84 lines
3 KiB
C++
84 lines
3 KiB
C++
/*
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* Copyright (c) 2023, stelar7 <dudedbz@gmail.com>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/Math.h>
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#include <LibCrypto/BigInt/UnsignedBigInteger.h>
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namespace Crypto::Hash {
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// https://www.rfc-editor.org/rfc/rfc2898#section-5.2
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class PBKDF2 {
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public:
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template<typename PRF>
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static ErrorOr<Bytes> derive_key(ReadonlyBytes password, ReadonlyBytes salt, u32 iterations, u32 key_length_bytes)
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requires requires(PRF t) {
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t.digest_size();
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}
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{
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PRF prf(password);
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// Note: hLen denotes the length in octets of the pseudorandom function output
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u32 h_len = prf.digest_size();
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// 1. If dkLen > (2^32 - 1) * hLen, output "derived key too long" and stop.
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if (key_length_bytes > (AK::pow(2.0, 32.0) - 1) * h_len)
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return Error::from_string_view("derived key too long"sv);
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// 2 . Let l be the number of hLen-octet blocks in the derived key rounding up,
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// and let r be the number of octets in the last block
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u32 l = AK::ceil_div(key_length_bytes, h_len);
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u32 r = key_length_bytes - (l - 1) * h_len;
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// 3. For each block of the derived key apply the function F defined
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// below to the password P, the salt S, the iteration count c, and
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// the block index to compute the block:
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ByteBuffer ui = TRY(ByteBuffer::create_zeroed(h_len));
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ByteBuffer ti = TRY(ByteBuffer::create_zeroed(h_len));
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ByteBuffer key = TRY(ByteBuffer::create_zeroed(key_length_bytes));
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// T_i = F (P, S, c, i)
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u8 iteration_bytes[4];
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for (u32 i = 1; i <= l; i++) {
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iteration_bytes[3] = i;
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iteration_bytes[2] = ((i >> 8) & 0xff);
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iteration_bytes[1] = ((i >> 16) & 0xff);
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iteration_bytes[0] = ((i >> 24) & 0xff);
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prf.update(salt);
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prf.update(ReadonlyBytes { iteration_bytes, 4 });
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auto digest = prf.digest();
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ui.overwrite(0, digest.immutable_data(), h_len);
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ti.overwrite(0, digest.immutable_data(), h_len);
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// U_1 = PRF (P, S || INT (i))
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// U_j = PRF (P, U_{j-1})
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// F (P, S, c, i) = U_1 \xor U_2 \xor ... \xor U_c
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for (u32 j = 2; j <= iterations; j++) {
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prf.update(ui.bytes());
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auto digest_inner = prf.digest();
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ui.overwrite(0, digest_inner.immutable_data(), h_len);
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UnsignedBigInteger ti_temp = UnsignedBigInteger::import_data(ti.data(), ti.size());
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UnsignedBigInteger ui_temp = UnsignedBigInteger::import_data(ui.data(), ui.size());
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UnsignedBigInteger r_temp = ti_temp.bitwise_xor(ui_temp);
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r_temp.export_data(ti.bytes());
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}
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// 4. Concatenate the blocks and extract the first dkLen octets to produce a derived key DK:
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key.overwrite((i - 1) * h_len, ti.data(), i == l ? r : h_len);
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}
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// 5. Output the derived key DK
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return key;
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}
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};
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}
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