Implement WebSocket reverse proxy

README.md

@@ -10,7 +10,7 @@ Necronda web server
   * File compression ([gzip](https://www.gzip.org/), [Brotli](https://www.brotli.org/))
   * Disk cache for compressed files
 * Reverse proxy for other HTTP and HTTPS servers
-  * Transparent WebSocket reverse proxy **[WIP]**
+  * Transparent WebSocket reverse proxy
 * FastCGI support (e.g. [PHP-FPM](https://php-fpm.org/))
   * Automatic path info detection (e.g. `/my/file/extra/path` -> script: `/my/file.php`, path info: `extra/path`)
 * Support for [MaxMind's GeoIP Database](https://www.maxmind.com/en/geoip2-services-and-databases)

src/client.c

@@ -5,8 +5,8 @@
  * Lorenz Stechauner, 2020-12-03
  */
 
-#include "client.h"
 #include "necronda.h"
+#include "client.h"
 #include "server.h"
 
 #include "lib/utils.h"
@@ -18,6 +18,7 @@
 #include "lib/cache.h"
 #include "lib/geoip.h"
 #include "lib/compress.h"
+#include "lib/websocket.h"
 
 #include <string.h>
 #include <errno.h>
@@ -31,7 +32,6 @@
 int server_keep_alive = 1;
 struct timeval client_timeout = {.tv_sec = CLIENT_TIMEOUT, .tv_usec = 0};
 
-int server_keep_alive;
 char *log_client_prefix, *log_conn_prefix, *log_req_prefix, *client_geoip;
 char *client_addr_str, *client_addr_str_ptr, *server_addr_str, *server_addr_str_ptr, *client_host_str;
 
@@ -52,11 +52,6 @@ void client_terminate() {
     server_keep_alive = 0;
 }
 
-int client_websocket_handler() {
-    // TODO implement client_websocket_handler
-    return 0;
-}
-
 int client_request_handler(sock *client, unsigned long client_num, unsigned int req_num) {
     struct timespec begin, end;
     long ret;
@@ -86,7 +81,7 @@ int client_request_handler(sock *client, unsigned long client_num, unsigned int
     http_status custom_status;
 
     http_res res = {.version = "1.1", .status = http_get_status(501), .hdr.field_num = 0, .hdr.last_field_num = -1};
-    http_status_ctx ctx = {.status = 0, .origin = NONE};
+    http_status_ctx ctx = {.status = 0, .origin = NONE, .ws_key = NULL};
 
     clock_gettime(CLOCK_MONOTONIC, &begin);
 
@@ -125,7 +120,7 @@ int client_request_handler(sock *client, unsigned long client_num, unsigned int
     }
 
     hdr_connection = http_get_header_field(&req.hdr, "Connection");
-    client_keep_alive = (hdr_connection != NULL && (strcmp(hdr_connection, "keep-alive") == 0 || strcmp(hdr_connection, "Keep-Alive") == 0));
+    client_keep_alive = (hdr_connection != NULL && (strstr(hdr_connection, "keep-alive") != NULL || strstr(hdr_connection, "Keep-Alive") != NULL));
     host_ptr = http_get_header_field(&req.hdr, "Host");
     if (host_ptr != NULL && strlen(host_ptr) > 255) {
         host[0] = 0;
@@ -488,6 +483,25 @@ int client_request_handler(sock *client, unsigned long client_num, unsigned int
         ret = rev_proxy_init(&req, &res, &ctx, conf, client, &custom_status, err_msg);
         use_rev_proxy = (ret == 0);
 
