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Fall back on WinINET proxy settings if WinHTTP proxy is not defined
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Implement the recommended behaviour for "well-written WinHTTP apps", see
https://blogs.msdn.microsoft.com/ieinternals/2013/10/11/understanding-web-proxy-configuration/

I.e. use IE proxy settings for the current user unless WinHTTP proxy is
explicitly defined (which seems to be quite rare in practice). This makes
applications using C++ REST SDK work out of the box on the networks where IE
is configured to access the Internet (which will almost always be the case),
whether via a fixed proxy or using proxy-configuration, using either WPAD or
fixed PAC URL (this fixes #182
in passing).
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@vadz
vadz committed Jul 8, 2017
1 parent c24bc6a commit eb108ad
Showing 1 changed file with 85 additions and 6 deletions.
91 changes: 85 additions & 6 deletions Release/src/http/client/http_client_winhttp.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -297,7 +297,7 @@ static DWORD ChooseAuthScheme( DWORD dwSupportedSchemes )
return 0;
}

// Small RAII helper to ensure that the fields of this struct are always
// Small RAII helpers to ensure that the fields of these structs are always
// properly freed.
struct proxy_info : WINHTTP_PROXY_INFO
{
Expand All @@ -315,6 +315,24 @@ struct proxy_info : WINHTTP_PROXY_INFO
}
};

struct ie_proxy_config : WINHTTP_CURRENT_USER_IE_PROXY_CONFIG
{
ie_proxy_config()
{
memset( this, 0, sizeof(WINHTTP_CURRENT_USER_IE_PROXY_CONFIG) );
}

~ie_proxy_config()
{
if ( lpszAutoConfigUrl )
::GlobalFree(lpszAutoConfigUrl);
if ( lpszProxy )
::GlobalFree(lpszProxy);
if ( lpszProxyBypass )
::GlobalFree(lpszProxyBypass);
}
};

// WinHTTP client.
class winhttp_client : public _http_client_communicator
{
Expand Down Expand Up @@ -376,8 +394,13 @@ class winhttp_client : public _http_client_communicator
// Open session and connection with the server.
virtual unsigned long open() override
{
// This object have lifetime greater than proxy_name and proxy_bypass
// which may point to its elements.
ie_proxy_config proxyIE;

DWORD access_type;
LPCWSTR proxy_name;
LPCWSTR proxy_bypass = WINHTTP_NO_PROXY_BYPASS;
utility::string_t proxy_str;
http::uri uri;

Expand All @@ -388,10 +411,51 @@ class winhttp_client : public _http_client_communicator
access_type = WINHTTP_ACCESS_TYPE_NO_PROXY;
proxy_name = WINHTTP_NO_PROXY_NAME;
}
else if(config.proxy().is_default() || config.proxy().is_auto_discovery())
else if(config.proxy().is_default())
{
// Use the default WinHTTP proxy by default.
access_type = WINHTTP_ACCESS_TYPE_DEFAULT_PROXY;
proxy_name = WINHTTP_NO_PROXY_NAME;

// However, if it is not configured...
proxy_info proxyDefault;
if(!WinHttpGetDefaultProxyConfiguration(&proxyDefault) ||
proxyDefault.dwAccessType == WINHTTP_ACCESS_TYPE_NO_PROXY)
{
// ... then try to fall back on the default WinINET proxy, as
// recommended for the desktop applications (if we're not
// running under a user account, the function below will just
// fail, so there is no real need to check for this explicitly)
if(WinHttpGetIEProxyConfigForCurrentUser(&proxyIE))
{
if(proxyIE.fAutoDetect)
{
m_proxy_auto_config = true;
}
else if(proxyIE.lpszAutoConfigUrl)
{
m_proxy_auto_config = true;
m_proxy_auto_config_url = proxyIE.lpszAutoConfigUrl;
}
else if(proxyIE.lpszProxy)
{
access_type = WINHTTP_ACCESS_TYPE_NAMED_PROXY;
proxy_name = proxyIE.lpszProxy;

if(proxyIE.lpszProxyBypass)
{
proxy_bypass = proxyIE.lpszProxyBypass;
}
}
}
}
}
else if(config.proxy().is_auto_discovery())
{
access_type = WINHTTP_ACCESS_TYPE_DEFAULT_PROXY;
proxy_name = WINHTTP_NO_PROXY_NAME;

m_proxy_auto_config = true;
}
else
{
Expand Down Expand Up @@ -426,7 +490,7 @@ class winhttp_client : public _http_client_communicator
NULL,
access_type,
proxy_name,
WINHTTP_NO_PROXY_BYPASS,
proxy_bypass,
WINHTTP_FLAG_ASYNC);
if(!m_hSession)
{
Expand Down Expand Up @@ -513,13 +577,22 @@ class winhttp_client : public _http_client_communicator
proxy_info info;
bool proxy_info_required = false;

if( client_config().proxy().is_auto_discovery() )
if(m_proxy_auto_config)
{
WINHTTP_AUTOPROXY_OPTIONS autoproxy_options;
memset( &autoproxy_options, 0, sizeof(WINHTTP_AUTOPROXY_OPTIONS) );

autoproxy_options.dwFlags = WINHTTP_AUTOPROXY_AUTO_DETECT;
autoproxy_options.dwAutoDetectFlags = WINHTTP_AUTO_DETECT_TYPE_DHCP | WINHTTP_AUTO_DETECT_TYPE_DNS_A;
if(m_proxy_auto_config_url.empty())
{
autoproxy_options.dwFlags = WINHTTP_AUTOPROXY_AUTO_DETECT;
autoproxy_options.dwAutoDetectFlags = WINHTTP_AUTO_DETECT_TYPE_DHCP | WINHTTP_AUTO_DETECT_TYPE_DNS_A;
}
else
{
autoproxy_options.dwFlags = WINHTTP_AUTOPROXY_CONFIG_URL;
autoproxy_options.lpszAutoConfigUrl = m_proxy_auto_config_url.c_str();
}

autoproxy_options.fAutoLogonIfChallenged = TRUE;

auto result = WinHttpGetProxyForUrl(
Expand Down Expand Up @@ -1370,6 +1443,12 @@ class winhttp_client : public _http_client_communicator
HINTERNET m_hSession;
HINTERNET m_hConnection;
bool m_secure;

// If auto config is true, dynamically find the proxy for each URL using
// the proxy configuration script at the given URL if it's not empty or
// using WPAD otherwise.
bool m_proxy_auto_config{false};
utility::string_t m_proxy_auto_config_url;
};

std::shared_ptr<_http_client_communicator> create_platform_final_pipeline_stage(uri&& base_uri, http_client_config&& client_config)
Expand Down

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