Basic socket communication

Two new issues to solve:

* Should the ui communication component also be the one that manages
  permissions?
* The format of data sent (protocol) needs definition.

sources/main.c

@@ -217,6 +217,7 @@ static int xmp_releasedir(const char *path, struct fuse_file_info *fi) {
   return 0;
 }
 
+/*
 // TODO: make this work
 static int xmp_mknod(const char *path, mode_t mode, dev_t rdev) {
   int res;
@@ -230,6 +231,7 @@ static int xmp_mknod(const char *path, mode_t mode, dev_t rdev) {
 
   return 0;
 }
+*/
 
 static int xmp_mkdir(const char *path, mode_t mode) {
   int res;
@@ -288,7 +290,7 @@ static int xmp_rename(const char *from, const char *to, unsigned int flags) {
 static int xmp_link(const char *from, const char *to) {
   int res;
 
-  res = link(from, to);
+  res = source_link(from, to);
   if (res == -1)
     return -errno;
 
@@ -301,7 +303,7 @@ static int xmp_chmod(const char *path, mode_t mode, struct fuse_file_info *fi) {
   if (fi)
     res = fchmod(fi->fh, mode);
   else
-    res = chmod(path, mode);
+    res = source_chmod(path, mode);
   if (res == -1)
     return -errno;
 
@@ -315,7 +317,7 @@ static int xmp_chown(const char *path, uid_t uid, gid_t gid,
   if (fi)
     res = fchown(fi->fh, uid, gid);
   else
-    res = lchown(path, uid, gid);
+    res = source_chown(path, uid, gid);
   if (res == -1)
     return -errno;
 
@@ -329,7 +331,7 @@ static int xmp_truncate(const char *path, off_t size,
   if (fi)
     res = ftruncate(fi->fh, size);
   else
-    res = truncate(path, size);
+    res = source_truncate(path, size);
 
   if (res == -1)
     return -errno;
@@ -358,7 +360,7 @@ static int xmp_create(const char *path, mode_t mode,
                       struct fuse_file_info *fi) {
   int fd;
 
-  fd = open(path, fi->flags, mode);
+  fd = source_create(path, fi->flags, mode);
   if (fd == -1)
     return -errno;
 
@@ -369,7 +371,7 @@ static int xmp_create(const char *path, mode_t mode,
 static int xmp_open(const char *path, struct fuse_file_info *fi) {
   int fd;
 
-  fd = open(path, fi->flags);
+  fd = source_open(path, fi->flags);
   if (fd == -1)
     return -errno;
 
@@ -386,6 +388,7 @@ static int xmp_open(const char *path, struct fuse_file_info *fi) {
   return 0;
 }
 
+/* Complete copy of the example method(no need to modify anything so far) */
 static int xmp_read(const char *path, char *buf, size_t size, off_t offset,
                     struct fuse_file_info *fi) {
   int res;
@@ -398,6 +401,7 @@ static int xmp_read(const char *path, char *buf, size_t size, off_t offset,
   return res;
 }
 
+/* Complete copy of the example method(no need to modify anything so far) */
 static int xmp_read_buf(const char *path, struct fuse_bufvec **bufp,
                         size_t size, off_t offset, struct fuse_file_info *fi) {
   struct fuse_bufvec *src;
@@ -419,6 +423,7 @@ static int xmp_read_buf(const char *path, struct fuse_bufvec **bufp,
   return 0;
 }
 
+/* Complete copy of the example method(no need to modify anything so far) */
 static int xmp_write(const char *path, const char *buf, size_t size,
                      off_t offset, struct fuse_file_info *fi) {
   int res;
@@ -431,6 +436,7 @@ static int xmp_write(const char *path, const char *buf, size_t size,
   return res;
 }
 
+/* Complete copy of the example method(no need to modify anything so far) */
 static int xmp_write_buf(const char *path, struct fuse_bufvec *buf,
                          off_t offset, struct fuse_file_info *fi) {
   struct fuse_bufvec dst = FUSE_BUFVEC_INIT(fuse_buf_size(buf));
@@ -454,6 +460,7 @@ static int xmp_statfs(const char *path, struct statvfs *stbuf) {
   return 0;
 }
 
+/* Complete copy of the example method(no need to modify anything so far) */
 static int xmp_flush(const char *path, struct fuse_file_info *fi) {
   int res;
 
@@ -470,6 +477,7 @@ static int xmp_flush(const char *path, struct fuse_file_info *fi) {
   return 0;
 }
 
+/* Complete copy of the example method(no need to modify anything so far) */
 static int xmp_release(const char *path, struct fuse_file_info *fi) {
   (void)path;
   close(fi->fh);
@@ -477,6 +485,7 @@ static int xmp_release(const char *path, struct fuse_file_info *fi) {
   return 0;
 }
 
