From ef0a3abf7305133d071bf1a94a7f461082f9a9aa Mon Sep 17 00:00:00 2001
From: Werner Koch <wk@gnupg.org>
Date: Sun, 15 Mar 2015 12:15:55 +0100
Subject: [PATCH] scd: Fix possible NULL deref in apdu.c

* scd/apdu.c (control_pcsc_direct): Take care of BUFLEN being NULL.
(control_pcsc_wrapped): Ditto.
--

pcsc_vendor_specific_init calls the above with BUFFER and BUFLEN as
NULL.

Reported by Stack 0.3:

  bug: anti-dce
  model: |
    control_pcsc.exit77:
    %retval.0.i.i76 = phi i32 [ %rc.0.i.i.i73, \
            %pcsc_error_to_sw.exit.i.i74 ], [ 0, %if.end.i.i75 ]
    %tobool198 = icmp ne i32 %retval.0.i.i76, 0, !dbg !728
    br i1 %tobool198, label %if.then199, label %if.end200, !dbg !728
  stack:
    - /home/wk/s/gnupg/scd/apdu.c:1882:0
  ncore: 1
  core:
    - /home/wk/s/gnupg/scd/apdu.c:1309:0
      - buffer overflow
---
 scd/apdu.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/scd/apdu.c b/scd/apdu.c
index 5e7d27bb6..53cc4b9b3 100644
--- a/scd/apdu.c
+++ b/scd/apdu.c
@@ -1307,7 +1307,7 @@ control_pcsc_direct (int slot, pcsc_dword_t ioctl_code,
   long err;
 
   err = pcsc_control (reader_table[slot].pcsc.card, ioctl_code,
-                      cntlbuf, len, buffer, *buflen, buflen);
+                      cntlbuf, len, buffer, buflen? *buflen:0, buflen);
   if (err)
     {
       log_error ("pcsc_control failed: %s (0x%lx)\n",
@@ -1375,14 +1375,18 @@ control_pcsc_wrapped (int slot, pcsc_dword_t ioctl_code,
 
   full_len = len;
 
-  n = *buflen < len ? *buflen : len;
+  if (buflen)
+    n = *buflen < len ? *buflen : len;
+  else
+    n = 0;
   if ((i=readn (slotp->pcsc.rsp_fd, buffer, n, &len)) || len != n)
     {
       log_error ("error receiving PC/SC CONTROL response: %s\n",
                  i? strerror (errno) : "premature EOF");
       goto command_failed;
     }
-  *buflen = n;
+  if (buflen)
+    *buflen = n;
 
   full_len -= len;
   if (full_len)