Working with PowerShell & Multiple Azure Contexts

When working with multiple Azure subscriptions, the PowerShell Az.* modules allow for easy context switching. This means that you can run commands agains multiple subscriptions, or you can run commands against subscriptions without changing your default context. An Azure Context object contains information about the Account that was used to sign into Azure, the active (for that context) Azure Subscription, and an auth token cache is not actually empty, it just can't read from here for security reasons, though you can read it with the Get-AzAccessToken command. Here's what is in an Azure Context object: PS> Get-AzContext | fl * Name : TK-PRD (yyyyyyyy-yyyy-yyyy-yyyy-yyyyyyyyyyyy) - tim@timkennedy.net Account : tim@timkennedy.net Environment : AzureCloud Subscription : yyyyyyyy-yyyy-yyyy-yyyy-yyyyyyyyyyyy Tenant : zzzzzzzz-zzzz-zzzz-zzzz-zzzzzzzzzzzz TokenCache : VersionProfile : ExtendedProperties : {} If y
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A generic perl script to scan a CIDR subnet for listeners on a specific port.

Ever had a customer ask you where *some process* was running on *some port* in their network? I have. And usually this involves an environment that doesn't have NMAP installed, or any other common port scanning tools. Fortunately these days, almost every *nix OS comes with Perl, even Solaris.

Since I work for a managed services company, and we manage a multitude of different environments, each with it's own set of restrictions and requirements, I try to write the most portable code that I can, so that it has the best chance of actually working in any given environment.

This script uses a couple of standard Perl modules that are included as part of the default installation, and don't require any CPAN-Fu, and it takes a couple of options, such as a switch for verbosity, and IP address, with or wirhout a CIDR mask, and a TCP port. The CIDR mask defaults to /32, and the port defaults to 22. Here's an example of the output. 

tcsh-[101]$ ./scan-port.pl 208.64.63.39/30 80
================================================================================
Request to scan 208.64.63.39/30 on Port 80 (http)
Scanning 4 IP Addresses:
--------------------------------------------------------------------------------
208.64.63.36    : rats.entic.net                   : listening on 80 (http)
208.64.63.37    : corn.entic.net                   : listening on 80 (http)
208.64.63.38    : ice.hostsonfire.co.uk            : listening on 80 (http)
208.64.63.39    : jeep.sugarat.net                 : listening on 80 (http)
--------------------------------------------------------------------------------
Found 4 hosts listenening on port 80.
================================================================================

And here's the script itself. 
#!/usr/bin/env perl
#===============================================================================#
#
# scan_port.pl (c) tkennedy - 2011 November 19 Version 1.1
#
#-------------------------------------------------------------------------------#
#
# Description: Allows scanning a IP Subnet for TCP listeners on designated port.
# Syntax: $0 [-v] IPADDRESS/CIDR-NETMASK [Port]
#
#-------------------------------------------------------------------------------#
#
# Purpose:
# This script provides a means of scanning a subnet for TCP listeners, using 
# only commonly available Perl functions.  This should make the script portable
# to any system with Perl installed.  The script can be passed 3 arguments. 2 of
# the arguments are optional, and include a '-v', which increases the verbosity
# of script output, and 'P', which is a TCP port presented as an integer between
# 1 - 65535.  If a port is not supplied on the command line, the script assumes
# a default of 22, which is the common port for Secure Shell traffic (ssh). The
# mandatory argument is an IP Address, either with, or without, a CIDR netmask.
# If a CIDR netmask is not supplied on the command line, then we assume you only
# intend to scan a single IP (ie, a /32).
#
#-------------------------------------------------------------------------------#
#
# History:
#
# 20101123 1.1 tkennedy - removed Switch module for Sol8/Perl5.003 compatibility
#
# 20101119 1.0 tkennedy - initial revision
#
#===============================================================================#
#
# The modules we're using are standard perl modules, so this script should 
# work on any operating system with Perl installed.
#
use strict;
use IO::Socket;

my ($ip,$cidr,$port,$target);
my $VERBOSE = 0;

# We need a regex to match IP addresses.  This is only used to validate
# the command-line options to verify that one option is an IP.
#
my $ipr = qr/^((?:(?:2(?:5[0-5]|[0-4][0-9])\.)|(?:1[0-9][0-9]\.)|(?:(?:[1-9][0-9]?|[0-9])\.)){3}(?:(?:2(?:5[0-5]|[0-4][0-9]))|(?:1[0-9][0-9])|(?:[1-9][0-9]?|[0-9])).*$)/x;

