[BB#17] Add custom HTTP request headers to outgoing HTTP requests

docs/man5/tinyproxy.conf.txt.in

@@ -219,6 +219,17 @@ The possible keywords and their descriptions are as follows:
     like `host.example.com` or a domain name like `.example.com` or
     even a top level domain name like `.com`.
 
+*AddHeader*::
+
+    Configure one or more HTTP request headers to be added to outgoing
+    HTTP requests that Tinyproxy makes. Note that this option will not
+    work for HTTPS traffic, as Tinyproxy has no control over what
+    headers are exchanged.
+    +
+----
+AddHeader "X-My-Header" "Powered by Tinyproxy"
+----
+
 *ViaProxyName*::
 
     RFC 2616 requires proxies to add a `Via` header to the HTTP

etc/tinyproxy.conf.in

@@ -209,6 +209,13 @@ MaxRequestsPerChild 0
 #
 Allow 127.0.0.1
 
+#
+# AddHeader: Adds the specified headers to outgoing HTTP requests that
+# Tinyproxy makes. Note that this option will not work for HTTPS
+# traffic, as Tinyproxy has no control over what headers are exchanged.
+#
+#AddHeader "X-My-Header" "Powered by Tinyproxy"
+
 #
 # ViaProxyName: The "Via" header is required by the HTTP RFC, but using
 # the real host name is a security concern.  If the following directive

src/conf.c

@@ -123,6 +123,7 @@ static HANDLE_FUNC (handle_connectport);
 static HANDLE_FUNC (handle_defaulterrorfile);
 static HANDLE_FUNC (handle_deny);
 static HANDLE_FUNC (handle_errorfile);
+static HANDLE_FUNC (handle_addheader);
 #ifdef FILTER_ENABLE
 static HANDLE_FUNC (handle_filter);
 static HANDLE_FUNC (handle_filtercasesensitive);
@@ -226,8 +227,10 @@ struct {
         STDCONF ("deny", "(" "(" IPMASK "|" IPV6MASK ")" "|" ALNUM ")",
                  handle_deny),
         STDCONF ("bind", "(" IP "|" IPV6 ")", handle_bind),
-        /* error files */
+        /* other */
         STDCONF ("errorfile", INT WS STR, handle_errorfile),
+        STDCONF ("addheader",  STR WS STR, handle_addheader),
+
 #ifdef FILTER_ENABLE
         /* filtering */
         STDCONF ("filter", STR, handle_filter),
@@ -260,6 +263,22 @@ struct {
 
 const unsigned int ndirectives = sizeof (directives) / sizeof (directives[0]);
 
+static void
+free_added_headers (vector_t add_headers)
+{
+        ssize_t i;
+
+        for (i = 0; i < vector_length (add_headers); i++) {
+                http_header_t *header = (http_header_t *)
+                        vector_getentry (add_headers, i, NULL);
+
+                safefree (header->name);
+                safefree (header->value);
+        }
+
+        vector_delete (add_headers);
+}
+
 static void free_config (struct config_s *conf)
 {
         safefree (conf->config_file);
@@ -282,6 +301,7 @@ static void free_config (struct config_s *conf)
         safefree (conf->bind_address);
         safefree (conf->via_proxy_name);
         hashmap_delete (conf->errorpages);
+        free_added_headers (conf->add_headers);
         safefree (conf->errorpage_undef);
         safefree (conf->statpage);
         flush_access_list (conf->access_list);
@@ -848,6 +868,30 @@ static HANDLE_FUNC (handle_errorfile)
         return 0;
 }
 
+static HANDLE_FUNC (handle_addheader)
+{
+        char *name = get_string_arg (line, &match[2]);
+        char *value = get_string_arg (line, &match[3]);
+        http_header_t *header;
+
+        if (!conf->add_headers) {
+                conf->add_headers = vector_create ();
+        }
+
+        header = (http_header_t *) safemalloc (sizeof (http_header_t));
+        header->name = name;
+        header->value = value;
+
+        vector_prepend (conf->add_headers, header, sizeof *header);
+
+        safefree (header);
+
+        /* Don't free name or value here, as they are referenced in the
+         * struct inserted into the vector. */
+
+        return 0;
+}
+
 /*
  * Log level's strings.
  */

src/conf.h

@@ -25,6 +25,14 @@
 #include "hashmap.h"
 #include "vector.h"
 
+/*
+ * Stores a HTTP header created using the AddHeader directive.
+ */
+typedef struct {
+        char *name;
+        char *value;
+} http_header_t;
+
 /*
  * Hold all the configuration time information.
  */
@@ -97,6 +105,11 @@ struct config_s {
          * anonymous feature is turned on.
          */
         hashmap_t anonymous_map;
+
+        /*
+         * Extra headers to be added to outgoing HTTP requests.
+         */
+        vector_t add_headers;
 };
 
 extern int reload_config_file (const char *config_fname, struct config_s *conf,

src/reqs.c

@@ -1327,6 +1327,7 @@ connect_to_upstream (struct conn_s *connptr, struct request_s *request)
  */
 void handle_connection (int fd)
 {
+        ssize_t i;
         struct conn_s *connptr;
         struct request_s *request = NULL;
         hashmap_t hashofheaders = NULL;
@@ -1407,6 +1408,19 @@ void handle_connection (int fd)
                 return;
         }
 
+        /*
+         * Add any user-specified headers (AddHeader directive) to the
+         * outgoing HTTP request.
+         */
+        for (i = 0; i < vector_length (config.add_headers); i++) {
+                http_header_t *header = (http_header_t *)
+                        vector_getentry (config.add_headers, i, NULL);
+
+                hashmap_insert (hashofheaders,
+                                header->name,
+                                header->value, strlen (header->value) + 1);
+        }
+
         request = process_request (connptr, hashofheaders);
         if (!request) {
                 if (!connptr->error_variables && !connptr->show_stats) {