From: Jacob Champion Date: Mon, 29 Aug 2016 23:56:16 +0000 (+0000) Subject: mpm_winnt: remove 'data' AcceptFilter in favor of 'connect' X-Git-Tag: 2.5.0-alpha~1180 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f533af4b28a4438829f09ef360319d315ec8396f;p=thirdparty%2Fapache%2Fhttpd.git 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 git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1758307 13f79535-47bb-0310-9956-ffa450edef68 --- diff --git a/CHANGES b/CHANGES index d8ed6944b14..3b1f57ca099 100644 --- a/CHANGES +++ b/CHANGES @@ -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] diff --git a/docs/log-message-tags/next-number b/docs/log-message-tags/next-number index a82b2ee2a70..c4b489825b3 100644 --- a/docs/log-message-tags/next-number +++ b/docs/log-message-tags/next-number @@ -1 +1 @@ -3458 +3459 diff --git a/docs/manual/mod/core.xml b/docs/manual/mod/core.xml index 56a1f672b3b..a5ae5830b4d 100644 --- a/docs/manual/mod/core.xml +++ b/docs/manual/mod/core.xml @@ -85,20 +85,15 @@ AcceptFilter https data

The default values on Windows are:

-AcceptFilter http data -AcceptFilter https data +AcceptFilter http connect +AcceptFilter https connect

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. data 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. connect will use the AcceptEx() API, also - retrieve the network endpoint addresses, but like none - the connect option does not wait for the initial data - transmission.

+ API, and does not support http protocol buffering. connect + will use the AcceptEx() API, also retrieve the network endpoint + addresses, but like none the connect option + does not wait for the initial data transmission.

On Windows, none 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.

+ + The <code>data</code> AcceptFilter (Windows) + +

For versions 2.4.23 and prior, the Windows data 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.

+ +

Current releases of httpd default to the connect filter + on Windows, and will fall back to connect if + data is specified. Users of prior releases are encouraged + to add an explicit setting of connect for their + AcceptFilter, as shown above.

+ + Protocol diff --git a/server/core.c b/server/core.c index 92b2fc4b59d..75e9218eeed 100644 --- a/server/core.c +++ b/server/core.c @@ -464,6 +464,10 @@ static void *create_core_server_config(apr_pool_t *a, server_rec *s) #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"); diff --git a/server/mpm/winnt/child.c b/server/mpm/winnt/child.c index e9a71905160..321a0240d81 100644 --- a/server/mpm/winnt/child.c +++ b/server/mpm/winnt/child.c @@ -323,8 +323,13 @@ static unsigned int __stdcall winnt_accept(void *lr_) "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_accept(void *lr_) } #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_accept(void *lr_) } 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 upon too many AcceptEx failures */ } } - 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 upon too many AcceptEx failures */ 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 upon too many AcceptEx failures */ * 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 upon too many AcceptEx failures */ * 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 upon too many AcceptEx failures */ } 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 upon too many AcceptEx failures */ /* 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 upon too many AcceptEx failures */ /* 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' */ {