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-rw-r--r--src/postscreen/postscreen_starttls.c258
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diff --git a/src/postscreen/postscreen_starttls.c b/src/postscreen/postscreen_starttls.c
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+/*++
+/* NAME
+/* postscreen_starttls 3
+/* SUMMARY
+/* postscreen TLS proxy support
+/* SYNOPSIS
+/* #include <postscreen.h>
+/*
+/* int psc_starttls_open(state, resume_event)
+/* PSC_STATE *state;
+/* void (*resume_event)(int unused_event, char *context);
+/* DESCRIPTION
+/* This module inserts the tlsproxy(8) proxy between the
+/* postscreen(8) server and the remote SMTP client. The entire
+/* process happens in the background, including notification
+/* of completion to the remote SMTP client and to the calling
+/* application.
+/*
+/* Before calling psc_starttls_open() the caller must turn off
+/* all pending timer and I/O event requests on the SMTP client
+/* stream.
+/*
+/* psc_starttls_open() starts the first transaction in the
+/* tlsproxy(8) hand-off protocol, and sets up event handlers
+/* for the successive protocol stages.
+/*
+/* Upon completion, the event handlers call resume_event()
+/* which must reset the SMTP helo/sender/etc. state when the
+/* PSC_STATE_FLAG_USING_TLS is set, and set up timer and read
+/* event requests to receive the next SMTP command.
+/* 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>
+
+/* Utility library. */
+
+#include <msg.h>
+#include <mymalloc.h>
+#include <connect.h>
+#include <stringops.h> /* concatenate() */
+#include <vstring.h>
+
+/* Global library. */
+
+#include <mail_params.h>
+#include <mail_proto.h>
+
+/* TLS library. */
+
+#include <tls_proxy.h>
+
+/* Application-specific. */
+
+#include <postscreen.h>
+
+ /*
+ * For now, this code is built into the postscreen(8) daemon. In the future
+ * it may be abstracted into a reusable library module for use by other
+ * event-driven programs (perhaps smtp-source and smtp-sink).
+ */
+
+ /*
+ * Transient state for the portscreen(8)-to-tlsproxy(8) hand-off protocol.
+ */
+typedef struct {
+ VSTREAM *tlsproxy_stream; /* hand-off negotiation */
+ EVENT_NOTIFY_FN resume_event; /* call-back handler */
+ PSC_STATE *smtp_state; /* SMTP session state */
+} PSC_STARTTLS;
+
+#define TLSPROXY_INIT_TIMEOUT 10
+
+static char *psc_tlsp_service = 0;
+
+/* psc_starttls_finish - complete negotiation with TLS proxy */
+
+static void psc_starttls_finish(int event, void *context)
+{
+ const char *myname = "psc_starttls_finish";
+ PSC_STARTTLS *starttls_state = (PSC_STARTTLS *) context;
+ PSC_STATE *smtp_state = starttls_state->smtp_state;
+ VSTREAM *tlsproxy_stream = starttls_state->tlsproxy_stream;
+ int status;
+
+ if (msg_verbose)
+ msg_info("%s: send client handle on proxy socket %d"
+ " for smtp socket %d from [%s]:%s flags=%s",
+ myname, vstream_fileno(tlsproxy_stream),
+ vstream_fileno(smtp_state->smtp_client_stream),
+ smtp_state->smtp_client_addr, smtp_state->smtp_client_port,
+ psc_print_state_flags(smtp_state->flags, myname));
+
+ /*
+ * We leave read-event notification enabled on the postscreen to TLS
+ * proxy stream, to avoid two kqueue/epoll/etc. system calls: one here,
+ * and one when resuming the dummy SMTP engine.
+ */
+ if (event != EVENT_TIME)
+ event_cancel_timer(psc_starttls_finish, (void *) starttls_state);
+
+ /*
+ * Receive the "TLS is available" indication.
+ *
+ * This may seem out of order, but we must have a read transaction between
+ * sending the request attributes and sending the SMTP client file
+ * descriptor. We can't assume UNIX-domain socket semantics here.
+ */
+ if (event != EVENT_READ
+ || attr_scan(tlsproxy_stream, ATTR_FLAG_STRICT,
+ RECV_ATTR_INT(MAIL_ATTR_STATUS, &status),
+ ATTR_TYPE_END) != 1 || status == 0) {
+
+ /*
+ * The TLS proxy reports that the TLS engine is not available (due to
+ * configuration error, or other causes).
+ */
+ event_disable_readwrite(vstream_fileno(tlsproxy_stream));
+ vstream_fclose(tlsproxy_stream);
+ PSC_SEND_REPLY(smtp_state,
+ "454 4.7.0 TLS not available due to local problem\r\n");
+ }
+
+ /*
+ * Send the remote SMTP client file descriptor.
+ */
+ else if (LOCAL_SEND_FD(vstream_fileno(tlsproxy_stream),
+ vstream_fileno(smtp_state->smtp_client_stream)) < 0) {
+
+ /*
+ * Some error: drop the TLS proxy stream.
+ */
+ msg_warn("%s sending file handle to %s service",
+ event == EVENT_TIME ? "timeout" : "problem",
+ psc_tlsp_service);
+ event_disable_readwrite(vstream_fileno(tlsproxy_stream));
+ vstream_fclose(tlsproxy_stream);
+ PSC_SEND_REPLY(smtp_state,
+ "454 4.7.0 TLS not available due to local problem\r\n");
+ }
+
+ /*
+ * After we send the plaintext 220 greeting, the client-side TLS engine
+ * is supposed to talk first, then the server-side TLS engine. However,
+ * postscreen(8) will not participate in that conversation.
