[From nobody Thu Mar 19 22:01:05 2026 Received: (at submit) by bugs.debian.org; 1 Oct 2019 11:39:29 +0000 X-Spam-Checker-Version: SpamAssassin 3.4.2-bugs.debian.org_2005_01_02 (2018-09-13) on buxtehude.debian.org X-Spam-Level: X-Spam-Status: No, score=-21.7 required=4.0 tests=BAYES_00,DIGITS_LETTERS, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FOURLA,HAS_PACKAGE, RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_PASS,TXREP,XMAILER_REPORTBUG, X_DEBBUGS_CC autolearn=ham autolearn_force=no version=3.4.2-bugs.debian.org_2005_01_02 X-Spam-Bayes: score:0.0000 Tokens: new, 58; hammy, 150; neutral, 245; spammy, 0. spammytokens: hammytokens:0.000-+--H*M:reportbug, 0.000-+--H*MI:reportbug, 0.000-+--H*x:reportbug, 0.000-+--H*UA:reportbug, 0.000-+--sysv Return-path: <dkg@fifthhorseman.net> Received: from che.mayfirst.org ([162.247.75.118]:40347) by buxtehude.debian.org with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from <dkg@fifthhorseman.net>) id 1iFGV7-0006AE-AS for submit@bugs.debian.org; 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Tue, 1 Oct 2019 07:39:25 -0400 (EDT) Received: by fifthhorseman.net (Postfix, from userid 1000) id EDB9020466; Tue, 1 Oct 2019 13:39:22 +0200 (CEST) Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit From: Daniel Kahn Gillmor <dkg@fifthhorseman.net> To: Debian Bug Tracking System <submit@bugs.debian.org> Subject: torsocks: nc.openbsd in tight loop when talking to tor via libtorsocks Message-ID: <156992996292.20038.16150638350008834146.reportbug@alice.fifthhorseman.net> X-Mailer: reportbug 7.5.3 Date: Tue, 01 Oct 2019 07:39:22 -0400 X-Debbugs-Cc: dkg@fifthhorseman.net Delivered-To: submit@bugs.debian.org Package: torsocks Version: 2.3.0-2+b1 Severity: normal Control: affects + netcat-openbsd On my system right now, nc is in a tight loop, burning 100% CPU: ``` 0 dkg@alice:~$ strace -p 10348 -T -ttt 2>&1 | head strace: Process 10348 attached 1569928260.402113 select(4, [3], NULL, NULL, NULL) = 1 (in [3]) <0.000020> 1569928260.402195 recvfrom(3, "", 10, 0, NULL, NULL) = 0 <0.000015> 1569928260.402300 select(4, [3], NULL, NULL, NULL) = 1 (in [3]) <0.000008> 1569928260.402351 recvfrom(3, "", 10, 0, NULL, NULL) = 0 <0.000007> 1569928260.402394 select(4, [3], NULL, NULL, NULL) = 1 (in [3]) <0.000007> 1569928260.402436 recvfrom(3, "", 10, 0, NULL, NULL) = 0 <0.000006> 1569928260.402477 select(4, [3], NULL, NULL, NULL) = 1 (in [3]) <0.000007> 1569928260.402517 recvfrom(3, "", 10, 0, NULL, NULL) = 0 <0.000006> 1569928260.402558 select(4, [3], NULL, NULL, NULL) = 1 (in [3]) <0.000007> 0 dkg@alice:~$ lsof -p 10348 COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME nc 10348 dkg cwd DIR 254,3 24576 261633 /home/dkg nc 10348 dkg rtd DIR 254,1 4096 2 / nc 10348 dkg txt REG 254,1 43504 135774 /bin/nc.openbsd nc 10348 dkg mem REG 254,1 51696 141113 /lib/x86_64-linux-gnu/libnss_files-2.29.so nc 10348 dkg mem REG 254,1 14592 138268 /lib/x86_64-linux-gnu/libdl-2.29.so nc 10348 dkg mem REG 254,1 1820104 135133 /lib/x86_64-linux-gnu/libc-2.29.so nc 10348 dkg mem REG 254,1 84808 141227 /lib/x86_64-linux-gnu/libresolv-2.29.so nc 10348 dkg mem REG 254,1 96568 5752 /usr/lib/x86_64-linux-gnu/libbsd.so.0.10.0 nc 10348 dkg mem REG 254,1 88160 133186 /usr/lib/x86_64-linux-gnu/torsocks/libtorsocks.so.0.0.0 nc 10348 dkg mem REG 254,1 165632 131306 /lib/x86_64-linux-gnu/ld-2.29.so nc 10348 dkg 0r FIFO 0,12 0t0 8164325 pipe nc 10348 dkg 1w FIFO 0,12 0t0 8164326 pipe nc 10348 dkg 2u CHR 136,14 0t0 17 /dev/pts/14 nc 10348 dkg 3u IPv4 8165435 0t0 TCP localhost:48380->localhost:9050 (CLOSE_WAIT) 0 dkg@alice:~$ ``` It was invoked as part of an ssh proxycommand: torsocks nc jsjr752kjv5evcwv.onion 22 (onion service name is anonymized here) I tried using ltrace on the same process, but nothing was emitted -- it's doing this loop without crossing any dynamic linker boundaries. With torsocks-dbgsym and netcat-openbsd-dbgsym installed, and gdb attached to the process, i see this backtrace: ``` #0 0x00007fb931222187 in __GI___select (nfds=nfds@entry=4, readfds=readfds@entry=0x7fffa2739eb0, writefds=writefds@entry=0x0, exceptfds=exceptfds@entry=0x0, timeout=timeout@entry=0x0) at ../sysdeps/unix/sysv/linux/select.c:41 #1 0x00007fb931359623 in wait_on_fd (fd=3) at socks5.c:40 #2 0x00007fb931359838 in recv_data_impl (fd=3, buf=0x7fffa273a070, len=<optimized out>) at socks5.c:69 #3 0x00007fb93135a2b0 in socks5_recv_connect_reply (conn=conn@entry=0x55ca81f32340) at socks5.c:509 #4 0x00007fb931352fca in tsocks_connect_to_tor (conn=conn@entry=0x55ca81f32340) at torsocks.c:500 #5 0x00007fb9313539e1 in tsocks_connect (sockfd=<optimized out>, addr=0x55ca81f32320, addrlen=16) at connect.c:206 #6 0x000055ca80745a7c in connect_with_timeout (ctimeout=<optimized out>, salen=16, sa=0x55ca81f32320, fd=3) at netcat.c:1277 #7 remote_connect (host=0x7fffa273ba37 "jsjr752kjv5evcwv.onion", port=0x55ca81f321c0 "22", hints=...) at netcat.c:1203 #8 0x000055ca80743ce0 in main (argc=<optimized out>, argv=<optimized out>) at netcat.c:878 (gdb) ``` Thanks for maintaining torsocks in debian! --dkg -- System Information: Debian Release: bullseye/sid APT prefers testing-debug APT policy: (500, 'testing-debug'), (500, 'testing'), (500, 'stable'), (500, 'oldstable'), (200, 'unstable-debug'), (200, 'unstable'), (1, 'experimental-debug'), (1, 'experimental') Architecture: amd64 (x86_64) Kernel: Linux 5.2.0-2-amd64 (SMP w/4 CPU cores) Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=en_US.UTF-8 (charmap=UTF-8) Shell: /bin/sh linked to /bin/dash Init: systemd (via /run/systemd/system) Versions of packages torsocks depends on: ii libc6 2.29-2 Versions of packages torsocks recommends: ii tor 0.4.1.6-1 torsocks suggests no packages. -- no debconf information ]