76 lines
3.1 KiB
Diff
76 lines
3.1 KiB
Diff
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From d00ccaf8c20efbd009964e3e2697d26907d14163 Mon Sep 17 00:00:00 2001
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From: Ondrej Dubaj <odubaj@redhat.com>
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Date: Tue, 30 Apr 2019 11:36:08 +0200
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Subject: [PATCH] rar: file split across multi-part archives must match
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Fuzzing uncovered some UAF and memory overrun bugs where a file in a
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single file archive reported that it was split across multiple
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volumes. This was caused by ppmd7 operations calling
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rar_br_fillup. This would invoke rar_read_ahead, which would in some
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situations invoke archive_read_format_rar_read_header. That would
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check the new file name against the old file name, and if they didn't
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match up it would free the ppmd7 buffer and allocate a new
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one. However, because the ppmd7 decoder wasn't actually done with the
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buffer, it would continue to used the freed buffer. Both reads and
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writes to the freed region can be observed.
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This is quite tricky to solve: once the buffer has been freed it is
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too late, as the ppmd7 decoder functions almost universally assume
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success - there's no way for ppmd_read to signal error, nor are there
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good ways for functions like Range_Normalise to propagate them. So we
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can't detect after the fact that we're in an invalid state - e.g. by
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checking rar->cursor, we have to prevent ourselves from ever ending up
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there. So, when we are in the dangerous part or rar_read_ahead that
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assumes a valid split, we set a flag force read_header to either go
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down the path for split files or bail. This means that the ppmd7
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decoder keeps a valid buffer and just runs out of data.
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Found with a combination of AFL, afl-rb and qsym.
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---
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libarchive/archive_read_support_format_rar.c | 9 +++++++++
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1 file changed, 9 insertions(+)
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diff --git a/libarchive/archive_read_support_format_rar.c b/libarchive/archive_read_support_format_rar.c
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index cbb14c3..c4a8278 100644
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--- a/libarchive/archive_read_support_format_rar.c
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+++ b/libarchive/archive_read_support_format_rar.c
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@@ -258,6 +258,7 @@ struct rar
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struct data_block_offsets *dbo;
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unsigned int cursor;
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unsigned int nodes;
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+ char filename_must_match;
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/* LZSS members */
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struct huffman_code maincode;
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@@ -1570,6 +1571,12 @@ read_header(struct archive_read *a, struct archive_entry *entry,
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}
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return ret;
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}
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+ else if (rar->filename_must_match)
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+ {
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+ archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
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+ "Mismatch of file parts split across multi-volume archive");
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+ return (ARCHIVE_FATAL);
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+ }
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rar->filename_save = (char*)realloc(rar->filename_save,
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filename_size + 1);
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@@ -2938,12 +2945,14 @@ rar_read_ahead(struct archive_read *a, size_t min, ssize_t *avail)
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else if (*avail == 0 && rar->main_flags & MHD_VOLUME &&
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rar->file_flags & FHD_SPLIT_AFTER)
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{
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+ rar->filename_must_match = 1;
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ret = archive_read_format_rar_read_header(a, a->entry);
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if (ret == (ARCHIVE_EOF))
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{
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rar->has_endarc_header = 1;
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ret = archive_read_format_rar_read_header(a, a->entry);
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}
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+ rar->filename_must_match = 0;
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if (ret != (ARCHIVE_OK))
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return NULL;
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return rar_read_ahead(a, min, avail);
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--
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2.17.1
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