SUID question

r_jr · 08-10-2011, 11:47 AM

I have a python script that needs to run as a normal user, but do to the fact that it is accessing digital IO ports I need root access. I tried setting the SUID

Code:

chmod 4755 file

and then tried running it as a normal user, but I still get a need to root error. Is there anyway around this problem?

corp769 · 08-10-2011, 12:07 PM

Hello,

Depending on what you are doing, you could always change the individual permission for the block device that you are using; In this case, a digital IO port. What exactly are you working on anyway? Just curious so I can help out...

Cheers,

Josh

r_jr · 08-10-2011, 12:45 PM

Quote:

Originally Posted by corp769

Hello,

Depending on what you are doing, you could always change the individual permission for the block device that you are using; In this case, a digital IO port. What exactly are you working on anyway? Just curious so I can help out...

Cheers,

Josh

I am using the python portio library to toggle a shutdown line to an external device. The code below works, but like I said I need to be root to execute it and I eventually need to do it as a normal user as part of an application. Either that or I need to add a new group to the sudoer list. I did that for a startup script that I need to run but I read that I could set the SUID to allow a normal user to run a script, but I have been unsuccessful so far.

Code:

import sys, time, os
import portio

# check for root privileges
if os.getuid():
  print 'You need to be root! Exiting.'
  sys.exit()

# acquire permission for I/O on lp0
#status = portio.ioperm(0x480, 1, 1)
status = portio.iopl(3)
if status:
  print 'iopl:',os.strerror(status)
  sys.exit()

#init the chipset
RetVal = 0

RetVal = portio.inb(0x4B0)
RetVal=RetVal|0x02
portio.outb(RetVal,0x4B0) 

RetVal = portio.inb(0x481)
RetVal=RetVal|0xF0
portio.outb(RetVal,0x481) 

RetVal = portio.inb(0x480)
RetVal=RetVal|0xC0
portio.outb(RetVal,0x480) 

RetVal = portio.inb(0x4B4)
RetVal=RetVal|0x01
portio.outb(RetVal,0x4B4) 

RetVal = portio.inb(0x485)
RetVal=RetVal&0x0F
portio.outb(RetVal,0x485) 

RetVal = portio.inb(0x485)
RetVal=RetVal|0x02
portio.outb(RetVal,0x485) 

RetVal = portio.inb(0x484)
RetVal=RetVal|0xC0
portio.outb(RetVal,0x484) 


#reset the output pins to zero
RetVal = portio.inb(0x48d)
RetVal=RetVal&0x0F
portio.outb(RetVal,0x48d) 
   

for i in range(1,10):
  print ("LED ON!, \n",i)
  #Set all DO0 to 1
  portio.outb(0x10,0x48d) #DO0 is bit 4
	     		  #DO1 is bit 5
		  	  #DO2 is bit 6
		  	  #DO3 is bit 7
  time.sleep(1)
  print ("LED OFF!, \n",i)
  #Set all output to 0
  portio.outb(0x00,0x48d)
  time.sleep(1)

print ("Hello World!, \n")

#### END