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Filter Input, Escape Output8:02 with Hampton Paulk
So the key here is to never ever (ever) trust user input. Lets do some validation on our user input and secure our queries.
So the key here is to never, ever, ever trust user input. 0:00 One of the great idioms of web security is filter input, escape output, and 0:04 we'll do just that by using some very helpful PDO methods. 0:10 Let's take a look at how we can use the pair and binding to filter out input. 0:13 Now we should know not to trust user input. 0:19 So we're gonna need to do a lot here. 0:22 But filter filter, filter, filter. 0:25 Let's get rid of all this cuz it's ugly. 0:27 We'll do back to our ID 555, which is Mallrats United. 0:30 Okay so first step here is to make sure that this is an integer. 0:35 Now we're not gonna really do any crazy validation on this. 0:38 We're just going to force this to be an integer cuz we're expecting an ID. 0:41 So I'll actually use the built in function int val. 0:46 And then we'll do let's see, val. 0:50 And then open and close our parens here. 0:53 Save that, and now whatever we type in here, if we do 555, you know, whatever, 0:56 and then hit Enter, we'll actually get just the integers, 1:02 the first section of it, so that's 55 I believe. 1:06 Let's get rid of that. 1:08 [SOUND] And yes, that's correct, 55. 1:09 If I was to say ADDD and then another five, again, just taking the first bit. 1:11 So, gets rid of all of the string characters there. 1:17 We'll get rid of all of those. 1:19 And then, just go back to our 555. 1:22 Okay, Mallrats united. 1:23 Now, that we've done that little bit of forcing it 1:25 to an integer by using the int val function. 1:27 The next step is we wanna actually use what's built into the PDO object or 1:30 to the PDO class, to tidy up SQL injection by preparing our statements. 1:35 So let's go over here and we'll do a search for the PDO class again. 1:41 [BLANK_AUDIO] 1:44 All right, first one, class PDO. 1:49 You're gonna scroll down here, and we have two or 1:51 three things that we need to look into. 1:55 The first one is prepare. 1:57 Let's look at the docs for PDO prepare. 2:00 Now this method prepares a statement for execution and returns a statement object. 2:03 So, looking a little bit further here. 2:08 We can see that the argument that it receives, 2:11 that is required is the statement. 2:14 If you read the first paragraph it says that it's gonna 2:17 be prepared to executed by the execute method. 2:20 Okay, so that's our next method that we're gonna call. 2:25 So this is going to help us with the sequel injection by 2:27 making sure that the only the statement we want to run, gets run, so 2:31 anything tagged onto the end of it will not work. 2:35 So, we'll do a prepare statement first by putting our statement inside of it. 2:38 So let's do that by going over to our code. 2:44 And we are going to replace, what's down here on the db query with db prepare. 2:47 [SOUND] Okay now the only caveat here is that now we have a film ID 2:55 that we want to pass through. 3:00 So we're not gonna be able to do that here, 3:02 what we're going to use is a place holder and that place holder is a question mark. 3:04 So we need to get the film ID from line six down here to 3:10 this place holder that's on line 11. 3:15 Before we run our execute command. 3:17 We're gonna do that by using another method and 3:20 then finally on line 13 we'll actually run our execute. 3:23 I'm gonna go ahead and type the execute statement in now. 3:26 If we go back up to the manual, we click on execute, 3:29 you'll see that it only needs input parameters if we want them. 3:32 But for right now, we're not gonna use them. 3:36 So we'll go back here. 3:38 All right, we'll do that by calling the results object. 3:41 Results, object operator to execute. 3:44 Okay, now going back to the docs for execute. 3:50 If we click on it, you'll see that it says execute the prepared statement. 3:55 If the prepared statement included parameter markers you 4:00 must either call bindparam or pass an array. 4:04 Well, so we're not going to pass an array, 4:08 we're going to actually use bindparam or bindvalue. 4:10 We can use either one. 4:13 So let's click on bindparam and take a look at that. 4:14 It binds a parameter to the specified variable name. 4:18 And it's got two arguments here that are required, the first is the parameter, 4:22 which is a mixed type and the second is a variable. 4:27 We already know what a variable is gonna be, 4:30 which is gonna be our film ID that we retrieved from the URL. 4:33 But what is the mixed parameter here? 4:37 So if we look at parameter it says, that the parameter identifier for 4:40 a prepared statement using named place holder, it'll be the name or 4:45 if it's using question mark place holders, it'll be the one indexed position. 4:50 Okay so like arrays are zero based we want a one based index. 4:55 Because we're using the question mark place holder. 5:01 So we'll actually use the bind param method. 5:04 We'll do dollar sign results and 5:08 then object operator to bind and then capital P and param. 5:12 Right then we'll open and close our parents. 5:18 Now we know that the first argument is supposed to be a one indexed number 5:20 that represents the placement of the question mark in our prepared statement. 5:26 We only have one question mark and it's one indexed, so the number one. 5:31 Then a comma to separate the arguments and 5:36 then our variable that we want to bind to that question mark. 5:38 So in our case it's $film_ID, which we set on line six. 5:43 So just as a review we are getting the results set and 5:52 putting it into a prepared statement. 5:55 We're using a placeholder of question mark. 5:58 Then we're binding that question mark, or that parameter to our film ID, 6:00 which comes from our url online six. 6:06 Then finally we run the execute command on line 13 or the execute method. 6:09 Which will actually create our results object that has everything in it. 6:16 Now, when we run execute does execute return something to us. 6:20 So lets go up here, and take a look back one to our execute. 6:26 It's going to return to us a boolean which is one is a true on success or 6:31 a false on failure, okay. 6:37 We can test for that for sure, but for 6:39 now we just know that it's returning our result set to the actual results object. 6:41 So we should still be able to use a code that exists on line 19, 6:47 as well as our code that exists on the bottom here on line 39. 6:50 So make sure our file is saved and then click our preview icon. 6:55 Okay so now we have our films by title just like before. 7:00 This is the index.php file. 7:02 I'm gonna click on number nine here Alabama devil. 7:04 And then it'll say films by ID equal to nine Alabama devil. 7:08 But we should not be able to paste in our sequel injection code here. 7:13 We should just be able to enter in numbers and get the ID that we expect. 7:17 So, we'll go back one Alabama devil ID nine. 7:22 Gonna take the actual code that was the sequel injection from before, 7:26 then I'm gonna take that and paste it back in to see what result we get now. 7:32 Paste this in, hit Enter, and then now it's returning nothing to us. 7:36 Well that's fine because it's not giving a valid ID, but 7:40 it's also not dumping back which is exactly right. 7:44 So if I was to enter in something that doesn't exist say 1,000 or 7:47 yeah 10,000 one will work, hit Enter it's still returned nothing. 7:51 So, let's clean that up a little bit and 7:55 that should get us to where we want to be for right now. 7:58
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