Description

For 1Password Cloud Keychain plugin, the length of inputs are not properly checked. Then inputs are copied to fixed length buffers. For example, creating a salt with a larger length allow a buffer overflow.

Proof of Concept

Using the cloudkeychain.hash file:

$ ./run/john cloudkeychain.hash 
=================================================================
==103166==ERROR: AddressSanitizer: global-buffer-overflow on address 0x55f917d99688 at pc 0x55f9172ebbb6 bp 0x7fff28faa160 sp 0x7fff28faa150
WRITE of size 1 at 0x55f917d99688 thread T0
    #0 0x55f9172ebbb5 in get_salt /home/sylvain/software/john/src/cloudkeychain_fmt_plug.c:124
    #1 0x55f91751bd43 in ldr_load_pw_line /home/sylvain/software/john/src/loader.c:1045
    #2 0x55f91751883f in read_file /home/sylvain/software/john/src/loader.c:255
    #3 0x55f91751e8e0 in ldr_load_pw_file /home/sylvain/software/john/src/loader.c:1198
    #4 0x55f91750cf42 in john_load /home/sylvain/software/john/src/john.c:1134
    #5 0x55f91750cf42 in john_init /home/sylvain/software/john/src/john.c:1578
    #6 0x55f91750cf42 in main /home/sylvain/software/john/src/john.c:2065
    #7 0x7f5306c760b2 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x270b2)
    #8 0x55f916fe52cd in _start (/home/sylvain/software/john/run/john+0x1ee2cd)

0x55f917d99688 is located 56 bytes to the left of global variable 'cur_salt' defined in 'cloudkeychain_fmt_plug.c:77:28' (0x55f917d996c0) of size 8
0x55f917d99688 is located 0 bytes to the right of global variable 'cs' defined in 'cloudkeychain_fmt_plug.c:116:28' (0x55f917d97e00) of size 6280
SUMMARY: AddressSanitizer: global-buffer-overflow /home/sylvain/software/john/src/cloudkeychain_fmt_plug.c:124 in get_salt
Shadow bytes around the buggy address:
  0x0abfa2fab280: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0abfa2fab290: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0abfa2fab2a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0abfa2fab2b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0abfa2fab2c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0abfa2fab2d0: 00[f9]f9 f9 f9 f9 f9 f9 00 f9 f9 f9 f9 f9 f9 f9
  0x0abfa2fab2e0: 00 f9 f9 f9 f9 f9 f9 f9 00 f9 f9 f9 f9 f9 f9 f9
  0x0abfa2fab2f0: 00 00 00 00 00 00 00 00 00 00 00 00 01 f9 f9 f9
  0x0abfa2fab300: f9 f9 f9 f9 00 00 00 00 00 00 00 00 f9 f9 f9 f9
  0x0abfa2fab310: 00 f9 f9 f9 f9 f9 f9 f9 00 f9 f9 f9 f9 f9 f9 f9
  0x0abfa2fab320: 00 00 00 00 00 f9 f9 f9 f9 f9 f9 f9 00 f9 f9 f9
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
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  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
  Left alloca redzone:     ca
  Right alloca redzone:    cb
  Shadow gap:              cc
==103166==ABORTING

Impact

Buffer overflow may lead to exploiting the program, which can allow the attacker to execute arbitrary code.