1 files changed, 341 insertions, 0 deletions
diff --git a/src/global/verify_sender_addr.c b/src/global/verify_sender_addr.c
new file mode 100644
index 0000000..a3eb1bb
--- /dev/null
+++ b/src/global/verify_sender_addr.c
@@ -0,0 +1,341 @@
+/*++
+/* NAME
+/*	verify_sender_addr 3
+/* SUMMARY
+/*	time-dependent probe sender addresses
+/* SYNOPSIS
+/*	#include <verify_sender_addr.h>
+/*
+/*	char	*var_verify_sender;
+/*	int	var_verify_sender_ttl;
+/*
+/*	const char *make_verify_sender_addr()
+/*
+/*	const char *valid_verify_sender_addr(addr)
+/*	const char *addr;
+/* DESCRIPTION
+/*	This module computes or verifies a constant or time-dependent
+/*	sender address for an address verification probe. The
+/*	time-dependent portion is appended to the address localpart
+/*	specified with the address_verify_sender parameter.
+/*
+/*	When the address_verify_sender parameter is empty or <>,
+/*	the sender address is always the empty address (i.e. always
+/*	time-independent).
+/*
+/*	The caller must initialize the address_verify_sender and
+/*	address_verify_sender_ttl parameter values.
+/*
+/*	make_verify_sender_addr() generates an envelope sender
+/*	address for an address verification probe.
+/*
+/*	valid_verify_sender_addr() verifies that the given address
+/*	is a valid sender address for address verification probes.
+/*	When probe sender addresses are configured to be time-dependent,
+/*	the given address is allowed to differ by +/-1 TTL unit
+/*	from the expected address.  The result is a null pointer
+/*	when no match is found. Otherwise, the result is the sender
+/*	address without the time-dependent portion; this is the
+/*	address that should be used for further delivery.
+/* DIAGNOSTICS
+/*	Fatal errors: malformed address_verify_sender value; out
+/*	of memory.
+/* 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 <errno.h>
+#include <string.h>
+#include <stdlib.h>
+
+/* Utility library. */
+
+#include <msg.h>
+#include <vstring.h>
+#include <events.h>
+#include <stringops.h>
+
+/* Global library */
+
+#include <mail_params.h>
+#include <rewrite_clnt.h>
+#include <safe_ultostr.h>
+#include <verify_sender_addr.h>
+
+/* Application-specific. */
+
+ /*
+  * We convert the time-dependent portion to a safe string (no vowels) in a
+  * reversible manner, so that we can check an incoming address against the
+  * current and +/-1 TTL time slot. This allows for some time slippage
+  * between multiple MTAs that handle mail for the same site. We use base 31
+  * so that the time stamp contains B-Z0-9. This simplifies regression tests.
+  */
+#define VERIFY_BASE		31
+
+ /*
+  * We append the time-dependent portion to the localpart of the address
+  * verification probe sender address, so that the result has the form
+  * ``fixed1variable@fixed2''. There is no delimiter between ``fixed1'' and
+  * ``variable'', because that could make "old" time stamps valid depending
+  * on how the recipient_delimiter feature is configured. The fixed text is
+  * taken from var_verify_sender with perhaps domain information appended
+  * during address canonicalization. The variable part of the address changes
+  * every var_verify_sender_ttl seconds.
+  */
+char   *var_verify_sender;		/* "bare" probe sender address */
+int     var_verify_sender_ttl;		/* time between address changes */
+
+ /*
+  * Scaffolding for stand-alone testing.
+  */
+#ifdef TEST
+#undef event_time
+#define event_time() verify_time
+static unsigned long verify_time;
+
+#endif
+
+#define VERIFY_SENDER_ADDR_EPOCH() (event_time() / var_verify_sender_ttl)
+
+ /*
+  * SLMs.
+  */
+#define STR(x) vstring_str(x)
+#define LEN(x) VSTRING_LEN(x)
+
+/* make_verify_sender_addr - generate address_verify_sender address */
+
+const char *make_verify_sender_addr(void)
+{
+    static VSTRING *verify_sender_buf;	/* the complete sender address */
+    static VSTRING *my_epoch_buf;	/* scratch space */
+    char   *my_at_domain;
+
+    /*
+     * The null sender is always time-independent.
