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50 lines
1.6 KiB
Go
50 lines
1.6 KiB
Go
/*
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* cache.go - Handles cache clearing and management.
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*
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* Copyright 2017 Google Inc.
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* Author: Joe Richey (joerichey@google.com)
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may not
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* use this file except in compliance with the License. You may obtain a copy of
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* the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations under
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* the License.
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*/
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package security
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import (
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"log"
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"os"
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"golang.org/x/sys/unix"
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)
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// DropFilesystemCache instructs the kernel to free the reclaimable inodes and
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// dentries. This has the effect of making encrypted directories whose keys are
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// not present no longer accessible. Requires root privileges.
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func DropFilesystemCache() error {
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// Dirty reclaimable inodes must be synced so that they will be freed.
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log.Print("syncing changes to filesystem")
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unix.Sync()
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// See: https://www.kernel.org/doc/Documentation/sysctl/vm.txt
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log.Print("freeing reclaimable inodes and dentries")
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file, err := os.OpenFile("/proc/sys/vm/drop_caches", os.O_WRONLY|os.O_SYNC, 0)
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if err != nil {
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return err
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}
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defer file.Close()
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// "2" just frees the reclaimable inodes and dentries. The associated
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// pages to these inodes will be freed. We do not need to free the
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// entire pagecache (as this will severely impact performance).
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_, err = file.WriteString("2")
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return err
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}
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