1 files changed, 149 insertions, 0 deletions
diff --git a/src/smtpd/smtpd_dsn_fix.c b/src/smtpd/smtpd_dsn_fix.c
new file mode 100644
index 0000000..d436967
--- /dev/null
+++ b/src/smtpd/smtpd_dsn_fix.c
@@ -0,0 +1,149 @@
+/*++
+/* NAME
+/*	smtpd_dsn_fix 3
+/* SUMMARY
+/*	fix DSN status
+/* SYNOPSIS
+/*	#include <smtpd_dsn_fix.h>
+/*
+/*	const char *smtpd_dsn_fix(status, reply_class)
+/*	const char *status;
+/*	const char *reply_class;
+/* DESCRIPTION
+/*	smtpd_dsn_fix() transforms DSN status codes according to the
+/*	status information that is actually being reported. The
+/*	following transformations are implemented:
+/* .IP \(bu
+/*	Transform a recipient address DSN into a sender address DSN
+/*	when reporting sender address status information, and vice
+/*	versa. This transformation may be needed because some Postfix
+/*	access control features don't know whether the address being
+/*	rejected is a sender or recipient. Examples are smtpd access
+/*	tables, rbl reply templates, and the error mailer.
+/* .IP \(bu
+/*	Transform a sender or recipient address DSN into a non-address
+/*	DSN when reporting non-address status information. For
+/*	example, if something rejects HELO with DSN status 4.1.1
+/*	(unknown recipient address), then we send the more neutral
+/*	4.0.0 DSN instead. This transformation is needed when the
+/*	same smtpd access map entry or rbl reply template is used
+/*	for both address and non-address information.
+/* .PP
+/*	A non-address DSN is not transformed
+/*	when reporting sender or recipient address status information,
+/*	as there are many legitimate instances of such usage.
+/*
+/*	It is left up to the caller to update the initial DSN digit
+/*	appropriately; in Postfix this is done as late as possible,
+/*	because hard rejects may be changed into soft rejects for
+/*	all kinds of reasons.
+/*
+/*	Arguments:
+/* .IP status
+/*	A DSN status as per RFC 3463.
+/* .IP reply_class
+/*	SMTPD_NAME_SENDER, SMTPD_NAME_RECIPIENT or some other
+/*	null-terminated string.
+/* 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
+/*--*/
+/* System library. */
+
+#include <sys_defs.h>
+#include <ctype.h>
+#include <string.h>
+
+/* Utility library. */
+
+#include <msg.h>
+
+/* Global library. */
+
+/* Application-specific. */
+
+#include <smtpd_dsn_fix.h>
+
+struct dsn_map {
+    const char *micro_code;		/* Final digits in mailbox D.S.N. */
+    const char *sender_dsn;		/* Replacement sender D.S.N. */
+    const char *rcpt_dsn;		/* Replacement recipient D.S.N. */
+};
+
+static struct dsn_map dsn_map[] = {
+    /* - Sender - Recipient */
+    "1", SND_DSN, "4.1.1",		/* 4.1.1: Bad dest mbox addr */
+    "2", "4.1.8", "4.1.2",		/* 4.1.2: Bad dest system addr */
+    "3", "4.1.7", "4.1.3",		/* 4.1.3: Bad dest mbox addr syntax */
+    "4", SND_DSN, "4.1.4",		/* 4.1.4: Dest mbox addr ambiguous */
+    "5", "4.1.0", "4.1.5",		/* 4.1.5: Dest mbox addr valid */
+    "6", SND_DSN, "4.1.6",		/* 4.1.6: Mailbox has moved */
+    "7", "4.1.7", "4.1.3",		/* 4.1.7: Bad sender mbox addr syntax */
+    "8", "4.1.8", "4.1.2",		/* 4.1.8: Bad sender system addr */
+    0, "4.1.0", "4.1.0",		/* Default mapping */
+};
+
+/* smtpd_dsn_fix - fix DSN status */
+
+const char *smtpd_dsn_fix(const char *status, const char *reply_class)
+{
+    struct dsn_map *dp;
+    const char *result = status;
+
+    /*
+     * Update an address-specific DSN according to what is being rejected.
+     */
+    if (ISDIGIT(status[0]) && strncmp(status + 1, ".1.", 3) == 0) {
+
+	/*
+	 * Fix recipient address DSN while rejecting a sender address. Don't
+	 * let future recipient-specific DSN codes slip past us.
+	 */
+	if (strcmp(reply_class, SMTPD_NAME_SENDER) == 0) {
+	    for (dp = dsn_map; dp->micro_code != 0; dp++)
+		if (strcmp(status + 4, dp->micro_code) == 0)
+		    break;
+	    result = dp->sender_dsn;
+	}
+
+	/*
+	 * Fix sender address DSN while rejecting a recipient address. Don't
+	 * let future sender-specific DSN codes slip past us.
+	 */
+	else if (strcmp(reply_class, SMTPD_NAME_RECIPIENT) == 0) {
+	    for (dp = dsn_map; dp->micro_code != 0; dp++)
+		if (strcmp(status + 4, dp->micro_code) == 0)
+		    break;
+	    result = dp->rcpt_dsn;
+	}
+
+	/*
+	 * Fix address-specific DSN while rejecting a non-address.
+	 */
+	else {
+	    result = "4.0.0";
+	}
+
+	/*
+	 * Give them a clue of what is going on.
+	 */
+	if (strcmp(status + 2, result + 2) != 0)
+	    msg_info("mapping DSN status %s into %s status %c%s",
+		     status, reply_class, status[0], result + 1);
+	return (result);
+    }
+
+    /*
+     * Don't update a non-address DSN. There are many legitimate uses for
+     * these while rejecting address or non-address information.
+     */
+    else {
+	return (status);
+    }
+}