| /* SPDX-License-Identifier: LGPL-2.1+ */ |
| |
| #include <fcntl.h> |
| #include <linux/magic.h> |
| #if HAVE_ACL |
| #include <sys/acl.h> |
| #endif |
| #include <sys/stat.h> |
| #include <sys/statvfs.h> |
| #include <sys/vfs.h> |
| #include <unistd.h> |
| |
| #include "acl-util.h" |
| #include "dirent-util.h" |
| #include "fd-util.h" |
| #include "fs-util.h" |
| #include "missing.h" |
| #include "nspawn-def.h" |
| #include "nspawn-patch-uid.h" |
| #include "stat-util.h" |
| #include "stdio-util.h" |
| #include "string-util.h" |
| #include "strv.h" |
| #include "user-util.h" |
| |
| #if HAVE_ACL |
| |
| static int get_acl(int fd, const char *name, acl_type_t type, acl_t *ret) { |
| char procfs_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int) + 1]; |
| acl_t acl; |
| |
| assert(fd >= 0); |
| assert(ret); |
| |
| if (name) { |
| _cleanup_close_ int child_fd = -1; |
| |
| child_fd = openat(fd, name, O_PATH|O_CLOEXEC|O_NOFOLLOW); |
| if (child_fd < 0) |
| return -errno; |
| |
| xsprintf(procfs_path, "/proc/self/fd/%i", child_fd); |
| acl = acl_get_file(procfs_path, type); |
| } else if (type == ACL_TYPE_ACCESS) |
| acl = acl_get_fd(fd); |
| else { |
| xsprintf(procfs_path, "/proc/self/fd/%i", fd); |
| acl = acl_get_file(procfs_path, type); |
| } |
| if (!acl) |
| return -errno; |
| |
| *ret = acl; |
| return 0; |
| } |
| |
| static int set_acl(int fd, const char *name, acl_type_t type, acl_t acl) { |
| char procfs_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int) + 1]; |
| int r; |
| |
| assert(fd >= 0); |
| assert(acl); |
| |
| if (name) { |
| _cleanup_close_ int child_fd = -1; |
| |
| child_fd = openat(fd, name, O_PATH|O_CLOEXEC|O_NOFOLLOW); |
| if (child_fd < 0) |
| return -errno; |
| |
| xsprintf(procfs_path, "/proc/self/fd/%i", child_fd); |
| r = acl_set_file(procfs_path, type, acl); |
| } else if (type == ACL_TYPE_ACCESS) |
| r = acl_set_fd(fd, acl); |
| else { |
| xsprintf(procfs_path, "/proc/self/fd/%i", fd); |
| r = acl_set_file(procfs_path, type, acl); |
| } |
| if (r < 0) |
| return -errno; |
| |
| return 0; |
| } |
| |
| static int shift_acl(acl_t acl, uid_t shift, acl_t *ret) { |
| _cleanup_(acl_freep) acl_t copy = NULL; |
| acl_entry_t i; |
| int r; |
| |
| assert(acl); |
| assert(ret); |
| |
| r = acl_get_entry(acl, ACL_FIRST_ENTRY, &i); |
| if (r < 0) |
| return -errno; |
| while (r > 0) { |
| uid_t *old_uid, new_uid; |
| bool modify = false; |
| acl_tag_t tag; |
| |
| if (acl_get_tag_type(i, &tag) < 0) |
| return -errno; |
| |
| if (IN_SET(tag, ACL_USER, ACL_GROUP)) { |
| |
| /* We don't distuingish here between uid_t and gid_t, let's make sure the compiler checks that |
| * this is actually OK */ |
| assert_cc(sizeof(uid_t) == sizeof(gid_t)); |
| |
| old_uid = acl_get_qualifier(i); |
| if (!old_uid) |
| return -errno; |
| |
| new_uid = shift | (*old_uid & UINT32_C(0xFFFF)); |
| if (!uid_is_valid(new_uid)) |
| return -EINVAL; |
| |
| modify = new_uid != *old_uid; |
| if (modify && !copy) { |
| int n; |
| |
| /* There's no copy of the ACL yet? if so, let's create one, and start the loop from the |
| * beginning, so that we copy all entries, starting from the first, this time. */ |
| |
| n = acl_entries(acl); |
