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| -rw-r--r-- | sink.c | 626 |
1 files changed, 626 insertions, 0 deletions
@@ -0,0 +1,626 @@ +/* + * sink.c -- forwarding/delivery support for fetchmail + * + * The interface of this module (open_sink(), stuff_line(), close_sink(), + * release_sink()) seals off the delivery logic from the protocol machine, + * so the latter won't have to care whether it's shipping to an SMTP + * listener daemon or an MDA pipe. + * + * Copyright 1998 by Eric S. Raymond + * For license terms, see the file COPYING in this directory. + */ + +#include "config.h" +#include <stdio.h> +#include <errno.h> +#include <string.h> +#include <signal.h> +#ifdef HAVE_MEMORY_H +#include <memory.h> +#endif /* HAVE_MEMORY_H */ +#if defined(STDC_HEADERS) +#include <stdlib.h> +#endif +#if defined(HAVE_UNISTD_H) +#include <unistd.h> +#endif +#if defined(HAVE_ALLOCA_H) +#include <alloca.h> +#else +#ifdef _AIX + #pragma alloca +#endif +#endif + +#include "fetchmail.h" +#include "socket.h" +#include "smtp.h" + +/* BSD portability hack...I know, this is an ugly place to put it */ +#if !defined(SIGCHLD) && defined(SIGCLD) +#define SIGCHLD SIGCLD +#endif + +#if INET6 +#define SMTP_PORT "smtp" /* standard SMTP service port */ +#else /* INET6 */ +#define SMTP_PORT 25 /* standard SMTP service port */ +#endif /* INET6 */ + +static int smtp_open(struct query *ctl) +/* try to open a socket to the appropriate SMTP server for this query */ +{ + /* maybe it's time to close the socket in order to force delivery */ + if (NUM_NONZERO(ctl->batchlimit) && (ctl->smtp_socket != -1) && batchcount++ == ctl->batchlimit) + { + close(ctl->smtp_socket); + ctl->smtp_socket = -1; + batchcount = 0; + } + + /* if no socket to any SMTP host is already set up, try to open one */ + if (ctl->smtp_socket == -1) + { + /* + * RFC 1123 requires that the domain name in HELO address is a + * "valid principal domain name" for the client host. If we're + * running in invisible mode, violate this with malice + * aforethought in order to make the Received headers and + * logging look right. + * + * In fact this code relies on the RFC1123 requirement that the + * SMTP listener must accept messages even if verification of the + * HELO name fails (RFC1123 section 5.2.5, paragraph 2). + * + * How we compute the true mailhost name to pass to the + * listener doesn't affect behavior on RFC1123- violating + * listeners that check for name match; we're going to lose + * on those anyway because we can never give them a name + * that matches the local machine fetchmail is running on. + * What it will affect is the listener's logging. + */ + struct idlist *idp; + char *id_me = run.invisible ? ctl->server.truename : fetchmailhost; + int oldphase = phase; + + errno = 0; + + /* + * Run down the SMTP hunt list looking for a server that's up. + * Use both explicit hunt entries (value TRUE) and implicit + * (default) ones (value FALSE). + */ + oldphase = phase; + phase = LISTENER_WAIT; + + set_timeout(ctl->server.timeout); + for (idp = ctl->smtphunt; idp; idp = idp->next) + { + char *cp, *parsed_host = alloca(strlen(idp->id) + 1); +#ifdef INET6 + char *portnum = SMTP_PORT; +#else + int portnum = SMTP_PORT; +#endif /* INET6 */ + + ctl->smtphost = idp->id; /* remember last host tried. */ + + strcpy(parsed_host, idp->id); + if ((cp = strrchr(parsed_host, '/'))) + { + *cp++ = 0; +#ifdef INET6 + portnum = cp; +#else + portnum = atoi(cp); +#endif /* INET6 */ + } + + if ((ctl->smtp_socket = SockOpen(parsed_host,portnum,NULL)) == -1) + continue; + + /* first, probe for ESMTP */ + if (SMTP_ok(ctl->smtp_socket) == SM_OK && + SMTP_ehlo(ctl->smtp_socket, id_me, + &ctl->server.esmtp_options) == SM_OK) + break; /* success */ + + /* + * RFC 1869 warns that some listeners hang up on a failed EHLO, + * so it's safest not to assume the socket will still be good. + */ + SockClose(ctl->smtp_socket); + ctl->smtp_socket = -1; + + /* if opening for ESMTP failed, try SMTP */ + if ((ctl->smtp_socket = SockOpen(parsed_host,portnum,NULL)) == -1) + continue; + + if (SMTP_ok(ctl->smtp_socket) == SM_OK && + SMTP_helo(ctl->smtp_socket, id_me) == SM_OK) + break; /* success */ + + SockClose(ctl->smtp_socket); + ctl->smtp_socket = -1; + } + set_timeout(0); + phase = oldphase; + } + + /* + * RFC 1123 requires that the domain name part of the + * RCPT TO address be "canonicalized", that is a FQDN + * or MX but not a CNAME. Some listeners (like exim) + * enforce this. Now that we have the actual hostname, + * compute what we should canonicalize with. + */ + ctl->destaddr = ctl->smtpaddress ? ctl->smtpaddress : ( ctl->smtphost ? ctl->smtphost : "localhost"); + + if (outlevel >= O_VERBOSE && ctl->smtp_socket != -1) + error(0, 0, "forwarding to %s", ctl->smtphost); + + return(ctl->smtp_socket); +} + +/* these are shared by open_sink and stuffline */ +static FILE *sinkfp; +static RETSIGTYPE (*sigchld)(); + +int stuffline(struct query *ctl, char *buf) +/* ship a line to the given control block's output sink (SMTP server or MDA) */ +{ + int n, oldphase; + char *last; + + /* The line may contain NUL characters. Find the last char to use + * -- the real line termination is the sequence "\n\0". + */ + last = buf; + while ((last += strlen(last)) && (last[-1] != '\n')) + last++; + + /* fix message lines that have only \n termination (for qmail) */ + if (ctl->forcecr) + { + if (last - 1 == buf || last[-2] != '\r') + { + last[-1] = '\r'; + *last++ = '\n'; + *last = '\0'; + } + } + + oldphase = phase; + phase = FORWARDING_WAIT; + + /* + * SMTP byte-stuffing. We only do this if the protocol does *not* + * use .<CR><LF> as EOM. If it does, the server will already have + * decorated any . lines it sends back up. + */ + if (*buf == '.') + if (ctl->server.base_protocol->delimited) /* server has already byte-stuffed */ + { + if (ctl->mda) + ++buf; + else + /* writing to SMTP, leave the byte-stuffing in place */; + } + else /* if (!protocol->delimited) -- not byte-stuffed already */ + { + if (!ctl->mda) + SockWrite(ctl->smtp_socket, buf, 1); /* byte-stuff it */ + else + /* leave it alone */; + } + + /* we may need to strip carriage returns */ + if (ctl->stripcr) + { + char *sp, *tp; + + for (sp = tp = buf; sp < last; sp++) + if (*sp != '\r') + *tp++ = *sp; + *tp = '\0'; + last = tp; + } + + n = 0; + if (ctl->mda) + n = fwrite(buf, 1, last - buf, sinkfp); + else if (ctl->smtp_socket != -1) + n = SockWrite(ctl->smtp_socket, buf, last - buf); + + phase = oldphase; + + return(n); +} + +static void sanitize(char *s) +/* replace unsafe shellchars by an _ */ +{ + static char *ok_chars = " 1234567890!@%-_=+:,./abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"; + char *cp; + + for (cp = s; *(cp += strspn(cp, ok_chars)); /* NO INCREMENT */) + *cp = '_'; +} + +int open_sink(struct query *ctl, + char *return_path, + struct idlist *xmit_names, + long reallen, + int *good_addresses, int *bad_addresses) +/* set up sinkfp to be an input sink we can ship a message to */ +{ + struct idlist *idp; + + *bad_addresses = *good_addresses = 0; + + if (ctl->mda) /* we have a declared MDA */ + { + int length = 0, fromlen = 0, nameslen = 0; + char *names = NULL, *before, *after, *from = NULL; + + ctl->destaddr = "localhost"; + + for (idp = xmit_names; idp; idp = idp->next) + if (idp->val.status.mark == XMIT_ACCEPT) + (*good_addresses)++; + + length = strlen(ctl->mda); + before = xstrdup(ctl->mda); + + /* get user addresses for %T (or %s for backward compatibility) */ + if (strstr(before, "%s") || strstr(before, "%T")) + { + /* + * We go through this in order to be able to handle very + * long lists of users and (re)implement %s. + */ + nameslen = 0; + for (idp = xmit_names; idp; idp = idp->next) + if (idp->val.status.mark == XMIT_ACCEPT) + nameslen += (strlen(idp->id) + 1); /* string + ' ' */ + if (*good_addresses = 0) + nameslen = strlen(run.postmaster); + + names = (char *)xmalloc(nameslen + 1); /* account for '\0' */ + if (*good_addresses == 0) + strcpy(names, run.postmaster); + else + { + names[0] = '\0'; + for (idp = xmit_names; idp; idp = idp->next) + if (idp->val.status.mark == XMIT_ACCEPT) + { + strcat(names, idp->id); + strcat(names, " "); + } + names[--nameslen] = '\0'; /* chop trailing space */ + } + + /* sanitize names in order to contain only harmless shell chars */ + sanitize(names); + } + + /* get From address for %F */ + if (strstr(before, "%F")) + { + from = xstrdup(return_path); + + /* sanitize from in order to contain *only* harmless shell chars */ + sanitize(from); + + fromlen = strlen(from); + } + + /* do we have to build an mda string? */ + if (names || from) + { + char *sp, *dp; + + /* find length of resulting mda string */ + sp = before; + while (sp = strstr(sp, "%s")) { + length += nameslen - 2; /* subtract %s */ + sp += 2; + } + sp = before; + while (sp = strstr(sp, "%T")) { + length += nameslen - 2; /* subtract %T */ + sp += 2; + } + sp = before; + while (sp = strstr(sp, "%F")) { + length += fromlen - 2; /* subtract %F */ + sp += 2; + } + + after = xmalloc(length + 1); + + /* copy mda source string to after, while expanding %[sTF] */ + for (dp = after, sp = before; *dp = *sp; dp++, sp++) { + if (sp[0] != '%') continue; + + /* need to expand? BTW, no here overflow, because in + ** the worst case (end of string) sp[1] == '\0' */ + if (sp[1] == 's' || sp[1] == 'T') { + strcpy(dp, names); + dp += nameslen; + sp++; /* position sp over [sT] */ + dp--; /* adjust dp */ + } else if (sp[1] == 'F') { + strcpy(dp, from); + dp += fromlen; + sp++; /* position sp over F */ + dp--; /* adjust dp */ + } + } + + if (names) { + free(names); + names = NULL; + } + if (from) { + free(from); + from = NULL; + } + + free(before); + + before = after; + } + + + if (outlevel == O_VERBOSE) + error(0, 0, "about to deliver with: %s", before); + +#ifdef HAVE_SETEUID + /* + * Arrange to run with user's permissions if we're root. + * This will initialize the ownership of any files the + * MDA creates properly. (The seteuid call is available + * under all BSDs and Linux) + */ + seteuid(ctl->uid); +#endif /* HAVE_SETEUID */ + + sinkfp = popen(before, "w"); + free(before); + before = NULL; + +#ifdef HAVE_SETEUID + /* this will fail quietly if we didn't start as root */ + seteuid(0); +#endif /* HAVE_SETEUID */ + + if (!sinkfp) + { + error(0, 0, "MDA open failed"); + return(PS_IOERR); + } + + sigchld = signal(SIGCHLD, SIG_DFL); + } + else + { + char *ap, options[MSGBUFSIZE], addr[128]; + + /* build a connection to the SMTP listener */ + if ((smtp_open(ctl) == -1)) + { + error(0, errno, "SMTP connect to %s failed", + ctl->smtphost ? ctl->smtphost : "localhost"); + return(PS_SMTP); + } + + /* + * Compute ESMTP options. + */ + options[0] = '\0'; + if (ctl->server.esmtp_options & ESMTP_8BITMIME) { + if (ctl->pass8bits || (ctl->mimemsg & MSG_IS_8BIT)) + strcpy(options, " BODY=8BITMIME"); + else if (ctl->mimemsg & MSG_IS_7BIT) + strcpy(options, " BODY=7BIT"); + } + + if ((ctl->server.esmtp_options & ESMTP_SIZE) && reallen > 0) + sprintf(options + strlen(options), " SIZE=%ld", reallen); + + /* + * Try to get the SMTP listener to take the Return-Path + * address as MAIL FROM . If it won't, fall back on the + * calling-user ID. This won't affect replies, which use the + * header From address anyway. + * + * RFC 1123 requires that the domain name part of the + * MAIL FROM address be "canonicalized", that is a + * FQDN or MX but not a CNAME. We'll assume the From + * header is already in this form here (it certainly + * is if rewrite is on). RFC 1123 is silent on whether + * a nonexistent hostname part is considered canonical. + * + * This is a potential problem if the MTAs further upstream + * didn't pass canonicalized From/Return-Path lines, *and* the + * local SMTP listener insists on them. + * + * None of these error conditions generates bouncemail. Comments + * below explain for each case why this is so. + */ + ap = (return_path[0]) ? return_path : user; + if (SMTP_from(ctl->smtp_socket, ap, options) != SM_OK) + { + int smtperr = atoi(smtp_response); + + if (str_find(&ctl->antispam, smtperr)) + { + /* + * SMTP listener explicitly refuses to deliver mail + * coming from this address, probably due to an + * anti-spam domain