install: add -z <max_cmp_size> option

Introduces the -z <max_cmp_size> flag, enabling users to set a custom file
size limit for pre-installation change checks and avoiding future hard-coded
limit modifications.

Reviewed by:    glebius
Approved by:    glebius (mentor)
Obtained from:  Fudo Security
MFC after:      2 weeks
Sponsored by:   Fudo Security
Differential Revision:	https://reviews.freebsd.org/D57230

usr.bin/xinstall/Makefile

@@ -11,7 +11,7 @@ MAN=		install.1
 CFLAGS+=	-I${SRCTOP}/contrib/mtree
 CFLAGS+=	-I${SRCTOP}/lib/libnetbsd
 
-LIBADD=		md
+LIBADD=		md util
 CFLAGS+=	-DWITH_MD5 -DWITH_RIPEMD160
 
 .ifdef BOOTSTRAPPING

usr.bin/xinstall/install.1

@@ -33,7 +33,7 @@
 .Nd install binaries
 .Sh SYNOPSIS
 .Nm
-.Op Fl bCcpSsUv
+.Op Fl bCcpSsUvz
 .Op Fl B Ar suffix
 .Op Fl D Ar destdir
 .Op Fl f Ar flags
@@ -45,9 +45,10 @@
 .Op Fl N Ar dbdir
 .Op Fl o Ar owner
 .Op Fl T Ar tags
+.Op Fl z Ar size
 .Ar file1 file2
 .Nm
-.Op Fl bCcpSsUv
+.Op Fl bCcpSsUvz
 .Op Fl B Ar suffix
 .Op Fl D Ar destdir
 .Op Fl f Ar flags
@@ -59,6 +60,7 @@
 .Op Fl N Ar dbdir
 .Op Fl o Ar owner
 .Op Fl T Ar tags
+.Op Fl z Ar size
 .Ar file1 ... fileN directory
 .Nm
 .Fl d
@@ -264,6 +266,13 @@ Cause
 .Nm
 to be verbose,
 showing files as they are installed or backed up.
+.It Fl z Ar maxsize
+Limit the comparison feature of
+.Fl C
+to files no larger than
+.Ar maxsize .
+Files exceeding this limit bypass the comparison step and are directly overwritten.
+The default maximum size is 128MiB.
 .El
 .Pp
 By default,

usr.bin/xinstall/xinstall.c

@@ -57,6 +57,7 @@
 #include <string.h>
 #include <sysexits.h>
 #include <unistd.h>
+#include <util.h>
 #include <vis.h>
 
 #include "mtree.h"
@@ -137,6 +138,7 @@ static FILE *metafp;
 static const char *group, *owner;
 static const char *suffix = BACKUP_SUFFIX;
 static char *destdir, *digest, *fflags, *metafile, *tags;
+static size_t max_compare_size = MAX_CMP_SIZE;
 
 static int	compare(int, const char *, size_t, int, const char *, size_t,
 		    char **);
@@ -168,12 +170,13 @@ main(int argc, char *argv[])
 	u_int iflags;
 	char *p;
 	const char *to_name;
+	uint64_t num;
 
 	fset = 0;
 	iflags = 0;
 	set = NULL;
 	group = owner = NULL;
-	while ((ch = getopt(argc, argv, "B:bCcD:df:g:h:l:M:m:N:o:pSsT:Uv")) !=
+	while ((ch = getopt(argc, argv, "B:bCcD:df:g:h:l:M:m:N:o:pSsT:Uvz:")) !=
 	     -1)
 		switch((char)ch) {
 		case 'B':
@@ -270,6 +273,13 @@ main(int argc, char *argv[])
 		case 'v':
 			verbose = 1;
 			break;
+		case 'z':
+			if (expand_number(optarg, &num) != 0 || num == 0) {
+				errx(EX_USAGE, "invalid max compare filesize:"
+				    " %s", optarg);
+			}
+			max_compare_size = num;
+			break;
 		case '?':
 		default:
 			usage();
@@ -1092,7 +1102,7 @@ compare(int from_fd, const char *from_name __unused, size_t from_len,
 
 	do_digest = (digesttype != DIGEST_NONE && dresp != NULL &&
 	    *dresp == NULL);
-	if (from_len <= MAX_CMP_SIZE) {
+	if (from_len <= max_compare_size) {
 		static char *buf, *buf1, *buf2;
 		static size_t bufsize;
 		int n1, n2;
@@ -1484,11 +1494,11 @@ usage(void)
 {
 	(void)fprintf(stderr,
 "usage: install [-bCcpSsUv] [-f flags] [-g group] [-m mode] [-o owner]\n"
-"               [-M log] [-D dest] [-h hash] [-T tags]\n"
+"               [-M log] [-D dest] [-h hash] [-T tags] [-z maxcmpsize]\n"
 "               [-B suffix] [-l linkflags] [-N dbdir]\n"
 "               file1 file2\n"
 "       install [-bCcpSsUv] [-f flags] [-g group] [-m mode] [-o owner]\n"
-"               [-M log] [-D dest] [-h hash] [-T tags]\n"
+"               [-M log] [-D dest] [-h hash] [-T tags] [-z maxcmpsize]\n"
 "               [-B suffix] [-l linkflags] [-N dbdir]\n"
 "               file1 ... fileN directory\n"
 "       install -dU [-vU] [-g group] [-m mode] [-N dbdir] [-o owner]\n"