Issue #7188 resolved

[itsmeroy2012]

Tell us what this change does. If you're fixing a bug, please mention
the github issue number.
Issue number #7188

Verification

List the steps needed to make sure this thing works

• msfconsole

• use exploit/multi/handler

• set payload android/meterpreter/reverse_tcp

• set lhost 127.0.0.1

• set lport 4444

• exploit

• Verify: It will set lhost to 127.0.0.1 and will print a warning : "Please note that errors might be experienced with this choice of address for LHOST."

• set lhost 127.0.0.54

• set lport 4444

• exploit

• Verify: It will set lhost to 127.0.0.54 and will not print a warning.

[HansHauge]

How about a little syntactic sugar?

localhost_ips = []

(1..8).each do |num|
  localhost_ips << "127.0.0.#{num}"
end

if localhost_ips.include?(ip)
  print_error("Please note that errors might be experienced with this choice of address for LHOST.")
end

[firefart]

You can keep it simple:

if ip =~ /^127\.0\.0\.[1-8]$/

[busterb]

My original suggestion from the issue was to check if this is in the loopback subnet 127.0.0.0/8, not just the first 8 addresses. The proper check function would look something like this (I'm sure the rescue could be tightened up, but I prefer test functions to really only return booleans where possible):

require 'ipaddr'

def is_loopback_addr(addr)
  begin
    a = IPAddr.new(addr.to_s)
    return true if IPAddr.new('127.0.0.1/8') === a
    return true if IPAddr.new('::1') === a
  rescue
  end
  false
end

[IPAddr.new('127.0.0.1'), '127.0.0.1', '127.255.255.255', '::1', 'dog'].each do |addr|
  puts "#{addr} is loopback: #{is_loopback_addr(addr)}"
end

[busterb]

This returns the following experimental values:

127.0.0.1 is loopback: true
127.0.0.1 is loopback: true
127.255.255.255 is loopback: true
::1 is loopback: true
dog is loopback: false

[cbrnrd]

Isn't this already an open PR? (#8041)

[HansHauge]

Nice catch @thecarterb

[wvu]

Yes, we're attempting to deconflict.

[busterb]

Close, but this isn't the right fix. This PR is also made from a master branch, which usually is easier to fix with a new PR. See https://github.com/rapid7/metasploit-framework/blob/master/CONTRIBUTING.md#code-contributions about creating topic branches for PRs.

Closing for now. See comment above as well about how to test for subnet membership for an IP address. Thanks, do try again!

[itsmeroy2012]

Thanks.. I'll surely look into it...

[busterb]

Also, since we have an earlier PR #8041, suggest we continue discussion there. Thanks!

[itsmeroy2012]

How do I issue a PR in an open discussion?

[busterb]

Well, I'd say make suggestions at that PR, rather than hijacking with an alternate. Let's keep the discussion in one place. You could also pull the other contributor's fork as a remote, and send him a pull request on his topic branch.