chiark / gitweb /
core: introduce parse_ip_port (#4825)
[elogind.git] / src / basic / fs-util.c
index ba79a32..4d49465 100644 (file)
@@ -1,5 +1,3 @@
-/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
-
 /***
   This file is part of systemd.
 
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+#include <dirent.h>
+#include <errno.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <time.h>
+#include <unistd.h>
+
 #include "alloc-util.h"
 #include "dirent-util.h"
 #include "fd-util.h"
 #include "fileio.h"
 #include "fs-util.h"
+//#include "log.h"
+//#include "macro.h"
+//#include "missing.h"
 #include "mkdir.h"
 #include "parse-util.h"
 #include "path-util.h"
 #include "string-util.h"
 #include "strv.h"
+//#include "time-util.h"
 #include "user-util.h"
 #include "util.h"
 
@@ -213,25 +225,25 @@ int readlink_and_make_absolute(const char *p, char **r) {
         return 0;
 }
 
-int readlink_and_canonicalize(const char *p, char **r) {
+int readlink_and_canonicalize(const char *p, const char *root, char **ret) {
         char *t, *s;
-        int j;
+        int r;
 
         assert(p);
-        assert(r);
+        assert(ret);
 
-        j = readlink_and_make_absolute(p, &t);
-        if (j < 0)
-                return j;
+        r = readlink_and_make_absolute(p, &t);
+        if (r < 0)
+                return r;
 
-        s = canonicalize_file_name(t);
-        if (s) {
+        r = chase_symlinks(t, root, 0, &s);
+        if (r < 0)
+                /* If we can't follow up, then let's return the original string, slightly cleaned up. */
+                *ret = path_kill_slashes(t);
+        else {
+                *ret = s;
                 free(t);
-                *r = s;
-        } else
-                *r = t;
-
-        path_kill_slashes(*r);
+        }
 
         return 0;
 }
@@ -275,26 +287,6 @@ int chmod_and_chown(const char *path, mode_t mode, uid_t uid, gid_t gid) {
         return 0;
 }
 
-#if 0 /// UNNEEDED by elogind
-int fchmod_and_fchown(int fd, mode_t mode, uid_t uid, gid_t gid) {
-        assert(fd >= 0);
-
-        /* Under the assumption that we are running privileged we
-         * first change the access mode and only then hand out
-         * ownership to avoid a window where access is too open. */
-
-        if (mode != MODE_INVALID)
-                if (fchmod(fd, mode) < 0)
-                        return -errno;
-
-        if (uid != UID_INVALID || gid != GID_INVALID)
-                if (fchown(fd, uid, gid) < 0)
-                        return -errno;
-
-        return 0;
-}
-#endif // 0
-
 int fchmod_umask(int fd, mode_t m) {
         mode_t u;
         int r;
@@ -333,7 +325,8 @@ int touch_file(const char *path, bool parents, usec_t stamp, uid_t uid, gid_t gi
         if (parents)
                 mkdir_parents(path, 0755);
 
-        fd = open(path, O_WRONLY|O_CREAT|O_CLOEXEC|O_NOCTTY, mode > 0 ? mode : 0644);
+        fd = open(path, O_WRONLY|O_CREAT|O_CLOEXEC|O_NOCTTY,
+                        (mode == 0 || mode == MODE_INVALID) ? 0644 : mode);
         if (fd < 0)
                 return -errno;
 
@@ -475,7 +468,7 @@ int get_files_in_directory(const char *path, char ***list) {
 
                 errno = 0;
                 de = readdir(d);
-                if (!de && errno != 0)
+                if (!de && errno > 0)
                         return -errno;
                 if (!de)
                         break;
@@ -506,3 +499,323 @@ int get_files_in_directory(const char *path, char ***list) {
 
