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Posted to issues@trafficserver.apache.org by "Leif Hedstrom (JIRA)" <ji...@apache.org> on 2016/02/04 19:55:49 UTC
[jira] [Closed] (TS-3283) Certain SSL handshake error during
client-hello hangs the client and leaves network connection open
[ https://issues.apache.org/jira/browse/TS-3283?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Leif Hedstrom closed TS-3283.
-----------------------------
> Certain SSL handshake error during client-hello hangs the client and leaves network connection open
> ---------------------------------------------------------------------------------------------------
>
> Key: TS-3283
> URL: https://issues.apache.org/jira/browse/TS-3283
> Project: Traffic Server
> Issue Type: Bug
> Components: SSL
> Reporter: Joe Chung
> Assignee: Phil Sorber
> Fix For: 4.2.3
>
>
> h3. Problem Description
> Send an SSLv2 Client Hello with an old cipher suite request against Traffic Server 4.2.2, and the connection will freeze on the client side and eventually time out after 120 seconds.
> The Traffic Server detects the SSL error, but instead of closing the connection, goes on to accept new connections.
> h3. Reproduction
> === Client: Macbook Pro running OSX Mavericks 10.9.5 ===
> {code:none}
> $ openssl version -a
> OpenSSL 0.9.8za 5 Jun 2014
> built on: Aug 10 2014
> platform: darwin64-x86_64-llvm
> options: bn(64,64) md2(int) rc4(ptr,char) des(idx,cisc,16,int) blowfish(idx)
> compiler: -arch x86_64 -fmessage-length=0 -pipe -Wno-trigraphs -fpascal-strings -fasm-blocks -O3 -D_REENTRANT -DDSO_DLFCN -DHAVE_DLFCN_H -DL_ENDIAN -DMD32_REG_T=int -DOPENSSL_NO_IDEA -DOPENSSL_PIC -DOPENSSL_THREADS -DZLIB -mmacosx-version-min=10.6
> OPENSSLDIR: "/System/Library/OpenSSL"
> {code}
> h4. The following command triggers the bad behavior on the 4.2.2 server.
> {code:none}
> $ openssl s_client -connect 192.168.20.130:443 -ssl2 -debug
> CONNECTED(00000003)
> write to 0x7fb9f2508610 [0x7fb9f300f201] (45 bytes => 45 (0x2D))
> 0000 - 80 2b 01 00 02 00 12 00-00 00 10 07 00 c0 03 00 .+..............
> 0010 - 80 01 00 80 06 00 40 04-00 80 02 00 80 f4 71 1a ......@.......q.
> 0020 - ad 23 06 59 4d f8 d2 c5-b2 57 a9 66 4c .#.YM....W.fL
> ^C
> {code}
> At this point, the client is hung, and I have to hit ctrl-c to interrupt it or wait 120 seconds for tcp timeout.
> h3. Server: Lubuntu 13.10 on VMware
> {code:none}
> $ openssl version -a
> OpenSSL 1.0.1e 11 Feb 2013
> built on: Fri Jun 20 18:52:25 UTC 2014
> platform: debian-i386
> options: bn(64,32) rc4(8x,mmx) des(ptr,risc1,16,long) blowfish(idx)
> compiler: cc -fPIC -DOPENSSL_PIC -DZLIB -DOPENSSL_THREADS -D_REENTRANT -DDSO_DLFCN -DHAVE_DLFCN_H -DL_ENDIAN -DTERMIO -g -O2 -fstack-protector --param=ssp-buffer-size=4 -Wformat -Werror=format-security -D_FORTIFY_SOURCE=2 -Wl,-Bsymbolic-functions -Wl,-z,relro -Wa,--noexecstack -Wall -DOPENSSL_NO_TLS1_2_CLIENT -DOPENSSL_MAX_TLS1_2_CIPHER_LENGTH=50 -DOPENSSL_BN_ASM_PART_WORDS -DOPENSSL_IA32_SSE2 -DOPENSSL_BN_ASM_MONT -DOPENSSL_BN_ASM_GF2m -DSHA1_ASM -DSHA256_ASM -DSHA512_ASM -DMD5_ASM -DRMD160_ASM -DAES_ASM -DVPAES_ASM -DWHIRLPOOL_ASM -DGHASH_ASM
> OPENSSLDIR: "/usr/lib/ssl"
> {code}
> {code:none}
> $ diff /usr/local/etc/trafficserver/records.config.422 /usr/local/etc/trafficserver/records.config
> 113c113
> < CONFIG proxy.config.http.server_ports STRING 8080
> ---
> > CONFIG proxy.config.http.server_ports STRING 8080 443:ssl
> 594,595c594,595
> < CONFIG proxy.config.diags.debug.enabled INT 0
> < CONFIG proxy.config.diags.debug.tags STRING http.*|dns.*
> ---
> > CONFIG proxy.config.diags.debug.enabled INT 1
