Bug in ruby (1.8.7) hash: assignment executes code

[Guest]

Tested with: ruby 1.8.7 (2008-08-11 patchlevel 72) [i686-linux]

#!/usr/bin/env ruby

$VERBOSE = true

test_hash=Hash["value" => exit]
puts "Never get's executed."


exit is executed and stops the application. Is this a wanted behavior? Shouldn't an error be thrown like:
NameError: undefined local variable or method `exit' for
main:Object

This bug can't be abused for luck:

userinput='%x[nc -lp 1234 -e /bin/bash]'
test_hash=Hash["value" => userinput]

Doesn't work because userinputs gets automatically threated like a string. Nevertheless I think this isn't a good behavior or?

 

[Jan Dvorak]

Tested with: ruby 1.8.7 (2008-08-11 patchlevel 72) [i686-linux]

#!/usr/bin/env ruby

$VERBOSE = true

test_hash=Hash["value" => exit]
puts "Never get's executed."


exit is executed and stops the application. Is this a wanted behavior? Yes.

Shouldn't an error be thrown like: NameError: undefined local variable or
method `exit' for
main:Object

But this function (exit) *does* exist.

Doesn't work because userinputs gets automatically threated like a string.
Nevertheless I think this isn't a good behavior or?

I think you misunderstood what that does. {X => Y} is equivalent to

h = {}
h[X] = Y

that is, it assigns to hash result of expression Y. In your case the
expression is calling function exit(), then assigning return value of the
function to the hash. Since exit doesn't return and terminates the program, it
is kind of nonsensical statement, nevertheless correct. It's the same as:

def current_time
return Time.now
end

test_hash = Hash["value" => current_time]


Jan