Dan Nelson added the CURLOPT_FTP_ALTERNATIVE_TO_USER libcurl option and curl

tool option named --ftp-alternative-to-user. It provides a mean to send a
particular command if the normal USER/PASS approach fails.

3 files changed, 22 insertions, 2 deletions

diff --git a/lib/ftp.c b/lib/ftp.c
index c27030504..c17d9fbaa 100644
--- a/lib/ftp.c
+++ b/lib/ftp.c
@@ -699,6 +699,7 @@ static CURLcode ftp_state_user(struct connectdata *conn)
   NBFTPSENDF(conn, "USER %s", ftp->user?ftp->user:"");
 
   state(conn, FTP_USER);
+  conn->data->state.ftp_trying_alternative = FALSE;
 
   return CURLE_OK;
 }
@@ -2302,8 +2303,19 @@ static CURLcode ftp_state_user_resp(struct connectdata *conn,
 
     530 User ... access denied
     (the server denies to log the specified user) */
-    failf(data, "Access denied: %03d", ftpcode);
-    result = CURLE_LOGIN_DENIED;
+
+    if (conn->data->set.ftp_alternative_to_user &&
+        !conn->data->state.ftp_trying_alternative) {
+      /* Ok, USER failed.  Let's try the supplied command. */
+      NBFTPSENDF(conn, "%s", conn->data->set.ftp_alternative_to_user);
+      conn->data->state.ftp_trying_alternative = TRUE;
+      state(conn, FTP_USER);
+      result = CURLE_OK;
+    }
+    else {
+      failf(data, "Access denied: %03d", ftpcode);
+      result = CURLE_LOGIN_DENIED;
+    }
   }
   return result;
 }
diff --git a/lib/url.c b/lib/url.c
index 17e3a7f57..b25d02be8 100644
--- a/lib/url.c
+++ b/lib/url.c
@@ -1546,6 +1546,10 @@ CURLcode Curl_setopt(struct SessionHandle *data, CURLoption option,
     data->set.connect_only = va_arg(param, long)?TRUE:FALSE;
     break;
 
+  case CURLOPT_FTP_ALTERNATIVE_TO_USER:
+    data->set.ftp_alternative_to_user = va_arg(param, char *);
+    break;
+
   default:
     /* unknown tag and its companion, just ignore: */
     result = CURLE_FAILED_INIT; /* correct this */
diff --git a/lib/urldata.h b/lib/urldata.h
index 63ccfe70a..c804105b6 100644
--- a/lib/urldata.h
+++ b/lib/urldata.h
@@ -937,6 +937,9 @@ struct UrlState {
   /* a place to store the most recenlty set FTP entrypath */
   char *most_recent_ftp_entrypath;
 
+  /* set after initial USER failure, to prevent an authentication loop */
+  bool ftp_trying_alternative;
+
 #ifndef WIN32
 /* do FTP line-end conversions on most platforms */
 #define CURL_DO_LINEEND_CONV
@@ -1054,6 +1057,7 @@ struct UserDefined {
   bool cookiesession;   /* new cookie session? */
   bool crlf;            /* convert crlf on ftp upload(?) */
   char *ftp_account;    /* ftp account data */
+  char *ftp_alternative_to_user;   /* command to send if USER/PASS fails */
   struct curl_slist *quote;     /* after connection is established */
   struct curl_slist *postquote; /* after the transfer */
   struct curl_slist *prequote; /* before the transfer, after type */