===================================================================
RCS file: /cvsrepo/anoncvs/cvs/src/usr.bin/xinstall/xinstall.c,v
retrieving revision 1.68
retrieving revision 1.69
diff -u -r1.68 -r1.69
--- src/usr.bin/xinstall/xinstall.c	2019/02/08 12:53:44	1.68
+++ src/usr.bin/xinstall/xinstall.c	2019/02/09 22:08:25	1.69
@@ -1,4 +1,4 @@
-/*	$OpenBSD: xinstall.c,v 1.68 2019/02/08 12:53:44 schwarze Exp $	*/
+/*	$OpenBSD: xinstall.c,v 1.69 2019/02/09 22:08:25 schwarze Exp $	*/
 /*	$NetBSD: xinstall.c,v 1.9 1995/12/20 10:25:17 jonathan Exp $	*/
 
 /*
@@ -60,7 +60,7 @@
 #define NOCHANGEBITS	(UF_IMMUTABLE | UF_APPEND | SF_IMMUTABLE | SF_APPEND)
 #define BACKUP_SUFFIX	".old"
 
-int dobackup, docompare, dodest, dodir, dopreserve, dostrip;
+int dobackup, docompare, dodest, dodir, dopreserve, dostrip, safecopy;
 int mode = S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH;
 char pathbuf[PATH_MAX], tempfile[PATH_MAX];
 char *suffix = BACKUP_SUFFIX;
@@ -73,6 +73,7 @@
 void	install_dir(char *, int);
 void	strip(char *);
 void	usage(void);
+int	create_newfile(char *, struct stat *);
 int	create_tempfile(char *, char *, size_t);
 int	file_write(int, char *, size_t, int *, int *, int);
 void	file_flush(int, int);
@@ -128,7 +129,7 @@
 			docompare = dopreserve = 1;
 			break;
 		case 'S':
-			/* For backwards compatibility. */
+			safecopy = 1;
 			break;
 		case 's':
 			dostrip = 1;
@@ -147,13 +148,17 @@
 	argv += optind;
 
 	/* some options make no sense when creating directories */
-	if ((docompare || dostrip) && dodir)
+	if ((safecopy || docompare || dostrip) && dodir)
 		usage();
 
 	/* must have at least two arguments, except when creating directories */
 	if (argc < 2 && !dodir)
 		usage();
 
+	/* need to make a temp copy so we can compare stripped version */
+	if (docompare && dostrip)
+		safecopy = 1;
+
 	/* get group and owner id's */
 	if (group != NULL && gid_from_group(group, &gid) == -1) {
 		gid = strtonum(group, 0, GID_MAX, &errstr);
@@ -260,30 +265,54 @@
 			err(1, "%s", from_name);
 	}
 
-	to_fd = create_tempfile(to_name, tempfile, sizeof(tempfile));
-	if (to_fd < 0)
-		err(1, "%s", tempfile);
+	if (safecopy) {
+		to_fd = create_tempfile(to_name, tempfile, sizeof(tempfile));
+		if (to_fd < 0)
+			err(1, "%s", tempfile);
+	} else if (docompare && !dostrip) {
+		if ((to_fd = open(to_name, O_RDONLY, 0)) < 0)
+			err(1, "%s", to_name);
+	} else {
+		if ((to_fd = create_newfile(to_name, &to_sb)) < 0)
+			err(1, "%s", to_name);
+	}
 
-	if (!devnull)
-		copy(from_fd, from_name, to_fd, tempfile, from_sb.st_size,
-		    ((off_t)from_sb.st_blocks * S_BLKSIZE < from_sb.st_size));
+	if (!devnull) {
+		if (docompare && !safecopy) {
+			files_match = !(compare(from_fd, from_name,
+					from_sb.st_size, to_fd,
+					to_name, to_sb.st_size));
 
+			/* Truncate "to" file for copy unless we match */
+			if (!files_match) {
+				(void)close(to_fd);
+				if ((to_fd = create_newfile(to_name, &to_sb)) < 0)
+					err(1, "%s", to_name);
+			}
+		}
+		if (!files_match)
+			copy(from_fd, from_name, to_fd,
+			     safecopy ? tempfile : to_name, from_sb.st_size,
+			     ((off_t)from_sb.st_blocks * S_BLKSIZE < from_sb.st_size));
+	}
+
 	if (dostrip) {
-		strip(tempfile);
+		strip(safecopy ? tempfile : to_name);
 
