39 lines
801 B
Go
39 lines
801 B
Go
package decrypt
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import (
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"encoding/binary"
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"fmt"
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"golang.org/x/crypto/salsa20"
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"io"
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)
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type Decrypt struct {
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Key []byte
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}
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func (d *Decrypt) Decrypt(reader io.Reader, writer io.Writer) error {
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if len(d.Key) != 32 {
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return fmt.Errorf("key must be 32 bytes long")
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}
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blockNumber := 0
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for {
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nonceBytes := make([]byte, 24)
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binary.LittleEndian.PutUint64(nonceBytes, uint64(blockNumber))
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block := make([]byte, 256)
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_, err := reader.Read(block)
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if err == io.EOF {
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return nil
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}
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if err != nil {
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return fmt.Errorf("unable to read file: %v", err)
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}
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outBlock := make([]byte, 256)
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salsa20.XORKeyStream(outBlock, block, nonceBytes, (*[32]byte)(d.Key))
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blockNumber++
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_, err = writer.Write(outBlock)
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if err != nil {
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return fmt.Errorf("unable to write: %v", err)
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}
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}
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}
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