Adding upstream version 3.4.23.upstream/3.4.23upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 828 insertions, 0 deletions

diff --git a/src/trivial-rewrite/resolve.c b/src/trivial-rewrite/resolve.c
new file mode 100644
index 0000000..4e9ea2a
--- /dev/null
+++ b/src/trivial-rewrite/resolve.c
@@ -0,0 +1,828 @@
+/*++
+/* NAME
+/*	resolve 3
+/* SUMMARY
+/*	mail address resolver
+/* SYNOPSIS
+/*	#include "trivial-rewrite.h"
+/*
+/*	void	resolve_init(void)
+/*
+/*	int	resolve_class(domain)
+/*	const char *domain;
+/*
+/*	void	resolve_proto(context, stream)
+/*	RES_CONTEXT *context;
+/*	VSTREAM	*stream;
+/* DESCRIPTION
+/*	This module implements the trivial address resolving engine.
+/*	It distinguishes between local and remote mail, and optionally
+/*	consults one or more transport tables that map a destination
+/*	to a transport, nexthop pair.
+/*
+/*	resolve_init() initializes data structures that are private
+/*	to this module. It should be called once before using the
+/*	actual resolver routines.
+/*
+/*	resolve_class() returns the address class for the specified
+/*	domain, or -1 in case of error.
+/*
+/*	resolve_proto() implements the client-server protocol:
+/*	read one address in FQDN form, reply with a (transport,
+/*	nexthop, internalized recipient) triple.
+/* STANDARDS
+/* DIAGNOSTICS
+/*	Problems and transactions are logged to \fBsyslogd\fR(8)
+/*	or \fBpostlogd\fR(8).
+/* BUGS
+/* SEE ALSO
+/* 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
+/*
+/*	Wietse Venema
+/*	Google, Inc.
+/*	111 8th Avenue
+/*	New York, NY 10011, USA
+/*--*/
+
+/* System library. */
+
+#include <sys_defs.h>
+#include <stdlib.h>
+#include <string.h>
+
+#ifdef STRCASECMP_IN_STRINGS_H
+#include <strings.h>
+#endif
+
+/* Utility library. */
+
+#include <msg.h>
+#include <vstring.h>
+#include <vstream.h>
+#include <vstring_vstream.h>
+#include <split_at.h>
+#include <valid_utf8_hostname.h>
+#include <stringops.h>
+#include <mymalloc.h>
+
+/* Global library. */
+
+#include <mail_params.h>
+#include <mail_proto.h>
+#include <resolve_local.h>
+#include <mail_conf.h>
+#include <quote_822_local.h>
+#include <tok822.h>
+#include <domain_list.h>
+#include <string_list.h>
+#include <match_parent_style.h>
+#include <maps.h>
+#include <mail_addr_find.h>
+#include <valid_mailhost_addr.h>
+
+/* Application-specific. */
+
+#include "trivial-rewrite.h"
+#include "transport.h"
+
+ /*
+  * The job of the address resolver is to map one recipient address to a
+  * triple of (channel, nexthop, recipient). The channel is the name of the
+  * delivery service specified in master.cf, the nexthop is (usually) a
+  * description of the next host to deliver to, and recipient is the final
+  * recipient address. The latter may differ from the input address as the
+  * result of stripping multiple layers of sender-specified routing.
+  * 
+  * Addresses are resolved by their domain name. Known domain names are
+  * categorized into classes: local, virtual alias, virtual mailbox, relay,
+  * and everything else. Finding the address domain class is a matter of
+  * table lookups.
+  * 
+  * Different address domain classes generally use different delivery channels,
+  * and may use class dependent ways to arrive at the corresponding nexthop
+  * information. With classes that do final delivery, the nexthop is
+  * typically the local machine hostname.
+  * 
+  * The transport lookup table provides a means to override the domain class
+  * channel and/or nexhop information for specific recipients or for entire
+  * domain hierarchies.
+  * 
+  * This works well in the general case. The only bug in this approach is that
+  * the structure of the nexthop information is transport dependent.
+  * Typically, the nexthop specifies a hostname, hostname + TCP Port, or the
+  * pathname of a UNIX-domain socket. However, with the error transport the
+  * nexthop field contains free text with the reason for non-delivery.
