diff -up ppp-2.4.5/pppd/auth.c.crypt ppp-2.4.5/pppd/auth.c
--- ppp-2.4.5/pppd/auth.c.crypt	2013-07-04 16:10:27.338463397 +0200
+++ ppp-2.4.5/pppd/auth.c	2013-07-04 16:15:00.204471203 +0200
@@ -1515,11 +1515,19 @@ check_passwd(unit, auser, userlen, apass
 		    ret = UPAP_AUTHNAK;
 		}
 	    }
+
 	    if (secret[0] != 0 && !login_secret) {
-		/* password given in pap-secrets - must match */
-		if ((cryptpap || strcmp(passwd, secret) != 0)
-		    && strcmp(crypt(passwd, secret), secret) != 0)
-		    ret = UPAP_AUTHNAK;
+		    /* password given in pap-secrets - must match */
+		    char *cryptbuf = NULL;
+		    cryptbuf = crypt(passwd, secret);
+
+		    if (cryptpap) {
+			    if ((cryptbuf == NULL) || (strcmp(cryptbuf, secret) != 0))
+				    ret = UPAP_AUTHNAK;
+		    } else {
+			    if ((strcmp(passwd, secret) != 0) && (cryptbuf == NULL || strcmp(cryptbuf, secret) != 0))
+				    ret = UPAP_AUTHNAK;
+		    }
 	    }
 	}
 	fclose(f);
diff -up ppp-2.4.5/pppd/session.c.crypt ppp-2.4.5/pppd/session.c
--- ppp-2.4.5/pppd/session.c.crypt	2009-11-16 23:26:07.000000000 +0100
+++ ppp-2.4.5/pppd/session.c	2013-07-04 16:10:27.354463397 +0200
@@ -348,9 +348,14 @@ session_start(flags, user, passwd, ttyNa
 	/*
 	 * If no passwd, don't let them login if we're authenticating.
 	 */
-        if (pw->pw_passwd == NULL || strlen(pw->pw_passwd) < 2
-            || strcmp(crypt(passwd, pw->pw_passwd), pw->pw_passwd) != 0)
+        if (pw->pw_passwd == NULL || strlen(pw->pw_passwd) < 2) {
             return SESSION_FAILED;
+        } else {
+            char *cryptbuf = NULL;
+            cryptbuf = crypt(passwd, pw->pw_passwd);
+            if ((cryptbuf == NULL) || (strcmp(cryptbuf, pw->pw_passwd) != 0))
+                return SESSION_FAILED;
+        }
     }
 
 #endif /* #ifdef USE_PAM */