permissions Module

Miklos Tirpak

Edited by

Miklos Tirpak

Edited by

Bogdan-Andrei Iancu

Edited by

Juha Heinanen

Edited by

Irina-Maria Stanescu

   Copyright © 2003 Miklos Tirpak

   Copyright © 2006-2008 Juha Heinanen

   Copyright © 2009 Irina-Maria Stanescu
   Revision History
   Revision $Revision$ $Date: 2013-01-29 14:35:11 +0200
                              (Tue, 29 Jan 2013) $
     __________________________________________________________

   Table of Contents

   1. Admin Guide

        1.1. Overview

              1.1.1. Call Routing
              1.1.2. Registration Permissions
              1.1.3. URI Permissions
              1.1.4. Address Permissions

        1.2. Dependencies

              1.2.1. OpenSIPS Modules
              1.2.2. External Libraries or Applications

        1.3. Exported Parameters

              1.3.1. default_allow_file (string)
              1.3.2. default_deny_file (string)
              1.3.3. check_all_branches (integer)
              1.3.4. allow_suffix (string)
              1.3.5. deny_suffix (string)
              1.3.6. db_url (string)
              1.3.7. address_table (string)
              1.3.8. grp_col (string)
              1.3.9. ip_col (string)
              1.3.10. mask_col (string)
              1.3.11. port_col (string)
              1.3.12. proto_col (string)
              1.3.13. pattern_col (string)
              1.3.14. info_col (string)

        1.4. Exported Functions

              1.4.1. allow_routing()
              1.4.2. allow_routing(basename)
              1.4.3. allow_routing(allow_file,deny_file)
              1.4.4. allow_register(basename)
              1.4.5. allow_register(allow_file, deny_file)
              1.4.6. allow_uri(basename, pvar)
              1.4.7. check_address(group_id, ip, port, proto [,
                      context_info [, pattern]])

              1.4.8. check_source_address(group_id [, context_info
                      [, pattern]])

              1.4.9. get_source_group(pvar)

        1.5. Exported MI Functions

              1.5.1. address_reload
              1.5.2. address_dump
              1.5.3. subnet_dump
              1.5.4. allow_uri

   List of Examples

   1.1. Set default_allow_file parameter
   1.2. Set default_deny_file parameter
   1.3. Set check_all_branches parameter
   1.4. Set allow_suffix parameter
   1.5. Set deny_suffix parameter
   1.6. Set db_url parameter
   1.7. Set address_table parameter
   1.8. Set grp_col parameter
   1.9. Set ip_col parameter
   1.10. Set mask_col parameter
   1.11. Set port_col parameter
   1.12. Set proto_col parameter
   1.13. Set pattern_col parameter
   1.14. Set info_col parameter
   1.15. allow_routing usage
   1.16. allow_routing(basename) usage
   1.17. allow_routing(allow_file, deny_file) usage
   1.18. allow_register(basename) usage
   1.19. allow_register(allow_file, deny_file) usage
   1.20. allow_uri(basename, pvar) usage
   1.21. check_address() usage
   1.22. check_source_address() usage
   1.23. get_source_group() usage

Chapter 1. Admin Guide

1.1. Overview

1.1.1. Call Routing

   The module can be used to determine if a call has appropriate
   permission to be established. Permission rules are stored in
   plaintext configuration files similar to hosts.allow and
   hosts.deny files used by tcpd.

   When allow_routing function is called it tries to find a rule
   that matches selected fields of the message.

   OpenSIPS is a forking proxy and therefore a single message can
   be sent to different destinations simultaneously. When checking
   permissions all the destinations must be checked and if one of
   them fails, the forwarding will fail.

   The matching algorithm is as follows, first match wins:
     * Create a set of pairs of form (From, R-URI of branch 1),
       (From, R-URI of branch 2), etc.
     * Routing will be allowed when all pairs match an entry in
       the allow file.
     * Otherwise routing will be denied when one of pairs matches
       an entry in the deny file.
     * Otherwise, routing will be allowed.

