14358 Cron should support randomized delay

Reviewed by: Andy Fiddaman <andy@omnios.org>
Approved by: Robert Mustacchi <rm@fingolfin.org>

8 files changed, 106 insertions, 50 deletions

diff --git a/usr/src/cmd/cron/Makefile b/usr/src/cmd/cron/Makefile
index 8e9a95060d..9a555562d8 100644
--- a/usr/src/cmd/cron/Makefile
+++ b/usr/src/cmd/cron/Makefile
@@ -41,8 +41,7 @@ CERRWARN +=	$(CNOWARN_UNINIT)
 CERRWARN +=	-_gcc=-Wno-unused-variable
 CERRWARN +=	-_gcc=-Wno-unused-value
 
-# not linted
-SMATCH=off
+SMOFF +=	signed_integer_overflow_check,all_func_returns
 
 ROOTVAR =	$(ROOT)/var
 
diff --git a/usr/src/cmd/cron/atq.c b/usr/src/cmd/cron/atq.c
index 99ce381440..d2e8b973a7 100644
--- a/usr/src/cmd/cron/atq.c
+++ b/usr/src/cmd/cron/atq.c
@@ -6,7 +6,7 @@
  */
 
 /*	Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T	*/
-/*	  All Rights Reserved  	*/
+/*	  All Rights Reserved  */
 
 
 /*
@@ -93,14 +93,14 @@ main(int argc, char **argv)
 
 	(void) setlocale(LC_ALL, "");
 	pp = getpwuid(getuid());
-	pr.pw_uid = pp->pw_uid;
-	pr.pw_name = pp->pw_name;
-
 	if (pp == NULL)
 		atabort(INVALIDUSER);
 	if (!allowed(pp->pw_name, ATALLOW, ATDENY))
 		atabort(NOTALLOWED);
 
+	pr.pw_uid = pp->pw_uid;
+	pr.pw_name = pp->pw_name;
+
 	/*
 	 * Interpret command line flags if they exist.
 	 */
diff --git a/usr/src/cmd/cron/cron.c b/usr/src/cmd/cron/cron.c
index faefcbebd0..a34d98766e 100644
--- a/usr/src/cmd/cron/cron.c
+++ b/usr/src/cmd/cron/cron.c
@@ -27,6 +27,7 @@
  * Copyright (c) 2014 Gary Mills
  * Copyright (c) 2016 by Delphix. All rights reserved.
  * Copyright 2019 OmniOS Community Edition (OmniOSce) Association.
+ * Copyright 2022 Sebastian Wiedenroth
  */
 
 /*	Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T	*/
@@ -194,6 +195,7 @@ struct event {
 			struct shared *tz;	/* timezone of this event */
 			struct shared *home;	/* directory for this event */
 			struct shared *shell;	/* shell for this event */
+			uint32_t max_random_delay;	/* max. random delay */
 		} ct;
 		struct { /* for at events */
 			short exists;	/* for revising at events	*/
@@ -1130,7 +1132,9 @@ readcron(struct usr *u, time_t reftime)
 	struct shared *tz = NULL;
 	struct shared *home = NULL;
 	struct shared *shell = NULL;
+	uint32_t max_random_delay = 0;
 	int lineno = 0;
+	const char *errstr;
 
 	/* read the crontab file */
 	cte_init();		/* Init error handling */
@@ -1204,6 +1208,23 @@ readcron(struct usr *u, time_t reftime)
 			continue;
 		}
 
+		if (strncmp(&line[cursor], ENV_RANDOM_DELAY,
+		    strlen(ENV_RANDOM_DELAY)) == 0) {
+			if ((tmp = strchr(&line[cursor], '\n')) != NULL) {
+				*tmp = '\0';
+			}
+
+			max_random_delay = strtonum(
+			    &line[cursor + strlen(ENV_RANDOM_DELAY)], 0,
+			    UINT32_MAX / 60, &errstr);
+			if (errstr != NULL) {
+				cte_add(lineno, line);
+				break;
+			}
+
+			continue;
+		}
+
 		e = xmalloc(sizeof (struct event));
 		e->etype = CRONEVENT;
 
