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Unified Diff: docs/system_hardening_features.md

Issue 1309473002: WIP: Migrate Wiki content over to src/docs (Closed) Base URL: https://chromium.googlesource.com/chromium/src.git@master
Patch Set: Created 5 years, 4 months ago
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Index: docs/system_hardening_features.md
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+# Introduction
+
+This is a list of current and planned Chrome OS security features. Each feature is listed together with its rationale and status. This should serve as a checklist and status update on Chrome OS security.
+
+
+
+# Details
+
+## General Linux features
+
+| **Feature** | **Status** | **Rationale** | **Tests** | **Bug** | **More thoughts or work needed?** |
+|:------------|:-----------|:--------------|:----------|:--------|:----------------------------------|
+| No Open Ports | implemented | Reduce attack surface of listening services. | [security\_NetworkListeners](http://git.chromium.org/gitweb/?p=chromiumos/third_party/autotest.git;a=tree;f=client/site_tests/security_NetworkListeners) | | Runtime test has to whitelist test-system-only "noise" like sshd. See Issue 22412 (on Google Code) and [ensure\_\*](http://git.chromium.org/gitweb/?p=chromiumos/platform/vboot_reference.git;a=tree;f=scripts/image_signing) for offsetting tests ensuring these aren't on Release builds. |
+| Password Hashing | When there is no TPM, scrypt is used. | Frustrate brute force attempts at recovering passwords. |
+| SYN cookies | needs functional test | In unlikely event of SYN flood, act sanely. | [kernel\_ConfigVerify](http://git.chromium.org/gitweb/?p=chromiumos/third_party/autotest.git;a=tree;f=client/site_tests/kernel_ConfigVerify) |
+| Filesystem Capabilities | runtime use only | allow root privilege segmentation | [security\_Minijail0](http://git.chromium.org/gitweb/?p=chromiumos/third_party/autotest.git;a=tree;f=client/site_tests/security_Minijail0) |
+| Firewall | needs functional test | Block unexpected network listeners to frustrate remote access. | | Issue 23089 (on Google Code) |
+| PR\_SET\_SECCOMP | needs functional test | Available for extremely restricted sandboxing. | [kernel\_ConfigVerify](http://git.chromium.org/gitweb/?p=chromiumos/third_party/autotest.git;a=tree;f=client/site_tests/kernel_ConfigVerify) | Issue 23090 (on Google Code) |
+| AppArmor | not used |
+| SELinux | not used |
+| SMACK | not used |
+| Encrypted LVM | not used |
+| eCryptFS | implemented | Keep per-user data private. | [login\_Cryptohome\*](http://git.chromium.org/gitweb/?p=chromiumos/third_party/autotest.git;a=tree;f=client/site_tests) |
+| glibc Stack Protector | needs functional test | Block string-buffer-on-stack-overflow attacks from rewriting saved IP. | | Issue 23101 (on Google Code) | -fstack-protector-strong is used for almost all packages |
+| glibc Heap Protector | needs functional test | Block heap unlink/double-free/etc corruption attacks. | | Issue 23101 (on Google Code) |
+| glibc Pointer Obfuscation | needs functional test | Frustrate heap corruption attacks using saved libc func ptrs. | | Issue 23101 (on Google Code) | includes FILE pointer managling |
+| Stack ASLR | needs functional test | Frustrate stack memory attacks that need known locations. | | |
+| Libs/mmap ASLR | needs functional test | Frustrate return-to-library and ROP attacks. | | |
+| Exec ASLR | needs functional test | Needs PIE, used to frustrate ROP attacks. | | |
+| brk ASLR | needs functional test | Frustrate brk-memory attacks that need known locations. | [kernel\_ConfigVerify](http://git.chromium.org/gitweb/?p=chromiumos/third_party/autotest.git;a=tree;f=client/site_tests/kernel_ConfigVerify) | |
