1 files changed, 293 insertions, 0 deletions

diff --git a/src/postscreen/postscreen_send.c b/src/postscreen/postscreen_send.c
new file mode 100644
index 0000000..53714b1
--- /dev/null
+++ b/src/postscreen/postscreen_send.c
@@ -0,0 +1,293 @@
+/*++
+/* NAME
+/*	postscreen_send 3
+/* SUMMARY
+/*	postscreen low-level output
+/* SYNOPSIS
+/*	#include <postscreen.h>
+/*
+/*	void	pcs_send_pre_jail_init(void)
+/*
+/*	int	psc_send_reply(state, text)
+/*	PSC_STATE *state;
+/*	const char *text;
+/*
+/*	int	PSC_SEND_REPLY(state, text)
+/*	PSC_STATE *state;
+/*	const char *text;
+/*
+/*	void	psc_send_socket(state)
+/*	PSC_STATE *state;
+/* DESCRIPTION
+/*	pcs_send_pre_jail_init() performs one-time initialization.
+/*
+/*	psc_send_reply() sends the specified text to the specified
+/*	remote SMTP client.  In case of an immediate error, it logs
+/*	a warning (except EPIPE) with the client address and port,
+/*	and returns a non-zero result (all errors including EPIPE).
+/*
+/*	psc_send_reply() does a best effort to send the reply, but
+/*	it won't block when the output is throttled by a hostile
+/*	peer.
+/*
+/*	PSC_SEND_REPLY() is a legacy wrapper for psc_send_reply().
+/*	It will eventually be replaced by its expansion.
+/*
+/*	psc_send_socket() sends the specified socket to the real
+/*	Postfix SMTP server. The socket is delivered in the background.
+/*	This function must be called after all other session-related
+/*	work is finished including postscreen cache updates.
+/*
+/*	In case of an immediate error, psc_send_socket() sends a 421
+/*	reply to the remote SMTP client and closes the connection.
+/*	If the 220- greeting was sent, sending 421 would be invalid;
+/*	instead, the client is redirected to the dummy SMTP engine
+/*	which sends the 421 reply at the first legitimate opportunity.
+/* 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 <string.h>
+#include <errno.h>
+
+/* Utility library. */
+
+#include <msg.h>
+#include <iostuff.h>
+#include <connect.h>
+#include <attr.h>
+#include <vstream.h>
+
+/* Global library. */
+
+#include <mail_params.h>
+#include <smtp_reply_footer.h>
+#include <mail_proto.h>
+#include <maps.h>
+
+/* Application-specific. */
+
+#include <postscreen.h>
+
+static MAPS *psc_rej_ftr_maps;
+
+ /*
+  * This program screens all inbound SMTP connections, so it better not waste
+  * time.
+  */
+#define PSC_SEND_SOCK_CONNECT_TIMEOUT	1
+#define PSC_SEND_SOCK_NOTIFY_TIMEOUT	100
+
+/* pcs_send_pre_jail_init - initialize */
+
+void    pcs_send_pre_jail_init(void)
+{
+    static int init_count = 0;
+
+    if (init_count++ != 0)
+	msg_panic("pcs_send_pre_jail_init: multiple calls");
+
+    /*
+     * SMTP server reject footer.
+     */
+    if (*var_psc_rej_ftr_maps)
+	psc_rej_ftr_maps = maps_create(VAR_SMTPD_REJ_FTR_MAPS,
+				       var_psc_rej_ftr_maps,
+				       DICT_FLAG_LOCK);
+}
+
+/* psc_get_footer - find that footer */
+
+static const char *psc_get_footer(const char *text, ssize_t text_len)
+{
+    static VSTRING *footer_buf = 0;
+
+    if (footer_buf == 0)
+	footer_buf = vstring_alloc(100);
+    /* Strip the \r\n for consistency with smtpd. */
+    vstring_strncpy(footer_buf, text, text_len);
+    return (psc_maps_find(psc_rej_ftr_maps, STR(footer_buf), 0));
+}
+
+/* psc_send_reply - send reply to remote SMTP client */
+
+int     psc_send_reply(PSC_STATE *state, const char *text)
+{
+    ssize_t start;
+    int     ret;
+    const char *footer;
+    ssize_t text_len = strlen(text) - 2;
+
+    if (msg_verbose)
+	msg_info("> [%s]:%s: %.*s", state->smtp_client_addr,
+		 state->smtp_client_port, (int) text_len, text);
+
+    /*
+     * Append the new text to earlier text that could not be sent because the
+     * output was throttled.
+     */
+    start = VSTRING_LEN(state->send_buf);
+    vstring_strcat(state->send_buf, text);
+
+    /*
+     * For soft_bounce support, we also fix the REJECT logging before the
+     * dummy SMTP engine calls the psc_send_reply() output routine. We do
+     * some double work, but it is for debugging only.
+     */
+    if (var_soft_bounce) {
+	if (text[0] == '5')
+	    STR(state->send_buf)[start + 0] = '4';
+	if (text[4] == '5')
+	    STR(state->send_buf)[start + 4] = '4';
+    }
+
+    /*
+     * Append the optional reply footer.
+     */
+    if ((*text == '4' || *text == '5')
+	&& ((psc_rej_ftr_maps != 0
+	     && (footer = psc_get_footer(text, text_len)) != 0)
+	    || *(footer = var_psc_rej_footer) != 0))
+	smtp_reply_footer(state->send_buf, start, footer,
+			  STR(psc_expand_filter), psc_expand_lookup,
+			  (void *) state);
+
+    /*
+     * Do a best effort sending text, but don't block when the output is
+     * throttled by a hostile peer.
