[Bug 13112] New: receive_xattr heap overread with non null terminated name and xattr filter

[samba-bugs at samba.org]

https://bugzilla.samba.org/show_bug.cgi?id=13112

            Bug ID: 13112
           Summary: receive_xattr heap overread with non null terminated
                    name and xattr filter
           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 13744
  --> https://bugzilla.samba.org/attachment.cgi?id=13744&action=edit
Make room for trailing NULL and use read_sbuf

$ ./rsync -v
rsync  version 3.1.3dev  protocol version 31

code snippets are from receive_xattr in xattrs.c

in receive_xattr a name is read from the sender. The sender sends the length of
the name, and then sends the name. The name is read in via read_buf so it's not
null terminated. 

 815         size_t name_len = read_varint(f);

 826         read_buf(f, name, name_len);


If the sender sent --filter that had an xattr filter then this name will be
passed to name_is_excluded. 

 834         if (saw_xattr_filter) {
 835             if (name_is_excluded(name, NAME_IS_XATTR, ALL_FILTERS)) {

This can lead to a heap overread as name_is_excluded is expecting a NULL
terminated string. 

These are the arguments I'm sending to the daemon when connecting
{"--server", "--filter", "+x jk", "-X", ".", ".", "\0"};

I provided a patch that will make room for a NULL byte in name, and use
read_sbuf instead. 

ASan output: 
=================================================================
==3497==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x60200000e831
at pc 0x7ffff6edc15b bp 0x7fffffff9990 sp 0x7fffffff9138
READ of size 2 at 0x60200000e831 thread T0
    #0 0x7ffff6edc15a in strlen
(/usr/lib/gcc/x86_64-pc-linux-gnu/5.4.0/libasan.so.2+0x7015a)
    #1 0x4412dd in rule_matches /home/raj/rsync/rsync/exclude.c:696
    #2 0x441921 in check_filter /home/raj/rsync/rsync/exclude.c:772
    #3 0x441724 in name_is_excluded /home/raj/rsync/rsync/exclude.c:744
    #4 0x4a2d76 in receive_xattr /home/raj/rsync/rsync/xattrs.c:835
    #5 0x40beac in recv_file_entry /home/raj/rsync/rsync/flist.c:1108
    #6 0x415bee in recv_file_list /home/raj/rsync/rsync/flist.c:2476
    #7 0x454eaa in do_server_recv /home/raj/rsync/rsync/main.c:1036
    #8 0x4556f4 in start_server /home/raj/rsync/rsync/main.c:1115
    #9 0x4b20f2 in rsync_module /home/raj/rsync/rsync/clientserver.c:1007
    #10 0x4b2b11 in start_daemon /home/raj/rsync/rsync/clientserver.c:1135
    #11 0x48f636 in start_accept_loop /home/raj/rsync/rsync/socket.c:618
    #12 0x4b32d2 in daemon_main /home/raj/rsync/rsync/clientserver.c:1237
    #13 0x458318 in main /home/raj/rsync/rsync/main.c:1630
    #14 0x7ffff64d866f in __libc_start_main (/lib64/libc.so.6+0x2066f)
    #15 0x4047c8 in _start (/home/raj/rsync/asan/bin/rsync+0x4047c8)

0x60200000e831 is located 0 bytes to the right of 1-byte region
[0x60200000e830,0x60200000e831)
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 0x4a2c63 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 0x4b20f2 in rsync_module /home/raj/rsync/rsync/clientserver.c:1007
    #8 0x4b2b11 in start_daemon /home/raj/rsync/rsync/clientserver.c:1135
    #9 0x48f636 in start_accept_loop /home/raj/rsync/rsync/socket.c:618
    #10 0x4b32d2 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 strlen
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[01]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
==3497==ABORTING

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