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Old 10-19-2005, 01:08 PM   #1
dimsh
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Registered: Aug 2005
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popen output not appear


Hi,

I am running my box on Linux FC4, and using Tomcat as my Web Server.
There is a user called utomcat who own the files/directories related to Tomcat and who own its process.

I am writing a binary file using C language and gcc compiler to allow web user (utomcat) to call (execute) a binary which can only be executed by root, those binaries are:
/home/vpopmail/bin/vadduser
/home/vpopmail/bin/vuserinfo

My problem is in the output that those binaries offer as a response to the acton they did.

I used "popen" in my program as following:
Code:
//### C Code ###
#include "stdio.h"
int main (int args, char *argv[]) {
	int result = 1;
	char *command = "/home/vpopmail/bin/vuserinfo user1@domain.com";
	FILE *output = popen(command , "r");

	while(result != EOF)	printf("%c" , result = fgetc(output));
	pclose(output);
};
//##############
The program compiled with no errors nor warnings and I named it "uinfo.exec", and chmod to 755.
I have set the "setuid" and "setgid" flags to the file "uinfo.exec" which is owned by root:root .

When I run the binary as root user , I get the output as supposed on the console terminal and every thing is fine

But
when su-ing to another user and running it (utomcat user for example) I see no output at all.

I need the output be visible to any user who call my binary.

Any solutions?

Thanks

Last edited by dimsh; 10-19-2005 at 01:11 PM.
 
Old 10-19-2005, 02:03 PM   #2
Hko
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Location: Groningen, The Netherlands
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I tried your code, with only the command changed to "ls /tmp" and it worked as expected. So I guess "vuserinfo" writes to stderr instead of stdin.

What happens when you try with "ls /tmp"?

I also wonder why you need this extra program. Doesn't java/tomcat has its own popen()-like functionality?
 
Old 10-20-2005, 06:45 AM   #3
dimsh
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Quote:
Originally posted by Hko
I tried your code, with only the command changed to "ls /tmp" and it worked as expected. So I guess "vuserinfo" writes to stderr instead of stdin.

What happens when you try with "ls /tmp"?
"ls /tmp" command works fine for both users.
What can I do if "vuserinfo" writes to stderr ? why i can get the user info using my binary if i am root and can not if other user ?

Quote:
I also wonder why you need this extra program. Doesn't java/tomcat has its own popen()-like functionality?
Also "vuserinfo" can only be executed by root , that is why i write this binary to be able to set its setuid flag (chmod 4755) and execute the "vuserinfo" command by any user (utomcat)

I do not know about java ability to popen because i am not java programmer , I need to allow java programmers to get user's mail information, via setuid ability, all they need to do is to call my binary from the java page , the script then will set UID to root , bring the user infor and they can read the binary output through java.

I think the problem is in stderr as you say , but how to work around it ?

Last edited by dimsh; 10-20-2005 at 07:00 AM.
 
Old 10-20-2005, 04:39 PM   #4
Hko
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Location: Groningen, The Netherlands
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Quote:
Originally posted by dimsh
I think the problem is in stderr as you say , but how to work around it ?
Instead of:
Code:
"/home/vpopmail/bin/vuserinfo user1@domain.com"
Try:
Code:
"/home/vpopmail/bin/vuserinfo user1@domain.com 2>&1"
If stderr is the problem, adding "2&>1" after the command should solve it.

Last edited by Hko; 10-20-2005 at 04:41 PM.
 
Old 10-22-2005, 02:56 AM   #5
dimsh
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Distribution: Debian, Ubuntu, Fedora
Posts: 74

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Thanks Hko for your help, redirecting using 2>&1 did not solve the problem.

I have posted this on experts-exchange also, the guys there says to use setuid() function and it works just fine.

if you like to see the solution there here is the link:
http://www.experts-exchange.com/Prog..._21600661.html

Thanks again for your efforts, Regards.
 
  


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