http: Fix Host header in proxied https connections

Currently CONNECT requests use the name of the proxy as Host value, instead of
the origin server's name.

According to RFC 2616 "The Host field value MUST represent the naming authority
of the origin server or gateway given by the original URL."

The current implementation causes problems with some proxy vendors. This
commit fixes this.

[jak: Adding a test case]
See merge request apt-team/apt!66

(cherry picked from commit 86d4d98060)
LP: #1838771

methods/http.cc

@@ -320,14 +320,14 @@ static ResultState UnwrapHTTPConnect(std::string Host, int Port, URI Proxy, std:
    std::string ProperHost;
 
    if (Host.find(':') != std::string::npos)
-      ProperHost = '[' + Proxy.Host + ']';
+      ProperHost = '[' + Host + ']';
    else
-      ProperHost = Proxy.Host;
+      ProperHost = Host;
 
    // Build the connect
    Req << "CONNECT " << Host << ":" << std::to_string(Port) << " HTTP/1.1\r\n";
    if (Proxy.Port != 0)
-      Req << "Host: " << ProperHost << ":" << std::to_string(Proxy.Port) << "\r\n";
+      Req << "Host: " << ProperHost << ":" << std::to_string(Port) << "\r\n";
    else
       Req << "Host: " << ProperHost << "\r\n";
 

test/integration/test-proxy-connect

@@ -0,0 +1,22 @@
+#!/bin/sh
+set -e
+
+TESTDIR="$(readlink -f "$(dirname "$0")")"
+. "$TESTDIR/framework"
+setupenvironment
+configarchitecture 'amd64'
+
+buildsimplenativepackage 'unrelated' 'all' '0.5~squeeze1' 'unstable'
+
+setupaptarchive
+changetowebserver --request-absolute='uri'
+
+
+msgmsg 'Check that host header we send for CONNECT is for target, not proxy'
+echo "deb https://example.example/ example example" > rootdir/etc/apt/sources.list
+rm -f rootdir/etc/apt/sources.list.d/*
+echo "Acquire::http::Proxy \"http://localhost:${APTHTTPPORT}\";" > rootdir/etc/apt/apt.conf.d/99proxy
+
+aptget update >/dev/null 2>&1
+testsuccessequal "CONNECT example.example:443 HTTP/1.1\r
+Host: example.example:443\r" grep -A1 "^CONNECT" aptarchive/webserver.log