[Bug 13113] New: receive_xattr heap overflow when prepending RSYNC_PREFIX
samba-bugs at samba.org
samba-bugs at samba.org
Tue Oct 31 04:40:14 UTC 2017
https://bugzilla.samba.org/show_bug.cgi?id=13113
Bug ID: 13113
Summary: receive_xattr heap overflow when prepending
RSYNC_PREFIX
Product: rsync
Version: 3.1.3
Hardware: All
OS: All
Status: NEW
Severity: normal
Priority: P5
Component: core
Assignee: wayned at samba.org
Reporter: jeriko.one at gmx.us
QA Contact: rsync-qa at samba.org
Created attachment 13745
--> https://bugzilla.samba.org/attachment.cgi?id=13745&action=edit
change MIGHT_NEED_RPRE to am_root <= 0
$ ./rsync -v
rsync version 3.1.3dev protocol version 31
I've built with HAVE_LINUX_XATTRS
I'm running rsyncd as a non root user.
the args I'm sending rsyncd when connecting are
{"--server", "--filter", "+x jk", "-X", ".", ".", "\0"};
code snippets are from xattrs.c
in receive_xattr a name is read from the sender. The name might need to be
prefixed depending on am_root. To make room for this prefix extra_len is
possibly allocated.
818 size_t extra_len = MIGHT_NEED_RPRE ? RPRE_LEN : 0;
822 ptr = new_array(char, dget_len + extra_len + name_len); <-- the
length values are received from the sender. In this case I'm sending dget_len =
0
61 #ifdef HAVE_LINUX_XATTRS
62 #define MIGHT_NEED_RPRE (am_root < 0)
The issue is that am_root < 0 isn't the only time that a prefix might be
prepended to name. If we're running as a normal user (am_root == 0) and the
sender has sent a filter with an xattr filter then the prefix will also be
prepended.
840 #ifdef HAVE_LINUX_XATTRS
841 /* Non-root can only save the user namespace. */
842 if (am_root <= 0 && !HAS_PREFIX(name, USER_PREFIX)) {
843 if (!am_root && !saw_xattr_filter) {
844 free(ptr);
845 continue;
846 }
847 name -= RPRE_LEN;
848 name_len += RPRE_LEN;
849 memcpy(name, RSYNC_PREFIX, RPRE_LEN);
850 need_sort = 1;
851 }
Since there wasn't any extra_len allocated name -= RPRE_LEN can point before
the buffer causing a heap overwrite.
The patch I've attached changes MIGHT_NEED_RPRE (am_root <= 0) since the only
time we might add a prefix is when we're not root.
ASan output:
=================================================================
==12012==ERROR: AddressSanitizer: heap-buffer-overflow on address
0x60200000e825 at pc 0x7ffff6ef8864 bp 0x7fffffff9b50 sp 0x7fffffff92f8
WRITE of size 11 at 0x60200000e825 thread T0
#0 0x7ffff6ef8863 in __asan_memcpy
(/usr/lib/gcc/x86_64-pc-linux-gnu/5.4.0/libasan.so.2+0x8c863)
#1 0x4a2eef in receive_xattr /home/raj/rsync/rsync/xattrs.c:849
#2 0x40beac in recv_file_entry /home/raj/rsync/rsync/flist.c:1108
#3 0x415bee in recv_file_list /home/raj/rsync/rsync/flist.c:2476
#4 0x454eaa in do_server_recv /home/raj/rsync/rsync/main.c:1036
#5 0x4556f4 in start_server /home/raj/rsync/rsync/main.c:1115
#6 0x4b20f9 in rsync_module /home/raj/rsync/rsync/clientserver.c:1007
#7 0x4b2b18 in start_daemon /home/raj/rsync/rsync/clientserver.c:1135
#8 0x48f636 in start_accept_loop /home/raj/rsync/rsync/socket.c:618
#9 0x4b32d9 in daemon_main /home/raj/rsync/rsync/clientserver.c:1237
#10 0x458318 in main /home/raj/rsync/rsync/main.c:1630
#11 0x7ffff64d866f in __libc_start_main (/lib64/libc.so.6+0x2066f)
#12 0x4047c8 in _start (/home/raj/rsync/asan/bin/rsync+0x4047c8)
0x60200000e825 is located 11 bytes to the left of 3-byte region
[0x60200000e830,0x60200000e833)
allocated by thread T0 here:
#0 0x7ffff6f04572 in malloc
(/usr/lib/gcc/x86_64-pc-linux-gnu/5.4.0/libasan.so.2+0x98572)
#1 0x44e48b in _new_array /home/raj/rsync/rsync/util2.c:68
#2 0x4a2c66 in receive_xattr /home/raj/rsync/rsync/xattrs.c:822
#3 0x40beac in recv_file_entry /home/raj/rsync/rsync/flist.c:1108
#4 0x415bee in recv_file_list /home/raj/rsync/rsync/flist.c:2476
#5 0x454eaa in do_server_recv /home/raj/rsync/rsync/main.c:1036
#6 0x4556f4 in start_server /home/raj/rsync/rsync/main.c:1115
#7 0x4b20f9 in rsync_module /home/raj/rsync/rsync/clientserver.c:1007
#8 0x4b2b18 in start_daemon /home/raj/rsync/rsync/clientserver.c:1135
#9 0x48f636 in start_accept_loop /home/raj/rsync/rsync/socket.c:618
#10 0x4b32d9 in daemon_main /home/raj/rsync/rsync/clientserver.c:1237
#11 0x458318 in main /home/raj/rsync/rsync/main.c:1630
#12 0x7ffff64d866f in __libc_start_main (/lib64/libc.so.6+0x2066f)
SUMMARY: AddressSanitizer: heap-buffer-overflow ??:0 __asan_memcpy
Shadow bytes around the buggy address:
0x0c047fff9cb0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9cc0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9cd0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9ce0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9cf0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x0c047fff9d00: fa fa fa fa[fa]fa 03 fa fa fa 04 fa fa fa 00 07
0x0c047fff9d10: fa fa fd fd fa fa 02 fa fa fa 02 fa fa fa 00 01
0x0c047fff9d20: fa fa 03 fa fa fa 06 fa fa fa 00 01 fa fa 06 fa
0x0c047fff9d30: fa fa 00 01 fa fa 06 fa fa fa fd fd fa fa fd fa
0x0c047fff9d40: fa fa 00 01 fa fa fd fa fa fa fd fa fa fa 00 01
0x0c047fff9d50: fa fa fd fa fa fa fd fa fa fa 02 fa fa fa fd fa
Shadow byte legend (one shadow byte represents 8 application bytes):
Addressable: 00
Partially addressable: 01 02 03 04 05 06 07
Heap left redzone: fa
Heap right redzone: fb
Freed heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack partial redzone: f4
Stack after return: f5
Stack use after scope: f8
Global redzone: f9
Global init order: f6
Poisoned by user: f7
Container overflow: fc
Array cookie: ac
Intra object redzone: bb
ASan internal: fe
==12012==ABORTING
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