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fix($parse): block assigning to fields of a constructor #12860

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fix($parse): block assigning to fields of a constructor #12860

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22 changes: 22 additions & 0 deletions src/ng/parse.js
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Original file line number Diff line number Diff line change
Expand Up @@ -102,6 +102,16 @@ function ensureSafeFunction(obj, fullExpression) {
}
}

function ensureSafeAssignContext(obj, fullExpression) {
if (obj) {
if (obj === (0).constructor || obj === (false).constructor || obj === ''.constructor ||
obj === {}.constructor || obj === [].constructor || obj === Function.constructor) {
throw $parseMinErr('isecaf',
'Assigning to a constructor is disallowed! Expression: {0}', fullExpression);
}
}
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So we only care about built-in constructors?

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we care the ones an expression can invoke and can be used to break the sandbox... the only other I can think about is Scope, but I really have no idea if it can be maliciously used. The alternative would be blocking to any property named constructor, but it might be just too much and there might be valid uses.

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So I guess we can't protect against developers putting stuff on the scope via a controller, such as the window object, for instance?

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there are other protections in place that prevent any form of access to several objects. Eg. DOM nodes and window

}

var OPERATORS = createMap();
forEach('+ - * / % === !== == != < > <= >= && || ! = |'.split(' '), function(operator) { OPERATORS[operator] = true; });
var ESCAPE = {"n":"\n", "f":"\f", "r":"\r", "t":"\t", "v":"\v", "'":"'", '"':'"'};
Expand Down Expand Up @@ -816,6 +826,7 @@ ASTCompiler.prototype = {
'ensureSafeMemberName',
'ensureSafeObject',
'ensureSafeFunction',
'ensureSafeAssignContext',
'ifDefined',
'plus',
'text',
Expand All @@ -824,6 +835,7 @@ ASTCompiler.prototype = {
ensureSafeMemberName,
ensureSafeObject,
ensureSafeFunction,
ensureSafeAssignContext,
ifDefined,
plusFn,
expression);
Expand Down Expand Up @@ -1050,6 +1062,7 @@ ASTCompiler.prototype = {
self.if_(self.notNull(left.context), function() {
self.recurse(ast.right, right);
self.addEnsureSafeObject(self.member(left.context, left.name, left.computed));
self.addEnsureSafeAssignContext(left.context);
expression = self.member(left.context, left.name, left.computed) + ast.operator + right;
self.assign(intoId, expression);
recursionFn(intoId || expression);
Expand Down Expand Up @@ -1175,6 +1188,10 @@ ASTCompiler.prototype = {
this.current().body.push(this.ensureSafeFunction(item), ';');
},

addEnsureSafeAssignContext: function(item) {
this.current().body.push(this.ensureSafeAssignContext(item), ';');
},

ensureSafeObject: function(item) {
return 'ensureSafeObject(' + item + ',text)';
},
Expand All @@ -1187,6 +1204,10 @@ ASTCompiler.prototype = {
return 'ensureSafeFunction(' + item + ',text)';
},

ensureSafeAssignContext: function(item) {
return 'ensureSafeAssignContext(' + item + ',text)';
},

lazyRecurse: function(ast, intoId, nameId, recursionFn, create, skipWatchIdCheck) {
var self = this;
return function() {
Expand Down Expand Up @@ -1364,6 +1385,7 @@ ASTInterpreter.prototype = {
var lhs = left(scope, locals, assign, inputs);
var rhs = right(scope, locals, assign, inputs);
ensureSafeObject(lhs.value, self.expression);
ensureSafeAssignContext(lhs.context);
lhs.context[lhs.name] = rhs;
return context ? {value: rhs} : rhs;
};
Expand Down
26 changes: 26 additions & 0 deletions test/ng/parseSpec.js
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Expand Up @@ -2703,6 +2703,32 @@ describe('parser', function() {
'');
}).toThrow();
});

it('should prevent assigning in the context of a constructor', function() {
expect(function() {
scope.$eval("''.constructor.join");
}).not.toThrow();
expect(function() {
scope.$eval("''.constructor.join = ''.constructor.join");
}).toThrow();
expect(function() {
scope.$eval("''.constructor[0] = ''");
}).toThrow();
expect(function() {
scope.$eval("(0).constructor[0] = ''");
}).toThrow();
expect(function() {
scope.$eval("{}.constructor[0] = ''");
}).toThrow();
// foo.constructor is the object constructor.
expect(function() {
scope.$eval("foo.constructor[0] = ''", {foo: {}});
}).toThrow();
// foo.constructor is not a constructor.
expect(function() {
scope.$eval("foo.constructor[0] = ''", {foo: {constructor: ''}});
}).not.toThrow();
});
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For good measure we could also test assigning to a variable that has been set to a constructor:

expect(function() {
  scope.$eval("foo = {}.constructor; foo.join = ''");
}).toThrow();

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done

});

it('should call the function from the received instance and not from a new one', function() {
Expand Down