If the user has supplied a backup password in Settings, that password
is validated during the full backup process and is used as an encryption
key for encoding the backed-up data itself. This is the fundamental
mechanism whereby users can secure their data even against malicious
parties getting physical unlocked access to their device.
Technically the user-supplied password is not used as the encryption
key for the backed-up data itself. What is actually done is that a
random key is generated to use as the raw encryption key. THAT key,
in turn, is encrypted with the user-supplied password (after random
salting and key expansion with PBKDF2). The encrypted master key
and a checksum are stored in the backup header. At restore time,
the user supplies their password, which allows the system to decrypt
the master key, which in turn allows the decryption of the backup
data itself.
The checksum is part of the archive in order to permit validation
of the user-supplied password. The checksum is the result of running
the user-supplied password through PBKDF2 with a randomly selected
salt. At restore time, the proposed password is run through PBKDF2
with the salt described by the archive header. If the result does
not match the archive's stated checksum, then the user has supplied
the wrong decryption password.
Also, suppress backup consideration for a few packages whose
data is either nonexistent or inapplicable across devices or
factory reset operations.
Bug 4901637
Change-Id: Id0cc9d0fdfc046602b129f273d48e23b7a14df36
New methods for full backup/restore have been added to BackupAgent
(still hidden): onFullBackup() and onRestoreFile(). The former is the
entry point for a full app backup to adb/socket/etc: the app then writes
all of its files, entire, to the output. During restore, the latter
new callback is invoked, once for each file being restored.
The full backup/restore interface does not use the previously-defined
BackupDataInput / BackupDataOutput classes, because those classes
provide an API designed for incremental key/value data structuring.
Instead, a new FullBackupDataOutput class has been introduced, through
which we restrict apps' abilities to write data during a full backup
operation to *only* writing entire on-disk files via a new BackupAgent
method called fullBackupFile().
"FullBackupAgent" exists now solely as a concrete shell class that
can be instantiated in the case of apps that do not have their own
BackupAgent implementations.
Along with the API change, responsibility for backing up the .apk
file and OBB container has been moved into the framework rather than
have the application side of the transaction do it.
Change-Id: I12849b06b1a6e4c44d080587c1e9828a52b70dae
Every available shared-storage volume is backed up, tagged with its
ordinal in the set of mounted shared volumes. This is an approximation
of "internal + the external card". This lets us restore things to the
same volume [or "equivalent" volume, in the case of a cross-model
restore] as they originated on.
Also fixed a bug in the handling of files/dirs with spaces in
their names.
Change-Id: I380019da8d0bb5b3699bd7c11eeff621a88e78c3
Usage: adb restore [tarfilename]
Restores app data [and installs the apps if necessary from the backup
file] captured in a previous invocation of 'adb backup'. The user
must explicitly acknowledge the action on-device before it is allowed
to proceed; this prevents any "invisible" pushes of content from the
host to the device.
Known issues:
* The settings databases and wallpaper are saved/restored, but lots
of other system state is not yet captured in the full backup. This
means that for practical purposes this is usable for 3rd party
apps at present but not for full-system cloning/imaging.
Change-Id: I0c748b645845e7c9178e30bf142857861a64efd3
This is the basic infrastructure for pulling a full(*) backup of the
device's data over an adb(**) connection to the local device. The
basic process consists of these interacting pieces:
1. The framework's BackupManagerService, which coordinates the
collection of app data and routing to the destination.
2. A new framework-provided BackupAgent implementation called
FullBackupAgent, which is instantiated in the target applications'
processes in turn, and knows how to emit a datastream that contains
all of the app's saved data files.
3. A new shell-level program called "bu" that is used to bridge from
adb to the framework's Backup Manager.
4. adb itself, which now knows how to use 'bu' to kick off a backup
operation and pull the resulting data stream to the desktop host.
5. A system-provided application that verifies with the user that
an attempted backup/restore operation is in fact expected and to
be allowed.
