owasp-modsecurity · airween · Mar 21, 2025 · Feb 19, 2025
diff --git a/.github/nginx/docs/403.html b/.github/nginx/docs/403.html
@@ -0,0 +1,10 @@
+<html>
+<head>
+<title>403</title>
+</head>
+
+<body>
+Forbidden 403 - custom error page.
+</body>
+</html>
+
diff --git a/.github/nginx/nginx.conf.redir b/.github/nginx/nginx.conf.redir
@@ -0,0 +1,90 @@
+user www-data;
+worker_processes auto;
+pid /run/nginx.pid;
+worker_cpu_affinity auto;
+
+#working_directory /tmp/cores/;
+worker_rlimit_core 2000M;
+debug_points abort;
+
+#load_module /usr/local/nginx/modules/ngx_http_modsecurity_module.so;
+
+events {
+    worker_connections 768;
+#    multi_accept on;
+#    use epoll;
+}
+
+worker_rlimit_nofile 33268;
+
+#daemon off;
+#master_process off;
+
+http {
+
+    ##
+    # Basic Settings
+    ##
+
+    types_hash_max_size 2048;
+
+    server_names_hash_bucket_size 64;
+
+    include mime.types;
+    default_type application/octet-stream;
+
+    ##
+    # Logging Settings
+    ##
+
+    #access_log /dev/stdout;
+    #error_log /dev/stdout info;
+    access_log /usr/local/nginx/logs/access.log;
+    error_log /usr/local/nginx/logs/error.log info;
+
+    server_tokens off;
+
+    proxy_hide_header X-Powered-By;
+
+    modsecurity on;
+
+    server {
+        listen          80;
+        server_name     modsectest1;
+
+        modsecurity on;
+        modsecurity_rules_file /home/runner/work/ModSecurity-nginx/ModSecurity-nginx/ModSecurity-nginx/.github/nginx/modsecurity.conf;
+        root  /usr/local/nginx/html/;
+
+        error_page 403 /403.html;
+
+        location /403.html {
+            internal;
+        }
+
+        location / {
+            try_files $uri /index.html;
+        }
+    }
+
+    server {
+        listen          80;
+        server_name     modsectest2;
+
+        modsecurity on;
+        modsecurity_rules_file /home/runner/work/ModSecurity-nginx/ModSecurity-nginx/ModSecurity-nginx/.github/nginx/modsecurity.conf;
+        root /usr/local/nginx/html/;
+
+        error_page 403 /403.html;
+
+        location /403.html {
+            internal;
+        }
+
+        location / {
+            try_files $uri /index.html;
+        }
+    }
+
+}
+
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
@@ -140,6 +140,78 @@ jobs:
             echo "FAIL"
             exit 1
           fi
+      - name: Start Nginx with redir
+        run: |
+          sudo killall nginx
+          sudo /usr/local/nginx/sbin/nginx -c /home/runner/work/ModSecurity-nginx/ModSecurity-nginx/ModSecurity-nginx/.github/nginx/nginx.conf.redir
+      - name: Run attack test vhost 1
+        run: |
+          status=$(curl -sSo /dev/null -w %{http_code} -I -X GET -H "Host: modsectest1" "http://localhost/?q=attack")
+          if [ "${status}" == "403" ]; then
+            echo "OK"
+          else
+            echo "FAIL"
+            exit 1
+          fi
+      - name: Run non-attack test vhost 1 (redir config)
+        run: |
+          status=$(curl -sSo /dev/null -w %{http_code} -I -X GET -H "Host: modsectest1" "http://localhost/?q=1")
+          if [ "${status}" == "200" ]; then
+            echo "OK"
+          else
+            echo "FAIL"
+            exit 1
+          fi
+      - name: Run attack test vhost 2 (redir config)
+        run: |
+          status=$(curl -sSo /dev/null -w %{http_code} -I -X GET -H "Host: modsectest2" "http://localhost/?q=attack")
+          if [ "${status}" == "403" ]; then
+            echo "OK"
+          else
+            echo "FAIL"
+            exit 1
+          fi
+      - name: Run non-attack test vhost 2 (redir config)
+        run: |
+          status=$(curl -sSo /dev/null -w %{http_code} -I -X GET -H "Host: modsectest2" "http://localhost/?q=1")
+          if [ "${status}" == "200" ]; then
+            echo "OK"
+          else
+            echo "FAIL"
+            exit 1
+          fi
+      - name: Run file consistency check 1 (redir config)
+        run: |
+          curl -sS "http://localhost/data50k.json" --output data50k.json
+          if [ -f data50k.json ]; then
+            diff data50k.json /usr/local/nginx/html/data50k.json > /dev/null
+            if [ $? -eq 0 ]; then
+                ls -l data50k.json /usr/local/nginx/html/data50k.json
+                echo "OK"
+            else
+                echo "FAIL"
+                exit 2
+            fi
+          else
+            echo "FAIL"
+            exit 1
+          fi
+      - name: Run file consistency check 2 (redir config)
+        run: |
+          curl -sS "http://localhost/plugged.png" --output plugged.png
+          if [ -f plugged.png ]; then
+            diff plugged.png /usr/local/nginx/html/plugged.png > /dev/null
+            if [ $? -eq 0 ]; then
+                ls -l plugged.png /usr/local/nginx/html/plugged.png
+                echo "OK"
+            else
+                echo "FAIL"
+                exit 2
+            fi
+          else
+            echo "FAIL"
+            exit 1
+          fi
 
