nnrpd: Reject articles with invalid dot-stuffing

Enforce correctly formatted articles at injection time.

close #286

doc/pod/news.pod

@@ -77,6 +77,13 @@ preserves the leading initial dot at injection time).
 
 =item *
 
+B<nnrpd> now rejects articles with invalid dot-stuffing (that is to say when
+a dot at the beginning of a line is not doubled) as it is a violation of the
+NNTP protocol.  (B<innd> still goes on accepting and propagating such articles
+as they have already been injected and propagated.)
+
+=item *
+
 Fixed the computation of the Bytes header field by B<pullnews> (in header-only
 mode with the B<-B> flag).
 

nnrpd/commands.c

@@ -620,7 +620,7 @@ CMDpost(int ac, char *av[])
     static int size;
     char *p, *q;
     char *end;
-    int longline;
+    int longline, missingdotstuffing;
     READTYPE r;
     int i;
     long l;
@@ -748,6 +748,7 @@ CMDpost(int ac, char *av[])
     end = &article[size];
 
     longline = 0;
+    missingdotstuffing = 0;
     for (l = 1;; l++) {
         size_t len;
         const char *line;
@@ -797,18 +798,20 @@ CMDpost(int ac, char *av[])
             p = i + article;
         }
 
-        /* Reverse any byte-stuffing. */
+        /* Reverse any dot-stuffing. */
         if (*line == '.') {
             ++line;
             --len;
+            if (*line != '.' && missingdotstuffing == 0)
+                missingdotstuffing = l;
         }
         memcpy(p, line, len);
         p += len;
         *p++ = '\n';
         *p = '\0';
     }
 
-    if (longline) {
+    if (longline > 0) {
         warn("%s too long in post", Client.host);
         Reply("%d Line %d too long\r\n",
               ihave ? NNTP_FAIL_IHAVE_REJECT : NNTP_FAIL_POST_REJECT,
@@ -817,6 +820,14 @@ CMDpost(int ac, char *av[])
         return;
     }
 
+    if (missingdotstuffing > 0) {
+        Reply("%d Line %d without its initial dot doubled (dot-stuffing)\r\n",
+              ihave ? NNTP_FAIL_IHAVE_REJECT : NNTP_FAIL_POST_REJECT,
+              missingdotstuffing);
+        POSTrejected++;
+        return;
+    }
+
     /* Send the article to the server. */
     response = ARTpost(article, idbuff, &permanent);
     if (response == NULL) {