> > CONFIG proxy.config.diags.debug.tags STRING ssl.*
> {code}
> {code:none}
> $ /usr/local/bin/traffic_server --version
> [TrafficServer] using root directory '/usr/local'
> Apache Traffic Server - traffic_server - 4.2.2 - (build # 0723 on Jan 7 2015 at 23:04:32)
> $ sudo /usr/local/bin/traffic_server
> [sudo] password for user:
> [TrafficServer] using root directory '/usr/local'
> [Jan 8 00:53:42.618] Server {0xb702e700} DEBUG: (ssl) setting SNI callbacks with for ctx 0xa4a7928
> [Jan 8 00:53:42.618] Server {0xb702e700} DEBUG: (ssl) indexed '*' with SSL_CTX 0xa4a7928
> [Jan 8 00:53:42.619] Server {0xb702e700} DEBUG: (ssl) importing SNI names from /usr/local/etc/trafficserver
> [Jan 8 00:54:02.256] Server {0xb6265b40} DEBUG: (ssl) [SSLNextProtocolAccept:mainEvent] event 202 netvc 0xb280fa90
> [Jan 8 00:54:02.256] Server {0xb6265b40} DEBUG: (ssl) ssl_callback_info ssl: 0xb280fcb8 where: 16 ret: 1
> [Jan 8 00:54:02.256] Server {0xb6265b40} DEBUG: (ssl) ssl_callback_info ssl: 0xb280fcb8 where: 8193 ret: 1
> [Jan 8 00:54:02.256] Server {0xb6265b40} DEBUG: (ssl) ssl_callback_info ssl: 0xb280fcb8 where: 8194 ret: -1
> [Jan 8 00:54:02.256] Server {0xb6265b40} DEBUG: (ssl) SSL::3055967040:error:140760FC:SSL routines:SSL23_GET_CLIENT_HELLO:unknown protocol:s23_srvr.c:628
> [Jan 8 00:54:02.256] Server {0xb6265b40} DEBUG: <SSLNetVConnection.cc:526 (sslServerHandShakeEvent)> (ssl) SSL handshake error: SSL_ERROR_SSL (1), errno=0
> {code}
> At this point, the server has not closed the tcp connection, and has instead gone back to the accept loop, waiting for new connections.
> After 120 seconds (TCP timeout) the connection is eventually closed. During this time, the server process holds onto a file descriptor needlessly for 120 seconds. I connected to the server from multiple clients and counted the server's number of open fds after each connection ({{sudo ls -1 /proc/$pid/fd | wc -l}}).
> This behavior makes the server vulnerable to a denial-of-service attack.
> h3. Possible Fix
> In gdb, I compared the behavior of 5.1.2 vs 4.2.2 in the face of an {{SSL_ERROR_SSL}} during the Client Hello handshake. I noticed that in 5.1.2, there is a {{netvc->do_io(VIO::CLOSE)}} in {{SSLNextProtocolTrampoline::ioCompletionEvent()}} that closes the TCP connection.
> When I apply the following diff to the 4.2.2 code base (essentially making this function look more like the 5.1.2 version), it fixes the problem; i.e. the server immediately closes the TCP connection after the error is detected.
> {code:none}
> $ git diff
> diff --git a/iocore/net/SSLNextProtocolAccept.cc b/iocore/net/SSLNextProtocolAccept.cc
> index bfc2f0b..a5612c6 100644
> --- a/iocore/net/SSLNextProtocolAccept.cc
> +++ b/iocore/net/SSLNextProtocolAccept.cc
> @@ -78,19 +78,22 @@ struct SSLNextProtocolTrampoline : public Continuation
> Continuation * plugin;
> SSLNetVConnection * netvc;
> + vio = static_cast<VIO *>(edata);
> + netvc = dynamic_cast<SSLNetVConnection *>(vio->vc_server);
> + ink_assert(netvc != NULL);
> +
> switch (event) {
> case VC_EVENT_INACTIVITY_TIMEOUT:
> - case VC_EVENT_READ_COMPLETE:
> case VC_EVENT_ERROR:
> - vio = static_cast<VIO *>(edata);
> + netvc->do_io(VIO::CLOSE);
> + delete this;
> + return EVENT_CONT;
> + case VC_EVENT_READ_COMPLETE:
> break;
> default:
> return EVENT_ERROR;
> }
> - netvc = dynamic_cast<SSLNetVConnection *>(vio->vc_server);
> - ink_assert(netvc != NULL);
> -
> plugin = netvc->endpoint();
> if (plugin) {
> send_plugin_event(plugin, NET_EVENT_ACCEPT, netvc);
> {code}
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