91 lines
2.0 KiB
C
91 lines
2.0 KiB
C
/* $NetBSD: authencrypt.c,v 1.2 1998/01/09 03:15:55 perry Exp $ */
|
|
|
|
/*
|
|
* authencrypt - compute and encrypt the mac field in an NTP packet
|
|
*/
|
|
#include "ntp_stdlib.h"
|
|
|
|
/*
|
|
* For our purposes an NTP packet looks like:
|
|
*
|
|
* a variable amount of encrypted data, multiple of 8 bytes, followed by:
|
|
* 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_long cache_keyid; /* cached key ID */
|
|
extern u_long DEScache_ekeys[]; /* cached decryption keys */
|
|
extern u_long DESzeroekeys[]; /* zero key decryption keys */
|
|
|
|
/*
|
|
* Stat counters from the database module
|
|
*/
|
|
extern u_int32 authencryptions;
|
|
extern u_int32 authkeyuncached;
|
|
extern u_int32 authnokey;
|
|
|
|
int
|
|
DESauthencrypt(keyno, pkt, length)
|
|
u_long keyno;
|
|
u_int32 *pkt;
|
|
int length; /* length of encrypted portion of packet */
|
|
{
|
|
register u_int32 *pd;
|
|
register int i;
|
|
register u_char *keys;
|
|
register int len;
|
|
u_int32 work[2];
|
|
|
|
authencryptions++;
|
|
|
|
if (keyno == 0) {
|
|
keys = (u_char *)DESzeroekeys;
|
|
} else {
|
|
if (keyno != cache_keyid) {
|
|
authkeyuncached++;
|
|
if (!authhavekey(keyno)) {
|
|
authnokey++;
|
|
return 0;
|
|
}
|
|
}
|
|
keys = (u_char *)DEScache_ekeys;
|
|
}
|
|
|
|
/*
|
|
* Do the encryption. Work our way forward in the packet, eight
|
|
* bytes at a time, encrypting as we go. Note that the byte order
|
|
* issues are handled by the DES routine itself
|
|
*/
|
|
pd = pkt;
|
|
work[0] = work[1] = 0;
|
|
len = length / sizeof(u_int32);
|
|
|
|
for (i = (len/2); i > 0; i--) {
|
|
work[0] ^= *pd++;
|
|
work[1] ^= *pd++;
|
|
DESauth_des(work, keys);
|
|
}
|
|
|
|
if (len & 0x1) {
|
|
work[0] ^= *pd++;
|
|
DESauth_des(work, keys);
|
|
}
|
|
|
|
/*
|
|
* Space past the keyid and stick the result back in the mac field
|
|
*/
|
|
pd += NOCRYPT_int32S;
|
|
*pd++ = work[0];
|
|
*pd = work[1];
|
|
|
|
return 4 + BLOCK_OCTETS; /* return size of key and MAC */
|
|
}
|