Adding upstream version 255.4.upstream/255.4

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1434 insertions, 0 deletions

diff --git a/src/basic/path-util.c b/src/basic/path-util.c
new file mode 100644
index 0000000..6810bf6
--- /dev/null
+++ b/src/basic/path-util.c
@@ -0,0 +1,1434 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+#include <fnmatch.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include "alloc-util.h"
+#include "chase.h"
+#include "extract-word.h"
+#include "fd-util.h"
+#include "fs-util.h"
+#include "glob-util.h"
+#include "log.h"
+#include "macro.h"
+#include "path-util.h"
+#include "stat-util.h"
+#include "string-util.h"
+#include "strv.h"
+#include "time-util.h"
+
+int path_split_and_make_absolute(const char *p, char ***ret) {
+        _cleanup_strv_free_ char **l = NULL;
+        int r;
+
+        assert(p);
+        assert(ret);
+
+        l = strv_split(p, ":");
+        if (!l)
+                return -ENOMEM;
+
+        r = path_strv_make_absolute_cwd(l);
+        if (r < 0)
+                return r;
+
+        *ret = TAKE_PTR(l);
+        return r;
+}
+
+char* path_make_absolute(const char *p, const char *prefix) {
+        assert(p);
+
+        /* Makes every item in the list an absolute path by prepending
+         * the prefix, if specified and necessary */
+
+        if (path_is_absolute(p) || isempty(prefix))
+                return strdup(p);
+
+        return path_join(prefix, p);
+}
+
+int safe_getcwd(char **ret) {
+        _cleanup_free_ char *cwd = NULL;
+
+        cwd = get_current_dir_name();
+        if (!cwd)
+                return negative_errno();
+
+        /* Let's make sure the directory is really absolute, to protect us from the logic behind
+         * CVE-2018-1000001 */
+        if (cwd[0] != '/')
+                return -ENOMEDIUM;
+
+        if (ret)
+                *ret = TAKE_PTR(cwd);
+
+        return 0;
+}
+
+int path_make_absolute_cwd(const char *p, char **ret) {
+        char *c;
+        int r;
+
+        assert(p);
+        assert(ret);
+
+        /* Similar to path_make_absolute(), but prefixes with the
+         * current working directory. */
+
+        if (path_is_absolute(p))
+                c = strdup(p);
+        else {
+                _cleanup_free_ char *cwd = NULL;
+
+                r = safe_getcwd(&cwd);
+                if (r < 0)
+                        return r;
+
+                c = path_join(cwd, p);
+        }
+        if (!c)
+                return -ENOMEM;
+
+        *ret = c;
+        return 0;
+}
+
+int path_make_relative(const char *from, const char *to, char **ret) {
+        _cleanup_free_ char *result = NULL;
+        unsigned n_parents;
+        const char *f, *t;
+        int r, k;
+        char *p;
+
+        assert(from);
+        assert(to);
+        assert(ret);
+
+        /* Strips the common part, and adds ".." elements as necessary. */
+
+        if (!path_is_absolute(from) || !path_is_absolute(to))
+                return -EINVAL;
+
+        for (;;) {
+                r = path_find_first_component(&from, true, &f);
+                if (r < 0)
+                        return r;
+
+                k = path_find_first_component(&to, true, &t);
+                if (k < 0)
+                        return k;
+
+                if (r == 0) {
+                        /* end of 'from' */
+                        if (k == 0) {
+                                /* from and to are equivalent. */
+                                result = strdup(".");
+                                if (!result)
+                                        return -ENOMEM;
+                        } else {
+                                /* 'to' is inside of 'from'. */
+                                r = path_simplify_alloc(t, &result);
+                                if (r < 0)
+                                        return r;
+
+                                if (!path_is_valid(result))
+                                        return -EINVAL;
+                        }
+
+                        *ret = TAKE_PTR(result);
+                        return 0;
+                }
+
+                if (r != k || !strneq(f, t, r))
+                        break;
+        }
+
+        /* If we're here, then "from_dir" has one or more elements that need to
+         * be replaced with "..". */
+
+        for (n_parents = 1;; n_parents++) {
+                /* If this includes ".." we can't do a simple series of "..". */
+                r = path_find_first_component(&from, false, &f);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        break;
+        }
+
+        if (isempty(t) && n_parents * 3 > PATH_MAX)
+                /* PATH_MAX is counted *with* the trailing NUL byte */
+                return -EINVAL;
+
+        result = new(char, n_parents * 3 + !isempty(t) + strlen_ptr(t));
+        if (!result)
+                return -ENOMEM;
+
+        for (p = result; n_parents > 0; n_parents--)
+                p = mempcpy(p, "../", 3);
+
+        if (isempty(t)) {
+                /* Remove trailing slash and terminate string. */
+                *(--p) = '\0';
+                *ret = TAKE_PTR(result);
+                return 0;
+        }
+
+        strcpy(p, t);
+
+        path_simplify(result);
+
+        if (!path_is_valid(result))
+                return -EINVAL;
+
+        *ret = TAKE_PTR(result);
+        return 0;
+}
+
+int path_make_relative_parent(const char *from_child, const char *to, char **ret) {
+        _cleanup_free_ char *from = NULL;
+        int r;
+
+        assert(from_child);
+        assert(to);
+        assert(ret);
+
+        /* Similar to path_make_relative(), but provides the relative path from the parent directory of
+         * 'from_child'. This may be useful when creating relative symlink.