         return n;
 }
+
+#if 0 /// UNNEEDED by elogind
+static int getenv_tmp_dir(const char **ret_path) {
+        const char *n;
+        int r, ret = 0;
+
+        assert(ret_path);
+
+        /* We use the same order of environment variables python uses in tempfile.gettempdir():
+         * https://docs.python.org/3/library/tempfile.html#tempfile.gettempdir */
+        FOREACH_STRING(n, "TMPDIR", "TEMP", "TMP") {
+                const char *e;
+
+                e = secure_getenv(n);
+                if (!e)
+                        continue;
+                if (!path_is_absolute(e)) {
+                        r = -ENOTDIR;
+                        goto next;
+                }
+                if (!path_is_safe(e)) {
+                        r = -EPERM;
+                        goto next;
+                }
+
+                r = is_dir(e, true);
+                if (r < 0)
+                        goto next;
+                if (r == 0) {
+                        r = -ENOTDIR;
+                        goto next;
+                }
+
+                *ret_path = e;
+                return 1;
+
+        next:
+                /* Remember first error, to make this more debuggable */
+                if (ret >= 0)
+                        ret = r;
+        }
+
+        if (ret < 0)
+                return ret;
+
+        *ret_path = NULL;
+        return ret;
+}
+
+static int tmp_dir_internal(const char *def, const char **ret) {
+        const char *e;
+        int r, k;
+
+        assert(def);
+        assert(ret);
+
+        r = getenv_tmp_dir(&e);
+        if (r > 0) {
+                *ret = e;
+                return 0;
+        }
+
+        k = is_dir(def, true);
+        if (k == 0)
+                k = -ENOTDIR;
+        if (k < 0)
+                return r < 0 ? r : k;
+
+        *ret = def;
+        return 0;
+}
+
+int var_tmp_dir(const char **ret) {
+
+        /* Returns the location for "larger" temporary files, that is backed by physical storage if available, and thus
+         * even might survive a boot: /var/tmp. If $TMPDIR (or related environment variables) are set, its value is
+         * returned preferably however. Note that both this function and tmp_dir() below are affected by $TMPDIR,
+         * making it a variable that overrides all temporary file storage locations. */
+
+        return tmp_dir_internal("/var/tmp", ret);
+}
+
+int tmp_dir(const char **ret) {
+
+        /* Similar to var_tmp_dir() above, but returns the location for "smaller" temporary files, which is usually
+         * backed by an in-memory file system: /tmp. */
+
+        return tmp_dir_internal("/tmp", ret);
+}
+
+int inotify_add_watch_fd(int fd, int what, uint32_t mask) {
+        char path[strlen("/proc/self/fd/") + DECIMAL_STR_MAX(int) + 1];
+        int r;
+
+        /* This is like inotify_add_watch(), except that the file to watch is not referenced by a path, but by an fd */
+        xsprintf(path, "/proc/self/fd/%i", what);
+
+        r = inotify_add_watch(fd, path, mask);
+        if (r < 0)
+                return -errno;
+
+        return r;
+}
+
+int chase_symlinks(const char *path, const char *original_root, unsigned flags, char **ret) {
+        _cleanup_free_ char *buffer = NULL, *done = NULL, *root = NULL;
+        _cleanup_close_ int fd = -1;
+        unsigned max_follow = 32; /* how many symlinks to follow before giving up and returning ELOOP */
+        bool exists = true;
+        char *todo;
+        int r;
+
+        assert(path);
+
+        /* This is a lot like canonicalize_file_name(), but takes an additional "root" parameter, that allows following
+         * symlinks relative to a root directory, instead of the root of the host.
+         *
+         * Note that "root" primarily matters if we encounter an absolute symlink. It is also used when following
+         * relative symlinks to ensure they cannot be used to "escape" the root directory. The path parameter passed is
+         * assumed to be already prefixed by it, except if the CHASE_PREFIX_ROOT flag is set, in which case it is first
+         * prefixed accordingly.
+         *
+         * Algorithmically this operates on two path buffers: "done" are the components of the path we already
+         * processed and resolved symlinks, "." and ".." of. "todo" are the components of the path we still need to
+         * process. On each iteration, we move one component from "todo" to "done", processing it's special meaning
+         * each time. The "todo" path always starts with at least one slash, the "done" path always ends in no
+         * slash. We always keep an O_PATH fd to the component we are currently processing, thus keeping lookup races
+         * at a minimum.
+         *
+         * Suggested usage: whenever you want to canonicalize a path, use this function. Pass the absolute path you got
+         * as-is: fully qualified and relative to your host's root. Optionally, specify the root parameter to tell this
+         * function what to do when encountering a symlink with an absolute path as directory: prefix it by the
+         * specified path.
+         *
+         * Note: there's also chase_symlinks_prefix() (see below), which as first step prefixes the passed path by the
+         * passed root. */
+
+        if (original_root) {
+                r = path_make_absolute_cwd(original_root, &root);
+                if (r < 0)
+                        return r;
+
+                if (flags & CHASE_PREFIX_ROOT)
+                        path = prefix_roota(root, path);
+        }
+
+        r = path_make_absolute_cwd(path, &buffer);
+        if (r < 0)
+                return r;
+
+        fd = open("/", O_CLOEXEC|O_NOFOLLOW|O_PATH);
+        if (fd < 0)
+                return -errno;
+
+        todo = buffer;
+        for (;;) {
+                _cleanup_free_ char *first = NULL;
+                _cleanup_close_ int child = -1;
+                struct stat st;
+                size_t n, m;
+
+                /* Determine length of first component in the path */
+                n = strspn(todo, "/");                  /* The slashes */
+                m = n + strcspn(todo + n, "/");         /* The entire length of the component */
