126 lines
2.8 KiB
C
126 lines
2.8 KiB
C
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/* auth12crypt.c,v 3.1 1993/07/06 01:07:43 jbj Exp
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* auth12crypt.c - routines to support two stage NTP encryption
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*/
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#include "ntp_stdlib.h"
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/*
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* For our purposes an NTP packet looks like:
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*
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* a variable amount of encrypted data, multiple of 8 bytes, which
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* is encrypted in pass 1, followed by:
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* an 8 byte chunk of data which is encrypted in pass 2
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* NOCRYPT_OCTETS worth of unencrypted data, followed by:
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* BLOCK_OCTETS worth of ciphered checksum.
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*/
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#define NOCRYPT_OCTETS 4
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#define BLOCK_OCTETS 8
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#define NOCRYPT_LONGS ((NOCRYPT_OCTETS)/sizeof(U_LONG))
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#define BLOCK_LONGS ((BLOCK_OCTETS)/sizeof(U_LONG))
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/*
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* Imported from the key data base module
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*/
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extern U_LONG cache_keyid; /* cached key ID */
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extern u_char DEScache_ekeys[]; /* cached decryption keys */
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extern u_char DESzeroekeys[]; /* zero key decryption keys */
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/*
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* Stat counters, from the database module
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*/
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extern U_LONG authencryptions;
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extern U_LONG authkeyuncached;
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extern U_LONG authnokey;
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/*
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* auth1crypt - do the first stage of a two stage encryption
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*/
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void
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DESauth1crypt(keyno, pkt, length)
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U_LONG keyno;
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U_LONG *pkt;
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int length; /* length of all encrypted data */
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{
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register U_LONG *pd;
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register int i;
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register u_char *keys;
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U_LONG work[2];
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authencryptions++;
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if (keyno == 0) {
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keys = DESzeroekeys;
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} else {
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if (keyno != cache_keyid) {
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authkeyuncached++;
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if (!authhavekey(keyno)) {
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authnokey++;
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return;
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}
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}
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keys = DEScache_ekeys;
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}
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/*
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* Do the first five encryptions. Stick the intermediate result
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* in the mac field. The sixth encryption must wait until the
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* caller freezes a transmit time stamp, and will be done in stage 2.
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*/
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pd = pkt;
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work[0] = work[1] = 0;
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for (i = (length/BLOCK_OCTETS - 1); i > 0; i--) {
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work[0] ^= *pd++;
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work[1] ^= *pd++;
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DESauth_des(work, keys);
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}
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/*
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* Space to the end of the packet and stick the intermediate
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* result in the mac field.
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*/
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pd += BLOCK_LONGS + NOCRYPT_LONGS;
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*pd++ = work[0];
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*pd = work[1];
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}
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/*
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* auth2crypt - do the second stage of a two stage encryption
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*/
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int
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DESauth2crypt(keyno, pkt, length)
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U_LONG keyno;
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U_LONG *pkt;
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int length; /* total length of encrypted area */
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{
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register U_LONG *pd;
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register u_char *keys;
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/*
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* Skip the key check. The call to the first stage should
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* have got it.
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*/
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if (keyno == 0)
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keys = DESzeroekeys;
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else
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keys = DEScache_ekeys;
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/*
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* The mac currently should hold the results of the first `n'
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* encryptions. We xor in the last block in data section and
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* do the final encryption in place.
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*
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* Get a pointer to the MAC block. XOR in the last two words of
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* the data area. Call the encryption routine.
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*/
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pd = pkt + (length/sizeof(U_LONG)) + NOCRYPT_LONGS;
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*pd ^= *(pd - NOCRYPT_LONGS - 2);
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*(pd + 1) ^= *(pd - NOCRYPT_LONGS - 1);
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DESauth_des(pd, keys);
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return 4 + 8; /* return size of key number and MAC */
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}
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