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Merge pull request #14 from giuseppe/honor-overlay-origin-xattr

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fuse-overlayfs: honor trusted.overlay.origin
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Giuseppe Scrivano 2018-08-07 08:26:53 +02:00 committed by GitHub
commit d40ac752b4
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1 changed files with 72 additions and 14 deletions
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82
main.c
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@ -63,10 +63,12 @@
#define ATTR_TIMEOUT 1000000000.0
#define ENTRY_TIMEOUT 1000000000.0
#define XATTR_PREFIX "user.fuseoverlayfs"
#define XATTR_PREFIX "user.fuseoverlayfs."
#define ORIGIN_XATTR "user.fuseoverlayfs.origin"
#define OPAQUE_XATTR "user.fuseoverlayfs.opaque"
#define PRIVILEGED_XATTR_PREFIX "trusted.overlay."
#define PRIVILEGED_OPAQUE_XATTR "trusted.overlay.opaque"
#define PRIVILEGED_ORIGIN_XATTR "trusted.overlay.origin"
#define NODE_TO_INODE(x) ((fuse_ino_t) x)
@ -153,6 +155,26 @@ static const struct fuse_opt ovl_opts[] = {
FUSE_OPT_END
};
/* Kernel definitions. */
typedef unsigned char u8;
typedef unsigned char uuid_t[16];
/* The type returned by overlay exportfs ops when encoding an ovl_fh handle */
#define OVL_FILEID 0xfb
/* On-disk and in-memeory format for redirect by file handle */
struct ovl_fh
{
u8 version; /* 0 */
u8 magic; /* 0xfb */
u8 len; /* size of this header + size of fid */
u8 flags; /* OVL_FH_FLAG_* */
u8 type; /* fid_type of fid */
uuid_t uuid; /* uuid of filesystem */
u8 fid[0]; /* file identifier */
} __packed;
static struct ovl_data *
ovl_data (fuse_req_t req)
{
@ -743,13 +765,48 @@ make_ovl_node (const char *path, struct ovl_layer *layer, const char *name, ino_
for (it = layer; it; it = it->next)
{
ssize_t s;
int fd = TEMP_FAILURE_RETRY (openat (it->fd, path, O_PATH|O_RDONLY));
int fd = TEMP_FAILURE_RETRY (openat (it->fd, path, O_RDONLY));
if (fd < 0)
continue;
if (fstat (fd, &st) == 0)
ret->ino = st.st_ino;
s = fgetxattr (fd, PRIVILEGED_ORIGIN_XATTR, path, sizeof (path) - 1);
if (s > 0)
{
char buf[512];
struct ovl_fh *ofh = (struct ovl_fh *) path;
size_t s = ofh->len - sizeof (*ofh);
struct file_handle *fh = (struct file_handle *) buf;
if (s < sizeof (buf) - sizeof(int) * 2)
{
int originfd;
/*
overlay in the kernel stores a file handle in the .origin xattr.
Honor it when present, but don't fail on errors as an unprivileged
user cannot open a file handle.
*/
fh->handle_bytes = s;
fh->handle_type = ofh->type;
memcpy (fh->f_handle, ofh->fid, s);
originfd = open_by_handle_at (AT_FDCWD, fh, O_RDONLY);
if (originfd >= 0)
{
if (fstat (originfd, &st) == 0)
{
ret->ino = st.st_ino;
close (originfd);
close (fd);
break;
}
}
}
}
/* If an origin is specified, use it for the next layer lookup. */
s = fgetxattr (fd, ORIGIN_XATTR, path, sizeof (path) - 1);
if (s > 0)
@ -888,7 +945,6 @@ load_dir (struct ovl_data *lo, struct ovl_node *n, struct ovl_layer *layer, char
{
if (it->low)
child->present_lowerdir = 1;
child->ino = st.st_ino;
continue;
}
}
@ -998,11 +1054,9 @@ read_dirs (char *path, bool low, struct ovl_layer *layers)
l->low = low;
if (low)
{
if (last == NULL)
{
last = layers = l;
l->next = NULL;
}
if (last == NULL)
last = layers = l;
else
{
last->next = l;
@ -1404,7 +1458,6 @@ ovl_do_readdir (fuse_req_t req, fuse_ino_t ino, size_t size,
memcpy (&e.attr, &st, sizeof (st));
entsize = fuse_add_direntry_plus (req, p, remaining, name, &e, offset + 1);
if (entsize <= remaining)
{
/* First two entries are . and .. */
@ -2081,7 +2134,7 @@ ovl_setxattr (fuse_req_t req, fuse_ino_t ino, const char *name,
fprintf (stderr, "ovl_setxattr(ino=%" PRIu64 "s, name=%s, value=%s, size=%zu, flags=%d)\n", ino, name,
value, size, flags);
if (has_prefix (name, XATTR_PREFIX))
if (has_prefix (name, PRIVILEGED_XATTR_PREFIX) || has_prefix (name, XATTR_PREFIX))
{
fuse_reply_err (req, EPERM);
return;
@ -2602,11 +2655,16 @@ ovl_link (fuse_req_t req, fuse_ino_t ino, fuse_ino_t newparent, const char *newn
if (sfd >= 0)
{
char origin_path[PATH_MAX + 10];
ssize_t s = fgetxattr (sfd, ORIGIN_XATTR, origin_path, sizeof (origin_path));
size_t s;
s = fgetxattr (sfd, PRIVILEGED_ORIGIN_XATTR, origin_path, sizeof (origin_path));
if (s > 0)
fsetxattr (dfd, PRIVILEGED_ORIGIN_XATTR, origin_path, s, 0);
s = fgetxattr (sfd, ORIGIN_XATTR, origin_path, sizeof (origin_path));
if (s > 0)
{
set = fsetxattr (dfd, ORIGIN_XATTR, origin_path, s, 0) == 0;
}
close (sfd);
}