Am I right in saying that if I have a plain text password (say to connect to an SMTP mail server) in one of my c# controllers, there is no way for an attacker to view this (or the rest of the server side code for that matter) unless server security is broken?
I am on shared hosting so I can't do anything with IIS to encrypt web config (as far as I am aware). If this is such bad practice, does anyone have any suggestions as to how to best tackle this issue?
If this is such bad practice, does anyone have any suggestions as to how to best tackle this issue?
It is a bad practice. While you can't prevent an attacker who can read files on the server (or the backups) from figuring it out (quickly, if they're good), you can force them to spend more time and effort in reading your code/disassembled application and your config files both.
Are you allowed to set the SMTP password yourself? Store in your config file a very high number of iterations (millions; it's just startup delay!), a truly random** salt of 8 bytes, and a long, random "password" (binary is better). In your code, when the application is started, read those values, add a hardcoded string of 8 truly random bytes to the salt (a "pepper"), and use the RFC2898DeriveBytes class to generate the actual SMTP password (which you're likely to have to encode with Base64). Don't ask for more than 20 bytes of RFC2898DeriveByutes output; that's using SHA-1 as the native hash. You will obviously need to do this prior to changing the SMTP password :).
Regardless of your ability to change the SMTP, you can always encrypt the password, using the above RFC2898DeriveBytes to generate a 128 bit key for use with AES-128 in, say, the AesCryptoServiceProvider class if you're on .NET 3.5 or up, which is one of the few FIPS 140-2 compliant encryption classes in .NET.
If you want a way to handle this that prevents simply reading files from finding out the password, you'll need to look at something like an HSM (hardware security module) or other secure key storage provider outside of your appliance. Be prepared to open your wallet!
** In .NET, use the RNGCryptoServiceProvider class to generate random bytes for crypto use.
Related
Are there any examples of using encryption to encrypt the disk-cache used by OkHttp's HttpResponseCache? Naively, I don't think this is a very hard thing to do, but I'd appreciate any advice or experience to avoid security-pitfalls.
Without too many specifics, here's what I'm trying to achieve: a server that accept user's api-keys (typically 40-character random string) for established service X, and makes many API calls on the users behalf. The server won't persist user's api-keys, but a likely use case is that users will periodically call the server, supplying the api-key each time. Established service X uses reasonable rate-limiting, but supports conditional (ETag, If-Modified-Since) requests, so server-side caching by my server makes sense. The information is private though, and the server will be hosted on Heroku or the like, so I'd like to encrypt the files cached by HttpResponseCache so that if the machine is compromised, they don't yield any information.
My plan would be to create a wrapper around HttpResponseCache that accepts a secret key - which would actually be a hash of half of the api-key string. This would be used to AES-encrypt the cached contents and keys used by HttpResponseCache. Does that sound reasonable?
Very difficult to do with the existing cache code. It's a journaled on-disk datastructure that is not designed to support privacy, and privacy is not a feature you can add on top.
One option is to mount an encrypted disk image and put the cache in there. Similar to Mac OS X's FileVault for example. If you can figure out how to do that, you're golden.
Your other option is to implement your own cache, using the existing cache as a guide. Fair warning: the OkResponseCache is subject to change in the next release!
I'm working on an application that will connect to various remote servers using a Web Service to retrieve some status information about those ( Windows ) machines.
It works well within a single domain where we can just use Windows Authentication and ensure that the user calling the services has the correct credentials. However if we are working across domains that is not going to work- we're going to need to store a set of credentials for a user with the requisite rights on the application side.
Is there a standard way of storing credentials for these purposes, some kind of central password store in Windows or a handy built in library to provide this kind of functionality? If not, what is the best approach to keeping the passwords on the central machine safe and make sure the remote machine credentials are available when those services need to be called?
I would expect this application to mostly be installed on one of the Windows Server operating systems- 2003 or 2008 - if that makes any difference to what is available.
I suggest you have a look at "Windows Identity Foundation". It may be overkill for you, or the prerequisite may not match, but it's anyway worth reading as its very instructive in terms of claims based architecture with Microsoft technology.
