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authormudcam <v.nieutin@live.fr>2017-12-07 10:31:22 +0100
committerronan [iot.bzh] <ronan.lemartret@iot.bzh>2017-12-07 12:52:16 +0100
commit981e9b9c4a40e248733d45cfedc6a512bdf95f5e (patch)
tree12526631368064d80c832d6bbf78b20af85c50f7 /security-blueprint/part-4/5-FileSystems.md
parentbc11e3eaceb629fbf5dee7ed7bfdf696839ddb12 (diff)
Add proposal for new security blueprint
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+# File System
+
+## Disable all file systems not needed
+
+To reduce the attack surface, file system data is parsed by the kernel, so any logic bugs in file system drivers can become kernel exploits.
+
+### Disable NFS file system
+
+NFS FileSystems are useful during development phases, but this can be a very helpful way for an attacker to get files when you are in production mode, so we must disable them.
+
+<!-- config -->
+
+Domain | `Config` name | `Value`
+------------------------ | --------------- | -------
+Kernel-FileSystems-NFS-1 | `CONFIG_NFSD` | `n`
+Kernel-FileSystems-NFS-2 | `CONFIG_NFS_FS` | `n`
+
+<!-- endconfig -->
+
+--------------------------------------------------------------------------------
+
+<!-- pagebreak -->
+
+## Partition Mount Options
+
+There are several security restrictions that can be set on a filesystem when it is mounted. Some common security options include, but are not limited to:
+
+`nosuid` - Do not allow set-user-identifier or set-group-identifier bits to take effect.
+
+`nodev` - Do not interpret character or block special devices on the filesystem.
+
+`noexec` - Do not allow execution of any binaries on the mounted filesystem.
+
+`ro` - Mount filesystem as read-only.
+
+The following flags shall be used for mounting common filesystems:
+
+<!-- config -->
+
+Domain | `Partition` | `Value`
+-------------------------- | ------------------- | -----------------------------------------------------------------
+Kernel-FileSystems-Mount-1 | `/boot` | `nosuid`, `nodev` and `noexec`.
+Kernel-FileSystems-Mount-2 | `/var` & `/tmp` | In `/etc/fstab` or `vfstab`, add `nosuid`, `nodev` and `noexec`.
+Kernel-FileSystems-Mount-3 | _Non-root local_ | If type is `ext2` or `ext3` and mount point not '/', add `nodev`.
+Kernel-FileSystems-Mount-4 | _Removable storage_ | Add `nosuid`, `nodev` and `noexec`.
+Kernel-FileSystems-Mount-5 | _Temporary storage_ | Add `nosuid`, `nodev` and `noexec`.
+Kernel-FileSystems-Mount-6 | `/dev/shm` | Add `nosuid`, `nodev` and `noexec`.
+Kernel-FileSystems-Mount-7 | `/dev` | Add `nosuid` and `noexec`.
+
+<!-- endconfig --> <!-- note -->
+
+If `CONFIG_DEVTMPFS_MOUNT` is set, then the kernel will mount /dev and will not apply the `nosuid`, `noexec` options. Either disable `CONFIG_DEVTMPFS_MOUNT` or add a remount with `noexec` and `nosuid` options to system startup.
+
+<!-- endnote --> <!-- config -->
+
+Domain | `Config` name | _State_ or `Value`
+-------------------------- | ----------------------- | -----------------------------------------------------------------------
+Kernel-FileSystems-Mount-1 | `CONFIG_DEVTMPFS_MOUNT` | _Disabled_ or add remount with `noexec` and `nosuid` to system startup.
+
+<!-- endconfig -->