WIP: Added the initial process table implementation.

Wrote a basic process table implementation with CC's vectors and hash
maps. So far, it looks like it does not really work.

src/main.c

@@ -36,7 +36,7 @@ int main(int argc, char *argv[]) {
     exit(EXIT_FAILURE);
   }
 
-  ret = init_ui_socket("/home/fedir/.icfs-sock");
+  ret = init_ui_socket();
   if (ret != 0) {
     perror("init_ui_socket");
     exit(EXIT_FAILURE);
@@ -45,5 +45,6 @@ int main(int argc, char *argv[]) {
   ret = fuse_main(argc, argv, get_fuse_operations(), NULL);
 
   free(mountpoint);
+  destroy_ui_socket();
   return ret;
 }

src/ui-socket.c

@@ -8,7 +8,9 @@
 
 #include <stddef.h>
 #include <sys/types.h>
+#include <time.h>
 #define _GNU_SOURCE
+#include "cc.h"
 #include "ui-socket.h"
 #include <errno.h>
 #include <pthread.h>
@@ -19,7 +21,61 @@
 #include <sys/un.h>
 #include <unistd.h>
 
-int init_ui_socket(const char *filename) {
+/**
+ * Function to get the process creation time (in jiffies) from the proc
+ * filesystem
+ *
+ * @param pid: The process ID of the process to get the creation time of
+ * @return: The process creation time in jiffies, or 0 on error
+ * @note: although nothing in the documentation says that the creation time is
+ * never really equal to 0, it exceptionally unlikely.
+ */
+unsigned long long get_process_creation_time(pid_t pid) {
+  char path[32];
+  FILE *fp;
+  unsigned long long creation_time = 0;
+
+  // Construct the path to the process's status file
+  snprintf(path, sizeof(path), "/proc/%d/stat", pid);
+
+  // Open the status file
+  fp = fopen(path, "r");
+  if (fp == NULL) {
+    perror("fopen");
+    return 0;
+  }
+
+  // Read the creation time (the 22nd field in the stat file)
+  for (int i = 1; i < 22; i++) {
+    if (fscanf(fp, "%*s") != 1) {
+      fprintf(stderr, "Error reading process stat file\n");
+      fclose(fp);
+      return 0;
+    }
+  }
+  if (fscanf(fp, "%llu", &creation_time) != 1) {
+    fprintf(stderr, "Error reading creation time\n");
+    fclose(fp);
+    return 0;
+  }
+
+  // Close the file
+  fclose(fp);
+
+  return creation_time;
+}
+
+struct temp_process_permissions {
+  // yes, this is a correct type for start time in jiffies (see
+  // proc_pid_stat(5))
+  unsigned long long creation_time;
+  vec(char *) allowed_files;
+};
+
+map(pid_t, struct temp_process_permissions) temp_permissions_table;
+pthread_mutex_t temp_permissions_table_lock;
+
+int init_ui_socket() {
   char line[256];
   FILE *fp;
 
@@ -28,12 +84,24 @@ int init_ui_socket(const char *filename) {
   if (fp == NULL) {
     perror("Pipe returned a error");
     return 1;
-  } else {
+  }
+  pthread_mutex_init(&temp_permissions_table_lock, PTHREAD_MUTEX_DEFAULT);
+  init(&temp_permissions_table);
+
   while (fgets(line, sizeof(line), fp))
     printf("%s", line);
   pclose(fp);
   return 0;
 }
+
+void destroy_ui_socket() {
+  // free the memory allocated for the table
+  for_each(&temp_permissions_table, entry) {
+    for_each(&entry->allowed_files, allowed_file) { free(*allowed_file); }
+    cleanup(&entry->allowed_files);
+  }
+  cleanup(&temp_permissions_table);
+  pthread_mutex_destroy(&temp_permissions_table_lock);
 }
 
 /**
@@ -71,6 +139,7 @@ int ask_access(const char *filename, struct process_info pi) {
   // to manually check the output.
   char buffer[1024];
   while (fgets(buffer, sizeof(buffer), fp)) {
+    printf("%s", buffer);
     if (strcmp(buffer, "Allow this time\n") == 0) {
       pclose(fp);
       return 2;
@@ -94,7 +163,31 @@ int ask_access(const char *filename, struct process_info pi) {
  * @return: 0 if access is denied, 1 if access is allowed
  */
 int check_temp_access(const char *filename, struct process_info pi) {
-  perror("Not implemented");
+  // TODO: more efficient locking
+  pthread_mutex_lock(&temp_permissions_table_lock);
+  struct temp_process_permissions *permission_entry =
+      get(&temp_permissions_table, pi.PID);
+  if (permission_entry != NULL) {
+    unsigned long long process_creation_time =
+        get_process_creation_time(pi.PID);
+    if (process_creation_time == 0) {
+      perror("Could not retrieve process creation time");
+      pthread_mutex_unlock(&temp_permissions_table_lock);
+      return 0;
+    }
+
+    if (process_creation_time == permission_entry->creation_time) {
+      // the process is the same as the one that was granted temporary access
+      // to the file
+      for_each(&permission_entry->allowed_files, allowed_file) {
+        if (strncmp(*allowed_file, filename, strlen(filename)) == 0) {
+          pthread_mutex_unlock(&temp_permissions_table_lock);
+          return 1;
+        }
+      }
+    }
+  }
+  pthread_mutex_unlock(&temp_permissions_table_lock);
   return 0;
 }
 
@@ -110,11 +203,51 @@ int check_perm_access(const char *filename, struct process_info pi) {
   return 0;
 }
 
-void give_temp_access(const char *filename, struct process_info pi) {
-  perror("Not implemented");
+int give_temp_access(const char *filename, struct process_info pi) {
+  pthread_mutex_lock(&temp_permissions_table_lock);
+  struct temp_process_permissions *permission_entry =
+      get(&temp_permissions_table, pi.PID);
+
+  if (permission_entry != NULL) {
+
+    unsigned long long process_creation_time =
+        get_process_creation_time(pi.PID);
+    if (process_creation_time == 0) {
+      perror("Could not retrieve process creation time");
+      pthread_mutex_unlock(&temp_permissions_table_lock);
+      return -1;
     }
-void give_perm_access(const char *filename, struct process_info pi) {
+
+    if (process_creation_time == permission_entry->creation_time) {
+      // the process is the same as the one that was granted temporary access
+      // to the file
+      push(&permission_entry->allowed_files, strdup(filename));
+      pthread_mutex_unlock(&temp_permissions_table_lock);
+      return 0;
+    }
+    // we have an entry for the process, but the process is different
+    // delete the entry and create a new one
+    erase(&temp_permissions_table, pi.PID);
+    permission_entry = NULL;
+  }
+
+  // no entry is present
+  // construct the entry
+  struct temp_process_permissions new_permission_entry;
+
+  new_permission_entry.creation_time = get_process_creation_time(pi.PID);
+  init(&new_permission_entry.allowed_files);
+  push(&new_permission_entry.allowed_files, strdup(filename));
+
+  insert(&temp_permissions_table, pi.PID, new_permission_entry);
+
+  pthread_mutex_unlock(&temp_permissions_table_lock);
+  return 0;
+}
+
+int give_perm_access(const char *filename, struct process_info pi) {
   perror("Not implemented");
+  return -1;
 }
 
 /**

src/ui-socket.h

@@ -21,8 +21,9 @@ struct process_info {
   uid_t UID;
 };
 
-// For default socket location, set socket_path = NULL.
-int init_ui_socket(const char *socket_path);
+int init_ui_socket();
+
+void destroy_ui_socket();
 
 int interactive_access(const char *filename, struct process_info pi);