Is it possible to execute a method as a different user in Linux (or SELinux specifically)? The programs that I have run in individual sandboxes, each with a different user and process id. I have a situation where I have to execute a branch of code as a different user and with different process id to prevent the access of the memory and disk space of the code that's spawning it.
If not possible, can you throw some light on how much of the kernel code has to be changed to achieve it? (I understand its subjective. Alternatively, if you can suggest what and how to go about it, that will be much helpful).
Protecting some resources from other codes executing on the same machine is precisely what lead to the process and UID invention.
If you are searching for a mechanism that looks like a simple function call, I would say it's impossible because it requires the memory to be shared between the caller and the callee. However, using fork/exec (or wrappers like system()) will give you some isolation as long as you deal with parameters/results using system objects like program parameters or pipes.
Although, the fact that *nix user is meant to protect processes from one-another, requires that an explicit relationship be built between two users to have one user act on behalf of the other.
Actually, you may want to:
define a sudoers policy which gives the right to your first user to run a command (or a particular command) as the second one.
use popen() (or system()) in your first program to call the less privileged code.
if any, pass the parameters and parse the result from stdout
As an extra, you may use the same binary for both executions, this way, all the code can be at the same location.
I created a time recording program in vb.net with a sql-server as backend. User can send there time entries into the database (i used typed datasets functionality) and send different queries to get overviews over there working time.
My plan was to put that exe in a folder in our network and let the user make a link on their desktops. Every user writes into the same table but can only see his own entries so there is no possibility that two user manipulate the same dataset.
During my research i found a warning that "write contentions between the different users" can be occur. Is that so in my case?
Has anyone experience with "many user using the same exe" and where that is using datasets and could give me an advice whether it is working or what i should do instead?
SQL Server will handle all of your multi-user DB access concerns.
Multiple users accessing the same exe from a network location can work but it's kind of a hack. Let's say you wanted to update that exe with a few bug fixes. You would have to ensure that all users close the application before you could release the update. To answer you question though, the application will be isolated to each user running it. You won't have any contention issues when it comes to CRUD operations on the database due to the network deployment.
You might consider something other than a copy/paste style publishing of your application. Visual Studio has a few simple tools you can use to publish your application to a central location using ClickOnce deployment.
http://msdn.microsoft.com/en-us/library/31kztyey(v=vs.110).aspx
My solution was to add a simple shutdown-timer in the form, which alerts users to saving their data before the program close att 4 AM.
If i need to upgrade, i just replace the .exe on the network.
Ugly and dirty, yes... but worked like a charm for the past 2 years.
good luck!
I am writing a program in Objective-C (Xcode 3.2, on Snow Leopard) that is capable of either selectively blocking certain sites for a duration or only allow certain sites (and thus block all others) for a duration. The reasoning behind this program is rather simple. I tend to get distracted when I have full internet access, but I do need internet access during my working hours to get to a number of work-related websites. Clearly, this is not a permanent block, but only helps me to focus whenever I find myself wandering a bit too much.
At the moment, I am using a Unix script that is called via AppleScript to obtain Administrator permissions. It then activates a number of ipfw rules and clears those after a specific duration to restore full internet access. Simple and effective, but since I am running as a standard user, it gets cumbersome to enter my administrator password each and every time I want to go "offline". Furthermore, this is a great opportunity to learn to work with XCode and Objective-C. At the moment, everything works as expected, minus the actual blocking. I can add a number of sites in a list, specify whether or not I want to block or allow these websites and I can "start" the blocking by specifying a time until which I want to stay "offline".
However, I find it hard to obtain clear information on how I can run a privileged Unix command from Objective-C. Ideally, I would like to be able to store information with respect to the Administrator account into the Keychain to use these later on, so that I can simply move into "offline" mode with the convenience of clicking a button. Even more ideally, there might be some class in Objective-C with which I can block access to some/all websites for this particular user without needing to rely on privileged Unix commands. A third possibility is in starting this program with root permissions and the reducing the permissions until I need them, but since this is a GUI application that is nested in the menu bar of OS X, the results are rather awkward and getting it to run each and every time with root permission is no easy task.
