webMathematica™ Wolfram - Wolfram Research

164 webMathematica User GuideHere is a less-than-friendly expression, the sort of thing that could be sent as an attack.In[4]:= MSP`Utility`SecurityFunction@InsecureExprQ@ HoldComplete@ Run@ "telnetd"DDDDOut[4]= TrueValidation works by collecting all the symbols into a list and steadily reducing the list. If anysymbols remain after reduction, the expression is not secure. The reduction process works withlists of symbol and context names that either can be allowed or disallowed according to thefollowing steps.1. If AllowedContexts is set, remove symbols with these contexts, otherwise remove symbolswith contexts not in DisallowedContexts.2. If DisallowedSymbols is set, remove symbols not in DisallowedSymbols, otherwiseremove symbols that are in AllowedSymbols.3. If no symbols remain, the expression is secure; otherwise it is not secure.These tests allow you to be restrictive or flexible. If you use the allowed lists, you are restrictiveand have more security, whereas if you use the disallowed lists, you are less restrictive andhave less security. It is up to each individual site to decide the appropriate balance.When the server is started, a default security model is installed. This default security modellooks like this.This is the value of AllowedContexts.In[5]:=MSP`Utility`SecurityFunction@SecurityDataD@@1DDOut[5]= 8Global`