merge #1100 from zackw: xvfb support

5 files changed, 254 insertions, 0 deletions

diff --git a/src/firejail/checkcfg.c b/src/firejail/checkcfg.c
index dff892ea3..56ab7c932 100644
--- a/src/firejail/checkcfg.c
+++ b/src/firejail/checkcfg.c
@@ -27,6 +27,8 @@ static int initialized = 0;
 static int cfg_val[CFG_MAX];
 char *xephyr_screen = "800x600";
 char *xephyr_extra_params = "";
+char *xvfb_screen = "800x600x24";
+char *xvfb_extra_params = "";
 char *netfilter_default = NULL;
 
 int checkcfg(int val) {
@@ -234,6 +236,28 @@ int checkcfg(int val) {
                                         errExit("strdup");
                         }
                         
+                        // Xvfb screen size
+                        else if (strncmp(ptr, "xvfb-screen ", 12) == 0) {
+                                // expecting three numbers separated by x's
+                                unsigned int n1;
+                                unsigned int n2;
+                                unsigned int n3;
+                                int rv = sscanf(ptr + 12, "%ux%ux%u", &n1, &n2, &n3);
+                                if (rv != 3)
+                                        goto errout;
+                                if (asprintf(&xvfb_screen, "%ux%ux%u", n1, n2, n3) == -1)
+                                        errExit("asprintf");
+                        }
+
+                        // Xvfb extra parameters
+                        else if (strncmp(ptr, "xvfb-extra-params ", 18) == 0) {
+                                if (*xvfb_extra_params != '\0')
+                                        goto errout;
+                                xvfb_extra_params = strdup(ptr + 18);
+                                if (!xvfb_extra_params)
+                                        errExit("strdup");
+                        }
+                        
                         // quiet by default
                         else if (strncmp(ptr, "quiet-by-default ", 17) == 0) {
                                 if (strcmp(ptr + 17, "yes") == 0)
diff --git a/src/firejail/firejail.h b/src/firejail/firejail.h
index cafaf8c4f..aec6f3de4 100644
--- a/src/firejail/firejail.h
+++ b/src/firejail/firejail.h
@@ -684,6 +684,8 @@ enum {
 };
 extern char *xephyr_screen;
 extern char *xephyr_extra_params;
+extern char *xvfb_screen;
+extern char *xvfb_extra_params;
 extern char *netfilter_default;
 int checkcfg(int val);
 void print_compiletime_support(void);
diff --git a/src/firejail/main.c b/src/firejail/main.c
index 978ca8cd2..5951e5d16 100644
--- a/src/firejail/main.c
+++ b/src/firejail/main.c
@@ -349,6 +349,14 @@ static void run_cmd_and_exit(int i, int argc, char **argv) {
                 else
                         exit_err_feature("x11");
         }
+        else if (strcmp(argv[i], "--x11=xvfb") == 0) {
+                if (checkcfg(CFG_X11)) {
+                        x11_start_xvfb(argc, argv);
+                        exit(0);
+                }
+                else
+                        exit_err_feature("x11");
+        }
 #endif
 #ifdef HAVE_NETWORK     
         else if (strncmp(argv[i], "--bandwidth=", 12) == 0) {
diff --git a/src/firejail/profile.c b/src/firejail/profile.c
index 271176fcd..9f6688d4a 100644
--- a/src/firejail/profile.c
+++ b/src/firejail/profile.c
@@ -719,6 +719,7 @@ int profile_check_line(char *ptr, int lineno, const char *fname) {
 #endif
                 return 0;
         }
+        
         if (strcmp(ptr, "x11 xpra") == 0) {
 #ifdef HAVE_X11
                 if (checkcfg(CFG_X11)) {
@@ -738,6 +739,25 @@ int profile_check_line(char *ptr, int lineno, const char *fname) {
                 return 0;
         }
         
+        if (strcmp(ptr, "x11 xvfb") == 0) {
+#ifdef HAVE_X11
+                if (checkcfg(CFG_X11)) {
+                        char *x11env = getenv("FIREJAIL_X11");
+                        if (x11env && strcmp(x11env, "yes") == 0) {
+                                return 0;
+                        }
+                        else {
+                                // start x11
+                                x11_start_xvfb(cfg.original_argc, cfg.original_argv);
+                                exit(0);
+                        }
+                }
+                else
+                        warning_feature_disabled("x11");
+#endif
+                return 0;
+        }
+
         if (strcmp(ptr, "x11") == 0) {
 #ifdef HAVE_X11
                 if (checkcfg(CFG_X11)) {
diff --git a/src/firejail/x11.c b/src/firejail/x11.c
index b668c1c9c..f66848b7c 100644
--- a/src/firejail/x11.c
+++ b/src/firejail/x11.c
@@ -200,6 +200,206 @@ static int random_display_number(void) {
 
