Noob question here. I'm overhauling some "Search" pages in a real estate website. I would like to be able to generate an unique ID (hash?) which contains in itself all the parameters of the search, e.g., the user would be given an URL in the form of http://search.example.com/a95kl53df-02, and loading this URL would repeat the exact same search.
Some of the search parameters are simply one of several options, some are integers, and there are also keywords (which I'll just append after the ID, I guess). What's the general approach to cramming this data into a string? I'm fairly comfortable with PHP/MySQL, but my practical experience is next to none, so I don't know "how it's done".
EDIT: I do not need the string to be random, and, indeed, I need the process to be two-way. Perhaps hash isn't the correct term, then. As for why - I'm doing this for the sake of brevity, since current URLs contain at least 22 GET parameters.
I have the nasty habit of always asking my questions on the Interwebs a bit too early, reconsiderations popping right into my head as soon as I have posted. I'm currently drafting a possible solution. I'm still open to any suggestions, though.
Hashes are not unique
A hash is NOT unique, you can't use it. Any hash can result from an infinite number of given strings.
You don't need randomness, just a unique token
You should just generate a unique token with the help of the database (even just an autoindexed id). You can create a cronjob that deletes old searches after a while.
That table would minimally contain the unique token plus the original search string.
Possible implementation
User does a search
Search params are stored in database, token is returned
Token is given to user in some way (e.g. do you want to save this search for later)
When user wants to repeat search with token, search string is retrieved from db and search run
You could use something like mcrypt() on $_SERVER['QUERY_STRING'], and then decrypt it if an encrypted URL is passed in. However, there are all sorts of problems here and I recommend not doing that.
Based on your edit that you are doing this because of a complicated URL, I would suggest that hashing is going to make the problem worse. If you have an error with the URL, you now have multiple places it could be going wrong.
Just make a random key that you then lookup in a simple flat-file database. You could check whether the URL is already in the database and then return the key if it is.
Another advantage of this system is that if your URL structure changes, then you can change all the URLs in the database and the users' short URLs still work.
Well to be random (which by the way you never can be), you can hash let us say the microtime (which is random-sh, since there is a low possibility that 2 users will search at the same time) along with some salt, with what you can use is the query id:
so something like:
$store_unique = md5(microtime().$queryID);
//the $store_unique you can save to the db with the query params
//then when anyone goes to the random url, you can check it against the db
UPDATE
Due to the comments below, I offer another solution (which can be more unique):
$store_unique = microtime(). "-" .$queryID;
//the $store_unique you can save to the db with the query params
//then when anyone goes to the random url, you can check it against the db
Related
I need to include the user ID in the URL like this:
http://www.example.com/user.php?id=123456
However, there is a problem. If a user manually changes the ID in the URL to 123455 for example, that could potentially lead to an erroneous update of the database.
For this reason, I need to somehow make the ID in the URL unreadable to the user so they can't just subtract 1 from the ID and be able to alter another user's data.
Another requirement is that the ID in the URL must be usable, meaning that whatever we do to it, PHP must have a way of figuring out the database row corresponding to that particular ID.
There are 2 possible solutions I can think of. I would be happy to hear your opinion on which one is better. If there's an even better solution that I haven't thought of, please let me know.
Including an encrypted version of the ID in the URL - that should make it extremely difficult for a user to just change the ID in the URL and guess another user's encrypted ID. It's also easy for PHP to decrypt the ID when needed and use it to request the user's data from the database.
Adding a new column called "hash" in the "users" table in the database. As you may have guessed, every user will have a unique random hash or UUID stored in the database which will be included in the URL. That makes guessing another user's hash very unlikely. PHP can easily retrieve the user's data by using the hash in the database query.
If a user manually changes the ID in the URL to 123455 for example, that could potentially lead to an erroneous update of the database.
The way to solve this problem is to have sanity checks on the server so the user is not allowed to erroneously update the database. You either want some sort of permission checking ("this user is not allowed to update this record"), or other consistency checks that ensure no updates can be made erroneously ("the user is generally allowed to update this record, but right now it would cause a conflict with something else, so we won't").
You will have to include some id in the URL, and a user will always be able to change that id. At best you can make valid ids harder to guess by using something other than consecutive numbering, but that doesn't solve the underlying problem that your server has no sanity checks. Don't fault the user for generating errors, it's your code that's allowing it.
You should use sessions for this, not GET[] parameters, sessions are the tool for this Job. You can try the solutions you think of but from my point of view using sessions will be a lot better and simpler to use and implement.
But if you need to do something like the classic "recover my acount" so you don't have a way to log in you user, them you may use a hash in an URL and send it by email to "ensure" your user is the one who get's the URL.
I was hoping to get some advice on a particular task I'm trying to implement.
I have a table that stores secure data and returns an ID as a representation of that data. No problems there. So, for example, if a social security number is stored, the code generates a representational ID and stores the social security number in an encrypted fashion in the table. The encryption is done using envelope encryption.
Here's my issue. Every time a new value comes in, I don't want to create a new ID if the data already exists. I need to check to see if the value already exists and, if so, return the existing ID. The problem I have is that the encrypted value is different each time and I certainly can't decrypt every value in the database to check for a duplicate. I could create a one way hash and store that as well but, if I do, I would need to salt it for security purposes and the hash will be different every time.
So I'm hoping to get advice/recommendations on how to achieve this? How to check for duplicates when the value is stored in an encrypted fashion.
Thank you!
I have a website where users can upload blog posts. This website is built entirely by me, no framework documentation to look through.
I've been using Mysql's Primary key as the page ID in the url, but i don't like this as it gives away too much information to the user.