+
+                /* Extract the first component. */
+                first = strndup(todo, m);
+                if (!first)
+                        return -ENOMEM;
+
+                todo += m;
+
+                /* Just a single slash? Then we reached the end. */
+                if (isempty(first) || path_equal(first, "/"))
+                        break;
+
+                /* Just a dot? Then let's eat this up. */
+                if (path_equal(first, "/."))
+                        continue;
+
+                /* Two dots? Then chop off the last bit of what we already found out. */
+                if (path_equal(first, "/..")) {
+                        _cleanup_free_ char *parent = NULL;
+                        int fd_parent = -1;
+
+                        /* If we already are at the top, then going up will not change anything. This is in-line with
+                         * how the kernel handles this. */
+                        if (isempty(done) || path_equal(done, "/"))
+                                continue;
+
+                        parent = dirname_malloc(done);
+                        if (!parent)
+                                return -ENOMEM;
+
+                        /* Don't allow this to leave the root dir.  */
+                        if (root &&
+                            path_startswith(done, root) &&
+                            !path_startswith(parent, root))
+                                continue;
+
+                        free_and_replace(done, parent);
+
+                        fd_parent = openat(fd, "..", O_CLOEXEC|O_NOFOLLOW|O_PATH);
+                        if (fd_parent < 0)
+                                return -errno;
+
+                        safe_close(fd);
+                        fd = fd_parent;
+
+                        continue;
+                }
+
+                /* Otherwise let's see what this is. */
+                child = openat(fd, first + n, O_CLOEXEC|O_NOFOLLOW|O_PATH);
+                if (child < 0) {
+
+                        if (errno == ENOENT &&
+                            (flags & CHASE_NONEXISTENT) &&
+                            (isempty(todo) || path_is_safe(todo))) {
+
+                                /* If CHASE_NONEXISTENT is set, and the path does not exist, then that's OK, return
+                                 * what we got so far. But don't allow this if the remaining path contains "../ or "./"
+                                 * or something else weird. */
+
+                                if (!strextend(&done, first, todo, NULL))
+                                        return -ENOMEM;
+
+                                exists = false;
+                                break;
+                        }
+
+                        return -errno;
+                }
+
+                if (fstat(child, &st) < 0)
+                        return -errno;
+
+                if (S_ISLNK(st.st_mode)) {
+                        _cleanup_free_ char *destination = NULL;
+
+                        /* This is a symlink, in this case read the destination. But let's make sure we don't follow
+                         * symlinks without bounds. */
+                        if (--max_follow <= 0)
+                                return -ELOOP;
+
+                        r = readlinkat_malloc(fd, first + n, &destination);
+                        if (r < 0)
+                                return r;
+                        if (isempty(destination))
+                                return -EINVAL;
+
+                        if (path_is_absolute(destination)) {
+
+                                /* An absolute destination. Start the loop from the beginning, but use the root
+                                 * directory as base. */
+
+                                safe_close(fd);
+                                fd = open(root ?: "/", O_CLOEXEC|O_NOFOLLOW|O_PATH);
+                                if (fd < 0)
+                                        return -errno;
+
+                                free_and_replace(buffer, destination);
+
+                                todo = buffer;
+                                free(done);
+
+                                /* Note that we do not revalidate the root, we take it as is. */
+                                if (isempty(root))
+                                        done = NULL;
+                                else {
+                                        done = strdup(root);
+                                        if (!done)
+                                                return -ENOMEM;
+                                }
+
+                        } else {
+                                char *joined;
+
+                                /* A relative destination. If so, this is what we'll prefix what's left to do with what
+                                 * we just read, and start the loop again, but remain in the current directory. */
+
+                                joined = strjoin("/", destination, todo);
+                                if (!joined)
+                                        return -ENOMEM;
+
+                                free(buffer);
+                                todo = buffer = joined;
+                        }
+
+                        continue;
+                }
+
+                /* If this is not a symlink, then let's just add the name we read to what we already verified. */
+                if (!done) {
+                        done = first;
+                        first = NULL;
+                } else {
+                        if (!strextend(&done, first, NULL))
+                                return -ENOMEM;
+                }
+
+                /* And iterate again, but go one directory further down. */
+                safe_close(fd);
+                fd = child;
+                child = -1;
+        }
+
+        if (!done) {
+                /* Special case, turn the empty string into "/", to indicate the root directory. */
+                done = strdup("/");
+                if (!done)
+                        return -ENOMEM;
+        }
+
+        *ret = done;
+        done = NULL;
+
+        return exists;
+}
+#endif // 0