--x11=xephyr rewrite

1 files changed, 103 insertions, 44 deletions

diff --git a/src/firejail/x11.c b/src/firejail/x11.c
index 090ff6f3b..9e818ab67 100644
--- a/src/firejail/x11.c
+++ b/src/firejail/x11.c
@@ -158,16 +158,15 @@ void fs_x11(void) {
 
 
 #ifdef HAVE_X11
-//$ Xephyr -ac -br -terminate -screen 800x600 :22 &
+//$ Xephyr -ac -br -noreset -screen 800x600 :22 &
 //$ DISPLAY=:22 firejail --net=eth0 --blacklist=/tmp/.X11-unix/x0 firefox
 void x11_start_xephyr(int argc, char **argv) {
         EUID_ASSERT();
-        int i;
+        size_t i;
         struct stat s;
         pid_t client = 0;
         pid_t server = 0;
         
-
         setenv("FIREJAIL_X11", "yes", 1);
 
         // unfortunately, xephyr does a number of weird things when started by root user!!!
@@ -186,29 +185,78 @@ void x11_start_xephyr(int argc, char **argv) {
         }
         
         int display = random_display_number();
+        char *display_str;
+        if (asprintf(&display_str, ":%d", display) == -1)
+                errExit("asprintf");
 
-        // start xephyr
-        char *cmd1;
+        assert(xephyr_screen);
+        char *server_argv[256] = { "Xephyr", "-ac", "-br", "-noreset", "-screen", xephyr_screen }; // rest initialyzed to NULL
+        unsigned pos = 0;
+        while (server_argv[pos] != NULL) pos++;
         if (checkcfg(CFG_XEPHYR_WINDOW_TITLE)) {
-                if (asprintf(&cmd1, "Xephyr -ac -br -title \"firejail x11 sandbox\" -terminate -screen %s %s :%d", xephyr_screen, xephyr_extra_params, display) == -1)
-                        errExit("asprintf");
-        }
-        else {
-                if (asprintf(&cmd1, "Xephyr -ac -br -terminate -screen %s %s :%d",  xephyr_screen, xephyr_extra_params, display) == -1)
-                        errExit("asprintf");
+                server_argv[pos++] = "-title";
+                server_argv[pos++] = "firejail x11 sandbox";
         }
 
-        int len = 50; // DISPLAY...
-        for (i = 0; i < argc; i++) {
-                len += strlen(argv[i]) + 1; // + ' '
+        assert(xephyr_extra_params); // should be "" if empty
+
+        // parse xephyr_extra_params
+        // very basic quoting support
+        char *temp = strdup(xephyr_extra_params);
+        if (xephyr_extra_params != "") {
+                if (!temp)
+                        errExit("strdup");
+                bool dquote = false;
+                bool squote = false;
+                for (i = 0; i < strlen(xephyr_extra_params); i++) {
+                        if (temp[i] == '\"') {
+                                dquote = !dquote;
+                                if (dquote) temp[i] = '\0'; // replace closing quote by \0
+                        }
+                        if (temp[i] == '\'') {
+                                squote = !squote;
+                                if (squote) temp[i] = '\0'; // replace closing quote by \0
+                        }
+                        if (!dquote && !squote && temp[i] == ' ') temp[i] = '\0';
+                        if (dquote && squote) {
+                                fprintf(stderr, "Error: mixed quoting found while parsing xephyr_extra_params\n");
+                                exit(1);
+                        }
+                }
+                if (dquote) {
+                        fprintf(stderr, "Error: unclosed quote found while parsing xephyr_extra_params\n");
+                        exit(1);
+                }
+
+                for (i = 0; i < strlen(xephyr_extra_params)-1; i++) {
+                        if (pos >= (sizeof(server_argv)/sizeof(*server_argv))) {
+                                fprintf(stderr, "Error: arg count limit exceeded while parsing xephyr_extra_params\n");
+                                exit(1);
+                        }
+                        if (temp[i] == '\0' && (temp[i+1] == '\"' || temp[i+1] == '\'')) server_argv[pos++] = temp + i + 2;
+                        else if (temp[i] == '\0' && temp[i+1] != '\0') server_argv[pos++] = temp + i + 1;
+                }
         }
         