| if (n < 0) |
| return -errno; |
| |
| copy = acl_init(n); |
| if (!copy) |
| return -errno; |
| |
| /* Seek back to the beginning */ |
| r = acl_get_entry(acl, ACL_FIRST_ENTRY, &i); |
| if (r < 0) |
| return -errno; |
| continue; |
| } |
| } |
| |
| if (copy) { |
| acl_entry_t new_entry; |
| |
| if (acl_create_entry(©, &new_entry) < 0) |
| return -errno; |
| |
| if (acl_copy_entry(new_entry, i) < 0) |
| return -errno; |
| |
| if (modify) |
| if (acl_set_qualifier(new_entry, &new_uid) < 0) |
| return -errno; |
| } |
| |
| r = acl_get_entry(acl, ACL_NEXT_ENTRY, &i); |
| if (r < 0) |
| return -errno; |
| } |
| |
| *ret = TAKE_PTR(copy); |
| |
| return !!*ret; |
| } |
| |
| static int patch_acls(int fd, const char *name, const struct stat *st, uid_t shift) { |
| _cleanup_(acl_freep) acl_t acl = NULL, shifted = NULL; |
| bool changed = false; |
| int r; |
| |
| assert(fd >= 0); |
| assert(st); |
| |
| /* ACLs are not supported on symlinks, there's no point in trying */ |
| if (S_ISLNK(st->st_mode)) |
| return 0; |
| |
| r = get_acl(fd, name, ACL_TYPE_ACCESS, &acl); |
| if (r == -EOPNOTSUPP) |
| return 0; |
| if (r < 0) |
| return r; |
| |
| r = shift_acl(acl, shift, &shifted); |
| if (r < 0) |
| return r; |
| if (r > 0) { |
| r = set_acl(fd, name, ACL_TYPE_ACCESS, shifted); |
| if (r < 0) |
| return r; |
| |
| changed = true; |
| } |
| |
| if (S_ISDIR(st->st_mode)) { |
| acl_free(acl); |
| acl_free(shifted); |
| |
| acl = shifted = NULL; |
| |
| r = get_acl(fd, name, ACL_TYPE_DEFAULT, &acl); |
| if (r < 0) |
| return r; |
| |
| r = shift_acl(acl, shift, &shifted); |
| if (r < 0) |
| return r; |
| if (r > 0) { |
| r = set_acl(fd, name, ACL_TYPE_DEFAULT, shifted); |
| if (r < 0) |
| return r; |
| |
| changed = true; |
| } |
| } |
| |
| return changed; |
| } |
| |
| #else |
| |
| static int patch_acls(int fd, const char *name, const struct stat *st, uid_t shift) { |
| return 0; |
| } |
| |
| #endif |
| |
| static int patch_fd(int fd, const char *name, const struct stat *st, uid_t shift) { |
| uid_t new_uid; |
| gid_t new_gid; |
| bool changed = false; |
| int r; |
| |
| assert(fd >= 0); |
| assert(st); |
| |
| new_uid = shift | (st->st_uid & UINT32_C(0xFFFF)); |
| new_gid = (gid_t) shift | (st->st_gid & UINT32_C(0xFFFF)); |
| |
| if (!uid_is_valid(new_uid) || !gid_is_valid(new_gid)) |
| return -EINVAL; |
| |
| if (st->st_uid != new_uid || st->st_gid != new_gid) { |
| if (name) |
| r = fchownat(fd, name, new_uid, new_gid, AT_SYMLINK_NOFOLLOW); |
| else |
| r = fchown(fd, new_uid, new_gid); |
| if (r < 0) |
| return -errno; |
| |
| /* The Linux kernel alters the mode in some cases of chown(). Let's undo this. */ |
| if (name) { |
| if (!S_ISLNK(st->st_mode)) |
| r = fchmodat(fd, name, st->st_mode, 0); |
| else /* AT_SYMLINK_NOFOLLOW is not available for fchmodat() */ |
| r = 0; |
| } else |
| r = fchmod(fd, st->st_mode); |
| if (r < 0) |
| return -errno; |
| |
| changed = true; |
| } |
| |
| r = patch_acls(fd, name, st, shift); |
| if (r < 0) |
| return r; |
| |
| return r > 0 || changed; |
| } |
| |
| /* |
| * Check if the filesystem is fully compatible with user namespaces or |
| * UID/GID patching. Some filesystems in this list can be fully mounted inside |
