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We've steered users away from QCOW/QCOW2 encryption for a while, because it's a flawed design (commit136cd19Describe flaws in qcow/qcow2 encryption in the docs). In addition to flawed crypto, we have comically bad usability, and plain old bugs. Let me show you. = Example images = I'm going to use a raw image as backing file, and two QCOW2 images, one encrypted, and one not: $ qemu-img create -f raw backing.img 4m Formatting 'backing.img', fmt=raw size=4194304 $ qemu-img create -f qcow2 -o encryption,backing_file=backing.img,backing_fmt=raw geheim.qcow2 4m Formatting 'geheim.qcow2', fmt=qcow2 size=4194304 backing_file='backing.img' backing_fmt='raw' encryption=on cluster_size=65536 lazy_refcounts=off $ qemu-img create -f qcow2 -o backing_file=backing.img,backing_fmt=raw normal.qcow2 4m Formatting 'normal.qcow2', fmt=qcow2 size=4194304 backing_file='backing.img' backing_fmt='raw' encryption=off cluster_size=65536 lazy_refcounts=off = Usability issues = == Confusing startup == When no image is encrypted, and you don't give -S, QEMU starts the guest immediately: $ qemu-system-x86_64 -nodefaults -display none -monitor stdio normal.qcow2 QEMU 2.2.50 monitor - type 'help' for more information (qemu) info status VM status: running But as soon as there's an encrypted image in play, the guest is *not* started, with no notification whatsoever: $ qemu-system-x86_64 -nodefaults -display none -monitor stdio geheim.qcow2 QEMU 2.2.50 monitor - type 'help' for more information (qemu) info status VM status: paused (prelaunch) If the user figured out that he needs to type "cont" to enter his keys, the confusion enters the next level: "cont" asks for at most *one* key. If more are needed, it then silently does nothing. The user has to type "cont" once per encrypted image: $ qemu-system-x86_64 -nodefaults -display none -monitor stdio -drive if=none,file=geheim.qcow2 -drive if=none,file=geheim.qcow2 QEMU 2.2.50 monitor - type 'help' for more information (qemu) info status VM status: paused (prelaunch) (qemu) c none0 (geheim.qcow2) is encrypted. Password: ****** (qemu) info status VM status: paused (prelaunch) (qemu) c none1 (geheim.qcow2) is encrypted. Password: ****** (qemu) info status VM status: running == Incorrect passwords not caught == All existing encryption schemes give you the GIGO treatment: garbage password in, garbage data out. Guests usually refuse to mount garbage, but other usage is prone to data loss. == Need to stop the guest to add an encrypted image == $ qemu-system-x86_64 -nodefaults -display none -monitor stdio QEMU 2.2.50 monitor - type 'help' for more information (qemu) info status VM status: running (qemu) drive_add "" if=none,file=geheim.qcow2 Guest must be stopped for opening of encrypted image (qemu) stop (qemu) drive_add "" if=none,file=geheim.qcow2 OK Commitc3adb58added this restriction. Before, we could expose images lacking an encryption key to guests, with potentially catastrophic results. See also "Use without key is not always caught". = Bugs = == Use without key is not always caught == Encrypted images can be in an intermediate state "opened, but no key". The weird startup behavior and the need to stop the guest are there to ensure the guest isn't exposed to that state. But other things still are! * drive_backup $ qemu-system-x86_64 -nodefaults -display none -monitor stdio geheim.qcow2 QEMU 2.2.50 monitor - type 'help' for more information (qemu) drive_backup -f ide0-hd0 out.img raw Formatting 'out.img', fmt=raw size=4194304 I guess this writes encrypted data to raw image out.img. Good luck with figuring out how to decrypt that again. * commit $ qemu-system-x86_64 -nodefaults -display none -monitor stdio geheim.qcow2 QEMU 2.2.50 monitor - type 'help' for more information (qemu) commit ide0-hd0 I guess this writes encrypted data into the unencrypted raw backing image, effectively destroying it. == QMP device_add of usb-storage fails when it shouldn't == When the image is encrypted, device_add creates the device, defers actually attaching it to when the key becomes available, then fails. This is wrong. device_add must either create the device and succeed, or do nothing and fail. $ qemu-system-x86_64 -nodefaults -display none -usb -qmp stdio -drive if=none,id=foo,file=geheim.qcow2 {"QMP": {"version": {"qemu": {"micro": 50, "minor": 2, "major": 2}, "package": ""}, "capabilities": []}} { "execute": "qmp_capabilities" } {"return": {}} { "execute": "device_add", "arguments": { "driver": "usb-storage", "id": "bar", "drive": "foo" } } {"error": {"class": "DeviceEncrypted", "desc": "'foo' (geheim.qcow2) is encrypted"}} {"execute":"device_del","arguments": { "id": "bar" } } {"timestamp": {"seconds": 1426003440, "microseconds": 237181}, "event": "DEVICE_DELETED", "data": {"path": "/machine/peripheral/bar/bar.0/legacy[0]"}} {"timestamp": {"seconds": 1426003440, "microseconds": 238231}, "event": "DEVICE_DELETED", "data": {"device": "bar", "path": "/machine/peripheral/bar"}} {"return": {}} This stuff is worse than useless, it's a trap for users. If people become sufficiently interested in encrypted images to contribute a cryptographically sane implementation for QCOW2 (or whatever other format), then rewriting the necessary support around it from scratch will likely be easier and yield better results than fixing up the existing mess. Let's deprecate the mess now, drop it after a grace period, and move on. Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
98 lines
4.8 KiB
Plaintext
98 lines
4.8 KiB
Plaintext
QA output created by 087
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Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728
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=== Missing ID ===
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Testing:
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QMP_VERSION
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{"return": {}}
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{"error": {"class": "GenericError", "desc": "Block device needs an ID"}}
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{"return": {}}
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{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "SHUTDOWN"}
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{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "ide1-cd0", "tray-open": true}}
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{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "floppy0", "tray-open": true}}
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=== Duplicate ID ===
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Testing:
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QMP_VERSION
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{"return": {}}
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{"return": {}}
