69 lines
1.8 KiB
Go
69 lines
1.8 KiB
Go
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package s3crypto
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import (
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"io"
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)
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const (
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gcmKeySize = 32
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gcmNonceSize = 12
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)
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type gcmContentCipherBuilder struct {
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generator CipherDataGenerator
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}
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// AESGCMContentCipherBuilder returns a new encryption only mode structure with a specific cipher
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// for the master key
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func AESGCMContentCipherBuilder(generator CipherDataGenerator) ContentCipherBuilder {
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return gcmContentCipherBuilder{generator}
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}
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func (builder gcmContentCipherBuilder) ContentCipher() (ContentCipher, error) {
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cd, err := builder.generator.GenerateCipherData(gcmKeySize, gcmNonceSize)
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if err != nil {
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return nil, err
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}
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return newAESGCMContentCipher(cd)
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}
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func newAESGCMContentCipher(cd CipherData) (ContentCipher, error) {
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cd.CEKAlgorithm = AESGCMNoPadding
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cd.TagLength = "128"
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cipher, err := newAESGCM(cd)
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if err != nil {
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return nil, err
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}
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return &aesGCMContentCipher{
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CipherData: cd,
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Cipher: cipher,
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}, nil
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}
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// AESGCMContentCipher will use AES GCM for the main cipher.
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type aesGCMContentCipher struct {
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CipherData CipherData
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Cipher Cipher
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}
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// EncryptContents will generate a random key and iv and encrypt the data using cbc
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func (cc *aesGCMContentCipher) EncryptContents(src io.Reader) (io.Reader, error) {
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return cc.Cipher.Encrypt(src), nil
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}
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// DecryptContents will use the symmetric key provider to instantiate a new GCM cipher.
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// We grab a decrypt reader from gcm and wrap it in a CryptoReadCloser. The only error
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// expected here is when the key or iv is of invalid length.
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func (cc *aesGCMContentCipher) DecryptContents(src io.ReadCloser) (io.ReadCloser, error) {
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reader := cc.Cipher.Decrypt(src)
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return &CryptoReadCloser{Body: src, Decrypter: reader}, nil
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}
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// GetCipherData returns cipher data
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func (cc aesGCMContentCipher) GetCipherData() CipherData {
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return cc.CipherData
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}
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