Staring from glibc 2.17 the crypt() function will error out and return NULL if
the seed or "correct" is invalid. The failure case for this is the sudo user
having a locked account in /etc/shadow, so their password is "!", which is an
invalid hash.  crypt() never returned NULL previously so this is crashing in
strcmp().

Upstream-Status: Pending
Signed-off-by: Ross Burton <ross.burton@intel.com>

Index: sudo-1.8.6p7/plugins/sudoers/auth/passwd.c
===================================================================
--- sudo-1.8.6p7.orig/plugins/sudoers/auth/passwd.c	2013-04-11 15:26:28.456416867 +0100
+++ sudo-1.8.6p7/plugins/sudoers/auth/passwd.c	2013-04-11 15:31:31.156421718 +0100
@@ -96,7 +96,9 @@
      */
     epass = (char *) crypt(pass, pw_epasswd);
     pass[8] = sav;
-    if (HAS_AGEINFO(pw_epasswd, pw_len) && strlen(epass) == DESLEN)
+    if (epass == NULL)
+	error = AUTH_FAILURE;
+    else if (HAS_AGEINFO(pw_epasswd, pw_len) && strlen(epass) == DESLEN)
 	error = strncmp(pw_epasswd, epass, DESLEN);
     else
 	error = strcmp(pw_epasswd, epass);