From: Christian Kastner <ckk@kvr.at>
Date: Fri, 15 Jan 2016 23:05:10 +0100
Subject: Selective logging

This implements a fine-grained control over what the cron daemon logs when it
executes jobs. This is driven via the '-L' command line option, which accepts a
bitmask of values for logging the start, end, failure and PID of jobs. The
following things can be logged:
    * Start of cron jobs
    * End of cron jobs
    * Failed jobs
    * Include PID of cron job in messages

The default is to log the start of jobs. 

Initially contributed by Steve Fosdick <dbugs@pelvoux.nildram.co.uk>.

Bug-Debian: https://bugs.debian.org/271747
Bug-Debian: https://bugs.debian.org/318247
Forwarded: no
Last-Update: 2016-01-15
---
 cron.8       | 25 ++++++++++++++++++++++++-
 cron.c       |  8 ++++++--
 cron.h       |  9 ++++++++-
 do_command.c | 56 ++++++++++++++++++++++++++++++++++++++++----------------
 4 files changed, 78 insertions(+), 20 deletions(-)

diff --git a/cron.8 b/cron.8
index 23a50c0..77cb100 100644
--- a/cron.8
+++ b/cron.8
@@ -25,6 +25,8 @@ cron \- daemon to execute scheduled commands (Vixie Cron)
 cron
 .RB [ \-f ]
 .RB [ \-l ]
+.RB [ \-L
+.IR loglevel ]
 .SH DESCRIPTION
 .I cron
 is started automatically from /etc/init.d on entering multi-user
@@ -38,6 +40,27 @@ Stay in foreground mode, don't daemonize.
 Enable LSB compliant names for /etc/cron.d files.  This setting, however, does
 not affect the parsing of files under /etc/cron.hourly, /etc/cron.daily,
 /etc/cron.weekly or /etc/cron.monthly.
+.TP
+.B \-L loglevel
+Tell cron what to log about \fBjobs\fR (errors are logged regardless of this
+value) as the sum of the following values:
+.br
+.RS 12
+.IP \fB1\fR
+will log the start of all cron jobs
+.IP \fB2\fR
+will log the end of all cron jobs
+.IP \fB4\fR
+will log all failed jobs (exit status != 0)
+.IP \fB8\fR
+will log the process number of all cron jobs
+.RE
+.IP
+The default is to log the start of all jobs (1).
+Logging will be disabled if
+.I levels
+is set to zero (0).
+A value of fifteen (15) will select all options.
 .SH NOTES
 .PP
 .I cron
@@ -272,7 +295,7 @@ daemon.  This file determines whether
 will read the system's environment variables and makes it possible to add
 additional options to the
 .I cron
-program before it is executed, for example to define how
+program before it is executed, either to configure its logging or to define how
 it will treat the files under /etc/cron.d.
 
 .SH "SEE ALSO"
diff --git a/cron.c b/cron.c
index 53a6dae..84b19e6 100644
--- a/cron.c
+++ b/cron.c
@@ -447,9 +447,9 @@ sighup_handler(int x) {
 
 
 #if DEBUGGING
-const char *getoptarg = "flx:";
+const char *getoptarg = "flL:x:";
 #else
-const char *getoptarg = "fl";
+const char *getoptarg = "flL:";
 #endif
 
 static void
@@ -461,6 +461,7 @@ parse_args(argc, argv)
 
 	stay_foreground = 0;
 	lsbsysinit_mode = 0;
+	log_level = 1;
 
 	while (EOF != (argch = getopt(argc, argv, getoptarg))) {
 		switch (argch) {
@@ -472,6 +473,9 @@ parse_args(argc, argv)
 		case 'l':
 			lsbsysinit_mode = 1;
 			break;
+		case 'L':
+			log_level = atoi(optarg);
+			break;
 #if DEBUGGING
 		case 'x':
 			if (!set_debug_flags(optarg))
diff --git a/cron.h b/cron.h
index 30b36e9..6c866a4 100644
--- a/cron.h
+++ b/cron.h
@@ -138,6 +138,12 @@
 
 typedef int time_min;
 
+/* Log levels */
+#define	CRON_LOG_JOBSTART	0x01
+#define	CRON_LOG_JOBEND		0x02
+#define	CRON_LOG_JOBFAILED	0x04
+#define	CRON_LOG_JOBPID		0x08
+
 #define SECONDS_PER_MINUTE 60
 
 #define	FIRST_MINUTE	0
@@ -210,7 +216,6 @@ typedef	struct _cron_db {
 	time_t		sysd_mtime;     /* last modtime on system crondir */
 } cron_db;
 
-
 void		set_cron_uid __P((void)),
 		set_cron_cwd __P((void)),
 		load_database __P((cron_db *)),
@@ -294,6 +299,7 @@ static long GMToff;
 
 int	stay_foreground;
 int	lsbsysinit_mode;
+int	log_level;
 
 char	cron_default_mail_charset[MAX_ENVSTR] = "";
 
