Adding upstream version 3.4.23.upstream/3.4.23upstream

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

1 files changed, 377 insertions, 0 deletions

diff --git a/src/postscreen/postscreen_early.c b/src/postscreen/postscreen_early.c
new file mode 100644
index 0000000..50b46ee
--- /dev/null
+++ b/src/postscreen/postscreen_early.c
@@ -0,0 +1,377 @@
+/*++
+/* NAME
+/*	postscreen_early 3
+/* SUMMARY
+/*	postscreen pre-handshake tests
+/* SYNOPSIS
+/*	#include <postscreen.h>
+/*
+/*	void	psc_early_init(void)
+/*
+/*	void	psc_early_tests(state)
+/*	PSC_STATE *state;
+/* DESCRIPTION
+/*	psc_early_tests() performs protocol tests before the SMTP
+/*	handshake: the pregreet test and the DNSBL test. Control
+/*	is passed to the psc_smtpd_tests() routine as appropriate.
+/*
+/*	psc_early_init() performs one-time initialization.
+/* 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 <sys/socket.h>
+#include <limits.h>
+
+/* Utility library. */
+
+#include <msg.h>
+#include <stringops.h>
+#include <mymalloc.h>
+#include <vstring.h>
+
+/* Global library. */
+
+#include <mail_params.h>
+
+/* Application-specific. */
+
+#include <postscreen.h>
+
+static char *psc_teaser_greeting;
+static VSTRING *psc_escape_buf;
+
+/* psc_whitelist_non_dnsbl - whitelist pending non-dnsbl tests */
+
+static void psc_whitelist_non_dnsbl(PSC_STATE *state)
+{
+    time_t  now;
+    int     tindx;
+
+    /*
+     * If no tests failed (we can't undo those), and if the whitelist
+     * threshold is met, flag non-dnsbl tests that are pending or disabled as
+     * successfully completed, and set their expiration times equal to the
+     * DNSBL expiration time, except for tests that would expire later.
+     * 
+     * Why flag disabled tests as passed? When a disabled test is turned on,
+     * postscreen should not apply that test to clients that are already
+     * whitelisted based on their combined DNSBL score.
+     */
+    if ((state->flags & PSC_STATE_MASK_ANY_FAIL) == 0
+	&& state->dnsbl_score < var_psc_dnsbl_thresh
+	&& var_psc_dnsbl_wthresh < 0
+	&& state->dnsbl_score <= var_psc_dnsbl_wthresh) {
+	now = event_time();
+	for (tindx = 0; tindx < PSC_TINDX_COUNT; tindx++) {
+	    if (tindx == PSC_TINDX_DNSBL)
+		continue;
+	    if ((state->flags & PSC_STATE_FLAG_BYTINDX_TODO(tindx))
+		&& !(state->flags & PSC_STATE_FLAG_BYTINDX_PASS(tindx))) {
+		if (msg_verbose)
+		    msg_info("skip %s test for [%s]:%s",
+			 psc_test_name(tindx), PSC_CLIENT_ADDR_PORT(state));
+		/* Wrong for deep protocol tests, but we disable those. */
+		state->flags |= PSC_STATE_FLAG_BYTINDX_DONE(tindx);
+		/* This also disables pending deep protocol tests. */
+		state->flags |= PSC_STATE_FLAG_BYTINDX_PASS(tindx);
+	    }
+	    /* Update expiration even if the test was completed or disabled. */
+	    if (state->client_info->expire_time[tindx] < now + state->dnsbl_ttl)
+		state->client_info->expire_time[tindx] = now + state->dnsbl_ttl;
+	}
+    }
+}
+
+/* psc_early_event - handle pre-greet, EOF, and DNSBL results. */
+
+static void psc_early_event(int event, void *context)
+{
+    const char *myname = "psc_early_event";
+    PSC_STATE *state = (PSC_STATE *) context;
+    time_t *expire_time = state->client_info->expire_time;
+    char    read_buf[PSC_READ_BUF_SIZE];
+    int     read_count;
+    DELTA_TIME elapsed;
+
+    if (msg_verbose > 1)
+	msg_info("%s: sq=%d cq=%d event %d on smtp socket %d from [%s]:%s flags=%s",
+		 myname, psc_post_queue_length, psc_check_queue_length,
+		 event, vstream_fileno(state->smtp_client_stream),
+		 state->smtp_client_addr, state->smtp_client_port,
+		 psc_print_state_flags(state->flags, myname));
+
+    PSC_CLEAR_EVENT_REQUEST(vstream_fileno(state->smtp_client_stream),
+			    psc_early_event, context);
+
+    /*
+     * XXX Be sure to empty the DNSBL lookup buffer otherwise we have a
+     * memory leak.