+/* Complete copy of the example method(no need to modify anything so far) */
 static int xmp_fsync(const char *path, int isdatasync,
                      struct fuse_file_info *fi) {
   int res;
@@ -551,6 +560,7 @@ static int xmp_lock(const char *path, struct fuse_file_info *fi, int cmd,
 }
 #endif
 
+/* Complete copy of the example method(no need to modify anything so far) */
 static int xmp_flock(const char *path, struct fuse_file_info *fi, int op) {
   int res;
   (void)path;
@@ -580,6 +590,7 @@ static ssize_t xmp_copy_file_range(const char *path_in,
 }
 #endif
 
+/* Complete copy of the example method(no need to modify anything so far) */
 static off_t xmp_lseek(const char *path, off_t off, int whence,
                        struct fuse_file_info *fi) {
   off_t res;
@@ -592,15 +603,16 @@ static off_t xmp_lseek(const char *path, off_t off, int whence,
   return res;
 }
 
+// TODO: look trough "optional"(commented out) operations.
 static const struct fuse_operations xmp_oper = {
     .init = xmp_init,
     .getattr = xmp_getattr,
-    .access = xmp_access,
+    // .access = xmp_access,
     .readlink = xmp_readlink,
     .opendir = xmp_opendir,
     .readdir = xmp_readdir,
     .releasedir = xmp_releasedir,
-    .mknod = xmp_mknod,
+    //    .mknod = xmp_mknod,
     .mkdir = xmp_mkdir,
     .symlink = xmp_symlink,
     .unlink = xmp_unlink,
@@ -611,7 +623,7 @@ static const struct fuse_operations xmp_oper = {
     .chown = xmp_chown,
     .truncate = xmp_truncate,
 #ifdef HAVE_UTIMENSAT
-    .utimens = xmp_utimens,
+// .utimens = xmp_utimens,
 #endif
     .create = xmp_create,
     .open = xmp_open,
@@ -624,20 +636,20 @@ static const struct fuse_operations xmp_oper = {
     .release = xmp_release,
     .fsync = xmp_fsync,
 #ifdef HAVE_POSIX_FALLOCATE
-    .fallocate = xmp_fallocate,
+// .fallocate = xmp_fallocate,
 #endif
 #ifdef HAVE_SETXATTR
-    .setxattr = xmp_setxattr,
-    .getxattr = xmp_getxattr,
-    .listxattr = xmp_listxattr,
-    .removexattr = xmp_removexattr,
+// .setxattr = xmp_setxattr,
+// .getxattr = xmp_getxattr,
+// .listxattr = xmp_listxattr,
+// .removexattr = xmp_removexattr,
 #endif
 #ifdef HAVE_LIBULOCKMGR
-    .lock = xmp_lock,
+// .lock = xmp_lock,
 #endif
     .flock = xmp_flock,
 #ifdef HAVE_COPY_FILE_RANGE
-    .copy_file_range = xmp_copy_file_range,
+// .copy_file_range = xmp_copy_file_range,
 #endif
     .lseek = xmp_lseek,
 };

sources/sourcefs.c

@@ -70,6 +70,47 @@ DIR *source_opendir(const char *filename) {
 }
 
 int source_rename(const char *oldpath, const char *newpath) {
-  printf("{\"%s\", \"%s\"}\n", oldpath, newpath);
-  return -1;
+  const char *relative_oldpath = source_fname_translate(oldpath);
+  const char *relative_newpath = source_fname_translate(newpath);
+  return renameat(handle.root_fd, relative_oldpath, handle.root_fd,
+                  relative_newpath);
+}
+
+int source_link(const char *oldpath, const char *newpath) {
+  const char *relative_oldpath = source_fname_translate(oldpath);
+  const char *relative_newpath = source_fname_translate(newpath);
+  return linkat(handle.root_fd, relative_oldpath, handle.root_fd,
+                relative_newpath, 0);
+  // NOTE: perhaps the flags here need to be reevaluated.
+}
+
+int source_chmod(const char *filename, mode_t mode) {
+  const char *relative_filename = source_fname_translate(filename);
+  return fchmodat(handle.root_fd, relative_filename, mode, 0);
+  // NOTE: perhaps the flags here need to be reevaluated.
+}
+
+int source_chown(const char *filename, uid_t owner, gid_t group) {
+  const char *relative_filename = source_fname_translate(filename);
+  return fchownat(handle.root_fd, filename, owner, group, AT_SYMLINK_NOFOLLOW);
+}
+
+int source_truncate(const char *filename, off_t length) {
+  const char *relative_filename = source_fname_translate(filename);
+  int fd = openat(handle.root_fd, relative_filename, NULL);
+  if (fd < 0) {
+    perror("Openat failed");
+    return -1;
+  }
+  return ftruncate(fd, length);
+}
+
+int source_open(const char *filename, int flags) {
+  const char *relative_filename = source_fname_translate(filename);
+  return openat(handle.root_fd, relative_filename, flags);
+}
+
+int source_create(const char *filename, int flags, mode_t mode) {
+  const char *relative_filename = source_fname_translate(filename);
+  return openat(handle.root_fd, relative_filename, flags, mode);
 }

sources/sourcefs.h

@@ -33,4 +33,19 @@ int source_symlink(const char *target, const char *linkpath);
 
 int source_rename(const char *oldpath, const char *newpath);
 
