Hiding true database object ID in url's

What would be useful solutions for hiding true database object ID in URL for security purposes? I found that one of the solutions would be:

1) Using hashids open source project

2) Using something like same old md5 on creation of the object to generate hash and store it in database, then use it in url's and querying by them, but the drawback is that querying by auto-incremented primary keys (IDs) is faster than hashes. So I believe the possibility to hash/unhash would be better?

Also as I'm on Symfony, are there maybe bundles that I could not find or built in functionalities that would help?

Please tell me what you found useful based on your experiences.

Answers


This question has been asked a lot, with different word choice (which makes it difficult to say, "Just search for it!"). This fact prompted a blog post titled, The Comprehensive Guide to URL Parameter Encryption in PHP .

What People Want To Do Here

What People Should Do Instead

Explanation

Typically, people want short random-looking URLs. This doesn't allow you much room to encrypt then authenticate the database record ID you wish to obfuscate. Doing so would require a minimum URL length of 32 bytes (for HMAC-SHA256), which is 44 characters when encoded in base64.

A simpler strategy is to generate a random string (see random_compat for a PHP5 implementation of random_bytes() and random_int() for generating these strings) and reference that column instead.

Also, hashids are broken by simple cryptanalysis. Their conclusion states:

The attack I have described is significantly better than a brute force attack, so from a cryptographic stand point the algorithm is considered to be broken, it is quite easy to recover the salt; making it possible for an attacker to run the encoding in either direction and invalidates property 2 for an ideal hash function.

Don't rely on it.


  1. Quote from the site:

Do you have a question or comment that involves "security" and "hashids" in the same sentence? Don't use Hashids.

  1. I'd use true encryption algorithm, like function openssl_encrypt (for example), or something like this. And encrypt ids when passing outside, decrypt when using in your code (like for db queries).

And I won't recommend storing ids in a base like any kind of encrypted "garbage", in my opinion its very inconvenient to hash your real ids. Keep it clean and pretty inside and encrypt for external display only.


Following your idea, you just need to cipher your IDs before writing the URL to HTML page and decipher them when processing those URLs.

  • If you want just security by obscurity, which is sufficient for, maybe 99% of curious people out there who likes to iterate over IDs in URLs, you use something simple like base64 or rot13. Of course, you can also precalculate those "public IDs" and store in the database, not encrypting each time the URL is being shown to end user.
  • If you want true security you have to encrypt them with some serious asymmetric cypher, storing both keys at your side, as you essentially talking with yourself and don't want a man-in-the-middle attack. This you will not be able to precalculate as at each encrypting there'll be different cyphertext, which is good for this cause.

In any case, you need something two-way, so if I were you I'd forget about word "hash", hashes are for purposes different from yours.

EDIT: But the solution which every blog out there uses for this task for several years already is just to utilize URL rewriting, converting, in your case, URLs like http://example.com/book/5 to URLs like http://example.com/rework-by-37signals. This will completely eradicate any sign of database ID from your URL.

Ideologically, you will need something which will uniquely map the request URL to your database content anyway. If you hide MySQL database IDs behind any layer of URL rewriting, you'll just make this rewritten URL a new ID for the same content. All you gain is protection from enumeration attacks and maybe SEF URLs.


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