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support zip files with data descriptor lump #5

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support zip files with data descriptor lump #5

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13 changes: 12 additions & 1 deletion lowzip.c
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Original file line number Diff line number Diff line change
Expand Up @@ -874,7 +874,7 @@ lowzip_file *lowzip_locate_file(lowzip_state *st, int idx, const char *name) {
}

fi = (lowzip_file *) st->scratch;

fi->have_data_descriptor = lowzip_read2(st, lhdr_offset + 6) & 0x08;
fi->compression_method = lowzip_read2(st, lhdr_offset + 8);
fi->crc32 = lowzip_read4(st, lhdr_offset + 14);
fi->compressed_size = lowzip_read4(st, lhdr_offset + 18);
Expand Down Expand Up @@ -974,12 +974,14 @@ void lowzip_get_data(lowzip_state *st) {
unsigned int header_crc32;
unsigned int header_uncompressed_size;
unsigned int computed_crc32;
unsigned int header_have_data_descriptor;

st->have_error = 0;

fi = (lowzip_file *) st->scratch;
header_crc32 = fi->crc32;
header_uncompressed_size = fi->uncompressed_size;
header_have_data_descriptor = fi->have_data_descriptor;

if (fi->compression_method == LOWZIP_COMPRESSION_STORE) {
offset = fi->data_offset;
Expand Down Expand Up @@ -1008,6 +1010,15 @@ void lowzip_get_data(lowzip_state *st) {
goto fail;
}
computed_crc32 = lowzip_zip_crc32(st->output_start, st->output_next);

if (header_have_data_descriptor) {
if (lowzip_read4(st, st->read_offset) == 0x08074b50UL) {
header_crc32 = lowzip_read4(st, st->read_offset + 4);
} else {
header_crc32 = lowzip_read4(st, st->read_offset);
}
}

if (computed_crc32 != header_crc32) {
goto fail;
}
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2 changes: 2 additions & 0 deletions lowzip.h
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Original file line number Diff line number Diff line change
Expand Up @@ -69,6 +69,8 @@ typedef struct {
/* Offset to start of compressed data. */
unsigned int data_offset;

unsigned int have_data_descriptor;

/* Filename, truncated to 255 characters. ZIP filenames can be
* 65535 bytes long, but 255 is enough in practice.
*/
Expand Down