mirror of
https://git.code.sf.net/p/linux-ima/ima-evm-utils
synced 2025-04-29 07:03:37 +02:00
1d24a94bb5
Latest version of EVM uses file system UUID as part of an HMAC calculation to prevent pasting of inode metadata from other file systems. This patch adds support for adding file system UUID to HMAC calculation. It is necessary to specify '-u -' or '--uuid -' on evmctl command line. Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@intel.com>
92 lines
2.3 KiB
Plaintext
92 lines
2.3 KiB
Plaintext
ima-evm-utils - IMA/EVM signing utility
|
|
=========================================
|
|
|
|
Contents:
|
|
|
|
|
|
1. Key and signature formats
|
|
2. Key generation
|
|
3. Initialization
|
|
4. Signing
|
|
|
|
|
|
Key and signature formats
|
|
-------------------------
|
|
|
|
EVM support (v2) in latest version of the kernel adds the file system UUID to
|
|
the HMAC calculation. It is controlled by the CONFIG_EVM_HMAC_VERSION and
|
|
version 2 is enabled by default. To include the UUID to the signature calculation,
|
|
it is necessary to provide '--uuid -' or '-u -' parameter to the 'sign' command.
|
|
|
|
Key generation
|
|
--------------
|
|
|
|
Generate private key in plain text format
|
|
|
|
$ openssl genrsa -out privkey_evm.pem 1024
|
|
|
|
Generate encrypted private key
|
|
|
|
$ openssl genrsa -des3 -out privkey_evm.pem 1024
|
|
|
|
Make encrypted private key from unencrypted
|
|
|
|
$ openssl rsa -in /etc/keys/privkey_evm.pem -out privkey_evm_enc.pem -des3
|
|
|
|
Get public key
|
|
|
|
$ openssl rsa -pubout -in privkey_evm.pem -out pubkey_evm.pem
|
|
|
|
Copy keys to /etc/keys
|
|
|
|
$ cp pubkey_evm.pem /etc/keys
|
|
$ scp pubkey_evm.pem target:/etc/keys
|
|
|
|
|
|
Initialization
|
|
--------------
|
|
|
|
IMA/EVM initialization should be normally done from initial RAM file system
|
|
before mounting root filesystem.
|
|
|
|
Here is an example script /etc/initramfs-tools/scripts/local-top/ima.sh
|
|
|
|
# import EVM HMAC key
|
|
keyctl clear @u
|
|
keyctl add user kmk "testing123" @u
|
|
keyctl add encrypted evm-key "load `cat /etc/keys/evm-key`" @u
|
|
|
|
# import IMA public key
|
|
ima_id=`keyctl newring _ima @u`
|
|
evmctl import /etc/keys/pubkey_evm.pem $ima_id
|
|
|
|
# import EVM public key
|
|
evm_id=`keyctl newring _evm @u`
|
|
evmctl import /etc/keys/pubkey_evm.pem $evm_id
|
|
|
|
# enable EVM
|
|
echo "1" > /sys/kernel/security/evm
|
|
|
|
|
|
Signing
|
|
-------
|
|
|
|
Signing for using new the EVM HMAC format is done using '-u -' or '--uuid -' parameter.
|
|
|
|
Sign file with EVM signature and use hash value for IMA - common case
|
|
|
|
$ evmctl sign [-u -] --imahash test.txt
|
|
|
|
Sign file with both IMA and EVM signatures - for immutable files
|
|
|
|
$ evmctl sign [-u -] --imasig test.txt
|
|
|
|
Label whole filesystem with EVM signatures
|
|
|
|
$ find / \( -fstype rootfs -o -fstype ext4 \) -exec evmctl sign [-u -] --imahash '{}' \;
|
|
|
|
Label filesystem in fix mode - kernel sets correct values to IMA and EVM xattrs
|
|
|
|
$ find / \( -fstype rootfs -o -fstype ext4 \) -exec sh -c "< '{}'" \;
|
|
|