+        if (res.status->code == 101) {
+            const char *connection = http_get_header_field(&res.hdr, "Connection");
+            const char *upgrade = http_get_header_field(&res.hdr, "Upgrade");
+            if (connection != NULL && upgrade != NULL &&
+                (strstr(connection, "upgrade") != NULL || strstr(connection, "Upgrade") != NULL) &&
+                strcmp(upgrade, "websocket") == 0)
+            {
+                const char *ws_accept = http_get_header_field(&res.hdr, "Sec-WebSocket-Accept");
+                if (ws_calc_accept_key(ctx.ws_key, buf0) == 0) {
+                    use_rev_proxy = (strcmp(buf0, ws_accept) == 0) ? 2 : 1;
+                }
+            } else {
+                print("Fail Test1");
+                ctx.status = 101;
+                ctx.origin = INTERNAL;
+                res.status = http_get_status(501);
+            }
+        }
+
         // Let 300 be formatted by origin server
         if (use_rev_proxy && res.status->code >= 301 && res.status->code < 600) {
             const char *content_type = http_get_header_field(&res.hdr, "Content-Type");
@@ -496,8 +510,10 @@ int client_request_handler(sock *client, unsigned long client_num, unsigned int
             if (content_encoding == NULL && content_type != NULL && content_length_f != NULL && strncmp(content_type, "text/html", 9) == 0) {
                 long content_len = strtol(content_length_f, NULL, 10);
                 if (content_len <= sizeof(msg_content) - 1) {
+                    if (ctx.status != 101) {
                         ctx.status = res.status->code;
                         ctx.origin = res.status->code >= 400 ? SERVER : NONE;
+                    }
                     use_rev_proxy = 0;
                     rev_proxy_dump(msg_content, content_len);
                 }
@@ -604,8 +620,10 @@ int client_request_handler(sock *client, unsigned long client_num, unsigned int
         }
     }
 
+    int close_proxy = 0;
+    if (use_rev_proxy != 2) {
         const char *conn = http_get_header_field(&res.hdr, "Connection");
-    int close_proxy = (conn == NULL || (strcmp(conn, "keep-alive") != 0 && strcmp(conn, "Keep-Alive") != 0));
+        close_proxy = (conn == NULL || (strstr(conn, "keep-alive") == NULL && strstr(conn, "Keep-Alive") == NULL));
         http_remove_header_field(&res.hdr, "Connection", HTTP_REMOVE_ALL);
         http_remove_header_field(&res.hdr, "Keep-Alive", HTTP_REMOVE_ALL);
         if (server_keep_alive && client_keep_alive) {
@@ -615,6 +633,7 @@ int client_request_handler(sock *client, unsigned long client_num, unsigned int
         } else {
             http_add_header_field(&res.hdr, "Connection", "close");
         }
+    }
 
     http_send_response(client, &res);
     clock_gettime(CLOCK_MONOTONIC, &end);
@@ -626,7 +645,17 @@ int client_request_handler(sock *client, unsigned long client_num, unsigned int
 
     // TODO access/error log file
 
-    if (strcmp(req.method, "HEAD") != 0) {
+    if (use_rev_proxy == 2) {
+        // WebSocket
+        print("Upgrading connection to WebSocket connection");
+        ret = ws_handle_connection(client, &rev_proxy);
+        if (ret != 0) {
+            client_keep_alive = 0;
+            close_proxy = 1;
+        }
+        print("WebSocket connection closed");
+    } else if (strcmp(req.method, "HEAD") != 0) {
+        // default response
         unsigned long snd_len = 0;
         unsigned long len;
         if (msg_buf[0] != 0) {

src/lib/http.h

@@ -108,6 +108,7 @@ typedef enum {
 typedef struct {
     unsigned short status;
     http_error_origin origin;
+    const char* ws_key;
 } http_status_ctx;
 
 extern const http_status http_statuses[];

src/lib/rev_proxy.c

@@ -5,10 +5,11 @@
  * Lorenz Stechauner, 2021-01-07
  */
 
+#include "../necronda.h"
+#include "../server.h"
 #include "rev_proxy.h"
 #include "utils.h"
 #include "compress.h"
-#include "../server.h"
 
 #include <openssl/ssl.h>
 #include <string.h>
@@ -33,8 +34,6 @@ int rev_proxy_preload() {
 int rev_proxy_request_header(http_req *req, int enc) {
     char buf1[256], buf2[256];
     int p_len;
-    http_remove_header_field(&req->hdr, "Connection", HTTP_REMOVE_ALL);
-    http_add_header_field(&req->hdr, "Connection", "keep-alive");
 
     const char *via = http_get_header_field(&req->hdr, "Via");
     sprintf(buf1, "HTTP/%s %s", req->version, SERVER_NAME);
@@ -184,12 +183,12 @@ int rev_proxy_response_header(http_req *req, http_res *res, host_config *conf) {
 
 int rev_proxy_init(http_req *req, http_res *res, http_status_ctx *ctx, host_config *conf, sock *client, http_status *custom_status, char *err_msg) {
     char buffer[CHUNK_SIZE];
+    const char *connection, *upgrade, *ws_version;
     long ret;
     int tries = 0, retry = 0;
 
