You are viewing a plain text version of this content. The canonical link for it is here.
Posted to cvs@httpd.apache.org by jc...@apache.org on 2016/08/29 23:56:16 UTC
svn commit: r1758307 - in /httpd/httpd/trunk: CHANGES
docs/log-message-tags/next-number docs/manual/mod/core.xml server/core.c
server/mpm/winnt/child.c
Author: jchampion
Date: Mon Aug 29 23:56:16 2016
New Revision: 1758307
URL: http://svn.apache.org/viewvc?rev=1758307&view=rev
Log:
mpm_winnt: remove 'data' AcceptFilter in favor of 'connect'
The 'data' AcceptFilter optimization instructs Windows to wait until
data is received on a connection before completing the AcceptEx
operation. Unfortunately, it seems this isn't performed atomically --
AcceptEx "partially" accepts the incoming connection during the wait for
data, leaving all other incoming connections in the accept queue. This
opens the server to a denial of service.
Since the fix for this requires a substantial rearchitecture (likely
involving multiple outstanding calls to AcceptEx), disable the 'data'
filter for now and replace it with 'connect', which uses the AcceptEx
interface but does not wait for data.
Users running prior releases of httpd on Windows should explicitly move
to a 'connect' AcceptFilter in their configurations if they are
currently using the default 'data' filter.
Many thanks to mludha, Arthur Ramsey, Paul Spangler, and many others for
their assistance in tracking down and diagnosing this issue.
PR: 59970
Modified:
httpd/httpd/trunk/CHANGES
httpd/httpd/trunk/docs/log-message-tags/next-number
httpd/httpd/trunk/docs/manual/mod/core.xml
httpd/httpd/trunk/server/core.c
httpd/httpd/trunk/server/mpm/winnt/child.c
Modified: httpd/httpd/trunk/CHANGES
URL: http://svn.apache.org/viewvc/httpd/httpd/trunk/CHANGES?rev=1758307&r1=1758306&r2=1758307&view=diff
==============================================================================
--- httpd/httpd/trunk/CHANGES [utf-8] (original)
+++ httpd/httpd/trunk/CHANGES [utf-8] Mon Aug 29 23:56:16 2016
@@ -1,6 +1,9 @@
-*- coding: utf-8 -*-
Changes with Apache 2.5.0
+ *) mpm_winnt: Prevent a denial of service when the 'data' AcceptFilter is in
+ use by replacing it with the 'connect' filter. PR 59970. [Jacob Champion]
+
*) mod_cgid: Resolve a case where a short CGI response causes a subsequent
CGI to be killed prematurely, resulting in a truncated subsequent
response. [Eric Covener]
Modified: httpd/httpd/trunk/docs/log-message-tags/next-number
URL: http://svn.apache.org/viewvc/httpd/httpd/trunk/docs/log-message-tags/next-number?rev=1758307&r1=1758306&r2=1758307&view=diff
==============================================================================
--- httpd/httpd/trunk/docs/log-message-tags/next-number (original)
+++ httpd/httpd/trunk/docs/log-message-tags/next-number Mon Aug 29 23:56:16 2016
@@ -1 +1 @@
-3458
+3459
Modified: httpd/httpd/trunk/docs/manual/mod/core.xml
URL: http://svn.apache.org/viewvc/httpd/httpd/trunk/docs/manual/mod/core.xml?rev=1758307&r1=1758306&r2=1758307&view=diff
==============================================================================
--- httpd/httpd/trunk/docs/manual/mod/core.xml (original)
+++ httpd/httpd/trunk/docs/manual/mod/core.xml Mon Aug 29 23:56:16 2016
@@ -85,20 +85,15 @@ AcceptFilter https data
<p>The default values on Windows are:</p>
<highlight language="config">
-AcceptFilter http data
-AcceptFilter https data
+AcceptFilter http connect
+AcceptFilter https connect
</highlight>
<p>Window's mpm_winnt interprets the AcceptFilter to toggle the AcceptEx()
- API, and does not support http protocol buffering. There are two values
- which utilize the Windows AcceptEx() API and will recycle network
- sockets between connections. <code>data</code> waits until data has
- been transmitted as documented above, and the initial data buffer and
- network endpoint addresses are all retrieved from the single AcceptEx()
- invocation. <code>connect</code> will use the AcceptEx() API, also
- retrieve the network endpoint addresses, but like <code>none</code>
- the <code>connect</code> option does not wait for the initial data
- transmission.</p>
+ API, and does not support http protocol buffering. <code>connect</code>
