From 65a23f5dbee4497064e9bb467f81138a62b0dae1 Mon Sep 17 00:00:00 2001 From: Daniel Axtens Date: Tue, 1 Jan 2019 16:01:40 +1100 Subject: [PATCH] 7zip: fix crash when parsing certain archives Fuzzing with CRCs disabled revealed that a call to get_uncompressed_data() would sometimes fail to return at least 'minimum' bytes. This can cause the crc32() invocation in header_bytes to read off into invalid memory. A specially crafted archive can use this to cause a crash. An ASAN trace is below, but ASAN is not required - an uninstrumented binary will also crash. ==7719==ERROR: AddressSanitizer: SEGV on unknown address 0x631000040000 (pc 0x7fbdb3b3ec1d bp 0x7ffe77a51310 sp 0x7ffe77a51150 T0) ==7719==The signal is caused by a READ memory access. #0 0x7fbdb3b3ec1c in crc32_z (/lib/x86_64-linux-gnu/libz.so.1+0x2c1c) #1 0x84f5eb in header_bytes (/tmp/libarchive/bsdtar+0x84f5eb) #2 0x856156 in read_Header (/tmp/libarchive/bsdtar+0x856156) #3 0x84e134 in slurp_central_directory (/tmp/libarchive/bsdtar+0x84e134) #4 0x849690 in archive_read_format_7zip_read_header (/tmp/libarchive/bsdtar+0x849690) #5 0x5713b7 in _archive_read_next_header2 (/tmp/libarchive/bsdtar+0x5713b7) #6 0x570e63 in _archive_read_next_header (/tmp/libarchive/bsdtar+0x570e63) #7 0x6f08bd in archive_read_next_header (/tmp/libarchive/bsdtar+0x6f08bd) #8 0x52373f in read_archive (/tmp/libarchive/bsdtar+0x52373f) #9 0x5257be in tar_mode_x (/tmp/libarchive/bsdtar+0x5257be) #10 0x51daeb in main (/tmp/libarchive/bsdtar+0x51daeb) #11 0x7fbdb27cab96 in __libc_start_main /build/glibc-OTsEL5/glibc-2.27/csu/../csu/libc-start.c:310 #12 0x41dd09 in _start (/tmp/libarchive/bsdtar+0x41dd09) This was primarly done with afl and FairFuzz. Some early corpus entries may have been generated by qsym. --- libarchive/archive_read_support_format_7zip.c | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-) diff --git a/libarchive/archive_read_support_format_7zip.c b/libarchive/archive_read_support_format_7zip.c index bccbf8966..b6d1505d3 100644 --- a/libarchive/archive_read_support_format_7zip.c +++ b/libarchive/archive_read_support_format_7zip.c @@ -2964,13 +2964,7 @@ get_uncompressed_data(struct archive_read *a, const void **buff, size_t size, if (zip->codec == _7Z_COPY && zip->codec2 == (unsigned long)-1) { /* Copy mode. */ - /* - * Note: '1' here is a performance optimization. - * Recall that the decompression layer returns a count of - * available bytes; asking for more than that forces the - * decompressor to combine reads by copying data. - */ - *buff = __archive_read_ahead(a, 1, &bytes_avail); + *buff = __archive_read_ahead(a, minimum, &bytes_avail); if (bytes_avail <= 0) { archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,