From 4ad4b34206c0ee3f245bc0be92d79d9b33a32ddc Mon Sep 17 00:00:00 2001 From: Peter Wu Date: Mon, 5 Jan 2015 18:00:29 +0100 Subject: block/dmg: fix sector data offset calculation This patch addresses two issues: - The data fork offset was not taken into account, resulting in failure to read an InstallESD.dmg file (5164763151 bytes) which had a non-zero DataForkOffset field. - The offset of the previous block ("partition") was unconditionally added to the current block because older files would start the input offset of a new block at zero. Newer files (including vlc-2.1.5.dmg, tuxpaint-0.9.15-macosx.dmg and OS X Yosemite [MAS].dmg) failed in reads because these files have chunk offsets, relative to the begin of a data fork. Now the data offset of the mish is taken into account. While we could check that the data_offset is within the data fork, let's not do that here as it would only result in parse failures on invalid files (rather than gracefully handling such bad files). dmg_read will error out if the offset is incorrect. Signed-off-by: Peter Wu --- block/dmg.c | 26 ++++++++++++++++++++------ 1 file changed, 20 insertions(+), 6 deletions(-) diff --git a/block/dmg.c b/block/dmg.c index 57feb1baf2..130efac018 100644 --- a/block/dmg.c +++ b/block/dmg.c @@ -188,7 +188,7 @@ static int64_t dmg_find_koly_offset(BlockDriverState *file_bs, Error **errp) typedef struct DmgHeaderState { /* used internally by dmg_read_mish_block to remember offsets of blocks * across calls */ - uint64_t last_in_offset; + uint64_t data_fork_offset; uint64_t last_out_offset; /* exported for dmg_open */ uint32_t max_compressed_size; @@ -203,6 +203,8 @@ static int dmg_read_mish_block(BDRVDMGState *s, DmgHeaderState *ds, size_t new_size; uint32_t chunk_count; int64_t offset = 0; + uint64_t data_offset; + uint64_t in_offset = ds->data_fork_offset; type = buff_read_uint32(buffer, offset); /* skip data that is not a valid MISH block (invalid magic or too small) */ @@ -211,8 +213,12 @@ static int dmg_read_mish_block(BDRVDMGState *s, DmgHeaderState *ds, return 0; } - offset += 4; - offset += 200; + /* location in data fork for (compressed) blob (in bytes) */ + data_offset = buff_read_uint64(buffer, offset + 0x18); + in_offset += data_offset; + + /* move to begin of chunk entries */ + offset += 204; chunk_count = (count - 204) / 40; new_size = sizeof(uint64_t) * (s->n_chunks + chunk_count); @@ -228,7 +234,6 @@ static int dmg_read_mish_block(BDRVDMGState *s, DmgHeaderState *ds, if (s->types[i] != 0x80000005 && s->types[i] != 1 && s->types[i] != 2) { if (s->types[i] == 0xffffffff && i > 0) { - ds->last_in_offset = s->offsets[i - 1] + s->lengths[i - 1]; ds->last_out_offset = s->sectors[i - 1] + s->sectorcounts[i - 1]; } @@ -255,7 +260,7 @@ static int dmg_read_mish_block(BDRVDMGState *s, DmgHeaderState *ds, } s->offsets[i] = buff_read_uint64(buffer, offset); - s->offsets[i] += ds->last_in_offset; + s->offsets[i] += in_offset; offset += 8; s->lengths[i] = buff_read_uint64(buffer, offset); @@ -413,7 +418,7 @@ static int dmg_open(BlockDriverState *bs, QDict *options, int flags, s->n_chunks = 0; s->offsets = s->lengths = s->sectors = s->sectorcounts = NULL; /* used by dmg_read_mish_block to keep track of the current I/O position */ - ds.last_in_offset = 0; + ds.data_fork_offset = 0; ds.last_out_offset = 0; ds.max_compressed_size = 1; ds.max_sectors_per_chunk = 1; @@ -425,6 +430,15 @@ static int dmg_open(BlockDriverState *bs, QDict *options, int flags, goto fail; } + /* offset of data fork (DataForkOffset) */ + ret = read_uint64(bs, offset + 0x18, &ds.data_fork_offset); + if (ret < 0) { + goto fail; + } else if (ds.data_fork_offset > offset) { + ret = -EINVAL; + goto fail; + } + /* offset of resource fork (RsrcForkOffset) */ ret = read_uint64(bs, offset + 0x28, &rsrc_fork_offset); if (ret < 0) { -- cgit v1.2.1