Anyone who can offer me some pointers or advice? Please, no security-warnings, I am fully aware that what I want to do is a potential security threat.
If you want to do something with admin privileges, and you don't want to have to authenticate each time, it sounds like you need to look at setuid.
Make little command-line executable to do the rule changing, and then set that tool's owner to root. Then, set the setuid bit. Now, you can run it as a user and it will run as root.
Look here for more info:
http://en.wikipedia.org/wiki/Setuid
You have to create a separate process that runs with higher privileges. Have a look at the BetterAuthorizationSample on how to run such helper applications using launchd.
I'm working on creating a self updating application and one issue I'm running into on Vista and Windows 7 is needing to have admin privileges in order to update the client. I've run into issues with clients that have their users running under restricted permissions and they would have to have IT log onto every machine that needed to update the client since the users were not able to.
A possible work around I'm considering is to have the launcher application installed into Program Files as normal, and having the real application that it updates installed in the users documents somewhere, so that they could update and run new versions without IT becoming involved.
I'm wondering what potential gotchas I'm missing here or what I should be aware of before heading down this path. I'm aware that click-once does something very similar, and I'd be using it, except I need the ability to do silent updates, without any user interaction.
This is how it is supposed to be. The last thing most IT departments want is a user randomly updating a piece of software. This could have all sorts of unintentional side effects such as incompatibility with the older version's files, new and possibly insecure functionality, etc. This is why IT departments disable Windows Update and do their updates manually in a controlled fashion.
If the users want an updated version of the software they should be requesting it from their IT department. Those computers and infrastructure don't belong to them, they're simply borrowing time on them from the company they work for so they can do their job.
Is there an issue with having only one installation of your program? Is it particularly large, for example?
Do you require admin privileges to run your program?
If not, odds are you don't need the Program Files folder.
I suggest you forgo installing to Program Files entirely and just install your program into the user's folder system at <userfolder>\AppData\ProgramName.
If you happen to be using .NET, look into the ClickOnce deployment mechanism. It's got a great self-updating feature that'd probably make your life a lot easier.
Edit: Just saw your last sentence. ClickOnce can force the user to update.
A couple of things:
If you decide to move your app to some place in documents, make sure that your application writes data transparently to where your program is installed, e.g. if there are hard coded paths anywhere in the code that are pointing to bad places. Perhaps this is not an issue for you, but might be something to keep in mind.
We solved this in pretty much the same way when we decided to implement a "live update" feature. But instead we installed a service which is running with administrator rights. This service in turn can run installers once the program needs to be updated. With this type of solution you don't even have to move your applicaton out of program files.
Cheers !
Edit:
Another neat thing with having a service running as administrator. Is that you could create a named pipe communication with it and have it do things for you, like you wouldn't be able to do as a normal user.
A loader stub is a good way to go. The only gotcha is when you have to update the loader; the same initial problem applies (though that should be pretty infrequent).
One problem that I can think of off the top of my head is that you're stepping outside the entire idea of keeping things more "secure." Since your executable exists in a location that should be completely accessible to a non-administrator, it's possible that something else could slam your exe thus subverting security.
You can probably leverage AppLocker. It may only be for Win7 though I'm not running Vista any more. ;)
As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, visit the help center for guidance.
Closed 10 years ago.
Lots of people have things that their systems do for them or for their teams. Source control post-commit hooks are a standard example: have an automated build system that checks out the latest source, compiles, tests, and packages it is a back-office hack that most of us probably use.
What other cool things have you done?
We had one developer in our team who wasn't familiar with the concept of a subversion conflict. He deduced that if he simply deleted all that weird stuff in his code and clicked resolve that everything was ok (i.e. knocking out all the other changes in the file....)
