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/*
* auth12crypt.c - routines to support two stage NTP encryption
*/
#include "ntp_stdlib.h"
/*
* For our purposes an NTP packet looks like:
*
* a variable amount of encrypted data, multiple of 8 bytes, which
* is encrypted in pass 1, followed by:
* an 8 byte chunk of data which is encrypted in pass 2
* NOCRYPT_OCTETS worth of unencrypted data, followed by:
* BLOCK_OCTETS worth of ciphered checksum.
*/
#define NOCRYPT_OCTETS 4
#define BLOCK_OCTETS 8
#define NOCRYPT_int32S ((NOCRYPT_OCTETS)/sizeof(u_int32))
#define BLOCK_int32S ((BLOCK_OCTETS)/sizeof(u_int32))
/*
* Imported from the key data base module
*/
extern u_int32 cache_keyid; /* cached key ID */
extern u_int32 DEScache_ekeys[]; /* cached decryption keys */
extern u_int32 DESzeroekeys[]; /* zero key decryption keys */
/*
* Stat counters, from the database module
*/
extern u_int32 authencryptions;
extern u_int32 authkeyuncached;
extern u_int32 authnokey;
/*
* auth1crypt - do the first stage of a two stage encryption
*/
void
DESauth1crypt(keyno, pkt, length)
u_int32 keyno;
u_int32 *pkt;
int length; /* length of all encrypted data */
{
register u_int32 *pd;
register int i;
register u_char *keys;
u_int32 work[2];
authencryptions++;
if (keyno == 0) {
keys = (u_char *)DESzeroekeys;
} else {
if (keyno != cache_keyid) {
authkeyuncached++;
if (!authhavekey(keyno)) {
authnokey++;
return;
}
}
keys = (u_char *)DEScache_ekeys;
}
/*
* Do the first five encryptions. Stick the intermediate result
* in the mac field. The sixth encryption must wait until the
* caller freezes a transmit time stamp, and will be done in stage 2.
*/
pd = pkt;
work[0] = work[1] = 0;
for (i = (length/BLOCK_OCTETS - 1); i > 0; i--) {
work[0] ^= *pd++;
work[1] ^= *pd++;
DESauth_des(work, keys);
}
/*
* Space to the end of the packet and stick the intermediate
* result in the mac field.
*/
pd += BLOCK_int32S + NOCRYPT_int32S;
*pd++ = work[0];
*pd = work[1];
}
/*
* auth2crypt - do the second stage of a two stage encryption
*/
int
DESauth2crypt(keyno, pkt, length)
u_int32 keyno;
u_int32 *pkt;
int length; /* total length of encrypted area */
{
register u_int32 *pd;
register u_char *keys;
/*
* Skip the key check. The call to the first stage should
* have got it.
*/
if (keyno == 0)
keys = (u_char *)DESzeroekeys;
else
keys = (u_char *)DEScache_ekeys;
/*
* The mac currently should hold the results of the first `n'
* encryptions. We xor in the last block in data section and
* do the final encryption in place.
*
* Get a pointer to the MAC block. XOR in the last two words of
* the data area. Call the encryption routine.
*/
pd = pkt + (length/sizeof(u_int32)) + NOCRYPT_int32S;
*pd ^= *(pd - NOCRYPT_int32S - 2);
*(pd + 1) ^= *(pd - NOCRYPT_int32S - 1);
DESauth_des(pd, keys);
return 4 + 8; /* return size of key number and MAC */
}
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