61 lines
1.3 KiB
C
61 lines
1.3 KiB
C
/* authmd5decrypt.c,v 3.1 1993/07/06 01:07:53 jbj Exp
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* md5crypt - MD5 based authentication routines
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*/
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#include "ntp_types.h"
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#include "ntp_string.h"
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#include "md5.h"
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#include "ntp_stdlib.h"
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extern U_LONG cache_keyid;
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extern char *cache_key;
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extern int cache_keylen;
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/*
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* Stat counters, imported from data base module
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*/
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extern U_LONG authencryptions;
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extern U_LONG authdecryptions;
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extern U_LONG authkeyuncached;
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extern U_LONG authdecryptok;
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extern U_LONG authnokey;
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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, followed by:
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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 16
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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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int
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MD5authdecrypt(keyno, pkt, length)
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U_LONG keyno;
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const U_LONG *pkt;
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int length; /* length of variable data in octets */
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{
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MD5_CTX ctx;
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authdecryptions++;
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if (keyno != cache_keyid) {
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authkeyuncached++;
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if (!authhavekey(keyno))
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return 0;
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}
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MD5Init(&ctx);
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MD5Update(&ctx, cache_key, cache_keylen);
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MD5Update(&ctx, (char *)pkt, length);
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MD5Final(&ctx);
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return (!memcmp((char *)ctx.digest,
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(char *)pkt + length + 4,
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BLOCK_OCTETS));
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}
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