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winpgnt: handle WM_COPYDATA requests in a subthread.

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This is preparation to allow Pageant to be able to return to its GUI
main loop in the middle of handling a request (e.g. present a dialog
box to the user related to that particular request, and wait for the
user's response). In order to do that, we need the main thread's
Windows message loop to never be blocked by a WM_COPYDATA agent
request.

So I've split Pageant's previous hidden window into two hidden
windows, each with a subset of the original roles, and created in
different threads so that they get independent message loops. The one
in the main thread receives messages relating to Pageant's system tray
icon; the one in the subthread has the identity known to (old) Pageant
clients, and receives WM_COPYDATA messages only. Each WM_COPYDATA is
handled by passing the request back to the main thread via an event
object integrated into the Pageant main loop, and then waiting for a
second event object that the main thread will signal when the answer
comes back, and not returning from the WndProc handler until the
response arrives.

Hence, if an agent request received via WM_COPYDATA requires GUI
activity, then the main thread's GUI message loop will be able to do
that in parallel with all Pageant's other activity, including other
GUI activity (like the key list dialog box) and including responding
to other requests via named pipe.

I can't stop WM_COPYDATA requests from blocking _each other_, but this
allows them not to block anything else. And named-pipe requests block
nothing at all, so as clients switch over to the new IPC, even that
blockage will become less and less common.
This commit is contained in:
Simon Tatham 2020-01-25 17:24:17 +00:00
parent 7590d0625b
commit 98538caa39
1 changed files with 105 additions and 54 deletions
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159
windows/winpgnt.c
View File

