Merge pull request #253 from Castaglia/ftp-interop-feat-blank-lines

Issue #251: Handle an interoperability edge case, where some specific…
Castaglia · Jul 23, 2023 · 5d35be6 · 5d35be6
2 parents ca6650e + 322e00d
commit 5d35be6
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Showing 3 changed files with 22 additions and 5 deletions.
diff --git a/include/proxy/ftp/ctrl.h b/include/proxy/ftp/ctrl.h
@@ -1,6 +1,6 @@
 /*
  * ProFTPD - mod_proxy FTP control conn API
- * Copyright (c) 2012-2020 TJ Saunders
+ * Copyright (c) 2012-2023 TJ Saunders
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -28,7 +28,9 @@
 #include "mod_proxy.h"
 
 /* Note: this flag is only used for testing. */
-#define PROXY_FTP_CTRL_FL_IGNORE_EOF	0x0001
+#define PROXY_FTP_CTRL_FL_IGNORE_EOF		0x0001
+
+#define PROXY_FTP_CTRL_FL_IGNORE_BLANK_RESP	0x0002
 
 int proxy_ftp_ctrl_handle_async(pool *p, conn_t *backend_conn,
   conn_t *frontend_conn, int flags);

diff --git a/lib/proxy/ftp/ctrl.c b/lib/proxy/ftp/ctrl.c
@@ -175,6 +175,13 @@ pr_response_t *proxy_ftp_ctrl_recv_resp(pool *p, conn_t *ctrl_conn,
       buflen--;
     }
 
+    if (buflen == 0 &&
+        (flags & PROXY_FTP_CTRL_FL_IGNORE_BLANK_RESP)) {
+      pr_trace_msg(trace_channel, 19, "%s",
+        "skipping blank response line from backend server");
+      continue;
+    }
+
     /* If we are the first line of the response, the first three characters
      * MUST be numeric, followed by a hypen.  Anything else is nonconformant
      * with RFC 959.

diff --git a/lib/proxy/ftp/sess.c b/lib/proxy/ftp/sess.c
@@ -1,6 +1,6 @@
 /*
  * ProFTPD - mod_proxy FTP session routines
- * Copyright (c) 2013-2022 TJ Saunders
+ * Copyright (c) 2013-2023 TJ Saunders
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -100,7 +100,7 @@ static int parse_feat(pool *p, const char *feat, array_header **res) {
 
 int proxy_ftp_sess_get_feat(pool *p, const struct proxy_session *proxy_sess) {
   pool *tmp_pool;
-  int res, xerrno = 0;
+  int flags, res, xerrno = 0;
   cmd_rec *cmd;
   pr_response_t *resp;
   unsigned int resp_nlines = 0;
@@ -129,8 +129,16 @@ int proxy_ftp_sess_get_feat(pool *p, const struct proxy_session *proxy_sess) {
     return -1;
   }
 
+  /* Some broken FTP servers actually send blank lines in responses, such
+   * as in a FEAT response.  Ugh.  (See Issue #251.)
+   *
+   * TODO: Should this use some sort of "enable compatibility with broken/
+   * non-conformat servrs" ProxyOption/flag?
+   */
+  flags = PROXY_FTP_CTRL_FL_IGNORE_BLANK_RESP;
+
   resp = proxy_ftp_ctrl_recv_resp(tmp_pool, proxy_sess->backend_ctrl_conn,
-    &resp_nlines, 0);
+    &resp_nlines, flags);
   if (resp == NULL) {
     xerrno = errno;