The two principal white papers for developers are:
Overview of the Claims Based Architecture
Microsoft Windows Identity Foundation (WIF) Whitepaper for Developers
I assume that this is not a question of Silverlight or Flash application, those would have some special things...
I have used authentication system by Federation of Finnish Financial Services (used by all major Finnish banks). It goes like this:
Both your client and server have a secret key (or 2 keys).
You can store it e.g. to a custom place in Windows registry (which is easy with .NET and you can control the registry access). Don't hard-code the key to code, because otherwise someone could use reflection to get it. Also a custom xml-file in a folder could be dangerous, if the platform is not secure enough.
Then, we have the request, let's say WebService REST Url and there is some id:
http://myserver/MyItems/15
Now, we need to use a timestamp and an one-way hash-algorithm.
There are lot of available ones like md5, SHA1, SHA512, ...
(also built-in to the Microsoft .NET library).
We calculate a hash-value over the id and timestamp (and maybe some other parameters).
To simplify a bit, those algorithms work like modulo-algorithm: Let's say that my id is 11, secret key is 3, then modulo 11 % 3 = 2, now the hash would be 2, and if you know the id (11) and hash (2), you can't get the secret key.
The real request would be like this:
http://myserver/MyItems/15?timestamp=20110304171900&hash=89A234BA645FD56
The service will check the hash. If some hackers would have enough time, they could guess valid requests.
But the service will also check if the timestamp is ok, like between 5min past and 5min future.
So you can't adjust the request because it would modify the hash.
And of course one more thing is to use the SSL protocol. Otherwise your requests could be read from a random proxy server.
I would also recommend the Windows Identity Foundation, but this is another option.
we are saving user data on a server and we want to do save this data encrypted with TrueCrypt.
If a user registers, we generate an asymmetric key for him that is encrypted with his password. This asymmetric user-specific key will encrypt all the keys that are used for services, including the above mentioned data encryption.
If we now want to read the users files, add new and modify existing ones from within our Java Application running on a Application Server, should we mount the TrueCrypt container?
We think that it might be a security leak as an attacker could easily look in the mounted container, but we also have no other idea - we are kind a stuck!
I am sure someone can help us here.
Thanks,
Heinrich
#edit By the way, we are using Spring for your Java App.
I don't think it is a good idea to use TrueCrypt for this usecase. When using TrueCrypt you have no other choice than mounting it on each request to encrypted files. You should think about using plain Java encryption and do encryption and decryption yourself. There are libraries like Google Keyczar that may help you implementing this.
I was thinking of making a small tool. It is not important what the tool will do. The important thing, is that the tool will need to store some sensitive information on the user's HDD. EDIT: The information that will be stored is USER'S information - I'm not trying to protect my own content, that I distribute with the app.
I understand that I need to encrypt this information. But then, where do I safely store the encryption password? It's some sort of an infinite recursion...
So, is there a way, to encrypt information on windows, and have windows securely manage the passwords? When I say windows I mean Windows XP SP2 or later.
I should also note, that users on the same system must not have access to other users information (even when they are both running my application).
I'm looking for both - .NET 2.0 (C#) and native (C/C++) solutions to this problem.
is there a way, to encrypt information on windows, and have windows securely manage the passwords?
CryptProtectData: http://msdn.microsoft.com/en-us/library/windows/desktop/aa380261(v=vs.85).aspx
Using from .NET: http://msdn.microsoft.com/en-us/library/aa302402.aspx
Historically, Protected Storage (available in XP, read-only in vista+): http://msdn.microsoft.com/en-us/library/bb432403%28VS.85%29.aspx
You should consider using DPAPI for this purpose. It will encrypt your data with a special (internal) symmetric key which is on per-user basis. You don't even need to ask for passwords in this case, because different users on the system will have different keys assigned to them.
The downside of it might be that you can't recover the data if the user is deleted/Windows reinstalled (I believe that this is the case, not quite sure though). In that case encrypt the data with a "self-generated" key derived from the password and store the password in registry/file encrypted using DPAPI.
You can use the native encryption facility. Set the encrypt attribute on your folder or file (from the property page, click on the "advanced" button). Then you can set the users that can access the file (by default this only includes the file creator). The big advantage of this solution is that it is totally transparent from the application and the users points of view.