+     */
+    if (*var_verify_sender == 0 || strcmp(var_verify_sender, "<>") == 0)
+	return ("");
+
+    /*
+     * Sanity check.
+     */
+    if (*var_verify_sender == '@')
+	msg_fatal("parameter %s: value \"%s\" must not start with '@'",
+		  VAR_VERIFY_SENDER, var_verify_sender);
+    if ((my_at_domain = strchr(var_verify_sender, '@')) != 0 && my_at_domain[1] == 0)
+	msg_fatal("parameter %s: value \"%s\" must not end with '@'",
+		  VAR_VERIFY_SENDER, var_verify_sender);
+
+    /*
+     * One-time initialization.
+     */
+    if (verify_sender_buf == 0) {
+	verify_sender_buf = vstring_alloc(10);
+	my_epoch_buf = vstring_alloc(10);
+    }
+
+    /*
+     * Start with the bare sender address.
+     */
+    vstring_strcpy(verify_sender_buf, var_verify_sender);
+
+    /*
+     * Append the time stamp to the address localpart, encoded in some
+     * non-decimal form for obscurity.
+     * 
+     * XXX It would be nice to have safe_ultostr() append-only support.
+     */
+    if (var_verify_sender_ttl > 0) {
+	/* Strip the @domain portion, if applicable. */
+	if (my_at_domain != 0)
+	    vstring_truncate(verify_sender_buf,
+			     (ssize_t) (my_at_domain - var_verify_sender));
+	/* Append the time stamp to the address localpart. */
+	vstring_sprintf_append(verify_sender_buf, "%s",
+			       safe_ultostr(my_epoch_buf,
+					    VERIFY_SENDER_ADDR_EPOCH(),
+					    VERIFY_BASE, 0, 0));
+	/* Add back the @domain, if applicable. */
+	if (my_at_domain != 0)
+	    vstring_sprintf_append(verify_sender_buf, "%s", my_at_domain);
+    }
+
+    /*
+     * Rewrite the address to canonical form.
+     */
+    rewrite_clnt_internal(MAIL_ATTR_RWR_LOCAL, STR(verify_sender_buf),
+			  verify_sender_buf);
+
+    return (STR(verify_sender_buf));
+}
+
+/* valid_verify_sender_addr - decide if address matches time window +/-1 */
+
+const char *valid_verify_sender_addr(const char *their_addr)
+{
+    static VSTRING *time_indep_sender_buf;	/* sender without time stamp */
+    ssize_t base_len;
+    unsigned long my_epoch;
+    unsigned long their_epoch;
+    char   *my_at_domain;
+    char   *their_at_domain;
+    char   *cp;
+
+    /*
+     * The null address is always time-independent.
+     */
+    if (*var_verify_sender == 0 || strcmp(var_verify_sender, "<>") == 0)
+	return (*their_addr ? 0 : "");
+
+    /*
+     * One-time initialization. Generate the time-independent address that we
+     * will return if the match is successful. This address is also used as a
+     * matching template.
+     */
+    if (time_indep_sender_buf == 0) {
+	time_indep_sender_buf = vstring_alloc(10);
+	vstring_strcpy(time_indep_sender_buf, var_verify_sender);
+	rewrite_clnt_internal(MAIL_ATTR_RWR_LOCAL, STR(time_indep_sender_buf),
+			      time_indep_sender_buf);
+    }
+
+    /*
+     * Check the time-independent sender localpart.
+     */
+    if ((my_at_domain = strchr(STR(time_indep_sender_buf), '@')) != 0)
+	base_len = my_at_domain - STR(time_indep_sender_buf);
+    else
+	base_len = LEN(time_indep_sender_buf);
+    if (strncasecmp_utf8(STR(time_indep_sender_buf), their_addr, base_len) != 0)
+	return (0);				/* sender localpart mis-match */
+
+    /*
+     * Check the time-independent domain.
+     */
+    if ((their_at_domain = strchr(their_addr, '@')) == 0 && my_at_domain != 0)
+	return (0);				/* sender domain mis-match */
+    if (their_at_domain != 0
+	&& (my_at_domain == 0
+	    || strcasecmp_utf8(their_at_domain, my_at_domain) != 0))
+	return (0);				/* sender domain mis-match */
+
+    /*
+     * Check the time-dependent portion.