+     * 
+     * XXX We can avoid "forgetting" to do this by keeping a pointer to the
+     * DNSBL lookup buffer in the PSC_STATE structure. This also allows us to
+     * shave off a hash table lookup when retrieving the DNSBL result.
+     * 
+     * A direct pointer increases the odds of dangling pointers. Hash-table
+     * lookup is safer, and that is why it's done that way.
+     */
+    switch (event) {
+
+	/*
+	 * We either reached the end of the early tests time limit, or all
+	 * early tests completed before the pregreet timer would go off.
+	 */
+    case EVENT_TIME:
+
+	/*
+	 * Check if the SMTP client spoke before its turn.
+	 */
+	if ((state->flags & PSC_STATE_FLAG_PREGR_TODO) != 0
+	    && (state->flags & PSC_STATE_MASK_PREGR_FAIL_DONE) == 0) {
+	    expire_time[PSC_TINDX_PREGR] = event_time() + var_psc_pregr_ttl;
+	    PSC_PASS_SESSION_STATE(state, "pregreet test",
+				   PSC_STATE_FLAG_PREGR_PASS);
+	}
+	if ((state->flags & PSC_STATE_FLAG_PREGR_FAIL)
+	    && psc_pregr_action == PSC_ACT_IGNORE) {
+	    PSC_UNFAIL_SESSION_STATE(state, PSC_STATE_FLAG_PREGR_FAIL);
+	    /* Not: PSC_PASS_SESSION_STATE. Repeat this test the next time. */
+	}
+
+	/*
+	 * Collect the DNSBL score, and whitelist other tests if applicable.
+	 * Note: this score will be partial when some DNS lookup did not
+	 * complete before the pregreet timer expired.
+	 * 
+	 * If the client is DNS blocklisted, drop the connection, send the
+	 * client to a dummy protocol engine, or continue to the next test.
+	 */
+#define PSC_DNSBL_FORMAT \
+	"%s 5.7.1 Service unavailable; client [%s] blocked using %s\r\n"
+#define NO_DNSBL_SCORE	INT_MAX
+
+	if (state->flags & PSC_STATE_FLAG_DNSBL_TODO) {
+	    if (state->dnsbl_score == NO_DNSBL_SCORE) {
+		state->dnsbl_score =
+		    psc_dnsbl_retrieve(state->smtp_client_addr,
+				       &state->dnsbl_name,
+				       state->dnsbl_index,
+				       &state->dnsbl_ttl);
+		if (var_psc_dnsbl_wthresh < 0)
+		    psc_whitelist_non_dnsbl(state);
+	    }
+	    if (state->dnsbl_score < var_psc_dnsbl_thresh) {
+		expire_time[PSC_TINDX_DNSBL] = event_time() + state->dnsbl_ttl;
+		PSC_PASS_SESSION_STATE(state, "dnsbl test",
+				       PSC_STATE_FLAG_DNSBL_PASS);
+	    } else {
+		msg_info("DNSBL rank %d for [%s]:%s",
+			 state->dnsbl_score, PSC_CLIENT_ADDR_PORT(state));
+		PSC_FAIL_SESSION_STATE(state, PSC_STATE_FLAG_DNSBL_FAIL);
+		switch (psc_dnsbl_action) {
+		case PSC_ACT_DROP:
+		    state->dnsbl_reply = vstring_sprintf(vstring_alloc(100),
+						    PSC_DNSBL_FORMAT, "521",
+						    state->smtp_client_addr,
+							 state->dnsbl_name);
+		    PSC_DROP_SESSION_STATE(state, STR(state->dnsbl_reply));
+		    return;
+		case PSC_ACT_ENFORCE:
+		    state->dnsbl_reply = vstring_sprintf(vstring_alloc(100),
+						    PSC_DNSBL_FORMAT, "550",
+						    state->smtp_client_addr,
+							 state->dnsbl_name);
+		    PSC_ENFORCE_SESSION_STATE(state, STR(state->dnsbl_reply));
+		    break;
+		case PSC_ACT_IGNORE:
+		    PSC_UNFAIL_SESSION_STATE(state, PSC_STATE_FLAG_DNSBL_FAIL);
+		    /* Not: PSC_PASS_SESSION_STATE. Repeat this test. */
+		    break;
+		default:
+		    msg_panic("%s: unknown dnsbl action value %d",
+			      myname, psc_dnsbl_action);
+
+		}
+	    }
+	}
+
+	/*
+	 * Pass the connection to a real SMTP server, or enter the dummy
+	 * engine for deep tests.
