pinger: Echo all received bytes on Windows icmp_sock (#2210)

Avoids OOB read by strlen().

Author: MegaManSec

src/icmp/IcmpPinger.cc

@@ -51,12 +51,14 @@ IcmpPinger::Open(void)
 
     WSADATA wsaData;
     WSAPROTOCOL_INFO wpi;
-    char buf[sizeof(wpi)];
+    char buf[sizeof(wpi)+1];
     int x;
 
     struct sockaddr_in PS;
     int xerrno;
 
+    static_assert(sizeof(WSAPROTOCOL_INFO) >= sizeof(PS), "PS must fit into wpi-sized buf");
+
     WSAStartup(2, &wsaData);
     atexit(Win32SockCleanup);
 
@@ -114,7 +116,7 @@ IcmpPinger::Open(void)
 
     xwrite(1, "OK\n", 3);
     memset(buf, 0, sizeof(buf));
-    x = xrecv(icmp_sock, buf, sizeof(buf), 0);
+    x = xrecv(icmp_sock, buf, sizeof(buf)-1, 0);
 
     if (x < 3) {
         xerrno = errno;