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cmd/mount: add all-squash option to squash all users #4144

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cmd/mount: add all-squash option to squash all users #4144

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c2161e3
cmd/mount: add `all-squash` option to squash all users
SandyXSD Nov 7, 2023
749ddba
disable 'default_permissions' when all-squash enabled
SandyXSD Nov 7, 2023
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23 changes: 19 additions & 4 deletions cmd/mount_unix.go
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Original file line number Diff line number Diff line change
Expand Up @@ -141,6 +141,10 @@ func fuseFlags() []cli.Flag {
Name: "root-squash",
Usage: "mapping local root user (uid = 0) to another one specified as <uid>:<gid>",
},
&cli.StringFlag{
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@Hexilee Hexilee Nov 7, 2023 •
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We should make flag non-default-permission visible or enable it by default when squash all users. Otherwise, the kernel may deny users to modify files they created.

$ touch hello
touch: setting times of 'hello': Permission denied

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We probably have to always disable default permission to make the all-squash work

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No, there will be lots of access() and much slower.

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But all-squash can hardly work with default-permission.

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When defaultPermission is disabled, we should make sure that the permission is checked in all the places, or access is called for them.

Name: "all-squash",
Usage: "mapping all local users to another one specified as <uid>:<gid>",
},
&cli.BoolFlag{
Name: "prefix-internal",
Usage: "add '.jfs' prefix to all internal files",
Expand Down Expand Up @@ -243,8 +247,16 @@ func mount_main(v *vfs.VFS, c *cli.Context) {
conf.EntryTimeout = time.Millisecond * time.Duration(c.Float64("entry-cache")*1000)
conf.DirEntryTimeout = time.Millisecond * time.Duration(c.Float64("dir-entry-cache")*1000)
conf.NonDefaultPermission = c.Bool("non-default-permission")
rootSquash := c.String("root-squash")
if rootSquash != "" {
squash := c.String("root-squash")
rootOnly := squash != ""
if allSquash := c.String("all-squash"); allSquash != "" {
if rootOnly {
rootOnly = false
logger.Warnf("'root-squash' is ignored since 'all-squash' is specified")
}
squash = allSquash
}
if squash != "" {
var uid, gid uint32 = 65534, 65534
if u, err := user.Lookup("nobody"); err == nil {
nobody, err := strconv.ParseUint(u.Uid, 10, 32)
Expand All @@ -261,7 +273,7 @@ func mount_main(v *vfs.VFS, c *cli.Context) {
gid = uint32(nogroup)
}

ss := strings.SplitN(strings.TrimSpace(rootSquash), ":", 2)
ss := strings.SplitN(strings.TrimSpace(squash), ":", 2)
if ss[0] != "" {
u, err := strconv.ParseUint(ss[0], 10, 32)
if err != nil {
Expand All @@ -276,7 +288,10 @@ func mount_main(v *vfs.VFS, c *cli.Context) {
}
gid = uint32(g)
}
conf.RootSquash = &vfs.RootSquash{Uid: uid, Gid: gid}
if !rootOnly && (uid == 0 || gid == 0) {
logger.Fatalf("cannot squash uid/gid to 0")
}
conf.UserSquash = &vfs.UserSquash{Uid: uid, Gid: gid, RootOnly: rootOnly}
}
logger.Infof("Mounting volume %s at %s ...", conf.Format.Name, conf.Meta.MountPoint)
err := fuse.Serve(v, c.String("o"), c.Bool("enable-xattr"), c.Bool("enable-ioctl"))
Expand Down
6 changes: 3 additions & 3 deletions pkg/fuse/context.go
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Expand Up @@ -63,10 +63,10 @@ func (fs *fileSystem) newContext(cancel <-chan struct{}, header *fuse.InHeader)
ctx.cancel = cancel
ctx.header = header
ctx.checkPermission = fs.conf.NonDefaultPermission && header.Uid != 0
if header.Uid == 0 && fs.conf.RootSquash != nil {
if fs.conf.UserSquash != nil && (header.Uid == 0 || !fs.conf.UserSquash.RootOnly) {
ctx.checkPermission = true
ctx.header.Uid = fs.conf.RootSquash.Uid
ctx.header.Gid = fs.conf.RootSquash.Gid
ctx.header.Uid = fs.conf.UserSquash.Uid
ctx.header.Gid = fs.conf.UserSquash.Gid
}
return ctx
}
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9 changes: 5 additions & 4 deletions pkg/vfs/vfs.go
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Expand Up @@ -62,13 +62,14 @@ type Config struct {
AccessLog string `json:",omitempty"`
PrefixInternal bool
HideInternal bool
RootSquash *RootSquash `json:",omitempty"`
UserSquash *UserSquash `json:",omitempty"`
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Will it break anything (loading a JSON)?

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Usually it's dynamically loaded

NonDefaultPermission bool `json:",omitempty"`
}

type RootSquash struct {
Uid uint32
Gid uint32
type UserSquash struct {
Uid uint32
Gid uint32
RootOnly bool
}

var (
Expand Down