Revert r32789 in favor of lib-level fixes

nmap.new_try() shouldn't be used in libraries. It results in Lua errors
being thrown that the script can't recover from without resorting to
pcall(). It has been replaced in proxy.lua with proper error handling
which did not require any changes to the scripts (http-open-proxy and
socks-open-proxy) that used it.

nselib/proxy.lua

@@ -69,11 +69,18 @@ end
 --@return result The result of the request
 --@return code_status True or false. If pattern was used, returns the result of code checking for the same result. If pattern was not used, is nil.
 local function test(socket, req, pattern)
-  local _, result, s_code, s_pattern
+  local status, result = socket:send(req)
-  socket:send(req)
+  if not status then
-  _, result = socket:receive()
+    socket:close()
+    return false, result
+  end
+  status, result = socket:receive()
+  if not status then
+    socket:close()
+    return false, result
+  end
   socket:close()
-  s_code, s_pattern = check(result, pattern)
+  local s_code, s_pattern = check(result, pattern)
   if result and pattern then return s_pattern, result, s_code end
   if result then return s_code, result, nil end
   return false, nil, nil
@@ -88,8 +95,10 @@ end
 -- @param pattern The pattern to check for valid result
 -- @return the result of the function test (status and the request result)
 function test_get(host, port, proxyType, test_url, hostname, pattern)
-  local socket = connectProxy(host, port, proxyType, hostname)
+  local status, socket = connectProxy(host, port, proxyType, hostname)
-  if not socket then return false end
+  if not status then
+    return false, socket
+  end
   local req = "GET " .. test_url .. " HTTP/1.0\r\nHost: " .. hostname .. "\r\n\r\n"
   stdnse.print_debug("GET Request: " .. req)
   return test(socket, req, pattern)
@@ -104,8 +113,10 @@ end
 -- @param pattern The pattern to check for valid result
 -- @return the result of the function test (status and the request result)
 function test_head(host, port, proxyType, test_url, hostname, pattern)
-  local socket = connectProxy(host, port, proxyType, hostname)
+  local status, socket = connectProxy(host, port, proxyType, hostname)
-  if not socket then return false end
+  if not status then
+    return false, socket
+  end
   local req = "HEAD " .. test_url .. " HTTP/1.0\r\nHost: " .. hostname .. "\r\n\r\n"
   stdnse.print_debug("HEAD Request: " .. req)
   return test(socket, req, pattern)
@@ -118,8 +129,10 @@ end
 -- @param hostname The hostname of the server to send the request
 -- @return the result of the function test (status and the request result)
 function test_connect(host, port, proxyType, hostname)
-  local socket = connectProxy(host, port, proxyType, hostname)
+  local status, socket = connectProxy(host, port, proxyType, hostname)
-  if not socket then return false end
+  if not status then
+    return false, socket
+  end
   local req = "CONNECT " .. hostname .. ":80 HTTP/1.0\r\n\r\n"
   stdnse.print_debug("CONNECT Request: " .. req)
   return test(socket, req, false)
@@ -170,94 +183,127 @@ end
 --  @param port The port table
 --  @param proxyType A string with the proxy type. Might be "http","socks4" or "socks5"
 --  @param hostname The proxy destination hostname
---  @return socket A socket with the handshake already done
+--  @return status True if handshake succeeded, false otherwise
+--  @return socket A socket with the handshake already done, or an error if
 function connectProxy(host, port, proxyType, hostname)
   local socket = nmap.new_socket()
   socket:set_timeout(10000)
-  local try = nmap.new_try(function() socket:close() return false end)
+  local status, err = socket:connect(host, port)
-  try(socket:connect(host, port))
+  if not status then
-  if proxyType == "http" then return socket end
+    socket:close()
+    return false, err
+  end
+  if proxyType == "http" then return true, socket end
   if proxyType == "socks4" then return socksHandshake(socket, 4, hostname) end
   if proxyType == "socks5" then return socksHandshake(socket, 5, hostname) end
-  return false
+  socket:close()
+  return false, "Invalid proxyType"
 end
 
