63 lines
2.0 KiB
Go
63 lines
2.0 KiB
Go
package fusefrontend_reverse
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import (
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"bytes"
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"io"
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"sync"
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"github.com/rfjakob/gocryptfs/v2/internal/contentenc"
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"github.com/rfjakob/gocryptfs/v2/internal/pathiv"
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"github.com/rfjakob/gocryptfs/v2/internal/tlog"
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)
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var inodeTable sync.Map
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// encryptBlocks - encrypt "plaintext" into a number of ciphertext blocks.
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// "plaintext" must already be block-aligned.
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func (rf *File) encryptBlocks(plaintext []byte, firstBlockNo uint64, fileID []byte, block0IV []byte) []byte {
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inBuf := bytes.NewBuffer(plaintext)
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var outBuf bytes.Buffer
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bs := int(rf.contentEnc.PlainBS())
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for blockNo := firstBlockNo; inBuf.Len() > 0; blockNo++ {
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inBlock := inBuf.Next(bs)
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iv := pathiv.BlockIV(block0IV, blockNo)
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outBlock := rf.contentEnc.EncryptBlockNonce(inBlock, blockNo, fileID, iv)
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outBuf.Write(outBlock)
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}
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return outBuf.Bytes()
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}
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// readBackingFile: read from the backing plaintext file, encrypt it, return the
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// ciphertext.
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// "off" ... ciphertext offset (must be >= HEADER_LEN)
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// "length" ... ciphertext length
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func (f *File) readBackingFile(off uint64, length uint64) (out []byte, err error) {
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blocks := f.contentEnc.ExplodeCipherRange(off, length)
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// Read the backing plaintext in one go
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alignedOffset, alignedLength := contentenc.JointPlaintextRange(blocks)
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plaintext := make([]byte, int(alignedLength))
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n, err := f.fd.ReadAt(plaintext, int64(alignedOffset))
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if err != nil && err != io.EOF {
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tlog.Warn.Printf("readBackingFile: ReadAt: %s", err.Error())
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return nil, err
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}
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// Truncate buffer down to actually read bytes
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plaintext = plaintext[0:n]
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// Encrypt blocks
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ciphertext := f.encryptBlocks(plaintext, blocks[0].BlockNo, f.header.ID, f.block0IV)
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// Crop down to the relevant part
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lenHave := len(ciphertext)
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skip := blocks[0].Skip
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endWant := int(skip + length)
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if lenHave > endWant {
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out = ciphertext[skip:endWant]
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} else if lenHave > int(skip) {
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out = ciphertext[skip:lenHave]
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} // else: out stays empty, file was smaller than the requested offset
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return out, nil
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}
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