Re: [patch] login_yubikey: delete keys

[fritjof]

On Thu, Mar 31, 2016 at 10:17:45PM +0200, Sebastian Benoit wrote:
> Hi Fritjof,
> 
> frit...@alokat.org(frit...@alokat.org) on 2016.03.31 11:43:58 +0200:
> > Wipe out the key from "user.key".
> > 
> > --f.
> > 
> The while loop above has return(AUTH_FAILED) so you dont zero in those
> cases. Can you change that?
> 

Yeah, sure. See patch below.

> 
> Also your diff does not apply, i think it has tab vs space issues.
> 

Ah, shit. Should work now.


Index: login_yubikey.c
===================================================================
RCS file: /cvs/src/libexec/login_yubikey/login_yubikey.c,v
retrieving revision 1.13
diff -u -r1.13 login_yubikey.c
--- login_yubikey.c     22 Oct 2015 23:56:30 -0000      1.13
+++ login_yubikey.c     31 Mar 2016 21:35:28 -0000
@@ -228,6 +228,8 @@
        yubikey_hex_decode(uid, hexuid, YUBIKEY_UID_SIZE);
        yubikey_hex_decode(key, hexkey, YUBIKEY_KEY_SIZE);
 
+       explicit_bzero(hexkey, sizeof(hexkey));
+
        /*
         * Cycle through the key mapping table.
          * XXX brute force, unoptimized; a lookup table for valid mappings may
@@ -239,6 +241,7 @@
                case EMSGSIZE:
                        syslog(LOG_INFO, "user %s failed: password too short.",
                            username);
+                       explicit_bzero(key, sizeof(key));
                        return (AUTH_FAILED);
                case EINVAL:    /* keyboard mapping invalid */
                        continue;
@@ -264,14 +267,18 @@
                        syslog(LOG_INFO, "user %s: could not decode password "
                            "with any keymap (%d crc ok)",
                            username, crcok);
+                       explicit_bzero(key, sizeof(key));
                        return (AUTH_FAILED);
                default:
                        syslog(LOG_DEBUG, "user %s failed: %s",
                            username, strerror(r));
+                       explicit_bzero(key, sizeof(key));
                        return (AUTH_FAILED);
                }
                break; /* only reached through the bottom of case 0 */
        }
+
+       explicit_bzero(key, sizeof(key));
 
        syslog(LOG_INFO, "user %s uid %s: %d matching keymaps (%d checked), "
            "%d crc ok", username, hexuid, mapok, i, crcok);