After receiving a connection and doing a reverse

lookup on the incoming IP, do a forward lookup on
the result and make sure that the IP is in the
resulting list.  If it's not, put the IP number
in utmp/wtmp instead of the rogue name.

Stolen from: rlogind
Suggested by: sef

1 files changed, 18 insertions, 2 deletions

diff --git a/libexec/telnetd/telnetd.c b/libexec/telnetd/telnetd.c
index 37564e3..c825eab 100644
--- a/libexec/telnetd/telnetd.c
+++ b/libexec/telnetd/telnetd.c
@@ -42,7 +42,7 @@ static const char copyright[] =
 static char sccsid[] = "@(#)telnetd.c	8.2 (Berkeley) 12/15/93";
 #endif
 static const char rcsid[] =
-	"$Id: telnetd.c,v 1.14 1998/04/26 06:51:36 phk Exp $";
+	"$Id: telnetd.c,v 1.15 1998/12/16 06:04:29 peter Exp $";
 #endif /* not lint */
 
 #include "telnetd.h"
@@ -821,7 +821,23 @@ doit(who)
          Please contact your net administrator");
 	} else if (hp &&
 	    (strlen(hp->h_name) <= ((utmp_len < 0) ? -utmp_len : utmp_len))) {
-		host = hp->h_name;
+		strncpy(remote_host_name, hp->h_name,
+			sizeof(remote_host_name)-1);
+		hp = gethostbyname(remote_host_name);
+		if (hp == NULL)
+			host = inet_ntoa(who->sin_addr);
+		else for (; ; hp->h_addr_list++) {
+			if (hp->h_addr_list[0] == NULL) {
+				/* End of list - ditch it */
+				host = inet_ntoa(who->sin_addr);
+				break;
+			}
+			if (!bcmp(hp->h_addr_list[0], (caddr_t)&who->sin_addr,
+			    sizeof(who->sin_addr))) {
+				host = hp->h_name;
+				break;		/* OK! */
+			}
+		}
 	} else {
 		host = inet_ntoa(who->sin_addr);
 	}