@@ -310,6 +316,7 @@ extern	char	*copyright[],
 		*DowNames[],
 		*ProgramName;
 extern	int	lsbsysinit_mode;
+extern	int	log_level;
 extern	int	LineNumber;
 extern	time_t	StartTime;
 extern  time_min timeRunning;
diff --git a/do_command.c b/do_command.c
index 923e507..e024995 100644
--- a/do_command.c
+++ b/do_command.c
@@ -131,6 +131,7 @@ child_process(e, u)
 	register char	*input_data;
 	char		*usernm, *mailto;
 	int		children = 0;
+	pid_t		job_pid;
 #if defined(USE_PAM)
 	int		retcode = 0;
 #endif
@@ -228,7 +229,7 @@ child_process(e, u)
 
 	/* fork again, this time so we can exec the user's command.
 	 */
-	switch (fork()) {
+	switch (job_pid = fork()) {
 	case -1:
 		log_it("CRON",getpid(),"error","can't fork");
 		exit(ERROR_EXIT);
@@ -242,14 +243,12 @@ child_process(e, u)
 		 * the actual user command shell was going to get and the
 		 * PID is part of the log message.
 		 */
-		/*local*/{
+		if ((log_level & CRON_LOG_JOBSTART) && ! (log_level & CRON_LOG_JOBPID)) {
 			char *x = mkprints((u_char *)e->cmd, strlen(e->cmd));
-
 			log_it(usernm, getpid(), "CMD", x);
 			free(x);
 		}
-
-		/* that's the last thing we'll log.  close the log files.
+		/* nothing to log from now on. close the log files.
 		 */
 		log_close();
 
@@ -357,6 +356,16 @@ child_process(e, u)
 		break;
 	default:
 		/* parent process */
+		/* write a log message if we want the parent and child
+		 * PID values
+		 */
+		if ( (log_level & CRON_LOG_JOBSTART) && (log_level & CRON_LOG_JOBPID)) {
+			char logcmd[MAX_COMMAND + 8];
+			snprintf(logcmd, sizeof(logcmd), "[%d] %s", (int) job_pid, e->cmd);
+			char *x = mkprints((u_char *)logcmd, strlen(logcmd));
+			log_it(usernm, getpid(), "CMD", x);
+			free(x);
+		}
 		break;
 	}
 
@@ -458,17 +467,19 @@ child_process(e, u)
 		Debug(DPROC, ("[%d] grandchild #%d finished, status=%04x\n",
 			getpid(), pid, WEXITSTATUS(waiter)))
 
-		if (WIFEXITED(waiter) && WEXITSTATUS(waiter)) {
-			status = waiter;
-			snprintf(msg, 256, "grandchild #%d failed with exit "
-				"status %d", pid, WEXITSTATUS(waiter));
-			log_it("CRON", getpid(), "error", msg);
-		} else if (WIFSIGNALED(waiter)) {
-			status = waiter;
-			snprintf(msg, 256, "grandchild #%d terminated by signal"
-				" %d%s", pid, WTERMSIG(waiter),
-				WCOREDUMP(waiter) ? ", dumped core" : "");
-			log_it("CRON", getpid(), "error", msg);
+		if (log_level & CRON_LOG_JOBFAILED) {
+			if (WIFEXITED(waiter) && WEXITSTATUS(waiter)) {
+				status = waiter;
+				snprintf(msg, 256, "grandchild #%d failed with exit "
+					"status %d", pid, WEXITSTATUS(waiter));
+				log_it("CRON", getpid(), "error", msg);
+			} else if (WIFSIGNALED(waiter)) {
+				status = waiter;
+				snprintf(msg, 256, "grandchild #%d terminated by signal"
+					" %d%s", pid, WTERMSIG(waiter),
+					WCOREDUMP(waiter) ? ", dumped core" : "");
+				log_it("CRON", getpid(), "error", msg);
+			}
 		}
 	}
 
@@ -616,6 +627,19 @@ child_process(e, u)
 mail_finished:
 	fclose(tmpout);
 
+	if (log_level & CRON_LOG_JOBEND) {
+		char *x;
+		if (log_level & CRON_LOG_JOBPID) {
+			char logcmd[MAX_COMMAND + 8];
+			snprintf(logcmd, sizeof(logcmd), "[%d] %s", (int) job_pid, e->cmd);
+			x = mkprints((u_char *)logcmd, strlen(logcmd));
+		} else {
+			x = mkprints((u_char *)e->cmd, strlen(e->cmd));
+		}
+		log_it(usernm, job_pid, "END", x);
+		free(x);
+	}
+
 #if defined(USE_PAM)
 	pam_setcred(pamh, PAM_DELETE_CRED | PAM_SILENT);
 	retcode = pam_close_session(pamh, PAM_SILENT);