acl.h

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 1999 - 2012, Digium, Inc.
 *
 * Mark Spencer <markster@digium.com>
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*! \file
 * \brief Access Control of various sorts
 */

#ifndef _ASTERISK_ACL_H
#define _ASTERISK_ACL_H


#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif

#include "asterisk/network.h"
#include "asterisk/linkedlists.h"
#include "asterisk/netsock2.h"
#include "asterisk/io.h"

enum ast_acl_sense {
   AST_SENSE_DENY,
   AST_SENSE_ALLOW
};

/* Host based access control */

/*! \brief internal representation of ACL entries
 * In principle user applications would have no need for this,
 * but there is sometimes a need to extract individual items,
 * e.g. to print them, and rather than defining iterators to
 * navigate the list, and an externally visible 'struct ast_ha_entry',
 * at least in the short term it is more convenient to make the whole
 * thing public and let users play with them.
 */
struct ast_ha {
   /* Host access rule */
   struct ast_sockaddr addr;
   struct ast_sockaddr netmask;
   enum ast_acl_sense sense;
   struct ast_ha *next;
};

#define ACL_NAME_LENGTH 80

/*!
 * \brief an ast_acl is a linked list node of ast_ha structs which may have names.
 *
 * \note These shouldn't be used directly by ACL consumers. Consumers should handle
 *       ACLs via ast_acl_list structs.
 */
struct ast_acl {
   struct ast_ha *acl;             /*!< Rules contained by the ACL */
   int is_realtime;                /*!< If raised, this named ACL was retrieved from realtime storage */
   int is_invalid;                 /*!< If raised, this is an invalid ACL which will automatically reject everything. */
   char name[ACL_NAME_LENGTH];     /*!< If this was retrieved from the named ACL subsystem, this is the name of the ACL. */
   AST_LIST_ENTRY(ast_acl) list;
};

/*! \brief Wrapper for an ast_acl linked list. */
AST_LIST_HEAD(ast_acl_list, ast_acl);

/*!
 * \brief Free a list of HAs
 *
 * \details
 * Given the head of a list of HAs, it and all appended
 * HAs are freed
 *
 * \param ha The head of the list of HAs to free
 * \retval void
 */
void ast_free_ha(struct ast_ha *ha);

/*!
 * \brief Free a list of ACLs
 *
 * \details
 * Given the head of a list of ast_acl structs, it and all appended
 * acl structs will be freed. This includes the ast_ha structs within
 * the individual nodes.
 * \param acl The list of ACLs to free
 * \retval NULL
 */
struct ast_acl_list *ast_free_acl_list(struct ast_acl_list *acl);

/*!
 * \brief Copy the contents of one HA to another
 *
 * \details
 * This copies the internals of the 'from' HA to the 'to'
 * HA. It is important that the 'to' HA has been allocated
 * prior to calling this function
 *
 * \param from Source HA to copy
 * \param to Destination HA to copy to
 * \retval void
 */
void ast_copy_ha(const struct ast_ha *from, struct ast_ha *to);

/*!
 * \brief Add a new rule to a list of HAs
 *
 * \details
 * This adds the new host access rule to the end of the list
 * whose head is specified by the path parameter. Rules are
 * evaluated in a way such that if multiple rules apply to
 * a single IP address/subnet mask, then the rule latest
 * in the list will be used.
 *
 * \param sense Either "permit" or "deny" (Actually any 'p' word will result
 * in permission, and any other word will result in denial)
 * \param stuff The IP address and subnet mask, separated with a '/'. The subnet
 * mask can either be in dotted-decimal format or in CIDR notation (i.e. 0-32).
 * \param path The head of the HA list to which we wish to append our new rule. If
 * NULL is passed, then the new rule will become the head of the list
 * \param[out] error The integer error points to will be set non-zero if an error occurs
 * \return The head of the HA list
 */
struct ast_ha *ast_append_ha(const char *sense, const char *stuff, struct ast_ha *path, int *error);

