I don't know much about the use of some random strings in URL.
As far as I used, I learned that it can be used where any user simply cannot guess the URL.
First noticed in phpmyadmin, as blowfish secret. and the URL said token=secret . I don't know about tokens.
My questions is - What are these strings anyway and are these random strings called tokens ?
There are many different uses of random strings in URLs. Your question is difficult to answer because you give us no examples, but I can describe one possible use.
A commercial site may allow users to create wish lists of products. The site may want users to be able to forward friends the URL of their wish list, but make them hard to guess. This can be implemented by adding a WishCode to the User record. Any time a user makes a wish list, create a string of random URL-compatible characters:
UserID Name WishCode
1076 Joe Bloggs a792f207a98d7db431bf3a56ab364e35
When the user adds a product to his wish list, add the product code to a Wish table:
UserID productID
1076 483692
1076 547320
1076 73028
Make the Wish List page accept a WishCode URL; e.g.:
http://myCompanycom/wishlist/a792f207a98d7db431bf3a56ab364e35
When a browser submits this URL, look up the UserID from the User table, and generate a page with all the products from this user's wish list. Note that it is very difficult to guess a valid wish URL.
Also note this has nothing to do with hashing, secrets, or passphrases, nor would I call this a "token". They are unrelated concepts.
Related
I have easily guessable internal identifiers (auto increasing numbers) and I'd like to give my clients access to resources based on these identifiers.
Of cause I cannot provide them with an URL like:
https://example.com/order/13
because they could easily guess how to access order #14 from this URL.
I therefore thought about providing them with a salted hash of the identifier like:
https://example.com/order/4643ef…
where
4643ef… = sha256(13 + 'supersecretsalt')
Is this a good approach from a security perspective?
First of all, your should not be granting access to any resource simply based on a uri. In other words, user A should not be able to access a resource that belongs to user B even if he knows the relevant uri. To mitigate this, you should add some form of authentication and authorization before allowing access to any (confidential?) resources.
That said, if you'd still like to obfuscate the uri, you can probably use a GUID for this instead of generating any kind of hash. Instead, fore each order ID, simply store a GUID together with it, and then look that ID up whenever the GUID is used in an url.
Sidenote: If you do want to let your customers look up some order-details based simply on a url (i.e. without requiring identification), you might at least make the availability of the resource temporary. You can do this by storing e.g. a valid until-date together with the GUID.
Now user A will be able to see info relating to his resource via a url with a guid, but perhaps only for e.g. 3 days. Other users would also be able to access it, but it would be less likely to happen, both because it would be hard to guess the GUID, and because they would only have a 3 day window to do so.
If user A needs to access his resource again later, perhaps you could provide a way to extend the validity of the GUID, or alternatively just provide a new GUID that points to the same resource, but with a different validity date.
Obviously you'll need to thing through whether or not this is realistic / acceptable for your particular situation and security needs.
I have two entities Hotel, Merchant where each merchant can have many hotels. Right now I am having an api endpoint like this:
/api/v1/merchants/{id}/hotels/{id}
But I was thinking what is wrong with this semantics:
/api/v1/hotels/{id}
The later one is short too.
In my experience, the latter is preferable because it gives you more flexibility later. In six months somebody's going to say "Hey, I want to be able to look up all the hotels in Agraba". The first URL scheme makes that painful - you need to add a new endpoint. The second URL scheme supports that with a query parameter: GET /hotels?location=Agraba.
You may want to keep /merchants/{id}/hotels as a collection endpoint so you can POST/DELETE to add/remove hotels from a particular merchant.
In REST, each URL should uniquely identify a single resource.
So if the hotel's id is globally unique, then sure, there's no problem in using the shorter link. If however hotel id 1 means something different for merchant 1 than for merchant 2, then you ought to stick with the first URL (basically a unique composite key).