+ will use the AcceptEx() API, also retrieve the network endpoint
+ addresses, but like <code>none</code> the <code>connect</code> option
+ does not wait for the initial data transmission.</p>
<p>On Windows, <code>none</code> uses accept() rather than AcceptEx()
and will not recycle sockets between connections. This is useful for
@@ -106,6 +101,22 @@ AcceptFilter https data
network providers such as vpn drivers, or spam, virus or spyware
filters.</p>
+ <note type="warning">
+ <title>The <code>data</code> AcceptFilter (Windows)</title>
+
+ <p>For versions 2.4.23 and prior, the Windows <code>data</code> accept
+ filter waited until data had been transmitted and the initial data
+ buffer and network endpoint addresses had been retrieved from the
+ single AcceptEx() invocation. This implementation was subject to a
+ denial of service attack and has been disabled.</p>
+
+ <p>Current releases of httpd default to the <code>connect</code> filter
+ on Windows, and will fall back to <code>connect</code> if
+ <code>data</code> is specified. Users of prior releases are encouraged
+ to add an explicit setting of <code>connect</code> for their
+ AcceptFilter, as shown above.</p>
+ </note>
+
</usage>
<seealso><directive module="core">Protocol</directive></seealso>
</directivesynopsis>
Modified: httpd/httpd/trunk/server/core.c
URL: http://svn.apache.org/viewvc/httpd/httpd/trunk/server/core.c?rev=1758307&r1=1758306&r2=1758307&view=diff
==============================================================================
--- httpd/httpd/trunk/server/core.c (original)
+++ httpd/httpd/trunk/server/core.c Mon Aug 29 23:56:16 2016
@@ -464,6 +464,10 @@ static void *create_core_server_config(a
#if APR_HAS_SO_ACCEPTFILTER
apr_table_setn(conf->accf_map, "http", ACCEPT_FILTER_NAME);
apr_table_setn(conf->accf_map, "https", "dataready");
+#elif defined(WIN32)
+ /* 'data' is disabled on Windows due to a DoS vuln (PR 59970) */
+ apr_table_setn(conf->accf_map, "http", "connect");
+ apr_table_setn(conf->accf_map, "https", "connect");
#else
apr_table_setn(conf->accf_map, "http", "data");
apr_table_setn(conf->accf_map, "https", "data");
Modified: httpd/httpd/trunk/server/mpm/winnt/child.c
URL: http://svn.apache.org/viewvc/httpd/httpd/trunk/server/mpm/winnt/child.c?rev=1758307&r1=1758306&r2=1758307&view=diff
==============================================================================
--- httpd/httpd/trunk/server/mpm/winnt/child.c (original)
+++ httpd/httpd/trunk/server/mpm/winnt/child.c Mon Aug 29 23:56:16 2016
@@ -323,8 +323,13 @@ static unsigned int __stdcall winnt_acce
"no known accept filter. Using 'none' instead",
lr->protocol);
}
- else if (strcmp(accf_name, "data") == 0)
- accf = 2;
+ else if (strcmp(accf_name, "data") == 0) {
+ accf = 1;
+ accf_name = "connect";
+ ap_log_error(APLOG_MARK, APLOG_INFO, 0, ap_server_conf,
+ APLOGNO(03458) "winnt_accept: 'data' accept filter is no "
+ "longer supported. Using 'connect' instead");
+ }
else if (strcmp(accf_name, "connect") == 0)
accf = 1;
else if (strcmp(accf_name, "none") == 0)
@@ -350,7 +355,7 @@ static unsigned int __stdcall winnt_acce
}
#endif
- if (accf > 0) /* 'data' or 'connect' */
+ if (accf > 0) /* 'connect' */
{
if (WSAIoctl(nlsd, SIO_GET_EXTENSION_FUNCTION_POINTER,
&GuidAcceptEx, sizeof GuidAcceptEx,
@@ -376,7 +381,7 @@ static unsigned int __stdcall winnt_acce
}
else /* accf == 0, 'none' */
{
-reinit: /* target of data or connect upon too many AcceptEx failures */
+reinit: /* target of connect upon too many AcceptEx failures */
/* last, low priority event is a not yet accepted connection */
events[0] = exit_event;
@@ -421,9 +426,8 @@ reinit: /* target of data or connect upo
}
}
- if (accf > 0) /* Either 'connect' or 'data' */
+ if (accf > 0) /* 'connect' */
{
- DWORD len;
char *buf;
/* Create and initialize the accept socket */
@@ -453,20 +457,12 @@ reinit: /* target of data or connect upo
continue;
}
- if (accf == 2) { /* 'data' */
- len = APR_BUCKET_BUFF_SIZE;
- buf = apr_bucket_alloc(len, context->ba);
- len -= PADDED_ADDR_SIZE * 2;
- }
- else /* (accf == 1) 'connect' */ {
- len = 0;
- buf = context->buff;
- }
+ buf = context->buff;
/* AcceptEx on the completion context. The completion context will be
* signaled when a connection is accepted.
