diff options
Diffstat (limited to 'src/basic/chase.c')
| -rw-r--r-- | src/basic/chase.c | 1156 |
1 files changed, 1156 insertions, 0 deletions
diff --git a/src/basic/chase.c b/src/basic/chase.c new file mode 100644 index 0000000..26bc2d6 --- /dev/null +++ b/src/basic/chase.c @@ -0,0 +1,1156 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ + +#include <linux/magic.h> + +#include "alloc-util.h" +#include "chase.h" +#include "fd-util.h" +#include "fileio.h" +#include "fs-util.h" +#include "glyph-util.h" +#include "log.h" +#include "path-util.h" +#include "string-util.h" +#include "user-util.h" + +bool unsafe_transition(const struct stat *a, const struct stat *b) { + /* Returns true if the transition from a to b is safe, i.e. that we never transition from unprivileged to + * privileged files or directories. Why bother? So that unprivileged code can't symlink to privileged files + * making us believe we read something safe even though it isn't safe in the specific context we open it in. */ + + if (a->st_uid == 0) /* Transitioning from privileged to unprivileged is always fine */ + return false; + + return a->st_uid != b->st_uid; /* Otherwise we need to stay within the same UID */ +} + +static int log_unsafe_transition(int a, int b, const char *path, ChaseFlags flags) { + _cleanup_free_ char *n1 = NULL, *n2 = NULL, *user_a = NULL, *user_b = NULL; + struct stat st; + + if (!FLAGS_SET(flags, CHASE_WARN)) + return -ENOLINK; + + (void) fd_get_path(a, &n1); + (void) fd_get_path(b, &n2); + + if (fstat(a, &st) == 0) + user_a = uid_to_name(st.st_uid); + if (fstat(b, &st) == 0) + user_b = uid_to_name(st.st_uid); + + return log_warning_errno(SYNTHETIC_ERRNO(ENOLINK), + "Detected unsafe path transition %s (owned by %s) %s %s (owned by %s) during canonicalization of %s.", + strna(n1), strna(user_a), special_glyph(SPECIAL_GLYPH_ARROW_RIGHT), strna(n2), strna(user_b), path); +} + +static int log_autofs_mount_point(int fd, const char *path, ChaseFlags flags) { + _cleanup_free_ char *n1 = NULL; + + if (!FLAGS_SET(flags, CHASE_WARN)) + return -EREMOTE; + + (void) fd_get_path(fd, &n1); + + return log_warning_errno(SYNTHETIC_ERRNO(EREMOTE), + "Detected autofs mount point %s during canonicalization of %s.", + strna(n1), path); +} + +static int log_prohibited_symlink(int fd, ChaseFlags flags) { + _cleanup_free_ char *n1 = NULL; + + assert(fd >= 0); + + if (!FLAGS_SET(flags, CHASE_WARN)) + return -EREMCHG; + + (void) fd_get_path(fd, &n1); + + return log_warning_errno(SYNTHETIC_ERRNO(EREMCHG), + "Detected symlink where not symlink is allowed at %s, refusing.", + strna(n1)); +} + +static int chaseat_needs_absolute(int dir_fd, const char *path) { + if (dir_fd < 0) + return path_is_absolute(path); + + return dir_fd_is_root(dir_fd); +} + +int chaseat(int dir_fd, const char *path, ChaseFlags flags, char **ret_path, int *ret_fd) { + _cleanup_free_ char *buffer = NULL, *done = NULL; + _cleanup_close_ int fd = -EBADF, root_fd = -EBADF; + unsigned max_follow = CHASE_MAX; /* how many symlinks to follow before giving up and returning ELOOP */ + bool exists = true, append_trail_slash = false; + struct stat st; /* stat obtained from fd */ + const char *todo; + int r; + + assert(!FLAGS_SET(flags, CHASE_PREFIX_ROOT)); + assert(!FLAGS_SET(flags, CHASE_STEP|CHASE_EXTRACT_FILENAME)); + assert(!FLAGS_SET(flags, CHASE_TRAIL_SLASH|CHASE_EXTRACT_FILENAME)); + assert(!FLAGS_SET(flags, CHASE_MKDIR_0755) || (flags & (CHASE_NONEXISTENT | CHASE_PARENT)) != 0); + assert(dir_fd >= 0 || dir_fd == AT_FDCWD); + + /* Either the file may be missing, or we return an fd to the final object, but both make no sense */ + if (FLAGS_SET(flags, CHASE_NONEXISTENT)) + assert(!ret_fd); + + if (FLAGS_SET(flags, CHASE_STEP)) + assert(!ret_fd); + + if (isempty(path)) + path = "."; + + /* This function resolves symlinks of the path relative to the given directory file descriptor. If + * CHASE_AT_RESOLVE_IN_ROOT is specified and a directory file descriptor is provided, symlinks + * are resolved relative to the given directory file descriptor. Otherwise, they are resolved + * relative to the root directory of the host. + * + * Note that when a positive directory file descriptor is provided and CHASE_AT_RESOLVE_IN_ROOT is + * specified and we find an absolute