[tor-commits] [tor/master] addr: Missing AF family to index conversion

[ahf at torproject.org]

commit ae6430818ee2786e2764bd6286aed311cdd77ab2
Author: David Goulet <dgoulet at torproject.org>
Date:   Thu Sep 3 11:54:22 2020 -0400

    addr: Missing AF family to index conversion
    
    When accessing the last_resolved_address cache we always need to convert the
    AF family value to an index value else we are out of bound and thus
    overflowing if we write to it.
    
    This fix is on code that has not been released.
    
    GeKo reported the following libasan crash using Tor Browser alpha with tor
    0.4.5.0-alpha-dev (3c884bc9e077e997):
    
    ==4240==ERROR: AddressSanitizer: global-buffer-overflow on address
    0x55888490e388 at pc 0x5588842cc216 bp 0x7ffc8c421b00 sp 0x7ffc8c421af8
    READ of size 2 at 0x55888490e388 thread T0
        #0 0x5588842cc215 in tor_addr_compare_masked
    (/home/thomas/Arbeit/Tor/tor-browser-build/tor-browser_en-US/Browser/TorBrowser/Tor/tor+0x5a6215)
        #1 0x558884203210 in is_local_to_resolve_addr
    (/home/thomas/Arbeit/Tor/tor-browser-build/tor-browser_en-US/Browser/TorBrowser/Tor/tor+0x4dd210)
        #2 0x558883f7e252 in channel_tls_connect
    (/home/thomas/Arbeit/Tor/tor-browser-build/tor-browser_en-US/Browser/TorBrowser/Tor/tor+0x258252)
        #3 0x558883f87ff7 in channel_connect_for_circuit
    (/home/thomas/Arbeit/Tor/tor-browser-build/tor-browser_en-US/Browser/TorBrowser/Tor/tor+0x261ff7)
        #4 0x558883f8bc90 in circuit_handle_first_hop
    (/home/thomas/Arbeit/Tor/tor-browser-build/tor-browser_en-US/Browser/TorBrowser/Tor/tor+0x265c90)
        #5 0x558883f8c891 in circuit_establish_circuit
    (/home/thomas/Arbeit/Tor/tor-browser-build/tor-browser_en-US/Browser/TorBrowser/Tor/tor+0x266891)
        #6 0x558883fc3bbc in circuit_launch_by_extend_info
    (/home/thomas/Arbeit/Tor/tor-browser-build/tor-browser_en-US/Browser/TorBrowser/Tor/tor+0x29dbbc)
        #7 0x558883fc5900
    (/home/thomas/Arbeit/Tor/tor-browser-build/tor-browser_en-US/Browser/TorBrowser/Tor/tor+0x29f900)
        #8 0x558883fc6988 in connection_ap_handshake_attach_circuit
    (/home/thomas/Arbeit/Tor/tor-browser-build/tor-browser_en-US/Browser/TorBrowser/Tor/tor+0x2a0988)
        #9 0x558883fd0d3f in connection_ap_attach_pending
    (/home/thomas/Arbeit/Tor/tor-browser-build/tor-browser_en-US/Browser/TorBrowser/Tor/tor+0x2aad3f)
        #10 0x7f4d50110885  (TorBrowser/Tor/libevent-2.1.so.7+0x22885)
        #11 0x7f4d501110de in event_base_loop
    (TorBrowser/Tor/libevent-2.1.so.7+0x230de)
        #12 0x558883f69b3c in do_main_loop
    (/home/thomas/Arbeit/Tor/tor-browser-build/tor-browser_en-US/Browser/TorBrowser/Tor/tor+0x243b3c)
        #13 0x558883f3f70c in tor_run_main
    (/home/thomas/Arbeit/Tor/tor-browser-build/tor-browser_en-US/Browser/TorBrowser/Tor/tor+0x21970c)
        #14 0x558883f3c2f7 in tor_main
    (/home/thomas/Arbeit/Tor/tor-browser-build/tor-browser_en-US/Browser/TorBrowser/Tor/tor+0x2162f7)
        #15 0x558883f3531b in main
    (/home/thomas/Arbeit/Tor/tor-browser-build/tor-browser_en-US/Browser/TorBrowser/Tor/tor+0x20f31b)
        #16 0x7f4d4f76acc9 in __libc_start_main
    (/lib/x86_64-linux-gnu/libc.so.6+0x26cc9)
        #17 0x558883f3ba00
    (/home/thomas/Arbeit/Tor/tor-browser-build/tor-browser_en-US/Browser/TorBrowser/Tor/tor+0x215a00)
    
    0x55888490e388 is located 24 bytes to the left of global variable
    'state_mgr' defined in 'src/app/config/statefile.c:184:22'
    (0x55888490e3a0) of size 8
    0x55888490e388 is located 32 bytes to the right of global variable
    'global_state' defined in 'src/app/config/statefile.c:204:20'
    (0x55888490e360) of size 8
    SUMMARY: AddressSanitizer: global-buffer-overflow
    (/home/thomas/Arbeit/Tor/tor-browser-build/tor-browser_en-US/Browser/TorBrowser/Tor/tor+0x5a6215)
    in tor_addr_compare_masked
    Shadow bytes around the buggy address:
      0x0ab190919c20: 00 f9 f9 f9 f9 f9 f9 f9 00 f9 f9 f9 f9 f9 f9 f9
      0x0ab190919c30: 04 f9 f9 f9 f9 f9 f9 f9 00 00 00 00 03 f9 f9 f9
      0x0ab190919c40: f9 f9 f9 f9 03 f9 f9 f9 f9 f9 f9 f9 00 00 00 00
      0x0ab190919c50: 00 00 00 04 f9 f9 f9 f9 00 00 00 00 00 00 00 04
      0x0ab190919c60: f9 f9 f9 f9 04 f9 f9 f9 f9 f9 f9 f9 00 f9 f9 f9
    =>0x0ab190919c70: f9[f9]f9 f9 00 f9 f9 f9 f9 f9 f9 f9 00 00 00 00
      0x0ab190919c80: 04 f9 f9 f9 f9 f9 f9 f9 04 f9 f9 f9 f9 f9 f9 f9
      0x0ab190919c90: 04 f9 f9 f9 f9 f9 f9 f9 04 f9 f9 f9 f9 f9 f9 f9
      0x0ab190919ca0: 00 00 00 00 00 f9 f9 f9 f9 f9 f9 f9 00 00 00 00
      0x0ab190919cb0: 01 f9 f9 f9 f9 f9 f9 f9 00 f9 f9 f9 f9 f9 f9 f9
      0x0ab190919cc0: 00 f9 f9 f9 f9 f9 f9 f9 00 f9 f9 f9 f9 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
    ==4240==ABORTING
    
    Signed-off-by: David Goulet <dgoulet at torproject.org>
---
 src/app/config/resolve_addr.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/app/config/resolve_addr.c b/src/app/config/resolve_addr.c
index a153d63974..b37707d2da 100644
--- a/src/app/config/resolve_addr.c
+++ b/src/app/config/resolve_addr.c
@@ -787,7 +787,8 @@ MOCK_IMPL(bool,
 is_local_to_resolve_addr, (const tor_addr_t *addr))
 {
   const int family = tor_addr_family(addr);
-  const tor_addr_t *last_resolved_addr = &last_resolved_addrs[family];
+  const tor_addr_t *last_resolved_addr =
+    &last_resolved_addrs[af_to_idx(family)];
 
   /* Internal address is always local. */
   if (tor_addr_is_internal(addr, 0)) {