john-okeefe
46ae45ee92
Vendored the sevenzip package to eliminate dependency chain: - sevenzip -> go4.org -> 25+ Google/Cloud/telemetry packages Changes: - Added internal/sevenzip/ with full package source - Inlined go4.org/readerutil into multireaderat.go - Updated all internal imports to use bookhoard/internal/sevenzip - Preserved .cb7 comic archive support This reduces bloat by ~4.9 MB and removes unused telemetry dependencies while maintaining all functionality.
127 lines
2.5 KiB
Go
127 lines
2.5 KiB
Go
// Package aes7z implements the 7-zip AES decryption.
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package aes7z
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import (
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"bytes"
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"crypto/aes"
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"crypto/cipher"
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"errors"
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"fmt"
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"io"
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)
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var (
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errAlreadyClosed = errors.New("aes7z: already closed")
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errNeedOneReader = errors.New("aes7z: need exactly one reader")
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errInsufficientProperties = errors.New("aes7z: not enough properties")
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errNoPasswordSet = errors.New("aes7z: no password set")
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errUnsupportedMethod = errors.New("aes7z: unsupported compression method")
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)
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type readCloser struct {
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rc io.ReadCloser
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salt, iv []byte
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cycles int
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cbc cipher.BlockMode
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buf bytes.Buffer
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}
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func (rc *readCloser) Close() error {
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if rc.rc == nil {
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return errAlreadyClosed
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}
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if err := rc.rc.Close(); err != nil {
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return fmt.Errorf("aes7z: error closing: %w", err)
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}
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rc.rc = nil
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return nil
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}
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func (rc *readCloser) Password(p string) error {
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key, err := calculateKey(p, rc.cycles, rc.salt)
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if err != nil {
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return err
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}
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block, err := aes.NewCipher(key)
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if err != nil {
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return fmt.Errorf("aes7z: error creating cipher: %w", err)
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}
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rc.cbc = cipher.NewCBCDecrypter(block, rc.iv)
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return nil
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}
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func (rc *readCloser) Read(p []byte) (int, error) {
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if rc.rc == nil {
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return 0, errAlreadyClosed
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}
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if rc.cbc == nil {
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return 0, errNoPasswordSet
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}
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var block [aes.BlockSize]byte
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for rc.buf.Len() < len(p) {
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if _, err := io.ReadFull(rc.rc, block[:]); err != nil {
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if errors.Is(err, io.EOF) {
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break
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}
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return 0, fmt.Errorf("aes7z: error reading block: %w", err)
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}
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rc.cbc.CryptBlocks(block[:], block[:])
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_, _ = rc.buf.Write(block[:])
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}
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n, err := rc.buf.Read(p)
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if err != nil && !errors.Is(err, io.EOF) {
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err = fmt.Errorf("aes7z: error reading: %w", err)
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}
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return n, err
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}
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// NewReader returns a new AES-256-CBC & SHA-256 io.ReadCloser. The Password
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// method must be called before attempting to call Read so that the block
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// cipher is correctly initialised.
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func NewReader(p []byte, _ uint64, readers []io.ReadCloser) (io.ReadCloser, error) {
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if len(readers) != 1 {
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return nil, errNeedOneReader
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}
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// Need at least two bytes initially
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if len(p) < 2 {
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return nil, errInsufficientProperties
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}
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if p[0]&0xc0 == 0 {
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return nil, errUnsupportedMethod
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}
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rc := new(readCloser)
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salt := p[0]>>7&1 + p[1]>>4
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iv := p[0]>>6&1 + p[1]&0x0f
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if len(p) != int(2+salt+iv) {
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return nil, errInsufficientProperties
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}
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rc.salt = p[2 : 2+salt]
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rc.iv = make([]byte, aes.BlockSize)
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copy(rc.iv, p[2+salt:])
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rc.cycles = int(p[0] & 0x3f)
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rc.rc = readers[0]
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return rc, nil
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}
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