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WIP: fix encrypt-on-recv

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fixes https://github.com/zrepl/zrepl/issues/504
This commit is contained in:
Christian Schwarz 2021-08-07 19:12:52 +02:00
parent bcfcd7a134
commit 6ccaf3b902
1 changed files with 34 additions and 0 deletions
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34
zfs/placeholder.go
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@ -90,6 +90,40 @@ func ZFSCreatePlaceholderFilesystem(ctx context.Context, fs *DatasetPath, parent
"-o", fmt.Sprintf("%s=%s", PlaceholderPropertyName, placeholderPropertyOn),
"-o", "mountpoint=none",
}
// xxx handle encryption not supported
props, err := zfsGet(ctx, parent.ToString(), []string{"keystatus"}, SourceAny)
if err != nil {
return errors.Wrap(err, "cannot determine key status")
}
keystatus := props.Get("keystatus") // xxx ability to distringuish `-` from ``
if keystatus == "" {
// parent is unencrypted => placeholder inherits encryption
} else if keystatus == "available" {
// parent is encrypted but since the key is loaded we can create an encrypted placeholder dataset
// without `-o encryption=off`
} else if keystatus == "unavailable" {
// parent is encrypted but keys are not loaded, either because
// 1) it's a send-encrypted dataset, or because
// 2) the user forgot to zfs load-key the root_fs or above
// In both cases we can't create an encrypted placeholder dataset.
// In case 1), we want to create an unencrypted placeholder through `-o encryption=off`.
// In case 2), `-o encryption=off` is harmful security-wise because it breaks the encrypt-on-receiver use case (https://github.com/zrepl/zrepl/issues/504)
// I.e., all children of the placeholder won't be encrypted because they inherit encryption=off
//
// => we could attempt to distinguish the cases by being more context sensitive
// (i.e., check whether the encryption root is root_fs or a parent thereof)
// However, that's always going to be imprecise, and a wrong decision there is harmful security-wise.
//
// => thus the safe choice is to never use `-o encryption=off` by default
// only if we know for sure that the stream is encrypted should we create placeholders with `-o encryption=off`
// => this knowledge can be achieved through one of the following means:
// a) have the sender indicate it to us in the RPC request (it's ok to trust them in this particular case since lying only hurts _their_ data's confidentiality)
// b) have the user acknowledge it in the receiver config
} else {
return errors.Errorf("unknown keystatus value %q for dataset %q", keystatus, parent.ToString())
}
if parentEncrypted, err := ZFSGetEncryptionEnabled(ctx, parent.ToString()); err != nil {
return errors.Wrap(err, "cannot determine encryption support")
} else if parentEncrypted {