   A non-existing permission control file is treated as if it were
   an empty file. Thus, permission control can be turned off by
   providing no permission control files.

   From header field and Request-URIs are always compared with
   regular expressions! For the syntax see the sample file:
   config/permissions.allow.

1.1.2. Registration Permissions

   In addition to call routing it is also possible to check
   REGISTER messages and decide--based on the configuration
   files--whether the message should be allowed and the
   registration accepted or not.

   Main purpose of the function is to prevent registration of
   "prohibited" IP addresses. One example, when a malicious user
   registers a contact containing IP address of a PSTN gateway, he
   might be able to bypass authorization checks performed by the
   SIP proxy. That is undesirable and therefore attempts to
   register IP address of a PSTN gateway should be rejected. Files
   config/register.allow and config/register.deny contain an
   example configuration.

   Function for registration checking is called allow_register and
   the algorithm is very similar to the algorithm described in
   Section 1.1.1, “Call Routing”. The only difference is in the
   way how pairs are created.

   Instead of From header field the function uses To header field
   because To header field in REGISTER messages contains the URI
   of the person being registered. Instead of the Request-URI of
   branches the function uses Contact header field.

   Thus, pairs used in matching will look like this: (To, Contact
   1), (To, Contact 2), (To, Contact 3), and so on..

   The algorithm of matching is same as described in
   Section 1.1.1, “Call Routing”.

1.1.3. URI Permissions

   The module can be used to determine if request is allowed to
   the destination specified by an URI stored in a pvar.
   Permission rules are stored in plaintext configuration files
   similar to hosts.allow and hosts.deny used by tcpd.

   When allow_uri function is called, it tries to find a rule that
   matches selected fields of the message. The matching algorithm
   is as follows, first match wins:
     * Create a pair <From URI, URI stored in pvar>.
     * Request will be allowed when the pair matches an entry in
       the allow file.
     * Otherwise request will be denied when the pair matches an
       entry in the deny file.
     * Otherwise, request will be allowed.

   A non-existing permission control file is treated as if it were
   an empty file. Thus, permission control can be turned off by
   providing no permission control files.

   From URI and URI stored in pvar are always compared with
   regular expressions! For the syntax see the sample file:
   config/permissions.allow.

1.1.4. Address Permissions

   The module can be used to determine if an address (IP address
   and port) matches any of the IP subnets stored in cached
   OpenSIPS database table. Port 0 in cached database table
   matches any port. Group ID, IP address, port and transport
   protocol values to be matched can be either taken from the
   request (check_source_address) or given as pvar arguments or
   directly as strings(check_address).

   Addresses stored in cached database table can be grouped
   together into one or more groups specified by a group
   identifier (unsigned integer). Group identifier is given as
   argument to check_address and check_source_address.

   Otherwise the request is rejected.

   The address database table is specified by module parameters.

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. default_allow_file (string)

   Default allow file used by functions without parameters. If you
   don't specify full pathname then the directory in which is the
   main config file is located will be used.

   Default value is “permissions.allow”.

   Example 1.1. Set default_allow_file parameter
...
modparam("permissions", "default_allow_file", "/etc/permissions.allow")
...

1.3.2. default_deny_file (string)

   Default file containing deny rules. The file is used by
   functions without parameters. If you don't specify full
   pathname then the directory in which the main config file is
   located will be used.

   Default value is “permissions.deny”.

   Example 1.2. Set default_deny_file parameter
...
modparam("permissions", "default_deny_file", "/etc/permissions.deny")
...

1.3.3. check_all_branches (integer)

   If set then allow_routing functions will check Request-URI of
   all branches (default). If disabled then only Request-URI of
   the first branch will be checked.

Warning

   Do not disable this parameter unless you really know what you
   are doing.

   Default value is 1.

   Example 1.3. Set check_all_branches parameter
...
modparam("permissions", "check_all_branches", 0)
...

