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 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 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 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