-    if (rev_proxy.socket != 0 && strcmp(rev_proxy_host, conf->name) == 0 && sock_check(&rev_proxy) == 0) {
+    if (rev_proxy.socket != 0 && strcmp(rev_proxy_host, conf->name) == 0 && sock_check(&rev_proxy) == 0)
         goto rev_proxy;
-    }
 
     retry:
     if (rev_proxy.socket != 0) {
@@ -290,6 +289,22 @@ int rev_proxy_init(http_req *req, http_res *res, http_status_ctx *ctx, host_conf
     print(BLUE_STR "Established new connection with " BLD_STR "[%s]:%i" CLR_STR, buffer, conf->rev_proxy.port);
 
     rev_proxy:
+    connection = http_get_header_field(&req->hdr, "Connection");
+    if (connection != NULL && (strstr(connection, "upgrade") != NULL || strstr(connection, "Upgrade") != NULL)) {
+        upgrade = http_get_header_field(&req->hdr, "Upgrade");
+        ws_version = http_get_header_field(&req->hdr, "Sec-WebSocket-Version");
+        if (upgrade != NULL && ws_version != NULL && strcmp(upgrade, "websocket") == 0 && strcmp(ws_version, "13") == 0) {
+            ctx->ws_key = http_get_header_field(&req->hdr, "Sec-WebSocket-Key");
+        } else {
+            res->status = http_get_status(501);
+            ctx->origin = INTERNAL;
+            return -1;
+        }
+    } else {
+        http_remove_header_field(&req->hdr, "Connection", HTTP_REMOVE_ALL);
+        http_add_header_field(&req->hdr, "Connection", "keep-alive");
+    }
+
     ret = rev_proxy_request_header(req, (int) client->enc);
     if (ret != 0) {
         res->status = http_get_status(500);
@@ -454,7 +469,6 @@ int rev_proxy_init(http_req *req, http_res *res, http_status_ctx *ctx, host_conf
 }
 
 int rev_proxy_send(sock *client, unsigned long len_to_send, int flags) {
-    // TODO handle websockets
     char buffer[CHUNK_SIZE], comp_out[CHUNK_SIZE], buf[256], *ptr;
     long ret = 0, len, snd_len;
     int finish_comp = 0;

src/lib/sock.c

@@ -130,11 +130,12 @@ int sock_poll(sock *sockets[], sock *ready[], short events, int n_sock, int time
     int ret = poll(fds, n_sock, timeout_ms);
     if (ret < 0 || ready == NULL) return ret;
 
-    for (int i = 0, j = 0; i < ret; j++) {
+    int j = 0;
+    for (int i = 0; i < n_sock; i++) {
         if (fds[i].revents & events)
-            ready[i++] = sockets[j];
+            ready[j++] = sockets[i];
     }
-    return ret;
+    return j;
 }
 
 int sock_poll_read(sock *sockets[], sock *readable[], int n_sock, int timeout_ms) {

src/lib/sock.h

@@ -9,6 +9,7 @@
 #define NECRONDA_SERVER_SOCK_H
 
 #include <openssl/crypto.h>
+#include <sys/socket.h>
 
 typedef struct {
     unsigned int enc:1;

src/lib/utils.c

@@ -192,6 +192,7 @@ int base64_encode(void *data, unsigned long data_len, char *output, unsigned lon
 
     for (int i = 0; i < base64_mod_table[data_len % 3]; i++)
         output[out_len - 1 - i] = '=';
+    output[out_len] = 0;
 
