gh-204: Support proxy environment variables

src/_native/bits.cpp

@@ -5,6 +5,7 @@
 #include <typeinfo>
 
 #include "helpers.h"
+#include "proxy.h"
 
 #ifdef BITS_INJECT_ERROR
 static HRESULT _inject_hr[]
@@ -205,7 +206,18 @@ PyObject *bits_serialize_job(PyObject *, PyObject *args, PyObject *kwargs) {
 }
 
 
-static HRESULT _job_setproxy(IBackgroundCopyJob *job) {
+static HRESULT _job_setproxy(IBackgroundCopyJob *job, const ProxySettings *settings) {
+    if (settings->mode == PROXY_MODE_DIRECT) {
+        return job->SetProxySettings(BG_JOB_PROXY_USAGE_NO_PROXY, NULL, NULL);
+    }
+    if (settings->mode == PROXY_MODE_OVERRIDE) {
+        return job->SetProxySettings(
+            BG_JOB_PROXY_USAGE_OVERRIDE,
+            settings->proxy_list,
+            NULL
+        );
+    }
+
     WINHTTP_CURRENT_USER_IE_PROXY_CONFIG proxy_config = { 0 };
     if (WinHttpGetIEProxyConfigForCurrentUser(&proxy_config)) {
         if (proxy_config.lpszProxy || proxy_config.lpszAutoConfigUrl || proxy_config.fAutoDetect) {
@@ -257,39 +269,50 @@ static HRESULT _job_setcredentials(
     return hr;
 }
 
-// (conn, name, url, path, [username], [password]) -> job
+// (conn, name, url, path, [username], [password], [proxy_settings]) -> job
 PyObject *bits_begin(PyObject *, PyObject *args, PyObject *kwargs) {
-    static const char * keywords[] = {"conn", "name", "url", "path", "username", "password", NULL};
+    static const char * keywords[] = {
+        "conn", "name", "url", "path", "username", "password", "proxy_settings", NULL
+    };
     IBackgroundCopyManager *bcm = NULL;
     wchar_t *name = NULL;
     wchar_t *url = NULL;
     wchar_t *path = NULL;
     wchar_t *username = NULL;
     wchar_t *password = NULL;
-    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "O&O&O&O&|O&O&:bits_begin", keywords,
+    PyObject *proxy_settings_obj = Py_None;
+    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "O&O&O&O&|O&O&O:bits_begin", keywords,
         from_capsule<IBackgroundCopyManager>, &bcm, as_utf16, &name, as_utf16, &url, as_utf16, &path,
-        as_utf16, &username, as_utf16, &password
+        as_utf16, &username, as_utf16, &password, &proxy_settings_obj
     )) {
         return NULL;
     }
 
     PyObject *r = NULL;
     GUID jobId;
     IBackgroundCopyJob* job = NULL;
+    ProxySettings proxy_settings = {};
     HRESULT hr;
+    if (!proxy_settings_parse(proxy_settings_obj, &proxy_settings)) {
+        goto done;
+    }
     if (FAILED(hr = _inject_hr[0])
         || FAILED(hr = bcm->CreateJob(name, BG_JOB_TYPE_DOWNLOAD, &jobId, &job))) {
         error_from_bits_hr(bcm, hr, "Creating download job");
         goto done;
     }
-    if (FAILED(hr = _job_setproxy(job))) {
+    if (FAILED(hr = _job_setproxy(job, &proxy_settings))) {
         error_from_bits_hr(bcm, hr, "Setting proxy");
         goto done;
     }
-    // Setting proxy credentials to NULL will automatically infer credentials
-    // if needed. It's a good default (provided users have not configured a
-    // malicious proxy server, which we can't do anything about here anyway).
-    if (FAILED(hr = _job_setcredentials(job, BG_AUTH_TARGET_PROXY, NULL, NULL))) {
+    // Explicit proxy credentials come from the configured proxy URL. NULL
+    // automatically infers credentials if needed, which remains the default.
+    if (FAILED(hr = _job_setcredentials(
+        job,
+        BG_AUTH_TARGET_PROXY,
+        proxy_settings.username,
+        proxy_settings.password
+    ))) {
         error_from_bits_hr(bcm, hr, "Setting proxy credentials");
         goto done;
     }
@@ -317,6 +340,7 @@ PyObject *bits_begin(PyObject *, PyObject *args, PyObject *kwargs) {
     if (job) {
         job->Release();
     }
+    proxy_settings_clear(&proxy_settings);
     PyMem_Free(path);
     PyMem_Free(url);
     PyMem_Free(name);