symlink, it is resolved relative to given directory file + * descriptor and not the root of the host. Also, when following relative symlinks, this functions + * ensures they cannot be used to "escape" the given directory file descriptor. If a positive + * directory file descriptor is provided, the "path" parameter is always interpreted relative to the + * given directory file descriptor, even if it is absolute. If the given directory file descriptor is + * AT_FDCWD and "path" is absolute, it is interpreted relative to the root directory of the host. + * + * When "dir_fd" points to a non-root directory and CHASE_AT_RESOLVE_IN_ROOT is set, this function + * always returns a relative path in "ret_path", even if "path" is an absolute path, because openat() + * like functions generally ignore the directory fd if they are provided with an absolute path. When + * CHASE_AT_RESOLVE_IN_ROOT is not set, then this returns relative path to the specified file + * descriptor if all resolved symlinks are relative, otherwise absolute path will be returned. When + * "dir_fd" is AT_FDCWD and "path" is an absolute path, we return an absolute path in "ret_path" + * because otherwise, if the caller passes the returned relative path to another openat() like + * function, it would be resolved relative to the current working directory instead of to "/". + * + * Summary about the result path: + * - "dir_fd" points to the root directory + * → result will be absolute + * - "dir_fd" points to a non-root directory, and CHASE_AT_RESOLVE_IN_ROOT is set + * → relative + * - "dir_fd" points to a non-root directory, and CHASE_AT_RESOLVE_IN_ROOT is not set + * → relative when all resolved symlinks are relative, otherwise absolute + * - "dir_fd" is AT_FDCWD, and "path" is absolute + * → absolute + * - "dir_fd" is AT_FDCWD, and "path" is relative + * → relative when all resolved symlinks are relative, otherwise absolute + * + * 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 + * its special meaning each time. We always keep an O_PATH fd to the component we are currently + * processing, thus keeping lookup races to 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 + * "dir_fd" parameter to tell this function what to do when encountering a symlink with an absolute + * path as directory: resolve it relative to the given directory file descriptor. + * + * There are five ways to invoke this function: + * + * 1. Without CHASE_STEP or ret_fd: in this case the path is resolved and the normalized path is + * returned in `ret_path`. The return value is < 0 on error. If CHASE_NONEXISTENT is also set, 0 + * is returned if the file doesn't exist, > 0 otherwise. If CHASE_NONEXISTENT is not set, >= 0 is + * returned if the destination was found, -ENOENT if it wasn't. + * + * 2. With ret_fd: in this case the destination is opened after chasing it as O_PATH and this file + * descriptor is returned as return value. This is useful to open files relative to some root + * directory. Note that the returned O_PATH file descriptors must be converted into a regular one + * (using fd_reopen() or such) before it can be used for reading/writing. ret_fd may not be + * combined with CHASE_NONEXISTENT. + * + * 3. With CHASE_STEP: in this case only a single step of the normalization is executed, i.e. only + * the first symlink or ".." component of the path is resolved, and the resulting path is + * returned. This is useful if a caller wants to trace the path through the file system verbosely. + * Returns < 0 on error, > 0 if the path is fully normalized, and == 0 for each normalization + * step. This may be combined with CHASE_NONEXISTENT, in which case 1 is returned when a component + * is not found. + * + * 4. With CHASE_SAFE: in this case the path must not contain unsafe transitions, i.e. transitions + * from unprivileged to privileged files or directories. In such cases the return value is + * -ENOLINK. If CHASE_WARN is also set, a warning describing the unsafe transition is emitted. + * CHASE_WARN cannot be used in PID 1. + * + * 5. With CHASE_NO_AUTOFS: in this case if an autofs mount point is encountered, path normalization + * is aborted and -EREMOTE is returned. If CHASE_WARN is also set, a warning showing the path of + * the mount point is emitted. CHASE_WARN cannot be used in PID 1. + */ + + if (FLAGS_SET(flags, CHASE_AT_RESOLVE_IN_ROOT)) { + /* If we get AT_FDCWD or dir_fd points to "/", then we always resolve symlinks relative to + * the host's root. Hence, CHASE_AT_RESOLVE_IN_ROOT is meaningless. */ + + r = dir_fd_is_root_or_cwd(dir_fd); + if (r < 0) + return r; + if (r > 0) + flags &= ~CHASE_AT_RESOLVE_IN_ROOT; + } + + if (!