Today we continue to discuss jigsaw.Efficient, low effort mashup isolation by James Mickens and Matthew Finifter. Mashups are web applications that contain code from different principals.
Jigsaw lets mashups be isolated with its framework and lets them selectively expose private state. We were discussing the related work. There were two techniques that came pretty close to Jigsaw. First, there was ObjectView with its flexible security policy. However it seems too clunky and an overkill as compared to Jigsaw declarative public and private keywords. Second was IFC which required developers to annotate and the engine to apply security tags to variables. Again the public private syntax is much easier. Moreover tagging variables is not suited for managing access to visual fields. Jigsaw does this with the full flexibility that case allows.
Conscript is another library that modifies the browser engine to apply security. Integrators specify policy code and these are attached at specific execution points such as the start of a function or the load of a module. These policies are similar to ObjectView policies and have the same advantages but jigsaw syntax is simpler.
OMash comes closer to Jigsaw in that it allows public functions to be declared for sharing. However it does not enforce private only access by default. Moreover the return value from the function can divulge sensitive data. On the other hand, Jigsaw allows both public and private and supports proxies.
MashupOS provides a new model where services instances are similar to the processes on an operating system and get partitioned physical resources. They communicate with each other using pass by value messages. This is elaborate by itself and still has shortcomings that Jigsaw does not. Jigsaw avoids such communication altogether with its pass by reference semantics.
CommonJs introduces another technique that gives each library it's own namespace and expose functions. However it suffers from the same limitations with regard to property manipulation and return value exploit as OMash. This is because the namespace are implemented using closure which allow prototypes to be transformed as opposed to Jigsaw's box.
#Google code jam
Ominoes are jigsaw puzzle pieces made by joining unit square pieces along one or more of their edges. An X ominous has X such unit squares. Richard picks one of the X Ominoes and Gabrielle uses that piece and Amy other piece or their copies to fill an RxC grid. If Gabrielle fills the grid she wins otherwise Richard wins. Given arbitrary X, R, C determine who wins
Void GetWinner (int X, int R, int C)
{
String answer = "Richard";
If ((R×C)%X == 0){
if ((R%X==0 || C%X==0) && C >X-1 && R > X-1)
{
answer = "Gabrielle";
}
Console.Writeline (answer);
}
Conscript is another library that modifies the browser engine to apply security. Integrators specify policy code and these are attached at specific execution points such as the start of a function or the load of a module. These policies are similar to ObjectView policies and have the same advantages but jigsaw syntax is simpler.
OMash comes closer to Jigsaw in that it allows public functions to be declared for sharing. However it does not enforce private only access by default. Moreover the return value from the function can divulge sensitive data. On the other hand, Jigsaw allows both public and private and supports proxies.
MashupOS provides a new model where services instances are similar to the processes on an operating system and get partitioned physical resources. They communicate with each other using pass by value messages. This is elaborate by itself and still has shortcomings that Jigsaw does not. Jigsaw avoids such communication altogether with its pass by reference semantics.
CommonJs introduces another technique that gives each library it's own namespace and expose functions. However it suffers from the same limitations with regard to property manipulation and return value exploit as OMash. This is because the namespace are implemented using closure which allow prototypes to be transformed as opposed to Jigsaw's box.
#Google code jam
Ominoes are jigsaw puzzle pieces made by joining unit square pieces along one or more of their edges. An X ominous has X such unit squares. Richard picks one of the X Ominoes and Gabrielle uses that piece and Amy other piece or their copies to fill an RxC grid. If Gabrielle fills the grid she wins otherwise Richard wins. Given arbitrary X, R, C determine who wins
Void GetWinner (int X, int R, int C)
{
String answer = "Richard";
If ((R×C)%X == 0){
if ((R%X==0 || C%X==0) && C >X-1 && R > X-1)
{
answer = "Gabrielle";
}
Console.Writeline (answer);
}
The problem can also be solved recursively with the assumption that a square of size greater than X and edge equal to min (R,C) can be filled by X dominoes and accounting for different orientations and positions of the remaining
Another way to solve the problem is to eliminate R-X and C-X and see if it can be solved for X by X as long as those R-X and C-X are divisible by X.
I am going to get a caprese sandwich and squash soup from yellow dot cafe.
Another way to look at this problem is to check if X+1 is greater than double the minimum of R and C in which case Richard wins because essentially you are using a vertical line after X.
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