+	 */
+	if ((state->flags & PSC_STATE_FLAG_NOFORWARD) != 0
+	    || ((state->flags & PSC_STATE_MASK_SMTPD_PASS)
+		!= PSC_STATE_FLAGS_TODO_TO_PASS(state->flags & PSC_STATE_MASK_SMTPD_TODO)))
+	    psc_smtpd_tests(state);
+	else
+	    psc_conclude(state);
+	return;
+
+	/*
+	 * EOF, or the client spoke before its turn. We simply drop the
+	 * connection, or we continue waiting and allow DNS replies to
+	 * trickle in.
+	 */
+    default:
+	if ((read_count = recv(vstream_fileno(state->smtp_client_stream),
+			  read_buf, sizeof(read_buf) - 1, MSG_PEEK)) <= 0) {
+	    /* Avoid memory leak. */
+	    if (state->dnsbl_score == NO_DNSBL_SCORE
+		&& (state->flags & PSC_STATE_FLAG_DNSBL_TODO))
+		(void) psc_dnsbl_retrieve(state->smtp_client_addr,
+					  &state->dnsbl_name,
+					  state->dnsbl_index,
+					  &state->dnsbl_ttl);
+	    /* XXX Wait for DNS replies to come in. */
+	    psc_hangup_event(state);
+	    return;
+	}
+	read_buf[read_count] = 0;
+	escape(psc_escape_buf, read_buf, read_count);
+	msg_info("PREGREET %d after %s from [%s]:%s: %.100s", read_count,
+	       psc_format_delta_time(psc_temp, state->start_time, &elapsed),
+		 PSC_CLIENT_ADDR_PORT(state), STR(psc_escape_buf));
+	PSC_FAIL_SESSION_STATE(state, PSC_STATE_FLAG_PREGR_FAIL);
+	switch (psc_pregr_action) {
+	case PSC_ACT_DROP:
+	    /* Avoid memory leak. */
+	    if (state->dnsbl_score == NO_DNSBL_SCORE
+		&& (state->flags & PSC_STATE_FLAG_DNSBL_TODO))
+		(void) psc_dnsbl_retrieve(state->smtp_client_addr,
+					  &state->dnsbl_name,
+					  state->dnsbl_index,
+					  &state->dnsbl_ttl);
+	    PSC_DROP_SESSION_STATE(state, "521 5.5.1 Protocol error\r\n");
+	    return;
+	case PSC_ACT_ENFORCE:
+	    /* We call psc_dnsbl_retrieve() when the timer expires. */
+	    PSC_ENFORCE_SESSION_STATE(state, "550 5.5.1 Protocol error\r\n");
+	    break;
+	case PSC_ACT_IGNORE:
+	    /* We call psc_dnsbl_retrieve() when the timer expires. */
+	    /* We must handle this case after the timer expires. */
+	    break;
+	default:
+	    msg_panic("%s: unknown pregreet action value %d",
+		      myname, psc_pregr_action);
+	}
+
+	/*
+	 * Terminate the greet delay if we're just waiting for the pregreet
+	 * test to complete. It is safe to call psc_early_event directly,
+	 * since we are already in that function.
+	 * 
+	 * XXX After this code passes all tests, swap around the two blocks in
+	 * this switch statement and fall through from EVENT_READ into
+	 * EVENT_TIME, instead of calling psc_early_event recursively.