+| VDSO ASLR | needs functional test | Frustrate return-to-VDSO attacks. | [kernel\_ConfigVerify](http://git.chromium.org/gitweb/?p=chromiumos/third_party/autotest.git;a=tree;f=client/site_tests/kernel_ConfigVerify) | |
+| Built PIE | needs functional test | Take advantage of exec ASLR. | [platform\_ToolchainOptions](http://git.chromium.org/gitweb/?p=chromiumos/third_party/autotest.git;a=tree;f=client/site_tests/platform_ToolchainOptions) | |
+| Built _FORTIFY\_SOURCE_| needs functional test | Catch overflows and other detectable security problems. | | |
+| Built RELRO | needs functional test | Reduce available locations to gain execution control. | [platform\_ToolchainOptions](http://git.chromium.org/gitweb/?p=chromiumos/third_party/autotest.git;a=tree;f=client/site_tests/platform_ToolchainOptions) | |
+| Built BIND\_NOW | needs functional test | With RELRO, really reduce available locations. | [platform\_ToolchainOptions](http://git.chromium.org/gitweb/?p=chromiumos/third_party/autotest.git;a=tree;f=client/site_tests/platform_ToolchainOptions) | |
+| Non-exec memory | needs functional test | Block execution of malicious data regions. | [kernel\_ConfigVerify](http://git.chromium.org/gitweb/?p=chromiumos/third_party/autotest.git;a=tree;f=client/site_tests/kernel_ConfigVerify) |
+| /proc/PID/maps protection | needs functional test | Block access to ASLR locations of other processes. |
+| Symlink restrictions | implemented | Block /tmp race attacks. | [security\_SymlinkRestrictions.py](http://git.chromium.org/gitweb/?p=chromiumos/third_party/autotest.git;a=blob;f=client/site_tests/security_SymlinkRestrictions/security_SymlinkRestrictions.py) | Issue 22137 (on Google Code) |
+| Hardlink restrictions | implemented | Block hardlink attacks. | [security\_HardlinkRestrictions.py](http://git.chromium.org/gitweb/?p=chromiumos/third_party/autotest.git;a=blob;f=client/site_tests/security_HardlinkRestrictions/security_HardlinkRestrictions.py) | Issue 22137 (on Google Code) |
+| ptrace scoping | implemented | Block access to in-process credentials. | [security\_ptraceRestrictions.py](http://git.chromium.org/gitweb/?p=chromiumos/third_party/autotest.git;a=blob;f=client/site_tests/security_ptraceRestrictions/security_ptraceRestrictions.py) | Issue 22137 (on Google Code) |
+| 0-address protection | needs functional test | Block kernel NULL-deref attacks. | [kernel\_ConfigVerify](http://git.chromium.org/gitweb/?p=chromiumos/third_party/autotest.git;a=tree;f=client/site_tests/kernel_ConfigVerify) |
+| /dev/mem protection | needs functional test | Block kernel root kits and privacy loss. | [kernel\_ConfigVerify](http://git.chromium.org/gitweb/?p=chromiumos/third_party/autotest.git;a=tree;f=client/site_tests/kernel_ConfigVerify) | Issue 21553 (on Google Code) | crash\_reporter uses ramoops via /dev/mem |
+| /dev/kmem protection | needs functional test | Block kernel root kits and privacy loss. | [kernel\_ConfigVerify](http://git.chromium.org/gitweb/?p=chromiumos/third_party/autotest.git;a=tree;f=client/site_tests/kernel_ConfigVerify) |
+| disable kernel module loading | how about module signing instead? | Block kernel root kits and privacy loss. |
+| read-only kernel data sections | needs functional test | Block malicious manipulation of kernel data structures. | [kernel\_ConfigVerify](http://git.chromium.org/gitweb/?p=chromiumos/third_party/autotest.git;a=tree;f=client/site_tests/kernel_ConfigVerify) |
+| kernel stack protector | needs functional test | Catch character buffer overflow attacks. | [kernel\_ConfigVerify](http://git.chromium.org/gitweb/?p=chromiumos/third_party/autotest.git;a=tree;f=client/site_tests/kernel_ConfigVerify) |