 
   build-windows:

diff --git a/src/ngx_http_modsecurity_body_filter.c b/src/ngx_http_modsecurity_body_filter.c
@@ -50,7 +50,7 @@ ngx_http_modsecurity_body_filter(ngx_http_request_t *r, ngx_chain_t *in)
         return ngx_http_next_body_filter(r, in);
     }
 
-    ctx = ngx_http_get_module_ctx(r, ngx_http_modsecurity_module);
+    ctx = ngx_http_modsecurity_get_module_ctx(r);
 
     dd("body filter, recovering ctx: %p", ctx);
 

diff --git a/src/ngx_http_modsecurity_common.h b/src/ngx_http_modsecurity_common.h
@@ -99,6 +99,7 @@ typedef struct {
     unsigned processed:1;
     unsigned logged:1;
     unsigned intervention_triggered:1;
+    unsigned request_body_processed:1;
 } ngx_http_modsecurity_ctx_t;
 
 
@@ -139,6 +140,7 @@ extern ngx_module_t ngx_http_modsecurity_module;
 /* ngx_http_modsecurity_module.c */
 int ngx_http_modsecurity_process_intervention (Transaction *transaction, ngx_http_request_t *r, ngx_int_t early_log);
 ngx_http_modsecurity_ctx_t *ngx_http_modsecurity_create_ctx(ngx_http_request_t *r);
+ngx_http_modsecurity_ctx_t *ngx_http_modsecurity_get_module_ctx(ngx_http_request_t *r);
 char *ngx_str_to_char(ngx_str_t a, ngx_pool_t *p);
 #if (NGX_PCRE2)
 #define ngx_http_modsecurity_pcre_malloc_init(x) NULL

diff --git a/src/ngx_http_modsecurity_header_filter.c b/src/ngx_http_modsecurity_header_filter.c
@@ -109,7 +109,7 @@ ngx_http_modsecurity_store_ctx_header(ngx_http_request_t *r, ngx_str_t *name, ng
     ngx_http_modsecurity_conf_t    *mcf;
     ngx_http_modsecurity_header_t  *hdr;
 
-    ctx = ngx_http_get_module_ctx(r, ngx_http_modsecurity_module);
+    ctx = ngx_http_modsecurity_get_module_ctx(r);
     if (ctx == NULL || ctx->sanity_headers_out == NULL) {
         return NGX_ERROR;
     }
@@ -152,7 +152,7 @@ ngx_http_modsecurity_resolv_header_server(ngx_http_request_t *r, ngx_str_t name,
     ngx_str_t value;
 
     clcf = ngx_http_get_module_loc_conf(r, ngx_http_core_module);
-    ctx = ngx_http_get_module_ctx(r, ngx_http_modsecurity_module);
+    ctx = ngx_http_modsecurity_get_module_ctx(r);
 
     if (r->headers_out.server == NULL) {
         if (clcf->server_tokens) {
@@ -186,7 +186,7 @@ ngx_http_modsecurity_resolv_header_date(ngx_http_request_t *r, ngx_str_t name, o
     ngx_http_modsecurity_ctx_t *ctx = NULL;
     ngx_str_t date;
 
-    ctx = ngx_http_get_module_ctx(r, ngx_http_modsecurity_module);
+    ctx = ngx_http_modsecurity_get_module_ctx(r);
 
     if (r->headers_out.date == NULL) {
         date.data = ngx_cached_http_time.data;
@@ -216,7 +216,7 @@ ngx_http_modsecurity_resolv_header_content_length(ngx_http_request_t *r, ngx_str
     ngx_str_t value;
     char buf[NGX_INT64_LEN+2];
 
