kdm, kcheckpass: Check for NULL return from crypt(3) and friends.

Potential issue noted and fixed by Mancha <mancha1@hush.com>.

Patch reviewed by myself and ossi. Review request was closed out by the
backport commit.

kcheckpass/checkpass_etcpasswd.c

@@ -35,6 +35,7 @@ AuthReturn Authenticate(const char *method,
 {
   struct passwd *pw;
   char *passwd;
+  char *crpt_passwd;
 
   if (strcmp(method, "classic"))
     return AuthError;
@@ -49,7 +50,7 @@ AuthReturn Authenticate(const char *method,
   if (!(passwd = conv(ConvGetHidden, 0)))
     return AuthAbort;
 
-  if (!strcmp(pw->pw_passwd, crypt(passwd, pw->pw_passwd))) {
+  if ((crpt_passwd = crypt(passwd, pw->pw_passwd)) && !strcmp(pw->pw_passwd, crpt_passwd)) {
     dispose(passwd);
     return AuthOk; /* Success */
   }

kcheckpass/checkpass_osfc2passwd.c

@@ -38,6 +38,7 @@ AuthReturn Authenticate(const char *method,
         const char *login, char *(*conv) (ConvRequest, const char *))
 {
   char *passwd;
+  char *crpt_passwd;
   char c2passwd[256];
 
   if (strcmp(method, "classic"))
@@ -52,7 +53,7 @@ AuthReturn Authenticate(const char *method,
   if (!(passwd = conv(ConvGetHidden, 0)))
     return AuthAbort;
 
-  if (!strcmp(c2passwd, osf1c2crypt(passwd, c2passwd))) {
+  if ((crpt_passwd = osf1c2crypt(passwd, c2passwd)) && !strcmp(c2passwd, crpt_passwd)) {
     dispose(passwd);
     return AuthOk; /* Success */
   }

kcheckpass/checkpass_shadow.c

@@ -69,7 +69,7 @@ AuthReturn Authenticate(const char *method,
   crpt_passwd = crypt(typed_in_password, password);
 #endif
 
-  if (!strcmp(password, crpt_passwd )) {
+  if (crpt_passwd && !strcmp(password, crpt_passwd )) {
     dispose(typed_in_password);
     return AuthOk; /* Success */
   }

kdm/backend/client.c

@@ -540,6 +540,9 @@ verify(GConvFunc gconv, int rootok)
 # if defined(HAVE_STRUCT_PASSWD_PW_EXPIRE) || defined(USESHADOW)
     int tim, expir, warntime, quietlog;
 # endif
+# if !defined(ultrix) && !defined(__ultrix__) && (defined(HAVE_PW_ENCRYPT) || defined(HAVE_CRYPT))
+    char *crpt_passwd;
+# endif
 #endif
 
     debug("verify ...\n");
@@ -752,9 +755,9 @@ verify(GConvFunc gconv, int rootok)
 # if defined(ultrix) || defined(__ultrix__)
     if (authenticate_user(p, curpass, 0) < 0)
 # elif defined(HAVE_PW_ENCRYPT)
-    if (strcmp(pw_encrypt(curpass, p->pw_passwd), p->pw_passwd))
+    if (!(crpt_passwd = pw_encrypt(curpass, p->pw_passwd)) || strcmp(crpt_passwd, p->pw_passwd))
 # elif defined(HAVE_CRYPT)
-    if (strcmp(crypt(curpass, p->pw_passwd), p->pw_passwd))
+    if (!(crpt_passwd = crypt(curpass, p->pw_passwd)) || strcmp(crpt_passwd, p->pw_passwd))
 # else
     if (strcmp(curpass, p->pw_passwd))
 # endif