+| kernel module RO/NX | needs functional test | Block malicious manipulation of kernel data structures. | [kernel\_ConfigVerify](http://git.chromium.org/gitweb/?p=chromiumos/third_party/autotest.git;a=tree;f=client/site_tests/kernel_ConfigVerify) |
+| kernel address display restriction | needs config and functional test | Frustrate kernel exploits that need memory locations. | | | Was disabled by default in 3.x kernels. |
+| disable debug interfaces for non-root users | needs config and functional test | Frustrate kernel exploits that depend on debugfs | | Issue 23758 (on Google Code) |
+| disable ACPI custom\_method | needs config and functional test | Frustrate kernel exploits that depend on root access to physical memory | | Issue 23759 (on Google Code) |
+| unreadable kernel files | needs config and functional test | Frustrate automated kernel exploits that depend access to various kernel resources | | Issue 23761 (on Google Code) |
+| blacklist rare network modules | needs functional test | Reduce attack surface of available kernel interfaces. |
+| syscall filtering | needs functional testing | Reduce attack surface of available kernel interfaces. | | Issue 23150 (on Google Code) |
+| vsyscall ASLR | medium priority | Reduce ROP target surface. |
+| Limited use of suid binaries | implemented | Potentially dangerous, so minimize use. | [security\_SuidBinaries](http://git.chromium.org/gitweb/?p=chromiumos/third_party/autotest.git;a=tree;f=client/site_tests/security_SuidBinaries) |
+
+## Chrome OS specific features
+
+ * We use `minijail` for sandboxing:
+ * [Design doc](http://www.chromium.org/chromium-os/chromiumos-design-docs/system-hardening#Detailed_Design_73859539098644_6227793370126997)
+ * Issue 380 (on Google Code)
+ * Current sandboxing status:
+
+| | | | | **Exposure** | | | | | **Privileges** | | **Sandbox** |
+|:-|:-|:-|:-|:-------------|:-|:-|:-|:-|:---------------|:-|:------------|
+| **Service/daemon** | **Overall status** | **Usage** | **Comments** | **Network traffic** | **User input** | **DBus** | **Hardware (udev)** | **FS (config files, etc.)** | **Runs as** | **Privileges needed?** | **uid** | **gid** | **Namespaces** | **Caps** | **seccomp\_filters** |
+| udevd | Low pri | Listens to udev events via netfilter socket | | No | No | No | Yes | No | root | Probably | No | No | No | No | No |
+| session-manager | <font color='yellow'>P2</font>| | Launched from /sbin/session\_manager\_setup.sh | No | No | Yes | No | No | root | Probably | No | No | No | No | No |
+| rsyslogd | Low pri | Logging | | No | No | No | No | Yes | root | Probably | No | | No | No | No |
+| dbus-daemon | Low pri | IPC | Listens on Unix domain socket | Unix domain socket | | Yes | | | messagebus | Yes | Yes | Yes | No | No | No |
+| powerm | <font color='yellow'>P2</font>| Suspend to RAM and system shutdown. Handles input events for hall effect sensor (lid) and power button. | | No | No | Yes | Yes | Yes | root | Probably | No | No | No | No | No |
+| wpa\_supplicant | Low pri | WPA auth | | Yes | Via flimflam | Yes | No | Yes, exposes management API through FS | wpa | Yes | Yes | Yes | No | Yes | No |
+| shill | <font color='red'>P0</font>| Connection manager | | Yes | Yes | Yes | Yes | Yes | root | Probably | No | No | No | No | No |
+| X | <font color='orange'>P1</font>| | | No (-nolisten tcp) | Yes | No | GPU | Yes | root | x86: no, ARM: yes | No | No | No | No | No |
+| htpdate | Low pri | Setting date and time | | Yes | No | No | No | No | ntp | Yes | Yes | Yes | No | No | No |
+| cashewd | Low pri | Network usage tracking | | No | No | Yes | No | No | cashew | Yes | Yes | Yes | No | No | No |
+| chapsd | Low pri | PKCS#11 implementation | | No | No | Yes | No | No | chaps | Yes | Yes | Yes | No | No | No |
