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Full request-line sent with http2 #3570

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bungle opened this issue Feb 14, 2019 · 4 comments

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@bungle
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commented Feb 14, 2019

I did this

curl -x http://example.test:8000/ http://www.example.org:1234/ \
     --http2-prior-knowledge -v

and from that I got this (the relevant part only):

> GET http://www.example.org:1234/ HTTP/2
> Host: www.example.org:1234

Which my Nginx server terminated with:

2019/02/14 [info] client sent invalid :path header: "http://www.example.org:1234/"
                  while reading client request headers

I expected the following

With http2 the client should not send other than path+query with the request line as it is not supported with http2.

I expected:

> GET / HTTP/2
> Host: www.example.org:1234

curl/libcurl version

url 7.63.0 (x86_64-apple-darwin16.7.0) libcurl/7.63.0 OpenSSL/1.0.2q zlib/1.2.8
                                       libidn2/2.1.0 nghttp2/1.35.1
Release-Date: 2018-12-12
Protocols: dict file ftp ftps gopher http https imap imaps ldap ldaps pop3
           pop3s rtsp smb smbs smtp smtps telnet tftp 
Features: AsynchDNS IDN IPv6 Largefile NTLM NTLM_WB SSL libz TLS-SRP
          HTTP2 UnixSockets HTTPS-proxy 

operating system

macOS Sierra 10.12.6

@jay

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commented Feb 16, 2019

Is this allowed or supported in http2? libcurl reports a PROTOCOL_ERROR and nginx 1.10.3 server /var/log/nginx/error.log shows nothing.

curl/lib/http.c

Lines 2513 to 2530 in f3294d9

/* url */
if(conn->bits.httpproxy && !conn->bits.tunnel_proxy) {
char *url = data->change.url;
result = Curl_add_buffer(&req_buffer, url, strlen(url));
}
else if(paste_ftp_userpwd)
result = Curl_add_bufferf(&req_buffer, "ftp://%s:%s@%s",
conn->user, conn->passwd,
path + sizeof("ftp://") - 1);
else {
result = Curl_add_buffer(&req_buffer, path, strlen(path));
if(result)
return result;
if(query)
result = Curl_add_bufferf(&req_buffer, "?%s", query);
}
if(result)
return result;

If I change it to conn->httpversion != 20 then I can get it working [1] so it's possible. It looks like custom host headers would have to be ignored (or sent as actual :host?) to ensure that the actual host is always sent as :authority? I don't know the best way to address this so I tried it parsing the url in http2.c rather than try to predict or have logic whether or not we're at http2 elsewhere...feels wrong though

diff --git a/lib/http2.c b/lib/http2.c
index 2884c71..5dd943e 100644
--- a/lib/http2.c
+++ b/lib/http2.c
@@ -1835,7 +1835,7 @@ static ssize_t http2_send(struct connectdata *conn, int sockindex,
   nghttp2_nv *nva = NULL;
   size_t nheader;
   size_t i;
-  size_t authority_idx;
+  size_t authority_idx, path_idx, scheme_idx;
   char *hdbuf = (char *)mem;
   char *end, *line_end;
   nghttp2_data_provider data_prd;
@@ -1947,6 +1947,7 @@ static ssize_t http2_send(struct connectdata *conn, int sockindex,
   }
   if(!end || end == hdbuf)
     goto fail;
+  path_idx = 1;
   nva[1].name = (unsigned char *)":path";
   nva[1].namelen = strlen((char *)nva[1].name);
   nva[1].value = (unsigned char *)hdbuf;
@@ -1957,6 +1958,7 @@ static ssize_t http2_send(struct connectdata *conn, int sockindex,
     goto fail;
   }
 
+  scheme_idx = 2;
   nva[2].name = (unsigned char *)":scheme";
   nva[2].namelen = strlen((char *)nva[2].name);
   if(conn->handler->flags & PROTOPT_SSL)
@@ -2030,6 +2032,50 @@ static ssize_t http2_send(struct connectdata *conn, int sockindex,
     ++i;
   }
 
