From: Paul Mackerras <paulus@samba.org>
Date: Sun, 20 May 2012 04:14:55 +0000 (+1000)
Subject: pppd: Don't crash if crypt() returns NULL
X-Git-Tag: ppp-2.4.7~37
X-Git-Url: https://git.ozlabs.org/?p=ppp.git;a=commitdiff_plain;h=04c4348108d847e034dd91066cc6843f60d71731;hp=80a8e2ce257ca12cce723519a0f20ea1d663b14a

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 fb71944..883b7f5 100644
--- 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 ((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);
diff --git a/pppd/session.c b/pppd/session.c
index 32901a2..56385dd 100644
--- 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;
+    char *cbuf;
 #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 (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;
     }