[krbdev.mit.edu #6773] rshd's limit on login name length is unnecessarily low

[The RT System itself via RT]

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Date: Thu, 9 Sep 2010 18:40:18 -0400
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To: krb5-bugs at mit.edu
Subject: rshd's limit on login name length is unnecessarily low
From: nalin at redhat.com
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>Submitter-Id:	net
>Originator:	
>Organization:
>Confidential:	no
>Synopsis:	rshd's limit on login name length is unnecessarily low
>Severity:	non-critical
>Priority:	low
>Category:	krb5-appl
>Class:		change-request
>Release:	1.0.1
>Environment:
	
System: Linux blade.bos.redhat.com 2.6.34-43.fc14.x86_64 #1 SMP Thu Jun 17 10:32:12 UTC 2010 x86_64 x86_64 x86_64 GNU/Linux
Architecture: x86_64

>Description:
	Rik Brown reported that kshd limits user names to 16 chars, while
	the more practical limit of the size of the user name field in
	a utmp entry is typically higher, at least on glibc systems.
>How-To-Repeat:
	Create a temporary user with 'useradd' with a name more than 16
	chars long, but less than 32 (the limit I get here).  Try to run
	"printenv USER" via rsh.
>Fix:
	Here's a revised version of Rik's patch from
	https://bugzilla.redhat.com/show_bug.cgi?id=611713:

Index: bsd/krshd.c
===================================================================
--- bsd/krshd.c	(revision 3307)
+++ bsd/krshd.c	(working copy)
@@ -171,7 +171,14 @@
 
 
 
+#ifdef HAVE_UTMP_H
+#include <utmp.h>
+#endif
 
+#ifndef UT_NAMESIZE	/* linux defines it directly in <utmp.h> */
+#define	UT_NAMESIZE	sizeof(((struct utmp *)0)->ut_name)
+#endif
+
 #define MAXRETRIES 4
 
 krb5_context bsd_context;
@@ -438,7 +445,7 @@
 #include <tmpdir.h>
 char tmpdir[64] = "TMPDIR=";
 #else
-char	username[20] = "USER=";
+char	username[UT_NAMESIZE + 6] = "USER=";
 #endif
 
 char	homedir[64] = "HOME=";
@@ -493,7 +500,7 @@
 #define NCARGS 4096
 #endif
 
-#define NMAX   16 
+#define NMAX   UT_NAMESIZE
 
 int pid;
 char locuser[NMAX+1];