1.3.4. allow_suffix (string)

   Suffix to be appended to basename to create filename of the
   allow file when version with one parameter of either
   allow_routing or allow_register is used.

Note

   Including leading dot.

   Default value is “.allow”.

   Example 1.4. Set allow_suffix parameter
...
modparam("permissions", "allow_suffix", ".allow")
...

1.3.5. deny_suffix (string)

   Suffix to be appended to basename to create filename of the
   deny file when version with one parameter of either
   allow_routing or allow_register is used.

Note

   Including leading dot.

   Default value is “.deny”.

   Example 1.5. Set deny_suffix parameter
...
modparam("permissions", "deny_suffix", ".deny")
...

1.3.6. db_url (string)

   This is URL of the database to be used.

   Default value is “NULL”.

   Example 1.6. Set db_url parameter
...
modparam("permissions", "db_url", "dbdriver://username:password@dbhost/d
bname")
...

1.3.7. address_table (string)

   Name of database table containing matching rules used by
   allow_register function.

   Default value is “address”.

   Example 1.7. Set address_table parameter
...
modparam("permissions", "address_table", "pbx")
...

1.3.8. grp_col (string)

   Name of address table column containing group identifier of the
   address.

   Default value is “grp”.

   Example 1.8. Set grp_col parameter
...
modparam("permissions", "grp_col", "group_id")
...

1.3.9. ip_col (string)

   Name of address table column containing IP address part of the
   address.

   Default value is “ip”.

   Example 1.9. Set ip_col parameter
...
modparam("permissions", "ip_col", "ipess")
...

1.3.10. mask_col (string)

   Name of address table column containing network mask of the
   address. Possible values are 0-32.

   Default value is “mask”.

   Example 1.10. Set mask_col parameter
...
modparam("permissions", "mask_col", "subnet_length")
...

1.3.11. port_col (string)

   Name of address table column containing port part of the
   address.

   Default value is “port”.

   Example 1.11. Set port_col parameter
...
modparam("permissions", "port_col", "prt")
...

1.3.12. proto_col (string)

   Name of address table column containing transport protocol that
   is matched against transport protocol of received request.
   Possible values that can be stored in proto_col are “any”,
   “udp”, “tcp”, “tls”, “sctp”, and “none”. Value “any” matches
   always and value “none” never.

   Default value is “proto”.

   Example 1.12. Set proto_col parameter
...
modparam("permissions", "proto_col", "transport")
...

1.3.13. pattern_col (string)

   Name of address table column containing regular expression that
   is matched against the arguments received by check_address or
   check_source_address.

   Default value is “pattern”.

   Example 1.13. Set pattern_col parameter
...
modparam("permissions", "pattern_col", "regexp")
...

1.3.14. info_col (string)

   Name of address table column containing a string that is added
   as value to a pvar given as argument to check_address or
   check_source_address in case the function succedes.

   Default value is “context_info”.

   Example 1.14. Set info_col parameter
...
modparam("permissions", "info_col", "info_col")
...

1.4. Exported Functions

1.4.1.  allow_routing()

   Returns true if all pairs constructed as described in
   Section 1.1.1, “Call Routing” have appropriate permissions
   according to the configuration files. This function uses
   default configuration files specified in default_allow_file and
   default_deny_file.

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

   Example 1.15. allow_routing usage
...
if (allow_routing()) {
        t_relay();
};
...

1.4.2.  allow_routing(basename)

   Returns true if all pairs constructed as described in
   Section 1.1.1, “Call Routing” have appropriate permissions
   according to the configuration files given as parameters.

   Meaning of the parameters is as follows:
     * basename - Basename from which allow and deny filenames
       will be created by appending contents of allow_suffix and
       deny_suffix parameters.
       If the parameter doesn't contain full pathname then the
       function expects the file to be located in the same
       directory as the main configuration file of the server.