+| cryptohomed | <font color='orange'>P1</font>| Encrypted user storage | | No | Yes | Yes | No | No | root | Probably | No | No | No | No | No |
+| powerd | Low pri | Idle or video activity detection. Dimming the backlight or turning off the screen, adjusting backlight intensity. Monitors plug state (on ac or on battery) and battery state-of-charge. | | No | Yes | Yes | Yes | Yes | powerd | Probably | Yes | No | No | No | No |
+| modem-manager | <font color='orange'>P1</font>| Manages 3G modems | | Indirectly | Yes | Yes | Yes | No | root | Probably not | No | No | No | No | No |
+| gavd | <font color='yellow'>P2</font>| Audio/video events and routing | | No | Yes | Yes | Yes | No | gavd | Yes | Yes | Yes | No | No | No |
+| dhcpcd | Low pri | DHCP client | | Yes | Indirectly | No | No | No | dhcp | Yes | Yes | Yes | No | Yes | No |
+| metrics\_daemon | <font color='yellow'>P2</font>| Metrics collection and uploading | | Yes, but shouldn't listen | No | Yes | No | No | root | Probably not | No | No | No | No | No |
+| cros-disks/disks | <font color='orange'>P1</font>| Removable media handling | | No | Yes | Yes | Yes | No | root | Launches minijail | No | No | No | No | No |
+| avfsd | Low pri | Compressed file handling | Launched from cros-disks, uses minijail | Not in Chrome OS | Yes | No | No | Yes | avfs | Yes | Yes | | No | Yes | Yes |
+| update\_engine | <font color='red'>P0</font>| System updates | | Yes | No | Yes | No | No | root | Probably | No | No | No | No | No |
+| cromo | Low pri | Supports Gobi 3G modems | | Indirectly | Yes | Yes | Yes | Probably | cromo | Yes | Yes | Yes | No | No | No |
+| bluetoothd | Low pri | | | Yes | Yes | Yes | Yes | Yes | bluetooth | Yes | Yes | Yes | No | Yes | No |
+| unclutter | Low pri | Hides cursor while typing | | | Yes | | | | chronos | Yes | Yes (via sudo) | No | No | No | No |
+| cras | <font color='yellow'>P2</font>| Audio server | | No | Yes | Yes | Yes | No | cras | Yes | Yes | Yes | No | No | No |
+| tcsd | <font color='yellow'>P2</font>| Portal to the TPM device driver | | No | Yes | Yes | Yes | Yes | tss | Yes | Yes | Yes | No | No | No |
+| keyboard\_touchpad\_helper | <font color='orange'>P1</font>| Disables touchpad when typing | | | Yes | | | | root | Probably not | No | No | No | No | No |
+| logger | Low pri | Redirects stderr for several daemons to syslog | | Indirectly | Indirectly | No | No | No | syslog | Yes | Yes | Yes | No | No | No |
+| login | <font color='yellow'>P2</font>| Helps organize Upstart events | | No | Indirectly | Yes | No | Yes | root | Probably | No | No | No | No | No |
+| wimax-manager | <font color='orange'>P1</font>| | Includes third-party library | Yes | Indirectly | Yes | Yes | Yes | root | Probably not | No | No | No | No | No |
+| mtpd | <font color='yellow'>P2</font>| Manages MTP devices | Includes third-party library | No | Yes | Yes | Yes | No | mtp | Yes | Yes | Yes | No | Not needed | Yes |
+| **Service/daemon** | **Overall status** | **Usage** | **Comments** | **Network traffic** | **User input** | **DBus** | **Hardware (udev)** | **FS (config files, etc.)** | **Runs as** | **Privileges needed?** | **uid** | **gid** | **Namespaces** | **Caps** | **seccomp\_filters** |
+| | | | | **Exposure** | | | | | **Privileges** | | **Sandbox** |
+
+Enforced by [security\_SandboxedServices](http://git.chromium.org/gitweb/?p=chromiumos/third_party/autotest.git;a=tree;f=client/site_tests/security_SandboxedServices)
+
+# References
+
+ * https://wiki.ubuntu.com/Security/Features
+ * http://wiki.debian.org/Hardening
+ * http://www.gentoo.org/proj/en/hardened/hardened-toolchain.xml
+ * http://www.awe.com/mark/blog/20101130.html
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