pppd: Don't crash if crypt() returns NULL

It is possible for crypt() to return NULL under some circumstances,
so we need to check the return value before passing it to strcmp().
If we do get NULL from crypt(), treat it as an authentication failure.

Reported-by: Paul Wouters <pwouters@redhat.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

diff --git a/pppd/auth.c b/pppd/auth.c
index fb719446f7489895f0b51081c99b99c8221fd210..883b7f5bb8aedfec061daa37b7bb2e4eabf15de8 100644 (file)
--- a/pppd/auth.c
+++ b/pppd/auth.c
@@ -1442,9 +1442,11 @@ check_passwd(unit, auser, userlen, apasswd, passwdlen, msg)
            }
            if (secret[0] != 0 && !login_secret) {
                /* password given in pap-secrets - must match */
            }
            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;
+               if (cryptpap || strcmp(passwd, secret) != 0) {
+                   char *cbuf = crypt(passwd, secret);
+                   if (!cbuf || strcmp(cbuf, secret) != 0)
+                       ret = UPAP_AUTHNAK;
+               }

            }
        }
        fclose(f);
            }
        }
        fclose(f);

diff --git a/pppd/session.c b/pppd/session.c
index 32901a24546f5913b67cdced816f002de9edc6e3..56385dd638742ba9fd7028165104e8565cff0778 100644 (file)
--- a/pppd/session.c
+++ b/pppd/session.c
@@ -178,6 +178,7 @@ session_start(flags, user, passwd, ttyName, msg)
     bool try_session = 0;
 #else /* #ifdef USE_PAM */
     struct passwd *pw;
     bool try_session = 0;
 #else /* #ifdef USE_PAM */
     struct passwd *pw;

+    char *cbuf;

 #ifdef HAS_SHADOW
     struct spwd *spwd;
     struct spwd *getspnam();
 #ifdef HAS_SHADOW
     struct spwd *spwd;
     struct spwd *getspnam();


@@ -348,8 +349,10 @@ session_start(flags, user, passwd, ttyName, msg)
        /*
         * If no passwd, don't let them login if we're authenticating.
         */
        /*
         * 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;
+       cbuf = crypt(passwd, pw->pw_passwd);
+       if (!cbuf || strcmp(cbuf, pw->pw_passwd) != 0)

             return SESSION_FAILED;
     }
 
             return SESSION_FAILED;
     }