The id appears somewhat like this
www.website.com/view?post=97
Youtube uses an 11 letter combination and looks somewhat like
watch?v=wEoFhRCUEs8 // *Not a plug*
I was thinking of encrypting the ID in an MD5, but 1) this is far too long, 2) Not the intended use of MD5.
Any ideas on how sites like facebook, stackoverflow, youtube etc encrypt each ID whilst ensuring that it is unique?
I'm also unsure if it is best to save a secondary unique ID in mysql, or just parse it through a function that converts it every time I need it.
Thanks
I can provide you the logic:
first there is a post //
then it is tried to be inserted into the database //
Before inserting into the database //
Generate a random string //
As soon as you generate the random string, check in the database if it is taken //
if it is taken, generate a new string //
else utilize that string //
now insert all the necessary data into the database //
Done //
You are actually on the right track with MD5. Basically what you need to do is create a simple encyption based on the post id. As long as it is not security related I'd write a quick 2 way hashing algorithm that allows you to convert 97 to "wEoFhRCUEs8" and vice versa. That way you can look up posts later.
Probably something that just bit shifts the number and xors it into a "secret" string.. etc...
If you want to go a little more secure try the mcrypt lib, depending on algorithm you can limit the output size.
If you don't do a reversable encryption then you have no choice but to store your unique string with your post so you can look it up later.
Using PHP, I have a MySQL database with an Actions table, in which a user optionally assigns actions to some pages in their website. Each such assignment results in an action row, containing (among other things) a unique ActionId and the URL of the appropriate page.
Later on, when in a context of a specific page, I want to find out if there is an action assigned to that page, and fetch (SELECT) the appropriate action row. At that time I know the URL of my page, so I can search the Actions table, by this relatively long string. I suspect this is not an optimal way to search in a database.
I assume a better way would be to use some kind of hashing which converts my long URL strings into integers, making sure no two different URLs are converted into the same integer (encryption is not the issue here). Is there such a PHP function? Alternatively, is there a better strategy for this?
Note I have seen this: SQL performance searching for long strings - but it doesn't really seem to come up with a firm solution, apart from mentioning md5 (which hashes into a string, not to integer).
The hashing strategy is a good strategy.
Dealing with the URL strings might indeed be a problem, because they can be very long, and contain a lot of special chars, which are always problematic for MySQL search (REGEXP or LIKE).
That is why hashing solves the problem. Even md5 which is not a good hashing function to hash passwords (because it's not secure anymore), is good to hash URL.
This way you will have http://www.stackoverflow.com changed into 4c9cbeb4f23fe03e0c2222f8c4d8c065, and that will be pretty much unique (unless you are very very unlucky).
Once you have your md5_url field set up, you can search with :
SELECT * FROM Actions where md5_url=?
Where the ? is an md5($url) of current URL.
Of course be sure to set an index on your md5_url field :
ALTER TABLE Actions
ADD md5_url varchar(32),
ADD KEY(md5_url);
If you add an index to the column, the database should take care of efficiency for you, and the length of the URL should make no difference.
I need help on coming up with a strategy to handle object ids in a PHP/MySQL application I'm working on. Basically, instead of having a URL look like this:
/post/get/1
I'm looking for something like:
/post/get/92Dga93jh
I know that security-through-obscurity is useless (I have an ACL system in place to handle security) but I still need to obscure the ids. This is where I'm stuck.
I thought about generating a separate public id for each DB row but have been unable to find a way to create truly unique ids.
I suppose I could encrypt and decrypt a MySQL auto increment row id as it leaves and enters my app, but I'm not sure how 'expensive' PHP's encryption and decryption methods are. Additionally, I need to make sure that the obscured id remains unique so that it doesn't decrypt into the wrong value.
Also, since my domain objects are related to each other, I want to avoid any unnecessary strain on MySQL if I decide to go with generating and storing an obscure id in the tables.
I'm beating my head against the wall because I feel like this is a common scenario, yet can't figure out what to do. Any help is greatly appreciated!
I'd just use a salted md5. It's secure for 99% of the cases. The other 1% will be when you are wacking your head on the wall cause you got your data stolen by a pro-hacker and it becomes critical to minimize the impact of it.
So:
$sql = 'SELECT * FROM my_table WHERE MD5(CONCAT(ID, "mysupersalt")) = "'.$my_checked_url_value.'"';
And generating the same thing from PHP can be done using similar strategy:
link text
Hope this is what you're looking for..
As long as you given 9-char base62 string - you could follow this strategy:
Generate a number from 1 to 13537086546263552 (62 ^ 9)
Convert it to the base62 string
Try to insert to the database (you're supposed to have the unique index over id field)
If ok - do nothing
If not ok - repeat 1-3
Use a one-way hash like md5, etc.
Depends on the application really, if its super essential that you have IDs from which the user can never 'guess' the original IDs, then use a recursive call to db to generate a unique public ID.
If on the other hand, you just need the IDs to look different without any security worries if someone can 'guess' the original ID, and are concerned with the performance, you can come up with a quick and basic math equation to generate a unique id on the fly and decode it as well when the URL is accessed.
(I know its a HACK, but gets the job done for a lot of cases)
E.g. If I access /blog/id/x!1#23409235 (which means /blog/id/1)
In the code, I can decode above by:
$blogId = intval(substr($_GET['id'], 4)) - 23409234;
and of course, while generating the URL, you add 23409234 to the original URL's id and prefix it with some random char bits..
Oh and you can use Apache's mod_rewrite to do all these calculations.
The probably easiest way is checking whether there is already such a record in a
do {
$id = generateID();
}
while(idExists($id));
loop. There shouldn't be to many duplicate IDs so in most cases there are only two queries most the time: Checking and Inserting.