From ce7d5bf0a43d147f8502e6424cd523b56adf5599 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20Poho=C5=99elsk=C3=BD?= <opohorel@redhat.com>
Date: Mon, 26 Sep 2022 16:51:41 +0200
Subject: [PATCH] Add -n option for crontab entries

The -n option causes no mail to be sent
when the command finishes successfully.

These kind of options are already supported in *BSD;
in fact, this is a port of a patch from NetBSD [1].

This was requested in [2].

[1]: NetBSD/src@666eac5
[2]: https://bugzilla.redhat.com/show_bug.cgi?id=1591763
---
 src/do_command.c | 32 +++++++++++++++++++++++++++++---
 src/entry.c      | 31 +++++++++++++++++++++++++++++++
 src/funcs.h      |  1 +
 src/popen.c      | 33 ++++++++++++++++++++++++++++++---
 src/structs.h    |  1 +
 5 files changed, 92 insertions(+), 6 deletions(-)

diff --git a/src/do_command.c b/src/do_command.c
index 87f996f..6a3886a 100644
--- a/src/do_command.c
+++ b/src/do_command.c
@@ -94,6 +94,7 @@ static int child_process(entry * e, char **jobenv) {
 	char mailfrom_expanded[MAX_EMAILSTR];
 	int children = 0;
 	pid_t pid = getpid();
+	pid_t jobpid = -1;
 	struct sigaction sa;
 
 	/* Ignore SIGPIPE as we will be writing to pipes and do not want to terminate
@@ -199,7 +200,7 @@ static int child_process(entry * e, char **jobenv) {
 
 	/* fork again, this time so we can exec the user's command.
 	 */
-	switch (fork()) {
+	switch (jobpid = fork()) {
 	case -1:
 		log_it("CRON", pid, "CAN'T FORK", "child_process", errno);
 		return ERROR_EXIT;
@@ -552,10 +553,35 @@ static int child_process(entry * e, char **jobenv) {
 				}
 #endif
 			}
-			/* only close pipe if we opened it -- i.e., we're
-			 * mailing...
+			/* if -n option was specified, abort the sending
+			 * now when we read all of the command output
+			 * and thus can wait for it's exit status
 			 */
+			if (mail && e->flags & MAIL_WHEN_ERR) {
+				int jobstatus = -1;
+				if (jobpid > 0) {
+					while (waitpid(jobpid, &jobstatus, WNOHANG) == -1) {
+						if (errno == EINTR) continue;
+						log_it("CRON", getpid(), "error", "invalid job pid", errno);
+						break;
+					}
+				} else {
+					log_it("CRON", getpid(), "error", "invalid job pid", 0);
+				}
 
+				/* if everything went well, -n is set, and we have mail,
+				 * we won't be mailing – so shoot the messenger!
+				 */
+				if (WIFEXITED(jobstatus) && WEXITSTATUS(jobstatus) == EXIT_SUCCESS) {
+					Debug(DPROC, ("[%ld] aborting pipe to mail\n", (long)getpid()));
+					status = cron_pabort(mail);
+					mail = NULL;
+				}
+			}
+
+			/* only close pipe if we opened it -- i.e., we're (still)
+			 * mailing...
+			 */
 			if (mail) {
 				Debug(DPROC, ("[%ld] closing pipe to mail\n", (long) getpid()));
 					/* Note: the pclose will probably see
diff --git a/src/entry.c b/src/entry.c
index bb7cb62..9e199fe 100644
--- a/src/entry.c
+++ b/src/entry.c
@@ -417,6 +417,37 @@ entry *load_entry(FILE * file, void (*error_func) (), struct passwd *pw,
 
 	Debug(DPARS, ("load_entry()...about to parse command\n"));
 
+	/* If the first character of the command is '-', it is a cron option. */
+	ch = get_char(file);
+	while (ch == '-') {
+		switch (ch = get_char(file)) {
+			case 'n':
+				/* only allow user to set the option once */
+				if ((e->flags & MAIL_WHEN_ERR) == MAIL_WHEN_ERR) {
+					ecode = e_option;
+					goto eof;
+				}
+				e->flags |= MAIL_WHEN_ERR;
+				break;
+
+			default:
+				ecode = e_option;
+				goto eof;
+		}
+
+		ch = get_char(file);
+		if (ch != '\t' && ch != ' ') {
+			ecode = e_option;
+			goto eof;
+		}
+		Skip_Blanks(ch, file);
+		if (ch == EOF || ch == '\n') {
+			ecode = e_cmd;
+			goto eof;
+		}
+	}
+	unget_char(ch, file);
+
 	/* 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.
diff --git a/src/funcs.h b/src/funcs.h
index dea737e..427e027 100644
--- a/src/funcs.h
+++ b/src/funcs.h
@@ -67,6 +67,7 @@ int		load_database(cron_db *),
 		swap_uids_back(void),
 		load_env(char *, FILE *),
 		env_set_from_environ(char ***envpp),
+		cron_pabort(FILE *),
 		cron_pclose(FILE *),
 		glue_strings(char *, size_t, const char *, const char *, char),
 		strcmp_until(const char *, const char *, char),
diff --git a/src/popen.c b/src/popen.c
index 4397264..3043eb6 100644
--- a/src/popen.c
+++ b/src/popen.c
@@ -167,7 +167,7 @@ FILE *cron_popen(char *program, const char *type, struct passwd *pw, char **jobe
 	return (iop);
 }
 
-int cron_pclose(FILE * iop) {
+static int cron_finalize(FILE * iop, int sig) {
 	int fdes;
 	sigset_t oset, nset;
 	WAIT_T stat_loc;
@@ -180,7 +180,12 @@ int cron_pclose(FILE * iop) {
 	fdes = fileno(iop);
 	if (pids == NULL || fdes >= fds || pids[fdes] == 0L)
 		return (-1);
-	(void) fclose(iop);
+	
+	if (!sig) {
+		(void) fclose(iop);
+	} else if (kill(pids[fdes], sig) == -1) {
+		return -1;
+	}
 
 	sigemptyset(&nset);
 	sigaddset(&nset, SIGINT);
@@ -189,6 +194,28 @@ int cron_pclose(FILE * iop) {
 	(void) sigprocmask(SIG_BLOCK, &nset, &oset);
 	while ((pid = wait(&stat_loc)) != pids[fdes] && pid != -1) ;
 	(void) sigprocmask(SIG_SETMASK, &oset, NULL);
+	
+	if (sig) {
+		(void) fclose(iop);
+	}
 	pids[fdes] = 0;
-	return (pid == -1 ? -1 : WEXITSTATUS(stat_loc));
+
+	if (pid < 0) {
+		return pid;
+	}
+
+	if (WIFEXITED(stat_loc)) {
+		return WEXITSTATUS(stat_loc);
+	} else {
+		return WTERMSIG(stat_loc);
+	}
+}
+
+int cron_pclose(FILE * iop) {
+	return cron_finalize(iop, 0);
+}
+
+int cron_pabort(FILE * iop) {
+	int esig = cron_finalize(iop, SIGKILL);
+	return esig == SIGKILL ? 0 : esig;
 }
diff --git a/src/structs.h b/src/structs.h
index 6d3c15b..d930da5 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -48,6 +48,7 @@ typedef	struct _entry {
 #define	DOW_STAR	0x08
 #define	WHEN_REBOOT	0x10
 #define	DONT_LOG	0x20
+#define	MAIL_WHEN_ERR	0x40
 } entry;
 
 			/* the crontab database will be a list of the