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{"error": {"class": "GenericError", "desc": "Device with id 'disk' already exists"}}
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{"error": {"class": "GenericError", "desc": "Device name 'test-node' conflicts with an existing node name"}}
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{"error": {"class": "GenericError", "desc": "node-name=disk is conflicting with a device id"}}
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{"error": {"class": "GenericError", "desc": "Duplicate node name"}}
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{"error": {"class": "GenericError", "desc": "node-name=disk3 is conflicting with a device id"}}
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{"return": {}}
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{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "SHUTDOWN"}
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{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "ide1-cd0", "tray-open": true}}
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{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "floppy0", "tray-open": true}}
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=== aio=native without O_DIRECT ===
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Testing:
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QMP_VERSION
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{"return": {}}
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{"error": {"class": "GenericError", "desc": "aio=native requires cache.direct=true"}}
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{"return": {}}
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{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "SHUTDOWN"}
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{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "ide1-cd0", "tray-open": true}}
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{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "floppy0", "tray-open": true}}
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=== Encrypted image ===
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qemu-img: Encrypted images are deprecated
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Support for them will be removed in a future release.
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You can use 'qemu-img convert' to convert your image to an unencrypted one.
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qemu-img: Encrypted images are deprecated
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Support for them will be removed in a future release.
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You can use 'qemu-img convert' to convert your image to an unencrypted one.
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Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 encryption=on
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Testing: -S
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QMP_VERSION
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{"return": {}}
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Encrypted images are deprecated
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Support for them will be removed in a future release.
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You can use 'qemu-img convert' to convert your image to an unencrypted one.
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{"error": {"class": "GenericError", "desc": "blockdev-add doesn't support encrypted devices"}}
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{"return": {}}
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{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "SHUTDOWN"}
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{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "ide1-cd0", "tray-open": true}}
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{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "floppy0", "tray-open": true}}
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Testing:
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QMP_VERSION
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{"return": {}}
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Encrypted images are deprecated
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Support for them will be removed in a future release.
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You can use 'qemu-img convert' to convert your image to an unencrypted one.
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{"error": {"class": "GenericError", "desc": "Guest must be stopped for opening of encrypted image"}}
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{"return": {}}
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{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "SHUTDOWN"}
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{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "ide1-cd0", "tray-open": true}}
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{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "floppy0", "tray-open": true}}
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=== Missing driver ===
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qemu-img: Encrypted images are deprecated
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Support for them will be removed in a future release.
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You can use 'qemu-img convert' to convert your image to an unencrypted one.
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qemu-img: Encrypted images are deprecated
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Support for them will be removed in a future release.
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You can use 'qemu-img convert' to convert your image to an unencrypted one.
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Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 encryption=on
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Testing: -S
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QMP_VERSION
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{"return": {}}
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{"error": {"class": "GenericError", "desc": "Invalid parameter type for 'driver', expected: string"}}
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{"return": {}}
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{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "SHUTDOWN"}
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{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "ide1-cd0", "tray-open": true}}
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{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "floppy0", "tray-open": true}}
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*** done
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