489 lines
8.6 KiB
C
489 lines
8.6 KiB
C
/*
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* authkeys.c - routines to manage the storage of authentication keys
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*/
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#ifdef HAVE_CONFIG_H
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# include <config.h>
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#endif
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#include <stdio.h>
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#include "ntp_types.h"
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#include "ntp_fp.h"
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#include "ntp.h"
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#include "ntpd.h"
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#include "ntp_string.h"
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#include "ntp_malloc.h"
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#include "ntp_stdlib.h"
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/*
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* Structure to store keys in in the hash table.
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*/
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struct savekey {
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struct savekey *next;
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union {
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long bogon; /* Make sure nonempty */
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u_char MD5_key[32]; /* MD5 key */
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} k;
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keyid_t keyid; /* key identifier */
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u_short flags; /* flags that wave */
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u_long lifetime; /* remaining lifetime */
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int keylen; /* key length */
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};
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#define KEY_TRUSTED 0x001 /* this key is trusted */
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#define KEY_MD5 0x200 /* this is a MD5 type key */
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/*
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* The hash table. This is indexed by the low order bits of the
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* keyid. We make this fairly big for potentially busy servers.
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*/
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#define HASHSIZE 64
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#define HASHMASK ((HASHSIZE)-1)
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#define KEYHASH(keyid) ((keyid) & HASHMASK)
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struct savekey *key_hash[HASHSIZE];
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u_long authkeynotfound; /* keys not found */
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u_long authkeylookups; /* calls to lookup keys */
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u_long authnumkeys; /* number of active keys */
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u_long authkeyexpired; /* key lifetime expirations */
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u_long authkeyuncached; /* cache misses */
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u_long authnokey; /* calls to encrypt with no key */
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u_long authencryptions; /* calls to encrypt */
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u_long authdecryptions; /* calls to decrypt */
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/*
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* Storage for free key structures. We malloc() such things but
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* never free them.
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*/
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struct savekey *authfreekeys;
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int authnumfreekeys;
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#define MEMINC 12 /* number of new free ones to get */
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/*
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* The key cache. We cache the last key we looked at here.
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*/
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keyid_t cache_keyid; /* key identifier */
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u_char *cache_key; /* key pointer */
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u_int cache_keylen; /* key length */
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u_short cache_flags; /* flags that wave */
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/*
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* init_auth - initialize internal data
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*/
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void
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init_auth(void)
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{
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/*
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* Initialize hash table and free list
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*/
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memset((char *)key_hash, 0, sizeof key_hash);
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}
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/*
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* auth_findkey - find a key in the hash table
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*/
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struct savekey *
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auth_findkey(
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keyid_t keyno
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)
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{
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struct savekey *sk;
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sk = key_hash[KEYHASH(keyno)];
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while (sk != 0) {
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if (keyno == sk->keyid)
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return (sk);
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sk = sk->next;
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}
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return (0);
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}
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/*
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* auth_havekey - return one if the key is known
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*/
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int
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auth_havekey(
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keyid_t keyno
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)
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{
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struct savekey *sk;
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if (keyno == 0 || (keyno == cache_keyid))
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return (1);
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sk = key_hash[KEYHASH(keyno)];
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while (sk != 0) {
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if (keyno == sk->keyid)
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return (1);
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sk = sk->next;
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}
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return (0);
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}
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/*
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* authhavekey - return one and cache the key, if known and trusted.
