diff -Nru fontconfig-2.11.0/debian/changelog fontconfig-2.11.0/debian/changelog --- fontconfig-2.11.0/debian/changelog 2014-06-04 16:13:22.000000000 +0000 +++ fontconfig-2.11.0/debian/changelog 2016-08-16 17:30:18.000000000 +0000 @@ -1,3 +1,12 @@ +fontconfig (2.11.0-0ubuntu4.2) trusty-security; urgency=medium + + * SECURITY UPDATE: double free when handling cache files + - debian/patches/CVE-2016-5384.patch: properly validate offsets in + cache files in src/fccache.c. + - CVE-2016-5384 + + -- Marc Deslauriers Tue, 16 Aug 2016 13:30:18 -0400 + fontconfig (2.11.0-0ubuntu4.1) trusty; urgency=medium * 0001-Bug-73291-poppler-does-not-show-fl-ligature.patch: Don't alias TeX diff -Nru fontconfig-2.11.0/debian/patches/CVE-2016-5384.patch fontconfig-2.11.0/debian/patches/CVE-2016-5384.patch --- fontconfig-2.11.0/debian/patches/CVE-2016-5384.patch 1970-01-01 00:00:00.000000000 +0000 +++ fontconfig-2.11.0/debian/patches/CVE-2016-5384.patch 2016-08-16 17:29:05.000000000 +0000 @@ -0,0 +1,161 @@ +Backport of: + +From 7a4a5bd7897d216f0794ca9dbce0a4a5c9d14940 Mon Sep 17 00:00:00 2001 +From: Tobias Stoeckmann +Date: Sat, 25 Jun 2016 19:18:53 +0200 +Subject: Properly validate offsets in cache files. + +The cache files are insufficiently validated. Even though the magic +number at the beginning of the file as well as time stamps are checked, +it is not verified if contained offsets are in legal ranges or are +even pointers. + +The lack of validation allows an attacker to trigger arbitrary free() +calls, which in turn allows double free attacks and therefore arbitrary +code execution. Due to the conversion from offsets into pointers through +macros, this even allows to circumvent ASLR protections. + +This attack vector allows privilege escalation when used with setuid +binaries like fbterm. A user can create ~/.fonts or any other +system-defined user-private font directory, run fc-cache and adjust +cache files in ~/.cache/fontconfig. The execution of setuid binaries will +scan these files and therefore are prone to attacks. + +If it's not about code execution, an endless loop can be created by +letting linked lists become circular linked lists. + +This patch verifies that: + +- The file is not larger than the maximum addressable space, which + basically only affects 32 bit systems. This allows out of boundary + access into unallocated memory. +- Offsets are always positive or zero +- Offsets do not point outside file boundaries +- No pointers are allowed in cache files, every "pointer or offset" + field must be an offset or NULL +- Iterating linked lists must not take longer than the amount of elements + specified. A violation of this rule can break a possible endless loop. + +If one or more of these points are violated, the cache is recreated. +This is current behaviour. + +Even though this patch fixes many issues, the use of mmap() shall be +forbidden in setuid binaries. It is impossible to guarantee with these +checks that a malicious user does not change cache files after +verification. This should be handled in a different patch. + +Signed-off-by: Tobias Stoeckmann + +Index: fontconfig-2.11.0/src/fccache.c +=================================================================== +--- fontconfig-2.11.0.orig/src/fccache.c 