
#endif /* #if defined(N2N_HAVE_AES) */
Reference in New Issue View Git Blame Copy Permalink