| * user namespaces, however their inodes may relate to host resources or only |
| * valid in the global user namespace, therefore no patching should be applied. |
| */ |
| static int is_fs_fully_userns_compatible(const struct statfs *sfs) { |
| |
| assert(sfs); |
| |
| return F_TYPE_EQUAL(sfs->f_type, BINFMTFS_MAGIC) || |
| F_TYPE_EQUAL(sfs->f_type, CGROUP_SUPER_MAGIC) || |
| F_TYPE_EQUAL(sfs->f_type, CGROUP2_SUPER_MAGIC) || |
| F_TYPE_EQUAL(sfs->f_type, DEBUGFS_MAGIC) || |
| F_TYPE_EQUAL(sfs->f_type, DEVPTS_SUPER_MAGIC) || |
| F_TYPE_EQUAL(sfs->f_type, EFIVARFS_MAGIC) || |
| F_TYPE_EQUAL(sfs->f_type, HUGETLBFS_MAGIC) || |
| F_TYPE_EQUAL(sfs->f_type, MQUEUE_MAGIC) || |
| F_TYPE_EQUAL(sfs->f_type, PROC_SUPER_MAGIC) || |
| F_TYPE_EQUAL(sfs->f_type, PSTOREFS_MAGIC) || |
| F_TYPE_EQUAL(sfs->f_type, SELINUX_MAGIC) || |
| F_TYPE_EQUAL(sfs->f_type, SMACK_MAGIC) || |
| F_TYPE_EQUAL(sfs->f_type, SECURITYFS_MAGIC) || |
| F_TYPE_EQUAL(sfs->f_type, BPF_FS_MAGIC) || |
| F_TYPE_EQUAL(sfs->f_type, TRACEFS_MAGIC) || |
| F_TYPE_EQUAL(sfs->f_type, SYSFS_MAGIC); |
| } |
| |
| static int recurse_fd(int fd, bool donate_fd, const struct stat *st, uid_t shift, bool is_toplevel) { |
| _cleanup_closedir_ DIR *d = NULL; |
| bool changed = false; |
| struct statfs sfs; |
| int r; |
| |
| assert(fd >= 0); |
| |
| if (fstatfs(fd, &sfs) < 0) |
| return -errno; |
| |
| /* We generally want to permit crossing of mount boundaries when patching the UIDs/GIDs. However, we probably |
| * shouldn't do this for /proc and /sys if that is already mounted into place. Hence, let's stop the recursion |
| * when we hit procfs, sysfs or some other special file systems. */ |
| |
| r = is_fs_fully_userns_compatible(&sfs); |
| if (r < 0) |
| goto finish; |
| if (r > 0) { |
| r = 0; /* don't recurse */ |
| goto finish; |
| } |
| |
| /* Also, if we hit a read-only file system, then don't bother, skip the whole subtree */ |
| if ((sfs.f_flags & ST_RDONLY) || |
| access_fd(fd, W_OK) == -EROFS) |
| goto read_only; |
| |
| if (S_ISDIR(st->st_mode)) { |
| struct dirent *de; |
| |
| if (!donate_fd) { |
| int copy; |
| |
| copy = fcntl(fd, F_DUPFD_CLOEXEC, 3); |
| if (copy < 0) { |
| r = -errno; |
| goto finish; |
| } |
| |
| fd = copy; |
| donate_fd = true; |
| } |
| |
| d = fdopendir(fd); |
| if (!d) { |
| r = -errno; |
| goto finish; |
| } |
| fd = -1; |
| |
| FOREACH_DIRENT_ALL(de, d, r = -errno; goto finish) { |
| struct stat fst; |
| |
| if (dot_or_dot_dot(de->d_name)) |
| continue; |
| |
| if (fstatat(dirfd(d), de->d_name, &fst, AT_SYMLINK_NOFOLLOW) < 0) { |
| r = -errno; |
| goto finish; |
| } |
| |
| if (S_ISDIR(fst.st_mode)) { |
| int subdir_fd; |
| |
| subdir_fd = openat(dirfd(d), de->d_name, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW|O_NOATIME); |
| if (subdir_fd < 0) { |
| r = -errno; |
| goto finish; |
| |
| } |
| |
| r = recurse_fd(subdir_fd, true, &fst, shift, false); |
| if (r < 0) |
| goto finish; |
| if (r > 0) |
| changed = true; |
| |
| } else { |
| r = patch_fd(dirfd(d), de->d_name, &fst, shift); |
| if (r < 0) |
| goto finish; |
| if (r > 0) |
| changed = true; |
| } |
| } |
| } |
| |
| /* After we descended, also patch the directory itself. It's key to do this in this order so that the top-level |
