How do you take a cipher.StreamWriter and pass it to a io.Reader

[Justin C]

I have a encryption function that gives a  cipher.StreamWriter 

    writer := &cipher.StreamWriter{S: stream, W: outFile}

I am trying to upload it to using a library that has a function that is uploadFile that requires a IO.reader is there a way to pass the writer to the io.reader so the file is in crypted then uploaded?

    UploadFile(outputFileName, metadata, io.Reader)

My code looks like this

                writer := &cipher.StreamWriter{S: stream, W: outFile}

// Copy the input file to the output file, encrypting as we go.

metadata := make(map[string]string)

b2h.currentBucket.UploadFile(outputFileName, metadata, writer)

I get this error.

cannot use writer (type *cipher.StreamWriter) as type io.Reader in argument to b2h.currentBucket.UploadFile: *cipher.StreamWriter does not implement io.Reader (missing Read method)

I'm having a little trouble understanding how this is suppose to work together.

Does anyone have any ideas? 

Thank you!

[Ilya Kostarev]

Try to construct an io.Pipe maybe
    pReader, pWriter := io.Pipe()
    writer := &cipher.StreamWriter{S: stream, W: pWriter}
    UploadFile(outputFileName, metadata, pReader)
    writer.Write(src)

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[Justin C]

I think your on the right track I just can't get this to work. It seem like I'm missing something simple to do with GOs readers and writters. 

func (b2h *B2Handler) EncyptandUpload(iv []byte, fileName string, outputFileName string) {

key := []byte("example key 1234")

inFile, err := os.Open(fileName)

if err != nil {

panic(err)

}

defer inFile.Close()

block, err := aes.NewCipher(key)

if err != nil {

panic(err)

}

// If the key is unique for each ciphertext, then it's ok to use a zero

// IV.

//var iv [aes.BlockSize]byte

stream := cipher.NewOFB(block, iv[:])

// outFile, err := os.OpenFile(outputFileName, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)

// if err != nil {

// panic(err)

// }

// defer outFile.Close()

pReader, pWriter := io.Pipe()

writer := &cipher.StreamWriter{S: stream, W: pWriter}

// Copy the input file to the output file, encrypting as we go.

// if _, err := io.Copy(writer, inFile); err != nil {

// panic(err)

// }

writer.Write(inFile) // cannot use inFile.Read (type func([]byte) (int, error)) as type []byte in argument to writer.Write

metadata := make(map[string]string)

_, err3 := b2h.currentBucket.UploadFile(outputFileName, metadata, pReader)

if err3 != nil {

fmt.Println(err3.Error)

}

I'm still getting a error on reading the file into the writer.Write().  *cannot use inFile.Read (type func([]byte) (int, error)) as type []byte in argument to writer.Write* It seems like you should be able to write it and upload it but i might have to write it out to a temp file and then upload it. 

Here is the encyption example https://golang.org/pkg/crypto/cipher/#NewOFB

here is the library i am using to upload it https://github.com/kothar/go-backblaze

If that helps. 

[Ilya Kostarev]

You can  use io.TeeReader to connect them all. Also to simultaneously read from one file, encrypt, and write to another file on the fly you seems to need a bit of concurrency 

func (b2h *B2Handler) EncyptandUpload(iv []byte, fileName string, outputFileName string) {

key := []byte("example key 1234")

inFile, err := os.Open(fileName)

if err != nil {

panic(err)

}

defer inFile.Close()

block, err := aes.NewCipher(key)

if err != nil {

panic(err)

}

// If the key is unique for each ciphertext, then it's ok to use a zero

// IV.

//var iv [aes.BlockSize]byte

stream := cipher.NewOFB(block, iv[:])

// outFile, err := os.OpenFile(outputFileName, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)

// if err != nil {

// panic(err)

// }

// defer outFile.Close()

pReader, pWriter := io.Pipe()

writer := &cipher.StreamWriter{S: stream, W: pWriter}

// Copy the input file to the output file, encrypting as we go.

// if _, err := io.Copy(writer, inFile); err != nil {

// panic(err)

// }

//writer.Write(inFile) // cannot use inFile.Read (type func([]byte) (int, error)) as type []byte in argument to writer.Write

        teeReader := io.TeeReader(inFile, writer)  //construct TeeReader
        go ioutil.ReadAll(teeReader)               //use it concurrently, err check omitted for simplicity

        metadata := make(map[string]string)

_, err3 := b2h.currentBucket.UploadFile(outputFileName, metadata, pReader)

if err3 != nil {

fmt.Println(err3.Error)

}
or you can do sequentially allocating in-memory  buffers for data

in, err := ioutil.ReadAll(inFile)
        var buf bytes.Buffer
        writer := &cipher.StreamWriter{S: stream, W: buf}
        _, err = writer.Write(in)
        _, err3 := b2h.currentBucket.UploadFile(outputFileName, metadata, buf)