+  * 
+  * Therefore, a transport map entry that overrides the channel but not the
+  * nexthop information (or vice versa) may produce surprising results. In
+  * particular, the free text nexthop information for the error transport is
+  * likely to confuse regular delivery agents; and conversely, a hostname or
+  * socket pathname is not an adequate text as reason for non-delivery.
+  * 
+  * In the code below, rcpt_domain specifies the domain name that we will use
+  * when the transport table specifies a non-default channel but no nexthop
+  * information (we use a generic text when that non-default channel is the
+  * error transport).
+  */
+
+#define STR	vstring_str
+#define LEN	VSTRING_LEN
+
+ /*
+  * Some of the lists that define the address domain classes.
+  */
+static DOMAIN_LIST *relay_domains;
+static STRING_LIST *virt_alias_doms;
+static STRING_LIST *virt_mailbox_doms;
+
+static MAPS *relocated_maps;
+
+/* resolve_class - determine domain address class */
+
+int     resolve_class(const char *domain)
+{
+    int     ret;
+
+    /*
+     * Same order as in resolve_addr().
+     */
+    if ((ret = resolve_local(domain)) != 0)
+	return (ret > 0 ? RESOLVE_CLASS_LOCAL : -1);
+    if (virt_alias_doms) {
+	if (string_list_match(virt_alias_doms, domain))
+	    return (RESOLVE_CLASS_ALIAS);
+	if (virt_alias_doms->error)
+	    return (-1);
+    }
+    if (virt_mailbox_doms) {
+	if (string_list_match(virt_mailbox_doms, domain))
+	    return (RESOLVE_CLASS_VIRTUAL);
+	if (virt_mailbox_doms->error)
+	    return (-1);
+    }
+    if (relay_domains) {
+	if (string_list_match(relay_domains, domain))
+	    return (RESOLVE_CLASS_RELAY);
+	if (relay_domains->error)
+	    return (-1);
+    }
+    return (RESOLVE_CLASS_DEFAULT);
+}
+
+/* resolve_addr - resolve address according to rule set */
+
+static void resolve_addr(RES_CONTEXT *rp, char *sender, char *addr,
+			         VSTRING *channel, VSTRING *nexthop,
+			         VSTRING *nextrcpt, int *flags)
+{
+    const char *myname = "resolve_addr";
+    VSTRING *addr_buf = vstring_alloc(100);
+    TOK822 *tree = 0;
+    TOK822 *saved_domain = 0;
+    TOK822 *domain = 0;
+    char   *destination;
+    const char *blame = 0;
+    const char *rcpt_domain;
+    ssize_t addr_len;
+    ssize_t loop_count;
+    ssize_t loop_max;
+    char   *local;
+    char   *oper;
+    char   *junk;
+    const char *relay;
+    const char *xport;
+    const char *sender_key;
+    int     rc;
+
+    *flags = 0;
+    vstring_strcpy(channel, "CHANNEL NOT UPDATED");
+    vstring_strcpy(nexthop, "NEXTHOP NOT UPDATED");
+    vstring_strcpy(nextrcpt, "NEXTRCPT NOT UPDATED");
+
+    /*
+     * The address is in internalized (unquoted) form.
+     * 
+     * In an ideal world we would parse the externalized address form as given
+     * to us by the sender.
+     * 
+     * However, in the real world we have to look for routing characters like
+     * %@! in the address local-part, even when that information is quoted
+     * due to the presence of special characters or whitespace. Although
+     * technically incorrect, this is needed to stop user@domain@domain relay
+     * attempts when forwarding mail to a Sendmail MX host.
+     * 
+     * This suggests that we parse the address in internalized (unquoted) form.
+     * Unfortunately, if we do that, the unparser generates incorrect white
+     * space between adjacent non-operator tokens. Example: ``first last''
+     * needs white space, but ``stuff[stuff]'' does not. This is is not a
+     * problem when unparsing the result from parsing externalized forms,
+     * because the parser/unparser were designed for valid externalized forms
+     * where ``stuff[stuff]'' does not happen.
+     * 
+     * As a workaround we start with the quoted form and then dequote the
+     * local-part only where needed. This will do the right thing in most
+     * (but not all) cases.
+     */
+    addr_len = strlen(addr);
+    quote_822_local(addr_buf, addr);
+    tree = tok822_scan_addr(vstring_str(addr_buf));
+
+    /*
+     * The optimizer will eliminate tests that always fail, and will replace
+     * multiple expansions of this macro by a GOTO to a single instance.
