New script, snmp-info for querying snmpv3 services

CHANGELOG

@@ -1,5 +1,8 @@
 # Nmap Changelog ($Id$); -*-text-*-
 
+o [NSE] Added snmp-info to get the enterprise number and other information from
+  the snmpEngineID in an SNMPv3 response packet. [Daniel Miller]
+
 o [NSE] Add support to citrix-enum-apps-xml for reporting if Citrix 
    published applications in the list are enforcing/requiring the level 
    of ICA/session data encryption shown in the script result.  

scripts/script.db

@@ -421,6 +421,7 @@ Entry { filename = "smtp-vuln-cve2011-1764.nse", categories = { "intrusive", "vu
 Entry { filename = "sniffer-detect.nse", categories = { "discovery", "intrusive", } }
 Entry { filename = "snmp-brute.nse", categories = { "brute", "intrusive", } }
 Entry { filename = "snmp-hh3c-logins.nse", categories = { "default", "discovery", "safe", } }
+Entry { filename = "snmp-info.nse", categories = { "default", "safe", "version", } }
 Entry { filename = "snmp-interfaces.nse", categories = { "default", "discovery", "safe", } }
 Entry { filename = "snmp-ios-config.nse", categories = { "intrusive", } }
 Entry { filename = "snmp-netstat.nse", categories = { "default", "discovery", "safe", } }

