Correcting the uptime parsing and reporting in SNMPsysdesr.nse when the uptime is less than about 46 hours. The amount of bytes holding the uptime is variable up to 4, but the script was assuming it always held 4 bytes of uptime. When the real uptime was less than 46 hours, this script was reporting an uptime anywhere from 5 days to 130 days (I think it actually reported 0 days once, but the hours were all messed up).

scripts/SNMPsysdesr.nse

@@ -90,18 +90,30 @@ action = function(host, port)
 	
 	try(socket:close())
 
-	if string.find(response, "\006\001\002\001\001\003") == nil then
+	local start, stop = response:find("\006\001\002\001\001\003\000")
+
+	if start == nil then
 		return result
 	end
 	
-	local length,uptime,s1,s2,s3,s4
-	
-	length = string.len(response)
-	
-	s1,s2,s3,s4 = string.byte(response, length - 3, length)
-	
-	uptime = s1*(2^24) + s2*(2^16) + s3*(2^8) + s4
-	
+	local uplen,uptime,s1,s2,s3,s4
+
+	uplen = response:byte(stop + 2)
+
+	s1,s2,s3,s4 = response:byte(stop + 3, stop + 3 + uplen)
+
+	if uplen == 4 then
+		uptime = s1*(2^24) + s2*(2^16) + s3*(2^8) + s4
+	elseif uplen == 3 then
+		uptime = s1*(2^16) + s2*(2^8) + s3
+	elseif uplen == 2 then
+		uptime = s1*(2^8) + s2
+	elseif uplen == 1 then
+		uptime = s1
+	else
+		return result
+	end
+
 	local days, hours, minutes, seconds, htime, mtime, stime
 	days = math.floor(uptime / 8640000)
 	htime = math.fmod(uptime, 8640000)