The full agent implementation is not used during normal operation of
the delta-based app-customized remote backup process. Instead it's
used during user-confirmed *full* backup of applications and all their
data to a local destination, e.g. via the adb connection.
The output format is 'tar'. This makes it very easy for the end
user to examine the resulting dataset, e.g. for purpose of extracting
files for debug purposes; as well as making it easy to contemplate
adding things like a direct gzip stage to the data pipeline during
backup/restore. It also makes it convenient to construct and maintain
synthetic backup datasets for testing purposes.
Within the tar format, certain artificial conventions are used.
All files are stored within top-level directories according to
their semantic origin:
apps/pkgname/a/ : Application .apk file itself
apps/pkgname/obb/: The application's associated .obb containers
apps/pkgname/f/ : The subtree rooted at the getFilesDir() location
apps/pkgname/db/ : The subtree rooted at the getDatabasePath() parent
apps/pkgname/sp/ : The subtree rooted at the getSharedPrefsFile() parent
apps/pkgname/r/ : Files stored relative to the root of the app's file tree
apps/pkgname/c/ : Reserved for the app's getCacheDir() tree; not stored.
For each package, the first entry in the tar stream is a file called
"_manifest", nominally rooted at apps/pkgname. This file contains some
metadata about the package whose data is stored in the archive.
The contents of shared storage can optionally be included in the tar
stream. It is placed in the synthetic location:
shared/...
uid/gid are ignored; app uids are assigned at install time, and the
app's data is handled from within its own execution environment, so
will automatically have the app's correct uid.
Forward-locked .apk files are never backed up. System-partition
.apk files are not backed up unless they have been overridden by a
post-factory upgrade, in which case the current .apk *is* backed up --
i.e. the .apk that matches the on-disk data. The manifest preceding
each application's portion of the tar stream provides version numbers
and signature blocks for version checking, as well as an indication
of whether the restore logic should expect to install the .apk before
extracting the data.
System packages can designate their own full backup agents. This is
to manage things like the settings provider which (a) cannot be shut
down on the fly in order to do a clean snapshot of their file trees,
and (b) manage data that is not only irrelevant but actively hostile
to non-identical devices -- CDMA telephony settings would seriously
mess up a GSM device if emplaced there blind, for example.
When a full backup or restore is initiated from adb, the system will
present a confirmation UI that the user must explicitly respond to
within a short [~ 30 seconds] timeout. This is to avoid the
possibility of malicious desktop-side software secretly grabbing a copy
of all the user's data for nefarious purposes.
(*) The backup is not strictly a full mirror. In particular, the
settings database is not cloned; it is handled the same way that
it is in cloud backup/restore. This is because some settings
are actively destructive if cloned onto a different (or
especially a different-model) device: telephony settings and
AndroidID are good examples of this.
(**) On the framework side it doesn't care that it's adb; it just
sends the tar stream to a file descriptor. This can easily be
retargeted around whatever transport we might decide to use
in the future.
KNOWN ISSUES:
* the security UI is desperately ugly; no proper designs have yet
been done for it
* restore is not yet implemented
* shared storage backup is not yet implemented
* symlinks aren't yet handled, though some infrastructure for
dealing with them has been put in place.
Change-Id: Ia8347611e23b398af36ea22c36dff0a276b1ce91
If the dimensions of the original are sufficiently different from the
device's preferred dimensions, just don't restore the image. This
avoids bad letterboxing / clipping on e.g. phone <-> tablet data
migration.
The expansion/shrinkage ratios used here allow restores of saved
wallpaper images among HVGA devices, among WVGA variants, and
among tablets; but skip restoring wallpapers across those
categories (where severe clipping or letterboxing would occur).
Bug 3261863
Change-Id: I75e75d6401d18f1df10d75796ee04e21d2302cfa
This is mostly refactoring, adding a new WallpaperManager class that takes care
of the old wallpaper APIs on Context, so we don't need to pollute Context with
various new wallpaper APIs as they are needed. Also adds the first little
definition of a wallpaper service, which is not yet used or useful.