src/_native/proxy.cpp

@@ -0,0 +1,56 @@
+#include <Python.h>
+
+#include "helpers.h"
+#include "proxy.h"
+
+int proxy_settings_parse(PyObject *obj, ProxySettings *settings) {
+    settings->mode = PROXY_MODE_AUTO;
+    settings->proxy_list = NULL;
+    settings->username = NULL;
+    settings->password = NULL;
+
+    if (!obj || Py_Is(obj, Py_GetConstantBorrowed(Py_CONSTANT_NONE))) {
+        return 1;
+    }
+
+    int mode;
+    if (!PyArg_ParseTuple(
+        obj,
+        "iO&O&O&:proxy_settings",
+        &mode,
+        as_utf16, &settings->proxy_list,
+        as_utf16, &settings->username,
+        as_utf16, &settings->password
+    )) {
+        // PyArg_ParseTuple calls cleanup for successful O& converters when a
+        // later conversion fails, so these pointers no longer own memory.
+        settings->proxy_list = NULL;
+        settings->username = NULL;
+        settings->password = NULL;
+        return 0;
+    }
+
+    if (mode < PROXY_MODE_AUTO || mode > PROXY_MODE_OVERRIDE) {
+        PyErr_SetString(PyExc_ValueError, "invalid proxy mode");
+        proxy_settings_clear(settings);
+        return 0;
+    }
+    settings->mode = (ProxyMode)mode;
+
+    if (settings->mode == PROXY_MODE_OVERRIDE && !settings->proxy_list) {
+        PyErr_SetString(PyExc_ValueError, "proxy override requires a proxy list");
+        proxy_settings_clear(settings);
+        return 0;
+    }
+    return 1;
+}
+
+void proxy_settings_clear(ProxySettings *settings) {
+    PyMem_Free(settings->proxy_list);
+    PyMem_Free(settings->username);
+    PyMem_Free(settings->password);
+    settings->mode = PROXY_MODE_AUTO;
+    settings->proxy_list = NULL;
+    settings->username = NULL;
+    settings->password = NULL;
+}

src/_native/proxy.h

@@ -0,0 +1,19 @@
+#pragma once
+
+#include <Python.h>
+
+enum ProxyMode {
+    PROXY_MODE_AUTO = 0,
+    PROXY_MODE_DIRECT = 1,
+    PROXY_MODE_OVERRIDE = 2,
+};
+
+struct ProxySettings {
+    ProxyMode mode;
+    wchar_t *proxy_list;
+    wchar_t *username;
+    wchar_t *password;
+};
+
+int proxy_settings_parse(PyObject *obj, ProxySettings *settings);
+void proxy_settings_clear(ProxySettings *settings);

src/_native/winhttp.cpp

@@ -5,6 +5,7 @@
 #include <netlistmgr.h>
 
 #include "helpers.h"
+#include "proxy.h"
 
 #pragma comment(lib, "winhttp.lib")
 
@@ -191,7 +192,12 @@ extern "C" {
 #define CHECK_WINHTTP(x) if (!x) { winhttp_error(); goto exit; }
 
 
-static bool winhttp_apply_proxy(HINTERNET hSession, HINTERNET hRequest, const wchar_t *url) {
+static bool winhttp_apply_proxy(
+    HINTERNET hSession,
+    HINTERNET hRequest,
+    const wchar_t *url,
+    const ProxySettings *settings
+) {
     bool result = false;
     WINHTTP_CURRENT_USER_IE_PROXY_CONFIG proxy_config = { 0 };
     WINHTTP_AUTOPROXY_OPTIONS proxy_opt = {
@@ -200,6 +206,42 @@ static bool winhttp_apply_proxy(HINTERNET hSession, HINTERNET hRequest, const wc
     };
     WINHTTP_PROXY_INFO proxy_info = { 0 };
 
+    if (settings->mode == PROXY_MODE_DIRECT) {
+        // The session may have inherited a static WinHTTP proxy, so explicitly
+        // override it rather than relying on the absence of request settings.
+        proxy_info.dwAccessType = WINHTTP_ACCESS_TYPE_NO_PROXY;
+        CHECK_WINHTTP(WinHttpSetOption(
+            hRequest,
+            WINHTTP_OPTION_PROXY,
+            &proxy_info,
+            sizeof(proxy_info)
+        ));
+        result = true;
+        goto exit;
+    }
+
+    if (settings->mode == PROXY_MODE_OVERRIDE) {
+        proxy_info.dwAccessType = WINHTTP_ACCESS_TYPE_NAMED_PROXY;
+        proxy_info.lpszProxy = settings->proxy_list;
+
+        CHECK_WINHTTP(WinHttpSetCredentials(
+            hRequest,
+            WINHTTP_AUTH_TARGET_PROXY,
+            settings->username ? WINHTTP_AUTH_SCHEME_BASIC : WINHTTP_AUTH_SCHEME_NEGOTIATE,
+            settings->username,
+            settings->username ? settings->password : NULL,
+            NULL
+        ));
+        CHECK_WINHTTP(WinHttpSetOption(
+            hRequest,
+            WINHTTP_OPTION_PROXY,
+            &proxy_info,
+            sizeof(proxy_info)
+        ));
+        result = true;
+        goto exit;
+    }
+
     // First load the global-ish config settings
     if (!WinHttpGetIEProxyConfigForCurrentUser(&proxy_config)) {
         if (GetLastError() != ERROR_FILE_NOT_FOUND) {
@@ -248,10 +290,10 @@ static bool winhttp_apply_proxy(HINTERNET hSession, HINTERNET hRequest, const wc
 
