smtpd_chat.c

[詳解]

/*++
/* NAME
/*  smtpd_chat 3
/* SUMMARY
/*  SMTP server request/response support
/* SYNOPSIS
/*  #include <smtpd.h>
/*  #include <smtpd_chat.h>
/*
/*  void    smtpd_chat_query(state)
/*  SMTPD_STATE *state;
/*
/*  void    smtpd_chat_reply(state, format, ...)
/*  SMTPD_STATE *state;
/*  char    *format;
/*
/*  void    smtpd_chat_notify(state)
/*  SMTPD_STATE *state;
/*
/*  void    smtpd_chat_reset(state)
/*  SMTPD_STATE *state;
/* DESCRIPTION
/*  This module implements SMTP server support for request/reply
/*  conversations, and maintains a limited SMTP transaction log.
/*
/*  smtpd_chat_query() receives a client request and appends a copy
/*  to the SMTP transaction log.
/*
/*  smtpd_chat_reply() formats a server reply, sends it to the
/*  client, and appends a copy to the SMTP transaction log.
/*  When soft_bounce is enabled, all 5xx (reject) responses are
/*  replaced by 4xx (try again). In case of a 421 reply the
/*  SMTPD_FLAG_HANGUP flag is set for orderly disconnect.
/*
/*  smtpd_chat_notify() sends a copy of the SMTP transaction log
/*  to the postmaster for review. The postmaster notice is sent only
/*  when delivery is possible immediately. It is an error to call
/*  smtpd_chat_notify() when no SMTP transaction log exists.
/*
/*  smtpd_chat_reset() resets the transaction log. This is
/*  typically done at the beginning of an SMTP session, or
/*  within a session to discard non-error information.
/* DIAGNOSTICS
/*  Panic: interface violations. Fatal errors: out of memory.
/*  internal protocol errors.
/* 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 <setjmp.h>
#include <unistd.h>
#include <time.h>
#include <stdlib.h>         /* 44BSD stdarg.h uses abort() */
#include <stdarg.h>

/* Utility library. */

#include <msg.h>
#include <argv.h>
#include <vstring.h>
#include <vstream.h>
#include <stringops.h>
#include <line_wrap.h>
#include <mymalloc.h>

/* Global library. */

#include <smtp_stream.h>
#include <record.h>
#include <rec_type.h>
#include <mail_proto.h>
#include <mail_params.h>
#include <mail_addr.h>
#include <post_mail.h>
#include <mail_error.h>
#include <smtp_reply_footer.h>

/* Application-specific. */

#include "smtpd.h"
#include "smtpd_expand.h"
#include "smtpd_chat.h"

#define STR vstring_str
#define LEN VSTRING_LEN

/* smtp_chat_reset - reset SMTP transaction log */

void    smtpd_chat_reset(SMTPD_STATE *state)
{
    if (state->history) {
    argv_free(state->history);
    state->history = 0;
    }
}

/* smtp_chat_append - append record to SMTP transaction log */

static void smtp_chat_append(SMTPD_STATE *state, char *direction,
                         const char *text)
{
    char   *line;

    if (state->notify_mask == 0)
    return;

    if (state->history == 0)
    state->history = argv_alloc(10);
    line = concatenate(direction, text, (char *) 0);
    argv_add(state->history, line, (char *) 0);
    myfree(line);
}

/* smtpd_chat_query - receive and record an SMTP request */

void    smtpd_chat_query(SMTPD_STATE *state)
{
    int     last_char;

    /*
     * We can't parse or store input that exceeds var_line_limit, so we skip
     * over it to avoid loss of synchronization.
     */
    last_char = smtp_get(state->buffer, state->client, var_line_limit,
             SMTP_GET_FLAG_SKIP);
    smtp_chat_append(state, "In:  ", STR(state->buffer));
    if (last_char != '\n')
    msg_warn("%s: request longer than %d: %.30s...",
         state->namaddr, var_line_limit,
         printable(STR(state->buffer), '?'));

    if (msg_verbose)
    msg_info("< %s: %s", state->namaddr, STR(state->buffer));
}

/* smtpd_chat_reply - format, send and record an SMTP response */

void    smtpd_chat_reply(SMTPD_STATE *state, const char *format,...)
{
    va_list ap;
    int     delay = 0;
    char   *cp;
    char   *next;
    char   *end;

