mirror of https://github.com/go-gitea/gitea.git
127 lines
3.0 KiB
Go
127 lines
3.0 KiB
Go
package rardecode
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import (
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"crypto/aes"
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"crypto/cipher"
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"io"
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)
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// cipherBlockReader implements Block Mode decryption of an io.Reader object.
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type cipherBlockReader struct {
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r io.Reader
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mode cipher.BlockMode
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inbuf []byte // input buffer for partial data block
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outbuf []byte // output buffer used when output slice < block size
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n int // bytes read from outbuf
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err error
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}
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// read reads and decrypts one or more input blocks into p.
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// len(p) must be >= cipher block size.
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func (cr *cipherBlockReader) read(p []byte) (n int, err error) {
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bs := cr.mode.BlockSize()
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// round p down to a multiple of the block size
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l := len(p) - len(p)%bs
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p = p[:l]
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l = len(cr.inbuf)
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if l > 0 {
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// copy any buffered input into p
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copy(p, cr.inbuf)
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cr.inbuf = cr.inbuf[:0]
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}
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// read data for at least one block
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n, err = io.ReadAtLeast(cr.r, p[l:], bs-l)
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n += l
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p = p[:n]
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l = n % bs
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// check if p is a multiple of the cipher block size
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if l > 0 {
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n -= l
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// save trailing partial block to process later
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cr.inbuf = append(cr.inbuf, p[n:]...)
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p = p[:n]
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}
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if err != nil {
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if err == io.ErrUnexpectedEOF || err == io.ErrShortBuffer {
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// ignore trailing bytes < block size length
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err = io.EOF
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}
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return 0, err
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}
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cr.mode.CryptBlocks(p, p) // decrypt block(s)
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return n, nil
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}
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// Read reads and decrypts data into p.
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// If the input is not a multiple of the cipher block size,
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// the trailing bytes will be ignored.
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func (cr *cipherBlockReader) Read(p []byte) (n int, err error) {
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for {
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if cr.n < len(cr.outbuf) {
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// return buffered output
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n = copy(p, cr.outbuf[cr.n:])
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cr.n += n
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return n, nil
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}
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if cr.err != nil {
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err = cr.err
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cr.err = nil
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return 0, err
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}
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if len(p) >= cap(cr.outbuf) {
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break
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}
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// p is not large enough to process a block, use outbuf instead
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n, cr.err = cr.read(cr.outbuf[:cap(cr.outbuf)])
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cr.outbuf = cr.outbuf[:n]
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cr.n = 0
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}
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// read blocks into p
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return cr.read(p)
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}
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// ReadByte returns the next decrypted byte.
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func (cr *cipherBlockReader) ReadByte() (byte, error) {
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for {
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if cr.n < len(cr.outbuf) {
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c := cr.outbuf[cr.n]
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cr.n++
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return c, nil
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}
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if cr.err != nil {
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err := cr.err
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cr.err = nil
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return 0, err
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}
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// refill outbuf
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var n int
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n, cr.err = cr.read(cr.outbuf[:cap(cr.outbuf)])
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cr.outbuf = cr.outbuf[:n]
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cr.n = 0
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}
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}
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// newCipherBlockReader returns a cipherBlockReader that decrypts the given io.Reader using
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// the provided block mode cipher.
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func newCipherBlockReader(r io.Reader, mode cipher.BlockMode) *cipherBlockReader {
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cr := &cipherBlockReader{r: r, mode: mode}
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cr.outbuf = make([]byte, 0, mode.BlockSize())
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cr.inbuf = make([]byte, 0, mode.BlockSize())
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return cr
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}
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// newAesDecryptReader returns a cipherBlockReader that decrypts input from a given io.Reader using AES.
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// It will panic if the provided key is invalid.
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func newAesDecryptReader(r io.Reader, key, iv []byte) *cipherBlockReader {
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block, err := aes.NewCipher(key)
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if err != nil {
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panic(err)
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}
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mode := cipher.NewCBCDecrypter(block, iv)
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return newCipherBlockReader(r, mode)
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}
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