 		/*
 		 * Re-open our fd on the target, in case we used a strip
 		 *  that does not work in-place -- like gnu binutils strip.
 		 */
 		close(to_fd);
-		if ((to_fd = open(tempfile, O_RDONLY, 0)) < 0)
+		if ((to_fd = open(safecopy ? tempfile : to_name, O_RDONLY,
+		     0)) < 0)
 			err(1, "stripping %s", to_name);
 	}
 
 	/*
 	 * Compare the (possibly stripped) temp file to the target.
 	 */
-	if (docompare) {
+	if (safecopy && docompare) {
 		int temp_fd = to_fd;
 		struct stat temp_sb;
 
@@ -333,13 +362,15 @@
 	if ((gid != (gid_t)-1 || uid != (uid_t)-1) &&
 	    fchown(to_fd, uid, gid)) {
 		serrno = errno;
-		(void)unlink(tempfile);
-		errx(1, "%s: chown/chgrp: %s", tempfile, strerror(serrno));
+		(void)unlink(safecopy ? tempfile : to_name);
+		errx(1, "%s: chown/chgrp: %s",
+		    safecopy ? tempfile : to_name, strerror(serrno));
 	}
 	if (fchmod(to_fd, mode)) {
 		serrno = errno;
-		(void)unlink(tempfile);
-		errx(1, "%s: chmod: %s", tempfile, strerror(serrno));
+		(void)unlink(safecopy ? tempfile : to_name);
+		errx(1, "%s: chmod: %s", safecopy ? tempfile : to_name,
+		    strerror(serrno));
 	}
 
 	/*
@@ -349,7 +380,8 @@
 	if (fchflags(to_fd,
 	    flags & SETFLAGS ? fset : from_sb.st_flags & ~UF_NODUMP)) {
 		if (errno != EOPNOTSUPP || (from_sb.st_flags & ~UF_NODUMP) != 0)
-			warnx("%s: chflags: %s", tempfile, strerror(errno));
+			warnx("%s: chflags: %s",
+			    safecopy ? tempfile :to_name, strerror(errno));
 	}
 
 	if (flags & USEFSYNC)
@@ -359,10 +391,10 @@
 		(void)close(from_fd);
 
 	/*
-	 * Move the new file into place if the files are different
-	 * or were not compared.
+	 * Move the new file into place if doing a safe copy
+	 * and the files are different (or just not compared).
 	 */
-	if (!files_match) {
+	if (safecopy && !files_match) {
 		/* Try to turn off the immutable bits. */
 		if (to_sb.st_flags & (NOCHANGEBITS))
 			(void)chflags(to_name, to_sb.st_flags & ~(NOCHANGEBITS));
@@ -623,6 +655,36 @@
 	strlcat(p, "INS@XXXXXXXXXX", tsize);
 
 	return(mkstemp(temp));
+}
+
+/*
+ * create_newfile --
+ *	create a new file, overwriting an existing one if necessary
+ */
+int
+create_newfile(char *path, struct stat *sbp)
+{
+	char backup[PATH_MAX];
+
+	/*
+	 * Unlink now... avoid ETXTBSY errors later.  Try and turn
+	 * off the append/immutable bits -- if we fail, go ahead,
+	 * it might work.
+	 */
+	if (sbp->st_flags & (NOCHANGEBITS))
+		(void)chflags(path, sbp->st_flags & ~(NOCHANGEBITS));
+
+	if (dobackup) {
+		(void)snprintf(backup, PATH_MAX, "%s%s", path, suffix);
+		/* It is ok for the target file not to exist. */
+		if (rename(path, backup) < 0 && errno != ENOENT)
+			err(1, "rename: %s to %s (errno %d)", path, backup, errno);
+	} else {
+		if (unlink(path) < 0 && errno != ENOENT)
+			err(1, "%s", path);
+	}
+
+	return(open(path, O_CREAT | O_RDWR | O_EXCL, S_IRUSR | S_IWUSR));
 }
 
 /*