From: Christian Kastner <ckk@kvr.at>
Date: Sat, 26 Dec 2015 19:03:24 +0100
Subject: Don't silently truncate commands

Commands have a maximum length. When hitting this maximum, generate an error
instead of silently truncated the command.

Bug-Debian: https://bugs.debian.org/686223
Forwarded: no
Last-Update: 2015-12-26
Index: cron/crontab.5
===================================================================
--- cron.orig/crontab.5
+++ cron/crontab.5
@@ -112,7 +112,8 @@ followed by a command, followed by a new
 The system crontab (/etc/crontab) uses the same format, except that
 the username for the command is specified after the time and
 date fields and before the command.  The fields may be separated
-by spaces or tabs.
+by spaces or tabs.  The maximum permitted length for the command field is
+998 characters.
 .PP
 Commands are executed by
 .IR cron (8)
Index: cron/entry.c
===================================================================
--- cron.orig/entry.c
+++ cron/entry.c
@@ -31,7 +31,7 @@ static char rcsid[] = "$Id: entry.c,v 2.
 
 typedef	enum ecode {
 	e_none, e_minute, e_hour, e_dom, e_month, e_dow,
-	e_cmd, e_timespec, e_username
+	e_cmd, e_timespec, e_username, e_cmd_len
 } ecode_e;
 
 static char	get_list __P((bitstr_t *, int, int, char *[], int, FILE *)),
@@ -50,6 +50,7 @@ static char *ecodes[] =
 		"bad command",
 		"bad time specifier",
 		"bad username",
+		"command too long",
 	};
 
 
@@ -311,9 +312,18 @@ load_entry(file, error_func, pw, envp)
 	/* Everything up to the next \n or EOF is part of the command...
 	 * too bad we don't know in advance how long it will be, since we
 	 * need to malloc a string for it... so, we limit it to MAX_COMMAND.
+	 *
+	 * To err on the side of caution, if the command string length is
+	 * equal to MAX_COMMAND, we will assume that the command has been
+	 * truncated and generate an error.
+	 *
 	 * XXX - should use realloc().
-	 */ 
+	 */
 	ch = get_string(cmd, MAX_COMMAND, file, "\n");
+	if (strnlen(cmd, MAX_COMMAND) == MAX_COMMAND - 1) {
+		ecode = e_cmd_len;
+		goto eof;
+	}
 
 	/* a file without a \n before the EOF is rude, so we'll complain...