(flags & + (CHASE_AT_RESOLVE_IN_ROOT|CHASE_NONEXISTENT|CHASE_NO_AUTOFS|CHASE_SAFE|CHASE_STEP| + CHASE_PROHIBIT_SYMLINKS|CHASE_MKDIR_0755)) && + !ret_path && ret_fd) { + + /* Shortcut the ret_fd case if the caller isn't interested in the actual path and has no root + * set and doesn't care about any of the other special features we provide either. */ + r = openat(dir_fd, path, O_PATH|O_CLOEXEC|(FLAGS_SET(flags, CHASE_NOFOLLOW) ? O_NOFOLLOW : 0)); + if (r < 0) + return -errno; + + *ret_fd = r; + return 0; + } + + buffer = strdup(path); + if (!buffer) + return -ENOMEM; + + /* If we receive an absolute path together with AT_FDCWD, we need to return an absolute path, because + * a relative path would be interpreted relative to the current working directory. Also, let's make + * the result absolute when the file descriptor of the root directory is specified. */ + r = chaseat_needs_absolute(dir_fd, path); + if (r < 0) + return r; + + bool need_absolute = r; + if (need_absolute) { + done = strdup("/"); + if (!done) + return -ENOMEM; + } + + /* If a positive directory file descriptor is provided, always resolve the given path relative to it, + * regardless of whether it is absolute or not. If we get AT_FDCWD, follow regular openat() + * semantics, if the path is relative, resolve against the current working directory. Otherwise, + * resolve against root. */ + fd = openat(dir_fd, done ?: ".", O_CLOEXEC|O_DIRECTORY|O_PATH); + if (fd < 0) + return -errno; + + if (fstat(fd, &st) < 0) + return -errno; + + /* If we get AT_FDCWD, we always resolve symlinks relative to the host's root. Only if a positive + * directory file descriptor is provided we will look at CHASE_AT_RESOLVE_IN_ROOT to determine + * whether to resolve symlinks in it or not. */ + if (dir_fd >= 0 && FLAGS_SET(flags, CHASE_AT_RESOLVE_IN_ROOT)) + root_fd = openat(dir_fd, ".", O_CLOEXEC|O_DIRECTORY|O_PATH); + else + root_fd = open("/", O_CLOEXEC|O_DIRECTORY|O_PATH); + if (root_fd < 0) + return -errno; + + if (FLAGS_SET(flags, CHASE_TRAIL_SLASH)) + append_trail_slash = ENDSWITH_SET(buffer, "/", "/."); + + for (todo = buffer;;) { + _cleanup_free_ char *first = NULL; + _cleanup_close_ int child = -EBADF; + struct stat st_child; + const char *e; + + r = path_find_first_component(&todo, /* accept_dot_dot= */ true, &e); + if (r < 0) + return r; + if (r == 0) { /* We reached the end. */ + if (append_trail_slash) + if (!strextend(&done, "/")) + return -ENOMEM; + break; + } + + first = strndup(e, r); + if (!first) + return -ENOMEM; + + /* Two dots? Then chop off the last bit of what we already found out. */ + if (path_equal(first, "..")) { + _cleanup_free_ char *parent = NULL; + _cleanup_close_ int fd_parent = -EBADF; + struct stat st_parent; + + /* 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 (empty_or_root(done) && FLAGS_SET(flags, CHASE_AT_RESOLVE_IN_ROOT)) { + if (FLAGS_SET(flags, CHASE_STEP)) + goto chased_one; + continue; + } + + fd_parent = openat(fd, "..", O_CLOEXEC|O_NOFOLLOW|O_PATH|O_DIRECTORY); + if (fd_parent < 0) + return -errno; + + if (fstat(fd_parent, &st_parent) < 0) + return -errno; + + /* If we opened the same directory, that _may_ indicate that we're at the host root + * directory. Let's confirm that in more detail with dir_fd_is_root(). And if so, + * going up won't change anything. */ + if (stat_inode_same(&st_parent, &st)) { + r = dir_fd_is_root(fd); + if (r < 0) + return r; + if (r > 0) { + if (FLAGS_SET(flags, CHASE_STEP)) + goto chased_one; + continue; + } + } + + r = path_extract_directory(done, &parent); + if (r >= 0) { + assert(!need_absolute || path_is_absolute(parent)); + free_and_replace(done, parent); + } else if (r == -EDESTADDRREQ) { + /* 'done' contains filename only (i.e. no slash). */ + assert(!need_absolute); + done = mfree(done); + } else if (r == -EADDRNOTAVAIL) { + /* 'done' is "/". This branch should be already