-    ctx = ngx_http_get_module_ctx(r, ngx_http_modsecurity_module);
+    ctx = ngx_http_modsecurity_get_module_ctx(r);
 
     if (r->headers_out.content_length_n > 0)
     {
@@ -243,7 +243,7 @@ ngx_http_modsecurity_resolv_header_content_type(ngx_http_request_t *r, ngx_str_t
 {
     ngx_http_modsecurity_ctx_t *ctx = NULL;
 
-    ctx = ngx_http_get_module_ctx(r, ngx_http_modsecurity_module);
+    ctx = ngx_http_modsecurity_get_module_ctx(r);
 
     if (r->headers_out.content_type.len > 0)
     {
@@ -270,7 +270,7 @@ ngx_http_modsecurity_resolv_header_last_modified(ngx_http_request_t *r, ngx_str_
     u_char buf[1024], *p;
     ngx_str_t value;
 
-    ctx = ngx_http_get_module_ctx(r, ngx_http_modsecurity_module);
+    ctx = ngx_http_modsecurity_get_module_ctx(r);
 
     if (r->headers_out.last_modified_time == -1) {
         return 1;
@@ -302,7 +302,7 @@ ngx_http_modsecurity_resolv_header_connection(ngx_http_request_t *r, ngx_str_t n
     ngx_str_t value;
 
     clcf = ngx_http_get_module_loc_conf(r, ngx_http_core_module);
-    ctx = ngx_http_get_module_ctx(r, ngx_http_modsecurity_module);
+    ctx = ngx_http_modsecurity_get_module_ctx(r);
 
     if (r->headers_out.status == NGX_HTTP_SWITCHING_PROTOCOLS) {
         connection = "upgrade";
@@ -353,7 +353,7 @@ ngx_http_modsecurity_resolv_header_transfer_encoding(ngx_http_request_t *r, ngx_
     if (r->chunked) {
         ngx_str_t value = ngx_string("chunked");
 
-        ctx = ngx_http_get_module_ctx(r, ngx_http_modsecurity_module);
+        ctx = ngx_http_modsecurity_get_module_ctx(r);
 
 #if defined(MODSECURITY_SANITY_CHECKS) && (MODSECURITY_SANITY_CHECKS)
         ngx_http_modsecurity_store_ctx_header(r, &name, &value);
@@ -380,7 +380,7 @@ ngx_http_modsecurity_resolv_header_vary(ngx_http_request_t *r, ngx_str_t name, o
     if (r->gzip_vary && clcf->gzip_vary) {
         ngx_str_t value = ngx_string("Accept-Encoding");
 
-        ctx = ngx_http_get_module_ctx(r, ngx_http_modsecurity_module);
+        ctx = ngx_http_modsecurity_get_module_ctx(r);
 
 #if defined(MODSECURITY_SANITY_CHECKS) && (MODSECURITY_SANITY_CHECKS)
         ngx_http_modsecurity_store_ctx_header(r, &name, &value);
@@ -422,7 +422,7 @@ ngx_http_modsecurity_header_filter(ngx_http_request_t *r)
 
 /* XXX: if NOT_MODIFIED, do we need to process it at all?  see xslt_header_filter() */
 
-    ctx = ngx_http_get_module_ctx(r, ngx_http_modsecurity_module);
+    ctx = ngx_http_modsecurity_get_module_ctx(r);
 
     dd("header filter, recovering ctx: %p", ctx);
 

diff --git a/src/ngx_http_modsecurity_log.c b/src/ngx_http_modsecurity_log.c
@@ -41,17 +41,9 @@ ngx_http_modsecurity_log_handler(ngx_http_request_t *r)
 {
     ngx_pool_t                   *old_pool;
     ngx_http_modsecurity_ctx_t   *ctx;
-    ngx_http_modsecurity_conf_t  *mcf;
 
     dd("catching a new _log_ phase handler");
 