+         *
+         * E.g.
+         * - from = "/path/to/aaa", to = "/path/to/bbb"
+         *      path_make_relative(from, to) = "../bbb"
+         *      path_make_relative_parent(from, to) = "bbb"
+         *
+         * - from = "/path/to/aaa/bbb", to = "/path/to/ccc/ddd"
+         *      path_make_relative(from, to) = "../../ccc/ddd"
+         *      path_make_relative_parent(from, to) = "../ccc/ddd"
+         */
+
+        r = path_extract_directory(from_child, &from);
+        if (r < 0)
+                return r;
+
+        return path_make_relative(from, to, ret);
+}
+
+char* path_startswith_strv(const char *p, char **set) {
+        STRV_FOREACH(s, set) {
+                char *t;
+
+                t = path_startswith(p, *s);
+                if (t)
+                        return t;
+        }
+
+        return NULL;
+}
+
+int path_strv_make_absolute_cwd(char **l) {
+        int r;
+
+        /* Goes through every item in the string list and makes it
+         * absolute. This works in place and won't rollback any
+         * changes on failure. */
+
+        STRV_FOREACH(s, l) {
+                char *t;
+
+                r = path_make_absolute_cwd(*s, &t);
+                if (r < 0)
+                        return r;
+
+                path_simplify(t);
+                free_and_replace(*s, t);
+        }
+
+        return 0;
+}
+
+char** path_strv_resolve(char **l, const char *root) {
+        unsigned k = 0;
+        bool enomem = false;
+        int r;
+
+        if (strv_isempty(l))
+                return l;
+
+        /* Goes through every item in the string list and canonicalize
+         * the path. This works in place and won't rollback any
+         * changes on failure. */
+
+        STRV_FOREACH(s, l) {
+                _cleanup_free_ char *orig = NULL;
+                char *t, *u;
+
+                if (!path_is_absolute(*s)) {
+                        free(*s);
+                        continue;
+                }
+
+                if (root) {
+                        orig = *s;
+                        t = path_join(root, orig);
+                        if (!t) {
+                                enomem = true;
+                                continue;
+                        }
+                } else
+                        t = *s;
+
+                r = chase(t, root, 0, &u, NULL);
+                if (r == -ENOENT) {
+                        if (root) {
+                                u = TAKE_PTR(orig);
+                                free(t);
+                        } else
+                                u = t;
+                } else if (r < 0) {
+                        free(t);
+
+                        if (r == -ENOMEM)
+                                enomem = true;
+
+                        continue;
+                } else if (root) {
+                        char *x;
+
+                        free(t);
+                        x = path_startswith(u, root);
+                        if (x) {
+                                /* restore the slash if it was lost */
+                                if (!startswith(x, "/"))
+                                        *(--x) = '/';
+
+                                t = strdup(x);
+                                free(u);
+                                if (!t) {
+                                        enomem = true;
+                                        continue;
+                                }
+                                u = t;
+                        } else {
+                                /* canonicalized path goes outside of
+                                 * prefix, keep the original path instead */
+                                free_and_replace(u, orig);
+                        }
+                } else
+                        free(t);
+
+                l[k++] = u;
+        }
+
+        l[k] = NULL;
+
+        if (enomem)
+                return NULL;
+
+        return l;
+}
+
+char** path_strv_resolve_uniq(char **l, const char *root) {
+
+        if (strv_isempty(l))
+                return l;
+
+        if (!path_strv_resolve(l, root))
+                return NULL;
+
+        return strv_uniq(l);
+}
+
+char* path_simplify_full(char *path, PathSimplifyFlags flags) {
+        bool add_slash = false, keep_trailing_slash, absolute, beginning = true;
+        char *f = path;
+        int r;
+
+        /* Removes redundant inner and trailing slashes. Also removes unnecessary dots.
+         * Modifies the passed string in-place.
+         *
+         * ///foo//./bar/.   becomes /foo/bar
+         * .//./foo//./bar/. becomes foo/bar
+         * /../foo/bar       becomes /foo/bar
+         * /../foo/bar/..    becomes /foo/bar/..
+         */
+
+        if (isempty(path))
+                return path;
+
+        keep_trailing_slash = FLAGS_SET(flags, PATH_SIMPLIFY_KEEP_TRAILING_SLASH) && endswith(path, "/");
+
+        absolute = path_is_absolute(path);
+        f += absolute;  /* Keep leading /, if present. */
+
+        for (const char *p = f;;) {
+                const char *e;
+
+                r = path_find_first_component(&p, true, &e);
+                if (r == 0)
+                        break;
+
+                if (r > 0 && absolute && beginning && path_startswith(e, ".."))