handled in the above. */ + assert(!FLAGS_SET(flags, CHASE_AT_RESOLVE_IN_ROOT)); + assert_not_reached(); + } else if (r == -EINVAL) { + /* 'done' is an empty string, ends with '..', or an invalid path. */ + assert(!need_absolute); + assert(!FLAGS_SET(flags, CHASE_AT_RESOLVE_IN_ROOT)); + + if (!path_is_valid(done)) + return -EINVAL; + + /* If we're at the top of "dir_fd", start appending ".." to "done". */ + if (!path_extend(&done, "..")) + return -ENOMEM; + } else + return r; + + if (FLAGS_SET(flags, CHASE_STEP)) + goto chased_one; + + if (FLAGS_SET(flags, CHASE_SAFE) && + unsafe_transition(&st, &st_parent)) + return log_unsafe_transition(fd, fd_parent, path, flags); + + /* If the path ends on a "..", and CHASE_PARENT is specified then our current 'fd' is + * the child of the returned normalized path, not the parent as requested. To correct + * this we have to go *two* levels up. */ + if (FLAGS_SET(flags, CHASE_PARENT) && isempty(todo)) { + _cleanup_close_ int fd_grandparent = -EBADF; + struct stat st_grandparent; + + fd_grandparent = openat(fd_parent, "..", O_CLOEXEC|O_NOFOLLOW|O_PATH|O_DIRECTORY); + if (fd_grandparent < 0) + return -errno; + + if (fstat(fd_grandparent, &st_grandparent) < 0) + return -errno; + + if (FLAGS_SET(flags, CHASE_SAFE) && + unsafe_transition(&st_parent, &st_grandparent)) + return log_unsafe_transition(fd_parent, fd_grandparent, path, flags); + + st = st_grandparent; + close_and_replace(fd, fd_grandparent); + break; + } + + /* update fd and stat */ + st = st_parent; + close_and_replace(fd, fd_parent); + continue; + } + + /* Otherwise let's see what this is. */ + child = r = RET_NERRNO(openat(fd, first, O_CLOEXEC|O_NOFOLLOW|O_PATH)); + if (r < 0) { + if (r != -ENOENT) + return r; + + if (!isempty(todo) && !path_is_safe(todo)) + return r; + + if (FLAGS_SET(flags, CHASE_MKDIR_0755) && !isempty(todo)) { + child = xopenat(fd, + first, + O_DIRECTORY|O_CREAT|O_EXCL|O_NOFOLLOW|O_CLOEXEC, + /* xopen_flags = */ 0, + 0755); + if (child < 0) + return child; + } else if (FLAGS_SET(flags, CHASE_PARENT) && isempty(todo)) { + if (!path_extend(&done, first)) + return -ENOMEM; + + break; + } else if (FLAGS_SET(flags, CHASE_NONEXISTENT)) { + if (!path_extend(&done, first, todo)) + return -ENOMEM; + + exists = false; + break; + } else + return r; + } + + if (fstat(child, &st_child) < 0) + return -errno; + + if (FLAGS_SET(flags, CHASE_SAFE) && + unsafe_transition(&st, &st_child)) + return log_unsafe_transition(fd, child, path, flags); + + if (FLAGS_SET(flags, CHASE_NO_AUTOFS) && + fd_is_fs_type(child, AUTOFS_SUPER_MAGIC) > 0) + return log_autofs_mount_point(child, path, flags); + + if (S_ISLNK(st_child.st_mode) && !(FLAGS_SET(flags, CHASE_NOFOLLOW) && isempty(todo))) { + _cleanup_free_ char *destination = NULL; + + if (FLAGS_SET(flags, CHASE_PROHIBIT_SYMLINKS)) + return log_prohibited_symlink(child, flags); + + /* 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, &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 file descriptor as base. */ + + safe_close(fd); + fd = fd_reopen(root_fd, O_CLOEXEC|O_PATH|O_DIRECTORY); + if (fd < 0) + return fd; + + if (fstat(fd, &st) < 0) + return -errno; + + if (FLAGS_SET(flags, CHASE_SAFE) && + unsafe_transition(&st_child, &st)) + return log_unsafe_transition(child, fd, path, flags); + + /* When CHASE_AT_RESOLVE_IN_ROOT is not set, now the chased path may be + * outside of the specified dir_fd. Let's make the result absolute. */ + if (!FLAGS_SET(flags, CHASE_AT_RESOLVE_IN_ROOT)) + need_absolute = true; + + r = free_and_strdup(&done, need_absolute ? "/" : NULL); + if (r < 0) + return r; + } + + /* Prefix what's left to do with what we just read, and start the loop again, but + * remain in the current directory. */ + if (!path_extend(&destination, todo)) + return -ENOMEM; + + free_and_replace(buffer, destination); + todo = buffer; + + if (FLAGS_SET(flags, CHASE_STEP)) + goto chased_one; + + continue; + } + + /* If this is not a symlink, then let's just add the name we read to what we already verified. */ + if (!path_extend(&done, first)) + return -ENOMEM; + + if (FLAGS_SET(flags, CHASE_PARENT) && isempty(todo)) + break; + + /* And iterate again, but go one directory further down. */ + st = st_child; + close_and_replace(fd, child); + } + + if (FLAGS_SET(flags, CHASE_PARENT)) { + r = stat_verify_directory(&st); + if (r < 0) + return r; + } + + if (ret_path) { + if (FLAGS_SET(flags, CHASE_EXTRACT_FILENAME) && done) { + _cleanup_free_ char *f = NULL; + + r = path_extract_filename(done, &f); + if (r < 0 && r != -EADDRNOTAVAIL) + return r; + + /* If we get EADDRNOTAVAIL we clear done and it will get reinitialized by the next block. */ + free_and_replace(done, f); + } + + if (!done) { + assert(!need_absolute || FLAGS_SET(flags, CHASE_EXTRACT_FILENAME)); + done = strdup(append_trail_slash ? "./" : "."); + if (!done) + return -ENOMEM; + } + + *ret_path = TAKE_PTR(done); + } + + if (ret_fd) { + /* Return the O_PATH fd we currently are looking to the caller. It can translate it to a + * proper fd by opening /proc/self/fd/xyz. */ + + assert(fd >= 0); + *ret_fd = TAKE_FD(fd); + } + + if (FLAGS_SET(flags, CHASE_STEP)) + return 1; + + return exists; + +chased_one: + if (ret_path) { + const char *e; + + if (!done) { + assert(!need_absolute); + done = strdup(append_trail_slash ? "./" : "."); + if (!done) + return -ENOMEM; + } + + /* todo may contain slashes at the beginning. */ + r = path_find_first_component(&todo, /* accept_dot_dot= */ true, &e); + if (r < 0) + return r; + if (r == 0) + *ret_path = TAKE_PTR(done); + else { + char *c; + + c = path_join(done, e); + if (!c) + return -ENOMEM; + + *ret_path = c; + } + } + + return 0; +} + +static int empty_or_root_to_null(const char **path) { + int r; + + assert(path); + + /* This nullifies the input path when the path is empty or points to "/". */ + + if (empty_or_root(*path)) { + *path = NULL; + return 0; + } + + r = path_is_root(*path); + if (r < 0) + return r; + if (r > 0) + *path = NULL; + + return 0; +} + +int chase(const char *path, const char *root, ChaseFlags flags, char **ret_path, int *ret_fd) { + _cleanup_free_ char *root_abs = NULL, *absolute = NULL, *p = NULL; + _cleanup_close_ int fd = -EBADF, pfd = -EBADF; + int r; + + assert(path); + + if (isempty(path)) + return -EINVAL; + + r = empty_or_root_to_null(&root); + if (r < 0) + return r; + + /* A root directory of "/" or "" is identical to "/". */ + if (empty_or_root(root)) { + root = "/"; + + /* When the root directory is "/", we will drop CHASE_AT_RESOLVE_IN_ROOT in chaseat(), + * hence below is not necessary, but let's shortcut. */ + flags &= ~CHASE_AT_RESOLVE_IN_ROOT; + + } else { + r = path_make_absolute_cwd(root, &root_abs); + if (r < 0) + return r; + + /* Simplify the root directory, so that it has no duplicate slashes and nothing at the + * end. While we won't resolve the root path we still simplify it. */ + root = path_simplify(root_abs); + + assert(path_is_absolute(root)); + assert(!empty_or_root(root)); + + if (FLAGS_SET(flags, CHASE_PREFIX_ROOT)) { + absolute = path_join(root, path); + if (!absolute) + return -ENOMEM; + } + + flags |= CHASE_AT_RESOLVE_IN_ROOT; + } + + if (!absolute) { + r = path_make_absolute_cwd(path, &absolute); + if (r < 0) + return r; + } + + path = path_startswith(absolute, root); + if (!path) + return log_full_errno(FLAGS_SET(flags, CHASE_WARN) ? LOG_WARNING : LOG_DEBUG, + SYNTHETIC_ERRNO(ECHRNG), + "Specified path '%s' is outside of specified root directory '%s', refusing to resolve.", + absolute, root); + + fd = open(root, O_CLOEXEC|O_DIRECTORY|O_PATH); + if (fd < 0) + return -errno; + + r = chaseat(fd, path, flags & ~CHASE_PREFIX_ROOT, ret_path ? &p : NULL, ret_fd ? &pfd : NULL); + if (r < 0) + return r; + + if (ret_path) { + if (!FLAGS_SET(flags, CHASE_EXTRACT_FILENAME)) { + + /* When "root" points to the root directory, the result of chaseat() is always + * absolute, hence it is not necessary to prefix with the root. When "root" points to + * a non-root directory, the result path is always normalized and relative, hence + * we can simply call path_join() and not necessary to call path_simplify(). + * Note that the result of chaseat() may start with "." (more specifically, it may be + * "." or "./"), and we need to drop "." in that case. */ + + if (empty_or_root(root)) + assert(path_is_absolute(p)); + else { + char *q; + + assert(!path_is_absolute(p)); + + q = path_join(root, p + (*p == '.')); + if (!q) + return -ENOMEM; + + free_and_replace(p, q); + } + } + + *ret_path = TAKE_PTR(p); + } + + if (ret_fd) + *ret_fd = TAKE_FD(pfd); + + return r; +} + +int chaseat_prefix_root(const char *path, const char *root, char **ret) { + char *q; + int r; + + assert(path); + assert(ret); + + /* This is mostly for prefixing the result of chaseat(). */ + + if (!path_is_absolute(path)) { + _cleanup_free_ char *root_abs = NULL; + + r = empty_or_root_to_null(&root); + if (r < 0 && r != -ENOENT) + return r; + + /* If the dir_fd points to the root directory, chaseat() always returns an absolute path. */ + if (empty_or_root(root)) + return -EINVAL; + + r = path_make_absolute_cwd(root, &root_abs); + if (r < 0) + return r; + + root = path_simplify(root_abs); + + q = path_join(root, path + (path[0] == '.' && IN_SET(path[1], '/', '\0'))); + } else + q = strdup(path); + if (!q) + return -ENOMEM; + + *ret = q; + return 0; +} + +int chase_extract_filename(const char *path, const char *root, char **ret) { + int r; + + /* This is similar to path_extract_filename(), but takes root directory. + * The result should be consistent with chase() with CHASE_EXTRACT_FILENAME. */ + + assert(path); + assert(ret); + + if (isempty(path)) + return -EINVAL; + + if (!path_is_absolute(path)) + return -EINVAL; + + r = empty_or_root_to_null(&root); + if (r < 0 && r != -ENOENT) + return r; + + if (!empty_or_root(root)) { + _cleanup_free_ char *root_abs = NULL; + + r = path_make_absolute_cwd(root, &root_abs); + if (r < 0) + return r; + + path = path_startswith(path, root_abs); + if (!path) + return -EINVAL; + } + + if (!isempty(path)) { + r = path_extract_filename(path, ret); + if (r != -EADDRNOTAVAIL) + return r; + } + + char *fname = strdup("."); + if (!fname) + return -ENOMEM; + + *ret = fname; + return 0; +} + +int chase_and_open(const char *path, const char *root, ChaseFlags chase_flags, int open_flags, char **ret_path) { + _cleanup_close_ int path_fd = -EBADF; + _cleanup_free_ char *p = NULL, *fname = NULL; + mode_t mode = open_flags & O_DIRECTORY ? 0755 : 0644; + int r; + + assert(!(chase_flags & (CHASE_NONEXISTENT|CHASE_STEP))); + + if (empty_or_root(root) && !ret_path && + (chase_flags & (CHASE_NO_AUTOFS|CHASE_SAFE|CHASE_PROHIBIT_SYMLINKS|CHASE_PARENT|CHASE_MKDIR_0755)) == 0) + /* Shortcut this call if none of the special features of this call are requested */ + return xopenat(AT_FDCWD, path, + open_flags | (FLAGS_SET(chase_flags, CHASE_NOFOLLOW) ? O_NOFOLLOW : 0), + /* xopen_flags = */ 0, + mode); + + r = chase(path, root, CHASE_PARENT|chase_flags, &p, &path_fd); + if (r < 0) + return r; + assert(path_fd >= 0); + + if (!FLAGS_SET(chase_flags, CHASE_PARENT) && + !FLAGS_SET(chase_flags, CHASE_EXTRACT_FILENAME)) { + r = chase_extract_filename(p, root, &fname); + if (r < 0) + return r; + } + + r = xopenat(path_fd, strempty(fname), open_flags|O_NOFOLLOW, /* xopen_flags = */ 0, mode); + if (r < 0) + return r; + + if (ret_path) + *ret_path = TAKE_PTR(p); + + return r; +} + +int chase_and_opendir(const char *path, const char *root, ChaseFlags chase_flags, char **ret_path, DIR **ret_dir) { + _cleanup_close_ int path_fd = -EBADF; + _cleanup_free_ char *p = NULL; + DIR *d; + int r; + + assert(!(chase_flags & (CHASE_NONEXISTENT|CHASE_STEP))); + assert(ret_dir); + + if (empty_or_root(root) && !ret_path && + (chase_flags & (CHASE_NO_AUTOFS|CHASE_SAFE|CHASE_PROHIBIT_SYMLINKS|CHASE_PARENT|CHASE_MKDIR_0755)) == 0) { + /* Shortcut this call if none of the special features of this call are requested */ + d = opendir(path); + if (!d) + return -errno; + + *ret_dir = d; + return 0; + } + + r = chase(path, root, chase_flags, ret_path ? &p : NULL, &path_fd); + if (r < 0) + return r; + assert(path_fd >= 0); + + d = xopendirat(path_fd, ".", O_NOFOLLOW); + if (!d) + return -errno; + + if (ret_path) + *ret_path = TAKE_PTR(p); + + *ret_dir = d; + return 0; +} + +int chase_and_stat(const char *path, const char *root, ChaseFlags chase_flags, char **ret_path, struct stat *ret_stat) { + _cleanup_close_ int path_fd = -EBADF; + _cleanup_free_ char *p = NULL; + int r; + + assert(path); + assert(!