Daan De Meyer
dd3c825294
Instead of having fopen_temporary() create the file either next to an existing file or in tmp/, let's split this up clearly into two different functions, one for creating temporary files next to existing files, and one for creating a temporary file in a directory.
411 lines
11 KiB
C
411 lines
11 KiB
C
/* SPDX-License-Identifier: LGPL-2.1-or-later */
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#include <sys/mman.h>
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#include "alloc-util.h"
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#include "fd-util.h"
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#include "fileio.h"
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#include "fs-util.h"
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#include "hexdecoct.h"
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#include "macro.h"
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#include "memfd-util.h"
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#include "missing_fcntl.h"
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#include "missing_syscall.h"
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#include "path-util.h"
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#include "process-util.h"
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#include "random-util.h"
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#include "stdio-util.h"
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#include "string-util.h"
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#include "tmpfile-util.h"
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#include "umask-util.h"
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static int fopen_temporary_internal(int dir_fd, const char *path, FILE **ret_file) {
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_cleanup_fclose_ FILE *f = NULL;
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_cleanup_close_ int fd = -1;
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int r;
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assert(dir_fd >= 0 || dir_fd == AT_FDCWD);
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assert(path);
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fd = openat(dir_fd, path, O_CLOEXEC|O_NOCTTY|O_RDWR|O_CREAT|O_EXCL, 0600);
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if (fd < 0)
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return -errno;
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/* This assumes that returned FILE object is short-lived and used within the same single-threaded
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* context and never shared externally, hence locking is not necessary. */
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r = take_fdopen_unlocked(&fd, "w", &f);
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if (r < 0) {
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(void) unlinkat(dir_fd, path, 0);
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return r;
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}
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if (ret_file)
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*ret_file = TAKE_PTR(f);
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return 0;
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}
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int fopen_temporary_at(int dir_fd, const char *path, FILE **ret_file, char **ret_path) {
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_cleanup_free_ char *t = NULL;
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int r;
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assert(dir_fd >= 0 || dir_fd == AT_FDCWD);
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assert(path);
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r = tempfn_random(path, NULL, &t);
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if (r < 0)
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return r;
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r = fopen_temporary_internal(dir_fd, t, ret_file);
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if (r < 0)
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return r;
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if (ret_path)
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*ret_path = TAKE_PTR(t);
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return 0;
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}
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int fopen_temporary_child_at(int dir_fd, const char *path, FILE **ret_file, char **ret_path) {
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_cleanup_free_ char *t = NULL;
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int r;
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assert(dir_fd >= 0 || dir_fd == AT_FDCWD);
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if (!path) {
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r = tmp_dir(&path);
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if (r < 0)
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return r;
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}
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r = tempfn_random_child(path, NULL, &t);
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if (r < 0)
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return r;
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r = fopen_temporary_internal(dir_fd, t, ret_file);
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if (r < 0)
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return r;
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if (ret_path)
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*ret_path = TAKE_PTR(t);
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return 0;
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}
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/* This is much like mkostemp() but is subject to umask(). */
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int mkostemp_safe(char *pattern) {
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assert(pattern);
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BLOCK_WITH_UMASK(0077);
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return RET_NERRNO(mkostemp(pattern, O_CLOEXEC));
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}
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int fmkostemp_safe(char *pattern, const char *mode, FILE **ret_f) {
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_cleanup_close_ int fd = -1;
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FILE *f;
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fd = mkostemp_safe(pattern);
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if (fd < 0)
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return fd;
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f = take_fdopen(&fd, mode);
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if (!f)
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return -errno;
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*ret_f = f;
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return 0;
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}
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static int tempfn_build(const char *p, const char *pre, const char *post, bool child, char **ret) {
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_cleanup_free_ char *d = NULL, *fn = NULL, *nf = NULL, *result = NULL;
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size_t len_pre, len_post, len_add;
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int r;
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assert(p);
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assert(ret);
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/*
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* Turns this:
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* /foo/bar/waldo
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*
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* Into this :
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* /foo/bar/waldo/.#<pre><post> (child == true)
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* /foo/bar/.#<pre>waldo<post> (child == false)