+ */
+ else {
+ PSC_SEND_REPLY(smtp_state, "220 2.0.0 Ready to start TLS\r\n");
+
+ /*
+ * Replace our SMTP client stream by the TLS proxy stream. Once the
+ * TLS handshake is done, the TLS proxy will deliver plaintext SMTP
+ * commands to postscreen(8).
+ *
+ * Swap the file descriptors from under the VSTREAM so that we don't
+ * have to worry about loss of user-configurable VSTREAM attributes.
+ */
+ vstream_fpurge(smtp_state->smtp_client_stream, VSTREAM_PURGE_BOTH);
+ vstream_control(smtp_state->smtp_client_stream,
+ CA_VSTREAM_CTL_SWAP_FD(tlsproxy_stream),
+ CA_VSTREAM_CTL_END);
+ vstream_fclose(tlsproxy_stream); /* direct-to-client stream! */
+ smtp_state->flags |= PSC_STATE_FLAG_USING_TLS;
+ }
+
+ /*
+ * Resume the postscreen(8) dummy SMTP engine and clean up.
+ */
+ starttls_state->resume_event(event, (void *) smtp_state);
+ myfree((void *) starttls_state);
+}
+
+/* psc_starttls_open - open negotiations with TLS proxy */
+
+void psc_starttls_open(PSC_STATE *smtp_state, EVENT_NOTIFY_FN resume_event)
+{
+ const char *myname = "psc_starttls_open";
+ PSC_STARTTLS *starttls_state;
+ VSTREAM *tlsproxy_stream;
+ int fd;
+ static VSTRING *remote_endpt = 0;
+
+ if (psc_tlsp_service == 0) {
+ psc_tlsp_service = concatenate(MAIL_CLASS_PRIVATE "/",
+ var_tlsproxy_service, (char *) 0);
+ remote_endpt = vstring_alloc(20);
+ }
+
+ /*
+ * Connect to the tlsproxy(8) daemon. We report all errors
+ * asynchronously, to avoid having to maintain multiple delivery paths.
+ */
+ if ((fd = LOCAL_CONNECT(psc_tlsp_service, NON_BLOCKING, 1)) < 0) {
+ msg_warn("connect to %s service: %m", psc_tlsp_service);
+ PSC_SEND_REPLY(smtp_state,
+ "454 4.7.0 TLS not available due to local problem\r\n");
+ event_request_timer(resume_event, (void *) smtp_state, 0);
+ return;
+ }
+ if (msg_verbose)
+ msg_info("%s: send client name/address on proxy socket %d"
+ " for smtp socket %d from [%s]:%s flags=%s",
+ myname, fd, vstream_fileno(smtp_state->smtp_client_stream),
+ smtp_state->smtp_client_addr, smtp_state->smtp_client_port,
+ psc_print_state_flags(smtp_state->flags, myname));
+
+ /*
+ * Initial handshake. Send the data attributes now, and send the client
+ * file descriptor in a later transaction. We report all errors
+ * asynchronously, to avoid having to maintain multiple delivery paths.
+ *
+ * XXX The formatted endpoint should be a state member. Then, we can
+ * simplify all the format strings throughout the program.
+ */
+ tlsproxy_stream = vstream_fdopen(fd, O_RDWR);
+ vstring_sprintf(remote_endpt, "[%s]:%s", smtp_state->smtp_client_addr,
+ smtp_state->smtp_client_port);
+ attr_print(tlsproxy_stream, ATTR_FLAG_NONE,
+ SEND_ATTR_STR(TLS_ATTR_REMOTE_ENDPT, STR(remote_endpt)),
+ SEND_ATTR_INT(TLS_ATTR_FLAGS, TLS_PROXY_FLAG_ROLE_SERVER),
+ SEND_ATTR_INT(TLS_ATTR_TIMEOUT, psc_normal_cmd_time_limit),
+ SEND_ATTR_INT(TLS_ATTR_TIMEOUT, psc_normal_cmd_time_limit),
+ SEND_ATTR_STR(TLS_ATTR_SERVERID, MAIL_SERVICE_SMTPD), /* XXX */
+ ATTR_TYPE_END);
+ if (vstream_fflush(tlsproxy_stream) != 0) {
+ msg_warn("error sending request to %s service: %m", psc_tlsp_service);
+ vstream_fclose(tlsproxy_stream);
+ PSC_SEND_REPLY(smtp_state,
+ "454 4.7.0 TLS not available due to local problem\r\n");
+ event_request_timer(resume_event, (void *) smtp_state, 0);
+ return;
+ }
+
+ /*
+ * Set up a read event for the next phase of the TLS proxy handshake.
+ */
+ starttls_state = (PSC_STARTTLS *) mymalloc(sizeof(*starttls_state));
+ starttls_state->tlsproxy_stream = tlsproxy_stream;
+ starttls_state->resume_event = resume_event;
+ starttls_state->smtp_state = smtp_state;
+ PSC_READ_EVENT_REQUEST(vstream_fileno(tlsproxy_stream), psc_starttls_finish,
+ (void *) starttls_state, TLSPROXY_INIT_TIMEOUT);
+}