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/*
* md5crypt - MD5 based authentication routines
*/
#include "ntp_types.h"
#include "ntp_string.h"
#include "md5.h"
#include "ntp_stdlib.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 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
MD5authdecrypt(keyno, pkt, length)
u_long keyno;
const U_LONG *pkt;
int length; /* length of variable data in octets */
{
MD5_CTX ctx;
authdecryptions++;
if (keyno != cache_keyid) {
authkeyuncached++;
if (!authhavekey(keyno))
return 0;
}
MD5Init(&ctx);
MD5Update(&ctx, cache_key, cache_keylen);
MD5Update(&ctx, (char *)pkt, length);
MD5Final(&ctx);
return (!memcmp((char *)ctx.digest,
(char *)pkt + length + 4,
BLOCK_OCTETS));
}
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