+     */
+#define FREE_MEMORY_AND_RETURN { \
+	if (saved_domain) \
+	    tok822_free_tree(saved_domain); \
+	if(tree) \
+	    tok822_free_tree(tree); \
+	if (addr_buf) \
+	    vstring_free(addr_buf); \
+	return; \
+    }
+
+    /*
+     * Preliminary resolver: strip off all instances of the local domain.
+     * Terminate when no destination domain is left over, or when the
+     * destination domain is remote.
+     * 
+     * XXX To whom it may concern. If you change the resolver loop below, or
+     * quote_822_local.c, or tok822_parse.c, be sure to re-run the tests
+     * under "make resolve_clnt_test" in the global directory.
+     */
+#define RESOLVE_LOCAL(domain) \
+    resolve_local(STR(tok822_internalize(addr_buf, domain, TOK822_STR_DEFL)))
+
+    for (loop_count = 0, loop_max = addr_len + 100; /* void */ ; loop_count++) {
+
+	/*
+	 * XXX Should never happen, but if this happens with some
+	 * pathological address, then that is not sufficient reason to
+	 * disrupt the operation of an MTA.
+	 */
+	if (loop_count > loop_max) {
+	    msg_warn("resolve_addr: <%s>: giving up after %ld iterations",
+		     addr, (long) loop_count);
+	    *flags |= RESOLVE_FLAG_FAIL;
+	    FREE_MEMORY_AND_RETURN;
+	    break;
+	}
+
+	/*
+	 * Strip trailing dot at end of domain, but not dot-dot or at-dot.
+	 * This merely makes diagnostics more accurate by leaving bogus
+	 * addresses alone.
+	 */
+	if (tree->tail
+	    && tree->tail->type == '.'
+	    && tok822_rfind_type(tree->tail, '@') != 0
+	    && tree->tail->prev->type != '.'
+	    && tree->tail->prev->type != '@')
+	    tok822_free_tree(tok822_sub_keep_before(tree, tree->tail));
+
+	/*
+	 * Strip trailing @.
+	 */
+	if (var_resolve_nulldom
+	    && tree->tail
+	    && tree->tail->type == '@')
+	    tok822_free_tree(tok822_sub_keep_before(tree, tree->tail));
+
+	/*
+	 * Strip (and save) @domain if local.
+	 * 
+	 * Grr. resolve_local() table lookups may fail. It may be OK for local
+	 * file lookup code to abort upon failure, but with network-based
+	 * tables it is preferable to return an error indication to the
+	 * requestor.
+	 */
+	if ((domain = tok822_rfind_type(tree->tail, '@')) != 0) {
+	    if (domain->next && (rc = RESOLVE_LOCAL(domain->next)) <= 0) {
+		if (rc < 0) {
+		    *flags |= RESOLVE_FLAG_FAIL;
+		    FREE_MEMORY_AND_RETURN;
+		}
+		break;
+	    }
+	    tok822_sub_keep_before(tree, domain);
+	    if (saved_domain)
+		tok822_free_tree(saved_domain);
+	    saved_domain = domain;
+	    domain = 0;				/* safety for future change */
+	}
+
+	/*
+	 * After stripping the local domain, if any, replace foo%bar by
+	 * foo@bar, site!user by user@site, rewrite to canonical form, and
+	 * retry.
+	 */
+	if (tok822_rfind_type(tree->tail, '@')
+	    || (var_swap_bangpath && tok822_rfind_type(tree->tail, '!'))
+	    || (var_percent_hack && tok822_rfind_type(tree->tail, '%'))) {
+	    rewrite_tree(&local_context, tree);
+	    continue;
+	}
+
+	/*
+	 * If the local-part is a quoted string, crack it open when we're
+	 * permitted to do so and look for routing operators. This is
+	 * technically incorrect, but is needed to stop relaying problems.
+	 * 
+	 * XXX Do another feeble attempt to keep local-part info quoted.