+	 */
+	state->flags |= PSC_STATE_FLAG_PREGR_DONE;
+	if (elapsed.dt_sec >= PSC_EFF_GREET_WAIT
+	    || ((state->flags & PSC_STATE_MASK_EARLY_DONE)
+		== PSC_STATE_FLAGS_TODO_TO_DONE(state->flags & PSC_STATE_MASK_EARLY_TODO)))
+	    psc_early_event(EVENT_TIME, context);
+	else
+	    event_request_timer(psc_early_event, context,
+				PSC_EFF_GREET_WAIT - elapsed.dt_sec);
+	return;
+    }
+}
+
+/* psc_early_dnsbl_event - cancel pregreet timer if waiting for DNS only */
+
+static void psc_early_dnsbl_event(int unused_event, void *context)
+{
+    const char *myname = "psc_early_dnsbl_event";
+    PSC_STATE *state = (PSC_STATE *) context;
+
+    if (msg_verbose)
+	msg_info("%s: notify [%s]:%s", myname, PSC_CLIENT_ADDR_PORT(state));
+
+    /*
+     * Collect the DNSBL score, and whitelist other tests if applicable.
+     */
+    state->dnsbl_score =
+	psc_dnsbl_retrieve(state->smtp_client_addr, &state->dnsbl_name,
+			   state->dnsbl_index, &state->dnsbl_ttl);
+    if (var_psc_dnsbl_wthresh < 0)
+	psc_whitelist_non_dnsbl(state);
+
+    /*
+     * Terminate the greet delay if we're just waiting for DNSBL lookup to
+     * complete. Don't call psc_early_event directly, that would result in a
+     * dangling pointer.
+     */
+    state->flags |= PSC_STATE_FLAG_DNSBL_DONE;
+    if ((state->flags & PSC_STATE_MASK_EARLY_DONE)
+	== PSC_STATE_FLAGS_TODO_TO_DONE(state->flags & PSC_STATE_MASK_EARLY_TODO))
+	event_request_timer(psc_early_event, context, EVENT_NULL_DELAY);
+}
+
+/* psc_early_tests - start the early (before protocol) tests */
+
+void    psc_early_tests(PSC_STATE *state)
+{
+    const char *myname = "psc_early_tests";
+
+    /*
+     * Report errors and progress in the context of this test.
+     */
+    PSC_BEGIN_TESTS(state, "tests before SMTP handshake");
+
+    /*
+     * Run a PREGREET test. Send half the greeting banner, by way of teaser,
+     * then wait briefly to see if the client speaks before its turn.
+     */
+    if ((state->flags & PSC_STATE_FLAG_PREGR_TODO) != 0
+	&& psc_teaser_greeting != 0
+	&& PSC_SEND_REPLY(state, psc_teaser_greeting) != 0) {
+	psc_hangup_event(state);
+	return;
+    }
+
+    /*
+     * Run a DNS blocklist query.
+     */
+    if ((state->flags & PSC_STATE_FLAG_DNSBL_TODO) != 0)
+	state->dnsbl_index =
+	    psc_dnsbl_request(state->smtp_client_addr, psc_early_dnsbl_event,
+			      (void *) state);
+    else
+	state->dnsbl_index = -1;
+    state->dnsbl_score = NO_DNSBL_SCORE;
+
+    /*
+     * Wait for the client to respond or for DNS lookup to complete.
+     */
+    if ((state->flags & PSC_STATE_FLAG_PREGR_TODO) != 0)
+	PSC_READ_EVENT_REQUEST(vstream_fileno(state->smtp_client_stream),
+		       psc_early_event, (void *) state, PSC_EFF_GREET_WAIT);
+    else
+	event_request_timer(psc_early_event, (void *) state, PSC_EFF_GREET_WAIT);
+}
+
+/* psc_early_init - initialize early tests */
+
+void    psc_early_init(void)
+{
+    if (*var_psc_pregr_banner) {
+	vstring_sprintf(psc_temp, "220-%s\r\n", var_psc_pregr_banner);
+	psc_teaser_greeting = mystrdup(STR(psc_temp));
+	psc_escape_buf = vstring_alloc(100);
+    }
+}