bounce_workaround.c

[詳解]

/*++
/* NAME
/*  bounce_workaround 3
/* SUMMARY
/*  Send non-delivery notification with sender override
/* SYNOPSIS
/*  #include "local.h"
/*
/*  int bounce_workaround(state)
/*  LOCAL_STATE state;
/* DESCRIPTION
/*  This module works around a limitation in the bounce daemon
/*  protocol, namely, the assumption that the envelope sender
/*  address in a queue file is the delivery status notification
/*  address for all recipients in that queue file. The assumption
/*  is not valid when the local(8) delivery agent overrides the
/*  envelope sender address by an owner- alias, for one or more
/*  recipients in the queue file.
/*
/*  Sender address override is a problem only when delivering
/*  to command or file, or when breaking a Delivered-To loop.
/*  The local(8) delivery agent saves normal recipients to a
/*  new queue file, together with the replacement envelope
/*  sender address; delivery then proceeds from that new queue
/*  file, and no workaround is needed.
/*
/*  The workaround sends one non-delivery notification for each
/*  failed delivery that has a replacement sender address.  The
/*  notifications are not aggregated, unlike notifications to
/*  non-replaced sender addresses. In practice, a local alias
/*  rarely has more than one file or command destination (if
/*  only because soft error handling is problematic).
/*
/*  Arguments:
/* .IP state
/*  The attributes that specify the message, recipient and more.
/*  Attributes describing alias, include or forward expansion.
/*  A table with the results from expanding aliases or lists.
/*  A table with delivered-to: addresses taken from the message.
/*  The non-delivery status must be either 4.X.X or 5.X.X.
/* DIAGNOSTICS
/*  Fatal errors: out of memory. The result is non-zero when
/*  the operation should be tried again. Warnings: malformed
/*  address.
/* BUGS
/*  The proper fix is to record in the bounce logfile an error
/*  return address for each individual recipient. This would
/*  eliminate the need for VERP-specific bounce protocol code,
/*  and would move complexity from the bounce client side to
/*  the bounce server side where it more likely belongs.
/* 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
/*--*/

/* System library. */

#include <sys_defs.h>
#include <strings.h>

/* Utility library. */

#include <msg.h>
#include <mymalloc.h>
#include <vstring.h>
#include <split_at.h>

/* Global library. */

#include <mail_params.h>
#include <strip_addr.h>
#include <stringops.h>
#include <bounce.h>
#include <defer.h>
#include <split_addr.h>
#include <canon_addr.h>

/* Application-specific. */

#include "local.h"

int     bounce_workaround(LOCAL_STATE state)
{
    const char *myname = "bounce_workaround";
    VSTRING *canon_owner = 0;
    int     rcpt_stat;

    /*
     * Look up the substitute sender address.
     */
    if (var_ownreq_special) {
    char   *stripped_recipient;
    char   *owner_alias;
    const char *owner_expansion;

#define FIND_OWNER(lhs, rhs, addr) { \
    lhs = concatenate("owner-", addr, (char *) 0); \
    (void) split_at_right(lhs, '@'); \
    rhs = maps_find(alias_maps, lhs, DICT_FLAG_NONE); \
    }

    FIND_OWNER(owner_alias, owner_expansion, state.msg_attr.rcpt.address);
    if (alias_maps->error == 0 && owner_expansion == 0
        && (stripped_recipient = strip_addr(state.msg_attr.rcpt.address,
                        (char **) 0,
                        var_rcpt_delim)) != 0) {
        myfree(owner_alias);
        FIND_OWNER(owner_alias, owner_expansion, stripped_recipient);
        myfree(stripped_recipient);
    }
    if (alias_maps->error == 0 && owner_expansion != 0) {
        canon_owner = canon_addr_internal(vstring_alloc(10),
                          var_exp_own_alias ?
                          owner_expansion : owner_alias);
        SET_OWNER_ATTR(state.msg_attr, STR(canon_owner), state.level);
    }
    myfree(owner_alias);
    if (alias_maps->error != 0) {
        /* At this point, canon_owner == 0. */
        dsb_simple(state.msg_attr.why, "4.3.0",
               "alias database unavailable");
        return (defer_append(BOUNCE_FLAGS(state.request),
                 BOUNCE_ATTR(state.msg_attr)));
    }
    }

    /*
     * Send a delivery status notification with a single recipient to the
     * substitute sender address, before completion of the delivery request.
     */
    if (canon_owner) {
    rcpt_stat =
        (STR(state.msg_attr.why->status)[0] == '4' ?
         defer_one : bounce_one)
        (BOUNCE_FLAGS(state.request),
         BOUNCE_ONE_ATTR(state.msg_attr));
    vstring_free(canon_owner);
    }

    /*
     * Send a regular delivery status notification, after completion of the
     * delivery request.
     */
    else {
    rcpt_stat =
        (STR(state.msg_attr.why->status)[0] == '4' ?
         defer_append : bounce_append)
        (BOUNCE_FLAGS(state.request),
         BOUNCE_ATTR(state.msg_attr));
    }
    return (rcpt_stat);
}