-    mcf = ngx_http_get_module_loc_conf(r, ngx_http_modsecurity_module);
-    if (mcf == NULL || mcf->enable != 1)
-    {
-        dd("ModSecurity not enabled... returning");
-        return NGX_OK;
-    }
-
     /*
     if (r->method != NGX_HTTP_GET &&
         r->method != NGX_HTTP_POST && r->method != NGX_HTTP_HEAD) {
@@ -60,13 +52,13 @@ ngx_http_modsecurity_log_handler(ngx_http_request_t *r)
         return NGX_OK;
     }
     */
-    ctx = ngx_http_get_module_ctx(r, ngx_http_modsecurity_module);
+    ctx = ngx_http_modsecurity_get_module_ctx(r);
 
     dd("recovering ctx: %p", ctx);
 
     if (ctx == NULL) {
-        dd("something really bad happened here. returning NGX_ERROR");
-        return NGX_ERROR;
+        dd("ModSecurity not enabled or error occurred");
+        return NGX_OK;
     }
 
     if (ctx->logged) {

diff --git a/src/ngx_http_modsecurity_module.c b/src/ngx_http_modsecurity_module.c
@@ -149,7 +149,7 @@ ngx_http_modsecurity_process_intervention (Transaction *transaction, ngx_http_re
 
     dd("processing intervention");
 
-    ctx = ngx_http_get_module_ctx(r, ngx_http_modsecurity_module);
+    ctx = ngx_http_modsecurity_get_module_ctx(r);
     if (ctx == NULL)
     {
         return NGX_HTTP_INTERNAL_SERVER_ERROR;
@@ -313,6 +313,27 @@ ngx_http_modsecurity_create_ctx(ngx_http_request_t *r)
     return ctx;
 }
 
+ngx_inline ngx_http_modsecurity_ctx_t *
+ngx_http_modsecurity_get_module_ctx(ngx_http_request_t *r)
+{
+    ngx_http_modsecurity_ctx_t *ctx;
+    ctx = ngx_http_get_module_ctx(r, ngx_http_modsecurity_module);
+    if (ctx == NULL) {
+        /*
+         * refer <nginx>/src/http/modules/ngx_http_realip_module.c
+         * if module context was reset, the original address
+         * can still be found in the cleanup handler
+         */
+        ngx_pool_cleanup_t *cln;
+        for (cln = r->pool->cleanup; cln; cln = cln->next) {
+            if (cln->handler == ngx_http_modsecurity_cleanup) {
+                ctx = cln->data;
+                break;
+            }
+        }
+    }
+    return ctx;
+}
 
 char *
 ngx_conf_set_rules(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)

diff --git a/src/ngx_http_modsecurity_pre_access.c b/src/ngx_http_modsecurity_pre_access.c
@@ -27,7 +27,7 @@ ngx_http_modsecurity_request_read(ngx_http_request_t *r)
 {
     ngx_http_modsecurity_ctx_t *ctx;
 
-    ctx = ngx_http_get_module_ctx(r, ngx_http_modsecurity_module);
+    ctx = ngx_http_modsecurity_get_module_ctx(r);
 
 #if defined(nginx_version) && nginx_version >= 8011
     r->main->count--;
@@ -70,7 +70,7 @@ ngx_http_modsecurity_pre_access_handler(ngx_http_request_t *r)
     }
     */
 
-    ctx = ngx_http_get_module_ctx(r, ngx_http_modsecurity_module);
+    ctx = ngx_http_modsecurity_get_module_ctx(r);
 
     dd("recovering ctx: %p", ctx);
 
@@ -80,6 +80,11 @@ ngx_http_modsecurity_pre_access_handler(ngx_http_request_t *r)
         return NGX_HTTP_INTERNAL_SERVER_ERROR;
     }
 
+    if (ctx->request_body_processed) {
+        // should we use r->internal or r->filter_finalize?
+        return NGX_DECLINED;
+    }
+
     if (ctx->intervention_triggered) {
         return NGX_DECLINED;
     }
@@ -212,6 +217,7 @@ ngx_http_modsecurity_pre_access_handler(ngx_http_request_t *r)
 
         old_pool = ngx_http_modsecurity_pcre_malloc_init(r->pool);
         msc_process_request_body(ctx->modsec_transaction);
+        ctx->request_body_processed = 1;
         ngx_http_modsecurity_pcre_malloc_done(old_pool);
 
         ret = ngx_http_modsecurity_process_intervention(ctx->modsec_transaction, r, 0);

diff --git a/src/ngx_http_modsecurity_rewrite.c b/src/ngx_http_modsecurity_rewrite.c
@@ -46,7 +46,7 @@ ngx_http_modsecurity_rewrite_handler(ngx_http_request_t *r)
 
     dd("catching a new _rewrite_ phase handler");
 
-    ctx = ngx_http_get_module_ctx(r, ngx_http_modsecurity_module);
+    ctx = ngx_http_modsecurity_get_module_ctx(r);
 
     dd("recovering ctx: %p", ctx);