+                        /* If we're at the beginning of an absolute path, we can safely skip ".." */
+                        continue;
+
+                beginning = false;
+
+                if (add_slash)
+                        *f++ = '/';
+
+                if (r < 0) {
+                        /* if path is invalid, then refuse to simplify the remaining part. */
+                        memmove(f, p, strlen(p) + 1);
+                        return path;
+                }
+
+                memmove(f, e, r);
+                f += r;
+
+                add_slash = true;
+        }
+
+        /* Special rule, if we stripped everything, we need a "." for the current directory. */
+        if (f == path)
+                *f++ = '.';
+
+        if (*(f-1) != '/' && keep_trailing_slash)
+                *f++ = '/';
+
+        *f = '\0';
+        return path;
+}
+
+char* path_startswith_full(const char *path, const char *prefix, bool accept_dot_dot) {
+        assert(path);
+        assert(prefix);
+
+        /* Returns a pointer to the start of the first component after the parts matched by
+         * the prefix, iff
+         * - both paths are absolute or both paths are relative,
+         * and
+         * - each component in prefix in turn matches a component in path at the same position.
+         * An empty string will be returned when the prefix and path are equivalent.
+         *
+         * Returns NULL otherwise.
+         */
+
+        if ((path[0] == '/') != (prefix[0] == '/'))
+                return NULL;
+
+        for (;;) {
+                const char *p, *q;
+                int r, k;
+
+                r = path_find_first_component(&path, accept_dot_dot, &p);
+                if (r < 0)
+                        return NULL;
+
+                k = path_find_first_component(&prefix, accept_dot_dot, &q);
+                if (k < 0)
+                        return NULL;
+
+                if (k == 0)
+                        return (char*) (p ?: path);
+
+                if (r != k)
+                        return NULL;
+
+                if (!strneq(p, q, r))
+                        return NULL;
+        }
+}
+
+int path_compare(const char *a, const char *b) {
+        int r;
+
+        /* Order NULL before non-NULL */
+        r = CMP(!!a, !!b);
+        if (r != 0)
+                return r;
+
+        /* A relative path and an absolute path must not compare as equal.
+         * Which one is sorted before the other does not really matter.
+         * Here a relative path is ordered before an absolute path. */
+        r = CMP(path_is_absolute(a), path_is_absolute(b));
+        if (r != 0)
+                return r;
+
+        for (;;) {
+                const char *aa, *bb;
+                int j, k;
+
+                j = path_find_first_component(&a, true, &aa);
+                k = path_find_first_component(&b, true, &bb);
+
+                if (j < 0 || k < 0) {
+                        /* When one of paths is invalid, order invalid path after valid one. */
+                        r = CMP(j < 0, k < 0);
+                        if (r != 0)
+                                return r;
+
+                        /* fallback to use strcmp() if both paths are invalid. */
+                        return strcmp(a, b);
+                }
+
+                /* Order prefixes first: "/foo" before "/foo/bar" */
+                if (j == 0) {
+                        if (k == 0)
+                                return 0;
+                        return -1;
+                }
+                if (k == 0)
+                        return 1;
+
+                /* Alphabetical sort: "/foo/aaa" before "/foo/b" */
+                r = memcmp(aa, bb, MIN(j, k));
+                if (r != 0)
+                        return r;
+
+                /* Sort "/foo/a" before "/foo/aaa" */
+                r = CMP(j, k);
+                if (r != 0)
+                        return r;
+        }
+}
+
+int path_compare_filename(const char *a, const char *b) {
+        _cleanup_free_ char *fa = NULL, *fb = NULL;
+        int r, j, k;
+
+        /* Order NULL before non-NULL */
+        r = CMP(!!a, !!b);
+        if (r != 0)
+                return r;
+
+        j = path_extract_filename(a, &fa);
+        k = path_extract_filename(b, &fb);
+
+        /* When one of paths is "." or root, then order it earlier. */
+        r = CMP(j != -EADDRNOTAVAIL, k != -EADDRNOTAVAIL);
+        if (r != 0)
+                return r;
+
+        /* When one of paths is invalid (or we get OOM), order invalid path after valid one. */
+        r = CMP(j < 0, k < 0);
+        if (r != 0)
+                return r;
+
+        /* fallback to use strcmp() if both paths are invalid. */
+        if (j < 0)
+                return strcmp(a, b);
+
+        return strcmp(fa, fb);
+}
+
+char* path_extend_internal(char **x, ...) {
+        size_t sz, old_sz;
+        char *q, *nx;
+        const char *p;
+        va_list ap;
+        bool slash;
+
+        /* Joins all listed strings until the sentinel and places a "/" between them unless the strings
+         * end/begin already with one so that it is unnecessary. Note that slashes which are already
+         * duplicate won't be removed. The string returned is hence always equal to or longer than the sum of
+         * the lengths of the individual strings.
+         *
+         * The first argument may be an already allocated string that is extended via realloc() if
+         * non-NULL. path_extend() and path_join() are macro wrappers around this function, making use of the
+         * first parameter to distinguish the two operations.
+         *
+         * Note: any listed empty string is simply skipped. This can be useful for concatenating strings of
+         * which some are optional.
