Windows: use the named pipe for normal agent queries.

As in the previous commit, this means that agent_query() is now able
to operate in an asynchronous mode, so that if Pageant takes time to
answer a request, the GUI of the PuTTY instance making the request
won't be blocked.

Also as in the previous commit, we still fall back to the WM_COPYDATA
protocol if the new named pipe protocol isn't available.

Recipe

@@ -341,7 +341,7 @@ pageant  : [G] winpgnt pageant sshrsa sshpubk sshdes ARITH sshmd5 version
 	 + tree234 MISC sshaes sshsha winsecur winpgntc aqsync sshdss sshsh256
 	 + sshsh512 winutils sshecc winmisc winmiscs winhelp conf pageant.res
 	 + sshauxcrypt sshhmac wincapi winnps winnpc winhsock errsock winnet
-	 + winhandl callback be_misc winselgui LIBS
+	 + winhandl callback be_misc winselgui winhandl LIBS
 
 puttygen : [G] winpgen sshrsag sshdssg sshprime sshdes ARITH sshmd5 version
          + sshrand winnoise sshsha winstore MISC winctrls sshrsa sshdss winmisc

windows/winpgntc.c

@@ -16,7 +16,7 @@
 
 #define AGENT_COPYDATA_ID 0x804e50ba   /* random goop */
 
-bool agent_exists(void)
+static bool wm_copydata_agent_exists(void)
 {
     HWND hwnd;
     hwnd = FindWindow("Pageant", "Pageant");
@@ -26,14 +26,7 @@ bool agent_exists(void)
         return true;
 }
 
-void agent_cancel_query(agent_pending_query *q)
-{
-    unreachable("Windows agent queries are never asynchronous!");
-}
-
-agent_pending_query *agent_query(
-    strbuf *query, void **out, int *outlen,
-    void (*callback)(void *, void *, int), void *callback_ctx)
+static void wm_copydata_agent_query(strbuf *query, void **out, int *outlen)
 {
     HWND hwnd;
     char *mapname;
@@ -49,11 +42,11 @@ agent_pending_query *agent_query(
     *outlen = 0;
 
     if (query->len > AGENT_MAX_MSGLEN)
-        return NULL;                   /* query too large */
+        return;                        /* query too large */
 
     hwnd = FindWindow("Pageant", "Pageant");
     if (!hwnd)
-        return NULL;                   /* *out == NULL, so failure */
+        return;                        /* *out == NULL, so failure */
     mapname = dupprintf("PageantRequest%08x", (unsigned)GetCurrentThreadId());
 
     psa = NULL;
@@ -94,7 +87,7 @@ agent_pending_query *agent_query(
                                 0, AGENT_MAX_MSGLEN, mapname);
     if (filemap == NULL || filemap == INVALID_HANDLE_VALUE) {
         sfree(mapname);
-        return NULL;                   /* *out == NULL, so failure */
+        return;                        /* *out == NULL, so failure */
     }
     p = MapViewOfFile(filemap, FILE_MAP_WRITE, 0, 0, 0);
     strbuf_finalise_agent_query(query);
@@ -134,7 +127,6 @@ agent_pending_query *agent_query(
     sfree(mapname);
     if (psd)
         LocalFree(psd);
-    return NULL;
 }
 
 #ifndef NO_SECURITY
@@ -173,6 +165,159 @@ void agent_free_connect_ctx(agent_connect_ctx *ctx)
     sfree(ctx);
 }
 