2016-08-16 13:28:15.106477627 -0400 ++++ fontconfig-2.11.0/src/fccache.c 2016-08-16 13:28:54.794974087 -0400 +@@ -27,6 +27,7 @@ + #include + #include + #include ++#include + #include + #include + #if defined(HAVE_MMAP) || defined(__CYGWIN__) +@@ -544,6 +545,82 @@ + return cache->checksum == (int) dir_stat->st_mtime; + } + ++static FcBool ++FcCacheOffsetsValid (FcCache *cache) ++{ ++ char *base = (char *)cache; ++ char *end = base + cache->size; ++ intptr_t *dirs; ++ FcFontSet *fs; ++ int i, j; ++ ++ if (cache->dir < 0 || cache->dir > cache->size - sizeof (intptr_t) || ++ memchr (base + cache->dir, '\0', cache->size - cache->dir) == NULL) ++ return FcFalse; ++ ++ if (cache->dirs < 0 || cache->dirs >= cache->size || ++ cache->dirs_count < 0 || ++ cache->dirs_count > (cache->size - cache->dirs) / sizeof (intptr_t)) ++ return FcFalse; ++ ++ dirs = FcCacheDirs (cache); ++ if (dirs) ++ { ++ for (i = 0; i < cache->dirs_count; i++) ++ { ++ FcChar8 *dir; ++ ++ if (dirs[i] < 0 || ++ dirs[i] > end - (char *) dirs - sizeof (intptr_t)) ++ return FcFalse; ++ ++ dir = FcOffsetToPtr (dirs, dirs[i], FcChar8); ++ if (memchr (dir, '\0', end - (char *) dir) == NULL) ++ return FcFalse; ++ } ++ } ++ ++ if (cache->set < 0 || cache->set > cache->size - sizeof (FcFontSet)) ++ return FcFalse; ++ ++ fs = FcCacheSet (cache); ++ if (fs) ++ { ++ if (fs->nfont > (end - (char *) fs) / sizeof (FcPattern)) ++ return FcFalse; ++ ++ if (fs->fonts != 0 && !FcIsEncodedOffset(fs->fonts)) ++ return FcFalse; ++ ++ for (i = 0; i < fs->nfont; i++) ++ { ++ FcPattern *font = FcFontSetFont (fs, i); ++ FcPatternElt *e; ++ FcValueListPtr l; ++ ++ if ((char *) font < base || ++ (char *) font > end - sizeof (FcFontSet) || ++ font->elts_offset < 0 || ++ font->elts_offset > end - (char *) font || ++ font->num > (end - (char *) font - font->elts_offset) / sizeof (FcPatternElt)) ++ return FcFalse; ++ ++ ++ e = FcPatternElts(font); ++ if (e->values != 0 && !FcIsEncodedOffset(e->values)) ++ return FcFalse; ++ ++ for (j = font->num, l = FcPatternEltValues(e); j >= 0 && l; j--, l = FcValueListNext(l)) ++ if (l->next != NULL && !FcIsEncodedOffset(l->next)) ++ break; ++ if (j < 0) ++ return FcFalse; ++ } ++ } ++ ++ return FcTrue; ++} ++ + /* + * Map a cache file into memory + */ +@@ -553,7 +630,8 @@ + FcCache *cache; + FcBool allocated = FcFalse; + +- if (fd_stat->st_size < (int) sizeof (FcCache)) ++ if (fd_stat->st_size > INTPTR_MAX || ++ fd_stat->st_size < (int) sizeof (FcCache)) + return NULL; + cache = FcCacheFindByStat (fd_stat); + if (cache) +@@ -609,6 +687,7 @@ + if (cache->magic != FC_CACHE_MAGIC_MMAP || + cache->version < FC_CACHE_CONTENT_VERSION || + cache->size != (intptr_t) fd_stat->st_size || ++ !FcCacheOffsetsValid (cache) || + !FcCacheTimeValid (cache, dir_stat) || + !FcCacheInsert (cache, fd_stat)) + { diff -Nru fontconfig-2.11.0/debian/patches/series fontconfig-2.11.0/debian/patches/series --- fontconfig-2.11.0/debian/patches/series 2014-06-04 16:03:05.000000000 +0000 +++ fontconfig-2.11.0/debian/patches/series 2016-08-16 17:28:11.000000000 +0000 @@ -7,3 +7,4 @@ 07_no_bitmaps.patch 0001-Bug-73291-poppler-does-not-show-fl-ligature.patch +CVE-2016-5384.patch