 --- Performs a socks handshake on a socket and returns it
 --  @param socket The socket where the handshake will be performed
 --  @param version The socks version (might be 4 or 5)
 --  @param hostname The proxy destination hostname
---  @return socket A socket with the handshake already done
+--  @return status True if handshake succeeded, false otherwise
+--  @return socket A socket with the handshake already done, or an error if
+--                 status is false
 function socksHandshake(socket, version, hostname)
   local resolve, sip, paystring, payload
   resolve, sip = hex_resolve(hostname)
-  local try = nmap.new_try(function() socket:close() return false end)
   if not resolve then
-    stdnse.print_debug("Unable to resolve hostname.")
+    return false, "Unable to resolve hostname"
-    return false
   end
   if version == 4 then
     paystring = '04 01 00 50 ' .. sip .. ' 6e 6d 61 70 00'
     payload = bin.pack("H",paystring)
-    try(socket:send(payload))
+    local status, response = socket:send(payload)
-    local response = try(socket:receive())
+    if not status then
+      socket:close()
+      return false, response
+    end
+    status, response = socket:receive()
+    if not status then
+      socket:close()
+      return false, response
+    end
+    if #response < 2 then
+      socket:close()
+      return false, "Invalid or unknown SOCKS response"
+    end
     local request_status = string.byte(response, 2)
+    local err = string.format("Unknown response (0x%02x)", request_status)
     if(request_status == 0x5a) then
-      stdnse.print_debug("Socks4: Received \"Request Granted\" from proxy server\n")
+      stdnse.print_debug('Socks4: Received "Request Granted" from proxy server')
-      return socket
+      return true, socket
     end
     if(request_status == 0x5b) then
-      stdnse.print_debug("Socks4: Received \"Request rejected or failed\" from proxy server")
+      err = "Request rejected or failed"
     elseif (request_status == 0x5c) then
-      stdnse.print_debug("Socks4: Received \"request failed because client is not running identd\" from proxy server")
+      err = "request failed because client is not running identd"
     elseif (request_status == 0x5d) then
-      stdnse.print_debug("Socks4: Received \"request failed because client's identd could not confirm" ..
+      err = "request failed because client program and identd report different user-ids"
-      "\nthe user ID string in the request from proxy server")
     end
-    return false
+    stdnse.print_debug('Socks4: Received "%s" from proxy server', err)
+    return false, err
   end
   if version == 5 then
     local payload = bin.pack("H",'05 01 00')
-    try(socket:send(payload))
+    local status, err = socket:send(payload)
-    local auth = try(socket:receive())
+    if not status then
+      socket:close()
+      return false, err
+    end
+    local auth
+    status, auth = socket:receive()
     local r2 = string.byte(auth,2)
 
     -- If Auth is required, proxy is closed, skip next test
     if(r2 ~= 0x00) then
-      stdnse.print_debug("Socks5: Authentication required")
+      err = "Authentication Required"
     else
       -- If no Auth is required, try to establish connection
       stdnse.print_debug("Socks5: No authentication required")
       -- Socks5 second payload: Version, Command, Null, Address type, Ip-Address, Port number
       paystring = '05 01 00 01 ' .. sip .. '00 50'
       payload = bin.pack("H",paystring)
-      try(socket:send(payload))
+      status, err = socket:send(payload)
-      local z = try(socket:receive())
+      if not status then
+        socket:close()
+        return false, err
+      end
+      local z
+      status, z = socket:receive()
+      if not status then
+        socket:close()
+        return false, z
+      end
       local request_status = string.byte(z, 2)
+      err = string.format("Unknown response (0x%02x)", request_status)
       if (request_status == 0x00) then
-        stdnse.print_debug("Socks5: Received \"Request Granted\" from proxy server\n")
+        stdnse.print_debug('Socks5: Received "Request Granted" from proxy server')
-        return socket
+        return true, socket
       elseif(request_status == 0x01) then
-        stdnse.print_debug("Socks5: Received \"General failure\" from proxy server")
+        err = "General Failure"
       elseif (request_status == 0x02) then
-        stdnse.print_debug("Socks5: Received \"Connection not allowed by ruleset\" from proxy server")
+        err = "Connection not allowed by ruleset"
       elseif (request_status == 0x03) then
-        stdnse.print_debug("Socks5: Received \"Network unreachable\" from proxy server")
+        err = "Network unreachable"
       elseif (request_status == 0x04) then
-        stdnse.print_debug("Socks5: Received \"Host unreachable\" from proxy server")
+        err = "Host unreachable"
       elseif (request_status == 0x05) then
-        stdnse.print_debug("Socks5: Received \"Connection refused by destination host\" from proxy server")
+        err = "Connection refused by destination host"
       elseif (request_status == 0x06) then
-        stdnse.print_debug("Socks5: Received \"TTL Expired\" from proxy server")
+        err = "TTL Expired"
       elseif (request_status == 0x07) then
-        stdnse.print_debug("Socks5: Received \"command not supported / protocol error\" from proxy server")
+        err = "command not supported / protocol error"
       elseif (request_status == 0x08) then
-        stdnse.print_debug("Socks5: Received \"Address type not supported\" from proxy server")
+        err = "Address type not supported"
       end
     end
-    return false
+    stdnse.print_debug('Socks5: Received "%s" from proxy server', err)
+    return false, err
   end
-  stdnse.print_debug("Unrecognized proxy type");
+  return false, "Invalid SOCKS version"
-  return false
 end
 
