exec Module

Jiri Kuthan

FhG FOKUS

Edited by

Jan Janak

Revision History
Revision $Revision: 5901 $$Date$

Table of Contents

1. Admin Guide
1.1. Overview
1.2. Dependencies
1.2.1. OpenSIPS Modules
1.2.2. External Libraries or Applications
1.3. Exported Parameters
1.3.1. setvars (integer)
1.3.2. time_to_kill (integer)
1.3.3. async (integer)
1.4. Exported Functions
1.4.1. exec_dset(command)
1.4.2. exec_msg(command)
1.4.3. exec_avp(command[, avplist])
1.4.4. exec_getenv(environment_variable[, avp])
1.4.5. exec(command, [stdin], [stdout], [stderr], [envavp])
1.5. Known Issues

List of Examples

1.1. Set “setvars” parameter
1.2. Set “time_to_kill” parameter
1.3. Set “async” parameter
1.4. exec_dset usage
1.5. exec_msg usage
1.6. exec_avp usage
1.7. exec_getenv usage
1.8. exec usage

Chapter 1. Admin Guide

1.1. Overview

The Exec module enables the execution of external commands from the OpenSIPS script. Any valid shell commands are accepted. The final input string is evaluated and executed using the "/bin/sh" symlink/binary. OpenSIPS may additionally pass a lot more information about the request using environment variables:

  • SIP_HF_<hf_name> contains value of each header field in request. If a header field occurred multiple times, values are concatenated and comma-separated. <hf_name> is in capital letters. Ff a header-field name occurred in compact form, <hf_name> is canonical.

  • SIP_TID is transaction identifier. All request retransmissions or CANCELs/ACKs associated with a previous INVITE result in the same value.

  • SIP_DID is dialog identifier, which is the same as to-tag. Initially, it is empty.

  • SIP_SRCIP is source IP address from which request came.

  • SIP_ORURI is original request URI.

  • SIP_RURI is current request URI (if unchanged, equal to original).

  • SIP_USER is userpart of current request URI.

  • SIP_OUSER is userpart of original request URI.

NOTE: Any environment variables which are given to the exec module functions must be specified using the '$$' delimiter (e.g., $$SIP_OUSER), otherwise they will be evaluated as OpenSIPS pseudo-variables, throwing scripting errors.

1.2. Dependencies

1.2.1. OpenSIPS Modules

The following modules must be loaded before this module:

  • No dependencies on other OpenSIPS modules.

1.2.2. External Libraries or Applications

The following libraries or applications must be installed before running OpenSIPS with this module loaded:

  • None.

1.3. Exported Parameters

1.3.1. setvars (integer)

Set to 1 to enable setting all above-mentioned environment variables for all executed commands.

WARNING: Before enabling this parameter, make sure your "/bin/sh" is safe from the Shellshock bash vulnerability!!!

Default value is 0 (disabled).

Example 1.1. Set “setvars” parameter

...
modparam("exec", "setvars", 1)
...

1.3.2.  time_to_kill (integer)

Specifies the longest time a program is allowed to execute. If the time is exceeded, the program is killed.

Default value is 0 (disabled).

Example 1.2. Set “time_to_kill” parameter

...
modparam("exec", "time_to_kill", 20)
...

1.3.3. async (integer)

Turns on the asynchronous mode for the 'exec_msg' and 'exec' functions. All commands will be executed by a different process and the caller will continue its flow, without waiting for a response.

Default value is 0 (disabled).

Example 1.3. Set “async” parameter

...
modparam("exec", "async", 1)
...

1.4. Exported Functions

1.4.1.  exec_dset(command)

Executes an external command. The current R-URI is appended to the command as its last parameter. The output of the command will rewrite the current R-URI. Multiple lines of output lead to multiple branches.

Meaning of the parameters is as follows:

  • command (string, pvar) - command to be executed. It can include pseudo-variables or '$$' delimited UNIX environment variables

WARNING: most OpenSIPS scripting variables should be quoted before being passed to external commands, as in: exec_avp("log-call.sh '$ct'"). This may help avoid some unexpected behaviour (e.g. unwanted extra parameters, errors due to special bash characters, etc.)

This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

Example 1.4. exec_dset usage

...
exec_dset("ruri-changer.sh");
exec_dset("ruri-changer.sh '$ct'");
...

1.4.2.  exec_msg(command)

Executes an external command. The current SIP message is passed to it in the standard input, no command-line parameters are added and the output of the command is ignored.

See sip-server/modules/exec/etc/exec.cfg in the source tarball for information on usage.