scripts/snmp-info.nse

@@ -0,0 +1,172 @@
+local bin = require "bin"
+local datafiles = require "datafiles"
+local ipOps = require "ipOps"
+local nmap = require "nmap"
+local shortport = require "shortport"
+local snmp = require "snmp"
+local stdnse = require "stdnse"
+local string = require "string"
+local lpeg = require "lpeg"
+local U = require "lpeg-utility"
+local comm = require "comm"
+
+description = [[
+Extracts basic information from an SNMPv3 GET request. The same probe is used
+here as in the service version detection scan.
+]]
+
+---
+--@output
+--161/udp open  snmp    udp-response ttl 244   ciscoSystems SNMPv3 server (public)
+--| snmp-info:
+--|   enterprise: ciscoSystems
+--|   engineIDFormat: mac
+--|   engineIDData: 00:d4:8c:00:11:22
+--|   snmpEngineBoots: 6
+--|_  snmpEngineTime: 358d01h13m46s
+--
+--@xmloutput
+-- <elem key="enterprise">ciscoSystems</elem>
+-- <elem key="engineIDFormat">mac</elem>
+-- <elem key="engineIDData">00:d4:8c:b5:32:bc</elem>
+-- <elem key="snmpEngineBoots">6</elem>
+-- <elem key="snmpEngineTime">358d01h26m34s</elem>
+
+author = "Daniel Miller"
+
+license = "Same as Nmap--See http://nmap.org/book/man-legal.html"
+
+categories = {"default", "version", "safe"}
+
+portrule = shortport.version_port_or_service(161, "snmp", "udp")
+
+-- XXX This section copied from http-server-header. Should be moved to a library.
+-- Cache the returned pattern
+local getquote = U.escaped_quote()
+
+-- Substitution pattern to unescape a string
+local unescape = lpeg.P {
+  -- Substitute captures
+  lpeg.Cs((lpeg.V "simple_char" + lpeg.V "unesc")^0),
+  -- Escape char is '\'
+  esc = lpeg.P "\\",
+  -- Simple char is anything but escape char
+  simple_char = lpeg.P(1) - lpeg.V "esc",
+  -- If we hit an escape, process specials or hex code, otherwise remove the escape
+  unesc = (lpeg.V "esc" * lpeg.Cs( lpeg.V "specials" + lpeg.V "code" + lpeg.P(1) ))/"%1",
+  -- single-char escapes. These are the only ones service_scan uses
+  specials = lpeg.S "trn0" / {t="\t", r="\r", n="\n", ["0"]="\0"},
+  -- hex escape: convert to char
+  code = (lpeg.P "x" * lpeg.C(lpeg.S "0123456789abcdefABCDEF"^-2))/function(c)
+  return string.char(tonumber(c,16)) end,
+}
+
+-- Turn the service fingerprint reply to a probe into a binary blob
+local function get_response (fp, probe)
+  local i, e = string.find(fp, string.format("%s,%%d+,", probe))
+  if i == nil then return nil end
+  return unescape:match(getquote:match(fp, e+1))
+end
+
+-- XXX End copy-paste.
+
+local ENTERPRISE_NUMS
+do
+  local status
+  status, ENTERPRISE_NUMS = datafiles.parse_file("nselib/data/enterprise_numbers.txt",
+    {[function(l) return tonumber(l:match("^%d+")) end] = "\t(.*)$"})
+  if not status then
+    stdnse.debug1("Couldn't parse enterprise numbers datafile: %s", ENTERPRISE_NUMS)
+    ENTERPRISE_NUMS = {}
+    setmetatable(ENTERPRISE_NUMS, {__index = function(i) return "unknown" end})
+  end
+end
+
+-- Lifted from nmap-service-probes:
+local SNMPv3GetRequest = "\x30\x3a\x02\x01\x03\x30\x0f\x02\x02\x4a\x69\x02\x03\0\xff\xe3\x04\x01\x04\x02\x01\x03\x04\x10\x30\x0e\x04\0\x02\x01\0\x02\x01\0\x04\0\x04\0\x04\0\x30\x12\x04\0\x04\0\xa0\x0c\x02\x02\x37\xf0\x02\x01\0\x02\x01\0\x30\0"
+
+-- TODO: This should probably check for version 1 and version 2, since those
+-- can operate on the same port. Right now it's really just "snmp3-info"
+action = function (host, port)
+  local response
+  -- Did the service engine already do the hard work?
+  if port.version and port.version.service_fp then
+    -- Probes sent, replies received, but no match. Unwrap the fingerprint:
+    local fp = string.gsub(port.version.service_fp, "\nSF:", "")
+    response = get_response(fp, "SNMPv3GetRequest")
+  end
+
+  if not response then
+    -- Have to send the probe ourselves
+    local status
+    status, response = comm.exchange(host, port, SNMPv3GetRequest)
+    if not status then
+      stdnse.debug1("Couldn't get a response: %s", response)
+      return nil
+    end
+  end
+
+  -- Check for SNMP version 3 and msgid 0x4a69 (from the probe)
+  if not response:match("^..\x02\x01\x03\x30.\x02\x02Ji") then
+    stdnse.debug1("Service is not SNMPv3, or packet structure not recognized")
+    return nil
+  end
+  local decoded = {snmp.decode(response)}
+
+  -- This really only works for User-based Security Model (USM)
+  if decoded[2][2][4] ~= 3 then
+    -- TODO: at least report the security model in use
+    stdnse.debug1("SNMP service not using User-based Security Model")
+    return nil
+  end
+
+  -- Decode the msgSecurityParameters octet-string
+  decoded = {snmp.decode(decoded[2][3])}
+
+  local output = stdnse.output_table()
+  -- Decode the msgAuthoritativeEngineID octet-string
+  local engineID = decoded[2][1]
+  local pos, enterprise = bin.unpack(">I", engineID)
+  if enterprise > 0x80000000 then
+    enterprise = enterprise - 0x80000000
+    output.enterprise = ENTERPRISE_NUMS[enterprise]
+    local format, data
+    pos, format = bin.unpack("C", engineID, pos)
+    if format == 1 then
+      output.engineIDFormat = "ipv4"
+      output.engineIDData = ipOps.str_to_ip(engineID:sub(pos,pos+3))
+    elseif format == 2 then
+      output.engineIDFormat = "ipv6"
+      output.engineIDData = ipOps.str_to_ip(engineID:sub(pos,pos+15))
+    elseif format == 3 then
+      output.engineIDFormat = "mac"
+      output.engineIDData = stdnse.tohex(engineID:sub(pos,pos+5), {separator=':'})
+    elseif format == 4 then
+      output.engineIDFormat = "text"
+      output.engineIDData = engineID:sub(pos)
+    elseif format == 5 then
+      output.engineIDFormat = "octets"
+      output.engineIDData = stdnse.tohex(engineID:sub(pos))
+    else
+      output.engineIDFormat = "unknown"
+      output.engineIDData = stdnse.tohex(engineID:sub(pos))
+    end
+  else
+    output.enterprise = ENTERPRISE_NUMS[enterprise] or enterprise
+    output.engineIDFormat = "unknown"
+    output.engineIDData = stdnse.tohex(engineID:sub(5))
+  end
+  output.snmpEngineBoots = decoded[2][2]
+  output.snmpEngineTime = stdnse.format_time(decoded[2][3])
+
+  port.version = port.version or {}
+  port.version.service = "snmp"
+  if port.version.product and port.version.product ~= "SNMPv3 server" then
+    port.version.product = ("%s; %s SNMPv3 server"):format(port.version.product, output.enterprise)
+  else
+    port.version.product = ("%s SNMPv3 server"):format(output.enterprise)
+  end
+  nmap.set_port_version(host, port, "hardmatched")
+
+  return output
+end