+int source_link(const char *oldpath, const char *newpath);
+
+int source_chmod(const char *filename, mode_t mode);
+
+int source_chown(const char *filename, uid_t owner, gid_t group);
+
+int source_truncate(const char *filename, off_t length);
+
+/* `open` and `create` are designed to correspond to fuse operations, not the
+ * libc's `open(2)`. Both of them actually call `openat`. */
+
+int source_open(const char *filename, int flags);
+
+int source_create(const char *filename, int flags, mode_t mode);
+
 #endif // !SOURCEFS_H

sources/ui-socket.c

@@ -0,0 +1,104 @@
+#include "ui-socket.h"
+#include <errno.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <unistd.h>
+
+static int socket_fd = -1;
+static pthread_mutex_t socket_mutex = PTHREAD_MUTEX_INITIALIZER;
+
+int init_ui_socket(const char *filename) {
+  struct sockaddr_un addr;
+  int fd;
+
+  if ((fd = socket(AF_UNIX, SOCK_STREAM, 0)) == -1) {
+    perror("socket");
+    return -1;
+  }
+
+  memset(&addr, 0, sizeof(addr));
+  addr.sun_family = AF_UNIX;
+  strncpy(addr.sun_path, filename, sizeof(addr.sun_path) - 1);
+
+  if (unlink(filename) == -1 && errno != ENOENT) {
+    perror("unlink");
+    close(fd);
+    return -1;
+  }
+
+  if (bind(fd, (struct sockaddr *)&addr, sizeof(addr)) == -1) {
+    perror("bind");
+    close(fd);
+    return -1;
+  }
+
+  if (listen(fd, 5) == -1) {
+    perror("listen");
+    close(fd);
+    return -1;
+  }
+
+  socket_fd = fd;
+  return 0;
+}
+
+int ask_access(const char *filename, struct process_info pi) {
+  int client_fd;
+  struct sockaddr_un client_addr;
+  socklen_t client_len = sizeof(client_addr);
+  char request[1024];
+  char response[4];
+  ssize_t bytes_sent, bytes_received;
+
+  // Accept a connection from the GUI
+  if ((client_fd = accept(socket_fd, (struct sockaddr *)&client_addr,
+                          &client_len)) == -1) {
+    perror("accept");
+    return -1;
+  }
+
+  // Construct the request message
+  snprintf(request, sizeof(request), "r%s;%d;%s;%d\0", filename, pi.PID,
+           pi.name, pi.UID);
+
+  // Lock the socket to ensure thread safety
+  pthread_mutex_lock(&socket_mutex);
+
+  // Send the request message to the GUI
+  bytes_sent = send(client_fd, request, strlen(request), 0);
+  if (bytes_sent == -1) {
+    perror("send");
+    pthread_mutex_unlock(&socket_mutex);
+    close(client_fd);
+    return -1;
+  }
+
+  // Receive the response from the GUI
+  bytes_received = recv(client_fd, response, sizeof(response) - 1, 0);
+  if (bytes_received == -1) {
+    perror("recv");
+    pthread_mutex_unlock(&socket_mutex);
+    close(client_fd);
+    return -1;
+  }
+  response[bytes_received] = '\0';
+
+  // Unlock the socket
+  pthread_mutex_unlock(&socket_mutex);
+
+  // Close the client socket
+  close(client_fd);
+
+  // Check the response
+  if (response[0] == 'a' && response[1] == 'y' && response[2] == '\0') {
+    return 0; // Access granted
+  } else if (response[0] == 'a' && response[1] == 'n' && response[2] == '\0') {
+    return 1; // Access denied
+  } else {
+    // fprintf(stderr, "Invalid response from GUI: %s\n", response);
+    return -1; // Invalid response
+  }
+}

sources/ui-socket.h

@@ -0,0 +1,24 @@
+
+/*
+ * Interface for controlling communication with the UI.
+ */
+
+#ifndef UI_SOCKET_H
+#define UI_SOCKET_H
+
+#include <sys/types.h>
+
+struct process_info {
+  pid_t PID;
+  const char *name;
+  uid_t UID;
+};
+
+// For default socket location, set socket_path = NULL.
+int init_ui_socket(const char *socket_path);
+
+// TODO: design an interface for asking user for permission.
+
+int ask_access(const char *filename, struct process_info pi);
+
+#endif // !UI_SOCKET_H