From 43bc679d0571dbfd344a1535e75b9de7961b54a9 Mon Sep 17 00:00:00 2001 From: LemonBoy Date: Sat, 1 Jun 2024 11:48:07 +0200 Subject: [PATCH] Support Zip archives not starting at zero offset Zip archives are usually read from the back to the front, making it possible to append them to other files (e.g. executables) in order to provide some kind of embedded filesystem. We can actually extract the start of the archive by looking at the central directory offset, by comparing the specified and the actual file offset. The Zip64 format adds another challenge as the EOCD locator specifies the offset to the EOCD starting from the beginning of the archive. Such relative offset cannot be directly used for archives not starting at position zero, hence the addition of another step that tries to locate the 64bit EOCD right before the EOCD locator. The added overhead is pretty small (and could be made smaller by reading both the presumed EOCD and EOCD locator at once) and works pretty well for 90% of the archives I've tested it with, if that heuristic fails the old behaviour is preserved. --- miniz_zip.c | 77 ++++++++++++++++++++++++++++++++++++++++++++--------- 1 file changed, 65 insertions(+), 12 deletions(-) diff --git a/miniz_zip.c b/miniz_zip.c index 8f52b4a..399972f 100644 --- a/miniz_zip.c +++ b/miniz_zip.c @@ -647,10 +647,23 @@ static int mz_stat64(const char *path, struct __stat64 *buffer) return MZ_TRUE; } + static mz_bool mz_zip_reader_eocd64_valid(mz_zip_archive *pZip, uint64_t offset, uint8_t *buf) + { + if (pZip->m_pRead(pZip->m_pIO_opaque, offset, buf, MZ_ZIP64_END_OF_CENTRAL_DIR_HEADER_SIZE) == MZ_ZIP64_END_OF_CENTRAL_DIR_HEADER_SIZE) + { + if (MZ_READ_LE32(buf + MZ_ZIP64_ECDH_SIG_OFS) == MZ_ZIP64_END_OF_CENTRAL_DIR_HEADER_SIG) + { + return MZ_TRUE; + } + } + + return MZ_FALSE; + } + static mz_bool mz_zip_reader_read_central_dir(mz_zip_archive *pZip, mz_uint flags) { mz_uint cdir_size = 0, cdir_entries_on_this_disk = 0, num_this_disk = 0, cdir_disk_index = 0; - mz_uint64 cdir_ofs = 0; + mz_uint64 cdir_ofs = 0, eocd_ofs = 0, archive_ofs = 0; mz_int64 cur_file_ofs = 0; const mz_uint8 *p; @@ -672,6 +685,7 @@ static int mz_stat64(const char *path, struct __stat64 *buffer) if (!mz_zip_reader_locate_header_sig(pZip, MZ_ZIP_END_OF_CENTRAL_DIR_HEADER_SIG, MZ_ZIP_END_OF_CENTRAL_DIR_HEADER_SIZE, &cur_file_ofs)) return mz_zip_set_error(pZip, MZ_ZIP_FAILED_FINDING_CENTRAL_DIR); + eocd_ofs = cur_file_ofs; /* Read and verify the end of central directory record. */ if (pZip->m_pRead(pZip->m_pIO_opaque, cur_file_ofs, pBuf, MZ_ZIP_END_OF_CENTRAL_DIR_HEADER_SIZE) != MZ_ZIP_END_OF_CENTRAL_DIR_HEADER_SIZE) return mz_zip_set_error(pZip, MZ_ZIP_FILE_READ_FAILED); @@ -685,21 +699,40 @@ static int mz_stat64(const char *path, struct __stat64 *buffer) { if (MZ_READ_LE32(pZip64_locator + MZ_ZIP64_ECDL_SIG_OFS) == MZ_ZIP64_END_OF_CENTRAL_DIR_LOCATOR_SIG) { - zip64_end_of_central_dir_ofs = MZ_READ_LE64(pZip64_locator + MZ_ZIP64_ECDL_REL_OFS_TO_ZIP64_ECDR_OFS); - if (zip64_end_of_central_dir_ofs > (pZip->m_archive_size - MZ_ZIP64_END_OF_CENTRAL_DIR_HEADER_SIZE)) - return mz_zip_set_error(pZip, MZ_ZIP_NOT_AN_ARCHIVE); - - if (pZip->m_pRead(pZip->m_pIO_opaque, zip64_end_of_central_dir_ofs, pZip64_end_of_central_dir, MZ_ZIP64_END_OF_CENTRAL_DIR_HEADER_SIZE) == MZ_ZIP64_END_OF_CENTRAL_DIR_HEADER_SIZE) - { - if (MZ_READ_LE32(pZip64_end_of_central_dir + MZ_ZIP64_ECDH_SIG_OFS) == MZ_ZIP64_END_OF_CENTRAL_DIR_HEADER_SIG) - { - pZip->m_pState->m_zip64 = MZ_TRUE; - } - } + pZip->m_pState->m_zip64 = MZ_TRUE; } } } + if (pZip->m_pState->m_zip64) + { + /* Try locating the EOCD64 right before the EOCD64 locator. This works even + * when the effective start of the zip header is not yet known. */ + if (cur_file_ofs < MZ_ZIP64_END_OF_CENTRAL_DIR_LOCATOR_SIZE + + MZ_ZIP64_END_OF_CENTRAL_DIR_HEADER_SIZE) + return mz_zip_set_error(pZip, MZ_ZIP_NOT_AN_ARCHIVE); + + zip64_end_of_central_dir_ofs = cur_file_ofs - + MZ_ZIP64_END_OF_CENTRAL_DIR_LOCATOR_SIZE - + MZ_ZIP64_END_OF_CENTRAL_DIR_HEADER_SIZE; + + if (!mz_zip_reader_eocd64_valid(pZip, zip64_end_of_central_dir_ofs, + pZip64_end_of_central_dir)) + { + /* That failed, try reading where the locator tells us to. */ + zip64_end_of_central_dir_ofs = MZ_READ_LE64( + pZip64_locator + MZ_ZIP64_ECDL_REL_OFS_TO_ZIP64_ECDR_OFS); + + if (zip64_end_of_central_dir_ofs > + (pZip->m_archive_size - MZ_ZIP64_END_OF_CENTRAL_DIR_HEADER_SIZE)) + return mz_zip_set_error(pZip, MZ_ZIP_NOT_AN_ARCHIVE); + + if (!mz_zip_reader_eocd64_valid(pZip, zip64_end_of_central_dir_ofs, + pZip64_end_of_central_dir)) + return mz_zip_set_error(pZip, MZ_ZIP_NOT_AN_ARCHIVE); + } + } + pZip->m_total_files = MZ_READ_LE16(pBuf + MZ_ZIP_ECDH_CDIR_TOTAL_ENTRIES_OFS); cdir_entries_on_this_disk = MZ_READ_LE16(pBuf + MZ_ZIP_ECDH_CDIR_NUM_ENTRIES_ON_DISK_OFS); num_this_disk = MZ_READ_LE16(pBuf + MZ_ZIP_ECDH_NUM_THIS_DISK_OFS); @@ -757,6 +790,26 @@ static int mz_stat64(const char *path, struct __stat64 *buffer) if ((cdir_ofs + (mz_uint64)cdir_size) > pZip->m_archive_size) return mz_zip_set_error(pZip, MZ_ZIP_INVALID_HEADER_OR_CORRUPTED); + /* The end of central dir follows the central dir, unless the zip file has + * some trailing data (e.g. it is appended to an executable file). */ + archive_ofs = eocd_ofs - (cdir_ofs + cdir_size); + if (pZip->m_pState->m_zip64) + { + if (archive_ofs < MZ_ZIP64_END_OF_CENTRAL_DIR_HEADER_SIZE + + MZ_ZIP64_END_OF_CENTRAL_DIR_LOCATOR_SIZE) + return mz_zip_set_error(pZip, MZ_ZIP_INVALID_HEADER_OR_CORRUPTED); + + archive_ofs -= MZ_ZIP64_END_OF_CENTRAL_DIR_HEADER_SIZE + + MZ_ZIP64_END_OF_CENTRAL_DIR_LOCATOR_SIZE; + } + + /* Update the archive start position, but only if not specified. */ + if (pZip->m_pState->m_file_archive_start_ofs == 0) + { + pZip->m_pState->m_file_archive_start_ofs = archive_ofs; + pZip->m_archive_size -= archive_ofs; + } + pZip->m_central_directory_file_ofs = cdir_ofs; if (pZip->m_total_files)