OK, lets assume we have two entities: Profile, consisting of id, name and ~10 irrelevant fields, and Post, consisting of text, title, and it's author (Profile). Also, there is resource /feed that returns feed containing posts from different profiles.
So I have two options:
Send full Profile entity in author
Send author's id (there is a way to request Profiles separately)
Which way is faster (in terms on using it on front end) and more convenient (RESTy, if you like).
Obviously just sending the id of Profile is faster because the response length is smaller.
The important question, however, do you need the full Profile object with each Post? If you want to, for example, print out the name of the author for each Post then sending the full object makes more sense. But if you want to just supply a link to the author with each Post (in the front end) then the id should be enough.
For other services that query yours for Posts just send the id and have them make a second call if they need. They can always cache the data on their end if needed.
Try to build your service so that each call/endpoint returns the bare minimum amount of data needed to make sense of the response. This might mean that a Post contains a lean Profile object where only the name is included but all the other, "irrelevant", fields are excluded. But when you query a Profile directly, you get the full object.
You can also have an optional query parameter where the caller can specify whether they want just the id or the full Profile, this is a strategy Atlassian JIRA uses to preserve bandwidth and improve speed.
Also check out the hal+json specification, it can give you good ideas about how to design a more usable and transparent REST service.
MOST IMPORTANT! Your endpoints should only return data that the outside world can actually use and make sense of. So that means if Profile has a field/fields which values are only used in your back-end (like, for example, the user's password) then you should never leak those out.
I'm writing an app which main purpose is to keep list of users
purchases.
I would like to ensure that even I as a developer (or anyone with full
access to the database) could not figure out how much money a
particular person has spent or what he has bought.
I initially came up with the following scheme:
--------------+------------+-----------
user_hash | item | price
--------------+------------+-----------
a45cd654fe810 | Strip club | 400.00
a45cd654fe810 | Ferrari | 1510800.00
54da2241211c2 | Beer | 5.00
54da2241211c2 | iPhone | 399.00
User logs in with username and password.
From the password calculate user_hash (possibly with salting etc.).
Use the hash to access users data with normal SQL-queries.
Given enough users, it should be almost impossible to tell how much
money a particular user has spent by just knowing his name.
Is this a sensible thing to do, or am I completely foolish?
I'm afraid that if your application can link a person to its data, any developer/admin can.
The only thing you can do is making it harder to do the link, to slow the developer/admin, but if you make it harder to link users to data, you will make it harder for your server too.
Idea based on #no idea :
You can have a classic user/password login to your application (hashed password, or whatever), and a special "pass" used to keep your data secure. This "pass" wouldn't be stored in your database.
When your client log in your application I would have to provide user/password/pass. The user/password is checked with the database, and the pass would be used to load/write data.
When you need to write data, you make a hash of your "username/pass" couple, and store it as a key linking your client to your data.
When you need to load data, you make a hash of your "username/pass" couple, and load every data matching this hash.
This way it's impossible to make a link between your data and your user.
In another hand, (as I said in a comment to #no) beware of collisions. Plus if your user write a bad "pass" you can't check it.
Update : For the last part, I had another idea, you can store in your database a hash of your "pass/password" couple, this way you can check if your "pass" is okay.
Create a users table with:
user_id: an identity column (auto-generated id)
username
password: make sure it's hashed!
Create a product table like in your example:
user_hash
item
price
The user_hash will be based off of user_id which never changes. Username and password are free to change as needed. When the user logs in, you compare username/password to get the user_id. You can send the user_hash back to the client for the duration of the session, or an encrypted/indirect version of the hash (could be a session ID, where the server stores the user_hash in the session).
Now you need a way to hash the user_id into user_hash and keep it protected.
If you do it client-side as #no suggested, the client needs to have user_id. Big security hole (especially if it's a web app), hash can be easily be tampered with and algorithm is freely available to the public.
You could have it as a function in the database. Bad idea, since the database has all the pieces to link the records.
For web sites or client/server apps you could have it on your server-side code. Much better, but then one developer has access to the hashing algorithm and data.
