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chase: introduce flags that verify that chased inode is regular file or dir

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This also implies the new CHASE_MUST_BE_DIRECTORY flag in case the
specified path ends in a slash. This makes the rules stricter, it means
we'll be closer to how this is handled in kernel: if a path ends in a
slash it can never refer to a non-directory.
This commit is contained in:
Lennart Poettering
2025-01-20 11:35:03 +01:00
parent 64d52739c5
commit 90b9f7a07e
3 changed files with 26 additions and 10 deletions
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src/basic/chase.c
+17 -3
View File
@@ -89,6 +89,7 @@ int chaseat(int dir_fd, const char *path, ChaseFlags flags, char **ret_path, int
int r;
assert(!FLAGS_SET(flags, CHASE_PREFIX_ROOT));
assert(!FLAGS_SET(flags, CHASE_MUST_BE_DIRECTORY|CHASE_MUST_BE_REGULAR));
assert(!FLAGS_SET(flags, CHASE_STEP|CHASE_EXTRACT_FILENAME));
assert(!FLAGS_SET(flags, CHASE_TRAIL_SLASH|CHASE_EXTRACT_FILENAME));
assert(dir_fd >= 0 || dir_fd == AT_FDCWD);
@@ -243,8 +244,15 @@ int chaseat(int dir_fd, const char *path, ChaseFlags flags, char **ret_path, int
if (root_fd < 0)
return -errno;
if (FLAGS_SET(flags, CHASE_TRAIL_SLASH))
append_trail_slash = ENDSWITH_SET(buffer, "/", "/.");
if (ENDSWITH_SET(buffer, "/", "/.")) {
flags |= CHASE_MUST_BE_DIRECTORY;
if (FLAGS_SET(flags, CHASE_TRAIL_SLASH))
append_trail_slash = true;
} else if (dot_or_dot_dot(buffer) || endswith(buffer, "/.."))
flags |= CHASE_MUST_BE_DIRECTORY;
if (FLAGS_SET(flags, CHASE_PARENT))
flags |= CHASE_MUST_BE_DIRECTORY;
for (todo = buffer;;) {
_cleanup_free_ char *first = NULL;
@@ -476,12 +484,18 @@ int chaseat(int dir_fd, const char *path, ChaseFlags flags, char **ret_path, int
close_and_replace(fd, child);
}
if (FLAGS_SET(flags, CHASE_PARENT)) {
if (FLAGS_SET(flags, CHASE_MUST_BE_DIRECTORY)) {
r = stat_verify_directory(&st);
if (r < 0)
return r;
}
if (FLAGS_SET(flags, CHASE_MUST_BE_REGULAR)) {
r = stat_verify_regular(&st);
if (r < 0)
return r;
}
if (ret_path) {
if (FLAGS_SET(flags, CHASE_EXTRACT_FILENAME) && done) {
_cleanup_free_ char *f = NULL;
src/basic/chase.h
+2
View File
@@ -29,6 +29,8 @@ typedef enum ChaseFlags {
* file points to the last path component does not exist. */
CHASE_MKDIR_0755 = 1 << 11, /* Create any missing directories in the given path. */
CHASE_EXTRACT_FILENAME = 1 << 12, /* Only return the last component of the resolved path */
CHASE_MUST_BE_DIRECTORY = 1 << 13, /* Fail if returned inode fd is not a dir */
CHASE_MUST_BE_REGULAR = 1 << 14, /* Fail if returned inode fd is not a regular file */
} ChaseFlags;
bool unsafe_transition(const struct stat *a, const struct stat *b);
src/shared/machine-id-setup.c
+7 -7
View File
@@ -74,7 +74,7 @@ static int acquire_machine_id(const char *root, bool machine_id_from_firmware, s