To do it programmatically: using the Win32 API, call EncryptFile() on the directory where you want to store your sensitive per-user data. From now on all newly created files within this dir will be encrypted and only readable by their creator (that would be the current user of your app). Alternatively you can use the FILE_ATTRIBUTE_ENCRYPTED flag on individual files at creation time. You can check encryption info from the explorer on the file's property page, and see that app-created files are correctly encrypted and restricted to their respective users. There is no password to store or use, everything is transparent.
If you want to hide data from all users then you can create a special app-specific user and impersonate it from your app. This, along with ACLs, is the blessed technique on Windows for system services.
You might want to look at Isolated Storage, which is a way of storing settings and other data on a per-application data automatically.
See an example and MSDN.
This is an alternative to storing normal settings in the registry, a better one in a lot of cases... I'm not sure how the data is stored to file however so you'd need to check, you wouldn't want it to be accessible, even encrypted, to other users. From memory only the app. that created the storage can open it - but that needs checking.
Edit:
From memory when I last used this, a good approach is to write a "Setting" class which handles all the settings etc. in your app. This class then has the equivalent of Serialize and DeSerialize methods which allow it to write all its data to an IsolatedStorage file, or load them back again.
The extra advantage of implementing it in this way is you can use attributes to mark up bits of the source and can then use a Property Grid to quickly give you user-edit control of settings (the Property Grid manipulates class properties at runtime using reflection).
I recommend you look at the Enterprise Library Cryptography Application Block. Check this blog post. Windows has a built in Data Protection API for encrypting data, but the Crypto Application Block makes it more straightforward.
Um, what you're trying to achieve is exactly what DRM tried to achieve. Encrypt something then give the user the keys (however obfuscated) and the crypto. They did it with DVDs. They did it with Blu-Ray. They did it with iTunes.
What you are proposing to do will never be secure. Your average lay person will probably not figure it out, but any sufficiently motivated attacker will work it out and discover the keys, the algorithm and decrypt the data.
If all you're doing is encrypting user data then ask the user for their password. If you're trying to protect your internal data from the user running the application you're S.O.L.
Erm hash the password? You don't need to store the real deal anywhere on the machine just a hashed password (possibly salted too). Then when the user enters their password you perform the same operation on that and compare it to the hashed one you've stored on disk.
Is it possible to store passwords on the local system (Windows XP) that can only be accessed by the application itself?
My instinctive answer would be "no". Even if some kind of hashing or encyption is used I would think that as long as the source code is available then the determined seeker could always use this to retrieve the password.
I'm working on a personal open source hobby project in which I would like to give users the option of storing passwords on disk so that they don't need to type them every time they use the software. One example of a password that could be stored would be the one used to authenticate on their network's proxy server.
There are a few related questions here on Stack Overflow and the most appropriate solution sounds like using an operating system service like DPAPI.
Is the basic premise correct that as long as the password is retrievable by the software without any user input, and the source code is open source, that the password will always be retrievable by a (suitably technically and willfully inclined) passer-by?
You could read about the Pidgin developers' take on it here:Plain Text Passwords.
Using the DPAPI in UserData mode will only allow your account on your machine to access the encrypted data.
It generates a master key based off of your login credentials and uses that for the encryption.
If the password is retrievable by the software without any user input, then the password will always be retrievable by a (suitably technically and willfully inclined) passer-by. Open or closed source only affects how much effort is involved.
Absolutely, you can write a program to store passwords securely.
Using AES, you could have your program generate an AES Key, and have that key stored in an operating system protected area. In WinXP, this is the registry, encrypted with DPAPI. Thus the only way to access the key is to have physical access to the machine.
You need to ensure that when you generate your AES key that you do so in a cryptographically secure manner. Just using RAND won't work, nor will generating a random character string.
Open Source has very little to do with security (in my opinion). Given the level of sophistication in tools for reverse engineering source code, even if you had a closed source solution, people determined to snoop at your code could do so.
Your effort is better spent ensuring that you follow best practice guidelines while using the chosen encryption scheme. I would argue that having your code openly looked at by a larger community would actually make your code more secure; vulnerabilities and threats would likely be identified sooner with a larger audience looking through your code.