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Annotation of embedaddon/mtr/SECURITY, revision 1.1.1.4

1.1       misho       1: SECURITY ISSUES RELATED TO MTR
                      2: 
1.1.1.3   misho       3: mtr invokes a sub-process, mtr-packet, which requires extra privileges
                      4: to send custom packets, and there are security implications from
                      5: granting this.
                      6: 
                      7: There are several different ways to provide the privileges:
                      8: 
                      9: 1. Add limited privileges on systems that support this. (Preferred.)
                     10: 2. Run mtr as the root user.
                     11: 3. Make mtr-packet a setuid-root binary.
                     12: 
                     13: Details:
                     14: 
                     15: 1. Add limited privileges on systems that support this.
                     16: 
                     17: Some operating systems allow binaries to be run with only the subset
                     18: of security privileges that are actually needed.
                     19: 
                     20: Linux:
                     21: On Linux, privileges are known as capabilities. The only additional
                     22: capability that mtr-packet needs is cap_net_raw. To give this
                     23: capability to the mtr-packet binary, run the following command as root:
                     24: 
                     25: # setcap cap_net_raw+ep mtr-packet
                     26: 
                     27: 
                     28: 2. Run mtr as the root user.
                     29: 
1.1       misho      30: You can limit mtr usage to the root user by not putting a setuid bit
1.1.1.3   misho      31: on the mtr-packet binary. In that case, the security implications are
                     32: minimal.
1.1       misho      33: 
                     34: 
1.1.1.3   misho      35: 3. Make mtr-packet a setuid-root binary.
1.1       misho      36: 
1.1.1.3   misho      37: The mtr-packet binary can be made setuid-root, which is what "make install"
1.1.1.4 ! misho      38: does only if using setcap (above) fails.  Using setcap is tried first.
1.1       misho      39: 
1.1.1.3   misho      40: When mtr-packet is installed as suid-root, some concern over security is
                     41: justified.  mtr-packet does the following two things after it is launched:
1.1       misho      42: 
1.1.1.3   misho      43: *  mtr-packet open sockets for sending raw packets and for receiving
                     44:    ICMP packets.
                     45: *  mtr-packet drops root privileges by setting the effective uid to
                     46:    match uid or the user calling mtr.
                     47: *  If capabilities support is available, mtr-packet drops all privileged
                     48:    capabilities.
1.1       misho      49: 
1.1.1.3   misho      50: See main() in packet.c and init_net_state_privileged() in probe_unix.c
                     51: for the details of this process.
                     52: 
                     53: This should limit the possibilities of using mtr to breach system security.
                     54: The worst case scenario is as follows:
                     55: 
                     56: Due to some oversight in the mtr-packet code, a malicious user is able to
                     57: overrun one of mtr-packets's internal buffers with binary code that is
1.1       misho      58: eventually executed.  The malicious user is still not able to read
1.1.1.3   misho      59: from or write to any system files other than those normally accessible
                     60: by the user running mtr.  The only privileges gained are access to the raw
                     61: socket, which would allow the malicious user to listen to all ICMP packets
                     62: arriving at the system, and to send forged packets with arbitrary contents.
                     63: 
1.1       misho      64: 
                     65: If you have further questions or comments about security issues,
1.1.1.3   misho      66: please see the README file for details on how to submit them.