(chase_flags & (CHASE_NONEXISTENT|CHASE_STEP))); + assert(ret_stat); + + if (empty_or_root(root) && !ret_path && + (chase_flags & (CHASE_NO_AUTOFS|CHASE_SAFE|CHASE_PROHIBIT_SYMLINKS|CHASE_PARENT|CHASE_MKDIR_0755)) == 0) + /* Shortcut this call if none of the special features of this call are requested */ + return RET_NERRNO(fstatat(AT_FDCWD, path, ret_stat, + FLAGS_SET(chase_flags, CHASE_NOFOLLOW) ? AT_SYMLINK_NOFOLLOW : 0)); + + r = chase(path, root, chase_flags, ret_path ? &p : NULL, &path_fd); + if (r < 0) + return r; + assert(path_fd >= 0); + + if (fstat(path_fd, ret_stat) < 0) + return -errno; + + if (ret_path) + *ret_path = TAKE_PTR(p); + + return 0; +} + +int chase_and_access(const char *path, const char *root, ChaseFlags chase_flags, int access_mode, char **ret_path) { + _cleanup_close_ int path_fd = -EBADF; + _cleanup_free_ char *p = NULL; + int r; + + assert(path); + assert(!(chase_flags & (CHASE_NONEXISTENT|CHASE_STEP))); + + if (empty_or_root(root) && !ret_path && + (chase_flags & (CHASE_NO_AUTOFS|CHASE_SAFE|CHASE_PROHIBIT_SYMLINKS|CHASE_PARENT|CHASE_MKDIR_0755)) == 0) + /* Shortcut this call if none of the special features of this call are requested */ + return RET_NERRNO(faccessat(AT_FDCWD, path, access_mode, + FLAGS_SET(chase_flags, CHASE_NOFOLLOW) ? AT_SYMLINK_NOFOLLOW : 0)); + + r = chase(path, root, chase_flags, ret_path ? &p : NULL, &path_fd); + if (r < 0) + return r; + assert(path_fd >= 0); + + r = access_fd(path_fd, access_mode); + if (r < 0) + return r; + + if (ret_path) + *ret_path = TAKE_PTR(p); + + return 0; +} + +int chase_and_fopen_unlocked( + const char *path, + const char *root, + ChaseFlags chase_flags, + const char *open_flags, + char **ret_path, + FILE **ret_file) { + + _cleanup_free_ char *final_path = NULL; + _cleanup_close_ int fd = -EBADF; + int mode_flags, r; + + assert(path); + assert(!(chase_flags & (CHASE_NONEXISTENT|CHASE_STEP|CHASE_PARENT))); + assert(open_flags); + assert(ret_file); + + mode_flags = fopen_mode_to_flags(open_flags); + if (mode_flags < 0) + return mode_flags; + + fd = chase_and_open(path, root, chase_flags, mode_flags, ret_path ? &final_path : NULL); + if (fd < 0) + return fd; + + r = take_fdopen_unlocked(&fd, open_flags, ret_file); + if (r < 0) + return r; + + if (ret_path) + *ret_path = TAKE_PTR(final_path); + + return 0; +} + +int chase_and_unlink(const char *path, const char *root, ChaseFlags chase_flags, int unlink_flags, char **ret_path) { + _cleanup_free_ char *p = NULL, *fname = NULL; + _cleanup_close_ int fd = -EBADF; + int r; + + assert(path); + assert(!(chase_flags & (CHASE_NONEXISTENT|CHASE_STEP|CHASE_PARENT))); + + fd = chase_and_open(path, root, chase_flags|CHASE_PARENT|CHASE_NOFOLLOW, O_PATH|O_DIRECTORY|O_CLOEXEC, &p); + if (fd < 0) + return fd; + + r = path_extract_filename(p, &fname); + if (r < 0) + return r; + + if (unlinkat(fd, fname, unlink_flags) < 0) + return -errno; + + if (ret_path) + *ret_path = TAKE_PTR(p); + + return 0; +} + +int chase_and_open_parent(const char *path, const char *root, ChaseFlags chase_flags, char **ret_filename) { + int pfd, r; + + assert(!(chase_flags & (CHASE_NONEXISTENT|CHASE_STEP))); + + r = chase(path, root, CHASE_PARENT|CHASE_EXTRACT_FILENAME|chase_flags, ret_filename, &pfd); + if (r < 0) + return r; + + return pfd; +} + +int chase_and_openat(int dir_fd, const char *path, ChaseFlags chase_flags, int open_flags, char **ret_path) { + _cleanup_close_ int path_fd = -EBADF; + _cleanup_free_ char *p = NULL, *fname = NULL; + mode_t mode = open_flags & O_DIRECTORY ? 0755 : 0644; + int r; + + assert(!(chase_flags & (CHASE_NONEXISTENT|CHASE_STEP))); + + if (dir_fd == AT_FDCWD && !ret_path && + (chase_flags & (CHASE_NO_AUTOFS|CHASE_SAFE|CHASE_PROHIBIT_SYMLINKS|CHASE_PARENT|CHASE_MKDIR_0755)) == 0) + /* Shortcut this call if none of the special features of this call are requested */ + return xopenat(dir_fd, path, + open_flags | (FLAGS_SET(chase_flags, CHASE_NOFOLLOW) ? O_NOFOLLOW : 0), + /* xopen_flags = */ 0, + mode); + + r = chaseat(dir_fd, path, chase_flags|CHASE_PARENT, &p, &path_fd); + if (r < 0) + return r; + + if (!FLAGS_SET(chase_flags, CHASE_PARENT)) { + r = path_extract_filename(p, &fname); + if (r < 0 && r != -EADDRNOTAVAIL) + return r; + } + + r = xopenat(path_fd, strempty(fname), open_flags|O_NOFOLLOW, /* xopen_flags = */ 0, mode); + if (r < 0) + return r; + + if (ret_path) + *ret_path = TAKE_PTR(p); + + return r; +} + +int chase_and_opendirat(int dir_fd, const char *path, ChaseFlags chase_flags, char **ret_path, DIR **ret_dir) { + _cleanup_close_ int path_fd = -EBADF; + _cleanup_free_ char *p = NULL; + DIR *d; + int r; + + assert(!