| * directory is patched as very last object in the tree, so that we can use it as quick indicator whether the |
| * tree is properly chown()ed already. */ |
| r = patch_fd(d ? dirfd(d) : fd, NULL, st, shift); |
| if (r == -EROFS) |
| goto read_only; |
| if (r > 0) |
| changed = true; |
| |
| r = changed; |
| goto finish; |
| |
| read_only: |
| if (!is_toplevel) { |
| _cleanup_free_ char *name = NULL; |
| |
| /* When we hit a ready-only subtree we simply skip it, but log about it. */ |
| (void) fd_get_path(fd, &name); |
| log_debug("Skipping read-only file or directory %s.", strna(name)); |
| r = changed; |
| } |
| |
| finish: |
| if (donate_fd) |
| safe_close(fd); |
| |
| return r; |
| } |
| |
| static int fd_patch_uid_internal(int fd, bool donate_fd, uid_t shift, uid_t range) { |
| struct stat st; |
| int r; |
| |
| assert(fd >= 0); |
| |
| /* Recursively adjusts the UID/GIDs of all files of a directory tree. This is used to automatically fix up an |
| * OS tree to the used user namespace UID range. Note that this automatic adjustment only works for UID ranges |
| * following the concept that the upper 16bit of a UID identify the container, and the lower 16bit are the actual |
| * UID within the container. */ |
| |
| if ((shift & 0xFFFF) != 0) { |
| /* We only support containers where the shift starts at a 2^16 boundary */ |
| r = -EOPNOTSUPP; |
| goto finish; |
| } |
| |
| if (shift == UID_BUSY_BASE) { |
| r = -EINVAL; |
| goto finish; |
| } |
| |
| if (range != 0x10000) { |
| /* We only support containers with 16bit UID ranges for the patching logic */ |
| r = -EOPNOTSUPP; |
| goto finish; |
| } |
| |
| if (fstat(fd, &st) < 0) { |
| r = -errno; |
| goto finish; |
| } |
| |
| if ((uint32_t) st.st_uid >> 16 != (uint32_t) st.st_gid >> 16) { |
| /* We only support containers where the uid/gid container ID match */ |
| r = -EBADE; |
| goto finish; |
| } |
| |
| /* Try to detect if the range is already right. Of course, this a pretty drastic optimization, as we assume |
| * that if the top-level dir has the right upper 16bit assigned, then everything below will have too... */ |
| if (((uint32_t) (st.st_uid ^ shift) >> 16) == 0) |
| return 0; |
| |
| /* Before we start recursively chowning, mark the top-level dir as "busy" by chowning it to the "busy" |
| * range. Should we be interrupted in the middle of our work, we'll see it owned by this user and will start |
| * chown()ing it again, unconditionally, as the busy UID is not a valid UID we'd everpick for ourselves. */ |
| |
| if ((st.st_uid & UID_BUSY_MASK) != UID_BUSY_BASE) { |
| if (fchown(fd, |
| UID_BUSY_BASE | (st.st_uid & ~UID_BUSY_MASK), |
| (gid_t) UID_BUSY_BASE | (st.st_gid & ~(gid_t) UID_BUSY_MASK)) < 0) { |
| r = -errno; |
| goto finish; |
| } |
| } |
| |
| return recurse_fd(fd, donate_fd, &st, shift, true); |
| |
| finish: |
| if (donate_fd) |
| safe_close(fd); |
| |
| return r; |
| } |
| |
| int path_patch_uid(const char *path, uid_t shift, uid_t range) { |
| int fd; |
| |
| fd = open(path, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW|O_NOATIME); |
| if (fd < 0) |
| return -errno; |
| |
| return fd_patch_uid_internal(fd, true, shift, range); |
| } |