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

   Example 1.16. allow_routing(basename) usage
...
if (allow_routing("basename")) {
        t_relay();
};
...

1.4.3.  allow_routing(allow_file,deny_file)

   Returns true if all pairs constructed as described in
   Section 1.1.1, “Call Routing” have appropriate permissions
   according to the configuration files given as parameters.

   Meaning of the parameters is as follows:
     * allow_file - File containing allow rules.
       If the parameter doesn't contain full pathname then the
       function expects the file to be located in the same
       directory as the main configuration file of the server.
     * deny_file - File containing deny rules.
       If the parameter doesn't contain full pathname then the
       function expects the file to be located in the same
       directory as the main configuration file of the server.

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

   Example 1.17. allow_routing(allow_file, deny_file) usage
...
if (allow_routing("rules.allow", "rules.deny")) {
        t_relay();
};
...

1.4.4.  allow_register(basename)

   The function returns true if all pairs constructed as described
   in Section 1.1.2, “Registration Permissions” have appropriate
   permissions according to the configuration files given as
   parameters.

   Meaning of the parameters is as follows:
     * basename - Basename from which allow and deny filenames
       will be created by appending contents of allow_suffix and
       deny_suffix parameters.
       If the parameter doesn't contain full pathname then the
       function expects the file to be located in the same
       directory as the main configuration file of the server.

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

   Example 1.18. allow_register(basename) usage
...
if (method=="REGISTER") {
        if (allow_register("register")) {
                save("location");
                exit;
        } else {
                sl_send_reply("403", "Forbidden");
        };
};
...

1.4.5.  allow_register(allow_file, deny_file)

   The function returns true if all pairs constructed as described
   in Section 1.1.2, “Registration Permissions” have appropriate
   permissions according to the configuration files given as
   parameters.

   Meaning of the parameters is as follows:
     * allow_file - File containing allow rules.
       If the parameter doesn't contain full pathname then the
       function expects the file to be located in the same
       directory as the main configuration file of the server.
     * deny_file - File containing deny rules.
       If the parameter doesn't contain full pathname then the
       function expects the file to be located in the same
       directory as the main configuration file of the server.

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

   Example 1.19. allow_register(allow_file, deny_file) usage
...
if (method=="REGISTER") {
        if (allow_register("register.allow", "register.deny")) {
                save("location");
                exit;
        } else {
                sl_send_reply("403", "Forbidden");
        };
};
...

1.4.6.  allow_uri(basename, pvar)

   Returns true if the pair constructed as described in
   Section 1.1.3, “URI Permissions” have appropriate permissions
   according to the configuration files specified by the
   parameter.

   Meaning of the parameter is as follows:
     * basename - Basename from which allow and deny filenames
       will be created by appending contents of allow_suffix and
       deny_suffix parameters.
       If the parameter doesn't contain full pathname then the
       function expects the file to be located in the same
       directory as the main configuration file of the server.
     * pvar - Any pseudo-variable defined in OpenSIPS.

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

   Example 1.20. allow_uri(basename, pvar) usage
...
if (allow_uri("basename", "$rt")) {  // Check Refer-To URI
        t_relay();
};
if (allow_uri("basename", "$avp(uri)") {  // Check URI stored in $avp(ur
i)
        t_relay();
};
...

1.4.7.  check_address(group_id, ip, port, proto [, context_info [,
pattern]])

   Returns 1 if group id, IP address, port and protocol given as
   arguments match an IP subnet found in cached address table, as
   described in Section 1.1.4, “Address Permissions” . The
   function takes 4 mandatory arguments and 2 optional ones.

   This function can be useful to check if a request can be
   allowed without authentication.

