mirror of
https://github.com/Atmosphere-NX/Atmosphere-libs.git
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129 lines
4.8 KiB
C++
129 lines
4.8 KiB
C++
/*
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* Copyright (c) 2018-2020 Atmosphère-NX
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms and conditions of the GNU General Public License,
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* version 2, as published by the Free Software Foundation.
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*
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* This program is distributed in the hope it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#pragma once
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#include <vapours/common.hpp>
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#include <vapours/assert.hpp>
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#include <vapours/util.hpp>
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#include <vapours/crypto/impl/crypto_hash_function.hpp>
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namespace ams::crypto::impl {
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template<typename Hash> /* requires HashFunction<Hash> */
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class RsaOaepImpl {
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NON_COPYABLE(RsaOaepImpl);
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NON_MOVEABLE(RsaOaepImpl);
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public:
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static constexpr size_t HashSize = Hash::HashSize;
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private:
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static constexpr u8 HeadMagic = 0x00;
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private:
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static void ComputeHashWithPadding(void *dst, Hash *hash, const void *salt, size_t salt_size) {
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/* Initialize our buffer. */
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u8 buf[8 + HashSize];
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std::memset(buf, 0, 8);
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hash->GetHash(buf + 8, HashSize);
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ON_SCOPE_EXIT { ClearMemory(buf, sizeof(buf)); };
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/* Calculate our hash. */
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hash->Initialize();
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hash->Update(buf, sizeof(buf));
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hash->Update(salt, salt_size);
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hash->GetHash(dst, HashSize);
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}
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static void ApplyMGF1(u8 *dst, size_t dst_size, const void *src, size_t src_size) {
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u8 buf[HashSize];
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ON_SCOPE_EXIT { ClearMemory(buf, sizeof(buf)); };
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const size_t required_iters = (dst_size + HashSize - 1) / HashSize;
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for (size_t i = 0; i < required_iters; i++) {
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Hash hash;
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hash.Initialize();
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hash.Update(src, src_size);
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const u32 tmp = util::ConvertToBigEndian(static_cast<u32>(i));
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hash.Update(std::addressof(tmp), sizeof(tmp));
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hash.GetHash(buf, HashSize);
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const size_t start = HashSize * i;
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const size_t end = std::min(dst_size, start + HashSize);
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for (size_t j = start; j < end; j++) {
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dst[j] ^= buf[j - start];
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}
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}
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}
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public:
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RsaOaepImpl() { /* ... */ }
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size_t Decode(void *dst, size_t dst_size, const void *label_digest, size_t label_digest_size, u8 *buf, size_t buf_size) {
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/* Check our preconditions. */
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AMS_ABORT_UNLESS(dst_size > 0);
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AMS_ABORT_UNLESS(buf_size >= 2 * HashSize + 3);
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AMS_ABORT_UNLESS(label_digest_size == HashSize);
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/* Validate sanity byte. */
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bool is_valid = buf[0] == HeadMagic;
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/* Decrypt seed and masked db. */
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size_t db_len = buf_size - HashSize - 1;
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u8 *seed = buf + 1;
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u8 *db = seed + HashSize;
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ApplyMGF1(seed, HashSize, db, db_len);
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ApplyMGF1(db, db_len, seed, HashSize);
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/* Check the label digest. */
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is_valid &= IsSameBytes(label_digest, db, HashSize);
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/* Skip past the label digest. */
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db += HashSize;
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db_len -= HashSize;
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/* Verify that DB is of the form 0000...0001 < message > */
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s32 msg_ofs = 0;
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{
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int looking_for_one = 1;
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int invalid_db_padding = 0;
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int is_zero;
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int is_one;
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for (size_t i = 0; i < db_len; /* ... */) {
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is_zero = (db[i] == 0);
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is_one = (db[i] == 1);
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msg_ofs += (looking_for_one & is_one) * (static_cast<s32>(++i));
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looking_for_one &= ~is_one;
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invalid_db_padding |= (looking_for_one & ~is_zero);
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}
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is_valid &= (invalid_db_padding == 0);
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}
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/* If we're invalid, return zero size. */
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const size_t valid_msg_size = db_len - msg_ofs;
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const size_t msg_size = std::min(dst_size, static_cast<size_t>(is_valid) * valid_msg_size);
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/* Copy to output. */
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std::memcpy(dst, db + msg_ofs, msg_size);
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/* Return copied size. */
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return msg_size;
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}
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};
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}
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