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For generating ICMP IDs to send, use modulus and addition on a single random

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number to guarantee it's nonzero (which some target hosts require) rather
than looping for new random numbers.  

* ICMP ID values are unimportant, as long as they are nonzero
* The original code to get random numbers was exactly duplicated (new variable,
  comment, loop, even whitespace) in the same function, so using a single
  variable set initially (albeit differently) simplifies duplication
This commit is contained in:
kris
2010-10-01 22:45:23 +00:00
parent 85d81f76ce
commit 380cfaba2c
1 changed files with 2 additions and 14 deletions
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16
scan_engine.cc
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@@ -3160,6 +3160,8 @@ static UltraProbe *sendIPScanProbe(UltraScanInfo *USI, HostScanStats *hss,
u32 vtag = 0;
char *chunk = NULL;
int chunklen = 0;
/* Some hosts do not respond to ICMP requests if the identifier is 0. */
u16 icmp_ident = (get_random_u16() % 0xffff) + 1;
if (USI->ethsd) {
memcpy(eth.srcmac, hss->target->SrcMACAddress(), 6);
@@ -3286,13 +3288,6 @@ static UltraProbe *sendIPScanProbe(UltraScanInfo *USI, HostScanStats *hss,
&packetlen);
break;
case IPPROTO_ICMP:
u16 icmp_ident;
/* Some hosts do not respond to ICMP requests if the identifier is 0. */
do {
icmp_ident = get_random_u16();
} while (icmp_ident == 0);
packet = build_icmp_raw(&o.decoys[decoy], hss->target->v4hostip(),
o.ttl, ipid, IP_TOS_DEFAULT, false,
o.ipoptions, o.ipoptionslen,
@@ -3353,13 +3348,6 @@ static UltraProbe *sendIPScanProbe(UltraScanInfo *USI, HostScanStats *hss,
free(packet);
}
} else if (pspec->type == PS_ICMP) {
u16 icmp_ident;
/* Some hosts do not respond to ICMP requests if the identifier is 0. */
do {
icmp_ident = get_random_u16();
} while (icmp_ident == 0);
for(decoy = 0; decoy < o.numdecoys; decoy++) {
packet = build_icmp_raw(&o.decoys[decoy], hss->target->v4hostip(),
o.ttl, ipid, IP_TOS_DEFAULT, false,