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*/
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int
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authhavekey(
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keyid_t keyno
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)
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{
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struct savekey *sk;
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authkeylookups++;
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if (keyno == 0 || keyno == cache_keyid)
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return (1);
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authkeyuncached++;
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sk = key_hash[KEYHASH(keyno)];
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while (sk != 0) {
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if (keyno == sk->keyid)
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break;
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sk = sk->next;
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}
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if (sk == 0) {
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authkeynotfound++;
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return (0);
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} else if (!(sk->flags & KEY_TRUSTED)) {
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authnokey++;
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return (0);
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}
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cache_keyid = sk->keyid;
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cache_flags = sk->flags;
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if (sk->flags & KEY_MD5) {
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cache_key = sk->k.MD5_key;
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cache_keylen = sk->keylen;
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return (1);
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}
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return (0);
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}
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/*
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* auth_moremem - get some more free key structures
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*/
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int
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auth_moremem(void)
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{
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struct savekey *sk;
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int i;
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sk = (struct savekey *)calloc(MEMINC, sizeof(struct savekey));
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if (sk == 0)
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return (0);
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for (i = MEMINC; i > 0; i--) {
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sk->next = authfreekeys;
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authfreekeys = sk++;
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}
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authnumfreekeys += MEMINC;
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return (authnumfreekeys);
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}
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/*
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* authtrust - declare a key to be trusted/untrusted
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*/
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void
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authtrust(
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keyid_t keyno,
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u_long trust
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)
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{
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struct savekey *sk;
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#ifdef DEBUG
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if (debug > 2)
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printf("authtrust: keyid %08x life %lu\n", keyno, trust);
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#endif
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sk = key_hash[KEYHASH(keyno)];
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while (sk != 0) {
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if (keyno == sk->keyid)
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break;
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sk = sk->next;
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}
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if (sk == 0 && !trust)
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return;
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if (sk != 0) {
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if (cache_keyid == keyno) {
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cache_flags = 0;
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cache_keyid = 0;
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}
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if (trust > 0) {
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sk->flags |= KEY_TRUSTED;
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if (trust > 1)
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sk->lifetime = current_time + trust;
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else
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sk->lifetime = 0;
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return;
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}
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sk->flags &= ~KEY_TRUSTED; {
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struct savekey *skp;
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skp = key_hash[KEYHASH(keyno)];
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if (skp == sk) {
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key_hash[KEYHASH(keyno)] = sk->next;
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} else {
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while (skp->next != sk)
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skp = skp->next;
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skp->next = sk->next;
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}
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authnumkeys--;
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sk->next = authfreekeys;
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authfreekeys = sk;
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authnumfreekeys++;
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}
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return;
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}
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if (authnumfreekeys == 0)
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if (auth_moremem() == 0)
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return;
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sk = authfreekeys;
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authfreekeys = sk->next;
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authnumfreekeys--;
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sk->keyid = keyno;
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sk->flags = KEY_TRUSTED;
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sk->next = key_hash[KEYHASH(keyno)];
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key_hash[KEYHASH(keyno)] = sk;
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authnumkeys++;
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return;
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}
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/*
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* authistrusted - determine whether a key is trusted
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*/
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int
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authistrusted(
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keyid_t keyno
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)
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{
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struct savekey *sk;
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if (keyno == cache_keyid)
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return ((cache_flags & KEY_TRUSTED) != 0);
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authkeyuncached++;
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sk = key_hash[KEYHASH(keyno)];
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while (sk != 0) {
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if (keyno == sk->keyid)
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break;
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sk = sk->next;
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}
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if (sk == 0) {
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authkeynotfound++;
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return (0);
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} else if (!(sk->flags & KEY_TRUSTED)) {
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authkeynotfound++;
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return (0);
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}
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return (1);
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}
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void
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MD5auth_setkey(
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keyid_t keyno,
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const u_char *key,
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const int len
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)
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{
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struct savekey *sk;
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/*
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* See if we already have the key. If so just stick in the
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* new value.
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*/
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sk = key_hash[KEYHASH(keyno)];
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while (sk != 0) {
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if (keyno == sk->keyid) {
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strncpy((char *)sk->k.MD5_key, (const char *)key,
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sizeof(sk->k.MD5_key));
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if ((sk->keylen = len) > sizeof(sk->k.MD5_key))
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sk->keylen = sizeof(sk->k.MD5_key);
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sk->flags |= KEY_MD5;
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if (cache_keyid == keyno) {
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cache_flags = 0;
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cache_keyid = 0;
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}
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return;
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}
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sk = sk->next;
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}
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/*
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* Need to allocate new structure. Do it.