 --- Checks if two different responses are equal,

scripts/socks-open-proxy.nse

@@ -65,11 +65,8 @@ local function custom_test(host, port, test_url, pattern)
   test_url = url_table.path
 
   -- make requests
-  local err
+  status4, get_r4, cstatus4 = proxy.test_get(host, port, "socks4", test_url, hostname, pattern)
-  err, status4, get_r4, cstatus4 = pcall(proxy.test_get, host, port, "socks4", test_url, hostname, pattern)
+  status5, get_r5, cstatus5 = proxy.test_get(host, port, "socks5", test_url, hostname, pattern)
-  status4 = err and status4
-  err, status5, get_r5, cstatus5 = pcall(proxy.test_get, host, port, "socks5", test_url, hostname, pattern)
-  status5 = err and status5
 
   fstatus = status4 or status5
   if(cstatus4) then response[#response+1]="socks4" end
@@ -108,11 +105,8 @@ local function default_test(host, port)
   local test_url = "/"
   local hostname = "www.google.com"
   local pattern = "^server: gws"
-  local err
+  status4, get_r4, cstatus4 = proxy.test_get(host, port, "socks4", test_url, hostname, pattern)
-  err, status4, get_r4, cstatus4 = pcall(proxy.test_get, host, port, "socks4", test_url, hostname, pattern)
+  status5, get_r5, cstatus5 = proxy.test_get(host, port, "socks5", test_url, hostname, pattern)
-  status4 = err and status4
-  err, status5, get_r5, cstatus5 = pcall(proxy.test_get, host, port, "socks5", test_url, hostname, pattern)
-  status5 = err and status5
 
   fstatus = status4 or status5
   if(cstatus4) then response[#response+1]="socks4" end
@@ -129,10 +123,8 @@ local function default_test(host, port)
   test_url = "/"
   hostname = "www.wikipedia.org"
   pattern  = "wikimedia"
-  err, status4, get_r4, cstatus4 = pcall(proxy.test_get, host, port, "socks4", test_url, hostname, pattern)
+  status4, get_r4, cstatus4 = proxy.test_get(host, port, "socks4", test_url, hostname, pattern)
-  status4 = err and status4
+  status5, get_r5, cstatus5 = proxy.test_get(host, port, "socks5", test_url, hostname, pattern)
-  err, status5, get_r5, cstatus5 = pcall(proxy.test_get, host, port, "socks5", test_url, hostname, pattern)
-  status5 = err and status5
 
   if(status4) then fstatus = true; response[#response+1]="socks4" end
   if(status5) then fstatus = true; response[#response+1]="socks5" end
@@ -146,10 +138,8 @@ local function default_test(host, port)
   test_url = "/"
   hostname = "www.computerhistory.org"
   pattern  = "museum"
-  err, status4, get_r4, cstatus4 = pcall(proxy.test_get, host, port, "socks4", test_url, hostname, pattern)
+  status4, get_r4, cstatus4 = proxy.test_get(host, port, "socks4", test_url, hostname, pattern)
-  status4 = err and status4
+  status5, get_r5, cstatus5 = proxy.test_get(host, port, "socks5", test_url, hostname, pattern)
-  err, status5, get_r5, cstatus5 = pcall(proxy.test_get, host, port, "socks5", test_url, hostname, pattern)
-  status5 = err and status5
 
   if(status4) then fstatus = true; response[#response+1]="socks4" end
   if(status5) then fstatus = true; response[#response+1]="socks5" end