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How to send a mail using Perl and sendmail in Linux

sendmail in LinuxThere will be some situations where you will not be allowed:
  • to send mail outside of your company/organization
  • to open any mail client like Gmail, yahoo or Hotmail using browser

But you wish to send mail to your outside friend. Either you will use some proxy settings or will request administrator to allow sending or receiving any mail from outside. What if we can do it using an in-built command or through script?

Yes it is possible and it’s much more easy if you are using Linux rather than Windows (I know even now most of us are using Windows to read this article 😉 ).

This code will work only at Linux variants. If you want to use sendmail in Windows and Linux also with command line option instead of writing a Perl script, you need to download sendEmail readymade script written in Perl by Brandon Zehm  .

  • For Linux users, just untar it and run as you run other Perl script, provided your Perl interpreter is at /usr/bin/perl else change the path at script accordingly
  • For Windows users, extract the code and run it at command line. Make sure, you have installed Perl interpreter.

Let’s see the explanation using codes:
[perl]
#!/usr/bin/perl
#################################################################################
#    Author: Sanjeev Jaiswal
#    Date: July, 2012
#    Description: This script will use inbuilt command “sendmail” with -t option mainly.
#                 You can send an email to anyone from any valid email id, even if it’s not you.
#                 You can use it to prank your friends too or to do some serious stuffs.
#################################################################################
use strict;
use warnings;
 
# You can put as many email ids as you wish in to, cc, bcc
# But, be sure to use commas under one string. All mail ids are fake here, used just for demo 😛
# except  admin@aliencoders.org 😉
my %config = (mail_from =>’ranjan2012@gmail.com’,
              mail_to => ‘jaszi@gmail.com, sanjeejas@gmail.com’,
              mail_cc => ‘jasse@gmail.com, jassi@hotmale.com’,
              mail_bcc => ‘nazibal700@gmail.com, jasze@gmall.com’,
              mail_subject => “Just testing Sendmail”
             );
 
#Call method to send preformatted email
mail_target();
 
sub mail_target{
   #Use \n\n to make sure that it will render as HTML format
   my $message = “From: $config{mail_from}\nTo: $config{mail_to}\nCc: $config{mail_cc}\nBcc: $config{mail_bcc}\nSubject: $config{mail_subject}\nContent-Type: text/html;\n\n”;
   $message.= “<strong>Hi Dear,</strong><br>If someone knows your email id, he/she can use it without your permission if he/she is using sendmail under Linux :D<br> Only issue is it says via which server. Through this you can find out from which server and location someone has used your email id.\n”;
 
   my $MAIL_CMD = “/usr/sbin/sendmail -t -i”;
   if(!open(SENDMAIL, “| $MAIL_CMD”)){
      print “Unable to open an input pipe to $MAIL_CMD:”;
      exit(1);
   }
   print SENDMAIL $message.”\n”;
   close(SENDMAIL);
}
[/perl]

If it gives error like Can’t exec “/usr/lib/sendmail” then :
  • Verify if you are using right sendmail path by using “which sendmail” command at linux box. You can see the sendmail path.
  • If it says no command found then, type whereis sendmail and you will surely get the lists of sendmail. Use any of these.
You can hide the server and host information also. But you may see “This message may not have been sent by: “ if it’s Gmail or any good email clients 😀
 
Any alternatives?
Yes, try any of these listed modules in Perl:
How we can trace out that this mail is from the original sender or someone used his/her id using such scripts?
If you click at show original option under Gmail, you can see, who sent you the mail and from where you got the mail.
Tips:
  • You can use anyone’s email id at from section but use yours only. I used my friends id to prank them (but it’s not ethical though)
  • It even didn’t check mail existence so you can  write from email address as bill-gates@msft.com
  • In case you forgot to use proper email format like bill-gates instead of bill-gates@msft.com then it would embed it’s server name as domain name like bill-gates@your-server-name.com
  • You can even attach files
  • You can send mails to many under to, cc and bcc. (Usually to should have only one email id)
Note: Use it to send mail from your mail id only. Using other’s identity for wrong doing is an offensive crime. Do those things at your own risk. Our work was to make you aware about working sendmail only. (Never say that I didn’t warn you before doing anything unethical)
 
How we can hide host name so that no one can get the original trace even using header information.
With the help of masquerading, your outgoing email would appear  from user@aliencoders.org instead of realunixuser@server01.aliencoders.org. This will also hide your internal user name or host name from rest of the world!
So this feature rewrites the hostname in the address of the outgoing mail. This can also be used when you have centralized mail server i.e. mail hub.

Masquerading Sendmail configuration (sendmail.mc not sendmail.cf)
Open your sendmail config file which will be located at  /etc/mail/sendmail.mc:

[vim]
# vi /etc/mail/sendmail.mc
[/vim]

Append/add/modify these lines as follows: (usually these lines will be commented, so just uncomment it)
[vim]
MASQUERADE_AS(aliencoders.org)dnl
FEATURE(masquerade_envelope)dnl
FEATURE(masquerade_entire_domain)dnl
MASQUERADE_DOMAIN(aliencoders.org)dnl
[/vim]
 

Save and close the file. Replace domain name aliencoders.org with your actual domain name. Update and restart sendmail server (use as root):

Before restarting the server, let’s sendmail.inc make sendmail configuration file ready using m4 command. The m4 utility is a macro processor intended as a front end for C, assembler, and other languages. Type man m4 in Linux box for more details. So, don’t edit sendmail.cf manually.