     return 0;
 }

src/lib/websocket.c

@@ -0,0 +1,202 @@
+/**
+ * Necronda Web Server
+ * WebSocket reverse proxy
+ * src/lib/websocket.c
+ * Lorenz Stechauner, 2022-08-16
+ */
+
+#include "../necronda.h"
+#include "websocket.h"
+#include "utils.h"
+
+#include <string.h>
+#include <openssl/sha.h>
+#include <errno.h>
+#include <signal.h>
+
+
+int terminate = 0;
+
+void ws_terminate() {
+    terminate = 1;
+}
+
+int ws_calc_accept_key(const char *key, char *accept_key) {
+    if (key == NULL || accept_key == NULL)
+        return -1;
+
+    char input[256] = "";
+    unsigned char output[SHA_DIGEST_LENGTH];
+    strcat(input, key);
+    strcat(input, ws_key_uuid);
+
+    if (SHA1((unsigned char *) input, strlen(input), output) == NULL) {
+        return -2;
+    }
+
+    base64_encode(output, sizeof(output), accept_key, NULL);
+
+    return 0;
+}
+
+int ws_recv_frame_header(sock *s, ws_frame *frame) {
+    unsigned char buf[12];
+
+    long ret = sock_recv(s, buf, 2, 0);
+    if (ret < 0) {
+        print(ERR_STR "Unable to receive from socket: %s" CLR_STR, strerror(errno));
+        return -1;
+    } else if (ret != 2) {
+        print(ERR_STR "Unable to receive 2 bytes from socket" CLR_STR);
+        return -2;
+    }
+
+    unsigned short bits = (buf[0] << 8) | buf[1];
+    frame->f_fin = (bits >> 15) & 1;
+    frame->f_rsv1 = (bits >> 14) & 1;
+    frame->f_rsv2 = (bits >> 13) & 1;
+    frame->f_rsv3 = (bits >> 12) & 1;
+    frame->opcode = (bits >> 8) & 0xF;
+    frame->f_mask = (bits >> 7) & 1;
+    unsigned short len = (bits & 0x7F);
+
+    int remaining = frame->f_mask ? 4 : 0;
+    if (len == 126) {
+        remaining += 2;
+    } else if (len == 127) {
+        remaining += 8;
+    }
+
+    ret = sock_recv(s, buf, remaining, 0);
+    if (ret < 0) {
+        print(ERR_STR "Unable to receive from socket: %s" CLR_STR, strerror(errno));
+        return -1;
+    } else if (ret != remaining) {
+        print(ERR_STR "Unable to receive correct number of bytes from socket" CLR_STR);
+        return -2;
+    }
+
+    if (len == 126) {
+        frame->len = (((unsigned long) buf[0]) << 8) | ((unsigned long) buf[1]);
+    } else if (len == 127) {
+        frame->len =
+                (((unsigned long) buf[0]) << 56) |
+                (((unsigned long) buf[1]) << 48) |
+                (((unsigned long) buf[2]) << 40) |
+                (((unsigned long) buf[3]) << 32) |
+                (((unsigned long) buf[4]) << 24) |
+                (((unsigned long) buf[5]) << 16) |
+                (((unsigned long) buf[6]) << 8) |
+                (((unsigned long) buf[7]) << 0);
+    } else {
+        frame->len = len;
+    }
+
+    if (frame->f_mask) memcpy(frame->masking_key, buf + (remaining - 4), 4);
+
+    return 0;
+}
+
+int ws_send_frame_header(sock *s, ws_frame *frame) {
+    unsigned char buf[14], *ptr = buf;
+
+    unsigned short len;
+    if (frame->len > 0x7FFF) {
+        len = 127;
+    } else if (frame->len > 125) {
+        len = 126;
+    } else {
+        len = frame->len;
+    }
+
+    unsigned short bits =
+            (frame->f_fin << 15) |
+            (frame->f_rsv1 << 14) |
+            (frame->f_rsv2 << 13) |
+            (frame->f_rsv3 << 12) |
+            (frame->opcode << 8) |
+            (frame->f_mask << 7) |
+            len;
+
+    ptr++[0] = bits >> 8;
+    ptr++[0] = bits & 0xFF;
+
+    if (len >= 126) {
+        for (int i = (len == 126 ? 2 : 8) - 1; i >= 0; i--)
+            ptr++[0] = (unsigned char) ((frame->len >> (i * 8)) & 0xFF);
+    }
+
+    if (frame->f_mask) {
+        memcpy(ptr, frame->masking_key, 4);
+        ptr += 4;
+    }
+
+    long ret = sock_send(s, buf, ptr - buf, frame->len != 0 ? MSG_MORE : 0);
+    if (ret < 0) {
+        print(ERR_STR "Unable to send to socket: %s" CLR_STR, strerror(errno));
+        return -1;
+    } else if (ret != ptr - buf) {
+        print(ERR_STR "Unable to send to socket" CLR_STR);
+        return -2;
+    }
+
+    return 0;
+}
+
+int ws_handle_connection(sock *s1, sock *s2) {
+    sock *poll_socks[2] = {s1, s2};
+    sock *readable[2];
+    int n_sock = 2;
+    ws_frame frame;
+    char buf[CHUNK_SIZE];
+    int poll, closes = 0;
+    long ret;
+
+    signal(SIGINT, ws_terminate);
+    signal(SIGTERM, ws_terminate);
+
+    while (!terminate && closes != 3) {
+        poll = sock_poll_read(poll_socks, readable, n_sock, WS_TIMEOUT * 1000);
+        if (terminate) {
+            break;
+        } else if (poll < 0) {
+            print(ERR_STR "Unable to poll sockets: %s" CLR_STR, strerror(errno));
+            return -1;
+        } else if (poll == 0) {
+            print(ERR_STR "Connection timed out" CLR_STR);
+            return -2;
+        }
+
+        for (int i = 0; i < poll; i++) {
+            sock *s = readable[i];
+            sock *o = (s == s1) ? s2 : s1;
+            if (ws_recv_frame_header(s, &frame) != 0) return -3;
+
+            if (frame.opcode == 0x8) {
+                n_sock--;
+                if (s == s1) {
+                    poll_socks[0] = s2;
+                    closes |= 1;
+                } else {
+                    closes |= 2;
+                }
+            }
+
+            if (ws_send_frame_header(o, &frame) != 0) return -3;
+
+            if (frame.len > 0) {
+                ret = sock_splice(o, s, buf, sizeof(buf), frame.len);
+                if (ret < 0) {
+                    print(ERR_STR "Unable to forward data in WebSocket: %s" CLR_STR, strerror(errno));
+                    return -3;
+                } else if (ret != frame.len) {
+                    print(ERR_STR "Unable to forward correct number of bytes in WebSocket" CLR_STR);
+                    return -3;
+                }
+            }
+        }
+    }
+
+    return 0;
+}
+

