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52 lines
1.6 KiB
52 lines
1.6 KiB
3 years ago
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package ige
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import (
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"crypto/cipher"
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"errors"
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)
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// ErrInvalidIV is displayed as the panic message if the initialization vector
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// passed to NewIGEEncrypter or NewIGEDecrypter doesn't fulfill the length
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// requirements for IGE.
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//
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// IGE uses a two step xor process, so the first initialization vector is the
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// first half, and the second initialization vector is the second half. This
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// requires the initialization vector to be twice as long as the block size.
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var ErrInvalidIV = errors.New("iv length must be: (block size * 2)")
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// IGE satisfies the cipher.BlockMode interface from the crypto/cipher package.
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type IGE interface {
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// BlockSize returns the mode's block size.
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BlockSize() int
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// CryptBlocks encrypts or decrypts a number of blocks based on the
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// underlying cipher.Block passed to NewIGEEncrypter or NewIGEDecrypter
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// (usually from crypto/aes).
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CryptBlocks(dst, src []byte)
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}
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type ige struct {
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block cipher.Block
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iv []byte
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}
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func newIGE(b cipher.Block, iv []byte) *ige {
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i := &ige{b, make([]byte, len(iv))}
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copy(i.iv, iv)
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return i
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}
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func checkIV(b cipher.Block, iv []byte) error {
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// the initialization vector needs to contain b.Blocksize()*2 bytes because
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// ige uses a two step xor process, and iv[:16] corresponds to the first iv
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// while iv[16:] corresponds to the second iv
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//
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// the original ige paper described the first iv as a random block and the
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// second iv as its encrypted counterpart, however, we're copying the
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// openssl implementation and therefore both ivs are supplied by the user
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if len(iv) != b.BlockSize()*2 {
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return ErrInvalidIV
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}
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return nil
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}
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