+	 */
+	if (var_resolve_dequoted
+	    && tree->head && tree->head == tree->tail
+	    && tree->head->type == TOK822_QSTRING
+	    && ((oper = strrchr(local = STR(tree->head->vstr), '@')) != 0
+		|| (var_percent_hack && (oper = strrchr(local, '%')) != 0)
+	     || (var_swap_bangpath && (oper = strrchr(local, '!')) != 0))) {
+	    if (*oper == '%')
+		*oper = '@';
+	    tok822_internalize(addr_buf, tree->head, TOK822_STR_DEFL);
+	    if (*oper == '@') {
+		junk = mystrdup(STR(addr_buf));
+		quote_822_local(addr_buf, junk);
+		myfree(junk);
+	    }
+	    tok822_free(tree->head);
+	    tree->head = tok822_scan(STR(addr_buf), &tree->tail);
+	    rewrite_tree(&local_context, tree);
+	    continue;
+	}
+
+	/*
+	 * An empty local-part or an empty quoted string local-part becomes
+	 * the local MAILER-DAEMON, for consistency with our own From:
+	 * message headers.
+	 */
+	if (tree->head && tree->head == tree->tail
+	    && tree->head->type == TOK822_QSTRING
+	    && VSTRING_LEN(tree->head->vstr) == 0) {
+	    tok822_free(tree->head);
+	    tree->head = 0;
+	}
+	/* XXX Re-resolve the surrogate, in case already in user@domain form. */
+	if (tree->head == 0) {
+	    tree->head = tok822_scan(var_empty_addr, &tree->tail);
+	    continue;
+	}
+	/* XXX Re-resolve with @$myhostname for backwards compatibility. */
+	if (domain == 0 && saved_domain == 0) {
+	    tok822_sub_append(tree, tok822_alloc('@', (char *) 0));
+	    tok822_sub_append(tree, tok822_scan(var_myhostname, (TOK822 **) 0));
+	    continue;
+	}
+
+	/*
+	 * We're done. There are no domains left to strip off the address,
+	 * and all null local-part information is sanitized.
+	 */
+	domain = 0;
+	break;
+    }
+
+    vstring_free(addr_buf);
+    addr_buf = 0;
+
+    /*
+     * Make sure the resolved envelope recipient has the user@domain form. If
+     * no domain was specified in the address, assume the local machine. See
+     * above for what happens with an empty address.
+     */
+    if (domain == 0) {
+	if (saved_domain) {
+	    tok822_sub_append(tree, saved_domain);
+	    saved_domain = 0;
+	} else {
+	    tok822_sub_append(tree, tok822_alloc('@', (char *) 0));
+	    tok822_sub_append(tree, tok822_scan(var_myhostname, (TOK822 **) 0));
+	}
+    }
+
+    /*
+     * Transform the recipient address back to internal form.
+     * 
+     * XXX This may produce incorrect results if we cracked open a quoted
+     * local-part with routing operators; see discussion above at the top of
+     * the big loop.
+     * 
+     * XXX We explicitly disallow domain names in bare network address form. A
+     * network address destination should be formatted according to RFC 2821:
+     * it should be enclosed in [], and an IPv6 address should have an IPv6:
+     * prefix.
+     */
+    tok822_internalize(nextrcpt, tree, TOK822_STR_DEFL);
+    rcpt_domain = strrchr(STR(nextrcpt), '@') + 1;
+    if (rcpt_domain == (char *) 1)
+	msg_panic("no @ in address: \"%s\"", STR(nextrcpt));
+    if (*rcpt_domain == '[') {
+	if (!valid_mailhost_literal(rcpt_domain, DONT_GRIPE))
+	    *flags |= RESOLVE_FLAG_ERROR;
+    } else if (var_smtputf8_enable
+	       && valid_utf8_string(STR(nextrcpt), LEN(nextrcpt)) == 0) {
+	*flags |= RESOLVE_FLAG_ERROR;
+    } else if (!valid_utf8_hostname(var_smtputf8_enable, rcpt_domain,
+				    DONT_GRIPE)) {
+	if (var_resolve_num_dom && valid_hostaddr(rcpt_domain, DONT_GRIPE)) {
+	    vstring_insert(nextrcpt, rcpt_domain - STR(nextrcpt), "[", 1);
+	    vstring_strcat(nextrcpt, "]");
+	    rcpt_domain = strrchr(STR(nextrcpt), '@') + 1;
+	    if ((rc = resolve_local(rcpt_domain)) > 0)	/* XXX */
+		domain = 0;
+	    else if (rc < 0) {
+		*flags |= RESOLVE_FLAG_FAIL;
+		FREE_MEMORY_AND_RETURN;
+	    }
+	} else {
+	    *flags |= RESOLVE_FLAG_ERROR;
+	}
+    }
+    tok822_free_tree(tree);
+    tree = 0;
+
+    /*
+     * XXX Short-cut invalid address forms.