Regardless to say, after the 5th time this occurred, and the 5th time that I had to explain why that defect that I just closed was reoccuring, I wrote a script.
It would diff for the changes to a file to see whether the consecutive checkin deleted all the previous changes and that they were done by the nameless developer.
It would then send an email to the boss with a description of what happened, and how much work was lost during the checkin.
There was no 7th occurrence.
We have a traffic-light that shows whether our daily build succeeds, has failed tests or simply doesn't build.
Also, we have a light bar that lights up for a few seconds whenever we receive an upload from a customer.
We aren't staffed 24x7 but we have critical processes that run throughout the night. We created an in-house alerts system to notify us of serious system issues, failed mission-critical processes, etc. It uses text-to-speech to create a descriptive message and then connects to our automated dialer to call the appropriate people with the message.
Working at a web design company I configured our dev server so we could see a working copy of a project in real time by a sub domain name. So if your name was joe and you were working on project jetfuel you would go to joe.jetfuel.test-example.com and you could see your changes instantly without committing.
This was a simple hack that used sub domain names as a partial directory structure. Our htdocs path looked like this htdocs/tag/project. We had a script (a php app that you would access by setup.test-example.com) that would create a new tag name for you and checkout whatever version you wanted and call the deploy script for that project. If it succeeded it would forward you to the new sub domain. You could then work on this new copy by a samba share.
This worked really well for us since we always deployed to the same linux build and our projects had simple database requirements.
Our original reason for doing this was because our developers worked on all kinds of different platforms. Besides fixing this platform problem this was awesome for viewing changes and testing. We had all kinds of tags ranging from peoples names, trunk versions, test tags, all the way to prototypes like jquery-menu-hack.jetfuel.test-example.com
Now that I look back I wonder how much easier it would have been to run virtual machines.
We had a dev working on a classic ASP site that didn't believe in source control. The code went from his machine straight to the production box. This lead to issues with lost changes or the inability to revert back to a stable version. Since CruiseControl.Net has the ability to monitor a directory, I added a project that actually checked in files whenever they were copied to production. Completely backward from CC.Net's original intent, but we didn't lose any more code.
Put in a pre-commit hook that checks the bug comment refers to an open bug, assigned to the user doing the checkin. (SCMBug can do this).
Then to make life REALLY interesting, spell check the comments!!
The commit comment, and the one in the code. (spell is my buddy)
Run the code through a code formatter set to compayn standard; and diff it to the original: if it's not in company offical format: reject the commit.
Do a coverage test with the unit test build.
Email all mistakes/errors caused to the development team.
I left OUT the name of the developer. They know they did it.
Not exactly hacks, but a couple of must-haves for IT dev work:
If you're using subversion, you've got to use CommitMonitor. (http://tools.tortoisesvn.net/CommitMonitor) It lets you monitor svn repositories for new commits & then review the new commits. Great if you're wanting to stay on top of what your team is doing. Particularly if you have a couple of juniors that need to be watched. ;)
Rsnapshot (http://www.rsnapshot.org/) is also invaluable - we have complete backup snapshots of our entire filesystem every four hours going back 2 years, and every day beyond that. It's like a data cube for your filesystem! The peace of mind this gives is pure bliss. :)
Hardly a hack, but back in the day, on our speedy VAX 11/730, our overnight process would print the file "BLAMMO.TXT" on the printer if something went amiss. Every morning, the first stop was the printer when coming in.
Back in the dotCom days about 9 years ago, I had to hack a failover system between two different locations. We had a funky setup with a powerbuilder front end website, and powerbuilder managment tool. Data was stored in MSSQL 7.0. The webservers used IPX to communicate to the SQL Servers (don't ask). Anyway, I was responsbile for coming up with a failover plan.