/*!
 * \brief Add a rule to an ACL struct
 *
 * \details
 * This adds a named ACL or an ACL rule to an ast_acl container.
 * It works in a similar way to ast_append_ha.
 *
 * \param sense Can be any among "permit", "deny", or "acl"
 *        this controls whether the rule being added will simply modify the unnamed ACL at the head of the list
 *        or if a new named ACL will be added to that ast_acl.
 * \param stuff If sense is 'permit'/'deny', this is the ip address and subnet mask separated with a '/' like in ast_append ha.
 *        If it sense is 'acl', then this will be the name of the ACL being appended to the container.
 * \param path Address of the ACL list being appended
 * \param[out] error The int that error points to will be set to 1 if an error occurs.
 * \param[out] named_acl_flag This will raise a flag under certain conditions to indicate that a named ACL has been added by this
 *        operation. This may be used to indicate that an event subscription should be made against the named ACL subsystem.
 *        Note: This flag may be raised by this function, but it will never be lowered by it.
 */
void ast_append_acl(const char *sense, const char *stuff, struct ast_acl_list **path, int *error, int *named_acl_flag);

/*!
 * \brief Determines if an ACL is empty or if it contains entries
 *
 * \param acl_list The ACL list being checked
 * \retval 0 - the list is not empty
 * \retval 1 - the list is empty
 */
int ast_acl_list_is_empty(struct ast_acl_list *acl_list);

/*!
 * \brief Apply a set of rules to a given IP address
 *
 * \details
 * The list of host access rules is traversed, beginning with the
 * input rule. If the IP address given matches a rule, the "sense"
 * of that rule is used as the return value. Note that if an IP
 * address matches multiple rules that the last one matched will be
 * the one whose sense will be returned.
 *
 * \param ha The head of the list of host access rules to follow
 * \param addr An ast_sockaddr whose address is considered when matching rules
 * \retval AST_SENSE_ALLOW The IP address passes our ACL
 * \retval AST_SENSE_DENY The IP address fails our ACL
 */
enum ast_acl_sense ast_apply_ha(const struct ast_ha *ha, const struct ast_sockaddr *addr);

/*!
 * \brief Apply a set of rules to a given IP address
 *
 * \details
 * Similar to the above, only uses an acl container, which is a whole slew
 * of ast_ha lists. It runs ast_apply_ha on each of the ast_ha structs
 * contained in the acl container. It will deny if any of the ast_ha lists
 * fail, and it will pass only if all of the rules pass.
 *
 * \param acl The head of the list of ACLs to evaluate
 * \param addr An ast_sockaddr whose address is considered when matching rules
 * \param purpose Context for which the ACL is being applied - Establishes purpose of a notice when rejected
 *
 * \retval AST_SENSE_ALLOW The IP address passes our ACLs
 * \retval AST_SENSE_DENY The IP address fails our ACLs
 */
enum ast_acl_sense ast_apply_acl(struct ast_acl_list *acl_list, const struct ast_sockaddr *addr, const char *purpose);

/*!
 * \brief Get the IP address given a hostname
 *
 * \details
 * Similar in nature to ast_gethostbyname, except that instead
 * of getting an entire hostent structure, you instead are given
 * only the IP address inserted into a ast_sockaddr structure.
 *
 * \param addr The IP address found.  The address family is used
 * as an input parameter to filter the returned addresses.  If
 * it is 0, both IPv4 and IPv6 addresses can be returned.
 * \param hostname The hostname to look up
 *
 * \retval 0 Success
 * \retval -1 Failure
 */
int ast_get_ip(struct ast_sockaddr *addr, const char *hostname);

/*!
 * \brief Get the IP address given a hostname and optional service
 *
 * \details
 * If the service parameter is non-NULL, then an SRV lookup will be made by
 * prepending the service to the hostname parameter, separated by a '.'
 * For example, if hostname is "example.com" and service is "_sip._udp" then
 * an SRV lookup will be done for "_sip._udp.example.com". If service is NULL,
 * then this function acts exactly like a call to ast_get_ip.
 *
 * \param addr The IP address found.  The address family is used
 * as an input parameter to filter the returned addresses.  If
 * it is 0, both IPv4 and IPv6 addresses can be returned.
 *
 * \param hostname The hostname to look up
 * \param service A specific service provided by the host. A NULL service results
 * in an A-record lookup instead of an SRV lookup
 * \retval 0 Success
 * \retval -1 Failure
 */
int ast_get_ip_or_srv(struct ast_sockaddr *addr, const char *hostname, const char *service);

/*!
 * \brief Get our local IP address when contacting a remote host
 *
 * \details
 * This function will attempt to connect(2) to them over UDP using a source
 * port of 5060. If the connect(2) call is successful, then we inspect the
 * sockaddr_in output parameter of connect(2) to determine the IP address
 * used to connect to them. This IP address is then copied into us.
 *
 * \param them The IP address to which we wish to attempt to connect
 * \param[out] us The source IP address used to connect to them
 * \retval -1 Failure
 * \retval 0 Success
 */
int ast_ouraddrfor(const struct ast_sockaddr *them, struct ast_sockaddr *us);

