Adding upstream version 241.upstream/241upstream

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

1 files changed, 490 insertions, 0 deletions

diff --git a/src/nspawn/nspawn-patch-uid.c b/src/nspawn/nspawn-patch-uid.c
new file mode 100644
index 0000000..db2f546
--- /dev/null
+++ b/src/nspawn/nspawn-patch-uid.c
@@ -0,0 +1,490 @@
+/* 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(&copy, &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("Skippping 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);
+}