[vim]
# m4 /etc/mail/sendmail.mc > /etc/mail/sendmail.cf
# /etc/init.d/sendmail restart
[/vim]
 

Done! Now you can hide your real user name, server details and can enjoy this beautiful feature of Linux. (Do pranks or unethical things at your own risk 😉 )

Disclaimer: This article is for educational purpose only. We are not responsible if you get sued or fired from your company while using this script or such knowledge. Use it at your own risk!

Minimal Introduction to Perl

 Welcome to Perlistan world! I have been using Perl (Perl 5.10 specifically) from last 1 year and I am really fond of this programming language. There are hell lots of features exist for Perl but I have written only few which I felt is important and interesting for beginners.

Introduction
Perl (Practical Extraction & Report Language) is the Swiss Army knife for  scripting languages(rather call it programming language): powerful and adaptable. It was first developed by Larry Wall, a linguist working as a systems administrator for NASA in the late 1980s, as a way to make report processing easier.

Since then, it has moved into a large number of roles: automating system administration, acting as glue between different computer systems; and, of course, being one of the most popular languages for CGI programming on the Web.

Why did Perl become so popular when the Web came along?
There may be at least two most important  reasons:

First, most of what is being done on the Web happens with text, and is best done with a language that's designed for text processing. More importantly, Perl was appreciably better than the alternatives at the time when people needed something to use. C is complex and can produce security problems (especially with untrusted data), Tcl can be awkward and Python didn't really have a foothold.

Second: It also didn't hurt that Perl is a friendly language. It plays well with your personal programming style. The Perl slogan is “There's more than one way to do it,'' The growth of Internet also complemented Perl. The initial attempt at providing dynamic content was through CGI (even now CGI is used extensively), and Perl's remarkable text handling features made it a quick fit. CGI programming is now synonymous with Perl programming.

CPAN – Comprehensive Perl Archive Network, was set up to share Perl code. Perl supports modules and chances are that for 99% of the programming requirements, there is already a tested module in CPAN (for the remaining 1%, write modules and contribute to CPAN!). Using modules really mask the complexities of adhering to pre-defined standards and frees you to concentrate on your tasks – no point in re-inventing the wheel. Now, you have modules which handles graphics, CGI etc… You can also embed Perl code in your C/C++ programs. A very popular embedded Perl architecture is mod_perl for Apache web server.

Lets dive little bit deeper

Data manipulation
Perl can handle strings, dates, binary data, database connectivity, streams, sockets and many more. This ability to manipulate multiple data types help immensely in data conversion (and by the way, it is much faster than PL/SQL!). Perl also has provision for lists (or arrays) and for hashes (associative arrays). Perl also supports references, which are similar to the pointers in C. Lists, hashes and references together make it possible to define and manipulate powerful custom-defined data-types.

Portability Most of the Perl code will run without any change in Unix or Windows or Macintosh. Typical changes you might have to make include specifying file paths and use of low-level OS specific functions.

CGI CGI.pm. Period. Almost all CGI programs written today are using the CGI.pm module from CPAN. Even before this was written, people used to use Perl extensively for CGI programming. CGI.pm made the process streamlined and easy, even for beginners. The graphics library GD is used extensively in producing dynamic web charts. Ever since Kernighan and Ritchie came out with C programming language, people have started learning almost any programming language with the obligatory "Hello World" program. Let us do the same!

Hello World!

Here is the basic perl program that we'll use to get started.

[perl] #! /usr/bin/perl
# prints Hello world.
use strict;
use warnings;
print 'Hello world.';                # Print a message [/perl]

#!  is called sh-bang (she bang 😉 ). Always let it be your first line of code in your program.  Write the location of executable perl here. Always try to write use strict and use warnings in your program. It will minimize error and you will be following standard coding rules !

Comments Perl treats any thing from a hash # to the end of line as a comment. Block comments are not possible. So, if you want to have a block of comments, you must ensure that each line starts with #.

Statements Everything other than comments are Perl statements, which must end with a semicolon, like the last line above. Unlike C, you need not put a wrapping character \ for long statements. A Perl statement always ends with a semicolon.

Running Perl Write a small  program using a text editor, and save it. The first line of the program is a typical shell construct, which will make the shell start the interpreter and feed the remaining lines of the file as an input to the interpreter. After you've entered and saved the program make sure the file is executable by using the command

[perl]
chmod u+x perlfile
[/perl]

at the UNIX prompt, where perlfile  is the filename of the program (of course with .pl or .pm extension mostly). Now, to run the program, just type any of the following at the prompt.

[perl]
perl perlfile
[/perl]

If something goes wrong then you may get error messages, or you may get nothing. You can always run the program with warnings using the command

[perl]
perl -w progname
[/perl]

at the prompt. This will display warnings and other (hopefully) helpful messages before it tries to execute the program. To run the program with a debugger use the command

[perl]
perl -d progname
[/perl]

When the file is executed Perl first compiles it and then executes that compiled version. Unlike many other interpreted languages, Perl scripts are compiled first, helping you to catch most of errors before program actually starts executing. In this context, the -w switch is very helpful. It will warn you about unused variables, suspicious statements etc.

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