mirror of
https://github.com/Atmosphere-NX/Atmosphere.git
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122 lines
4.3 KiB
C++
122 lines
4.3 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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#include <exosphere.hpp>
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#include "se_execute.hpp"
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namespace ams::se {
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/* NOTE: This implementation is mostly copy/pasted from crypto::impl::RsaOaepImpl. */
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namespace {
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constexpr inline size_t HashSize = sizeof(Sha256Hash);
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constexpr inline u8 HeadMagic = 0x00;
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void ApplyMGF1(u8 *dst, size_t dst_size, const void *src, size_t src_size) {
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/* Check our pre-conditions. */
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AMS_ABORT_UNLESS(src_size <= RsaSize - (1 + HashSize));
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/* Create a buffer. */
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util::AlignedBuffer<hw::DataCacheLineSize, RsaSize - (1 + HashSize) + sizeof(u32)> buf;
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u32 counter = 0;
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while (dst_size > 0) {
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/* Setup the current hash buffer. */
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const size_t cur_size = std::min(HashSize, dst_size);
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std::memcpy(static_cast<u8 *>(buf), src, src_size);
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{
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u32 counter_be;
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util::StoreBigEndian(std::addressof(counter_be), counter++);
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std::memcpy(static_cast<u8 *>(buf) + src_size, std::addressof(counter_be), sizeof(counter_be));
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}
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/* Ensure se sees correct data. */
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hw::FlushDataCache(buf, src_size + sizeof(u32));
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hw::DataSynchronizationBarrierInnerShareable();
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/* Calculate the hash. */
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Sha256Hash hash;
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se::CalculateSha256(std::addressof(hash), buf, src_size + sizeof(u32));
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/* Mask the current output. */
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const u8 *mask = hash.bytes;
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for (size_t i = 0; i < cur_size; ++i) {
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*(dst++) ^= *(mask++);
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}
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/* Advance. */
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dst_size -= cur_size;
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}
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}
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}
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size_t DecodeRsaOaepSha256(void *dst, size_t dst_size, void *src, size_t src_size, const void *label_digest, size_t label_digest_size) {
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/* Check our preconditions. */
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AMS_ABORT_UNLESS(src_size == RsaSize);
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AMS_ABORT_UNLESS(label_digest_size == HashSize);
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/* Get a byte-readable copy of the input. */
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u8 *buf = static_cast<u8 *>(src);
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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 = src_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 &= crypto::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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