+         *
+         * Examples:
+         *
+         * path_join("foo", "bar") → "foo/bar"
+         * path_join("foo/", "bar") → "foo/bar"
+         * path_join("", "foo", "", "bar", "") → "foo/bar" */
+
+        sz = old_sz = x ? strlen_ptr(*x) : 0;
+        va_start(ap, x);
+        while ((p = va_arg(ap, char*)) != POINTER_MAX) {
+                size_t add;
+
+                if (isempty(p))
+                        continue;
+
+                add = 1 + strlen(p);
+                if (sz > SIZE_MAX - add) { /* overflow check */
+                        va_end(ap);
+                        return NULL;
+                }
+
+                sz += add;
+        }
+        va_end(ap);
+
+        nx = realloc(x ? *x : NULL, GREEDY_ALLOC_ROUND_UP(sz+1));
+        if (!nx)
+                return NULL;
+        if (x)
+                *x = nx;
+
+        if (old_sz > 0)
+                slash = nx[old_sz-1] == '/';
+        else {
+                nx[old_sz] = 0;
+                slash = true; /* no need to generate a slash anymore */
+        }
+
+        q = nx + old_sz;
+
+        va_start(ap, x);
+        while ((p = va_arg(ap, char*)) != POINTER_MAX) {
+                if (isempty(p))
+                        continue;
+
+                if (!slash && p[0] != '/')
+                        *(q++) = '/';
+
+                q = stpcpy(q, p);
+                slash = endswith(p, "/");
+        }
+        va_end(ap);
+
+        return nx;
+}
+
+static int check_x_access(const char *path, int *ret_fd) {
+        _cleanup_close_ int fd = -EBADF;
+        int r;
+
+        /* We need to use O_PATH because there may be executables for which we have only exec
+         * permissions, but not read (usually suid executables). */
+        fd = open(path, O_PATH|O_CLOEXEC);
+        if (fd < 0)
+                return -errno;
+
+        r = fd_verify_regular(fd);
+        if (r < 0)
+                return r;
+
+        r = access_fd(fd, X_OK);
+        if (r == -ENOSYS) {
+                /* /proc is not mounted. Fallback to access(). */
+                if (access(path, X_OK) < 0)
+                        return -errno;
+        } else if (r < 0)
+                return r;
+
+        if (ret_fd)
+                *ret_fd = TAKE_FD(fd);
+
+        return 0;
+}
+
+static int find_executable_impl(const char *name, const char *root, char **ret_filename, int *ret_fd) {
+        _cleanup_close_ int fd = -EBADF;
+        _cleanup_free_ char *path_name = NULL;
+        int r;
+
+        assert(name);
+
+        /* Function chase() is invoked only when root is not NULL, as using it regardless of
+         * root value would alter the behavior of existing callers for example: /bin/sleep would become
+         * /usr/bin/sleep when find_executables is called. Hence, this function should be invoked when
+         * needed to avoid unforeseen regression or other complicated changes. */
+        if (root) {
+                 /* prefix root to name in case full paths are not specified */
+                r = chase(name, root, CHASE_PREFIX_ROOT, &path_name, /* ret_fd= */ NULL);
+                if (r < 0)
+                        return r;
+
+                name = path_name;
+        }
+
+        r = check_x_access(name, ret_fd ? &fd : NULL);
+        if (r < 0)
+                return r;
+
+        if (ret_filename) {
+                r = path_make_absolute_cwd(name, ret_filename);
+                if (r < 0)
+                        return r;
+        }
+
+        if (ret_fd)
+                *ret_fd = TAKE_FD(fd);
+
+        return 0;
+}
+
+int find_executable_full(
+                const char *name,
+                const char *root,
+                char **exec_search_path,
+                bool use_path_envvar,
+                char **ret_filename,
+                int *ret_fd) {
+
+        int last_error = -ENOENT, r = 0;
+        const char *p = NULL;
+
+        assert(name);
+
+        if (is_path(name))
+                return find_executable_impl(name, root, ret_filename, ret_fd);
+
+        if (use_path_envvar)
+                /* Plain getenv, not secure_getenv, because we want to actually allow the user to pick the
+                 * binary. */
+                p = getenv("PATH");
+        if (!p)
+                p = DEFAULT_PATH;
+
+        if (exec_search_path) {
+                STRV_FOREACH(element, exec_search_path) {
+                        _cleanup_free_ char *full_path = NULL;
+
+                        if (!path_is_absolute(*element))
+                                continue;
+
+                        full_path = path_join(*element, name);
+                        if (!full_path)
+                                return -ENOMEM;
+
+                        r = find_executable_impl(full_path, root, ret_filename, ret_fd);
+                        if (r < 0) {
+                                if (r != -EACCES)
+                                        last_error = r;
+                                continue;
+                        }
+                        return 0;
+                }
+                return last_error;
+        }
+
+        /* Resolve a single-component name to a full path */
+        for (;;) {
+                _cleanup_free_ char *element = NULL;
+
+                r = extract_first_word(&p, &element, ":", EXTRACT_RELAX|EXTRACT_DONT_COALESCE_SEPARATORS);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        break;
+
+                if (!path_is_absolute(element))
+                        continue;
+
+                if (!path_extend(&element, name))
