feat: Add Firewall / Access Control with blocklist.txt and 403 Forbidden response

README.md

@@ -5,19 +5,20 @@ This project is implemented using `C` and Parsing of HTTP referred from <a href
 
 ## Index
 
-- [Project Theory](https://github.com/Lovepreet-Singh-LPSK/MultiThreadedProxyServerClient#project-theory)
-- [How to Run](https://github.com/Lovepreet-Singh-LPSK/MultiThreadedProxyServerClient#How-to-Run)
-- [Demo](https://github.com/Lovepreet-Singh-LPSK/MultiThreadedProxyServerClient#Demo)
-- [Contributing](https://github.com/Lovepreet-Singh-LPSK/MultiThreadedProxyServerClient#contributing)
+- [Project Theory](https://github.com/uddiGitHub/MultiThreadedProxyServerClient#project-theory)
+- [How to Run](https://github.com/uddiGitHub/MultiThreadedProxyServerClient#How-to-Run)
+- [Demo](https://github.com/uddiGitHub/MultiThreadedProxyServerClient#Demo)
+- [Contributors](https://github.com/uddiGitHub/MultiThreadedProxyServerClient#Contributors)
+- [Contributing](https://github.com/uddiGitHub/MultiThreadedProxyServerClient#contributing)
 
 ## Project Theory
 
-[[Back to top]](https://github.com/Lovepreet-Singh-LPSK/MultiThreadedProxyServerClient#index)
+[[Back to top]](https://github.com/uddiGitHub/MultiThreadedProxyServerClient#index)
 
 ##### Introduction
 
 ##### Basic Working Flow of the Proxy Server:
-![](https://github.com/Lovepreet-Singh-LPSK/MultiThreadedProxyServerClient/blob/main/pics/UML.JPG)
+![](https://github.com/uddiGitHub/MultiThreadedProxyServerClient/blob/main/pics/UML.JPG)
 
 ##### How did we implement Multi-threading?
 - Used Semaphore instead of Condition Variables and pthread_join() and pthread_exit() function. 
@@ -43,13 +44,16 @@ This project is implemented using `C` and Parsing of HTTP referred from <a href
 - Semaphore
 - Cache (LRU algorithm is used in it)
 
+##### Access Control (Firewall)
+- We implemented a blocklist feature that restricts users from accessing specific websites.
+- A `blocklist.txt` file is loaded into memory when the server starts. Any HTTP request for a domain listed in this file is intercepted, and the proxy directly responds with a `403 Forbidden` error page.
+
 ##### Limitations ​
 - If a URL opens multiple clients itself, then our cache will store each client’s response as a separate element in the linked list. So, during retrieval from the cache, only a chunk of response will be send and the website will not open
 - Fixed size of cache element, so big websites may not be stored in cache. 
 
 ##### How this project can be extended? ​
 - This code can be implemented using multiprocessing that can speed up the process with parallelism.
-- We can decide which type of websites should be allowed by extending the code.
 - We can implement requests like POST with this code.
 
 
@@ -60,26 +64,31 @@ This project is implemented using `C` and Parsing of HTTP referred from <a href
 ## How to Run
 
 ```bash
-$ git clone https://github.com/Lovepreet-Singh-LPSK/MultiThreadedProxyServerClient.git
+$ git clone https://github.com/uddiGitHub/MultiThreadedProxyServerClient.git
 $ cd MultiThreadedProxyServerClient
 $ make all
 $ ./proxy <port no.>
 ```
-`Open http://localhost:port/https://www.cs.princeton.edu/`
-
-# Note:
-- This code can only be run in Linux Machine. Please disable your browser cache.
-- To run the proxy without cache Change the name of the file (`proxy_server_with_cache.c to proxy_server_without_cache.c`) MakeFile.
+**Note:**
+- This code can only be run in Linux or MacOS Machine. Please disable your browser cache.
+- To run the proxy without cache, change the name of the file in the Makefile (`proxy_server_with_cache.c` to `proxy_server_without_cache.c`).
 
 ## Demo
-![](https://github.com/Lovepreet-Singh-LPSK/MultiThreadedProxyServerClient/blob/main/pics/cache.png)
+![](https://github.com/uddiGitHub/MultiThreadedProxyServerClient/blob/main/pics/cache.png)
+
 - When website is opened for the first time (`url not found`) then cache will be miss.
 - Then if you again open that website again then `Data is retrieved from the cache` will be printed.
 
-## Contributing
+## Contributors
+
+| Contributor | GitHub | Contributions |
+| :--- | :--- | :--- |
+| **Lovepreet Singh** | [Lovepreet-Singh-LPSK](https://github.com/Lovepreet-Singh-LPSK) | Original proxy server implementation (multi-threading, LRU caching, HTTP parsing) |
+| **Uddipta Deka** | [uddiGitHub](https://github.com/uddiGitHub) | Implemented Firewall / Access Control feature: `blocklist.txt` loading, hostname blocking via `is_blocked()` check, and `403 Forbidden` response before request forwarding. Applied to both `proxy_server_with_cache.c` and `proxy_server_without_cache.c`. |
 
-[[Back to top]](https://github.com/Lovepreet-Singh-LPSK/MultiThreadedProxyServerClient#index)
+## Contributing
+[Back to top](#index)
 
-Feel free to add some useful. You can see `How this code can be extended`. Use ideas from there and feel free to fork and CHANGE. 
+Feel free to add some useful. You can see `How this code can be extended`. Use ideas from there and feel free to fork and CHANGE.
 