I ended up hacking together some linux boxes, and had them run our external DNS. One at each location. We had a remote site w/ webserver, and sql server I got SQL transaction replication working over a 128k ISDN IPX connection (of all things). Then built a monitoring tool at our production site to send packets out to various upstream network handoffs. If we experienced more than 20% outage the primary site, the monitoring tool ran a perl script on the Debian box to change DNS and point to our 2ndary. Our secondary had a heartbeat w/ our primary DNS, and monitoring station. It would duplicate records unless it lost both connections then it would roll over to pointing DNS to backup location.
The primary site would shut down the SQL server at the primary location to break replication. Automated site to site failover using 128k ISDN IPX connection :)
Back at my previous job, we had to audit many tables for data changes (inserts, updates and deletes). Our support crew had to be able to search through this data to find changes that users made.
The temporary solution that had become semi-permanent was to store each non-select query. However this was a large system, that the table would grow by about 1.5GB a day.
The solution I came up with was to create a script that for all tables in an external list, created the appropriate triggers that audit each table, row, column, before and after, when and by whom and store it in our new audit table. This table grew by about 10% the size of the older version and stored much more usable data. It enabled us to create a UI to search and view every change made to our data, without requiring any knowledge of SQL for our support team or business users.
This is at a lesser level, but I am fairly proud of a make file I wrote for compiling code for my research. It only needs to be given your source and header file names that can take care of the rest all by itself (though it does make the one assumption that you will not be compiling any header files into objects, only source files get compiled). The other downsides are the fact that it relies on the GNU make program's second expansion feature, so I don't know if it works on other make programs. Additionally the compiler used needs to support something similar to gcc's -MM feature. Here is hoping that no one laughs at it.
-include prereqs.mk
HEADERS=$(SRC_DIR)/gs_lib.h $(SRC_DIR)/gs_structs.h
SOURCES=$(SRC_DIR)/main.cpp $(SRC_DIR)/gs_lib.cpp
OBJECTS=$(patsubst $(SRC_DIR)/%.cpp,$(OBJ_DIR)/%.o,$(SOURCES))
release: FLAGS=$(GEN_FLAGS)$(OPT_FLAGS)
release: $(OBJECTS) prereqs.mk
$(CXX) $(FLAGS) $(LINKER_FLAGS) $(OUTPUT_FLAG) $(EXECUTABLE) $(OBJECTS)
prereqs.mk: $(SOURCES) $(HEADERS)
$(CXX) $(DIR_FLAGS) $(MAKE_FLAG) $(SOURCES) | sed 's,\([abcdefghijklmnopqrstuvwxyz_]*\).o:,\1= \\\n,' > $#
.SECONDEXPANSION:
$(OBJECTS): $$($$(patsubst $(OBJ_DIR)/%.o,%,$$#))
$(CXX) $(FLAGS) $(NO_LINK_FLAG) $(OUTPUT_FLAG) $# $(patsubst $(OBJ_DIR)/%.o,$(SRC_DIR)/%.cpp,$#)
Obviously I dropped the definition of a number of variables, but I think it gets the idea across.
Since my coding tools and style are compatible with the requirements of this script I like to use it. All I need to do to add (a) new piece(s) of source code is add its name(s) to the appropriate variable and the rest is taken care of.
We have Twitter accounts for many projects which tweet things like commit messages, notices from builds, failed unit tests, deployments, bug tracking activity - any kind of event associated with the project. Running a client like Twitter Gwibber (which displays a pop-up for each new status) is a great way to stay in touch with the activity on the projects you are interested. Using Twitter is good as you can take advantage of all the 3rd party apps - such as the iPhone clients.
Add commit-hook check for VRML/3d-model files with absolute path to textures/images. f:/maya/my-textures/newproject/xxxx.png just doesn't belong on the server.
Back in the 1993, when source control systems were really expensive and unwieldy, the company I worked about had an in-house source control built as 4DOS scripts. It wasn't as sofisticated as most current source control systems, for example it didn't have branching or integrates, but it did the basic job of supporting revisions history, checkout/checkin and rudimentary conflict resolution.