+                        return -ENOMEM;
+
+                r = find_executable_impl(element, root, ret_filename, ret_fd);
+                if (r < 0) {
+                        /* PATH entries which we don't have access to are ignored, as per tradition. */
+                        if (r != -EACCES)
+                                last_error = r;
+                        continue;
+                }
+
+                /* Found it! */
+                return 0;
+        }
+
+        return last_error;
+}
+
+bool paths_check_timestamp(const char* const* paths, usec_t *timestamp, bool update) {
+        bool changed = false, originally_unset;
+
+        assert(timestamp);
+
+        if (!paths)
+                return false;
+
+        originally_unset = *timestamp == 0;
+
+        STRV_FOREACH(i, paths) {
+                struct stat stats;
+                usec_t u;
+
+                if (stat(*i, &stats) < 0)
+                        continue;
+
+                u = timespec_load(&stats.st_mtim);
+
+                /* check first */
+                if (*timestamp >= u)
+                        continue;
+
+                log_debug(originally_unset ? "Loaded timestamp for '%s'." : "Timestamp of '%s' changed.", *i);
+
+                /* update timestamp */
+                if (update) {
+                        *timestamp = u;
+                        changed = true;
+                } else
+                        return true;
+        }
+
+        return changed;
+}
+
+static int executable_is_good(const char *executable) {
+        _cleanup_free_ char *p = NULL, *d = NULL;
+        int r;
+
+        r = find_executable(executable, &p);
+        if (r == -ENOENT)
+                return 0;
+        if (r < 0)
+                return r;
+
+        /* An fsck that is linked to /bin/true is a non-existent fsck */
+
+        r = readlink_malloc(p, &d);
+        if (r == -EINVAL) /* not a symlink */
+                return 1;
+        if (r < 0)
+                return r;
+
+        return !PATH_IN_SET(d, "true"
+                               "/bin/true",
+                               "/usr/bin/true",
+                               "/dev/null");
+}
+
+int fsck_exists(void) {
+        return executable_is_good("fsck");
+}
+
+int fsck_exists_for_fstype(const char *fstype) {
+        const char *checker;
+        int r;
+
+        assert(fstype);
+
+        if (streq(fstype, "auto"))
+                return -EINVAL;
+
+        r = fsck_exists();
+        if (r <= 0)
+                return r;
+
+        checker = strjoina("fsck.", fstype);
+        return executable_is_good(checker);
+}
+
+static const char* skip_slash_or_dot(const char *p) {
+        for (; !isempty(p); p++) {
+                if (*p == '/')
+                        continue;
+                if (startswith(p, "./")) {
+                        p++;
+                        continue;
+                }
+                break;
+        }
+        return p;
+}
+
+int path_find_first_component(const char **p, bool accept_dot_dot, const char **ret) {
+        const char *q, *first, *end_first, *next;
+        size_t len;
+
+        assert(p);
+
+        /* When a path is input, then returns the pointer to the first component and its length, and
+         * move the input pointer to the next component or nul. This skips both over any '/'
+         * immediately *before* and *after* the first component before returning.
+         *
+         * Examples
+         *   Input:  p: "//.//aaa///bbbbb/cc"
+         *   Output: p: "bbbbb///cc"
+         *           ret: "aaa///bbbbb/cc"
+         *           return value: 3 (== strlen("aaa"))
+         *
+         *   Input:  p: "aaa//"
+         *   Output: p: (pointer to NUL)
+         *           ret: "aaa//"
+         *           return value: 3 (== strlen("aaa"))
+         *
+         *   Input:  p: "/", ".", ""
+         *   Output: p: (pointer to NUL)
+         *           ret: NULL
+         *           return value: 0
+         *
+         *   Input:  p: NULL
+         *   Output: p: NULL
+         *           ret: NULL
+         *           return value: 0
+         *
+         *   Input:  p: "(too long component)"
+         *   Output: return value: -EINVAL
+         *
+         *   (when accept_dot_dot is false)
+         *   Input:  p: "//..//aaa///bbbbb/cc"
+         *   Output: return value: -EINVAL
+         */
+
+        q = *p;
+
+        first = skip_slash_or_dot(q);
+        if (isempty(first)) {
+                *p = first;
+                if (ret)
+                        *ret = NULL;
+                return 0;
+        }
+        if (streq(first, ".")) {
+                *p = first + 1;
+                if (ret)
+                        *ret = NULL;
+                return 0;
+        }
+
+        end_first = strchrnul(first, '/');
+        len = end_first - first;
+
+        if (len > NAME_MAX)
+                return -EINVAL;
+        if (!accept_dot_dot && len == 2 && first[0] == '.' && first[1] == '.')
+                return -EINVAL;
+
+        next = skip_slash_or_dot(end_first);
+
+        *p = next + streq(next, ".");
+        if (ret)
+                *ret = first;
+        return len;
+}
+
+static const char* skip_slash_or_dot_backward(const char *path, const char *q) {
+        assert(path);
+        assert(!q || q >= path);
+
+        for (; q; q = PTR_SUB1(q, path)) {
+                if (*q == '/')
+                        continue;
+                if (q > path && strneq(q - 1, "/.", 2))
+                        continue;
+                if (q == path && *q == '.')