-        char *cmd2 = malloc(len + 1); // + '\0'
-        if (!cmd2)
-                errExit("malloc");
+        server_argv[pos++] = display_str;
+        server_argv[pos++] = NULL;
+
+        assert(pos < (sizeof(server_argv)/sizeof(*server_argv))); // no overrun
+        assert(server_argv[pos-1] == NULL); // last element is null
         
-        sprintf(cmd2, "DISPLAY=:%d ", display);
-        char *ptr = cmd2 + strlen(cmd2);
+        if (arg_debug) {
+                size_t i = 0;
+                printf("xephyr server:");
+                while (server_argv[i]!=NULL) {
+                        printf(" \"%s\"", server_argv[i]);
+                        i++;
+                }
+                putchar('\n');
+        }
+
+        // remove --x11 arg
+        char *client_argv[argc+2];
+        size_t j = 0;
         for (i = 0; i < argc; i++) {
                 if (strcmp(argv[i], "--x11") == 0)
                         continue;
@@ -216,14 +264,23 @@ void x11_start_xephyr(int argc, char **argv) {
                         continue;
                 if (strcmp(argv[i], "--x11=xephyr") == 0)
                         continue;
-                ptr += sprintf(ptr, "%s ", argv[i]);
+                client_argv[j] = argv[i];
+                j++;
+        }
+        client_argv[j] = NULL;
+
+        assert(j < argc+2); // no overrun
+
+        if (arg_debug) {
+                size_t i = 0;
+                printf("xephyr client:");
+                while (client_argv[i]!=NULL) {
+                        printf(" \"%s\"", client_argv[i]);
+                        i++;
+                }
+                putchar('\n');
         }
-        if (arg_debug)
-                printf("xephyr server: %s\n", cmd1);    
-        if (arg_debug)
-                printf("xephyr client: %s\n", cmd2);    
         
-        signal(SIGHUP,SIG_IGN); // fix sleep(1) below
         server = fork();
         if (server < 0)
                 errExit("fork");
@@ -231,17 +288,14 @@ void x11_start_xephyr(int argc, char **argv) {
                 if (arg_debug)
                         printf("Starting xephyr...\n");
         
-                char *a[4];
-                a[0] = "/bin/bash";
-                a[1] = "-c";
-                a[2] = cmd1;
-                a[3] = NULL;
-        
-                execvp(a[0], a); 
+                execvp(server_argv[0], server_argv);
                 perror("execvp");
                 exit(1);
         }
 
+        if (arg_debug)
+                printf("xephyr server pid %d\n", server);
+
         // check X11 socket
         char *fname;
         if (asprintf(&fname, "/tmp/.X11-unix/X%d", display) == -1)
@@ -259,7 +313,6 @@ void x11_start_xephyr(int argc, char **argv) {
                 exit(1);
         }
         free(fname);
-        sleep(1);
         
         if (arg_debug) {
                 printf("X11 sockets: "); fflush(0);
@@ -267,26 +320,32 @@ void x11_start_xephyr(int argc, char **argv) {
                 (void) rv;
         }
 
+        setenv("DISPLAY", display_str, 1);
         // run attach command
         client = fork();
         if (client < 0)
                 errExit("fork");
         if (client == 0) {
                 printf("\n*** Attaching to Xephyr display %d ***\n\n", display);
-                char *a[4];
-                a[0] = "/bin/bash";
-                a[1] = "-c";
-                a[2] = cmd2;
-                a[3] = NULL;
-        
-                execvp(a[0], a); 
+
+                execvp(client_argv[0], client_argv);
                 perror("execvp");
                 exit(1);
         }
-        sleep(1);
-        
-        if (!arg_quiet)
-                printf("Xephyr server pid %d, client pid %d\n", server, client);
+
+        // cleanup
+        free(display_str);
+        free(temp);
+
+        // wait for either server or client termination
+        pid_t pid = wait();
+
+        // see which process terminated and kill other
+        if (pid == server) {
+                kill(client, SIGTERM);
+        } else if (pid == client) {
+                kill(server, SIGTERM);
+        }
 
         exit(0);
 }