From 74287f5df9966a0648b4a68417451dd18f079ab8 Mon Sep 17 00:00:00 2001

From: "djm@openbsd.org" <djm@openbsd.org>

Date: Tue, 31 Jul 2018 03:10:27 +0000

Subject: [PATCH] upstream: delay bailout for invalid authentic

=?UTF-8?q?ating=20user=20until=20after=20the=20packet=20containing=20the?=

=?UTF-8?q?=20request=20has=20been=20fully=20parsed.=20Reported=20by=20Dar?=

=?UTF-8?q?iusz=20Tytko=20and=20Micha=C5=82=20Sajdak;=20ok=20deraadt?=

MIME-Version: 1.0

Content-Type: text/plain; charset=UTF-8

Content-Transfer-Encoding: 8bit

OpenBSD-Commit-ID: b4891882fbe413f230fe8ac8a37349b03bd0b70d

---

 auth2-gss.c       | 11 +++++++----

 auth2-hostbased.c | 11 ++++++-----

 auth2-pubkey.c    | 25 +++++++++++++++----------

 3 files changed, 28 insertions(+), 19 deletions(-)

diff --git a/auth2-gss.c b/auth2-gss.c

index 47308c5ce..9351e0428 100644

--- a/auth2-gss.c

+++ b/auth2-gss.c

@@ -70,9 +70,6 @@ userauth_gssapi(struct ssh *ssh)

 	u_int len;

 	u_char *doid = NULL;

-	if (!authctxt->valid || authctxt->user == NULL)

-		return (0);

-

 	mechs = packet_get_int();

 	if (mechs == 0) {

 		debug("Mechanism negotiation is not supported");

@@ -106,6 +103,12 @@ userauth_gssapi(struct ssh *ssh)

 		return (0);

 	}

+	if (!authctxt->valid || authctxt->user == NULL) {

+		debug2("%s: disabled because of invalid user", __func__);

+		free(doid);

+		return (0);

+	}

+

 	if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) {

 		if (ctxt != NULL)

 			ssh_gssapi_delete_ctx(&ctxt);

diff --git a/auth2-hostbased.c b/auth2-hostbased.c

index 60159a56c..359393291 100644

--- a/auth2-hostbased.c

+++ b/auth2-hostbased.c

@@ -67,10 +67,6 @@ userauth_hostbased(struct ssh *ssh)

 	int pktype;

 	int authenticated = 0;

-	if (!authctxt->valid) {

-		debug2("userauth_hostbased: disabled because of invalid user");

-		return 0;

-	}

 	pkalg = packet_get_string(&alen;;

 	pkblob = packet_get_string(&blen);

 	chost = packet_get_string(NULL);

@@ -117,6 +113,11 @@ userauth_hostbased(struct ssh *ssh)

 		goto done;

 	}

+	if (!authctxt->valid || authctxt->user == NULL) {

+		debug2("%s: disabled because of invalid user", __func__);

+		goto done;

+	}

+

 	service = datafellows & SSH_BUG_HBSERVICE ? "ssh-userauth" :

 	    authctxt->service;

 	buffer_init(&b);

diff --git a/auth2-pubkey.c b/auth2-pubkey.c

index c4d0f7908..e1c150401 100644

--- a/auth2-pubkey.c

+++ b/auth2-pubkey.c

@@ -89,16 +89,12 @@ userauth_pubkey(struct ssh *ssh)

 {

 	Buffer b;

 	Key *key = NULL;

-	char *pkalg, *userstyle, *pubkey, *fp = NULL;

-	u_char *pkblob, *sig;

+	char *pkalg = NULL, *userstyle = NULL, *pubkey = NULL, *fp = NULL;

+	u_char *pkblob = NULL, *sig = NULL;

 	u_int alen, blen, slen;

 	int have_sig, pktype;

 	int authenticated = 0;

-	if (!authctxt->valid) {

-		debug2("%s: disabled because of invalid user", __func__);

-		return 0;

-	}

 	have_sig = packet_get_char();

 	if (datafellows & SSH_BUG_PKAUTH) {

 		debug2("%s: SSH_BUG_PKAUTH", __func__);

@@ -167,6 +163,12 @@ userauth_pubkey(struct ssh *ssh)

 		} else {

 			buffer_put_string(&b, session_id2, session_id2_len);

 		}

+		if (!authctxt->valid || authctxt->user == NULL) {

+			buffer_free(&b);

+			debug2("%s: disabled because of invalid user",

+			    __func__);

+			goto done;

+		}

 		/* reconstruct packet */

 		buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);

 		xasprintf(&userstyle, "%s%s%s%s%s", authctxt->user,

@@ -183,7 +184,6 @@ userauth_pubkey(struct ssh *ssh)

 #endif

 		pubkey = sshkey_format_oneline(key, options.fingerprint_hash);

 		auth_info(authctxt, "%s", pubkey);

-

 		/* test for correct signature */

 		authenticated = 0;

 		if (PRIVSEP(user_key_allowed(authctxt->pw, key, 1)) &&

@@ -194,7 +194,6 @@ userauth_pubkey(struct ssh *ssh)

 			free(pubkey);

 		}

 		buffer_free(&b);

-		free(sig);

 	} else {

 		debug("%s: test whether pkalg/pkblob are acceptable for %s %s",

 		    __func__, sshkey_type(key), fp);

@@ -205,6 +204,11 @@ userauth_pubkey(struct ssh *ssh)

 		    __func__, sshkey_type(key), fp);

 		packet_check_eom();

+		if (!authctxt->valid || authctxt->user == NULL) {

+			debug2("%s: disabled because of invalid user",

+			    __func__);

+			goto done;

+		}

 		/* XXX fake reply and always send PK_OK ? */

 		/*

 		 * XXX this allows testing whether a user is allowed

@@ -238,6 +242,7 @@ userauth_pubkey(struct ssh *ssh)

 	free(pkalg);

 	free(pkblob);

 	free(fp);

+	free(sig);

 	return authenticated;

 }