FTP: allow "rubbish" prepended to the SIZE response

This is a protocol violation but apparently there are legacy proprietary
servers doing this.

Added test 336 and 337 to verify.

Reported-by: Philippe Marguinaud
Closes #4339

1 files changed, 18 insertions, 2 deletions

diff --git a/lib/ftp.c b/lib/ftp.c
index 0793dc1f3..00233a80d 100644
--- a/lib/ftp.c
+++ b/lib/ftp.c
@@ -2244,9 +2244,25 @@ static CURLcode ftp_state_size_resp(struct connectdata *conn,
   char *buf = data->state.buffer;
 
   /* get the size from the ascii string: */
-  if(ftpcode == 213)
+  if(ftpcode == 213) {
+    /* To allow servers to prepend "rubbish" in the response string, we scan
+       for all the digits at the end of the response and parse only those as a
+       number. */
+    char *start = &buf[4];
+    char *fdigit = strchr(start, '\r');
+    if(fdigit) {
+      do
+        fdigit--;
+      while(ISDIGIT(*fdigit) && (fdigit > start));
+      if(!ISDIGIT(*fdigit))
+        fdigit++;
+    }
+    else
+      fdigit = start;
     /* ignores parsing errors, which will make the size remain unknown */
-    (void)curlx_strtoofft(buf + 4, NULL, 0, &filesize);
+    (void)curlx_strtoofft(fdigit, NULL, 0, &filesize);
+
+  }
 
   if(instate == FTP_SIZE) {
 #ifdef CURL_FTP_HTTPSTYLE_HEAD