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+/*
+ * Copyright (c) 1989 - 1993, Julianne Frances Haugh
+ * Copyright (c) 1996 - 1999, Marek Michałkiewicz
+ * Copyright (c) 2003 - 2005, Tomasz Kłoczko
+ * Copyright (c) 2007 - 2008, Nicolas François
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. The name of the copyright holders or contributors may not be used to
+ * endorse or promote products derived from this software without
+ * specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+ * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <config.h>
+
+#ident "$Id$"
+
+#include <sys/types.h>
+#include <stdio.h>
+#include "prototypes.h"
+#include "defines.h"
+#include <pwd.h>
+/*
+ * valid - compare encrypted passwords
+ *
+ * Valid() compares the DES encrypted password from the password file
+ * against the password which the user has entered after it has been
+ * encrypted using the same salt as the original. Entries which do
+ * not have a password file entry have a NULL pw_name field and this
+ * is used to indicate that a dummy salt must be used to encrypt the
+ * password anyway.
+ */
+bool valid (const char *password, const struct passwd *ent)
+{
+ const char *encrypted;
+ /*@observer@*/const char *salt;
+
+ /*
+ * Start with blank or empty password entries. Always encrypt
+ * a password if no such user exists. Only if the ID exists and
+ * the password is really empty do you return quickly. This
+ * routine is meant to waste CPU time.
+ */
+
+ if ((NULL != ent->pw_name) && ('\0' == ent->pw_passwd[0])) {
+ if ('\0' == password[0]) {
+ return true; /* user entered nothing */
+ } else {
+ return false; /* user entered something! */
+ }
+ }
+
+ /*
+ * If there is no entry then we need a salt to use.
+ */
+
+ if ((NULL == ent->pw_name) || ('\0' == ent->pw_passwd[0])) {
+ salt = "xx";
+ } else {
+ salt = ent->pw_passwd;
+ }
+
+ /*
+ * Now, perform the encryption using the salt from before on
+ * the users input. Since we always encrypt the string, it
+ * should be very difficult to determine if the user exists by
+ * looking at execution time.
+ */
+
+ encrypted = pw_encrypt (password, salt);
+
+ /*
+ * One last time we must deal with there being no password file
+ * entry for the user. We use the pw_name == NULL idiom to
+ * cause non-existent users to not be validated.
+ */
+
+ if ( (NULL != ent->pw_name)
+ && (NULL != encrypted)
+ && (strcmp (encrypted, ent->pw_passwd) == 0)) {
+ return true;
+ } else {
+ return false;
+ }
+}
+