config: T4919: Add support for encrypted config file with TPM

1 files changed, 276 insertions, 0 deletions

diff --git a/src/helpers/vyos-config-encrypt.py b/src/helpers/vyos-config-encrypt.py
new file mode 100755
index 000000000..8f7359767
--- /dev/null
+++ b/src/helpers/vyos-config-encrypt.py
@@ -0,0 +1,276 @@
+#!/usr/bin/env python3
+#
+# Copyright (C) 2024 VyOS maintainers and contributors
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 or later as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import os
+import re
+import shutil
+import sys
+
+from argparse import ArgumentParser
+from cryptography.fernet import Fernet
+from tempfile import NamedTemporaryFile
+from tempfile import TemporaryDirectory
+
+from vyos.tpm import clear_tpm_key
+from vyos.tpm import init_tpm
+from vyos.tpm import read_tpm_key
+from vyos.tpm import write_tpm_key
+from vyos.util import ask_input
+from vyos.util import ask_yes_no
+from vyos.util import cmd
+
+persistpath_cmd = '/opt/vyatta/sbin/vyos-persistpath'
+mount_paths = ['/config', '/opt/vyatta/etc/config']
+dm_device = '/dev/mapper/vyos_config'
+
+def is_opened():
+    return os.path.exists(dm_device)
+
+def get_current_image():
+    with open('/proc/cmdline', 'r') as f:
+        args = f.read().split(" ")
+        for arg in args:
+            if 'vyos-union' in arg:
+                k, v = arg.split("=")
+                path_split = v.split("/")
+                return path_split[-1]
+    return None
+
+def load_config(key):
+    if not key:
+        return
+
+    persist_path = cmd(persistpath_cmd).strip()
+    image_name = get_current_image()
+    image_path = os.path.join(persist_path, 'luks', image_name)
+
+    if not os.path.exists(image_path):
+        raise Exception("Encrypted config volume doesn't exist")
+
+    if is_opened():
+        print('Encrypted config volume is already mounted')
+        return
+
+    with NamedTemporaryFile(dir='/dev/shm', delete=False) as f:
+        f.write(key)
+        key_file = f.name
+
+    cmd(f'cryptsetup -q open {image_path} vyos_config --key-file={key_file}')
+
+    for path in mount_paths:
+        cmd(f'mount /dev/mapper/vyos_config {path}')
+        cmd(f'chgrp -R vyattacfg {path}')
+
+    os.unlink(key_file)
+
+    return True
+
+def encrypt_config(key, recovery_key):
+    if is_opened():
+        raise Exception('An encrypted config volume is already mapped')
+
+    # Clear and write key to TPM
+    try:
+        clear_tpm_key()
+    except:
+        pass
+    write_tpm_key(key)
+
+    persist_path = cmd(persistpath_cmd).strip()
+    size = ask_input('Enter size of encrypted config partition (MB): ', numeric_only=True, default=512)
+
+    luks_folder = os.path.join(persist_path, 'luks')
+
+    if not os.path.isdir(luks_folder):
+        os.mkdir(luks_folder)
+
+    image_name = get_current_image()
+    image_path = os.path.join(luks_folder, image_name)
+
+    # Create file for encrypted config
+    cmd(f'fallocate -l {size}M {image_path}')
+
+    # Write TPM key for slot #1
+    with NamedTemporaryFile(dir='/dev/shm', delete=False) as f:
+        f.write(key)
+        key_file = f.name
+
+    # Format and add main key to volume
+    cmd(f'cryptsetup -q luksFormat {image_path} {key_file}')
+
+    if recovery_key:
+        # Write recovery key for slot 2
+        with NamedTemporaryFile(dir='/dev/shm', delete=False) as f:
+            f.write(recovery_key)
+            recovery_key_file = f.name
+
+        cmd(f'cryptsetup -q luksAddKey {image_path} {recovery_key_file} --key-file={key_file}')
+
+    # Open encrypted volume and format with ext4
+    cmd(f'cryptsetup -q open {image_path} vyos_config --key-file={key_file}')
+    cmd('mkfs.ext4 /dev/mapper/vyos_config')
+
+    with TemporaryDirectory() as d:
+        cmd(f'mount /dev/mapper/vyos_config {d}')
+
+        # Move /config to encrypted volume
+        shutil.copytree('/config', d, copy_function=shutil.move, dirs_exist_ok=True)
+
+        cmd(f'umount {d}')
+
+    os.unlink(key_file)
+
+    if recovery_key:
+        os.unlink(recovery_key_file)
+
+    for path in mount_paths:
+        cmd(f'mount /dev/mapper/vyos_config {path}')
+        cmd(f'chgrp vyattacfg {path}')
+
+    return True
+
+def decrypt_config(key):
+    if not key:
+        return
+
+    persist_path = cmd(persistpath_cmd).strip()
+    image_name = get_current_image()
+    image_path = os.path.join(persist_path, 'luks', image_name)