-#### Enjoy CODE and pull requests are highly appreciated.
+#### Enjoy CODE and pull requests are highly appreciated.

blocklist.txt

@@ -0,0 +1,3 @@
+www.cs.princeton.edu
+blocked.com
+www.google.com

proxy_server_with_cache.c

@@ -47,6 +47,40 @@ pthread_mutex_t lock;               //lock is used for locking the cache
 cache_element* head;                //pointer to the cache
 int cache_size;             //cache_size denotes the current size of the cache
 
+#define MAX_BLOCKED_HOSTS 100
+char blocked_hosts[MAX_BLOCKED_HOSTS][256];
+int num_blocked_hosts = 0;
+
+void load_blocklist() {
+    FILE *file = fopen("blocklist.txt", "r");
+    if (file == NULL) {
+        printf("No blocklist.txt found or unable to open. No hosts will be blocked.\n");
+        return;
+    }
+
+    char line[256];
+    while (fgets(line, sizeof(line), file)) {
+        // Remove newline character
+        line[strcspn(line, "\r\n")] = 0;
+        if (strlen(line) > 0 && num_blocked_hosts < MAX_BLOCKED_HOSTS) {
+            strcpy(blocked_hosts[num_blocked_hosts], line);
+            num_blocked_hosts++;
+        }
+    }
+    fclose(file);
+    printf("Loaded %d blocked hosts from blocklist.txt\n", num_blocked_hosts);
+}
+
+int is_blocked(char* host) {
+    if (host == NULL) return 0;
+    for (int i = 0; i < num_blocked_hosts; i++) {
+        if (strcmp(host, blocked_hosts[i]) == 0) {
+            return 1;
+        }
+    }
+    return 0;
+}
+
 int sendErrorMessage(int socket, int status_code)
 {
 	char str[1024];
@@ -136,7 +170,7 @@ int connectRemoteServer(char* host_addr, int port_num)
 }
 
 
-int handle_request(int clientSocket, ParsedRequest *request, char *tempReq)
+int handle_request(int clientSocket, struct ParsedRequest *request, char *tempReq)
 {
 	char *buf = (char*)malloc(sizeof(char)*MAX_BYTES);
 	strcpy(buf, "GET ");
@@ -302,7 +336,7 @@ void* thread_fn(void* socketNew)
 	{
 		len = strlen(buffer); 
 		//Parsing the request
-		ParsedRequest* request = ParsedRequest_create();
+		struct ParsedRequest* request = ParsedRequest_create();
 
         //ParsedRequest_parse returns 0 on success and -1 on failure.On success it stores parsed request in
         // the request
@@ -318,10 +352,15 @@ void* thread_fn(void* socketNew)
 
 				if( request->host && request->path && (checkHTTPversion(request->version) == 1) )
 				{
-					bytes_send_client = handle_request(socket, request, tempReq);		// Handle GET request
-					if(bytes_send_client == -1)
-					{	
-						sendErrorMessage(socket, 500);
+					if (is_blocked(request->host)) {
+						printf("Blocked request to %s\n", request->host);
+						sendErrorMessage(socket, 403);
+					} else {
+						bytes_send_client = handle_request(socket, request, tempReq);		// Handle GET request
+						if(bytes_send_client == -1)
+						{	
+							sendErrorMessage(socket, 500);
+						}
 					}
 
 				}
@@ -381,6 +420,7 @@ int main(int argc, char * argv[]) {
 	}
 
 	printf("Setting Proxy Server Port : %d\n",port_number);
+	load_blocklist();
 
     //creating the proxy socket
 	proxy_socketId = socket(AF_INET, SOCK_STREAM, 0);

proxy_server_without_cache.c

@@ -94,7 +94,39 @@ cache_element* head;                //pointer to the cache
 
 int cache_size=0;             //cache_size denotes the current size of the cache
 
+#define MAX_BLOCKED_HOSTS 100
+char blocked_hosts[MAX_BLOCKED_HOSTS][256];
+int num_blocked_hosts = 0;
+
+void load_blocklist() {
+    FILE *file = fopen("blocklist.txt", "r");
+    if (file == NULL) {
+        printf("No blocklist.txt found or unable to open. No hosts will be blocked.\n");
+        return;
+    }
 
+    char line[256];
+    while (fgets(line, sizeof(line), file)) {
+        // Remove newline character
+        line[strcspn(line, "\r\n")] = 0;
+        if (strlen(line) > 0 && num_blocked_hosts < MAX_BLOCKED_HOSTS) {
+            strcpy(blocked_hosts[num_blocked_hosts], line);
+            num_blocked_hosts++;
+        }
+    }
+    fclose(file);
+    printf("Loaded %d blocked hosts from blocklist.txt\n", num_blocked_hosts);
+}
+
+int is_blocked(char* host) {
+    if (host == NULL) return 0;
+    for (int i = 0; i < num_blocked_hosts; i++) {
+        if (strcmp(host, blocked_hosts[i]) == 0) {
+            return 1;
+        }
+    }
+    return 0;
+}
 
 int sendErrorMessage(int socket, int status_code)
 
@@ -613,15 +645,19 @@ void* thread_fn(void* socketNew)
 				if( request->host && request->path && (checkHTTPversion(request->version) == 1) )
 
 				{
+					if (is_blocked(request->host)) {
+						printf("Blocked request to %s\n", request->host);
+						sendErrorMessage(socket, 403);
+					} else {
+						bytes_send_client = handle_request(socket, request, buffer, tempReq);		// Handle GET request
 
-					bytes_send_client = handle_request(socket, request, buffer, tempReq);		// Handle GET request
-
-					if(bytes_send_client == -1)
+						if(bytes_send_client == -1)
 
-					{	
+						{	
 
-						sendErrorMessage(socket, 500);
+							sendErrorMessage(socket, 500);
 
+						}
 					}
 
 
@@ -735,6 +771,7 @@ int main(int argc, char * argv[]) {
 
 
 	printf("Setting Proxy Server Port : %d\n",port_number);
+	load_blocklist();