(chase_flags & (CHASE_NONEXISTENT|CHASE_STEP))); + assert(ret_dir); + + if (dir_fd == AT_FDCWD && !ret_path && + (chase_flags & (CHASE_NO_AUTOFS|CHASE_SAFE|CHASE_PROHIBIT_SYMLINKS|CHASE_PARENT|CHASE_MKDIR_0755)) == 0) { + /* Shortcut this call if none of the special features of this call are requested */ + d = opendir(path); + if (!d) + return -errno; + + *ret_dir = d; + return 0; + } + + r = chaseat(dir_fd, path, chase_flags, ret_path ? &p : NULL, &path_fd); + if (r < 0) + return r; + assert(path_fd >= 0); + + d = xopendirat(path_fd, ".", O_NOFOLLOW); + if (!d) + return -errno; + + if (ret_path) + *ret_path = TAKE_PTR(p); + + *ret_dir = d; + return 0; +} + +int chase_and_statat(int dir_fd, const char *path, ChaseFlags chase_flags, char **ret_path, struct stat *ret_stat) { + _cleanup_close_ int path_fd = -EBADF; + _cleanup_free_ char *p = NULL; + int r; + + assert(path); + assert(!(chase_flags & (CHASE_NONEXISTENT|CHASE_STEP))); + assert(ret_stat); + + if (dir_fd == AT_FDCWD && !ret_path && + (chase_flags & (CHASE_NO_AUTOFS|CHASE_SAFE|CHASE_PROHIBIT_SYMLINKS|CHASE_PARENT|CHASE_MKDIR_0755)) == 0) + /* Shortcut this call if none of the special features of this call are requested */ + return RET_NERRNO(fstatat(AT_FDCWD, path, ret_stat, + FLAGS_SET(chase_flags, CHASE_NOFOLLOW) ? AT_SYMLINK_NOFOLLOW : 0)); + + r = chaseat(dir_fd, path, chase_flags, ret_path ? &p : NULL, &path_fd); + if (r < 0) + return r; + assert(path_fd >= 0); + + if (fstat(path_fd, ret_stat) < 0) + return -errno; + + if (ret_path) + *ret_path = TAKE_PTR(p); + + return 0; +} + +int chase_and_accessat(int dir_fd, const char *path, ChaseFlags chase_flags, int access_mode, char **ret_path) { + _cleanup_close_ int path_fd = -EBADF; + _cleanup_free_ char *p = NULL; + int r; + + assert(path); + assert(!(chase_flags & (CHASE_NONEXISTENT|CHASE_STEP))); + + if (dir_fd == AT_FDCWD && !ret_path && + (chase_flags & (CHASE_NO_AUTOFS|CHASE_SAFE|CHASE_PROHIBIT_SYMLINKS|CHASE_PARENT|CHASE_MKDIR_0755)) == 0) + /* Shortcut this call if none of the special features of this call are requested */ + return RET_NERRNO(faccessat(AT_FDCWD, path, access_mode, + FLAGS_SET(chase_flags, CHASE_NOFOLLOW) ? AT_SYMLINK_NOFOLLOW : 0)); + + r = chaseat(dir_fd, path, chase_flags, ret_path ? &p : NULL, &path_fd); + if (r < 0) + return r; + assert(path_fd >= 0); + + r = access_fd(path_fd, access_mode); + if (r < 0) + return r; + + if (ret_path) + *ret_path = TAKE_PTR(p); + + return 0; +} + +int chase_and_fopenat_unlocked( + int dir_fd, + const char *path, + ChaseFlags chase_flags, + const char *open_flags, + char **ret_path, + FILE **ret_file) { + + _cleanup_free_ char *final_path = NULL; + _cleanup_close_ int fd = -EBADF; + int mode_flags, r; + + assert(path); + assert(!(chase_flags & (CHASE_NONEXISTENT|CHASE_STEP|CHASE_PARENT))); + assert(open_flags); + assert(ret_file); + + mode_flags = fopen_mode_to_flags(open_flags); + if (mode_flags < 0) + return mode_flags; + + fd = chase_and_openat(dir_fd, path, chase_flags, mode_flags, ret_path ? &final_path : NULL); + if (fd < 0) + return fd; + + r = take_fdopen_unlocked(&fd, open_flags, ret_file); + if (r < 0) + return r; + + if (ret_path) + *ret_path = TAKE_PTR(final_path); + + return 0; +} + +int chase_and_unlinkat(int dir_fd, const char *path, ChaseFlags chase_flags, int unlink_flags, char **ret_path) { + _cleanup_free_ char *p = NULL, *fname = NULL; + _cleanup_close_ int fd = -EBADF; + int r; + + assert(path); + assert(!(chase_flags & (CHASE_NONEXISTENT|CHASE_STEP|CHASE_PARENT))); + + fd = chase_and_openat(dir_fd, path, chase_flags|CHASE_PARENT|CHASE_NOFOLLOW, O_PATH|O_DIRECTORY|O_CLOEXEC, &p); + if (fd < 0) + return fd; + + r = path_extract_filename(p, &fname); + if (r < 0) + return r; + + if (unlinkat(fd, fname, unlink_flags) < 0) + return -errno; + + if (ret_path) + *ret_path = TAKE_PTR(p); + + return 0; +} + +int chase_and_open_parent_at(int dir_fd, const char *path, ChaseFlags chase_flags, char **ret_filename) { + int pfd, r; + + assert(!(chase_flags & (CHASE_NONEXISTENT|CHASE_STEP))); + + r = chaseat(dir_fd, path, CHASE_PARENT|CHASE_EXTRACT_FILENAME|chase_flags, ret_filename, &pfd); + if (r < 0) + return r; + + return pfd; +} |