+     */
+    if (*flags & RESOLVE_FLAG_ERROR) {
+	*flags |= RESOLVE_CLASS_DEFAULT;
+	FREE_MEMORY_AND_RETURN;
+    }
+
+    /*
+     * Recognize routing operators in the local-part, even when we do not
+     * recognize ! or % as valid routing operators locally. This is needed to
+     * prevent backup MX hosts from relaying third-party destinations through
+     * primary MX hosts, otherwise the backup host could end up on black
+     * lists. Ignore local swap_bangpath and percent_hack settings because we
+     * can't know how the next MX host is set up.
+     */
+    if (strcmp(STR(nextrcpt) + strcspn(STR(nextrcpt), "@!%") + 1, rcpt_domain))
+	*flags |= RESOLVE_FLAG_ROUTED;
+
+    /*
+     * With local, virtual, relay, or other non-local destinations, give the
+     * highest precedence to transport associated nexthop information.
+     * 
+     * Otherwise, with relay or other non-local destinations, the relayhost
+     * setting overrides the recipient domain name, and the sender-dependent
+     * relayhost overrides both.
+     * 
+     * XXX Nag if the recipient domain is listed in multiple domain lists. The
+     * result is implementation defined, and may break when internals change.
+     * 
+     * For now, we distinguish only a fixed number of address classes.
+     * Eventually this may become extensible, so that new classes can be
+     * configured with their own domain list, delivery transport, and
+     * recipient table.
+     */
+#define STREQ(x,y) (strcmp((x), (y)) == 0)
+
+    if (domain != 0) {
+
+	/*
+	 * Virtual alias domain.
+	 */
+	if (virt_alias_doms
+	    && string_list_match(virt_alias_doms, rcpt_domain)) {
+	    if (var_helpful_warnings) {
+		if (virt_mailbox_doms
+		    && string_list_match(virt_mailbox_doms, rcpt_domain))
+		    msg_warn("do not list domain %s in BOTH %s and %s",
+			     rcpt_domain, VAR_VIRT_ALIAS_DOMS,
+			     VAR_VIRT_MAILBOX_DOMS);
+		if (relay_domains
+		    && domain_list_match(relay_domains, rcpt_domain))
+		    msg_warn("do not list domain %s in BOTH %s and %s",
+			     rcpt_domain, VAR_VIRT_ALIAS_DOMS,
+			     VAR_RELAY_DOMAINS);
+#if 0
+		if (strcasecmp_utf8(rcpt_domain, var_myorigin) == 0)
+		    msg_warn("do not list $%s (%s) in %s",
+			   VAR_MYORIGIN, var_myorigin, VAR_VIRT_ALIAS_DOMS);
+#endif
+	    }
+	    vstring_strcpy(channel, MAIL_SERVICE_ERROR);
+	    vstring_sprintf(nexthop, "5.1.1 User unknown%s",
+			    var_show_unk_rcpt_table ?
+			    " in virtual alias table" : "");
+	    *flags |= RESOLVE_CLASS_ALIAS;
+	} else if (virt_alias_doms && virt_alias_doms->error != 0) {
+	    msg_warn("%s lookup failure", VAR_VIRT_ALIAS_DOMS);
+	    *flags |= RESOLVE_FLAG_FAIL;
+	    FREE_MEMORY_AND_RETURN;
+	}
+
+	/*
+	 * Virtual mailbox domain.
