Crashing net/microsocks if DNS being proxied

[Pavel Timofeev]

вс, 9 авг. 2020 г. в 16:30, Pavel Timofeev <timp87 at gmail.com>:

>
>  Pavel Timofeev <timp87 at gmail.com>:
>
>> Hello
>>
>> I'd like to take advantage of net/microsocks port - a small SOCKSv5
>> server.
>> It's v1.0.1 (https://github.com/rofl0r/microsocks/tree/v1.0.1) under
>> 12.1 RELEASE amd64.
>> It works OK with firefox until I ask firefox to proxy DNS via socks also.
>> It cashes after getaddrinfo() call.
>> I have quite poor C knowledge and I can't understand what's wrong with it.
>> Parameters passed to getaddrinfo() looks OK
>> Can anybody advise where to look at also?
>>
>>
>>
>> $ gdb92 microsocks microsocks.core
>>
>>
>> GNU gdb (GDB) 9.2 [GDB v9.2 for FreeBSD]
>>
>> Copyright (C) 2020 Free Software Foundation, Inc.
>>
>> License GPLv3+: GNU GPL version 3 or later <
>> http://gnu.org/licenses/gpl.html>
>>
>>
>> This is free software: you are free to change and redistribute it.
>>
>>
>> There is NO WARRANTY, to the extent permitted by law.
>>
>>
>> Type "show copying" and "show warranty" for details.
>>
>> This GDB was configured as "x86_64-portbld-freebsd12.1".
>>
>>
>> Type "show configuration" for configuration details.
>>
>> For bug reporting instructions, please see:
>>
>> <http://www.gnu.org/software/gdb/bugs/>.
>>
>> Find the GDB manual and other documentation resources online at:
>>
>>
>>     <http://www.gnu.org/software/gdb/documentation/>.
>>
>>
>>
>> For help, type "help".
>> Type "apropos word" to search for commands related to "word"...
>>
>>
>> Reading symbols from microsocks...
>>
>> [New LWP 100579]
>> [New LWP 100347]
>> Core was generated by `./microsocks'.
>>
>> Program terminated with signal SIGSEGV, Segmentation fault.
>>
>>
>> #0  0x00000008003e5467 in _getht (hostf=0x7fffdfffd238,
>> name=0x7fffdfffda20 "freebsd.org",
>>
>>
>>     pai=0x7fffdfffd5a0, cur=0x7fffdfffd240) at
>> /usr/src/lib/libc/net/getaddrinfo.c:2476
>>
>>
>> 2476    {
>> [Current thread is 1 (LWP 100579)]
>>
>> (gdb) bt
>> #0  0x00000008003e5467 in _getht (hostf=0x7fffdfffd238,
>> name=0x7fffdfffda20 "freebsd.org", pai=0x7fffdfffd5a0,
>> cur=0x7fffdfffd240) at /usr/src/lib/libc/net/getaddrinfo.c:2476
>> #1  0x00000008003e4990 in _files_getaddrinfo (rv=0x7fffdfffd670,
>> cb_data=<optimized out>, ap=<optimized out>) at
>> /usr/src/lib/libc/net/getaddrinfo.c:2515
>> #2  0x000000080040df6c in _nsdispatch (retval=0x7fffdfffd670,
>> disp_tab=0x8004482e0, database=<optimized out>, method_name=0x8002bafb7
>> "getaddrinfo", defaults=<optimized out>)
>>     at /usr/src/lib/libc/net/nsdispatch.c:716
>> #3  0x00000008003e30b3 in explore_fqdn (pai=0x1, hostname=<optimized
>> out>, servname=0x7fffdfffd860 "80", res=<optimized out>) at
>> /usr/src/lib/libc/net/getaddrinfo.c:1945
>> #4  getaddrinfo (hostname=<optimized out>, servname=0x7fffdfffd860 "80",
>> hints=<optimized out>, res=0x7fffdfffda18) at
>> /usr/src/lib/libc/net/getaddrinfo.c:576
>> #5  0x00000000002037f6 in resolve (host=0x7fffdfffda20 "freebsd.org",
>> port=80, addr=0x7fffdfffda18) at server.c:14
>> #6  0x00000000002030e8 in connect_socks_target (buf=0x7fffdfffdba0
>> "\005\001", n=18, client=0x800689038) at sockssrv.c:136
>> #7  0x00000000002029e3 in clientthread (data=0x800689030) at
>> sockssrv.c:317
>> #8  0x000000080025a736 in thread_start (curthread=0x800683500) at
>> /usr/src/lib/libthr/thread/thr_create.c:292
>> #9  0x0000000000000000 in ?? ()
>> Backtrace stopped: Cannot access memory at address 0x7fffdfffe000
>> (gdb) f 5
>> #5  0x00000000002037f6 in resolve (host=0x7fffdfffda20 "freebsd.org",
>> port=80, addr=0x7fffdfffda18) at server.c:14
>> 14              return getaddrinfo(host, port_buf, &hints, addr);
>> (gdb) p host
>> $1 = 0x7fffdfffda20 "freebsd.org"
>> (gdb) p port_buf
>> $2 = "80\000\000\b\000\000"
>> (gdb) p hints
>> $3 = {ai_flags = 1, ai_family = 0, ai_socktype = 1, ai_protocol = 0,
>> ai_addrlen = 0, ai_canonname = 0x0, ai_addr = 0x0, ai_next = 0x0}
>> (gdb) p *addr
>> $4 = (struct addrinfo *) 0x0
>> (gdb) list
>> 9                       .ai_socktype = SOCK_STREAM,
>> 10                      .ai_flags = AI_PASSIVE,
>> 11              };
>> 12              char port_buf[8];
>> 13              snprintf(port_buf, sizeof port_buf, "%u", port);
>> 14              return getaddrinfo(host, port_buf, &hints, addr);
>> 15      }
>> 16
>> 17      int server_bindtoip(const struct server *server, int fd) {
>> 18              if(server->bindaddr.v4.sin_family != AF_UNSPEC)
>>
>>
>>
>> However, it works OK under Linux no matter if DNS proxied or not.
>> Thank you!
>>
>
>
>
> I'm not asking for full debug session, just a few clues or an advice which
> way to dig probably.
>


Ahh, it fiddles with PTHREAD_STACK_MIN. It's the root cause.