@@ -1258,6 +1279,8 @@ again:
 		e->of.ct.shell = dup_shared(shell);
 		/* set the home of this entry */
 		e->of.ct.home = dup_shared(home);
+		/* set the maximum random delay */
+		e->of.ct.max_random_delay = max_random_delay;
 		/* have the event point to it's owner	*/
 		e->u = u;
 		/* insert this event at the front of this user's event list */
@@ -1848,18 +1871,22 @@ recalc:
 static time_t
 next_time(struct event *e, time_t tflag)
 {
-	if (e->of.ct.tz != NULL) {
-		time_t ret;
+	time_t ret;
 
+	if (e->of.ct.tz != NULL) {
 		(void) putenv((char *)get_obj(e->of.ct.tz));
 		tzset();
 		ret = tz_next_time(e, tflag);
 		(void) putenv(tzone);
 		tzset();
-		return (ret);
 	} else {
-		return (tz_next_time(e, tflag));
+		ret = tz_next_time(e, tflag);
+	}
+
+	if (e->of.ct.max_random_delay > 0) {
+		ret += arc4random_uniform(e->of.ct.max_random_delay * 60 - 1);
 	}
+	return (ret);
 }
 
 /*
diff --git a/usr/src/cmd/cron/cron.h b/usr/src/cmd/cron/cron.h
index e071209673..b2e241f202 100644
--- a/usr/src/cmd/cron/cron.h
+++ b/usr/src/cmd/cron/cron.h
@@ -25,6 +25,7 @@
 
 /*
  * Copyright 2019 OmniOS Community Edition (OmniOSce) Association.
+ * Copyright 2022 Sebastian Wiedenroth
  */
 
 #ifndef	_CRON_H
@@ -101,9 +102,10 @@ typedef enum {
 
 #define	SHELL		"/usr/bin/sh"	/* shell to execute */
 
-#define	ENV_SHELL	"SHELL="
-#define	ENV_TZ		"TZ="
-#define	ENV_HOME	"HOME="
+#define	ENV_SHELL		"SHELL="
+#define	ENV_TZ			"TZ="
+#define	ENV_HOME		"HOME="
+#define	ENV_RANDOM_DELAY	"RANDOM_DELAY="
 
 #define	CTLINESIZE	1000	/* max chars in a crontab line */
 
diff --git a/usr/src/cmd/cron/crontab.c b/usr/src/cmd/cron/crontab.c
index d85c9c554b..4ff985240e 100644
--- a/usr/src/cmd/cron/crontab.c
+++ b/usr/src/cmd/cron/crontab.c
@@ -27,6 +27,7 @@
 
 /*
  * Copyright 2020 OmniOS Community Edition (OmniOSce) Association.
+ * Copyright 2022 Sebastian Wiedenroth
  */
 
 #include <sys/types.h>
@@ -96,6 +97,7 @@
 #define	BAD_TZ	"Timezone unrecognized in: %s"
 #define	BAD_SHELL	"Invalid shell specified: %s"
 #define	BAD_HOME	"Unable to access directory: %s\t%s\n"
+#define	BAD_RAND_DELAY	"Invalid delay: %s"
 
 extern int	per_errno;
 
@@ -428,6 +430,7 @@ copycron(FILE *fp)
 	char pid[6], *tnam_end;
 	int t;
 	char buf[LINE_MAX];
+	const char *errstr;
 	cferror_t cferr;
 
 	sprintf(pid, "%-5d", getpid());
@@ -460,7 +463,7 @@ copycron(FILE *fp)
 		if (strncmp(&line[cursor], ENV_TZ, strlen(ENV_TZ)) == 0) {
 			char *x;
 