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*/
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if (pre && strchr(pre, '/'))
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return -EINVAL;
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if (post && strchr(post, '/'))
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return -EINVAL;
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len_pre = strlen_ptr(pre);
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len_post = strlen_ptr(post);
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/* NAME_MAX is counted *without* the trailing NUL byte. */
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if (len_pre > NAME_MAX - STRLEN(".#") ||
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len_post > NAME_MAX - STRLEN(".#") - len_pre)
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return -EINVAL;
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len_add = len_pre + len_post + STRLEN(".#");
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if (child) {
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d = strdup(p);
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if (!d)
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return -ENOMEM;
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} else {
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r = path_extract_directory(p, &d);
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if (r < 0 && r != -EDESTADDRREQ) /* EDESTADDRREQ → No directory specified, just a filename */
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return r;
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r = path_extract_filename(p, &fn);
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if (r < 0)
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return r;
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if (strlen(fn) > NAME_MAX - len_add)
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/* We cannot simply prepend and append strings to the filename. Let's truncate the filename. */
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fn[NAME_MAX - len_add] = '\0';
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}
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nf = strjoin(".#", strempty(pre), strempty(fn), strempty(post));
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if (!nf)
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return -ENOMEM;
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if (d) {
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if (!path_extend(&d, nf))
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return -ENOMEM;
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result = path_simplify(TAKE_PTR(d));
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} else
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result = TAKE_PTR(nf);
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if (!path_is_valid(result)) /* New path is not valid? (Maybe because too long?) Refuse. */
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return -EINVAL;
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*ret = TAKE_PTR(result);
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return 0;
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}
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int tempfn_xxxxxx(const char *p, const char *extra, char **ret) {
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/*
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* Turns this:
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* /foo/bar/waldo
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*
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* Into this:
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* /foo/bar/.#<extra>waldoXXXXXX
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*/
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return tempfn_build(p, extra, "XXXXXX", /* child = */ false, ret);
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}
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int tempfn_random(const char *p, const char *extra, char **ret) {
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_cleanup_free_ char *s = NULL;
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assert(p);
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assert(ret);
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/*
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* Turns this:
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* /foo/bar/waldo
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*
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* Into this:
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* /foo/bar/.#<extra>waldobaa2a261115984a9
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*/
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if (asprintf(&s, "%016" PRIx64, random_u64()) < 0)
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return -ENOMEM;
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return tempfn_build(p, extra, s, /* child = */ false, ret);
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}
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int tempfn_random_child(const char *p, const char *extra, char **ret) {
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_cleanup_free_ char *s = NULL;
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int r;
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assert(ret);
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/* Turns this:
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* /foo/bar/waldo
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* Into this:
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* /foo/bar/waldo/.#<extra>3c2b6219aa75d7d0
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*/
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if (!p) {
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r = tmp_dir(&p);
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if (r < 0)
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return r;
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}
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if (asprintf(&s, "%016" PRIx64, random_u64()) < 0)
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return -ENOMEM;
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return tempfn_build(p, extra, s, /* child = */ true, ret);
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}
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int open_tmpfile_unlinkable(const char *directory, int flags) {
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char *p;
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int fd, r;
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if (!directory) {
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r = tmp_dir(&directory);
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if (r < 0)
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return r;
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} else if (isempty(directory))
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return -EINVAL;
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/* Returns an unlinked temporary file that cannot be linked into the file system anymore */
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/* Try O_TMPFILE first, if it is supported */
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fd = open(directory, flags|O_TMPFILE|O_EXCL, S_IRUSR|S_IWUSR);
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if (fd >= 0)
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return fd;
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/* Fall back to unguessable name + unlinking */
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p = strjoina(directory, "/systemd-tmp-XXXXXX");
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fd = mkostemp_safe(p);
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if (fd < 0)
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return fd;
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(void) unlink(p);
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return fd;
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}
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int open_tmpfile_linkable(const char *target, int flags, char **ret_path) {