Have another developer write the hashing algorithm (which you don't have access to) and stick in on another server (which you also don't have access to) as a TCP/web service. Your server-side code would then pass the user ID and get a hash back. You wouldn't have the algorithm, but you can send all the user IDs through to get all their hashes back. Not a lot of benefits to #3, though the service could have logging and such to try to minimize the risk.
If it's simply a client-database app, you only have choices #1 and 2. I would strongly suggest adding another [business] layer that is server-side, separate from the database server.
Edit:
This overlaps some of the previous points. Have 3 servers:
Authentication server: Employee A has access. Maintains user table. Has web service (with encrypted communications) that takes user/password combination. Hashes password, looks up user_id in table, generates user_hash. This way you can't simply send all user_ids and get back the hashes. You have to have the password which isn't stored anywhere and is only available during authentication process.
Main database server: Employee B has access. Only stores user_hash. No userid, no passwords. You can link the data using the user_hash, but the actual user info is somewhere else.
Website server: Employee B has access. Gets login info, passes to authentication server, gets hash back, then disposes login info. Keeps hash in session for writing/querying to the database.
So Employee A has user_id, username, password and algorithm. Employee B has user_hash and data. Unless employee B modifies the website to store the raw user/password, he has no way of linking to the real users.
Using SQL profiling, Employee A would get user_id, username and password hash (since user_hash is generated later in code). Employee B would get user_hash and data.
Keep in mind that even without actually storing the person's identifying information anywhere, merely associating enough information all with the same key could allow you to figure out the identity of the person associated with certain information. For a simple example, you could call up the strip club and ask which customer drove a Ferrari.
For this reason, when you de-identify medical records (for use in research and such), you have to remove birthdays for people over 89 years old (because people that old are rare enough that a specific birthdate could point to a single person) and remove any geographic coding that specifies an area containing fewer than 20,000 people. (See http://privacy.med.miami.edu/glossary/xd_deidentified_health_info.htm)
AOL found out the hard way when they released search data that people can be identified just by knowing what searches are associated with an anonymous person. (See http://www.fi.muni.cz/kd/events/cikhaj-2007-jan/slides/kumpost.pdf)
The only way to ensure that the data can't be connected to the person it belongs to is to not record the identity information in the first place (make everything anonymous). Doing this, however, would most likely make your app pointless. You can make this more difficult to do, but you can't make it impossible.
Storing user data and identifying information in separate databases (and possibly on separate servers) and linking the two with an ID number is probably the closest thing that you can do. This way, you have isolated the two data sets as much as possible. You still must retain that ID number as a link between them; otherwise, you would be unable to retrieve a user's data.
In addition, I wouldn't recommend using a hashed password as a unique identifier. When a user changes their password, you would then have to go through and update all of your databases to replace the old hashed password IDs with the new ones. It is usually much easier to use a unique ID that is not based on any of the user's information (to help ensure that it will stay static).
This ends up being a social problem, not a technological problem. The best solutions will be a social solution. After hardening your systems to guard against unauthorized access (hackers, etc), you will probably get better mileage working on establishing trust with your users and implementing a system of policies and procedures regarding data security. Include specific penalties for employees who misuse customer information. Since a single breach of customer trust is enough to ruin your reputation and drive all of your users away, the temptation of misusing this data by those with "top-level" access is less than you might think (since the collapse of the company usually outweighs any gain).
The problem is that if someone already has full access to the database then it's just a matter of time before they link up the records to particular people. Somewhere in your database (or in the application itself) you will have to make the relation between the user and the items. If someone has full access, then they will have access to that mechanism.
There is absolutely no way of preventing this.
The reality is that by having full access we are in a position of trust. This means that the company managers have to trust that even though you can see the data, you will not act in any way on it. This is where little things like ethics come into play.
Now, that said, a lot of companies separate the development and production staff. The purpose is to remove Development from having direct contact with live (ie:real) data. This has a number of advantages with security and data reliability being at the top of the heap.
