We're providing a web form whereby users fill in their personal information; some of it is sensitive information (SSN, Birthday, etc). Upon user submission, the data is prefilled into a PDF which is then made available via a link.
We are creating the PDF in a folder that has write access on the website.
How can we safely create and add PDFs in this folder, with whatever naming scheme (use a GUID?), such that another user cannot guess/spoof the PDF file location, type this in the URL and access another person's PDF?
Maybe the PDF folder has rights only specific to the user, but that may be a different question on how that is accomplished. (The number of users is unknown, as this will be open to public).
Any thoughts on this? In a nut shell, we need to allow the user to view a PDF of the data they just entered while preventing more-savvy users to figure out the location of PDF files, allowing access to other files.
Thanks!
trying to obfuscate the path to a file isn't really making it secure. I would find a way to email or another way to fetch it for the user instead of allowing access to an open directory.
Make the web app fetch the file for the user instead of relying on web server open folder permissions.
just keep in mind obfuscation isn't really security.
If it's really just for the moment, create a completely random file (20384058532045850.pdf) in a temporary directory, serve that to the user immediately and remove it after a certain period of time.
Whether your web app has write rights on that directory or not (I assume you are talking about chmod user rights) is not important, it can't be breached trough the web server and I don't see a problem in revealing the directory path per se - you have to reveal something in giving the user a URL to download. If your PDF names are random enough, there is practically no risk of somebody being able to guess the name of another PDF file in the same directory.
As the PDF contains sensitive data: Don't forget to turn off caching to prevent a local copy of the PDF being saved on the client's browser cache.
I don't know for sure whether turning off caching through the appropriate headers is enough to prevent local caching in all browsers. You might have to look into that.
For the purpose of pdf's, would it not be better (I know I will get flamed for this) to store the actual pdf into the database as a BLOB, which would be on the back-end of the website in question?
There will be no reference to the URL anywhere nor will there be a specific path highlighted in any links on that form.
Hope this helps,
Best regards,
Tom.
The simplest way is to proxy the file through your application (fpassthru() in php for example), this allows you to use what ever access control/identification system you already use for the dynamic content.
If you don't have any means of identifying your users and restricting access, and assuming your platform has a secure session mechanism, you can protect the file by storing the filename in the user's session and then returning that file (and only that file) to the user when requested. This should mean that an attacker would have to spoof a session to access the file so this should be as secure as your session mechanism is.
Related
I would like to save user file in my project, such as user's profile image(jpg) or user's grade information(xml).
Now,I know
how to implement upload process in express
how to use static file path in express (at "public" dir) (for "CSS", "JS", "page image")
But, If I upload user's file in public directory, client can access file in public directory just with url like "my_website/public/.../....xml". I think it is not good for security because everyone can access others' profile image, grade information, and so on.
So, my question is
Is it okay to save user's sensitive information in public(static) directory?
If not, is there any way to save file safely except database?
In real websites, where they save user's sensitive information file? Is it in same directory with server files like main.js? or completely another server?
Is it okay to save user's sensitive information in public(static) directory?
No, it is not OK. That allows anyone access to private information.
If not, is there any way to save file safely except database?
Yes, there are other ways. For example, you could store a user's information in a directory just for that user and only allow users access to their data in their own directory. This obviously required authentication with some sort of username and a credential/password. You won't be using express.static() to access private information. Instead, you will create a route for each type of resource, verify who the logged in user is and provide access to only the resources that belong to that logged in user.
In real websites, where they save user's sensitive information file? Is it in same directory with server files like main.js? or completely another server?
There are lots of ways to implement user-specific storage, but it is highly unlikely that it is stored in the same directory as other server resources (like code files). User-specific data would be stored somewhere else.
I'm working on a windows app which is reading a "authorized" domains list from a txt file with a web request from "domain.com/sub/txtfile"
I don't want people to see the content of the file when entering it directly in the browser. Is it possible to achieve this with some .htaccess hacks or something else?
As your app is a client-side native Windows application, it's not possible to store any secret in the app itself that could be used for authentication. As the user has everything the Windows app may have, it impossible to authenticate the client as discussed many times here.
It also doesn't make much sense. Imagine it was somehow possible and file contents were only visible to your app. What would be the purpose? What if an attacker changed the hosts file on Windows to download the file from a rogue server? What if he used an intermediate proxy to inspect, change or replace contents? The latter is also possible with https, because the user has full control of the client, and can trust whatever certificate he wants.
You could authenticate the user though. An attacker can still see and modify downloaded file contents, but at least not anybody could download the file, only your authenticated users. But this means having a user database where the file is downloaded from, and implementing proper authentication. And it still doesn't solve the other problems.
In short, you can't protect a client-side application from a user that controls the whole client.
Need to test file upload feature for security. Purpose is to avoid/stop any type of malicious files from being uploaded.
Thanks !!
There are multiple vulnerabilities that usually come up around file uploads/downloads.
Malware in uploaded files
Any uploaded file should be virus-checked. As #CandiedOrange responded, you can use the EICAR test for that purpose.
Path injection
The filename for an uploaded file is te same type of user input as any other field in the request, an attacker can freely choose the filename. As a tester, you can send something like "../filename" to try and save it to unintended locations or to overwrite other files.
