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World_Of_Computer_Software-02-385-Vol-1of3.iso
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xntp3.zip
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authmd5encrypt
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1992-08-04
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/*
* md5crypt - MD5 based authentication routines
*/
#include <sys/types.h>
#include "md5.h"
extern u_long cache_keyid;
extern char *cache_key;
extern int cache_keylen;
/*
* Stat counters, imported from data base module
*/
extern u_long authencryptions;
extern u_long authdecryptions;
extern u_long authkeyuncached;
extern u_long authdecryptok;
extern u_long authnokey;
/*
* 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 16
#define NOCRYPT_LONGS ((NOCRYPT_OCTETS)/sizeof(u_long))
#define BLOCK_LONGS ((BLOCK_OCTETS)/sizeof(u_long))
int
MD5authencrypt(keyno, pkt, length)
u_long keyno;
u_long *pkt;
int length; /* length of encrypted portion of packet */
{
MD5_CTX ctx;
int len; /* in 4 byte quantities */
authencryptions++;
if (keyno != cache_keyid) {
authkeyuncached++;
if (!authhavekey(keyno)) {
authnokey++;
return 0;
}
}
len = length / sizeof(u_long);
/*
* Generate the authenticator.
*/
MD5Init(&ctx);
MD5Update(&ctx, cache_key, cache_keylen);
MD5Update(&ctx, (char *)pkt, length);
MD5Final(&ctx);
bcopy(ctx.digest, (char *) &pkt[NOCRYPT_LONGS + len], BLOCK_OCTETS);
return 4 + BLOCK_OCTETS; /* return size of key and MAC */
}