# I wanted to keep things as free-form as possible, and so opted to just 
# parse the command line to extract our options.  This also gives us some
# leeway to ignore bad options.
#
# In our parser, we will match a '-h' for help info, a '-v' to extend 
# our output a bit, including printing lines for hosts that are scanned
# but not listening.  We'll also match a single number, which we'll 
# interpret as a TCP port number, and lastly, we'll match an IP address
# or CIDR-masked sub-net.
#
foreach my $arg (@ARGV) {
 for ($arg) {
  if ( $arg eq '-h' )  { &usage; }
  elsif ( $arg eq '-v' )  { $VERBOSE = 1; }
  elsif ( $arg =~ m/^\d+$/ )  { $port  = $arg; }
  elsif ( $arg =~ m/$ipr/ )  { $target = $arg; } 
 }  
}

# if the user forgot to put in a target subnet, goto usage();
#
&usage("Error: no target supplied!") if ("$target" == "");

# Here we'll set the default port to "22", which is SSH, and then we'll
# check to see if a port was submitted on the command line.  If it was,
# we'll override the default with the user submitted value.  We'll do 
# the same for CIDR mask, assuming that if a mask was not passed in, then
# the user wants a single host scanned and use /32 as the default.
#
($ip,$cidr) = split( /\//, $target);
$cidr  = ( $cidr ? $cidr : "32" );
$port  = ( $port ? $port : "22" );

# die if we get an invalid CIDR mask!
#
&usage("Error: Invalid CIDR mask [$cidr]") if ( $cidr > 32 );

# Get the TCP Service name for our port...
#
my $svcname = getservbyport($port,"tcp");

# Convert the CIDR mask into a hex netmask, and calculate the number
# of addresses in the supplied target.
#
# my $mask = 0xffffffff >> $cidr;  # this fails on sol8/perl-5.003
my $size = 1 << ( 32 - $cidr );
my $mask = $size - 1;

#===============================================================================#
# script body below here.
#===============================================================================#

&hr2();
print "Request to scan ${ip}/${cidr} on Port $port ($svcname)","\n";
print "Scanning $size IP Addresses:","\n";

# calculate the lowest IP in the range, by AND-ing the supplied IP 
# address and the netmask, and convert to dotted quad notation.
#
my $lowest      = unpack('N', pack('C4', split '\.', $ip)) & ~$mask;
my $count = 0;
my $scanned = 0;

# based on the $lowest IP in the subnet, let's enumerate all of the
# IP addresses in the supplied $target subnet.
#
my @ips  = map {$lowest++} 0 .. $mask;

# a simple loop to scan each of the ips we mapped.
#
foreach my $addr(@ips) {
 scan_ip($addr);
}

&hr();
print "Found $count hosts listenening on port $port.","\n";
&hr2();

#===============================================================================#
# only subroutines are below here.
#===============================================================================#

sub scan_ip {
 #
 # from the foreach loop above, we've passed in our address.
 # this address is an integer, so we'll need to convert it to
 # a dotted-quad format IP address. then try hostname lookup,
 # and then try opening a socket.
 #
 my $addr = shift;
 my $ipaddr = join( '.', unpack( "C4", pack( "N", $addr ) ) );

 my $hostname = gethostbyaddr(inet_aton("$ipaddr"), AF_INET);
 chomp $hostname;

 if ("$hostname" eq "") {
  $hostname = ( $VERBOSE ? "NXDOMAIN" : " " );
 }

 my $sock = IO::Socket::INET->new(
  PeerAddr => "$ipaddr",
  PeerPort => "$port",
  Timeout => "1",
  Proto => "tcp",
  ) or nosocket("$ipaddr","$hostname") && next;

 if($scanned < 1) { &hr(); }
 
 my $txt = "listening on $port ($svcname)";
 printf('%-15s : %-32s : %-15s', $ipaddr, $hostname, "$txt\n") if($sock);

 close($sock) if($sock);
 $count++;
 $scanned++;
}

sub nosocket { 
 # we reach this sub on unsuccessful socket attempts.
 #
 if($scanned < 1) { &hr(); }
 my $ipaddr = shift;
 my $hostname = shift;

 if($VERBOSE > 0) {
  my $txt = "closed on $port ($svcname)";
  printf('%-15s : %-32s : %-15s', $ipaddr, $hostname, "$txt\n");
 }

 $scanned++;
 next;
}

sub usage { 
 if (@_) {
  print "\n@_\n";
 }
 # this sub() just prints the standard usage information.
 #
 print < [port]
 -h  this message
 -v  verbose output
  format IP/CIDR: 1.1.1.1/32, /32 is default CIDR mask
 [port]  a tcp port between 1 and 65535, 22 is default 

Example: $0 -v 192.168.0.1/24 80
 will scan the 255 addresses in the 192.168.0.0 subnet on port 80

EOT
exit(1);
}

sub hr { 
 # print a row of ---s
 print "-" x 80, "\n";
}

sub hr2 { 
 # print a row of ===s
 print "=" x 80, "\n";
}

# EOF
So far this has worked successfully on Solaris 10 Sparc & x64, CentOS 5.5 x64, Solaris 8 Sparc, and Solaris 9 Sparc, and Mac OS X 10.6.

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