Meaning of the parameters is as follows:

  • command (string) - command to be executed. It can include pseudo-variables or '$$' delimited UNIX environment variables

WARNING: most OpenSIPS scripting variables should be quoted before being passed to external commands, as in: exec_avp("log-call.sh '$ct'"). This may help avoid some unexpected behaviour (e.g. unwanted extra parameters, errors due to special bash characters, etc.)

This function can be used from REQUEST_ROUTE, FAILURE_ROUTE, LOCAL_ROUTE, TIMER_ROUTE, EVENT_ROUTE, ONREPLY_ROUTE.

Example 1.5. exec_msg usage

...
exec_msg("call-logger.sh '$ct' >> /var/log/call-logger/'$rU'.calls");
...

1.4.3.  exec_avp(command[, avplist])

Executes an external command. Each output line of the command is saved in its corresponding AVP from avplist. If avplist is missing or is incomplete, the populated AVPs will be 1, 2, 3... or N, N+1, N+2...

Meaning of the parameters is as follows:

  • command (string) - command to be executed. It can include pseudo-variables or '$$' delimited UNIX environment variables

  • avplist (string) - comma separated list with AVP names to store the result in

WARNING: most OpenSIPS scripting variables should be quoted before being passed to external commands, as in: exec_avp("log-call.sh '$ct'"). This may help avoid some unexpected behaviour (e.g. unwanted extra parameters, errors due to special bash characters, etc.)

This function can be used from REQUEST_ROUTE, FAILURE_ROUTE, LOCAL_ROUTE, STARTUP_ROUTE, TIMER_ROUTE, EVENT_ROUTE, ONREPLY_ROUTE.

Example 1.6. exec_avp usage

...
exec_avp("get-subscriber-details.sh '$rU'", "$avp(credit) $avp(contract_model)");
...

1.4.4.  exec_getenv(environment_variable[, avp])

Obtains the value of a UNIX evironment_variable. The value is saved in 'avp'. If 'avp' is missing, output will be stored in $avp(1). If there is no such environment variable no value will be returned.

Meaning of the parameters is as follows:

  • environment_variable (string) - environent variable name. Can also be specified as a pseudo-variable

  • avp - an AVP to store the result in

WARNING: any OpenSIPS pseudo-vars which may contain special bash characters should be placed inside quotes, e.g. exec_getenv("'$ct'");

This function can be used from REQUEST_ROUTE, FAILURE_ROUTE, LOCAL_ROUTE, STARTUP_ROUTE, TIMER_ROUTE, EVENT_ROUTE, ONREPLY_ROUTE.

Example 1.7. exec_getenv usage

...
exec_getenv("HOSTNAME");
exec_getenv("HOSTNAME", "$avp(localhost)");
...

1.4.5.  exec(command, [stdin], [stdout], [stderr], [envavp])

Executes an external command. The input is passed to the standard input of the new process, if specified, and the output is saved in the output variable.

Meaning of the parameters is as follows:

  • command - command to be executed.It can include pseudovariables.

  • stdin - String to be passed to the standard input of the command. The string can be given as a pseudovariable.

  • stdout - pseudovariable where to store the output from the standard output of the process. Keep in mind that if this parameter is set, the async paramater will not be taken in consideration.

  • stderr - pseudovariable where to store the error from the standard error of the process.

  • envavp - Avp where to store the values for the environment variables to be passed for the command. The names of the environment variables will be "OSIPS_EXEC_#" where # will start from 0. For example if you store 2 values into an avp ("a" and "b") OSIPS_EXEC_0 will contain the first value and OSIPS_EXEC_1 the second value.

WARNING: any OpenSIPS pseudo-vars which may contain special bash characters should be placed inside quotes, e.g. exec("update-stats.sh '$ct'");

WARNING: "stdin"/"stdout"/"stderr" parameters are not designed for a large amount of data so one should be careful when using them because server could considerably be slowed down.

This function can be used from REQUEST_ROUTE, FAILURE_ROUTE, LOCAL_ROUTE, STARTUP_ROUTE, TIMER_ROUTE, EVENT_ROUTE, ONREPLY_ROUTE.

Example 1.8. exec usage

...
$avp(env) = "a";
$avp(env) = "b";
exec("ls -l", , "$var(out)", "$var(err)", "$avp(env)");
xlog("The output is $var(out)\n");
xlog("Received the following error\n$var(err)");
...
$var(input) = "input";
exec("/home/../myscript.sh", "this is my $var(input) for exec\n", , , "$avp(env)");
...

1.5. Known Issues

When imposing an execution timeout using time_to_kill, make sure your "/bin/sh" is a shell which does not fork when executed, case in which the job itself will not be killed, but rather its parent shell, while the job is silently inherited by "init" and will continue to run. "/bin/dash" is one of these troublesome shell environments.