added IMA settings and short IMA description

README.md

@@ -9,7 +9,7 @@ This version is tested for Ubuntu 20.04 LTS. It requires TPM-Tools 4.x as the pa
 1. Execute install.sh
 2. Reboot the machine, you will still be asked for your encryption passphrase
 3. Update the TPM PCR policy with update-luks-tpm.sh
-4. The next reboot is done automatically
+4. During the next reboot the encrypted disk will be opened automatically
 
 ## Result
 - Grub is still installed, but not used (as a fallback)
@@ -24,8 +24,8 @@ Ideas taken from
 - https://medium.com/@pawitp/full-disk-encryption-on-arch-linux-backed-by-tpm-2-0-c0892cab9704
 - https://medium.com/@pawitp/its-certainly-annoying-that-tpm2-tools-like-to-change-their-command-line-parameters-d5d0f4351206
 
-I used the PCRs 0,1,4,5,7 as policy for unlocking disk encryption. The PCRs 2,3 and 6 have the same hash value and are therefore assumed as empty.
+I used the PCRs 0-7 as policy for unlocking disk encryption. The PCRs 2,3 and 6 have the same hash value and are therefore not used.
-For additional security reasons, one may consider including these registers as well (to prevent e.g. Option ROM DMA attacks).
+However these PCRs are included as well (to prevent e.g. Option ROM DMA attacks).
 Furthermore I use the RNG on the TPM for secret generation and use SHA256 and ECC instead of SHA1 and RSA.
 
