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Henrik RydgårdandClaude Opus 5
917cb1b0fc
KL4E is Sony's second compression scheme for ~PSP modules, alongside gzip: LZ77 tokens where every bit is arithmetic-coded, structurally close to LZMA. PPSSPP could detect it but not decode it, so any module packed with it failed to load at all - the loader reached the gzip path and bailed there. Which scheme a compressed module uses is now decided by the payload's own magic rather than assuming gzip. On a 6.61 flash0 dump this takes the kd/ modules that load from 126 to 129 of 129; libmp3.prx, libaac.prx and libmp4.prx were the ones affected, and libmp3.prx decompresses to exactly the elf_size its PRX header declares. Two bounds problems in the format are fixed rather than reproduced: the match copy is unchecked against the output buffer on real hardware, so a crafted stream can write up to 255 bytes past it, and a long enough distance code indexes copyDistProbs out of range. Input reads are bounded too - the format carries no length and trusts the stream to terminate itself. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
42 lines
1.9 KiB
C
42 lines
1.9 KiB
C
// Copyright (c) 2026- PPSSPP Project.
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, version 2.0 or later versions.
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License 2.0 for more details.
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// A copy of the GPL 2.0 should have been included with the program.
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// If not, see http://www.gnu.org/licenses/
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// Official git repository and contact information can be found at
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// https://github.com/hrydgard/ppsspp and http://www.ppsspp.org/.
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#pragma once
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#include <cstddef>
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#include "Common/CommonTypes.h"
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// KL4E / KL3E - Sony's LZ77-with-arithmetic-coding scheme for compressed PSP executables, the
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// alternative to gzip inside a ~PSP module. KL3E is the same bitstream with one constant changed.
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//
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// See docs/KL4E.md for the format.
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// Decompresses one KL4E/KL3E stream. `in` points at the five-byte stream header, i.e. *past* the
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// four-byte "KL4E"/"KL3E" magic. `inSize` bounds reads so a truncated file can't run off the end.
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//
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// Returns the number of bytes written, or a negative PSP error code:
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// SCE_KERNEL_ERROR_INVALID_SIZE (0x80000104) output didn't fit
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// SCE_KERNEL_ERROR_INVALID_FORMAT (0x80000108) stream is malformed
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//
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// If `end` is non-null it receives a pointer just past the last input byte consumed. (The PSP's
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// own routine reports the last byte consumed for stored streams and one past for compressed ones;
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// this is deliberately consistent instead, since nothing in PPSSPP depends on the quirk.)
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int DecompressKL4E(u8 *out, int outSize, const u8 *in, size_t inSize, const u8 **end, bool isKL3E);
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// True if the buffer starts with a "KL4E" or "KL3E" magic. Sets *isKL3E when it does.
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bool IsKL4EMagic(const u8 *data, size_t size, bool *isKL3E);
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