 
 #ifdef HAVE_X11
+
+void x11_start_xvfb(int argc, char **argv) {
+        EUID_ASSERT();
+        int i;
+        struct stat s;
+        pid_t jail = 0;
+        pid_t server = 0;
+        
+        setenv("FIREJAIL_X11", "yes", 1);
+
+        // mever try to run X servers as root!!!
+        if (getuid() == 0) {
+                fprintf(stderr, "Error: X11 sandboxing is not available when running as root\n");
+                exit(1);
+        }
+        drop_privs(0);
+
+        // check xephyr
+        if (!program_in_path("Xvfb")) {
+                fprintf(stderr, "\nError: xvfb program was not found in /usr/bin directory, please install it:\n");
+                fprintf(stderr, "   Debian/Ubuntu/Mint: sudo apt-get install xvfb\n");
+                fprintf(stderr, "   Arch: sudo pacman -S xorg-server-xvfb\n");
+                exit(0);
+        }
+        
+        int display = random_display_number();
+        char *display_str;
+        if (asprintf(&display_str, ":%d", display) == -1)
+                errExit("asprintf");
+
+        assert(xvfb_screen);
+
+        char *server_argv[256] = { "Xvfb", display_str, "-screen", "0", xvfb_screen }; // rest initialyzed to NULL
+        unsigned pos = 0;
+        while (server_argv[pos] != NULL) pos++;
+        assert(xvfb_extra_params); // should be "" if empty
+
+        // parse xvfb_extra_params
+        // very basic quoting support
+        char *temp = strdup(xephyr_extra_params);
+        if (*xephyr_extra_params != '\0') {
+                if (!temp)
+                        errExit("strdup");
+                bool dquote = false;
+                bool squote = false;
+                for (i = 0; i < (int) strlen(xvfb_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 xvfb_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 < (int) strlen(xvfb_extra_params)-1; i++) {
+                        if (pos >= (sizeof(server_argv)/sizeof(*server_argv)) - 2) {
+                                fprintf(stderr, "Error: arg count limit exceeded while parsing xvfb_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;
+                }
+        }
+        
+        server_argv[pos++] = NULL;
+
+        assert(pos < (sizeof(server_argv)/sizeof(*server_argv))); // no overrun
+        assert(server_argv[pos-1] == NULL); // last element is null
+        
+        if (arg_debug) {
+                size_t i = 0;
+                printf("xvfb server:");
+                while (server_argv[i]!=NULL) {
+                        printf(" \"%s\"", server_argv[i]);
+                        i++;
+                }
+                putchar('\n');
+        }
+
+        // remove --x11 arg
+        char *jail_argv[argc+2];
+        int j = 0;
+        for (i = 0; i < argc; i++) {
+                if (strcmp(argv[i], "--x11") == 0)
+                        continue;
+                if (strcmp(argv[i], "--x11=xpra") == 0)
+                        continue;
+                if (strcmp(argv[i], "--x11=xephyr") == 0)
+                        continue;
+                if (strcmp(argv[i], "--x11=xvfb") == 0)
+                        continue;
+                jail_argv[j] = argv[i];
+                j++;
+        }
+        jail_argv[j] = NULL;
+
+        assert(j < argc+2); // no overrun
+
+        if (arg_debug) {
+                size_t i = 0;
+                printf("xvfb client:");
+                while (jail_argv[i]!=NULL) {
+                        printf(" \"%s\"", jail_argv[i]);
+                        i++;
+                }
+                putchar('\n');
+        }
+        
+        server = fork();
+        if (server < 0)
+                errExit("fork");
+        if (server == 0) {
+                if (arg_debug)
+                        printf("Starting xvfb...\n");
+
+                // running without privileges - see drop_privs call above
+                assert(getenv("LD_PRELOAD") == NULL);   
+                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)
+                errExit("asprintf");
+        int n = 0;
+        // wait for x11 server to start
+        while (++n < 10) {
+                sleep(1);
+                if (stat(fname, &s) == 0)
+                        break;
+        };
+        
+        if (n == 10) {
+                fprintf(stderr, "Error: failed to start xephyr\n");
+                exit(1);
+        }
+        free(fname);
+        
+        if (arg_debug) {
+                printf("X11 sockets: "); fflush(0);
+                int rv = system("ls /tmp/.X11-unix");
+                (void) rv;
+        }
+
+        setenv("DISPLAY", display_str, 1);
+        // run attach command
+        jail = fork();
+        if (jail < 0)
+                errExit("fork");
+        if (jail == 0) {
+                if (!arg_quiet)
+                        printf("\n*** Attaching to Xvfb display %d ***\n\n", display);
+
+                // running without privileges - see drop_privs call above
+                assert(getenv("LD_PRELOAD") == NULL);   
+                execvp(jail_argv[0], jail_argv);
+                perror("execvp");
+                _exit(1);
+        }
+
+        // cleanup
+        free(display_str);
+        free(temp);
+
+        // wait for either server or jail termination
+        pid_t pid = wait(NULL);
+
+        // see which process terminated and kill other
+        if (pid == server) {
+                kill(jail, SIGTERM);
+        } else if (pid == jail) {
+                kill(server, SIGTERM);
+        }
+
+        // without this closing Xephyr window may mess your terminal:
+        // "monitoring" process will release terminal before
+        // jail process ends and releases terminal
+        wait(NULL); // fulneral
+
+        exit(0);
+}
+
+
+
 //$ 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) {