Asked  7 Months ago    Answers:  5   Viewed   26 times

This question got me thinking about bare strings.

When PHP sees a string that's not enclosed in quotes, it first checks to see if it's a constant. If not, it just assumes it's a string and goes on anyway. So for example if I have

echo $foo[bar];

If there's a constant called bar it uses that for the array key, but if not then it treats bar as a bare string, so it behaves just like

echo $foo["bar"];

This can cause all kinds of problems if at some future date a constant is added with the same name.

My question is, is there any situation in which it actually makes sense to use a bare string?

 Answers

24

Nope, I can not see a single instance where it would make sense, and it always is dangerous. Using strings without quotes should absolutely be reserved to address constants. I don't understand how the inventors of PHP could decide to introduce this ridiculous behaviour at all - it makes the proper use of constants almost impossible (because if you try to access a constant that has not been defined, PHP will silently and stupidly generate a string) without giving any benefit.

Wednesday, March 31, 2021
 
Revent
answered 7 Months ago
52

is that what you wanted? i hope that code is compiling :)

$string = 'My nAmE is Tom.';
$array = array("name","tom");
if(0 < count(array_intersect(array_map('strtolower', explode(' ', $string)), $array)))
{
  //do sth
}
Thursday, June 10, 2021
 
daiscog
answered 5 Months ago
84
$array = str_split("0123456789bcdfghjkmnpqrstvwxyz");

str_split takes an optional 2nd param, the chunk length (default 1), so you can do things like:

$array = str_split("aabbccdd", 2);

// $array[0] = aa
// $array[1] = bb
// $array[2] = cc  etc ...

You can also get at parts of your string by treating it as an array:

$string = "hello";
echo $string[1];

// outputs "e"
Tuesday, June 22, 2021
 
cbcp
answered 4 Months ago
88

As pointed out in the other answer, RDRAND is seeded with true randomness. In particular, it frequently reseeds its internal CSPRNG with 128 bits of hardware-generated randomness, guaranteeing a reseed at least once every 511 * 128 bits. See section 4.2.5 of this doc:

https://software.intel.com/en-us/articles/intel-digital-random-number-generator-drng-software-implementation-guide

So in your examples, you used a single 128-bit seed to generate 10 million random draws from rabbit_extract. In the RDRAND version, you had the equivalent of 2.5 million 128-bit draws, meaning that the CSPRING was reseeded at least 2,500,000/511 = 4,892 times.

So instead of 128 bits of entropy going into your rabbit example, there were at least 4,892*128 = 626,176 bits of entropy going into the RDRAND example.

That's much, much more entropy than you're going to get in 0.361 seconds without hardware support. That could matter if you're doing stuff where lots of real randomness is important. One example is Shamir secret sharing of large quantities of data -- not sure if there are others.

So in conclusion -- it's not for speed, it's for high security. The question of whether it's backdoored is troubling, of course, but you can always XOR it with other sources, and at the very least it's not hurting you.

Wednesday, August 11, 2021
 
tika
answered 2 Months ago
96

I've used them, although I'd never heard the term code cave until today. The Wiktionary definition suggests that a code cave is something the cracker finds in the executable he or she is attempting to crack. The question you cite doesn't use it that way. Instead, it suggests the code cave is being allocated with VirtualAllocEx to create a brand new block of memory in the target process. That removes the need to search for unused space in the target, and it guarantees you'll have enough space to put all your new code.

Ultimately, I think a "code cave" is just a place to store run-time-generated code. There doesn't have to be any nefarious purpose to that code. And at that point, the question of what a code cave is becomes entirely uninteresting. The interesting parts are what reasons there are for generating code at run time, and what techniques there are for making sure that new code gets run when you want it.

Monday, September 6, 2021
 
Andrew Burton
answered 2 Months ago
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