*/
- if (!lpfnAcceptEx(nlsd, context->accept_socket, buf, len,
+ if (!lpfnAcceptEx(nlsd, context->accept_socket, buf, 0,
PADDED_ADDR_SIZE, PADDED_ADDR_SIZE, &BytesRead,
&context->overlapped)) {
rv = apr_get_netos_error();
@@ -476,8 +472,6 @@ reinit: /* target of data or connect upo
* 1) the client disconnects early
* 2) handshake was incomplete
*/
- if (accf == 2)
- apr_bucket_free(buf);
closesocket(context->accept_socket);
context->accept_socket = INVALID_SOCKET;
continue;
@@ -492,8 +486,6 @@ reinit: /* target of data or connect upo
* 3) the dynamic address / adapter has changed
* Give five chances, then fall back on AcceptFilter 'none'
*/
- if (accf == 2)
- apr_bucket_free(buf);
closesocket(context->accept_socket);
context->accept_socket = INVALID_SOCKET;
++err_count;
@@ -513,8 +505,6 @@ reinit: /* target of data or connect upo
}
else if ((rv != APR_FROM_OS_ERROR(ERROR_IO_PENDING)) &&
(rv != APR_FROM_OS_ERROR(WSA_IO_PENDING))) {
- if (accf == 2)
- apr_bucket_free(buf);
closesocket(context->accept_socket);
context->accept_socket = INVALID_SOCKET;
++err_count;
@@ -555,14 +545,10 @@ reinit: /* target of data or connect upo
/* exit_event triggered or event handle was closed */
closesocket(context->accept_socket);
context->accept_socket = INVALID_SOCKET;
- if (accf == 2)
- apr_bucket_free(buf);
break;
}
if (context->accept_socket == INVALID_SOCKET) {
- if (accf == 2)
- apr_bucket_free(buf);
continue;
}
}
@@ -585,28 +571,11 @@ reinit: /* target of data or connect upo
/* Get the local & remote address
* TODO; error check
*/
- lpfnGetAcceptExSockaddrs(buf, len, PADDED_ADDR_SIZE, PADDED_ADDR_SIZE,
+ lpfnGetAcceptExSockaddrs(buf, 0, PADDED_ADDR_SIZE, PADDED_ADDR_SIZE,
&context->sa_server, &context->sa_server_len,
&context->sa_client, &context->sa_client_len);
- /* For 'data', craft a bucket for our data result
- * and pass to worker_main as context->overlapped.Pointer
- */
- if (accf == 2 && BytesRead)
- {
- apr_bucket *b;
- b = apr_bucket_heap_create(buf, APR_BUCKET_BUFF_SIZE,
- apr_bucket_free, context->ba);
- /* Adjust the bucket to refer to the actual bytes read */
- b->length = BytesRead;
- context->overlapped.Pointer = b;
- }
- else {
- if (accf == 2) {
- apr_bucket_free(buf);
- }
- context->overlapped.Pointer = NULL;
- }
+ context->overlapped.Pointer = NULL;
}
else /* (accf = 0) e.g. 'none' */
{