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*/
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if (authnumfreekeys == 0) {
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if (auth_moremem() == 0)
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return;
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}
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sk = authfreekeys;
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authfreekeys = sk->next;
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authnumfreekeys--;
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strncpy((char *)sk->k.MD5_key, (const char *)key,
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sizeof(sk->k.MD5_key));
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if ((sk->keylen = len) > sizeof(sk->k.MD5_key))
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sk->keylen = sizeof(sk->k.MD5_key);
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sk->keyid = keyno;
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sk->flags = KEY_MD5;
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sk->lifetime = 0;
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sk->next = key_hash[KEYHASH(keyno)];
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key_hash[KEYHASH(keyno)] = sk;
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authnumkeys++;
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return;
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}
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/*
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* auth_delkeys - delete all known keys, in preparation for rereading
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* the keys file (presumably)
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*/
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void
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auth_delkeys(void)
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{
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struct savekey *sk;
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struct savekey **skp;
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int i;
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for (i = 0; i < HASHSIZE; i++) {
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skp = &(key_hash[i]);
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sk = key_hash[i];
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/*
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* Leave autokey keys alone.
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*/
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while (sk != 0 && sk->keyid <= NTP_MAXKEY) {
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/*
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* Don't lose info as to which keys are trusted.
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*/
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if (sk->flags & KEY_TRUSTED) {
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skp = &(sk->next);
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memset(&sk->k, 0, sizeof(sk->k));
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sk->lifetime = 0;
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sk->keylen = 0;
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sk = sk->next;
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} else {
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*skp = sk->next;
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authnumkeys--;
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sk->next = authfreekeys;
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authfreekeys = sk;
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authnumfreekeys++;
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sk = *skp;
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}
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}
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}
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}
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/*
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* auth_agekeys - delete keys whose lifetimes have expired
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*/
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void
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auth_agekeys(void)
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{
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struct savekey *sk;
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struct savekey *skp;
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int i;
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for (i = 0; i < HASHSIZE; i++) {
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sk = skp = key_hash[i];
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while (sk != 0) {
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skp = sk->next;
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if (sk->lifetime > 0 && current_time >
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sk->lifetime) {
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authtrust(sk->keyid, 0);
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authkeyexpired++;
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}
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sk = skp;
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}
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}
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#ifdef DEBUG
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if (debug)
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printf("auth_agekeys: at %lu keys %lu expired %lu\n",
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current_time, authnumkeys, authkeyexpired);
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#endif
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}
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/*
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* authencrypt - generate message authenticator
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*
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* Returns length of authenticator field, zero if key not found.
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*/
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int
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authencrypt(
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keyid_t keyno,
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u_int32 *pkt,
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int length
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)
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{
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/*
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* A zero key identifier means the sender has not verified
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* the last message was correctly authenticated. The MAC
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* consists of a single word with value zero.
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*/
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authencryptions++;
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pkt[length / 4] = htonl(keyno);
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if (keyno == 0) {
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return (4);
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}
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if (!authhavekey(keyno))
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return (0);
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if (cache_flags & KEY_MD5)
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return (MD5authencrypt(cache_key, pkt, length));
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return (0);
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}
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/*
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* authdecrypt - verify message authenticator
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*
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* Returns one if authenticator valid, zero if invalid or key not found.
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*/
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int
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authdecrypt(
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keyid_t keyno,
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u_int32 *pkt,
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int length,
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int size
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)
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{
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/*
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* A zero key identifier means the sender has not verified
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* the last message was correctly authenticated. Nevertheless,
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* the authenticator itself is considered valid.
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*/
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authdecryptions++;
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if (keyno == 0)
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return (0);
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if (!authhavekey(keyno) || size < 4)
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return (0);
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if (cache_flags & KEY_MD5)
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return (MD5authdecrypt(cache_key, pkt, length, size));
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return (0);
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}
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