mynetworks.c

[詳解]

/*++
/* NAME
/*  mynetworks 3
/* SUMMARY
/*  generate patterns for my own interface addresses
/* SYNOPSIS
/*  #include <mynetworks.h>
/*
/*  const char *mynetworks()
/* AUXILIARY FUNCTIONS
/*  const char *mynetworks_host()
/* DESCRIPTION
/*  This routine uses the address list built by own_inet_addr()
/*  to produce a list of patterns that match the corresponding
/*  networks.
/*
/*  The interface list is specified with the "inet_interfaces"
/*  configuration parameter.
/*
/*  The address to netblock conversion style is specified with
/*  the "mynetworks_style" parameter: one of "class" (match
/*  whole class A, B, C or D networks), "subnet" (match local
/*  subnets), or "host" (match local interfaces only).
/*
/*  mynetworks_host() uses the "host" style.
/* LICENSE
/* .ad
/* .fi
/*  The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/*  Wietse Venema
/*  IBM T.J. Watson Research
/*  P.O. Box 704
/*  Yorktown Heights, NY 10598, USA
/*
/*  Dean C. Strik
/*  Department ICT Services
/*  Eindhoven University of Technology
/*  P.O. Box 513
/*  5600 MB  Eindhoven, Netherlands
/*  E-mail: <dean@ipnet6.org>
/*--*/

/* System library. */

#include <sys_defs.h>
#include <sys/param.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#ifndef IN_CLASSD_NET
#define IN_CLASSD_NET       0xf0000000
#define IN_CLASSD_NSHIFT    28
#endif

/* Utility library. */

#include <msg.h>
#include <vstring.h>
#include <inet_addr_list.h>
#include <name_mask.h>
#include <myaddrinfo.h>
#include <mask_addr.h>
#include <argv.h>
#include <inet_proto.h>
#include <mymalloc.h>

/* Global library. */

#include <own_inet_addr.h>
#include <mail_params.h>
#include <mynetworks.h>
#include <sock_addr.h>
#include <been_here.h>

/* Application-specific. */

#define MASK_STYLE_CLASS    (1 << 0)
#define MASK_STYLE_SUBNET   (1 << 1)
#define MASK_STYLE_HOST     (1 << 2)

static const NAME_MASK mask_styles[] = {
    MYNETWORKS_STYLE_CLASS, MASK_STYLE_CLASS,
    MYNETWORKS_STYLE_SUBNET, MASK_STYLE_SUBNET,
    MYNETWORKS_STYLE_HOST, MASK_STYLE_HOST,
    0,
};

/* mynetworks_core - return patterns for specific mynetworks style */

static const char *mynetworks_core(const char *style)
{
    const char *myname = "mynetworks_core";
    VSTRING *result;
    INET_ADDR_LIST *my_addr_list;
    INET_ADDR_LIST *my_mask_list;
    unsigned shift;
    unsigned junk;
    int     i;
    unsigned mask_style;
    struct sockaddr_storage *sa;
    struct sockaddr_storage *ma;
    int     net_mask_count = 0;
    ARGV   *argv;
    BH_TABLE *dup_filter;
    char  **cpp;

    /*
     * Avoid run-time errors when all network protocols are disabled. We
     * can't look up interface information, and we can't convert explicit
     * names or addresses.
     */
    if (inet_proto_info()->ai_family_list[0] == 0) {
    if (msg_verbose)
        msg_info("skipping %s setting - "
             "all network protocols are disabled",
             VAR_MYNETWORKS);
    return (mystrdup(""));
    }
    mask_style = name_mask("mynetworks mask style", mask_styles, style);

    /*
     * XXX Workaround: name_mask() needs a flags argument so that we can
     * require exactly one value, or we need to provide an API that is
     * dedicated for single-valued flags.
     * 
     * XXX Why not use name_code() instead?
     */
    for (i = 0, junk = mask_style; junk != 0; junk >>= 1U)
    i += (junk & 1);
    if (i != 1)
    msg_fatal("bad %s value: %s; specify exactly one value",
          VAR_MYNETWORKS_STYLE, var_mynetworks_style);

    result = vstring_alloc(20);
    my_addr_list = own_inet_addr_list();
    my_mask_list = own_inet_mask_list();

    for (sa = my_addr_list->addrs, ma = my_mask_list->addrs;
     sa < my_addr_list->addrs + my_addr_list->used;
     sa++, ma++) {
    unsigned long addr;
    unsigned long mask;
    struct in_addr net;

    if (SOCK_ADDR_FAMILY(sa) == AF_INET) {
        addr = ntohl(SOCK_ADDR_IN_ADDR(sa).s_addr);
        mask = ntohl(SOCK_ADDR_IN_ADDR(ma).s_addr);

        switch (mask_style) {

        /*
         * Natural mask. This is dangerous if you're customer of an
         * ISP who gave you a small portion of their network.
         */
        case MASK_STYLE_CLASS:
        if (IN_CLASSA(addr)) {
            mask = IN_CLASSA_NET;
            shift = IN_CLASSA_NSHIFT;
        } else if (IN_CLASSB(addr)) {
            mask = IN_CLASSB_NET;
            shift = IN_CLASSB_NSHIFT;
        } else if (IN_CLASSC(addr)) {
            mask = IN_CLASSC_NET;
            shift = IN_CLASSC_NSHIFT;
        } else if (IN_CLASSD(addr)) {
            mask = IN_CLASSD_NET;
            shift = IN_CLASSD_NSHIFT;
        } else {
            msg_fatal("%s: unknown address class: %s",
                  myname, inet_ntoa(SOCK_ADDR_IN_ADDR(sa)));
        }
        break;