+     */
+    ret = write(vstream_fileno(state->smtp_client_stream),
+		STR(state->send_buf), LEN(state->send_buf));
+    if (ret > 0)
+	vstring_truncate(state->send_buf, ret - LEN(state->send_buf));
+    if (ret < 0 && errno != EAGAIN && errno != EPIPE && errno != ECONNRESET)
+	msg_warn("write [%s]:%s: %m", state->smtp_client_addr,
+		 state->smtp_client_port);
+    return (ret < 0 && errno != EAGAIN);
+}
+
+/* psc_send_socket_close_event - file descriptor has arrived or timeout */
+
+static void psc_send_socket_close_event(int event, void *context)
+{
+    const char *myname = "psc_send_socket_close_event";
+    PSC_STATE *state = (PSC_STATE *) context;
+
+    if (msg_verbose > 1)
+	msg_info("%s: sq=%d cq=%d event %d on send socket %d from [%s]:%s",
+		 myname, psc_post_queue_length, psc_check_queue_length,
+		 event, state->smtp_server_fd, state->smtp_client_addr,
+		 state->smtp_client_port);
+
+    /*
+     * The real SMTP server has closed the local IPC channel, or we have
+     * reached the limit of our patience. In the latter case it is still
+     * possible that the real SMTP server will receive the socket so we
+     * should not interfere.
+     */
+    PSC_CLEAR_EVENT_REQUEST(state->smtp_server_fd, psc_send_socket_close_event,
+			    context);
+    if (event == EVENT_TIME)
+	msg_warn("timeout sending connection to service %s",
+		 psc_smtpd_service_name);
+    psc_free_session_state(state);
+}
+
+/* psc_send_socket - send socket to real SMTP server process */
+
+void    psc_send_socket(PSC_STATE *state)
+{
+    const char *myname = "psc_send_socket";
+    int     server_fd;
+    int     pass_err;
+    VSTREAM *fp;
+
+    if (msg_verbose > 1)
+	msg_info("%s: sq=%d cq=%d send socket %d from [%s]:%s",
+		 myname, psc_post_queue_length, psc_check_queue_length,
+		 vstream_fileno(state->smtp_client_stream),
+		 state->smtp_client_addr, state->smtp_client_port);
+
+    /*
+     * Connect to the real SMTP service over a local IPC channel, send the
+     * file descriptor, and close the file descriptor to save resources.
+     * Experience has shown that some systems will discard information when
+     * we close a channel immediately after writing. Thus, we waste resources
+     * waiting for the remote side to close the local IPC channel first. The
+     * good side of waiting is that we learn when the real SMTP server is
+     * falling behind.
+     * 
+     * This is where we would forward the connection to an SMTP server that
+     * provides an appropriate level of service for this client class. For
+     * example, a server that is more forgiving, or one that is more
+     * suspicious. Alternatively, we could send attributes along with the
+     * socket with client reputation information, making everything even more
+     * Postfix-specific.
+     */
+    if ((server_fd =
+	 LOCAL_CONNECT(psc_smtpd_service_name, NON_BLOCKING,
+		       PSC_SEND_SOCK_CONNECT_TIMEOUT)) < 0) {
+	msg_warn("cannot connect to service %s: %m", psc_smtpd_service_name);
+	if (state->flags & PSC_STATE_FLAG_PREGR_TODO) {
+	    PSC_SMTPD_X21(state, "421 4.3.2 No system resources\r\n");
+	} else {
+	    PSC_SEND_REPLY(state, "421 4.3.2 All server ports are busy\r\n");
+	    psc_free_session_state(state);
+	}
+	return;
+    }
+    /* XXX Note: no dummy read between LOCAL_SEND_FD() and attr_print(). */
+    fp = vstream_fdopen(server_fd, O_RDWR);
+    pass_err =
+	(LOCAL_SEND_FD(server_fd,
+		       vstream_fileno(state->smtp_client_stream)) < 0
+	 || (attr_print(fp, ATTR_FLAG_NONE,
+	  SEND_ATTR_STR(MAIL_ATTR_ACT_CLIENT_ADDR, state->smtp_client_addr),
+	  SEND_ATTR_STR(MAIL_ATTR_ACT_CLIENT_PORT, state->smtp_client_port),
+	  SEND_ATTR_STR(MAIL_ATTR_ACT_SERVER_ADDR, state->smtp_server_addr),
+	  SEND_ATTR_STR(MAIL_ATTR_ACT_SERVER_PORT, state->smtp_server_port),
+			ATTR_TYPE_END) || vstream_fflush(fp)));
+    /* XXX Note: no read between attr_print() and vstream_fdclose(). */
+    (void) vstream_fdclose(fp);
+    if (pass_err != 0) {
+	msg_warn("cannot pass connection to service %s: %m",
+		 psc_smtpd_service_name);
+	(void) close(server_fd);
+	if (state->flags & PSC_STATE_FLAG_PREGR_TODO) {
+	    PSC_SMTPD_X21(state, "421 4.3.2 No system resources\r\n");
+	} else {
+	    PSC_SEND_REPLY(state, "421 4.3.2 No system resources\r\n");
+	    psc_free_session_state(state);
+	}
+	return;
+    } else {
+
+	/*
+	 * Closing the smtp_client_fd here triggers a FreeBSD 7.1 kernel bug
+	 * where smtp-source sometimes sees the connection being closed after
+	 * it has already received the real SMTP server's 220 greeting!
+	 */
+#if 0
+	PSC_DEL_CLIENT_STATE(state);
+#endif
+	PSC_ADD_SERVER_STATE(state, server_fd);
+	PSC_READ_EVENT_REQUEST(state->smtp_server_fd, psc_send_socket_close_event,
+			       (void *) state, PSC_SEND_SOCK_NOTIFY_TIMEOUT);
+	return;
+    }
+}