The only real drawback is that some developers believe they can't troubleshoot a problem without production access. However, this is simply not true.
Production staff then would be the only ones with access to the live servers. They will typically be vetted to a larger degree (criminal history and other background checks) that is commiserate with the type of data you have to protect.
The point of all this is that this is a personnel problem; and not one that can truly be solved with technical means.
UPDATE
Others here seem to be missing a very important and vital piece of the puzzle. Namely, that the data is being entered into the system for a reason. That reason is almost universally so that it can be shared. In the case of an expense report, that data is entered so that accounting can know who to pay back.
Which means that the system, at some level, will have to match users and items without the data entry person (ie: a salesperson) being logged in.
And because that data has to be tied together without all parties involved standing there to type in a security code to "release" the data, then a DBA will absolutely be able to review the query logs to figure out who is who. And very easily I might add regardless of how many hash marks you want to throw into it. Triple DES won't save you either.
At the end of the day all you've done is make development harder with absolutely zero security benefit. I can't emphasize this enough: the only way to hide data from a dba would be for either 1. that data to only be accessible by the very person who entered it or 2. for it to not exist in the first place.
Regarding option 1, if the only person who can ever access it is the person who entered it.. well, there is no point for it to be in a corporate database.
It seems like you're right on track with this, but you're just over thinking it (or I simply don't understand it)
Write a function that builds a new string based on the input (which will be their username or something else that cant change overtime)
Use the returned string as a salt when building the user hash (again I would use the userID or username as an input for the hash builder because they wont change like the users' password or email)
Associate all user actions with the user hash.
No one with only database access can determine what the hell the user hashes mean. Even an attempt at brute forcing it by trying different seed, salt combinations will end up useless because the salt is determined as a variant of the username.
I think you've answered you own question with your initial post.
Actually, there's a way you could possibly do what you're talking about...
You could have the user type his name and password into a form that runs a purely client-side script which generates a hash based on the name and pw. That hash is used as a unique id for the user, and is sent to the server. This way the server only knows the user by hash, not by name.
For this to work, though, the hash would have to be different from the normal password hash, and the user would be required to enter their name / password an additional time before the server would have any 'memory' of what that person bought.
The server could remember what the person bought for the duration of their session and then 'forget', because the database would contain no link between the user accounts and the sensitive info.
edit
In response to those who say hashing on the client is a security risk: It's not if you do it right. It should be assumed that a hash algorithm is known or knowable. To say otherwise amounts to "security through obscurity." Hashing doesn't involve any private keys, and dynamic hashes could be used to prevent tampering.
For example, you take a hash generator like this:
http://baagoe.com/en/RandomMusings/javascript/Mash.js
// From http://baagoe.com/en/RandomMusings/javascript/
// Johannes Baagoe <baagoe#baagoe.com>, 2010
function Mash() {
var n = 0xefc8249d;
var mash = function(data) {
data = data.toString();
for (var i = 0; i < data.length; i++) {
n += data.charCodeAt(i);
var h = 0.02519603282416938 * n;
n = h >>> 0;
h -= n;
h *= n;
n = h >>> 0;
h -= n;
n += h * 0x100000000; // 2^32
}
return (n >>> 0) * 2.3283064365386963e-10; // 2^-32
};
mash.version = 'Mash 0.9';
return mash;
}
See how n changes, each time you hash a string you get something different.
Hash the username+password using a normal hash algo. This will be the same as the key of the 'secret' table in the database, but will match nothing else in the database.
Append the hashed pass to the username and hash it with the above algorithm.
Base-16 encode var n and append it in the original hash with a delimiter character.
This will create a unique hash (will be different each time) which can be checked by the system against each column in the database. The system can be set up be allow a particular unique hash only once (say, once a year), preventing MITM attacks, and none of the user's information is passed across the wire. Unless I'm missing something, there is nothing insecure about this.