-			strncpy(buf, &line[cursor + strlen(ENV_TZ)],
+			(void) strncpy(buf, &line[cursor + strlen(ENV_TZ)],
 			    sizeof (buf));
 			if ((x = strchr(buf, '\n')) != NULL)
 				*x = '\0';
@@ -476,7 +479,7 @@ copycron(FILE *fp)
 		    strlen(ENV_SHELL)) == 0) {
 			char *x;
 
-			strncpy(buf, &line[cursor + strlen(ENV_SHELL)],
+			(void) strncpy(buf, &line[cursor + strlen(ENV_SHELL)],
 			    sizeof (buf));
 			if ((x = strchr(buf, '\n')) != NULL)
 				*x = '\0';
@@ -492,7 +495,7 @@ copycron(FILE *fp)
 		    strlen(ENV_HOME)) == 0) {
 			char *x;
 
-			strncpy(buf, &line[cursor + strlen(ENV_HOME)],
+			(void) strncpy(buf, &line[cursor + strlen(ENV_HOME)],
 			    sizeof (buf));
 			if ((x = strchr(buf, '\n')) != NULL)
 				*x = '\0';
@@ -504,6 +507,25 @@ copycron(FILE *fp)
 				    strerror(errno));
 				continue;
 			}
+		} else if (strncmp(&line[cursor], ENV_RANDOM_DELAY,
+		    strlen(ENV_RANDOM_DELAY)) == 0) {
+			char *x;
+
+			(void) strncpy(buf,
+			    &line[cursor + strlen(ENV_RANDOM_DELAY)],
+			    sizeof (buf));
+			if ((x = strchr(buf, '\n')) != NULL)
+				*x = '\0';
+
+			(void) strtonum(buf, 0, UINT32_MAX / 60, &errstr);
+			if (errstr == NULL) {
+				goto cont;
+			} else {
+				err = 1;
+				fprintf(stderr, BAD_RAND_DELAY,
+				    &line[cursor], strerror(errno));
+				continue;
+			}
 		}
 
 		if ((cferr = next_field(0, 59, line, &cursor, NULL)) != CFOK ||
diff --git a/usr/src/cmd/cron/elm.c b/usr/src/cmd/cron/elm.c
index 7956a0f26b..324135150b 100644
--- a/usr/src/cmd/cron/elm.c
+++ b/usr/src/cmd/cron/elm.c
@@ -25,7 +25,7 @@
  */
 
 /*	Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T	*/
-/*	  All Rights Reserved  	*/
+/*	  All Rights Reserved  */
 
 
 
@@ -125,12 +125,9 @@ struct index {	struct key *key;
 /* index pts to the front of the index list */
 static struct index *index = NULL;
 
-/* ******************* */
+
 void
-el_init(du, lb, dt, nlim)
-/* ******************* */
-int du, nlim;
-time_t lb, dt;
+el_init(int du, time_t lb, time_t dt, int nlim)
 {
 	int	i;
 	time_t	t;
@@ -217,13 +214,8 @@ time_t lb, dt;
 }
 
 
-/* ********************** */
 int
-el_add(event, time, id)
-/* ********************** */
-void	*event;
-int	id;
-time_t	time;
+el_add(void *event, time_t time, int id)
 {
 	/*
 	 * add works slightly differently than in the reference.  if the
@@ -303,11 +295,8 @@ time_t	time;
 }
 
 
-/* ******************** */
 void
-el_remove(id, flag)
-/* ******************** */
-int	id, flag;
+el_remove(int id, int flag)
 {
 	/*
 	 * remove finds notices n that need to be removed by traversing thru
@@ -334,11 +323,13 @@ int	id, flag;
 				(k->left)->right = k->right;
 				(k->right)->left = k->left;
 				free(k);
-			} else { if (n->key != NULL) {
+			} else {
+				if (n->key != NULL) {
 					/* n has a key pointing to it */
 					(n->left)->key = n->key;
 					(n->key)->time = (n->left)->time;
-					(n->key)->notice = n->left; }
+					(n->key)->notice = n->left;
+				}
 				/* find the key that points to this sublist */
 				n2 = n;
 				while (n2->key == NULL) n2 = n2->right;
@@ -359,8 +350,7 @@ int	id, flag;
 					k->left = kl->left;
 					free(kl);
 				} else if ((!(k->notice)->isdummy) &&
-					    ((kr->numnote+k->numnote)
-					    <= NLIM)) {
+				    ((kr->numnote+k->numnote) <= NLIM)) {
 					/* delete this key */
 					(k->notice)->key = NULL;
 					kr->numnote += k->numnote;
@@ -386,10 +376,8 @@ int	id, flag;
 }
 