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_cleanup_free_ char *tmp = NULL;
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int r, fd;
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assert(target);
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assert(ret_path);
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/* Don't allow O_EXCL, as that has a special meaning for O_TMPFILE */
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assert((flags & O_EXCL) == 0);
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/* Creates a temporary file, that shall be renamed to "target" later. If possible, this uses O_TMPFILE – in
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* which case "ret_path" will be returned as NULL. If not possible the temporary path name used is returned in
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* "ret_path". Use link_tmpfile() below to rename the result after writing the file in full. */
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fd = open_parent(target, O_TMPFILE|flags, 0640);
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if (fd >= 0) {
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*ret_path = NULL;
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return fd;
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}
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log_debug_errno(fd, "Failed to use O_TMPFILE for %s: %m", target);
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r = tempfn_random(target, NULL, &tmp);
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if (r < 0)
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return r;
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fd = open(tmp, O_CREAT|O_EXCL|O_NOFOLLOW|O_NOCTTY|flags, 0640);
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if (fd < 0)
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return -errno;
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*ret_path = TAKE_PTR(tmp);
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return fd;
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}
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int fopen_tmpfile_linkable(const char *target, int flags, char **ret_path, FILE **ret_file) {
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_cleanup_free_ char *path = NULL;
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_cleanup_fclose_ FILE *f = NULL;
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_cleanup_close_ int fd = -1;
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assert(target);
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assert(ret_file);
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assert(ret_path);
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fd = open_tmpfile_linkable(target, flags, &path);
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if (fd < 0)
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return fd;
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f = take_fdopen(&fd, "w");
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if (!f)
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return -ENOMEM;
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*ret_path = TAKE_PTR(path);
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*ret_file = TAKE_PTR(f);
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return 0;
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}
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int link_tmpfile(int fd, const char *path, const char *target) {
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assert(fd >= 0);
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assert(target);
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/* Moves a temporary file created with open_tmpfile() above into its final place. if "path" is NULL an fd
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* created with O_TMPFILE is assumed, and linkat() is used. Otherwise it is assumed O_TMPFILE is not supported
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* on the directory, and renameat2() is used instead.
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*
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* Note that in both cases we will not replace existing files. This is because linkat() does not support this
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* operation currently (renameat2() does), and there is no nice way to emulate this. */
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if (path)
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return rename_noreplace(AT_FDCWD, path, AT_FDCWD, target);
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return RET_NERRNO(linkat(AT_FDCWD, FORMAT_PROC_FD_PATH(fd), AT_FDCWD, target, AT_SYMLINK_FOLLOW));
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}
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int flink_tmpfile(FILE *f, const char *path, const char *target) {
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int fd, r;
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assert(f);
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assert(target);
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fd = fileno(f);
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if (fd < 0) /* Not all FILE* objects encapsulate fds */
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return -EBADF;
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r = fflush_sync_and_check(f);
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if (r < 0)
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return r;
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return link_tmpfile(fd, path, target);
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}
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int mkdtemp_malloc(const char *template, char **ret) {
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_cleanup_free_ char *p = NULL;
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int r;
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assert(ret);
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if (template)
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p = strdup(template);
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else {
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const char *tmp;
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r = tmp_dir(&tmp);
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if (r < 0)
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return r;
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p = path_join(tmp, "XXXXXX");
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}
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if (!p)
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return -ENOMEM;
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if (!mkdtemp(p))
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return -errno;
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*ret = TAKE_PTR(p);
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return 0;
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}
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int mkdtemp_open(const char *template, int flags, char **ret) {
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_cleanup_free_ char *p = NULL;
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int fd, r;
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r = mkdtemp_malloc(template, &p);
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if (r < 0)
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return r;
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fd = RET_NERRNO(open(p, O_DIRECTORY|O_CLOEXEC|flags));
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if (fd < 0) {
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(void) rmdir(p);
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return fd;
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}
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if (ret)
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*ret = TAKE_PTR(p);
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return fd;
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}
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