+	 */
+	else if (virt_mailbox_doms
+		 && string_list_match(virt_mailbox_doms, rcpt_domain)) {
+	    if (var_helpful_warnings) {
+		if (relay_domains
+		    && domain_list_match(relay_domains, rcpt_domain))
+		    msg_warn("do not list domain %s in BOTH %s and %s",
+			     rcpt_domain, VAR_VIRT_MAILBOX_DOMS,
+			     VAR_RELAY_DOMAINS);
+	    }
+	    vstring_strcpy(channel, RES_PARAM_VALUE(rp->virt_transport));
+	    vstring_strcpy(nexthop, rcpt_domain);
+	    blame = rp->virt_transport_name;
+	    *flags |= RESOLVE_CLASS_VIRTUAL;
+	} else if (virt_mailbox_doms && virt_mailbox_doms->error != 0) {
+	    msg_warn("%s lookup failure", VAR_VIRT_MAILBOX_DOMS);
+	    *flags |= RESOLVE_FLAG_FAIL;
+	    FREE_MEMORY_AND_RETURN;
+	} else {
+
+	    /*
+	     * Off-host relay destination.
+	     */
+	    if (relay_domains
+		&& domain_list_match(relay_domains, rcpt_domain)) {
+		vstring_strcpy(channel, RES_PARAM_VALUE(rp->relay_transport));
+		blame = rp->relay_transport_name;
+		*flags |= RESOLVE_CLASS_RELAY;
+	    } else if (relay_domains && relay_domains->error != 0) {
+		msg_warn("%s lookup failure", VAR_RELAY_DOMAINS);
+		*flags |= RESOLVE_FLAG_FAIL;
+		FREE_MEMORY_AND_RETURN;
+	    }
+
+	    /*
+	     * Other off-host destination.
+	     */
+	    else {
+		if (rp->snd_def_xp_info
+		    && (xport = mail_addr_find(rp->snd_def_xp_info,
+					    sender_key = (*sender ? sender :
+					       var_null_def_xport_maps_key),
+					       (char **) 0)) != 0) {
+		    if (*xport == 0) {
+			msg_warn("%s: ignoring null lookup result for %s",
+				 rp->snd_def_xp_maps_name, sender_key);
+			xport = "DUNNO";
+		    }
+		    vstring_strcpy(channel, strcasecmp(xport, "DUNNO") == 0 ?
+				RES_PARAM_VALUE(rp->def_transport) : xport);
+		    blame = rp->snd_def_xp_maps_name;
+		} else if (rp->snd_def_xp_info
+			   && rp->snd_def_xp_info->error != 0) {
+		    msg_warn("%s lookup failure", rp->snd_def_xp_maps_name);
+		    *flags |= RESOLVE_FLAG_FAIL;
+		    FREE_MEMORY_AND_RETURN;
+		} else {
+		    vstring_strcpy(channel, RES_PARAM_VALUE(rp->def_transport));
+		    blame = rp->def_transport_name;
+		}
+		*flags |= RESOLVE_CLASS_DEFAULT;
+	    }
+
+	    /*
+	     * With off-host delivery, sender-dependent or global relayhost
+	     * override the recipient domain.
+	     */
+	    if (rp->snd_relay_info
+		&& (relay = mail_addr_find(rp->snd_relay_info,
+					   sender_key = (*sender ? sender :
+						   var_null_relay_maps_key),
+					   (char **) 0)) != 0) {
+		if (*relay == 0) {
+		    msg_warn("%s: ignoring null lookup result for %s",
+			     rp->snd_relay_maps_name, sender_key);
+		    relay = 0;
+		} else if (strcasecmp_utf8(relay, "DUNNO") == 0)
+		    relay = 0;
+	    } else if (rp->snd_relay_info
+		       && rp->snd_relay_info->error != 0) {
+		msg_warn("%s lookup failure", rp->snd_relay_maps_name);
+		*flags |= RESOLVE_FLAG_FAIL;
+		FREE_MEMORY_AND_RETURN;
+	    } else {
+		relay = 0;
+	    }
+	    /* Enforce all the relayhost precedences in one place. */
+	    if (relay != 0) {
+		vstring_strcpy(nexthop, relay);
+	    } else if (*RES_PARAM_VALUE(rp->relayhost))
+		vstring_strcpy(nexthop, RES_PARAM_VALUE(rp->relayhost));
+	    else
+		vstring_strcpy(nexthop, rcpt_domain);
+	}
+    }
+
+    /*
+     * Local delivery.
+     * 
+     * XXX Nag if the domain is listed in multiple domain lists. The effect is
+     * implementation defined, and may break when internals change.