    /*
     * Slow down clients that make errors. Sleep-on-anything slows down
     * clients that make an excessive number of errors within a session.
     */
    if (state->error_count >= var_smtpd_soft_erlim)
    sleep(delay = var_smtpd_err_sleep);

    va_start(ap, format);
    vstring_vsprintf(state->buffer, format, ap);
    va_end(ap);

    if (*var_smtpd_rej_footer
    && (*(cp = STR(state->buffer)) == '4' || *cp == '5'))
    smtp_reply_footer(state->buffer, 0, var_smtpd_rej_footer,
              STR(smtpd_expand_filter), smtpd_expand_lookup,
              (void *) state);

    /* All 5xx replies must have a 5.xx.xx detail code. */
    for (cp = STR(state->buffer), end = cp + strlen(STR(state->buffer));;) {
    if (var_soft_bounce) {
        if (cp[0] == '5') {
        cp[0] = '4';
        if (cp[4] == '5')
            cp[4] = '4';
        }
    }
    /* This is why we use strlen() above instead of VSTRING_LEN(). */
    if ((next = strstr(cp, "\r\n")) != 0) {
        *next = 0;
        if (next[2] != 0)
        cp[3] = '-';            /* contact footer kludge */
        else
        next = end;         /* strip trailing \r\n */
    } else {
        next = end;
    }
    smtp_chat_append(state, "Out: ", cp);

    if (msg_verbose)
        msg_info("> %s: %s", state->namaddr, cp);

    smtp_fputs(cp, next - cp, state->client);
    if (next < end)
        cp = next + 2;
    else
        break;
    }

    /*
     * Flush unsent output if no I/O happened for a while. This avoids
     * timeouts with pipelined SMTP sessions that have lots of server-side
     * delays (tarpit delays or DNS lookups for UCE restrictions).
     */
    if (delay || time((time_t *) 0) - vstream_ftime(state->client) > 10)
    vstream_fflush(state->client);

    /*
     * Abort immediately if the connection is broken.
     */
    if (vstream_ftimeout(state->client))
    vstream_longjmp(state->client, SMTP_ERR_TIME);
    if (vstream_ferror(state->client))
    vstream_longjmp(state->client, SMTP_ERR_EOF);

    /*
     * Orderly disconnect in case of 421 or 521 reply.
     */
    if (strncmp(STR(state->buffer), "421", 3) == 0
    || strncmp(STR(state->buffer), "521", 3) == 0)
    state->flags |= SMTPD_FLAG_HANGUP;
}

/* print_line - line_wrap callback */

static void print_line(const char *str, int len, int indent, void *context)
{
    VSTREAM *notice = (VSTREAM *) context;

    post_mail_fprintf(notice, " %*s%.*s", indent, "", len, str);
}

/* smtpd_chat_notify - notify postmaster */

void    smtpd_chat_notify(SMTPD_STATE *state)
{
    const char *myname = "smtpd_chat_notify";
    VSTREAM *notice;
    char  **cpp;

    /*
     * Sanity checks.
     */
    if (state->history == 0)
    msg_panic("%s: no conversation history", myname);
    if (msg_verbose)
    msg_info("%s: notify postmaster", myname);

    /*
     * Construct a message for the postmaster, explaining what this is all
     * about. This is junk mail: don't send it when the mail posting service
     * is unavailable, and use the double bounce sender address to prevent
     * mail bounce wars. Always prepend one space to message content that we
     * generate from untrusted data.
     */
#define NULL_TRACE_FLAGS    0
#define NO_QUEUE_ID     ((VSTRING *) 0)
#define LENGTH  78
#define INDENT  4

    notice = post_mail_fopen_nowait(mail_addr_double_bounce(),
                    var_error_rcpt,
                    MAIL_SRC_MASK_NOTIFY, NULL_TRACE_FLAGS,
                    SMTPUTF8_FLAG_NONE, NO_QUEUE_ID);
    if (notice == 0) {
    msg_warn("postmaster notify: %m");
    return;
    }
    post_mail_fprintf(notice, "From: %s (Mail Delivery System)",
              mail_addr_mail_daemon());
    post_mail_fprintf(notice, "To: %s (Postmaster)", var_error_rcpt);
    post_mail_fprintf(notice, "Subject: %s SMTP server: errors from %s",
              var_mail_name, state->namaddr);
    post_mail_fputs(notice, "");
    post_mail_fputs(notice, "Transcript of session follows.");
    post_mail_fputs(notice, "");
    argv_terminate(state->history);
    for (cpp = state->history->argv; *cpp; cpp++)
    line_wrap(printable(*cpp, '?'), LENGTH, INDENT, print_line,
          (void *) notice);
    post_mail_fputs(notice, "");
    if (state->reason)
    post_mail_fprintf(notice, "Session aborted, reason: %s", state->reason);
    post_mail_fputs(notice, "");
    post_mail_fprintf(notice, "For other details, see the local mail logfile");
    (void) post_mail_fclose(notice);
}