mirror of https://github.com/mautrix/go.git
31 lines
1.1 KiB
Go
31 lines
1.1 KiB
Go
// Copyright (c) 2024 Sumner Evans
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//
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// This Source Code Form is subject to the terms of the Mozilla Public
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// License, v. 2.0. If a copy of the MPL was not distributed with this
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// file, You can obtain one at http://mozilla.org/MPL/2.0/.
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package pkcs7
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import "bytes"
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// Pad implements PKCS#7 padding as defined in [RFC2315]. It pads the plaintext
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// to the given blockSize in the range [1, 255]. This is normally used in
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// AES-CBC encryption.
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//
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// [RFC2315]: https://www.ietf.org/rfc/rfc2315.txt
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func Pad(plaintext []byte, blockSize int) []byte {
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padding := blockSize - len(plaintext)%blockSize
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return append(plaintext, bytes.Repeat([]byte{byte(padding)}, padding)...)
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}
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// Unpad implements PKCS#7 unpadding as defined in [RFC2315]. It unpads the
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// plaintext by reading the padding amount from the last byte of the plaintext.
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// This is normally used in AES-CBC decryption.
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//
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// [RFC2315]: https://www.ietf.org/rfc/rfc2315.txt
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func Unpad(plaintext []byte) []byte {
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length := len(plaintext)
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unpadding := int(plaintext[length-1])
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return plaintext[:length-unpadding]
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}
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