+     */
+    else {
+	if (var_helpful_warnings) {
+	    if (virt_alias_doms
+		&& string_list_match(virt_alias_doms, rcpt_domain))
+		msg_warn("do not list domain %s in BOTH %s and %s",
+			 rcpt_domain, VAR_MYDEST, VAR_VIRT_ALIAS_DOMS);
+	    if (virt_mailbox_doms
+		&& string_list_match(virt_mailbox_doms, rcpt_domain))
+		msg_warn("do not list domain %s in BOTH %s and %s",
+			 rcpt_domain, VAR_MYDEST, VAR_VIRT_MAILBOX_DOMS);
+	}
+	vstring_strcpy(channel, RES_PARAM_VALUE(rp->local_transport));
+	vstring_strcpy(nexthop, rcpt_domain);
+	blame = rp->local_transport_name;
+	*flags |= RESOLVE_CLASS_LOCAL;
+    }
+
+    /*
+     * An explicit main.cf transport:nexthop setting overrides the nexthop.
+     * 
+     * XXX We depend on this mechanism to enforce per-recipient concurrencies
+     * for local recipients. With "local_transport = local:$myhostname" we
+     * force mail for any domain in $mydestination/${proxy,inet}_interfaces
+     * to share the same queue.
+     */
+    if ((destination = split_at(STR(channel), ':')) != 0 && *destination)
+	vstring_strcpy(nexthop, destination);
+
+    /*
+     * Sanity checks.
+     */
+    if (*STR(channel) == 0) {
+	if (blame == 0)
+	    msg_panic("%s: null blame", myname);
+	msg_warn("file %s/%s: parameter %s: null transport is not allowed",
+		 var_config_dir, MAIN_CONF_FILE, blame);
+	*flags |= RESOLVE_FLAG_FAIL;
+	FREE_MEMORY_AND_RETURN;
+    }
+    if (*STR(nexthop) == 0)
+	msg_panic("%s: null nexthop", myname);
+
+    /*
+     * The transport map can selectively override any transport and/or
+     * nexthop host info that is set up above. Unfortunately, the syntax for
+     * nexthop information is transport specific. We therefore need sane and
+     * intuitive semantics for transport map entries that specify a channel
+     * but no nexthop.
+     * 
+     * With non-error transports, the initial nexthop information is the
+     * recipient domain. However, specific main.cf transport definitions may
+     * specify a transport-specific destination, such as a host + TCP socket,
+     * or the pathname of a UNIX-domain socket. With less precedence than
+     * main.cf transport definitions, a main.cf relayhost definition may also
+     * override nexthop information for off-host deliveries.
+     * 
+     * With the error transport, the nexthop information is free text that
+     * specifies the reason for non-delivery.
+     * 
+     * Because nexthop syntax is transport specific we reset the nexthop
+     * information to the recipient domain when the transport table specifies
+     * a transport without also specifying the nexthop information.
+     * 
+     * Subtle note: reset nexthop even when the transport table does not change
+     * the transport. Otherwise it is hard to get rid of main.cf specified
+     * nexthop information.
+     * 
+     * XXX Don't override the virtual alias class (error:User unknown) result.
+     */
+    if (rp->transport_info && !(*flags & RESOLVE_CLASS_ALIAS)) {
+	if (transport_lookup(rp->transport_info, STR(nextrcpt),
+			     rcpt_domain, channel, nexthop) == 0
+	    && rp->transport_info->transport_path->error != 0) {
+	    msg_warn("%s lookup failure", rp->transport_maps_name);
+	    *flags |= RESOLVE_FLAG_FAIL;
+	    FREE_MEMORY_AND_RETURN;
+	}
+    }
+
+    /*
+     * Bounce recipients that have moved, regardless of domain address class.
+     * We do this last, in anticipation of transport maps that can override
+     * the recipient address.
+     * 
+     * The downside of not doing this in delivery agents is that this table has
+     * no effect on local alias expansion results. Such mail will have to
+     * make almost an entire iteration through the mail system.