     result = true;
 exit:
-    if (proxy_info.lpszProxy) {
+    if (settings->mode == PROXY_MODE_AUTO && proxy_info.lpszProxy) {
         GlobalFree((HGLOBAL)proxy_info.lpszProxy);
     }
-    if (proxy_info.lpszProxyBypass) {
+    if (settings->mode == PROXY_MODE_AUTO && proxy_info.lpszProxyBypass) {
         GlobalFree((HGLOBAL)proxy_info.lpszProxyBypass);
     }
     if (proxy_opt.lpszAutoConfigUrl) {
@@ -262,21 +304,26 @@ static bool winhttp_apply_proxy(HINTERNET hSession, HINTERNET hRequest, const wc
 
 
 PyObject *winhttp_urlopen(PyObject *, PyObject *args, PyObject *kwargs) {
-    static const char * keywords[] = {"url", "method", "headers", "accepts", "chunksize", "on_progress", "on_cred_request", NULL};
+    static const char * keywords[] = {
+        "url", "method", "headers", "accepts", "chunksize",
+        "on_progress", "on_cred_request", "proxy_settings", NULL
+    };
     wchar_t *url = NULL;
     wchar_t *method = NULL;
     wchar_t *headers = NULL;
     wchar_t *accepts = NULL;
     PyObject *on_progress = NULL;
     PyObject *on_cred_request = NULL;
+    PyObject *proxy_settings_obj = Py_None;
 
     PyObject *result = NULL;
     URL_COMPONENTS url_parts = { sizeof(URL_COMPONENTS) };
     HINTERNET hSession = NULL;
     HINTERNET hConnection = NULL;
     HINTERNET hRequest = NULL;
     DWORD opt = 0;
-    LPCWSTR *accepts_array;
+    LPCWSTR *accepts_array = NULL;
+    ProxySettings proxy_settings = {};
 
     Py_ssize_t chunksize = 65536;
     DWORD status_code = 0;
@@ -289,10 +336,14 @@ PyObject *winhttp_urlopen(PyObject *, PyObject *args, PyObject *kwargs) {
     wchar_t *user = NULL;
     wchar_t *pass = NULL;
 
-    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "O&O&O&O&|nOO:winhttp_urlopen", keywords,
-        as_utf16, &url, as_utf16, &method, as_utf16, &headers, as_utf16, &accepts, &chunksize, &on_progress, &on_cred_request)) {
+    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "O&O&O&O&|nOOO:winhttp_urlopen", keywords,
+        as_utf16, &url, as_utf16, &method, as_utf16, &headers, as_utf16, &accepts,
+        &chunksize, &on_progress, &on_cred_request, &proxy_settings_obj)) {
         return NULL;
     }
+    if (!proxy_settings_parse(proxy_settings_obj, &proxy_settings)) {
+        goto exit;
+    }
 
     if (on_progress && !PyObject_IsTrue(on_progress)) {
         on_progress = NULL;
@@ -370,7 +421,7 @@ PyObject *winhttp_urlopen(PyObject *, PyObject *args, PyObject *kwargs) {
     );
     CHECK_WINHTTP(hRequest);
 
-    CHECK_WINHTTP(winhttp_apply_proxy(hSession, hRequest, url));
+    CHECK_WINHTTP(winhttp_apply_proxy(hSession, hRequest, url, &proxy_settings));
 
     opt = WINHTTP_DECOMPRESSION_FLAG_ALL;
     CHECK_WINHTTP(WinHttpSetOption(
@@ -514,6 +565,7 @@ PyObject *winhttp_urlopen(PyObject *, PyObject *args, PyObject *kwargs) {
     }
     PyMem_Free(user);
     PyMem_Free(pass);
+    proxy_settings_clear(&proxy_settings);
     PyMem_Free(hostname);
     PyMem_Free(urlpath);
     PyMem_Free(accepts_array);
@@ -645,4 +697,4 @@ PyObject *winhttp_urlunsplit(PyObject *, PyObject *args, PyObject *kwargs) {
 }
 
 
-}
+}