+                        continue;
+                break;
+        }
+        return q;
+}
+
+int path_find_last_component(const char *path, bool accept_dot_dot, const char **next, const char **ret) {
+        const char *q, *last_end, *last_begin;
+        size_t len;
+
+        /* Similar to path_find_first_component(), but search components from the end.
+        *
+        * Examples
+        *   Input:  path: "//.//aaa///bbbbb/cc//././"
+        *           next: NULL
+        *   Output: next: "/cc//././"
+        *           ret: "cc//././"
+        *           return value: 2 (== strlen("cc"))
+        *
+        *   Input:  path: "//.//aaa///bbbbb/cc//././"
+        *           next: "/cc//././"
+        *   Output: next: "///bbbbb/cc//././"
+        *           ret: "bbbbb/cc//././"
+        *           return value: 5 (== strlen("bbbbb"))
+        *
+        *   Input:  path: "//.//aaa///bbbbb/cc//././"
+        *           next: "///bbbbb/cc//././"
+        *   Output: next: "//.//aaa///bbbbb/cc//././" (next == path)
+        *           ret: "aaa///bbbbb/cc//././"
+        *           return value: 3 (== strlen("aaa"))
+        *
+        *   Input:  path: "/", ".", "", or NULL
+        *   Output: next: equivalent to path
+        *           ret: NULL
+        *           return value: 0
+        *
+        *   Input:  path: "(too long component)"
+        *   Output: return value: -EINVAL
+        *
+        *   (when accept_dot_dot is false)
+        *   Input:  path: "//..//aaa///bbbbb/cc/..//"
+        *   Output: return value: -EINVAL
+        */
+
+        if (isempty(path)) {
+                if (next)
+                        *next = path;
+                if (ret)
+                        *ret = NULL;
+                return 0;
+        }
+
+        if (next && *next) {
+                if (*next < path || *next > path + strlen(path))
+                        return -EINVAL;
+                if (*next == path) {
+                        if (ret)
+                                *ret = NULL;
+                        return 0;
+                }
+                if (!IN_SET(**next, '\0', '/'))
+                        return -EINVAL;
+                q = *next - 1;
+        } else
+                q = path + strlen(path) - 1;
+
+        q = skip_slash_or_dot_backward(path, q);
+        if (!q || /* the root directory */
+            (q == path && *q == '.')) { /* path is "." or "./" */
+                if (next)
+                        *next = path;
+                if (ret)
+                        *ret = NULL;
+                return 0;
+        }
+
+        last_end = q + 1;
+
+        while (q && *q != '/')
+                q = PTR_SUB1(q, path);
+
+        last_begin = q ? q + 1 : path;
+        len = last_end - last_begin;
+
+        if (len > NAME_MAX)
+                return -EINVAL;
+        if (!accept_dot_dot && len == 2 && strneq(last_begin, "..", 2))
+                return -EINVAL;
+
+        if (next) {
+                q = skip_slash_or_dot_backward(path, q);
+                *next = q ? q + 1 : path;
+        }
+
+        if (ret)
+                *ret = last_begin;
+        return len;
+}
+
+const char* last_path_component(const char *path) {
+
+        /* Finds the last component of the path, preserving the optional trailing slash that signifies a directory.
+         *
+         *    a/b/c → c
+         *    a/b/c/ → c/
+         *    x → x
+         *    x/ → x/
+         *    /y → y
+         *    /y/ → y/
+         *    / → /
+         *    // → /
+         *    /foo/a → a
+         *    /foo/a/ → a/
+         *
+         *    Also, the empty string is mapped to itself.
+         *
+         * This is different than basename(), which returns "" when a trailing slash is present.
+         *
+         * This always succeeds (except if you pass NULL in which case it returns NULL, too).
+         */
+
+        unsigned l, k;
+
+        if (!path)
+                return NULL;
+
+        l = k = strlen(path);
+        if (l == 0) /* special case — an empty string */
+                return path;
+
+        while (k > 0 && path[k-1] == '/')
+                k--;
+
+        if (k == 0) /* the root directory */
+                return path + l - 1;
+
+        while (k > 0 && path[k-1] != '/')
+                k--;
+
+        return path + k;
+}
+
+int path_extract_filename(const char *path, char **ret) {
+        _cleanup_free_ char *a = NULL;
+        const char *c, *next = NULL;
+        int r;
+
+        /* Extracts the filename part (i.e. right-most component) from a path, i.e. string that passes
+         * filename_is_valid(). A wrapper around last_path_component(), but eats up trailing
+         * slashes. Returns:
+         *
+         * -EINVAL        → if the path is not valid
+         * -EADDRNOTAVAIL → if only a directory was specified, but no filename, i.e. the root dir
+         *                  itself or "." is specified
+         * -ENOMEM        → no memory
+         *
+         * Returns >= 0 on success. If the input path has a trailing slash, returns O_DIRECTORY, to
+         * indicate the referenced file must be a directory.
