{"id":1408,"date":"2017-03-03T13:07:28","date_gmt":"2017-03-03T11:07:28","guid":{"rendered":"http:\/\/blogs.gentoo.org\/ago\/?p=1408"},"modified":"2017-03-26T15:22:45","modified_gmt":"2017-03-26T13:22:45","slug":"potrace-heap-based-buffer-overflow-in-bm_readbody_bmp-bitmap_io-c-incomplete-fix-for-cve-2016-8698","status":"publish","type":"post","link":"https:\/\/blogs.gentoo.org\/ago\/2017\/03\/03\/potrace-heap-based-buffer-overflow-in-bm_readbody_bmp-bitmap_io-c-incomplete-fix-for-cve-2016-8698\/","title":{"rendered":"potrace: heap-based buffer overflow in bm_readbody_bmp (bitmap_io.c) (incomplete fix for CVE-2016-8698)"},"content":{"rendered":"<p><strong>Description<\/strong>:<br \/>\n<a href=\"http:\/\/potrace.sourceforge.net\/\">potrace<\/a> is a utility that transforms bitmaps into vector graphics.<\/p>\n<p>A fuzz on 1.14 showed that an overflow previously reported as CVE-2016-8698 was not really fixed. Since there isn&#8217;t a public git repository, I uploaded the patch on my &#8216;poc&#8217; repository on github. The patch was sent from the upstream maintainer, Mr. Peter Selinger.<\/p>\n<p>The complete ASan output:<\/p>\n<pre><font size=\"2\"># potrace $FILE\r\n==7325==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x60200000efd0 at pc 0x00000051dc51 bp 0x7ffc766b1a30 sp 0x7ffc766b1a28\r\nREAD of size 8 at 0x60200000efd0 thread T0\r\n    #0 0x51dc50 in bm_readbody_bmp \/tmp\/portage\/media-gfx\/potrace-1.14\/work\/potrace-1.14\/src\/bitmap_io.c:754:4\r\n    #1 0x51dc50 in bm_read \/tmp\/portage\/media-gfx\/potrace-1.14\/work\/potrace-1.14\/src\/bitmap_io.c:138\r\n    #2 0x510a45 in process_file \/tmp\/portage\/media-gfx\/potrace-1.14\/work\/potrace-1.14\/src\/main.c:1058:9\r\n    #3 0x50dd56 in main \/tmp\/portage\/media-gfx\/potrace-1.14\/work\/potrace-1.14\/src\/main.c:1214:7\r\n    #4 0x7f6c7333e78f in __libc_start_main \/tmp\/portage\/sys-libs\/glibc-2.23-r3\/work\/glibc-2.23\/csu\/..\/csu\/libc-start.c:289\r\n    #5 0x419b68 in getenv (\/usr\/bin\/potrace+0x419b68)\r\n\r\n0x60200000efd1 is located 0 bytes to the right of 1-byte region [0x60200000efd0,0x60200000efd1)\r\nallocated by thread T0 here:\r\n    #0 0x4d2b25 in calloc \/tmp\/portage\/sys-devel\/llvm-3.9.1-r1\/work\/llvm-3.9.1.src\/projects\/compiler-rt\/lib\/asan\/asan_malloc_linux.cc:72\r\n    #1 0x519776 in bm_new \/tmp\/portage\/media-gfx\/potrace-1.14\/work\/potrace-1.14\/src\/bitmap.h:121:30\r\n    #2 0x519776 in bm_readbody_bmp \/tmp\/portage\/media-gfx\/potrace-1.14\/work\/potrace-1.14\/src\/bitmap_io.c:574\r\n    #3 0x519776 in bm_read \/tmp\/portage\/media-gfx\/potrace-1.14\/work\/potrace-1.14\/src\/bitmap_io.c:138\r\n    #4 0x510a45 in process_file \/tmp\/portage\/media-gfx\/potrace-1.14\/work\/potrace-1.14\/src\/main.c:1058:9\r\n    #5 0x50dd56 in main \/tmp\/portage\/media-gfx\/potrace-1.14\/work\/potrace-1.14\/src\/main.c:1214:7\r\n    #6 0x7f6c7333e78f in __libc_start_main \/tmp\/portage\/sys-libs\/glibc-2.23-r3\/work\/glibc-2.23\/csu\/..\/csu\/libc-start.c:289\r\n\r\nSUMMARY: AddressSanitizer: heap-buffer-overflow \/tmp\/portage\/media-gfx\/potrace-1.14\/work\/potrace-1.14\/src\/bitmap_io.c:754:4 in bm_readbody_bmp\r\nShadow bytes around the buggy address:\r\n  0x0c047fff9da0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa\r\n  0x0c047fff9db0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa\r\n  0x0c047fff9dc0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa\r\n  0x0c047fff9dd0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa\r\n  0x0c047fff9de0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa\r\n=&gt;0x0c047fff9df0: fa fa fa fa fa fa fa fa fa fa[01]fa fa fa 04 fa\r\n  0x0c047fff9e00: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa\r\n  0x0c047fff9e10: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa\r\n  0x0c047fff9e20: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa\r\n  0x0c047fff9e30: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa\r\n  0x0c047fff9e40: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa\r\nShadow byte legend (one shadow byte represents 8 application bytes):\r\n  Addressable:           00\r\n  Partially addressable: 01 02 03 04 05 06 07 \r\n  Heap left redzone:       fa\r\n  Heap right redzone:      fb\r\n  Freed heap region:       fd\r\n  Stack left redzone:      f1\r\n  Stack mid redzone:       f2\r\n  Stack right redzone:     f3\r\n  Stack partial redzone:   f4\r\n  Stack after return:      f5\r\n  Stack use after scope:   f8\r\n  Global redzone:          f9\r\n  Global init order:       f6\r\n  Poisoned by user:        f7\r\n  Container overflow:      fc\r\n  Array cookie:            ac\r\n  Intra object redzone:    bb\r\n  ASan internal:           fe\r\n  Left alloca redzone:     ca\r\n  Right alloca redzone:    cb\r\n==7325==ABORTING\r\n<\/font><\/pre>\n<p><strong>Affected version:<\/strong><br \/>\n1.14<\/p>\n<p><strong>Fixed version:<\/strong><br \/>\n1.15<\/p>\n<p><strong>Commit fix:<\/strong><br \/>\n<a href=\"https:\/\/github.com\/asarubbo\/poc\/blob\/master\/00219-potrace-heapoverflow-bm_readbody_bmp-PATCH\">https:\/\/github.com\/asarubbo\/poc\/blob\/master\/00219-potrace-heapoverflow-bm_readbody_bmp-PATCH<\/a><\/p>\n<p><strong>Credit:<\/strong><br \/>\nThis bug was discovered by Agostino Sarubbo of Gentoo.<\/p>\n<p><strong>CVE:<\/strong><br \/>\nCVE-2017-7263<\/p>\n<p><strong>Reproducer:<\/strong><br \/>\n<a href=\"https:\/\/github.com\/asarubbo\/poc\/blob\/master\/00210-potrace-heapoverflow-bm_readbody_bmp\">https:\/\/github.com\/asarubbo\/poc\/blob\/master\/00210-potrace-heapoverflow-bm_readbody_bmp<\/a><\/p>\n<p><strong>Timeline:<\/strong><br \/>\n2017-02-26: bug discovered and reported to upstream<br \/>\n2017-02-28: upstream released a patch<br \/>\n2017-03-03: blog post about the issue<br \/>\n2017-03-26: CVE assigned<\/p>\n<p><strong>Note:<\/strong><br \/>\nThis bug was found with <a href=\"http:\/\/lcamtuf.coredump.cx\/afl\">American Fuzzy Lop<\/a>.<\/p>\n<p><strong>Permalink:<\/strong><\/p>\n<blockquote data-secret=\"50fyu0vhOq\" class=\"wp-embedded-content\"><p><a href=\"http:\/\/blogs.gentoo.org\/ago\/2017\/03\/03\/potrace-heap-based-buffer-overflow-in-bm_readbody_bmp-bitmap_io-c-incomplete-fix-for-cve-2016-8698\/\">potrace: heap-based buffer overflow in bm_readbody_bmp (bitmap_io.c) (incomplete fix for CVE-2016-8698)<\/a><\/p><\/blockquote>\n<p><iframe class=\"wp-embedded-content\" sandbox=\"allow-scripts\" security=\"restricted\" style=\"position: absolute; clip: rect(1px, 1px, 1px, 1px);\" src=\"http:\/\/blogs.gentoo.org\/ago\/2017\/03\/03\/potrace-heap-based-buffer-overflow-in-bm_readbody_bmp-bitmap_io-c-incomplete-fix-for-cve-2016-8698\/embed\/#?secret=50fyu0vhOq\" data-secret=\"50fyu0vhOq\" width=\"600\" height=\"338\" title=\"&#8220;potrace: heap-based buffer overflow in bm_readbody_bmp (bitmap_io.c) (incomplete fix for CVE-2016-8698)&#8221; &#8212; agostino&#039;s blog\" frameborder=\"0\" marginwidth=\"0\" marginheight=\"0\" scrolling=\"no\"><\/iframe><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Description: potrace is a utility that transforms bitmaps into vector graphics. A fuzz on 1.14 showed that an overflow previously reported as CVE-2016-8698 was not really fixed. Since there isn&#8217;t a public git repository, I uploaded the patch on my &hellip; <a href=\"https:\/\/blogs.gentoo.org\/ago\/2017\/03\/03\/potrace-heap-based-buffer-overflow-in-bm_readbody_bmp-bitmap_io-c-incomplete-fix-for-cve-2016-8698\/\">Continue reading <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":140,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"spay_email":"","jetpack_publicize_message":"","jetpack_is_tweetstorm":false,"jetpack_publicize_feature_enabled":true},"categories":[12,10],"tags":[],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p2EaBc-mI","_links":{"self":[{"href":"https:\/\/blogs.gentoo.org\/ago\/wp-json\/wp\/v2\/posts\/1408"}],"collection":[{"href":"https:\/\/blogs.gentoo.org\/ago\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.gentoo.org\/ago\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.gentoo.org\/ago\/wp-json\/wp\/v2\/users\/140"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.gentoo.org\/ago\/wp-json\/wp\/v2\/comments?post=1408"}],"version-history":[{"count":5,"href":"https:\/\/blogs.gentoo.org\/ago\/wp-json\/wp\/v2\/posts\/1408\/revisions"}],"predecessor-version":[{"id":1524,"href":"https:\/\/blogs.gentoo.org\/ago\/wp-json\/wp\/v2\/posts\/1408\/revisions\/1524"}],"wp:attachment":[{"href":"https:\/\/blogs.gentoo.org\/ago\/wp-json\/wp\/v2\/media?parent=1408"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.gentoo.org\/ago\/wp-json\/wp\/v2\/categories?post=1408"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.gentoo.org\/ago\/wp-json\/wp\/v2\/tags?post=1408"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}