src/lib/websocket.h

@@ -0,0 +1,36 @@
+/**
+ * Necronda Web Server
+ * WebSocket reverse proxy (header file)
+ * src/lib/websocket.h
+ * Lorenz Stechauner, 2022-08-16
+ */
+
+#ifndef NECRONDA_SERVER_WEBSOCKET_H
+#define NECRONDA_SERVER_WEBSOCKET_H
+
+#include "sock.h"
+
+#define WS_TIMEOUT 3600
+
+const char *ws_key_uuid = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
+
+typedef struct {
+    unsigned char f_fin:1;
+    unsigned char f_rsv1:1;
+    unsigned char f_rsv2:1;
+    unsigned char f_rsv3:1;
+    unsigned char opcode:4;
+    unsigned char f_mask:1;
+    unsigned long len;
+    char masking_key[4];
+} ws_frame;
+
+int ws_calc_accept_key(const char *key, char *accept_key);
+
+int ws_recv_frame_header(sock *s, ws_frame *frame);
+
+int ws_send_frame_header(sock *s, ws_frame *frame);
+
+int ws_handle_connection(sock *s1, sock *s2);
+
+#endif // NECRONDA_SERVER_WEBSOCKET_H

src/necronda.h

@@ -12,6 +12,8 @@
 #define SERVER_STR "Necronda/" NECRONDA_VERSION
 #define SERVER_STR_HTML "Necronda web server " NECRONDA_VERSION
 
+#define CHUNK_SIZE 8192
+
 #ifndef DEFAULT_HOST
 #   define DEFAULT_HOST "www.necronda.net"
 #endif

src/server.h

@@ -20,7 +20,6 @@
 #define SERVER_TIMEOUT_INIT 4
 #define SERVER_TIMEOUT 3600
 
-#define CHUNK_SIZE 8192
 
 extern int sockets[NUM_SOCKETS];
 extern pid_t children[MAX_CHILDREN];