+         *
+         * This function guarantees to return a fully valid filename, i.e. one that passes
+         * filename_is_valid() – this means "." and ".." are not accepted. */
+
+        if (!path_is_valid(path))
+                return -EINVAL;
+
+        r = path_find_last_component(path, false, &next, &c);
+        if (r < 0)
+                return r;
+        if (r == 0) /* root directory */
+                return -EADDRNOTAVAIL;
+
+        a = strndup(c, r);
+        if (!a)
+                return -ENOMEM;
+
+        *ret = TAKE_PTR(a);
+        return strlen(c) > (size_t) r ? O_DIRECTORY : 0;
+}
+
+int path_extract_directory(const char *path, char **ret) {
+        _cleanup_free_ char *a = NULL;
+        const char *c, *next = NULL;
+        int r;
+
+        /* The inverse of path_extract_filename(), i.e. returns the directory path prefix. Returns:
+         *
+         * -EINVAL        → if the path is not valid
+         * -EDESTADDRREQ  → if no directory was specified in the passed in path, i.e. only a filename was passed
+         * -EADDRNOTAVAIL → if the passed in parameter had no filename but did have a directory, i.e.
+         *                   the root dir itself or "." was specified
+         * -ENOMEM        → no memory (surprise!)
+         *
+         * This function guarantees to return a fully valid path, i.e. one that passes path_is_valid().
+         */
+
+        r = path_find_last_component(path, false, &next, &c);
+        if (r < 0)
+                return r;
+        if (r == 0) /* empty or root */
+                return isempty(path) ? -EINVAL : -EADDRNOTAVAIL;
+        if (next == path) {
+                if (*path != '/') /* filename only */
+                        return -EDESTADDRREQ;
+
+                a = strdup("/");
+                if (!a)
+                        return -ENOMEM;
+                *ret = TAKE_PTR(a);
+                return 0;
+        }
+
+        a = strndup(path, next - path);
+        if (!a)
+                return -ENOMEM;
+
+        path_simplify(a);
+
+        if (!path_is_valid(a))
+                return -EINVAL;
+
+        if (ret)
+                *ret = TAKE_PTR(a);
+
+        return 0;
+}
+
+bool filename_part_is_valid(const char *p) {
+        const char *e;
+
+        /* Checks f the specified string is OK to be *part* of a filename. This is different from
+         * filename_is_valid() as "." and ".." and "" are OK by this call, but not by filename_is_valid(). */
+
+        if (!p)
+                return false;
+
+        e = strchrnul(p, '/');
+        if (*e != 0)
+                return false;
+
+        if (e - p > NAME_MAX) /* NAME_MAX is counted *without* the trailing NUL byte */
+                return false;
+
+        return true;
+}
+
+bool filename_is_valid(const char *p) {
+
+        if (isempty(p))
+                return false;
+
+        if (dot_or_dot_dot(p)) /* Yes, in this context we consider "." and ".." invalid */
+                return false;
+
+        return filename_part_is_valid(p);
+}
+
+bool path_is_valid_full(const char *p, bool accept_dot_dot) {
+        if (isempty(p))
+                return false;
+
+        for (const char *e = p;;) {
+                int r;
+
+                r = path_find_first_component(&e, accept_dot_dot, NULL);
+                if (r < 0)
+                        return false;
+
+                if (e - p >= PATH_MAX) /* Already reached the maximum length for a path? (PATH_MAX is counted
+                                        * *with* the trailing NUL byte) */
+                        return false;
+                if (*e == 0)           /* End of string? Yay! */
+                        return true;
+        }
+}
+
+bool path_is_normalized(const char *p) {
+        if (!path_is_safe(p))
+                return false;
+
+        if (streq(p, ".") || startswith(p, "./") || endswith(p, "/.") || strstr(p, "/./"))
+                return false;
+
+        if (strstr(p, "//"))
+                return false;
+
+        return true;
+}
+
+int file_in_same_dir(const char *path, const char *filename, char **ret) {
+        _cleanup_free_ char *b = NULL;
+        int r;
+
+        assert(path);
+        assert(filename);
+        assert(ret);
+
+        /* This removes the last component of path and appends filename, unless the latter is absolute anyway
+         * or the former isn't */
+
+        if (path_is_absolute(filename))
+                b = strdup(filename);
+        else {
+                _cleanup_free_ char *dn = NULL;
+
+                r = path_extract_directory(path, &dn);
+                if (r == -EDESTADDRREQ) /* no path prefix */
+                        b = strdup(filename);
+                else if (r < 0)
+                        return r;
+                else
+                        b = path_join(dn, filename);
+        }
+        if (!b)
+                return -ENOMEM;
+
+        *ret = TAKE_PTR(b);
+        return 0;
+}
+
+bool hidden_or_backup_file(const char *filename) {
+        assert(filename);
+
+        if (filename[0] == '.' ||
+            STR_IN_SET(filename,
+                       "lost+found",
+                       "aquota.user",
+                       "aquota.group") ||
+            endswith(filename, "~"))
+                return true;
+
+        const char *dot = strrchr(filename, '.');
+        if (!dot)
+                return false;
+
+        /* Please, let's not add more entries to the list below. If external projects think it's a good idea
+         * to come up with always new suffixes and that everybody else should just adjust to that, then it
+         * really should be on them. Hence, in future, let's not add any more entries. Instead, let's ask
+         * those packages to instead adopt one of the generic suffixes/prefixes for hidden files or backups,
+         * possibly augmented with an additional string. Specifically: there's now:
+         *
+         *    The generic suffixes "~" and ".bak" for backup files
+         *    The generic prefix "." for hidden files
+         *
+         * Thus, if a new package manager "foopkg" wants its own set of ".foopkg-new", ".foopkg-old",
+         * ".foopkg-dist" or so registered, let's refuse that and ask them to use ".foopkg.new",
+         * ".foopkg.old" or ".foopkg~" instead.
