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Correctly check for unsigned subtraction underflow.

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This commit is contained in:
dmiller 2020-09-09 21:34:56 +00:00
parent 3521f15180
commit 9c1cfd8405
1 changed files with 3 additions and 1 deletions
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4
nmap_dns.cc
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@ -1473,6 +1473,7 @@ bool DNS::Factory::ptrToIp(const std::string &ptr, sockaddr_storage &ip)
break;
}
u8 n = *p;
// First subtract base regardless of underflow:
if (n < 0x3A) { // 0-9
n -= 0x30;
}
@ -1485,7 +1486,8 @@ bool DNS::Factory::ptrToIp(const std::string &ptr, sockaddr_storage &ip)
else { // invalid
return false;
}
if (n < 0) { // invalid
// Now catch any of the underflow conditions above:
if (n > 0xf) { // invalid
return false;
}
if (alt == 0) { // high nibble