net/http: Error out on headers with LF without CR

In a similar vein to the previous patch, parse_line() would write
a NUL byte past the end of the buffer if there was an HTTP header
with a LF rather than a CRLF.

RFC-2616 says:

  Many HTTP/1.1 header field values consist of words separated by LWS
  or special characters. These special characters MUST be in a quoted
  string to be used within a parameter value (as defined in section 3.6).

We don't support quoted sections or continuation lines, etc.

If we see an LF that's not part of a CRLF, bail out.

Fixes: CVE-2022-28734

Signed-off-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

grub-core/net/http.c

@@ -68,7 +68,15 @@ parse_line (grub_file_t file, http_data_t data, char *ptr, grub_size_t len)
   char *end = ptr + len;
   while (end > ptr && *(end - 1) == '\r')
     end--;
+
+  /* LF without CR. */
+  if (end == ptr + len)
+    {
+      data->errmsg = grub_strdup (_("invalid HTTP header - LF without CR"));
+      return GRUB_ERR_NONE;
+    }
   *end = 0;
+
   /* Trailing CRLF.  */
   if (data->in_chunk_len == 1)
     {