   Meaning of the parameter is as follows:
     * group_id
       This argument represents the group id to be matched. It can
       be an integer string or a string pvar. If the group_id
       argument is "0", the query can match any group in the
       cached address table.
     * ip
       This argument represents the ip address to be matched. It
       can be an given directly as string or as a string pvar.
       This argument cannot be null/empty.
     * port
       This argument represents the port to be matched. It can be
       an given as an integer string or as a string pvar. Cached
       address table entry containing port value 0 matches any
       port. Also, a "0" value for the argument can match any port
       in the address table.
     * proto
       This argument represents the protocol used for transport;
       it can be an given as string or as string pvar. Transport
       protocol is either "ANY" or any valid transport protocol
       value: "UDP, "TCP", "TLS", and "SCTP".
     * context_info
       This argument represents the pvar in wich the context_info
       field from the cached address table will be stored in case
       of match. This argument is optional.
     * pattern
       This argument is a string to be matched with the regular
       expression pattern field from the cached address table.
       This argument is optional.

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

   Example 1.21. check_address() usage
...

// Checks if the tuple IP address/port (given as strings) and source pro
tocol
// (given as pvar), belongs to group 4, verifies if pattern string "text
test"
// matches the regular expression field in the database table and stores
 the
// context information in $avp(ctx)
if (check_address("4","192.168.2.135","5700","$proto","$avp(ctx)", "text
test")) {
        t_relay();
        xlog("$avp(ctx)\n");
}

...

// Checks if the tuple IP address/port/protocol of the source message is
 in group 4
if (check_address("4","$si","$sp","$proto")) {
        t_relay();
}

...

// Checks if the tuple IP address/port/protocol stored in AVPs s:ip/s:po
rt/s:proto
// is in group 4 and stores context information in $avp(ctx)
$avp(ip) = "192.168.2.135";
$avp(port) = 5061;
$avp(proto) = "any";
if (check_address("4","$avp(ip)","$avp(port)","$avp(proto)","$avp(ctx)))
 {
        t_relay();
        xlog("$avp(ctx)\n");
}

...

// Checks if the tuple IP address/port (given as strings) and source pro
tocol
// (given as pvar) is in group 4, verifies if pattern string  "texttest"
 matches
// the regular expression field in the database table, without storing a
ny
// context information
if (check_address("4","$si","5700","$proto","", "texttest")) {
        t_relay();
}

...


1.4.8.  check_source_address(group_id [, context_info [, pattern]])

   Equivalent to check_address(group_id, "$si", "$sp", "$proto",
   context_info, pattern).

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

   Example 1.22. check_source_address() usage
...
// Check if source address/port/proto is in group 4 and stores
// context information in $avp(ctx)
if (check_source_address("4","$avp(ctx)")) {
        xlog("$avp(ctx)\n");
}else {
        sl_send_reply("403", "Forbidden");
}
...

1.4.9.  get_source_group(pvar)

   Checks if an entry with the source ip/port/protocol is found in
   cached address or subnet table in any group. If yes, returns
   that group in the pvar parameter. If not returns -1. Port value
   0 in cached address and subnet table matches any port.

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

   Example 1.23. get_source_group() usage

...

if ( get_source_group("$var(group)") ) {
   # do something with $var(group)
   xlog("group is $var(group)\n");
};
...


1.5. Exported MI Functions

1.5.1.  address_reload

   Causes permissions module to re-read the contents of the
   address database table into cache memory. In cache memory the
   entries are for performance reasons stored in two different
   tables: address table and subnet table depending on the value
   of the mask field (32 or smaller).

   Parameters: none

1.5.2.  address_dump

   Causes permissions module to dump contents of the address table
   from cache memory.

   Parameters: none

1.5.3.  subnet_dump

   Causes permissions module to dump contents of cache memory
   subnet table.

   Parameters: none

1.5.4.  allow_uri

   Tests if (URI, Contact) pair is allowed according to allow/deny
   files. The files must already have been loaded by OpenSIPS.

   Parameters:
     * basename - Basename from which allow and deny filenames
       will be created by appending contents of allow_suffix and
       deny_suffix parameters.
     * URI - URI to be tested
     * Contact - Contact to be tested