+     */
+    if (var_verify_sender_ttl > 0) {
+	their_epoch = safe_strtoul(their_addr + base_len, &cp, VERIFY_BASE);
+	if ((*cp != '@' && *cp != 0)
+	    || (their_epoch == ULONG_MAX && errno == ERANGE))
+	    return (0);				/* malformed time stamp */
+	my_epoch = VERIFY_SENDER_ADDR_EPOCH();
+	if (their_epoch < my_epoch - 1 || their_epoch > my_epoch + 1)
+	    return (0);				/* outside time window */
+    }
+
+    /*
+     * No time-dependent portion.
+     */
+    else {
+	if (their_addr[base_len] != '@' && their_addr[base_len] != 0)
+	    return (0);				/* garbage after sender base */
+    }
+    return (STR(time_indep_sender_buf));
+}
+
+ /*
+  * Proof-of-concept test program. Read test address_verify_sender and
+  * address_verify_sender_ttl values from stdin, and report results that we
+  * would get on stdout.
+  */
+#ifdef TEST
+
+#include <stdlib.h>
+#include <vstream.h>
+#include <msg_vstream.h>
+#include <vstring_vstream.h>
+#include <mail_conf.h>
+#include <conv_time.h>
+
+int     main(int argc, char **argv)
+{
+    const char *verify_sender;
+    const char *valid_sender;
+
+    msg_vstream_init(argv[0], VSTREAM_ERR);
+
+    /*
+     * Prepare to talk to the address rewriting service.
+     */
+    mail_conf_read();
+    vstream_printf("using config files in %s\n", var_config_dir);
+    if (chdir(var_queue_dir) < 0)
+	msg_fatal("chdir %s: %m", var_queue_dir);
+
+    /*
+     * Parse JCL.
+     */
+    if (argc != 3)
+	msg_fatal("usage: %s address_verify_sender address_verify_sender_ttl",
+		  argv[0]);
+    var_verify_sender = argv[1];
+    if (conv_time(argv[2], &var_verify_sender_ttl, 's') == 0)
+	msg_fatal("bad time value: %s", argv[2]);
+    verify_time = time((time_t *) 0);
+
+    /*
+     * Compute the current probe sender address.
+     */
+    verify_sender = make_verify_sender_addr();
+
+    /*
+     * Check two past time slots.
+     */
+    if (var_verify_sender_ttl > 0) {
+	verify_time -= 2 * var_verify_sender_ttl;
+	vstream_printf("\"%s\" matches prev2: \"%s\"\n", verify_sender,
+	     (valid_sender = valid_verify_sender_addr(verify_sender)) != 0 ?
+		       valid_sender : "nope");
+	verify_time += var_verify_sender_ttl;
+	vstream_printf("\"%s\" matches prev1: \"%s\"\n", verify_sender,
+	     (valid_sender = valid_verify_sender_addr(verify_sender)) != 0 ?
+		       valid_sender : "nope");
+	verify_time += var_verify_sender_ttl;
+    }
+
+    /*
+     * Check the current time slot.
+     */
+    vstream_printf("\"%s\" matches self: \"%s\"\n", verify_sender,
+	     (valid_sender = valid_verify_sender_addr(verify_sender)) != 0 ?
+		   valid_sender : "nope");
+
+    /*
+     * Check two future time slots.
+     */
+    if (var_verify_sender_ttl > 0) {
+	verify_time += var_verify_sender_ttl;
+	vstream_printf("\"%s\" matches next1: \"%s\"\n", verify_sender,
+	     (valid_sender = valid_verify_sender_addr(verify_sender)) != 0 ?
+		       valid_sender : "nope");
+	verify_time += var_verify_sender_ttl;
+	vstream_printf("\"%s\" matches next2: \"%s\"\n", verify_sender,
+	     (valid_sender = valid_verify_sender_addr(verify_sender)) != 0 ?
+		       valid_sender : "nope");
+    }
+    vstream_fflush(VSTREAM_OUT);
+    exit(0);
+}
+
+#endif