63 lines
1.4 KiB
C
63 lines
1.4 KiB
C
/* $NetBSD: a_md5decrypt.c,v 1.3 1998/01/09 03:15:48 perry Exp $ */
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/*
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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_int32 authencryptions;
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extern u_int32 authdecryptions;
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extern u_int32 authkeyuncached;
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extern u_int32 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_int32S ((NOCRYPT_OCTETS)/sizeof(u_int32))
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#define BLOCK_int32S ((BLOCK_OCTETS)/sizeof(u_int32))
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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_int32 *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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char hash[16];
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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, (unsigned const char *)cache_key, cache_keylen);
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MD5Update(&ctx, (unsigned const char *)pkt, length);
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MD5Final(hash, &ctx);
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return (!memcmp((char *) hash,
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(char *)pkt + length + 4,
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BLOCK_OCTETS));
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}
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