qgs: add -m=MODE parameter for UNIX socket mode

The UNIX socket mode default is controlled by the process umask, but it
can be desirable to override this to open up the socket mode, while
keeping the umask restrictive.

For example, to allow QEMU to connect to the socket, it needs to be
world accessible, while the default umask of 0700 set by systemd
will normally limit its access to only the qgs user.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

Author: berrange

QuoteGeneration/quote_wrapper/qgs/server_main.cpp

@@ -73,9 +73,10 @@ int main(int argc, const char* argv[])
     bool no_daemon = false;
     unsigned long int port = 0;
     unsigned long int num_threads = 0;
+    unsigned long int mode = 0;
     char *endptr = NULL;
     if (argc > 4) {
-        cout << "Usage: " << argv[0] << "[--no-daemon] [-p=port_number] [-n=number_threads]"
+        cout << "Usage: " << argv[0] << "[--no-daemon] [-p=port_number] [-m=unix_socket_mode] [-n=number_threads]"
              << endl;
         exit(1);
     }
@@ -100,6 +101,19 @@ int main(int argc, const char* argv[])
             }
             cout << "port number [" << port << "] found in cmdline" << endl;
             continue;
+        } else if (strncmp(argv[i], "-m=", 3 ) == 0) {
+            if (strspn(argv[i] + 3, "0123456789") != strlen(argv[i] + 3)) {
+                cout << "Please input valid socket mode" << endl;
+                exit(1);
+            }
+            errno = 0;
+            mode = strtoul(argv[i] + 3, &endptr, 8);
+            if (errno || strlen(endptr) || (mode > UINT_MAX) ) {
+                cout << "Please input valid socket mode" << endl;
+                exit(1);
+            }
+            cout << "socket mode [" << mode << "] found in cmdline" << endl;
+            continue;
         } else if (strncmp(argv[i], "-n=", 3) == 0) {
             if (strspn(argv[i] + 3, "0123456789") != strlen(argv[i] + 3)) {
                 cout << "Please input valid thread number" << endl;
@@ -114,7 +128,7 @@ int main(int argc, const char* argv[])
             cout << "thread number [" << num_threads << "] found in cmdline" << endl;
             continue;
         } else {
-            cout << "Usage: " << argv[0] << "[--no-daemon] [-p=port_number] [-n=number_threads]"
+            cout << "Usage: " << argv[0] << "[--no-daemon] [-p=port_number] [-m=unix_socket_mode] [-n=number_threads]"
                 << endl;
             exit(1);
         }
@@ -123,7 +137,7 @@ int main(int argc, const char* argv[])
 
     // Use the port number in QGS_CONFIG_FILE if no valid port number on
     // command line
-    if (port == 0 || num_threads == 0) {
+    if (port == 0 || num_threads == 0 || mode == 0) {
         ifstream config_file(QGS_CONFIG_FILE);
         if (config_file.is_open()) {
             string line;
@@ -155,6 +169,15 @@ int main(int argc, const char* argv[])
                              << QGS_CONFIG_FILE << endl;
                         exit(1);
                     }
+                } else if (!mode && name.compare("socket_mode") == 0) {
+                    errno = 0;
+                    endptr = NULL;
+                    mode = strtoul(value, &endptr, 8);
+                    if (errno || strlen(endptr) || (mode > UINT_MAX)) {
+                        cout << "Please input valid socket mode in "
+                             << QGS_CONFIG_FILE << endl;
+                        exit(1);
+                    }
                 } else if (!num_threads && name.compare("number_threads") == 0) {
                     errno = 0;
                     endptr = NULL;
@@ -203,6 +226,12 @@ int main(int argc, const char* argv[])
             } else {
                 asio::local::stream_protocol::endpoint unix_ep(QGS_UNIX_SOCKET_FILE);
                 ep = unix_ep;
+		/* Allow mode to be determined by umask by default,
+		 * overriding only if an explicit mode is requested
+		 */
+		if (mode != 0) {
+                    chmod(QGS_UNIX_SOCKET_FILE, mode);
+		}
             }
             QGS_LOG_INFO("About to create QgsServer with num_thread = %d\n", (uint8_t)num_threads);
             server = new QgsServer(io_service, ep, (uint8_t)num_threads);