/*!
 * \brief Find an IP address associated with a specific interface
 *
 * \details
 * Given an interface such as "eth0" we find the primary IP address
 * associated with it using the SIOCGIFADDR ioctl. If the ioctl call
 * should fail, we populate address with 0s.
 *
 * \note
 * This function is not actually used anywhere
 *
 * \param iface The interface name whose IP address we wish to find
 * \param[out] address The interface's IP address is placed into this param
 * \retval -1 Failure. address is filled with 0s
 * \retval 0 Success
 */
int ast_lookup_iface(char *iface, struct ast_sockaddr *address);

/*!
 * \brief Duplicate the contents of a list of host access rules
 *
 * \details
 * A deep copy of all ast_has in the list is made. The returned
 * value is allocated on the heap and must be freed independently
 * of the input parameter when finished.
 *
 * \param original The ast_ha to copy
 * \retval The head of the list of duplicated ast_has
 */
struct ast_ha *ast_duplicate_ha_list(struct ast_ha *original);

/*!
 * \brief Duplicates the contests of a list of lists of host access rules.
 *
 * \details
 * A deep copy of an ast_acl list is made (which in turn means a deep copy of
 * each of the ast_ha structs contained within). The returned value is allocated
 * on the heap and must be freed independently of the input paramater when
 * finished.
 *
 * \param original The ast_acl_list to copy
 * \retval The new duplicated ast_acl_list
 */
struct ast_acl_list *ast_duplicate_acl_list(struct ast_acl_list *original);

/*!
 * \brief Find our IP address
 *
 * \details
 * This function goes through many iterations in an attempt to find
 * our IP address. If any step along the way should fail, we move to the
 * next item in the list. Here are the steps taken:
 * - If bindaddr has a non-zero IP address, that is copied into ourip
 * - We use a combination of gethostname and ast_gethostbyname to find our
 *   IP address.
 * - We use ast_ouraddrfor with 198.41.0.4 as the destination IP address
 * - We try some platform-specific socket operations to find the IP address
 *
 * \param[out] ourip Our IP address is written here when it is found
 * \param bindaddr A hint used for finding our IP. See the steps above for
 * more details
 * \param family Only addresses of the given family will be returned. Use 0
 * or AST_SOCKADDR_UNSPEC to get addresses of all families.
 * \retval 0 Success
 * \retval -1 Failure
 */
int ast_find_ourip(struct ast_sockaddr *ourip, const struct ast_sockaddr *bindaddr, int family);

/*!
 * \brief Convert a string to the appropriate COS value
 *
 * \param value The COS string to convert
 * \param[out] cos The integer representation of that COS value
 * \retval -1 Failure
 * \retval 0 Success
 */
int ast_str2cos(const char *value, unsigned int *cos);

/*!
 * \brief Convert a string to the appropriate TOS value
 *
 * \param value The TOS string to convert
 * \param[out] tos The integer representation of that TOS value
 * \retval -1 Failure
 * \retval 0 Success
 */
int ast_str2tos(const char *value, unsigned int *tos);

/*!
 * \brief Convert a TOS value into its string representation
 *
 * \param tos The TOS value to look up
 * \return The string equivalent of the TOS value
 */
const char *ast_tos2str(unsigned int tos);

/*!
 * \brief Retrieve a named ACL
 *
 * \details
 * This function attempts to find a named ACL. If found, a copy
 * of the requested ACL will be made which must be freed by
 * the caller.
 *
 * \param name Name of the ACL sought
 * \param[out] is_realtime will be true if the ACL being returned is from realtime
 * \param[out] is_undefined will be true if no ACL profile can be found for the requested name
 *
 * \retval A copy of the named ACL as an ast_ha
 * \retval NULL if no ACL could be found.
 */
struct ast_ha *ast_named_acl_find(const char *name, int *is_realtime, int *is_undefined);

/*!
 * \brief Initialize and configure the named ACL system.
 *
 * \details
 * This function will prepare the named ACL system for use.
 * For this reason, it needs to be called before other things that use ACLs are initialized.
 */
int ast_named_acl_init(void);

/*!
 * \brief reload/reconfigure the named ACL system.
 *
 * \details
 * This function is designed to trigger an event upon a successful reload that may update
 * ACL consumers.
 */
int ast_named_acl_reload(void);

#if defined(__cplusplus) || defined(c_plusplus)
}
#endif

#endif /* _ASTERISK_ACL_H */