From 81c42da8eab8db75b274dfad67c774e1de33b4b7 Mon Sep 17 00:00:00 2001
From: deraadt <>
Date: Mon, 5 Aug 1996 00:34:46 +0000
Subject: if port 20 incoming, kill it and try again

---
 src/lib/libc/net/rcmd.c | 9 +++++++++
 1 file changed, 9 insertions(+)

(limited to 'src/lib')

diff --git a/src/lib/libc/net/rcmd.c b/src/lib/libc/net/rcmd.c
index 643604f3b3..86f35664e4 100644
--- a/src/lib/libc/net/rcmd.c
+++ b/src/lib/libc/net/rcmd.c
@@ -153,6 +153,7 @@ rcmd(ahost, rport, locuser, remuser, cmd, fd2p)
 			(void)close(s2);
 			goto bad;
 		}
+again:
 		FD_ZERO(&reads);
 		FD_SET(s, &reads);
 		FD_SET(s2, &reads);
@@ -170,6 +171,14 @@ rcmd(ahost, rport, locuser, remuser, cmd, fd2p)
 			goto bad;
 		}
 		s3 = accept(s2, (struct sockaddr *)&from, &len);
+		/*
+		 * XXX careful for ftp bounce attacks. If discovered, shut them
+		 * down and check for the real auxiliary channel to connect.
+		 */
+		if (from.sin_family == AF_INET && from.sin_port == htons(20)) {
+			close(s3);
+			goto again;
+		}
 		(void)close(s2);
 		if (s3 < 0) {
 			(void)fprintf(stderr,
-- 
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