| 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(+) |
| |
| [for import into Buildroot] |
| Signed-off-by: Thomas De Schampheleire <thomas.de_schampheleire@nokia.com> |
| Upstream-status: backport |
| |
| CVE-2018-1000878 |
| |
| diff --git a/libarchive/archive_read_support_format_rar.c b/libarchive/archive_read_support_format_rar.c |
| index 6f419c27..a8cc5c94 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); |
| -- |
| 2.19.2 |
| |