}
/* Then, try reading the D-Bus machine ID, unless it is a symlink */
fd = chase_and_open("/var/lib/dbus/machine-id", root, CHASE_PREFIX_ROOT | CHASE_NOFOLLOW, O_RDONLY|O_CLOEXEC|O_NOCTTY, NULL);
fd = chase_and_open("/var/lib/dbus/machine-id", root, CHASE_PREFIX_ROOT|CHASE_NOFOLLOW|CHASE_MUST_BE_REGULAR, O_RDONLY|O_CLOEXEC|O_NOCTTY, NULL);
if (fd >= 0 && id128_read_fd(fd, ID128_FORMAT_PLAIN | ID128_REFUSE_NULL, ret) >= 0) {
log_info("Initializing machine ID from D-Bus machine ID.");
return 0;
@@ -140,12 +140,12 @@ int machine_id_setup(const char *root, sd_id128_t machine_id, MachineIdSetupFlag
WITH_UMASK(0000) {
_cleanup_close_ int inode_fd = -EBADF;
r = chase("/etc/machine-id", root, CHASE_PREFIX_ROOT, &etc_machine_id, &inode_fd);
r = chase("/etc/machine-id", root, CHASE_PREFIX_ROOT|CHASE_MUST_BE_REGULAR, &etc_machine_id, &inode_fd);
if (r == -ENOENT) {
_cleanup_close_ int etc_fd = -EBADF;
_cleanup_free_ char *etc = NULL;
r = chase("/etc/", root, CHASE_PREFIX_ROOT|CHASE_MKDIR_0755, &etc, &etc_fd);
r = chase("/etc/", root, CHASE_PREFIX_ROOT|CHASE_MKDIR_0755|CHASE_MUST_BE_DIRECTORY, &etc, &etc_fd);
if (r < 0)
return log_error_errno(r, "Failed to open '/etc/': %m");
@@ -250,7 +250,7 @@ int machine_id_setup(const char *root, sd_id128_t machine_id, MachineIdSetupFlag
if (write_run_machine_id) {
_cleanup_free_ char *run = NULL;
r = chase("/run/", root, CHASE_PREFIX_ROOT|CHASE_MKDIR_0755, &run, &run_fd);
r = chase("/run/", root, CHASE_PREFIX_ROOT|CHASE_MKDIR_0755|CHASE_MUST_BE_DIRECTORY, &run, &run_fd);
if (r < 0)
return log_error_errno(r, "Failed to open '/run/': %m");
@@ -266,7 +266,7 @@ int machine_id_setup(const char *root, sd_id128_t machine_id, MachineIdSetupFlag
unlink_run_machine_id = true;
} else {
r = chase("/run/machine-id", root, CHASE_PREFIX_ROOT, &run_machine_id, /* ret_inode_fd= */ NULL);
r = chase("/run/machine-id", root, CHASE_PREFIX_ROOT|CHASE_MUST_BE_REGULAR, &run_machine_id, /* ret_inode_fd= */ NULL);
if (r < 0)
return log_error_errno(r, "Failed to open '/run/machine-id': %m");
}
@@ -321,7 +321,7 @@ int machine_id_commit(const char *root) {
_cleanup_close_ int etc_fd = -EBADF;
_cleanup_free_ char *etc = NULL;
r = chase("/etc/", root, CHASE_PREFIX_ROOT, &etc, &etc_fd);
r = chase("/etc/", root, CHASE_PREFIX_ROOT|CHASE_MUST_BE_DIRECTORY, &etc, &etc_fd);
if (r < 0)
return log_error_errno(r, "Failed to open /etc/: %m");
@@ -369,7 +369,7 @@ int machine_id_commit(const char *root) {
/* Open /etc/ again after we transitioned into our own private mount namespace */
_cleanup_close_ int etc_fd_again = -EBADF;
r = chase("/etc/", root, CHASE_PREFIX_ROOT, /* ret_path= */ NULL, &etc_fd_again);
r = chase("/etc/", root, CHASE_PREFIX_ROOT|CHASE_MUST_BE_DIRECTORY, /* ret_path= */ NULL, &etc_fd_again);
if (r < 0)
return log_error_errno(r, "Failed to open /etc/: %m");