 
-/* ********************* */
 int
 el_empty(void)
-/* ********************* */
 {
 	if (current == NULL)
 		return (1);
@@ -398,10 +386,8 @@ el_empty(void)
 }
 
 
-/* ********************* */
 void *
 el_first(void)
-/* ********************* */
 {
 	struct notice *n, *fn;
 	struct key *k, *fk;
@@ -496,10 +482,8 @@ el_first(void)
 }
 
 
-/* ************** */
 void
 el_delete(void)
-/* ************** */
 {
 	/* el_delete frees up all the space associated with the event list */
 
diff --git a/usr/src/cmd/cron/permit.c b/usr/src/cmd/cron/permit.c
index a5a951200b..6b5ea10577 100644
--- a/usr/src/cmd/cron/permit.c
+++ b/usr/src/cmd/cron/permit.c
@@ -19,7 +19,7 @@
  * CDDL HEADER END
  */
 /*	Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T	*/
-/*	  All Rights Reserved  	*/
+/*	  All Rights Reserved  */
 
 /*
  * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
@@ -46,8 +46,7 @@ static int within(char *, char *);
 
 
 char *
-getuser(uid)
-uid_t uid;
+getuser(uid_t uid)
 {
 	struct passwd *nptr;
 
@@ -69,8 +68,7 @@ uid_t uid;
 }
 
 int
-allowed(user, allow, deny)
-char *user, *allow, *deny;
+allowed(char *user, char *allow, char *deny)
 {
 	if (exists(allow)) {
 		if (within(user, allow)) {
@@ -92,8 +90,7 @@ char *user, *allow, *deny;
 }
 
 static int
-within(username, filename)
-char *username, *filename;
+within(char *username, char *filename)
 {
 	char line[UNAMESIZE];
 	FILE *cap;
diff --git a/usr/src/man/man1/crontab.1 b/usr/src/man/man1/crontab.1
index 549133aad2..49723a0b3e 100644
--- a/usr/src/man/man1/crontab.1
+++ b/usr/src/man/man1/crontab.1
@@ -44,8 +44,10 @@
 .\" Portions Copyright (c) 1992, X/Open Company Limited All Rights Reserved
 .\" Copyright (c) 2009, Sun Microsystems, Inc. All Rights Reserved
 .\" Copyright 2020 OmniOS Community Edition (OmniOSce) Association.
+.\" Copyright 2022 Sebastian Wiedenroth
+
 .\"
-.TH CRONTAB 1 "Aug 20, 2020"
+.TH CRONTAB 1 "Jan 9, 2022"
 .SH NAME
 crontab \- user crontab file
 .SH SYNOPSIS
@@ -314,6 +316,29 @@ TZ=Iceland
 .RE
 
 .sp
+.ne 2
+.na
+\fBRANDOM_DELAY\fR
+.ad
+.sp .6
+.RS 4n
+Allows the user to specify an upper bound in minutes for which execution
+may be delayed. The default is 0 which means no delay. A value that is
+larger than the scheduled interval may result in the command running less
+often. For example, to have the command run at some random time within
+two minutes after the schedule use:
+.sp
+.in +2
+.nf
+RANDOM_DELAY=2
+.fi
+.in -2
+.sp
+
+.RE
+
+
+.sp
 .LP
 Each of these variables affects all of the lines that follow it in the
 \fBcrontab\fR file, until it is reset by a subsequent line resetting that