From: jsing <jsing@openbsd.org>
Date: Wed, 5 Sep 2018 16:48:11 +0000 (+0000)
Subject: Correctly clear the current cipher state, when changing cipher state.
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=f1abf68627e51bc3621a614ccccf1e70315337bb;p=openbsd

Correctly clear the current cipher state, when changing cipher state.

When a renegotiation results in a change of cipher suite, the renegotation
would fail if it switched from AEAD to non-AEAD or vice versa. This is due
to the fact that the previous EVP_AEAD or EVP_CIPHER state remained,
resulting in incorrect logic that caused MAC failures.

Rename ssl_clear_cipher_ctx() to ssl_clear_cipher_state() and split it
into separate read/write components, then call these functions from the
appropriate places when a ChangeCipherSpec message is being processed.
Also, remove the separate ssl_clear_hash_ctx() calls and fold these into
the ssl_clear_cipher_{read,write}_state() functions.

Issue reported by Bernard Spil, who also tested this diff.

ok tb@
---

diff --git a/lib/libssl/ssl_lib.c b/lib/libssl/ssl_lib.c
index 938139e18ed..44d11d4b164 100644
--- a/lib/libssl/ssl_lib.c
+++ b/lib/libssl/ssl_lib.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssl_lib.c,v 1.187 2018/08/30 16:56:16 jsing Exp $ */
+/* $OpenBSD: ssl_lib.c,v 1.188 2018/09/05 16:48:11 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -191,9 +191,7 @@ SSL_clear(SSL *s)
 	BUF_MEM_free(s->internal->init_buf);
 	s->internal->init_buf = NULL;
 
-	ssl_clear_cipher_ctx(s);
-	ssl_clear_hash_ctx(&s->read_hash);
-	ssl_clear_hash_ctx(&s->internal->write_hash);
+	ssl_clear_cipher_state(s);
 
 	s->internal->first_packet = 0;
 
@@ -534,9 +532,7 @@ SSL_free(SSL *s)
 		SSL_SESSION_free(s->session);
 	}
 
-	ssl_clear_cipher_ctx(s);
-	ssl_clear_hash_ctx(&s->read_hash);
-	ssl_clear_hash_ctx(&s->internal->write_hash);
+	ssl_clear_cipher_state(s);
 
 	ssl_cert_free(s->cert);
 
@@ -2431,10 +2427,7 @@ SSL_set_accept_state(SSL *s)
 	s->internal->shutdown = 0;
 	S3I(s)->hs.state = SSL_ST_ACCEPT|SSL_ST_BEFORE;
 	s->internal->handshake_func = s->method->internal->ssl_accept;
-	/* clear the current cipher */
-	ssl_clear_cipher_ctx(s);
-	ssl_clear_hash_ctx(&s->read_hash);
-	ssl_clear_hash_ctx(&s->internal->write_hash);
+	ssl_clear_cipher_state(s);
 }
 
 void
@@ -2444,10 +2437,7 @@ SSL_set_connect_state(SSL *s)
 	s->internal->shutdown = 0;
 	S3I(s)->hs.state = SSL_ST_CONNECT|SSL_ST_BEFORE;
 	s->internal->handshake_func = s->method->internal->ssl_connect;
-	/* clear the current cipher */
-	ssl_clear_cipher_ctx(s);
-	ssl_clear_hash_ctx(&s->read_hash);
-	ssl_clear_hash_ctx(&s->internal->write_hash);
+	ssl_clear_cipher_state(s);
 }
 
 int
@@ -2623,24 +2613,40 @@ SSL_dup(SSL *s)
 }
 
 void
-ssl_clear_cipher_ctx(SSL *s)
+ssl_clear_cipher_state(SSL *s)
+{
+	ssl_clear_cipher_read_state(s);
+	ssl_clear_cipher_write_state(s);
+}
+
+void
+ssl_clear_cipher_read_state(SSL *s)
 {
 	EVP_CIPHER_CTX_free(s->enc_read_ctx);
 	s->enc_read_ctx = NULL;
-	EVP_CIPHER_CTX_free(s->internal->enc_write_ctx);
-	s->internal->enc_write_ctx = NULL;
+	EVP_MD_CTX_destroy(s->read_hash);
+	s->read_hash = NULL;
 
 	if (s->internal->aead_read_ctx != NULL) {
 		EVP_AEAD_CTX_cleanup(&s->internal->aead_read_ctx->ctx);
 		free(s->internal->aead_read_ctx);
 		s->internal->aead_read_ctx = NULL;
 	}
+}
+
+void
+ssl_clear_cipher_write_state(SSL *s)
+{
+	EVP_CIPHER_CTX_free(s->internal->enc_write_ctx);
+	s->internal->enc_write_ctx = NULL;
+	EVP_MD_CTX_destroy(s->internal->write_hash);
+	s->internal->write_hash = NULL;
+
 	if (s->internal->aead_write_ctx != NULL) {
 		EVP_AEAD_CTX_cleanup(&s->internal->aead_write_ctx->ctx);
 		free(s->internal->aead_write_ctx);
 		s->internal->aead_write_ctx = NULL;
 	}
-
 }
 