+
+    if not os.path.exists(image_path):
+        raise Exception("Encrypted config volume doesn't exist")
+
+    key_file = None
+
+    if not is_opened():
+        with NamedTemporaryFile(dir='/dev/shm', delete=False) as f:
+            f.write(key)
+            key_file = f.name
+
+        cmd(f'cryptsetup -q open {image_path} vyos_config --key-file={key_file}')
+
+    # unmount encrypted volume mount points
+    for path in mount_paths:
+        if os.path.ismount(path):
+            cmd(f'umount {path}')
+
+    # If /config is populated, move to /config.old
+    if len(os.listdir('/config')) > 0:
+        print('Moving existing /config folder to /config.old')
+        shutil.move('/config', '/config.old')
+
+    # Temporarily mount encrypted volume and migrate files to /config on rootfs
+    with TemporaryDirectory() as d:
+        cmd(f'mount /dev/mapper/vyos_config {d}')
+
+        # Move encrypted volume to /config
+        shutil.copytree(d, '/config', copy_function=shutil.move, dirs_exist_ok=True)
+        cmd(f'chgrp -R vyattacfg /config')
+
+        cmd(f'umount {d}')
+
+    # Close encrypted volume
+    cmd('cryptsetup -q close vyos_config')
+
+    # Remove encrypted volume image file and key
+    if key_file:
+        os.unlink(key_file)
+    os.unlink(image_path)
+
+    try:
+        clear_tpm_key()
+    except:
+        pass
+
+    return True
+
+if __name__ == '__main__':
+    if len(sys.argv) < 2:
+        print("Must specify action.")
+        sys.exit(1)
+
+    parser = ArgumentParser(description='Config encryption')
+    parser.add_argument('--disable', help='Disable encryption', action="store_true")
+    parser.add_argument('--enable', help='Enable encryption', action="store_true")
+    parser.add_argument('--load', help='Load encrypted config volume', action="store_true")
+    args = parser.parse_args()
+
+    tpm_exists = os.path.exists('/sys/class/tpm/tpm0')
+
+    key = None
+    recovery_key = None
+    need_recovery = False
+
+    question_key_str = 'recovery key' if tpm_exists else 'key'
+
+    if tpm_exists:
+        if args.enable:
+            key = Fernet.generate_key()
+        elif args.disable or args.load:
+            try:
+                key = read_tpm_key()
+                need_recovery = False
+            except:
+                print('Failed to read key from TPM, recovery key required')
+                need_recovery = True
+    else:
+        need_recovery = True
+
+    if args.enable and not tpm_exists:
+        print('WARNING: VyOS will boot into a default config when encrypted without a TPM')
+        print('You will need to manually login with default credentials and use "encryption load"')
+        print('to mount the encrypted volume and use "load /config/config.boot"')
+
+        if not ask_yes_no('Are you sure you want to proceed?'):
+            sys.exit(0)
+
+    if need_recovery or (args.enable and not ask_yes_no(f'Automatically generate a {question_key_str}?', default=True)):
+        while True:
+            recovery_key = ask_input(f'Enter {question_key_str}:', default=None).encode()
+
+            if len(recovery_key) >= 32:
+                break
+
+            print('Invalid key - must be at least 32 characters, try again.')
+    else:
+        recovery_key = Fernet.generate_key()
+
+    try:
+        if args.disable:
+            decrypt_config(key or recovery_key)
+
+            print('Encrypted config volume has been disabled')
+            print('Contents have been migrated to /config on rootfs')
+        elif args.load:
+            load_config(key or recovery_key)
+
+            print('Encrypted config volume has been mounted')
+            print('Use "load /config/config.boot" to load configuration')
+        elif args.enable and tpm_exists:
+            encrypt_config(key, recovery_key)
+
+            print('Encrypted config volume has been enabled with TPM')
+            print('Backup the recovery key in a safe place!')
+            print('Recovery key: ' + recovery_key.decode())
+        elif args.enable:
+            encrypt_config(recovery_key)
+
+            print('Encrypted config volume has been enabled without TPM')
+            print('Backup the key in a safe place!')
+            print('Key: ' + recovery_key.decode())
+    except Exception as e:
+        word = 'decrypt' if args.disable or args.load else 'encrypt'
+        print(f'Failed to {word} config: {e}')