1 /* $OpenBSD: copy.c,v 1.4 2022/12/26 19:16:02 jmc Exp $ */
2 /*
3 * Copyright (c) 2021 Claudio Jeker <claudio@openbsd.org>
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17
18 #include <sys/types.h>
19
20 #include <err.h>
21 #include <fcntl.h>
22 #include <unistd.h>
23
24 #include "extern.h"
25
26 #define _MAXBSIZE (64 * 1024)
27
28 /*
29 * Return true if all bytes in buffer are zero.
30 * A buffer of zero length is also considered a zero buffer.
31 */
32 static int
iszero(const void * b,size_t len)33 iszero(const void *b, size_t len)
34 {
35 const unsigned char *c = b;
36
37 for (; len > 0; len--) {
38 if (*c++ != '\0')
39 return 0;
40 }
41 return 1;
42 }
43
44 static int
copy_internal(int fromfd,int tofd)45 copy_internal(int fromfd, int tofd)
46 {
47 char buf[_MAXBSIZE];
48 ssize_t r, w;
49
50 while ((r = read(fromfd, buf, sizeof(buf))) > 0) {
51 if (iszero(buf, sizeof(buf))) {
52 if (lseek(tofd, r, SEEK_CUR) == -1)
53 return -1;
54 } else {
55 w = write(tofd, buf, r);
56 if (r != w || w == -1)
57 return -1;
58 }
59 }
60 if (r == -1)
61 return -1;
62 if (ftruncate(tofd, lseek(tofd, 0, SEEK_CUR)) == -1)
63 return -1;
64 return 0;
65 }
66
67 void
copy_file(int rootfd,const char * basedir,const struct flist * f)68 copy_file(int rootfd, const char *basedir, const struct flist *f)
69 {
70 int fromfd, tofd, dfd;
71
72 dfd = openat(rootfd, basedir, O_RDONLY | O_DIRECTORY);
73 if (dfd == -1)
74 err(ERR_FILE_IO, "%s: openat", basedir);
75
76 fromfd = openat(dfd, f->path, O_RDONLY | O_NOFOLLOW);
77 if (fromfd == -1)
78 err(ERR_FILE_IO, "%s/%s: openat", basedir, f->path);
79 close(dfd);
80
81 tofd = openat(rootfd, f->path,
82 O_WRONLY | O_NOFOLLOW | O_TRUNC | O_CREAT | O_EXCL,
83 0600);
84 if (tofd == -1)
85 err(ERR_FILE_IO, "%s: openat", f->path);
86
87 if (copy_internal(fromfd, tofd) == -1)
88 err(ERR_FILE_IO, "%s: copy file", f->path);
89
90 close(fromfd);
91 close(tofd);
92 }
93