@ -51,6 +51,15 @@
#define APPNAME "Pageant"
/* Titles and class names for invisible windows. IPCWINTITLE and
* IPCCLASSNAME are critical to backwards compatibility: WM_COPYDATA
* based Pageant clients will call FindWindow with those parameters
* and expect to find the Pageant IPC receiver. */
#define TRAYWINTITLE "Pageant"
#define TRAYCLASSNAME "PageantSysTray"
#define IPCWINTITLE "Pageant"
#define IPCCLASSNAME "Pageant"
static HWND keylist;
static HWND aboutbox;
static HMENU systray_menu, session_menu;
@ -754,23 +763,30 @@ PSID get_default_sid(void)
}
#endif
struct PageantReply {
char *buf;
size_t size, len;
bool overflowed;
BinarySink_IMPLEMENTATION;
};
struct WmCopydataTransaction {
char *length, *body;
size_t bodysize, bodylen;
HANDLE ev_msg_ready, ev_reply_ready;
} wmct;
static void pageant_reply_BinarySink_write(
BinarySink *bs, const void *data, size_t len)
static void wm_copydata_got_msg(void *vctx)
{
struct PageantReply *rep = BinarySink_DOWNCAST(bs, struct PageantReply);
if (!rep->overflowed && len <= rep->size - rep->len) {
memcpy(rep->buf + rep->len, data, len);
rep->len += len;
} else {
rep->overflowed = true;
strbuf *sb = strbuf_new();
pageant_handle_msg(BinarySink_UPCAST(sb), wmct.body, wmct.bodylen,
NULL, NULL);
if (sb->len > wmct.bodysize) {
/* Output would overflow message buffer. Replace with a
* failure message. */
sb->len = 0;
put_byte(sb, SSH_AGENT_FAILURE);
assert(sb->len <= wmct.bodysize);
}
PUT_32BIT_MSB_FIRST(wmct.length, sb->len);
memcpy(wmct.body, sb->u, sb->len);
SetEvent(wmct.ev_reply_ready);
}
static char *answer_filemapping_message(const char *mapname)
@ -780,7 +796,6 @@ static char *answer_filemapping_message(const char *mapname)
char *err = NULL;
size_t mapsize;
unsigned msglen;
struct PageantReply reply;
#ifndef NO_SECURITY
PSID mapsid = NULL;
@ -789,7 +804,7 @@ static char *answer_filemapping_message(const char *mapname)
PSECURITY_DESCRIPTOR psd = NULL;
#endif
reply.buf = NULL;
wmct.length = wmct.body = NULL;
#ifdef DEBUG_IPC
debug("mapname = \"%s\"\n", mapname);
@ -892,42 +907,31 @@ static char *answer_filemapping_message(const char *mapname)
goto cleanup;
}
msglen = GET_32BIT_MSB_FIRST((unsigned char *)mapaddr);
wmct.length = (char *)mapaddr;
msglen = GET_32BIT_MSB_FIRST(wmct.length);
#ifdef DEBUG_IPC
debug("msg length=%08x, msg type=%02x\n",
msglen, (unsigned)((unsigned char *) mapaddr)[4]);
#endif
reply.buf = (char *)mapaddr + 4;
reply.size = mapsize - 4;
reply.len = 0;
reply.overflowed = false;
BinarySink_INIT(&reply, pageant_reply_BinarySink_write);
wmct.body = wmct.length + 4;
wmct.bodysize = mapsize - 4;
if (msglen > mapsize - 4) {
pageant_failure_msg(BinarySink_UPCAST(&reply),
"incoming length field too large", NULL, NULL);
if (msglen > wmct.bodysize) {
/* Incoming length field is too large. Emit a failure response
* without even trying to handle the request.
*
* (We know this must fit, because we checked mapsize >= 5
* above.) */
PUT_32BIT_MSB_FIRST(wmct.length, 1);
*wmct.body = SSH_AGENT_FAILURE;
} else {
pageant_handle_msg(BinarySink_UPCAST(&reply),
(unsigned char *)mapaddr + 4, msglen, NULL, NULL);
if (reply.overflowed) {
reply.len = 0;
reply.overflowed = false;
pageant_failure_msg(BinarySink_UPCAST(&reply),
"output would overflow message buffer",
NULL, NULL);
}
wmct.bodylen = msglen;
SetEvent(wmct.ev_msg_ready);
WaitForSingleObject(wmct.ev_reply_ready, INFINITE);
}
if (reply.overflowed) {
err = dupstr("even failure message overflows buffer");
goto cleanup;
}
/* Write in the initial length field, and we're done. */
PUT_32BIT_MSB_FIRST(((unsigned char *)mapaddr), reply.len);
cleanup:
/* expectedsid has the lifetime of the program, so we don't free it */
sfree(expectedsid_bc);
@ -940,8 +944,8 @@ static char *answer_filemapping_message(const char *mapname)
return err;
}
static LRESULT CALLBACK WndProc(HWND hwnd, UINT message,
WPARAM wParam, LPARAM lParam)
static LRESULT CALLBACK TrayWndProc(HWND hwnd, UINT message,
WPARAM wParam, LPARAM lParam)
{
static bool menuinprogress;
static UINT msgTaskbarCreated = 0;
@ -1079,6 +1083,15 @@ static LRESULT CALLBACK WndProc(HWND hwnd, UINT message,
quit_help(hwnd);
PostQuitMessage(0);
return 0;
}
return DefWindowProc(hwnd, message, wParam, lParam);
}
static LRESULT CALLBACK wm_copydata_WndProc(HWND hwnd, UINT message,
WPARAM wParam, LPARAM lParam)
{
switch (message) {
case WM_COPYDATA:
{
COPYDATASTRUCT *cds;
@ -1105,6 +1118,25 @@ static LRESULT CALLBACK WndProc(HWND hwnd, UINT message,
return DefWindowProc(hwnd, message, wParam, lParam);
}
static DWORD WINAPI wm_copydata_threadfunc(void *param)
{
HINSTANCE inst = *(HINSTANCE *)param;
HWND ipchwnd = CreateWindow(IPCCLASSNAME, IPCWINTITLE,
WS_OVERLAPPEDWINDOW | WS_VSCROLL,
CW_USEDEFAULT, CW_USEDEFAULT,
100, 100, NULL, NULL, inst, NULL);
ShowWindow(ipchwnd, SW_HIDE);
MSG msg;
while (GetMessage(&msg, NULL, 0, 0) == 1) {
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return 0;
}
/*
* Fork and Exec the command in cmdline. [DBW]
*/
@ -1146,7 +1178,6 @@ int flags = FLAG_SYNCAGENT;
int WINAPI WinMain(HINSTANCE inst, HINSTANCE prev, LPSTR cmdline, int show)
{
WNDCLASS wndclass;
MSG msg;
const char *command = NULL;
bool added_keys = false;
@ -1313,24 +1344,35 @@ int WINAPI WinMain(HINSTANCE inst, HINSTANCE prev, LPSTR cmdline, int show)
#endif /* !defined NO_SECURITY */
/*
* Set up window classes for two hidden windows: one that receives
* all the messages to do with our presence in the system tray,
* and one that receives the WM_COPYDATA message used by the
* old-style Pageant IPC system.
*/
if (!prev) {
wndclass.style = 0;
wndclass.lpfnWndProc = WndProc;
wndclass.cbClsExtra = 0;
wndclass.cbWndExtra = 0;
WNDCLASS wndclass;
memset(&wndclass, 0, sizeof(wndclass));
wndclass.lpfnWndProc = TrayWndProc;
wndclass.hInstance = inst;
wndclass.hIcon = LoadIcon(inst, MAKEINTRESOURCE(IDI_MAINICON));
wndclass.hCursor = LoadCursor(NULL, IDC_IBEAM);
wndclass.hbrBackground = GetStockObject(BLACK_BRUSH);
wndclass.lpszMenuName = NULL;
wndclass.lpszClassName = APPNAME;
wndclass.lpszClassName = TRAYCLASSNAME;
RegisterClass(&wndclass);
memset(&wndclass, 0, sizeof(wndclass));
wndclass.lpfnWndProc = wm_copydata_WndProc;
wndclass.hInstance = inst;
wndclass.lpszClassName = IPCCLASSNAME;
RegisterClass(&wndclass);
}
keylist = NULL;
hwnd = CreateWindow(APPNAME, APPNAME,
hwnd = CreateWindow(TRAYCLASSNAME, TRAYWINTITLE,
WS_OVERLAPPEDWINDOW | WS_VSCROLL,
CW_USEDEFAULT, CW_USEDEFAULT,
100, 100, NULL, NULL, inst, NULL);
@ -1364,6 +1406,13 @@ int WINAPI WinMain(HINSTANCE inst, HINSTANCE prev, LPSTR cmdline, int show)
ShowWindow(hwnd, SW_HIDE);
DWORD wm_copydata_threadid;
wmct.ev_msg_ready = CreateEvent(NULL, false, false, NULL);
wmct.ev_reply_ready = CreateEvent(NULL, false, false, NULL);
CreateThread(NULL, 0, wm_copydata_threadfunc,
&inst, 0, &wm_copydata_threadid);
handle_add_foreign_event(wmct.ev_msg_ready, wm_copydata_got_msg, NULL);
/*
* Main message loop.
*/
@ -1394,6 +1443,8 @@ int WINAPI WinMain(HINSTANCE inst, HINSTANCE prev, LPSTR cmdline, int show)
TranslateMessage(&msg);
DispatchMessage(&msg);
}
run_toplevel_callbacks();
}
finished: