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@

1 files changed, 25 insertions, 27 deletions

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 */
@@ -3021,14 +3027,6 @@ SSL_set_msg_callback(SSL *ssl, void (*cb)(int write_p, int version,
 }
 
 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)
 {
 	s->internal->debug = debug;