 /* Fix this function so that it takes an optional type parameter */
@@ -3020,14 +3026,6 @@ SSL_set_msg_callback(SSL *ssl, void (*cb)(int write_p, int version,
 	SSL_callback_ctrl(ssl, SSL_CTRL_SET_MSG_CALLBACK, (void (*)(void))cb);
 }
 
-void
-ssl_clear_hash_ctx(EVP_MD_CTX **hash)
-{
-	if (*hash)
-		EVP_MD_CTX_destroy(*hash);
-	*hash = NULL;
-}
-
 void
 SSL_set_debug(SSL *s, int debug)
 {
diff --git a/lib/libssl/ssl_locl.h b/lib/libssl/ssl_locl.h
index b6d71492fd0..a4e831577d0 100644
--- a/lib/libssl/ssl_locl.h
+++ b/lib/libssl/ssl_locl.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssl_locl.h,v 1.212 2018/08/30 16:56:16 jsing Exp $ */
+/* $OpenBSD: ssl_locl.h,v 1.213 2018/09/05 16:48:11 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -1039,7 +1039,9 @@ extern SSL3_ENC_METHOD TLSv1_enc_data;
 extern SSL3_ENC_METHOD TLSv1_1_enc_data;
 extern SSL3_ENC_METHOD TLSv1_2_enc_data;
 
-void ssl_clear_cipher_ctx(SSL *s);
+void ssl_clear_cipher_state(SSL *s);
+void ssl_clear_cipher_read_state(SSL *s);
+void ssl_clear_cipher_write_state(SSL *s);
 int ssl_clear_bad_session(SSL *s);
 CERT *ssl_cert_new(void);
 CERT *ssl_cert_dup(CERT *cert);
@@ -1279,7 +1281,6 @@ int tls12_get_sigid(const EVP_PKEY *pk);
 int tls12_get_hashandsig(CBB *cbb, const EVP_PKEY *pk, const EVP_MD *md);
 const EVP_MD *tls12_get_hash(unsigned char hash_alg);
 
-void ssl_clear_hash_ctx(EVP_MD_CTX **hash);
 long ssl_get_algorithm2(SSL *s);
 int tls1_process_sigalgs(SSL *s, CBS *cbs);
 void tls12_get_req_sig_algs(SSL *s, unsigned char **sigalgs,
diff --git a/lib/libssl/t1_enc.c b/lib/libssl/t1_enc.c
index 24fc8ede683..39f542215b4 100644
--- a/lib/libssl/t1_enc.c
+++ b/lib/libssl/t1_enc.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: t1_enc.c,v 1.110 2018/08/31 18:31:34 jsing Exp $ */
+/* $OpenBSD: t1_enc.c,v 1.111 2018/09/05 16:48:11 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -397,10 +397,13 @@ tls1_change_cipher_state_aead(SSL *s, char is_read, const unsigned char *key,
 	SSL_AEAD_CTX *aead_ctx;
 
 	if (is_read) {
+		ssl_clear_cipher_read_state(s);
 		if (!tls1_aead_ctx_init(&s->internal->aead_read_ctx))
 			return 0;
 		aead_ctx = s->internal->aead_read_ctx;
 	} else {
+		/* XXX - Need to correctly handle DTLS. */
+		ssl_clear_cipher_write_state(s);
 		if (!tls1_aead_ctx_init(&s->internal->aead_write_ctx))
 			return 0;
 		aead_ctx = s->internal->aead_write_ctx;
@@ -468,10 +471,7 @@ tls1_change_cipher_state_cipher(SSL *s, char is_read,
 		else
 			s->internal->mac_flags &= ~SSL_MAC_FLAG_READ_MAC_STREAM;
 
-		EVP_CIPHER_CTX_free(s->enc_read_ctx);
-		s->enc_read_ctx = NULL;
-		EVP_MD_CTX_destroy(s->read_hash);
-		s->read_hash = NULL;
+		ssl_clear_cipher_read_state(s);
 
 		if ((cipher_ctx = EVP_CIPHER_CTX_new()) == NULL)
 			goto err;
@@ -492,12 +492,9 @@ tls1_change_cipher_state_cipher(SSL *s, char is_read,
 		 * contexts that are used for DTLS - these are instead freed
 		 * by DTLS when its frees a ChangeCipherSpec fragment.
 		 */
-		if (!SSL_IS_DTLS(s)) {
-			EVP_CIPHER_CTX_free(s->internal->enc_write_ctx);
-			s->internal->enc_write_ctx = NULL;
-			EVP_MD_CTX_destroy(s->internal->write_hash);
-			s->internal->write_hash = NULL;
-		}
+		if (!SSL_IS_DTLS(s))
+			ssl_clear_cipher_write_state(s);
+
 		if ((cipher_ctx = EVP_CIPHER_CTX_new()) == NULL)
 			goto err;
 		s->internal->enc_write_ctx = cipher_ctx;