I'm making a site for a writers management company. They get tons of script submissions every day from prospective and often unsolicited writers. The new site will allow a prospective writer to submit a short logline / sample of his or her idea. This idea gets sent to an email account at the management group. If the management group likes what they see, they want to be able to approve that submission from within the email and have a unique link dispatched to the submitter to upload their full script. This link would either only work once, or only for a certain amount of time so that only the intended recipient could use it.
So, can anyone point me in the direction of some sort of (I'm assumine PHP + mySQL) CMS or framework that could accomplish this? I've searched a lot, but I can't seem to figure out the right way to phrase this query to a search engine.
I have moderate programming experience, but not much with PHP outside of some simple Wordpress hacks.
Thanks!
I will just give you general guidelines on a simple way to construct such a system.
I assume that the Writer is somehow Registered into the system, and his/her profile contains a valid mail address.
So, when he submits the sample, you would create an entry on the "Sample" table. Then you would mail a Manager with the sample and a link. This link would point to a script giving the database "id" of the sample as a parameter (this script should verify that the manager is logged on -- if not, show the login screen and after successful login redirect him back).
This script would then be aware of the Manager's intention to allow the Writer to submit his work. Now the fun begins.
There are many possibilities:
You can create an entry in an appropriate "SubmitAuthorizations" DB table containing the id of the Writer and the date this authorization was given (ie, the date when the row was added to your DB). Then you simply send a mail to the Writer with a link like "upload.php?id=42", where the id is the authorization id. This script would check if the logged user is the correct Writer, and if he is within the allowed timeframe (by comparing the stored "authorization date" and the current date).
The next is the one I prefer: without a special table just for handling something trivial (let's say you will never want to "edit" an authorization, nor "cancel" it, but it may still "expire"). You simply simply give the Writer a link with 2 parameters: the date the authorization was given and an authorization key, like: "upload.php?authDate=20091030&key=87a62d726ef7..."
Let me explain how it works.
The script would first verify if the Writer is logged on (if not, show the login page with a redirection after successful login).
So, now it's time to validate the request: that is, check if this is not a "forged" link. How to do this? It's just a "smart" way of construction this authorization key.
You can do something like:
key = hash(concat(userId, ";", authDate, ";", seed));
Well, here hash() is what we call a "one-way function", like MD5, SHA1, etc. Then concat() is simply a string concatenation function. Finally seed is something like a "master password", completely random and that will not change (for if you change it all the issued links would stop working) just to increase security -- let's say a hacker correctly guesses you are using MD5 (which is easy) and the he tries to hack your system by hashing some combinations of the username and the date.
Also, for a request to be valid, it must be in the correct time frame.
So, if both the key is valid, and the date is within the time frame, you are able to accept an upload.
Some points to note:
This is a very simple system, but might be exactly what you need.
You should avoid MD5 for the hashing function, take something like SHA1 instead.
For the link sent to the Writer, you could "obfuscate" the parameter names, ie, call them "k" for the "key" and "d" for the "authDate".
For the date, you could chose another format, more "cryptic", like the unix epoch.
Finally, you can encode the parameters with something like "base64" (or simply apply some character replacing function like rot13 for instance, but that take digits into account aswell) just in order to make them more difficult to guessing
Just for completeness, in the validation script you can also check if the Writer has already sent a file on the time frame, thus making it impossible to him to send many files within the time frame.
I have recently implemented something like this twice on the company I work for, for two completely different uses. Once you get the idea, it is extremelly simple to implement it -- maybe less than 10 lines of code for the whole key-generation and validation process.
On one of them, the agent equivalent to your Writer had no account into the system (actually it would be his first contact with the system) -- there was only his "profile" on the system, managed by someone else. In this case, you would have to include the "Writer"'s id on the parameters to the "Upload" script aswell.
I hope this helps, and that it was clear enough. If I find the time, I will blog about it with an working example on some language.