        /*
         * Subnet mask. This is less unsafe, but still bad if you're
         * connected to a large subnet.
         */
        case MASK_STYLE_SUBNET:
        for (junk = mask, shift = MAI_V4ADDR_BITS; junk != 0;
             shift--, junk <<= 1)
             /* void */ ;
        break;

        /*
         * Host only. Do not relay authorize other hosts.
         */
        case MASK_STYLE_HOST:
        mask = ~0UL;
        shift = 0;
        break;

        default:
        msg_panic("unknown mynetworks mask style: %s",
              var_mynetworks_style);
        }
        net.s_addr = htonl(addr & mask);
        vstring_sprintf_append(result, "%s/%d ",
                   inet_ntoa(net), MAI_V4ADDR_BITS - shift);
        net_mask_count++;
        continue;
    }
#ifdef HAS_IPV6
    else if (SOCK_ADDR_FAMILY(sa) == AF_INET6) {
        MAI_HOSTADDR_STR hostaddr;
        unsigned char *ac;
        unsigned char *end;
        unsigned char ch;
        struct sockaddr_in6 net6;

        switch (mask_style) {

        /*
         * There are no classes for IPv6. We default to subnets
         * instead.
         */
        case MASK_STYLE_CLASS:

        /* FALLTHROUGH */

        /*
         * Subnet mask.
         */
        case MASK_STYLE_SUBNET:
        ac = (unsigned char *) &SOCK_ADDR_IN6_ADDR(ma);
        end = ac + sizeof(SOCK_ADDR_IN6_ADDR(ma));
        shift = MAI_V6ADDR_BITS;
        while (ac < end) {
            if ((ch = *ac++) == (unsigned char) ~0U) {
            shift -= CHAR_BIT;
            continue;
            } else {
            while (ch != 0)
                shift--, ch <<= 1;
            break;
            }
        }
        break;

        /*
         * Host only. Do not relay authorize other hosts.
         */
        case MASK_STYLE_HOST:
        shift = 0;
        break;

        default:
        msg_panic("unknown mynetworks mask style: %s",
              var_mynetworks_style);
        }
        /* FIX 200501: IPv6 patch did not clear host bits. */
        net6 = *SOCK_ADDR_IN6_PTR(sa);
        mask_addr((unsigned char *) &net6.sin6_addr,
              sizeof(net6.sin6_addr),
              MAI_V6ADDR_BITS - shift);
        SOCKADDR_TO_HOSTADDR(SOCK_ADDR_PTR(&net6), SOCK_ADDR_LEN(&net6),
                 &hostaddr, (MAI_SERVPORT_STR *) 0, 0);
        vstring_sprintf_append(result, "[%s]/%d ",
                   hostaddr.buf, MAI_V6ADDR_BITS - shift);
        net_mask_count++;
        continue;
    }
#endif
    else {
        msg_warn("%s: skipping unknown address family %d",
             myname, SOCK_ADDR_FAMILY(sa));
        continue;
    }
    }

    /*
     * FIX 200501 IPv6 patch produced repeated results. Some systems report
     * the same interface multiple times, notably multi-homed systems with
     * IPv6 link-local or site-local addresses. A straight-forward sort+uniq
     * produces ugly results, though. Instead we preserve the original order
     * and use a duplicate filter to suppress repeated information.
     */
    if (net_mask_count > 1) {
    argv = argv_split(vstring_str(result), " ");
    VSTRING_RESET(result);
    dup_filter = been_here_init(net_mask_count, BH_FLAG_NONE);
    for (cpp = argv->argv; cpp < argv->argv + argv->argc; cpp++)
        if (!been_here_fixed(dup_filter, *cpp))
        vstring_sprintf_append(result, "%s ", *cpp);
    argv_free(argv);
    been_here_free(dup_filter);
    }
    if (msg_verbose)
    msg_info("%s: %s", myname, vstring_str(result));
    return (vstring_export(result));
}

/* mynetworks - return patterns that match my own networks */

const char *mynetworks(void)
{
    static const char *result;

    if (result == 0)
    result = mynetworks_core(var_mynetworks_style);
    return (result);
}

/* mynetworks_host - return patterns for "host" mynetworks style */

const char *mynetworks_host(void)
{
    static const char *result;

    if (result == 0)
    result = mynetworks_core(MYNETWORKS_STYLE_HOST);
    return (result);
}

#ifdef TEST
#include <inet_proto.h>

char   *var_inet_interfaces;
char   *var_mynetworks_style;

int     main(int argc, char **argv)
{
    INET_PROTO_INFO *proto_info;

    if (argc != 4)
    msg_fatal("usage: %s protocols mask_style interface_list (e.g. \"all subnet all\")",
          argv[0]);
    msg_verbose = 10;
    proto_info = inet_proto_init(argv[0], argv[1]);
    var_mynetworks_style = argv[2];
    var_inet_interfaces = argv[3];
    mynetworks();
    return (0);
}

#endif