exclusion. Respect this. Don't + * try to ship the message, and don't prevent it from + * being deleted. Typical values: + * + * 501 = exim's old antispam response + * 550 = exim's new antispam response (temporary) + * 553 = sendmail 8.8.7's generic REJECT + * 571 = sendmail's "unsolicited email refused" + * + * We don't send bouncemail on antispam failures because + * we don't want the scumbags to know the address is even + * valid. + */ + SMTP_rset(ctl->smtp_socket); /* required by RFC1870 */ + return(PS_REFUSED); + } + + /* + * Suppress error message only if the response specifically + * meant `excluded for policy reasons'. We *should* see + * an error when the return code is less specific. + */ + if (smtperr >= 400) + error(0, -1, "SMTP error: %s", smtp_response); + + switch (smtperr) + { + case 452: /* insufficient system storage */ + /* + * Temporary out-of-queue-space condition on the + * ESMTP server. Don't try to ship the message, + * and suppress deletion so it can be retried on + * a future retrieval cycle. + * + * Bouncemail *might* be appropriate here as a delay + * notification. But it's not really necessary because + * this is not an actual failure, we're very likely to be + * able to recover on the next cycle. + */ + SMTP_rset(ctl->smtp_socket); /* required by RFC1870 */ + return(PS_TRANSIENT); + + case 552: /* message exceeds fixed maximum message size */ + case 553: /* invalid sending domain */ + /* + * Permanent no-go condition on the + * ESMTP server. Don't try to ship the message, + * and allow it to be deleted. + * + * Bouncemail would be appropriate for 552, but in these + * latter days 553 usually means a spammer is trying to + * cover his tracks. We'd rather deny the scumbags any + * feedback that the address is valid. + */ + SMTP_rset(ctl->smtp_socket); /* required by RFC1870 */ + return(PS_REFUSED); + + default: /* retry with postmaster's address */ + if (SMTP_from(ctl->smtp_socket,run.postmaster,options)!=SM_OK) + { + error(0, -1, "SMTP error: %s", smtp_response); + return(PS_SMTP); /* should never happen */ + } + } + } + + /* + * Now list the recipient addressees + */ + for (idp = xmit_names; idp; idp = idp->next) + if (idp->val.status.mark == XMIT_ACCEPT) + { + if (strchr(idp->id, '@')) + strcpy(addr, idp->id); + else +#ifdef HAVE_SNPRINTF + snprintf(addr, sizeof(addr)-1, "%s@%s", idp->id, ctl->destaddr); +#else + sprintf(addr, "%s@%s", idp->id, ctl->destaddr); +#endif /* HAVE_SNPRINTF */ + + if (SMTP_rcpt(ctl->smtp_socket, addr) == SM_OK) + (*good_addresses)++; + else + { + (*bad_addresses)++; + idp->val.status.mark = XMIT_ANTISPAM; + error(0, 0, + "SMTP listener doesn't like recipient address `%s'", + addr); + } + } + if (!(*good_addresses)) + { +#ifdef HAVE_SNPRINTF + snprintf(addr, sizeof(addr)-1, "%s@%s", run.postmaster, ctl->destaddr); +#else + sprintf(addr, "%s@%s", run.postmaster, ctl->destaddr); +#endif /* HAVE_SNPRINTF */ + + if (SMTP_rcpt(ctl->smtp_socket, addr) != SM_OK) + { + error(0, 0, "can't even send to %s!", run.postmaster); + return(PS_SMTP); + } + } + + /* tell it we're ready to send data */ + SMTP_data(ctl->smtp_socket); + } + + return(PS_SUCCESS); +} + +void release_sink(struct query *ctl) +/* release the per-message output sink, whether it's a pipe or SMTP socket */ +{ + if (ctl->mda) + { + if (sinkfp) + { + pclose(sinkfp); + sinkfp = (FILE *)NULL; + } + signal(SIGCHLD, sigchld); + } +} + +int close_sink(struct query *ctl, flag forward) +/* perform end-of-message actions on the current output sink */ +{ + if (ctl->mda) + { + int rc; + + /* close the delivery pipe, we'll reopen before next message */ + if (sinkfp) + { + rc = pclose(sinkfp); + sinkfp = (FILE *)NULL; + } + else + rc = 0; + signal(SIGCHLD, sigchld); + if (rc) + { + error(0, -1, "MDA exited abnormally or returned nonzero status"); + return(FALSE); + } + } + else if (forward) + { + /* write message terminator */ + if (SMTP_eom(ctl->smtp_socket) != SM_OK) + { + error(0, -1, "SMTP listener refused delivery"); + return(FALSE); + } + } + + return(TRUE); +} + +/* sink.c ends here */ |