debops.smstools

This is an Ansible role which configures smstools package and sets up a TCP -> SMS and mail -> SMS gateway. This role has been tested on Debian and should work on Debian-based systems.

Several other roles from DebOps project are used to configure various parts of the SMS gateway (debops.postfix role is used to create mail -> SMS gateway, debops.etc_services, debops.ferm and debops.tcpwrappers are used to configure TCP service which can be used by other hosts to send SMS messages over the network).

Installation

This role requires at least Ansible v1.7.0. To install it, run:

ansible-galaxy install debops.smstools

Role dependencies

  • debops.ferm
  • debops.etc_services
  • debops.postfix
  • debops.tcpwrappers
  • debops.rsyslog

Role variables

List of default variables available in the inventory:

---

# ---- TCP -> SMS gateway ----

# List of IP addresses or CIDR network ranges which are allowed to access TCP
# service
smstools_service_allow: []


# ---- mail -> SMS gateway ----

# Settings for subdomains and domains which are used to send messages to SMS
# gateway

# Subdomain for SMS transport
smstools_mail_transport_subdomain: 'sms'

# Subdomain for mail aliases which are resolved to mobile numbers
smstools_mail_alias_subdomain: 'gsm'

# Domains that combine above subdomains with main host domain
smstools_mail_transport_domain: '{{ smstools_mail_transport_subdomain }}.{{ ansible_domain }}'
smstools_mail_alias_domain: '{{ smstools_mail_transport_subdomain }}.{{ ansible_domain }}'

# List of default mail senders that are allowed to send mail messages to mobile
# recipients
# Options:
#    - name: 'mail@example.com'            # required
#      state: 'permit/deny'                # optional
smstools_default_senders:
  - name: 'root@{{ ansible_domain }}'
  - name: '{{ ansible_ssh_user }}@{{ ansible_domain }}'

# Additional list of mail senders
smstools_senders: []

# Hash table which specifies mail alias to mobile number mapping. Aliases will
# be generated in a domain specified with smstools_mail_alias_* variables
smstools_mail_recipients: {}
  #'recipient1': [ '+00123123123' ]
  #'recipient2': [ '+00123123123', '+00321321321' ]

# Hash table which specifies aliases for groups of recipients from
# smstools_mail_recipients table. Aliases will be created in a domain specified
# with smstools_mail_alias_* variables
smstools_mail_aliases: {}
  #'alias': [ 'recipient1', 'recipient2' ]

# List of regexps which will be used to find and remove strings in SMS messages
# before they are sent
smstools_mail_msgdel_list: []
  #- 'linux'
  #- '^Ansible'

# Log sent SMS messages for accounting purposes, use monthly log rotation, logs
# should be kept for 2 years
smstools_sms_log: '/var/log/sms.log'
smstools_sms_log_rotation: 'monthly'
smstools_sms_log_rotation_interval: '{{ (12 * 2) }}'


# ---- SMS gateway testing ----

# List of mobile numbers to send a test message to on host reboot
# Example: [ '+00123123123' ]
smstools_test_recipients: []

# Test message to send on host reboot
smstools_test_message: 'This is a test of the SMS gateway on {{ ansible_fqdn }} sent at $(date)'


# ---- smstools options ----

# Time between queue checks, in seconds
smstools_sleep: 1

# Generate modem stats once a day
smstools_stats_interval: '{{ (60 * 60 * 24)|round|int }}'

# Hash with options configured in /etc/smsd.conf
smstools_global_options:
  delaytime: '{{ smstools_sleep }}'
  delaytime_mainprocess: '{{ smstools_sleep }}'
  receive_before_send: no
  autosplit: 3
  loglevel: 5

# List of modems known to smsd, by default it's configured to use one modem on
# serial interface
smstools_devices:
  - name: 'GSM1'
    device: '/dev/ttyS0'
    options:
      baudrate: 115200
      incoming: yes

Detailed usage guide

Sending a text message from command line

You can send SMS messages from the host connected to the GSM modem, by running command:

sudo -u smsd sendsms +00123123123 "Text message"

Your user needs to be in sms system group or needs to be able to run /usr/local/bin/sendsms script (for example have admin access).

Sending a text message using TCP service

SMS messages can be sent remotely using TCP service (by default configured on port 9898). Access to the service is protected using tcpwrappers (via xinetd service) and iptables firewall.

To send a text message using TCP service, connect to port 9898 (by default) and send string similar to (notice lack of quotation marks):

TEXT +00123123123 Text message

TCP service should respond with text ending with 250 SMS accepted (if formatting was correct), or 500 Command not recognized (if formatting was incorrect).

Example telnet session which sends SMS message from a localhost:

$ telnet localhost sms
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
TEXT +00123123123 Text message
--
Text: Text message
To: +00123123123
250 SMS accepted
Connection closed by foreign host.

Sending a text message over mail

debops.smstools role configures two subdomains in local Postfix instance:

  • sms. subdomain is responsible for mail to SMS transport, Postfix takes mail messages sent to that subdomain and passes them to sms service (configured in /etc/postfix/master.cf which is a script that parses the mail message and sends body of that message to specified recipient using sendsms script;
  • gsm. subdomain is used for aliases which correspond to addresses in the sms. subdomain or groups of aliases in the same subdomain;

To send a SMS message via mail, send a mail to an address <+00123123123@sms> (on localhost) or <+00123123123@sms.example.com> (from elsewhere). You can also create mail aliases using debops.smstools role variables or your configured alias table in format <name@gsm> (from localhost) or <name@gsm.example.com> (from elsewhere) which should correspond to mail addresses outlined previously. Subject of the mail message will be ignored, and body of the message will be sent using SMS gateway.

Warning, this role can generate mail backscatter!

At the moment, SMTP server is configured by debops.smstools role to accept mail messages to subdomains specified above and relay them to sms transport which checks if a sender of mail message can send SMS messages through mail. If it can't, SMTP server receives a reject message and generates a bounce message to an original sender of the mail, which can be forged, generating mail backscatter.

Because of that risk, at the moment mail -> SMS gateway should be configured on a separate host behind a trusted mail relay to avoid receiving messages from unknown mail senders, and should only process mail messages from hosts included in mynetworks Postfix configuration variable.

To fix backscatter issue, debops.smstools role needs to have an external Postfix access policy service which will be used by Postfix to check if a specific mail sender can send SMS messages using the gateway. Steps to determine that:

  • check recipient domain of a mail message,
  • if recipient domain is one of the supported subdomains (sms. or gsm.), check mail address or domain of the sender against list of allowed senders,
  • if mail sender can send SMS messages, return PERMIT (or DUNNO if other checks should be performed),
  • if mail sender is not found, return REJECT,
  • otherwise (mail recipient not in a supported domain), return DUNNO to allow other checks to perform.

Policy service check should be included in smtpd_recipient_restrictions list to be able to check both recipient and sender addresses.

Known bugs

  • sendsms script supports sending SMS messages in UTF-8, but sms-service and sms-transport scripts do not, SMS messages are truncated at first UTF-8 character.

Authors and license

debops.smstools role was written by:

License: GPLv3