WIP: Resize encrypted partitions

cloudinit/config/cc_growpart.py

@@ -63,11 +63,14 @@
             - "/dev/vdb1"
         ignore_growroot_disabled: <true/false>
 """
-
+import base64
+import copy
+import json
 import os
 import os.path
 import re
 import stat
+from contextlib import suppress
 
 from cloudinit import log as logging
 from cloudinit.settings import PER_ALWAYS
@@ -83,6 +86,8 @@
     'ignore_growroot_disabled': False,
 }
 
+KEYDATA_PATH = "/cc_growpart_keydata"
+
 
 class RESIZE(object):
     SKIPPED = "SKIPPED"
@@ -286,10 +291,83 @@ def devent2dev(devent):
     return dev
 
 
+def get_mapped_device(blockdev):
+    """Returns underlying block device for a mapped device.
+
+    If blockdev is a symlink pointing to a /dev/dm-* device, return
+    the device pointed to. Otherwise, return None.
+    """
+    realpath = os.path.realpath(blockdev)
+    if realpath.startswith("/dev/dm-"):
+        LOG.debug("%s is a mapped device pointing to %s", blockdev, realpath)
+        return realpath
+    return None
+
+
+def is_encrypted(blockdev) -> bool:
+    """
+    Check if a device is an encrypted device. blockdev should have
+    a /dev/dm-* path.
+    """
+    if not subp.which("cryptsetup"):
+        LOG.debug("cryptsetup not found. Assuming no encrypted partitions")
+        return False
+    is_encrypted = False
+    with suppress(subp.ProcessExecutionError):
+        subp.subp(["cryptsetup", "status", blockdev])
+        is_encrypted = True
+    LOG.debug(
+        "Determined that %s is %s encrypted",
+        blockdev,
+        "" if is_encrypted else "not"
+    )
+    return is_encrypted
+
+
+def get_underlying_partition(blockdev):
+    command = ["dmsetup", "deps", "--options=devname", blockdev]
+    dep = subp.subp(command)[0]
+    try:
+        # Returned result should look something like:
+        # 1 dependencies : (vdb1)
+        return "/dev/{}".format(dep.split(": (")[1].split(")")[0])
+    except IndexError:
+        raise Exception(
+            "Ran `{}`, but received unexpected stdout: `{}`".format(
+                command, dep))
+
+
+def resize_encrypted(blockdev, partition):
+    """Use 'cryptsetup resize' to resize LUKS volume.
+
+    The loaded keyfile is json formatted with 'key' and 'slot' keys.
+    key is base64 encoded. Example:
+    {"key":"XFmCwX2FHIQp0LBWaLEMiHIyfxt1SGm16VvUAVledlY=","slot":5}
+    """
+    try:
+        with open(KEYDATA_PATH) as f:
+            keydata = json.load(f)
+        key = keydata["key"]
+        decoded_key = base64.b64decode(key)
+        slot = keydata["slot"]
+    except Exception as e:
+        raise Exception("Could not load encryption key") from e
+    subp.subp(
+        ["cryptsetup", "--key-file", "-", "resize", blockdev],
+        data=decoded_key,
+    )
+    subp.subp([
+        "cryptsetup", "luksKillSlot", "--batch-mode", partition, str(slot)
+    ])
+
+
 def resize_devices(resizer, devices):
     # returns a tuple of tuples containing (entry-in-devices, action, message)
+    devices = copy.copy(devices)
     info = []
-    for devent in devices:
+
+    while devices:
+        devent = devices.pop(0)
         try:
             blockdev = devent2dev(devent)
         except ValueError as e:
@@ -310,6 +388,29 @@ def resize_devices(resizer, devices):
                          "device '%s' not a block device" % blockdev,))
             continue
 
+        underlying_blockdev = get_mapped_device(blockdev)
+        if underlying_blockdev and is_encrypted(underlying_blockdev):
+            try:
+                # We need to resize the underlying partition first
+                partition = get_underlying_partition(blockdev)
+                if partition not in [x[0] for x in info]:
+                    # We shouldn't attempt to resize this mapped partition
+                    # until the underlying partition is resized, so re-add
+                    # our device to the beginning of the list we're iterating
+                    # over, then add our underlying partition so it can
+                    # get processed first
+                    devices.insert(0, devent)
+                    devices.insert(0, partition)
+                    continue
+                resize_encrypted(blockdev, partition)
+            except Exception as e:
+                info.append((
+                    devent,
+                    RESIZE.FAILED,
+                    "Resizing encrypted device ({}) failed: {}".format(
+                        blockdev, e
+                    )
+                ))
         try:
             (disk, ptnum) = device_part_info(blockdev)
         except (TypeError, ValueError) as e:

cloudinit/subp.py

@@ -4,6 +4,7 @@
 import logging
 import os
 import subprocess
+from typing import Tuple, Any
 
 from errno import ENOEXEC
 
@@ -141,10 +142,12 @@ def _indent_text(self, text, indent_level=8):
         return text.rstrip(cr).replace(cr, cr + indent)
 
 
-def subp(args, data=None, rcs=None, env=None, capture=True,
-         combine_capture=False, shell=False,
-         logstring=False, decode="replace", target=None, update_env=None,
-         status_cb=None, cwd=None):
+def subp(
+    args, data=None, rcs=None, env=None, capture=True,
+    combine_capture=False, shell=False,
+    logstring=False, decode="replace", target=None, update_env=None,
+    status_cb=None, cwd=None
+) -> Tuple[Any, Any]:
     """Run a subprocess.
 
     :param args: command to run in a list. [cmd, arg1, arg2...]