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- From bfcfe6f04ed20db2504db8a254d1f40a1d84eb28 Mon Sep 17 00:00:00 2001
- From: Daniel Axtens <dja@axtens.net>
- Date: Tue, 4 Dec 2018 00:55:22 +1100
- Subject: [PATCH] rar: file split across multi-part archives must match
-
- Fuzzing uncovered some UAF and memory overrun bugs where a file in a
- single file archive reported that it was split across multiple
- volumes. This was caused by ppmd7 operations calling
- rar_br_fillup. This would invoke rar_read_ahead, which would in some
- situations invoke archive_read_format_rar_read_header. That would
- check the new file name against the old file name, and if they didn't
- match up it would free the ppmd7 buffer and allocate a new
- one. However, because the ppmd7 decoder wasn't actually done with the
- buffer, it would continue to used the freed buffer. Both reads and
- writes to the freed region can be observed.
-
- This is quite tricky to solve: once the buffer has been freed it is
- too late, as the ppmd7 decoder functions almost universally assume
- success - there's no way for ppmd_read to signal error, nor are there
- good ways for functions like Range_Normalise to propagate them. So we
- can't detect after the fact that we're in an invalid state - e.g. by
- checking rar->cursor, we have to prevent ourselves from ever ending up
- there. So, when we are in the dangerous part or rar_read_ahead that
- assumes a valid split, we set a flag force read_header to either go
- down the path for split files or bail. This means that the ppmd7
- decoder keeps a valid buffer and just runs out of data.
-
- Found with a combination of AFL, afl-rb and qsym.
- ---
- libarchive/archive_read_support_format_rar.c | 9 +++++++++
- 1 file changed, 9 insertions(+)
-
- diff --git a/libarchive/archive_read_support_format_rar.c b/libarchive/archive_read_support_format_rar.c
- index 6f419c270..a8cc5c94d 100644
- --- a/libarchive/archive_read_support_format_rar.c
- +++ b/libarchive/archive_read_support_format_rar.c
- @@ -258,6 +258,7 @@ struct rar
- struct data_block_offsets *dbo;
- unsigned int cursor;
- unsigned int nodes;
- + char filename_must_match;
-
- /* LZSS members */
- struct huffman_code maincode;
- @@ -1560,6 +1561,12 @@ read_header(struct archive_read *a, struct archive_entry *entry,
- }
- return ret;
- }
- + else if (rar->filename_must_match)
- + {
- + archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
- + "Mismatch of file parts split across multi-volume archive");
- + return (ARCHIVE_FATAL);
- + }
-
- rar->filename_save = (char*)realloc(rar->filename_save,
- filename_size + 1);
- @@ -2933,12 +2940,14 @@ rar_read_ahead(struct archive_read *a, size_t min, ssize_t *avail)
- else if (*avail == 0 && rar->main_flags & MHD_VOLUME &&
- rar->file_flags & FHD_SPLIT_AFTER)
- {
- + rar->filename_must_match = 1;
- ret = archive_read_format_rar_read_header(a, a->entry);
- if (ret == (ARCHIVE_EOF))
- {
- rar->has_endarc_header = 1;
- ret = archive_read_format_rar_read_header(a, a->entry);
- }
- + rar->filename_must_match = 0;
- if (ret != (ARCHIVE_OK))
- return NULL;
- return rar_read_ahead(a, min, avail);
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