 All of the below instructions should be executed as root:
@@ -42,7 +42,7 @@ All of the below instructions should be executed as root:
 5. Update initramfs
 `update-initramfs -u -k all`
 6. Create the Kernel Command Line
-`echo "/vmlinuz-5.4.0-39-generic root=/dev/mapper/ubuntu--vg-ubuntu--lv ro" > /boot/kernel-command-line.txt`
+`echo "/vmlinuz-5.4.0-39-generic root=/dev/mapper/ubuntu--vg-ubuntu--lv ro ima_audit=1 ima_policy=appraise_tcb rootflags=i_version" > /boot/kernel-command-line.txt`
 6. Create unified Kernel
 ```
 mkdir -p /boot/efi/EFI/Linux
@@ -59,12 +59,52 @@ objcopy \
 9. Store the secret key in the TPM and use the now valid PCRs as policy
 ```
 tpm2_evictcontrol -C o -c 0x81000000 #evict an old passphrase before writing the new one
-tpm2_createpolicy --policy-pcr -l sha256:0,1,4,5,7 -L /root/policy.digest
+tpm2_createpolicy --policy-pcr -l sha256:0,1,2,3,4,5,6,7 -L /root/policy.digest
 tpm2_createprimary -C e -g sha256 -G ecc256 -c /root/primary.context
 tpm2_create -g sha256 -u /root/obj.pub -r /root/obj.priv -C /root/primary.context -L /root/policy.digest -a "noda|adminwithpolicy|fixedparent|fixedtpm" -i /root/secret.bin
 tpm2_load -C /root/primary.context -u /root/obj.pub -r /root/obj.priv -c /root/load.context
 tpm2_evictcontrol -C o -c /root/load.context 0x81000000
-# tpm2_unseal -c 0x81000000 -p pcr:sha1:0,1,4,5,7 -o /root/test.bin #proof that the persistence worked
+# tpm2_unseal -c 0x81000000 -p pcr:sha1:0,1,2,3,4,5,6,7 -o /root/test.bin #proof that the persistence worked
 rm -f /root/load.context /root/obj.priv /root/obj.pub /root/policy.digest /root/primary.context
 ```
-10. The next reboot should work automatically
+10. The next reboot should work without manual disk decryption
+
+## Integrity Measurement Architecture (IMA)
+References for IMA:
+- https://sourceforge.net/p/linux-ima/wiki/Home/
+- https://wiki.gentoo.org/wiki/Integrity_Measurement_Architecture
+- https://wiki.strongswan.org/projects/strongswan/wiki/IMA
+
+Attention! The above Docs are written for different versions of IMA and the Linux Kernel.
+
+### Manual installation
+To enable IMA, the Kernel needs the corresponding parameters as follows:
+- `ima_appraise=`
+  - `off` - no files are checked
+  - `log` - just log all measures files in the IMA log.
+  - `fix` - save the file hash of each accessed file to the file attribute 'security.ima' (used)
+  - `enforce` - only files with a valid 'security.ima' file hash can be accessed.
+- `ima_policy=` (more than one policy possible, kernel uses union of all policies)
+  - `appraise_tcb` - appraises all files owned by root (used)
+  - `tcb` - measures all executables run, all memory mapped files for execution (such as shared libraries), all Kernel modules loaded, all firmware loaded, and all files opened for read by root. (used)
+  - `secure_boot` - appraises all loaded modules, firmware, kexec'd Kernel, and IMA policies. It also requires them to have an IMA signature as well. This is normally used with the CONFIG_INTEGRITY_TRUSTED_KEYRING option in the Kernel in "secure boot" scenario, with the public key obtained from the OEM in firmware or via the MOK (Machine Owner Key) in shim.
+- `ima_hash=` (used hash algorithm
+  - `sha1` (default)
+  - `sha256`
+  - `sha512`
+  - ...
+- `ima_template=`
+  - `ima-ng` (used)
+    - template_hash=hash(filedata-hash length, filedata-hash, pathname length, pathname)
+    - filedata_hash=hash(filedata)
+  - `ima-sig`
+    - template_hash=hash(filedata-hash length, filedata-hash, pathname length, pathname)
+    - filedata_hash=hash(filedata)
+    - append signature if present
+  - `ima`
+    - template_hash=hash(filedata-hash, filename-hint)
+    - filedata_hash=hash(filedata)
+- `rootflags=i_version` - files are only measured when they are updated on the file system.
+
+The IMA log is a virtual file in `/sys/kernel/security/ima/ascii_runtime_measurements`.
+

install.sh

@@ -9,6 +9,7 @@ cp -vf ./create-luks-tpm.sh /usr/sbin || exit 1
 cp -vf ./tpm2-hook.sh /etc/initramfs-tools/hooks/ || exit 2
 awk -i inplace '/luks/{print $0 ",discard,initramfs,keyscript=/usr/sbin/passphrase-from-tpm.sh"}' /etc/crypttab
 
+cp -vf ./kernel-command-line.txt /boot/ || exit 3
 /usr/sbin/create-luks-tpm.sh
 /usr/sbin/update-kernel.sh
 efibootmgr --create --disk /dev/nvme0n1 --part 1 --label "ubuntu unified" --loader "\EFI\Linux\Linux.efi" --verbose

kernel-command-line.txt

@@ -0,0 +1 @@
+/vmlinuz-5.4.0-42-generic ima_appraise=fix ima_policy=appraise_tcb ima_policy=tcb ima_hash=sha256 root=/dev/mapper/ubuntu--vg-ubuntu--lv ro rootflags=i_version

passphrase-from-tpm.sh

@@ -1,7 +1,7 @@
 #!/bin/sh
 echo "Unlocking via TPM" >&2
 export TPM2TOOLS_TCTI="device:/dev/tpm0"
-/usr/bin/tpm2_unseal -c 0x81000000 -p pcr:sha256:0,1,4,5,7
+/usr/bin/tpm2_unseal -c 0x81000000 -p pcr:sha256:0,1,2,3,4,5,6,7
 if [ $? -eq 0 ]; then
 	exit
 fi

update-kernel.sh

@@ -8,7 +8,7 @@ update-initramfs -u -k all
 LATEST=`ls -t /boot/vmlinuz* | head -1`
 VERSION=`file -bL $LATEST | grep -o 'version [^ ]*' | cut -d ' ' -f 2`
 ### echo "/vmlinuz-$VERSION root=/dev/mapper/vg-root rw loglevel=3 cryptdevice=PARTUUID=$(blkid -o value $PARTITION_ROOT | tail -n 1):lvm:allow-discards rd.luks.options=discard" > /boot/kernel-command-line.txt #Arch command line
-echo "/vmlinuz-$VERSION root=$PARTITION_ROOT ro" > /boot/kernel-command-line.txt #Ubuntu command line
+# echo "/vmlinuz-$VERSION root=$PARTITION_ROOT ro ima_appraise=fix ima_policy=tcb ima_policy=appraise_tcb rootflags=i_version" > /boot/kernel-command-line.txt #Ubuntu command line
 objcopy \
   --add-section .osrel="/usr/lib/os-release" --change-section-vma .osrel=0x20000 \
   --add-section .cmdline="/boot/kernel-command-line.txt" --change-section-vma .cmdline=0x30000 \

update-luks-tpm.sh

@@ -5,7 +5,7 @@ set +e
 tpm2_evictcontrol -C o -c 0x81000000
 
 set -e
-tpm2_createpolicy --policy-pcr -l sha256:0,1,4,5,7 -L /root/policy.digest
+tpm2_createpolicy --policy-pcr -l sha256:0,1,2,3,4,5,6,7 -L /root/policy.digest
 tpm2_createprimary -C e -g sha256 -G ecc256 -c /root/primary.context
 tpm2_create -g sha256 -u /root/obj.pub -r /root/obj.priv -C /root/primary.context -L /root/policy.digest -a "noda|adminwithpolicy|fixedparent|fixedtpm" -i /root/secret.bin
 tpm2_load -C /root/primary.context -u /root/obj.pub -r /root/obj.priv -c /root/load.context