+         */
+
+        return STR_IN_SET(dot + 1,
+                          "rpmnew",
+                          "rpmsave",
+                          "rpmorig",
+                          "dpkg-old",
+                          "dpkg-new",
+                          "dpkg-tmp",
+                          "dpkg-dist",
+                          "dpkg-bak",
+                          "dpkg-backup",
+                          "dpkg-remove",
+                          "ucf-new",
+                          "ucf-old",
+                          "ucf-dist",
+                          "swp",
+                          "bak",
+                          "old",
+                          "new");
+}
+
+bool is_device_path(const char *path) {
+
+        /* Returns true for paths that likely refer to a device, either by path in sysfs or to something in
+         * /dev. This accepts any path that starts with /dev/ or /sys/ and has something after that prefix.
+         * It does not actually resolve the path.
+         *
+         * Examples:
+         * /dev/sda, /dev/sda/foo, /sys/class, /dev/.., /sys/.., /./dev/foo → yes.
+         * /../dev/sda, /dev, /sys, /usr/path, /usr/../dev/sda → no.
+         */
+
+        const char *p = PATH_STARTSWITH_SET(ASSERT_PTR(path), "/dev/", "/sys/");
+        return !isempty(p);
+}
+
+bool valid_device_node_path(const char *path) {
+
+        /* Some superficial checks whether the specified path is a valid device node path, all without
+         * looking at the actual device node. */
+
+        if (!PATH_STARTSWITH_SET(path, "/dev/", "/run/systemd/inaccessible/"))
+                return false;
+
+        if (endswith(path, "/")) /* can't be a device node if it ends in a slash */
+                return false;
+
+        return path_is_normalized(path);
+}
+
+bool valid_device_allow_pattern(const char *path) {
+        assert(path);
+
+        /* Like valid_device_node_path(), but also allows full-subsystem expressions like those accepted by
+         * DeviceAllow= and DeviceDeny=. */
+
+        if (STARTSWITH_SET(path, "block-", "char-"))
+                return true;
+
+        return valid_device_node_path(path);
+}
+
+bool dot_or_dot_dot(const char *path) {
+        if (!path)
+                return false;
+        if (path[0] != '.')
+                return false;
+        if (path[1] == 0)
+                return true;
+        if (path[1] != '.')
+                return false;
+
+        return path[2] == 0;
+}
+
+bool empty_or_root(const char *path) {
+
+        /* For operations relative to some root directory, returns true if the specified root directory is
+         * redundant, i.e. either / or NULL or the empty string or any equivalent. */
+
+        if (isempty(path))
+                return true;
+
+        return path_equal(path, "/");
+}
+
+bool path_strv_contains(char **l, const char *path) {
+        STRV_FOREACH(i, l)
+                if (path_equal(*i, path))
+                        return true;
+
+        return false;
+}
+
+bool prefixed_path_strv_contains(char **l, const char *path) {
+        STRV_FOREACH(i, l) {
+                const char *j = *i;
+
+                if (*j == '-')
+                        j++;
+                if (*j == '+')
+                        j++;
+                if (path_equal(j, path))
+                        return true;
+        }
+
+        return false;
+}
+
+int path_glob_can_match(const char *pattern, const char *prefix, char **ret) {
+        assert(pattern);
+        assert(prefix);
+
+        for (const char *a = pattern, *b = prefix;;) {
+                _cleanup_free_ char *g = NULL, *h = NULL;
+                const char *p, *q;
+                int r, s;
+
+                r = path_find_first_component(&a, /* accept_dot_dot = */ false, &p);
+                if (r < 0)
+                        return r;
+
+                s = path_find_first_component(&b, /* accept_dot_dot = */ false, &q);
+                if (s < 0)
+                        return s;
+
+                if (s == 0) {
+                        /* The pattern matches the prefix. */
+                        if (ret) {
+                                char *t;
+
+                                t = path_join(prefix, p);
+                                if (!t)
+                                        return -ENOMEM;
+
+                                *ret = t;
+                        }
+                        return true;
+                }
+
+                if (r == 0)
+                        break;
+
+                if (r == s && strneq(p, q, r))
+                        continue; /* common component. Check next. */
+
+                g = strndup(p, r);
+                if (!g)
+                        return -ENOMEM;
+
+                if (!string_is_glob(g))
+                        break;
+
+                /* We found a glob component. Check if the glob pattern matches the prefix component. */
+
+                h = strndup(q, s);
+                if (!h)
+                        return -ENOMEM;
+
+                r = fnmatch(g, h, 0);
+                if (r == FNM_NOMATCH)
+                        break;
+                if (r != 0) /* Failure to process pattern? */
+                        return -EINVAL;
+        }
+
+        /* The pattern does not match the prefix. */
+        if (ret)
+                *ret = NULL;
+        return false;
+}