+  /* hack to fix http proxy over http2 */
+  if(conn->bits.httpproxy && !conn->bits.tunnel_proxy) {
+    if(!authority_idx || !path_idx || !scheme_idx) {
+      failf(conn->data, "http2 missing pseudo-headers for proxy modification");
+      goto fail;
+    }
+    for(i = 0; i < nva[path_idx].valuelen; ++i) {
+      if(nva[path_idx].value[i] == ':') {
+        if(i + 2 < nva[path_idx].valuelen &&
+           nva[path_idx].value[i+1] == '/' &&
+           nva[path_idx].value[i+2] == '/')
+          break;
+        else {
+          failf(conn->data, "http2 bad scheme in path for proxy modification");
+          goto fail;
+        }
+      }
+    }
+    if(i == 0 || i == nva[path_idx].valuelen) {
+      failf(conn->data, "http2 missing scheme in path for proxy modification");
+      goto fail;
+    }
+    nva[scheme_idx].valuelen = &nva[path_idx].value[i] -
+                               nva[path_idx].value;
+    nva[scheme_idx].value = nva[path_idx].value;
+    nva[path_idx].valuelen -= &nva[path_idx].value[i+3] -
+                              nva[path_idx].value;
+    nva[path_idx].value = &nva[path_idx].value[i+3];
+    for(i = 0; i < nva[path_idx].valuelen; ++i) {
+      if(nva[path_idx].value[i] == '/')
+        break;
+    }
+    if(i == 0 || i == nva[path_idx].valuelen) {
+      failf(conn->data, "http2 missing host in path for proxy modification");
+      goto fail;
+    }
+    nva[authority_idx].valuelen = &nva[path_idx].value[i] -
+                                  nva[path_idx].value;
+    nva[authority_idx].value = nva[path_idx].value;
+    nva[path_idx].valuelen -= &nva[path_idx].value[i] -
+                              nva[path_idx].value;
+    nva[path_idx].value = &nva[path_idx].value[i];
+  }
+
   /* :authority must come before non-pseudo header fields */
   if(authority_idx != 0 && authority_idx != AUTHORITY_DST_IDX) {
     nghttp2_nv authority = nva[authority_idx];

(Patch now up at branch jay:http2_proxy)

[1]: I used a crude setup of nginx as a forward proxy with appended http2 to the listen line, added a proxy_set_header Proxy-Connection ""; and put it in /etc/nginx/sites-available/default and then restarted the server sudo systemctl reload nginx.service

@bagder

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commented Feb 16, 2019

I think the primary explanation for this flaw is the outstanding item in the TODO:

"Support HTTP/2 for HTTP(S) proxies"

This simply hasn't been made to work (yet)!

jay added a commit to jay/curl that referenced this issue Feb 16, 2019

http2: hack to fix http proxy over http2. draft1
- Parse the scheme, host and path from the :path component and then
  use that information to update the respective pseudo-headers.

http2.c constructs an http2 request by parsing a regular http request
that has been constructed in http.c. Normally this request has the
path as the request-uri field (ie /foo in GET /foo HTTP/1.1) so that is
what is used for http2 pseudo-header :path. However in the case of an
http proxy libcurl uses the full URL as the request-uri field
(ie http://test.com/foo in GET http://test.com/foo HTTP/1.1) so that
is not just :path but must be split into :scheme and :authority (host)
which is what this patch does. A side effect of this is that any
user-specified host field is overridden.

Ref: curl#3570 (comment)
Ref: https://curl.haxx.se/docs/todo.html#Support_HTTP_2_for_HTTP_S_proxi
@daurnimator

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commented Mar 13, 2019

I also ran into this today.

Noted at nghttp2/nghttp2#1304 (comment)

I'm not entirely sure what the behaviour here is meant to be, so in lua-http I added: https://github.com/daurnimator/lua-http/pull/141/files#diff-b4a19dcf32626be03ed2854d0f44ff8eR457

@bagder

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commented Apr 16, 2019

I close this issue now and refer to the TODO issue again for our still outstanding task to add HTTP/2 support for proxies. The --http2-prior-knowledge option is intended for talking to the server, and doing this over a HTTP/1 proxy I don't think can ever be made to work.

@jay's comments and work above can certainly serve as the beginning of this support, but should be submitted as a regular PR instead when ripe and we can then discuss its merits and the details then.

@bagder bagder closed this Apr 16, 2019

jay added a commit to jay/curl that referenced this issue May 8, 2019

http: Ignore HTTP/2 prior knowledge setting for HTTP proxies
- Do not switch to HTTP/2 for an HTTP proxy that is not tunnelling to
  the destination host.

We already do something similar for HTTPS proxies by not sending h2. [1]

Prior to this change setting CURL_HTTP_VERSION_2_PRIOR_KNOWLEDGE would
incorrectly use HTTP/2 to talk to the proxy, which is not something we
support (yet?). Also it's debatable whether or not that setting should
apply to HTTP/2 proxies.

[1]: curl@17c5d05

Bug: curl#3570
Bug: curl#3832

Closes #xxxx

jay added a commit that referenced this issue May 9, 2019

http: Ignore HTTP/2 prior knowledge setting for HTTP proxies
- Do not switch to HTTP/2 for an HTTP proxy that is not tunnelling to
  the destination host.

We already do something similar for HTTPS proxies by not sending h2. [1]

Prior to this change setting CURL_HTTP_VERSION_2_PRIOR_KNOWLEDGE would
incorrectly use HTTP/2 to talk to the proxy, which is not something we
support (yet?). Also it's debatable whether or not that setting should
apply to HTTP/2 proxies.

[1]: 17c5d05

Bug: #3570
Bug: #3832

Closes #3853

@lock lock bot locked as resolved and limited conversation to collaborators Jul 15, 2019

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