How mailx -r works? Post: 302832565

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Top Forums Shell Programming and Scripting How mailx -r works? Post 302832565 by bakunin on Monday 15th of July 2013 07:42:12 AM

07-15-2013

Registered User

First, you have to distinguish between mail as a (network) protocol and the means (clients, servers, MTAs, ...) to use this protocol.

The mail protocol - SMTP - allows to send messages with any name as sender. As "mailx" is a very basic client it does nothing to authenticate a user at all, so: yes, in the way you presented it it would be possible to send mail using any arbitrary mail address as sender. Yes, this would work for other email addresses too, provided that your mail server (more precisely: mail transfer agent, MTA) is set up this way. In fact this is the way professional spammers work: by setting up a MTA of their own and configuring it in a sufficiently crooked way.

This is the reason why you should not trust incoming mail (solely) based on the mail address of the sender: because this could be forged.

Now, in a common setup the MTA would not allow to send mail with an arbitrary sender address and/or has rules to rewrite address information when handling mail messages. Your MTA (probably "sendmail") is perhaps set up only rudimentary to allow sending diagnostic information via mail to the admins. This is not uncommon: if a filesystem becomes nearly full or a similar condition takes place the server might generate a mail message to the admin(s). For this the MTA is installed and set up with minimal effort. This does not automatically mean it could send mail anywhere outside the companies network. If so: this is a security deficit and should be taken care of.

I hope this helps.

bakunin

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reporter-mailx

REPORTER-MAILX(1)						 LIBREPORT MANUAL						 REPORTER-MAILX(1)

NAME

       reporter-mailx - Sends contents of a problem directory via email.

SYNOPSIS

       reporter-mailx [-v] -d DIR [-c CONFFILE]

DESCRIPTION

       The tool reads a problem directory, composes an email message from the directory contents, and uses mailx to send the message to specified
       recipient.

       Properties of email messages can be specified in a configuration file, and via environment variables.

   Configuration file
       Configuration file contains entries in a format "Option = Value".

       The options are:

       Subject
	   The subject of the email message.

       EmailFrom
	   The sender of the email message.

       EmailTo
	   The recipient of the email message.

       SendBinaryData
	   Use yes/true/on/1 to attach all binary files from the problem directory to the email. This can cause the emails to be very large.

   Integration with ABRT events
       reporter-mailx can be used as a reporter, to allow users report problems via email when they decide to do it. This usage is pre-configured
       in /etc/libreport/events.d/mailx_event.conf:

	   EVENT=report_Mailx	   reporter-mailx

       It can also be used to notify administrator automatically when a problem happens. When this is desired, modify the event configuration file
       to run the tool on the post-create event:

	   EVENT=post-create	   reporter-mailx

OPTIONS

       -d DIR
	   Path to problem directory.

       -c CONFFILE
	   Path to configuration file. When used in ABRT event system, the file contains site-wide configuration. Users can change the values via
	   environment variables.

ENVIRONMENT VARIABLES

       Environment variables take precedence over values provided in the configuration file.

       Mailx_Subject
	   Subject of the email message.

       Mailx_EmailFrom
	   Sender of the email message.

       Mailx_EmailTo
	   Recipient of the email message. If nor the environment variable nor the corresponding option is defined, the message is send to
	   "root@localhost".

       Mailx_SendBinaryData
	   Use yes/true/on/1 to attach all binary files from the problem directory to the email.

AUTHORS

       o   ABRT team

LIBREPORT 2.1.11						    06/18/2014							 REPORTER-MAILX(1)

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