+static bool named_pipe_agent_exists(void)
+{
+    char *pipename = agent_named_pipe_name();
+    DWORD type = GetFileType(pipename);
+    sfree(pipename);
+    return type == FILE_TYPE_PIPE;
+}
+
+bool agent_exists(void)
+{
+    return named_pipe_agent_exists() || wm_copydata_agent_exists();
+}
+
+struct agent_pending_query {
+    struct handle *handle;
+    strbuf *response;
+    void (*callback)(void *, void *, int);
+    void *callback_ctx;
+};
+
+static int named_pipe_agent_accumulate_response(
+    strbuf *sb, const void *data, size_t len)
+{
+    put_data(sb, data, len);
+    if (sb->len >= 4) {
+        uint32_t length_field = GET_32BIT_MSB_FIRST(sb->u);
+        if (length_field > AGENT_MAX_MSGLEN)
+            return -1; /* badly formatted message */
+
+        int overall_length = length_field + 4;
+        if (sb->len >= overall_length)
+            return overall_length;
+    }
+
+    return 0; /* not done yet */
+}
+
+static size_t named_pipe_agent_gotdata(
+    struct handle *h, const void *data, size_t len, int err)
+{
+    agent_pending_query *pq = handle_get_privdata(h);
+
+    if (err || len == 0) {
+        pq->callback(pq->callback_ctx, NULL, 0);
+        agent_cancel_query(pq);
+    }
+
+    int status = named_pipe_agent_accumulate_response(pq->response, data, len);
+    if (status == -1) {
+        pq->callback(pq->callback_ctx, NULL, 0);
+        agent_cancel_query(pq);
+    } else if (status > 0) {
+        void *response_buf = strbuf_to_str(pq->response);
+        pq->response = NULL;
+        pq->callback(pq->callback_ctx, response_buf, status);
+        agent_cancel_query(pq);
+    }
+    return 0;
+}
+
+agent_pending_query *named_pipe_agent_query(
+    strbuf *query, void **out, int *outlen,
+    void (*callback)(void *, void *, int), void *callback_ctx)
+{
+    agent_pending_query *pq = NULL;
+    char *err = NULL, *pipename = NULL;
+    strbuf *sb = NULL;
+    HANDLE pipehandle;
+
+    pipename = agent_named_pipe_name();
+    pipehandle = connect_to_named_pipe(pipename, &err);
+    if (pipehandle == INVALID_HANDLE_VALUE)
+        goto failure;
+
+    strbuf_finalise_agent_query(query);
+
+    for (DWORD done = 0; done < query->len ;) {
+        DWORD nwritten;
+        bool ret = WriteFile(pipehandle, query->s + done, query->len - done,
+                             &nwritten, NULL);
+        if (!ret)
+            goto failure;
+
+        done += nwritten;
+    }
+
+    if (!callback) {
+        int status;
+
+        sb = strbuf_new_nm();
+        do {
+            char buf[1024];
+            DWORD nread;
+            bool ret = ReadFile(pipehandle, buf, sizeof(buf), &nread, NULL);
+            if (!ret)
+                goto failure;
+            status = named_pipe_agent_accumulate_response(sb, buf, nread);
+        } while (status == 0);
+
+        if (status == -1)
+            goto failure;
+
+        *out = strbuf_to_str(sb);
+        *outlen = status;
+        sb = NULL;
+        pq = NULL;
+        goto out;
+    }
+
+    pq = snew(agent_pending_query);
+    pq->handle = handle_input_new(pipehandle, named_pipe_agent_gotdata, pq, 0);
+    pipehandle = NULL;  /* prevent it being closed below */
+    pq->response = strbuf_new_nm();
+    pq->callback = callback;
+    pq->callback_ctx = callback_ctx;
+    goto out;
+
+  failure:
+    *out = NULL;
+    *outlen = 0;
+    pq = NULL;
+
+  out:
+    sfree(err);
+    sfree(pipename);
+    if (pipehandle != INVALID_HANDLE_VALUE)
+        CloseHandle(pipehandle);
+    if (sb)
+        strbuf_free(sb);
+    return pq;
+}
+
+void agent_cancel_query(agent_pending_query *pq)
+{
+    handle_free(pq->handle);
+    if (pq->response)
+        strbuf_free(pq->response);
+    sfree(pq);
+}
+
+agent_pending_query *agent_query(
+    strbuf *query, void **out, int *outlen,
+    void (*callback)(void *, void *, int), void *callback_ctx)
+{
+    agent_pending_query *pq = named_pipe_agent_query(
+        query, out, outlen, callback, callback_ctx);
+    if (pq || *out)
+        return pq;
+
+    wm_copydata_agent_query(query, out, outlen);
+    return NULL;
+}
+
 #else /* NO_SECURITY */
 
 Socket *agent_connect(void *vctx, Plug *plug)
@@ -189,4 +334,22 @@ void agent_free_connect_ctx(agent_connect_ctx *ctx)
 {
 }
 
+bool agent_exists(void)
+{
+    return wm_copydata_agent_exists();
+}
+
+agent_pending_query *agent_query(
+    strbuf *query, void **out, int *outlen,
+    void (*callback)(void *, void *, int), void *callback_ctx)
+{
+    wm_copydata_agent_query(query, out, outlen);
+    return NULL;
+}
+
+void agent_cancel_query(agent_pending_query *q)
+{
+    unreachable("Windows agent queries are never asynchronous!");
+}
+
 #endif /* NO_SECURITY */