+     */
+#define IGNORE_ADDR_EXTENSION   ((char **) 0)
+
+    if (relocated_maps != 0) {
+	const char *newloc;
+
+	if ((newloc = mail_addr_find(relocated_maps, STR(nextrcpt),
+				     IGNORE_ADDR_EXTENSION)) != 0) {
+	    vstring_strcpy(channel, MAIL_SERVICE_ERROR);
+	    /* 5.1.6 is the closest match, but not perfect. */
+	    vstring_sprintf(nexthop, "5.1.6 User has moved to %s", newloc);
+	} else if (relocated_maps->error != 0) {
+	    msg_warn("%s lookup failure", VAR_RELOCATED_MAPS);
+	    *flags |= RESOLVE_FLAG_FAIL;
+	    FREE_MEMORY_AND_RETURN;
+	}
+    }
+
+    /*
+     * Bounce recipient addresses that start with `-'. External commands may
+     * misinterpret such addresses as command-line options.
+     * 
+     * In theory I could say people should always carefully set up their
+     * master.cf pipe mailer entries with `--' before the first non-option
+     * argument, but mistakes will happen regardless.
+     * 
+     * Therefore the protection is put in place here, where it cannot be
+     * bypassed.
+     */
+    if (var_allow_min_user == 0 && STR(nextrcpt)[0] == '-') {
+	*flags |= RESOLVE_FLAG_ERROR;
+	FREE_MEMORY_AND_RETURN;
+    }
+
+    /*
+     * Clean up.
+     */
+    FREE_MEMORY_AND_RETURN;
+}
+
+/* Static, so they can be used by the network protocol interface only. */
+
+static VSTRING *channel;
+static VSTRING *nexthop;
+static VSTRING *nextrcpt;
+static VSTRING *query;
+static VSTRING *sender;
+
+/* resolve_proto - read request and send reply */
+
+int     resolve_proto(RES_CONTEXT *context, VSTREAM *stream)
+{
+    int     flags;
+
+    if (attr_scan(stream, ATTR_FLAG_STRICT,
+		  RECV_ATTR_STR(MAIL_ATTR_SENDER, sender),
+		  RECV_ATTR_STR(MAIL_ATTR_ADDR, query),
+		  ATTR_TYPE_END) != 2)
+	return (-1);
+
+    resolve_addr(context, STR(sender), STR(query),
+		 channel, nexthop, nextrcpt, &flags);
+
+    if (msg_verbose)
+	msg_info("`%s' -> `%s' -> (`%s' `%s' `%s' `%d')",
+		 STR(sender), STR(query), STR(channel),
+		 STR(nexthop), STR(nextrcpt), flags);
+
+    attr_print(stream, ATTR_FLAG_NONE,
+	       SEND_ATTR_INT(MAIL_ATTR_FLAGS, server_flags),
+	       SEND_ATTR_STR(MAIL_ATTR_TRANSPORT, STR(channel)),
+	       SEND_ATTR_STR(MAIL_ATTR_NEXTHOP, STR(nexthop)),
+	       SEND_ATTR_STR(MAIL_ATTR_RECIP, STR(nextrcpt)),
+	       SEND_ATTR_INT(MAIL_ATTR_FLAGS, flags),
+	       ATTR_TYPE_END);
+
+    if (vstream_fflush(stream) != 0) {
+	msg_warn("write resolver reply: %m");
+	return (-1);
+    }
+    return (0);
+}
+
+/* resolve_init - module initializations */
+
+void    resolve_init(void)
+{
+    sender = vstring_alloc(100);
+    query = vstring_alloc(100);
+    channel = vstring_alloc(100);
+    nexthop = vstring_alloc(100);
+    nextrcpt = vstring_alloc(100);
+
+    if (*var_virt_alias_doms)
+	virt_alias_doms =
+	    string_list_init(VAR_VIRT_ALIAS_DOMS, MATCH_FLAG_RETURN,
+			     var_virt_alias_doms);
+
+    if (*var_virt_mailbox_doms)
+	virt_mailbox_doms =
+	    string_list_init(VAR_VIRT_MAILBOX_DOMS, MATCH_FLAG_RETURN,
+			     var_virt_mailbox_doms);
+
+    if (*var_relay_domains)
+	relay_domains =
+	    domain_list_init(VAR_RELAY_DOMAINS, MATCH_FLAG_RETURN
+			     | match_parent_style(VAR_RELAY_DOMAINS),
+			     var_relay_domains);
+
+    if (*var_relocated_maps)
+	relocated_maps =
+	    maps_create(VAR_RELOCATED_MAPS, var_relocated_maps,
+			DICT_FLAG_LOCK | DICT_FLAG_FOLD_FIX
+			| DICT_FLAG_UTF8_REQUEST);
+}