Filetypes
If the filetype restriction is only on the client, that's obviously useless for security. But even if the file extension is restricted on the server side, say only .pdf is allowed, you can still try to upload something.pdf.php or something.pdf.exe or similar to get around the filter. It's best if the application uses some real content discovery to find out if the uploaded file is actually an allowed filetype.
Content sniffing
Some browsers have this awesome (not) feature that when a file is downloaded, the browser looks into its content and displays it according to the content, regardless of the content type header received from the server. This means even if uploads are restricted to say .pdf, an attacker might upload an html file with javascript, in a file named "something.pdf" and when somebody else downloads that file, the browser may run the javascript, thus making the application vulnerable to XSS. To prevent this, the application should send the X-Content-Type-Options: nosniff response header.
Uploaded file size
If an attacker can upload too many or too big files, he may be able to achieve denial of service by filling up the space on the server.
Download without restriction (direct object reference)
An application might save uploaded files to a location directly accessible to the webserver. In such a case, download links would look similar to /uploads/file.pdf. This is only suitable for public files, access control cannot be enforced that way, anybody that has the link can download the file.
Lack of access control
If files are not available to all logged on users, the application must perform authorization to decide whether the user that's logged in can actually download the file he is requesting. Too many times this authorization step is missing or flawed, resulting in the application being able to serve the wrong files to users cleverly modifying requests.
So the bottom line is, file upload/download vulnerabilities are much more than just virus checking uploaded files.
If you're security is signature based consider uploading an EICAR test file. It should trigger your protection and if it doesn't, and is somehow executed, all it will do is print "EICAR-STANDARD-ANTIVIRUS-TEST-FILE!" and stop.
Well you can activate malware protection on your network firewall. Snort is good option for protecting websites.
You can also add input filters to your application code so it checks if the uploaded file has malware
I know that the title can be better, but I don't know how to define my problem.
my problem is the next, I'm not sure if it's possible to do, but i suppose that it is.
I have some .pdf online and i want to protect them for third people.
My idea, instead of assign a password and show an input like this:
I want to send the password (or token) in the path. something like
file.pdf?tpw=aaaa-bbb-dddd
Is it possible? I'm using C# to create the pdf.
edit: the case
I have an application which create a folder with some pdf, those pdf can be uploaded or created here with a form. (this part works)
All this documents are stored in internet (global access) then I want to prevent that 3rd people or search engines (I'm reading about this, it doesn't looks like a big problem)
Then here is the problem, i want to some users can access to some pdf, for example
user K can access to pdf 33
user j can access to pdf 54
but not k to 54, etc.
my idea is send to the user (they should access throw the link) something like "https://domain.com/pdf/33.pdf?password=222222" and without this password cant access.
if is not possible to do it, i can create an "intermediate page" to put the links there.
and send the url like "http://domain.com/pdf/view.chtml?id=33&password=222222"
edit: and prevent the access if they type https://domain.com/pdf/33.pdf
EDIT 2: SOLUTION (at least per now)
store into the database for each file
- filename - user(in md5) - token (in sha1)
send to the user a link like www.domain.com/api/showpdf.chtml?user=XXXXX&token=KKKKKKKKKKKKKKK
When the user clicks on that just check in the database by the user and the token if any file exist, if is this case show the file.
To solve the problem with the direct access, we are going to put the files out of "localhost" folders
Thanks for all.
I don't think it is a good idea to GET your passwords, they will be visible, the password should only be sent once, start a user session in the server, which will then create a temporary ticket for the user, and this ticket should be sent on each request via POST.
Anyway, you'll need to use a database and store users, passwords, files, and per-file permissions for each user, you could use a file, but it's never a good idea to store the passwords in plain text. I guess you already have a database running, you'll only need to add a files and a per-file permissions table to it.
Also, you should never keep the real password in the database either, but just a checksum of it (SHA-1, or similar)
Goal: to download archives from a web-site (ordinary hosting). An user must know nothing about downloading, a connection, a file storage on a web-site.
I use idHTTP+SSL to download archives. But user can access a web-site -> I can set Basic Authentication, but an user can see a user name/password e.g. in HTTP Analyzer.
A program downloads file with settings. Settings are in a form of a plain text. This text can be seen in HTTP Analyzer too.
I can to encrypt this text but what about archives? I need to secure everything at one time.
Therefore I do not want that user could see an web address of archives and setting file. It can be pasted in a web browser -> please download everything...
How to prevent all these?
Thanks!!!!!!!!
I assume "ordinary hosting" means the usual PHP/Perl hosted site where you can't really run arbitrary software or make significant site-wise configuration changes. I'd take the following steps:
Configure the folder where your archives and "text file" reside to only accept HTTPS connection, then make sure you only connect using HTTPS: "HTTP Analyzer" (or any analyzer for that matter) will no longer be able to see your traffic.
Give your archive meaningless names (GUID's?), so there's no way for the user to just enter a file name into the browser and download that. You'll need to "map" the actual file names to the GUID's using your TXT file.
For extra points replace the "TXT" file with a script that authenticates your application before providing the actual data. Even a simple salted hash of the current date and time would be enough to deter most users.
Of course, I expect this question to be followed up with other questions, some on ServerFault, some here on SO:
How to block plain HTTP access to a folder using [name your server software]
How do I authenticate my application so an ordinary browser can't download my TXT file.