http_proxy: Ignore TE and CL in CONNECT 2xx responses

A client MUST ignore any Content-Length or Transfer-Encoding header
fields received in a successful response to CONNECT.
"Successful" described as: 2xx (Successful). RFC 7231 4.3.6

Prior to this change such a case would cause an error.

In some ways this bug appears to be a regression since c50b878. Prior to
that libcurl may have appeared to function correctly in such cases by
acting on those headers instead of causing an error. But that behavior
was also incorrect.

Bug: https://github.com/curl/curl/issues/1317
Reported-by: mkzero@users.noreply.github.com

lib/http_proxy.c

@@ -515,34 +515,35 @@ CURLcode Curl_proxyCONNECT(struct connectdata *conn,
         }
         else if(checkprefix("Content-Length:", line_start)) {
           if(k->httpcode/100 == 2) {
-            /* A server MUST NOT send any Transfer-Encoding or
+            /* A client MUST ignore any Content-Length or Transfer-Encoding
-               Content-Length header fields in a 2xx (Successful)
+               header fields received in a successful response to CONNECT.
-               response to CONNECT. (RFC 7231 section 4.3.6) */
+               "Successful" described as: 2xx (Successful). RFC 7231 4.3.6 */
-            failf(data, "Content-Length: in %03d response",
+            infof(data, "Ignoring Content-Length in CONNECT %03d response\n",
                   k->httpcode);
-            return CURLE_RECV_ERROR;
           }
-
+          else {
             cl = curlx_strtoofft(line_start +
                                  strlen("Content-Length:"), NULL, 10);
           }
+        }
         else if(Curl_compareheader(line_start, "Connection:", "close"))
           closeConnection = TRUE;
-        else if(Curl_compareheader(line_start,
+        else if(checkprefix("Transfer-Encoding:", line_start)) {
-                                   "Transfer-Encoding:",
-                                   "chunked")) {
           if(k->httpcode/100 == 2) {
-            /* A server MUST NOT send any Transfer-Encoding or
+            /* A client MUST ignore any Content-Length or Transfer-Encoding
-               Content-Length header fields in a 2xx (Successful)
+               header fields received in a successful response to CONNECT.
-               response to CONNECT. (RFC 7231 section 4.3.6) */
+               "Successful" described as: 2xx (Successful). RFC 7231 4.3.6 */
-            failf(data, "Transfer-Encoding: in %03d response", k->httpcode);
+            infof(data, "Ignoring Transfer-Encoding in "
-            return CURLE_RECV_ERROR;
+                  "CONNECT %03d response\n", k->httpcode);
           }
+          else if(Curl_compareheader(line_start,
+                                     "Transfer-Encoding:", "chunked")) {
             infof(data, "CONNECT responded chunked\n");
             chunked_encoding = TRUE;
             /* init our chunky engine */
             Curl_httpchunk_init(conn);
           }
+        }
         else if(Curl_compareheader(line_start, "Proxy-Connection:", "close"))
           closeConnection = TRUE;
         else if(2 == sscanf(line_start, "HTTP/1.%d %d",

tests/data/Makefile.inc

@@ -131,7 +131,7 @@ test1244 test1245 test1246 test1247 test1248 test1249 test1250 test1251 \
 test1252 test1253 test1254 test1255 test1256 test1257 test1258 test1259 \
 test1260 \
 \
-test1280 test1281 test1282 test1283 test1284 test1285 test1286 \
+test1280 test1281 test1282 test1283 test1284 test1285 test1286 test1287 \
 \
 test1300 test1301 test1302 test1303 test1304 test1305 test1306 test1307 \
 test1308 test1309 test1310 test1311 test1312 test1313 test1314 test1315 \

tests/data/test1287

@@ -0,0 +1,90 @@
+<testcase>
+<info>
+<keywords>
+HTTP
+HTTP GET
+HTTP CONNECT
+proxytunnel
+</keywords>
+</info>
+#
+# Server-side
+<reply>
+<data>
+HTTP/1.1 200 OK
+Date: Thu, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake swsclose
+Content-Type: text/html
+Funny-head: yesyes
+Content-Length: 9
+
+contents
+</data>
+
+# The purpose of this test is to make sure curl ignores headers
+# Content-Length and Transfer-Encoding in a successful CONNECT 2xx reply.
+<connect>
+HTTP/1.1 200 Mighty fine indeed
+Content-Length: 123
+Transfer-Encoding: chunked
+
+</connect>
+
+<datacheck>
+HTTP/1.1 200 Mighty fine indeed
+Content-Length: 123
+Transfer-Encoding: chunked
+
+HTTP/1.1 200 OK
+Date: Thu, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake swsclose
+Content-Type: text/html
+Funny-head: yesyes
+Content-Length: 9
+
+contents
+</datacheck>
+</reply>
+
+#
+# Client-side
+<client>
+<server>
+http
+http-proxy
+</server>
+<name>
+HTTP over proxy-tunnel ignore TE and CL in CONNECT 2xx responses
+</name>
+<command>
+-v --proxytunnel -x %HOSTIP:%PROXYPORT http://test.1287:%HTTPPORT/we/want/that/page/1287
+</command>
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+<strip>
+^User-Agent:.*
+</strip>
+<proxy>
+CONNECT test.1287:%HTTPPORT HTTP/1.1
+Host: test.1287:%HTTPPORT
+Proxy-Connection: Keep-Alive
+
+</proxy>
+<protocol>
+GET /we/want/that/page/1287 HTTP/1.1
+Host: test.1287:%HTTPPORT
+Accept: */*
+
+</protocol>
+<file name="log/stderr1287" mode="text">
+* Ignoring Content-Length in CONNECT 200 response
+* Ignoring Transfer-Encoding in CONNECT 200 response
+</file>
+<stripfile>
+s/^.*(?=\* Ignoring (?:Content-Length|Transfer-Encoding) )// or $_ = ''
+</stripfile>
+</verify>
+</testcase>