Fixed cf-execd SMTP mock and reapplied dot-stuffing

cf-execd/cf-execd-runner.c

@@ -797,7 +797,11 @@ static void MailResult(const ExecConfig *config, const char *file)
         {
             continue;
         }
-        if (send(sd, line, n_read, 0) == -1 ||
+        /* Dot-stuff lines starting with '.' (RFC 5321, section 4.5.2), or a
+         * lone "." in the output would end the DATA section early and the
+         * remaining lines would be read by the server as SMTP commands. */
+        if ((line[0] == '.' && send(sd, ".", 1, 0) == -1) ||
+            send(sd, line, n_read, 0) == -1 ||
             send(sd, "\r\n", 2, 0) == -1)
         {
             Log(LOG_LEVEL_ERR, "Error while sending mail to mailserver "

tests/acceptance/25_cf-execd/cf-execd-rpl-functions.c

@@ -66,14 +66,29 @@ static void *FeedSmtpDirectives(void *data)
     COND_SEND("250 to@test.com... Recipient ok\r\n");
     COND_RECV(recvbuf);
     COND_SEND("354 Enter mail, end with \".\" on a line by itself\r\n");
-    while (true)
+    /* The end of DATA marker may be split across several recv() calls, so
+     * track the last bytes of the stream rather than each chunk alone. */
+    char last[5] = { '\0', '\0', '\0', '\r', '\n' };
+    bool done = false;
+    while (!done)
     {
         COND_RECV(recvbuf);
-        if ((rcvd == 3 && memcmp(recvbuf + rcvd - 3, ".\r\n", 3) == 0) ||
-            (rcvd > 3 && memcmp(recvbuf + rcvd - 4, "\n.\r\n", 4) == 0))
+        if (rcvd == 0)
         {
-            break;
+            Log(LOG_LEVEL_ERR, "Connection closed before end of DATA in %s:%i", __FILE__, __LINE__);
+            return NULL;
         }
+        /* It's a sliding window:
+         * For each received byte we left shift the buffer and append the new
+         * byte to the end. The client waits for our reply after sending the
+         * End-of-Data marker, so the marker can only appear at the end of
+         * the received data. */
+        for (int i = 0; i < rcvd; i++)
+        {
+            memmove(last, last + 1, sizeof(last) - 1);
+            last[sizeof(last) - 1] = recvbuf[i];
+        }
+        done = (memcmp(last, "\r\n.\r\n", sizeof(last)) == 0);
     }
     COND_SEND("250 Message accepted for delivery\r\n");
     COND_RECV(recvbuf);

tests/acceptance/25_cf-execd/mail_dot_line.cf

@@ -0,0 +1,44 @@
+# Tests that a line consisting of a single "." in the agent output is
+# dot-stuffed by cf-execd, so it does not end the SMTP DATA section early.
+body common control
+{
+  inputs => { "../default.sub.cf", "mailfilter_common.cf.sub" };
+  bundlesequence => { default($(this.promise_filename)) };
+}
+
+bundle agent init
+{
+  vars:
+    "reports" slist => { "CorrectString1$(const.n).$(const.n)CorrectString2" };
+    "includes" slist => {};
+    "excludes" slist => {};
+
+  methods:
+    "any"
+      usebundle => prepare_mailfilter_test(
+        @(reports), @(includes), @(excludes)
+      );
+}
+
+bundle agent test
+{
+  meta:
+    "test_soft_fail"
+      string => "windows",
+      meta => { "ENT-10215" };
+}
+
+bundle agent check
+{
+  vars:
+    "wanted" slist => { 'CorrectString1\r
+\.\.\r
+CorrectString2' };
+    "empty_list" slist => {};
+
+  methods:
+    "any"
+      usebundle => check_cf_execd_mail(
+        @(wanted), @(empty_list), $(this.promise_filename)
+      );
+}