From 06da6e49777285f50aeb1b920d950a9bd27fef52 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Lutz=20J=C3=A4nicke?= <jaenicke@openssl.org>
Date: Fri, 3 Aug 2001 08:45:13 +0000
Subject: [PATCH] Don't disable rollback attack detection as a recommended bug
workaround.
---
CHANGES | 8 ++++++++
doc/ssl/SSL_CTX_set_options.pod | 28 +++++++++++++++-------------
ssl/ssl.h | 6 +++++-
3 files changed, 28 insertions(+), 14 deletions(-)
diff --git a/CHANGES b/CHANGES
index 0c96da129c..7ec91e58d2 100644
--- a/CHANGES
+++ b/CHANGES
@@ -12,6 +12,14 @@
*) applies to 0.9.6a/0.9.6b/0.9.6c and 0.9.7
+) applies to 0.9.7 only
+ +) Move SSL_OP_TLS_ROLLBACK_BUG out of the SSL_OP_ALL list of recommended
+ bug workarounds. Rollback attack detection is a security feature.
+ The problem will only arise on OpenSSL servers, when TLSv1 is not
+ available (sslv3_server_method() or SSL_OP_NO_TLSv1).
+ Software authors not wanting to support TLSv1 will have special reasons
+ for their choice and can explicitly enable this option.
+ [Bodo Moeller, Lutz Jaenicke]
+
+) Rationalise EVP so it can be extended: don't include a union of
cipher/digest structures, add init/cleanup functions. This also reduces
the number of header dependencies.
diff --git a/doc/ssl/SSL_CTX_set_options.pod b/doc/ssl/SSL_CTX_set_options.pod
index 88304ef7ed..4e7fbaedc8 100644
--- a/doc/ssl/SSL_CTX_set_options.pod
+++ b/doc/ssl/SSL_CTX_set_options.pod
@@ -100,18 +100,6 @@ doing a re-connect, always takes the first cipher in the cipher list.
...
-=item SSL_OP_TLS_ROLLBACK_BUG
-
-Disable version rollback attack detection.
-
-During the client key exchange, the client must send the same information
-about acceptable SSL/TLS protocol levels as during the first hello. Some
-clients violate this rule by adapting to the server's answer. (Example:
-the client sends a SSLv2 hello and accepts up to SSLv3.1=TLSv1, the server
-only understands up to SSLv3. In this case the client must still use the
-same SSLv3.1=TLSv1 announcement. Some clients step down to SSLv3 with respect
-to the server's answer and violate the version rollback protection.)
-
=item SSL_OP_ALL
All of the above bug workarounds.
@@ -125,6 +113,18 @@ The following B<modifying> options are available:
=over 4
+=item SSL_OP_TLS_ROLLBACK_BUG
+
+Disable version rollback attack detection.
+
+During the client key exchange, the client must send the same information
+about acceptable SSL/TLS protocol levels as during the first hello. Some
+clients violate this rule by adapting to the server's answer. (Example:
+the client sends a SSLv2 hello and accepts up to SSLv3.1=TLSv1, the server
+only understands up to SSLv3. In this case the client must still use the
+same SSLv3.1=TLSv1 announcement. Some clients step down to SSLv3 with respect
+to the server's answer and violate the version rollback protection.)
+
=item SSL_OP_SINGLE_DH_USE
Always create a new key when using temporary/ephemeral DH parameters
@@ -207,6 +207,8 @@ L<dhparam(1)|dhparam(1)>
SSL_OP_CIPHER_SERVER_PREFERENCE has been added in OpenSSL 0.9.7.
-SSL_OP_TLS_ROLLBACK_BUG has been added in OpenSSL 0.9.6.
+SSL_OP_TLS_ROLLBACK_BUG has been added in OpenSSL 0.9.6 and was automatically
+enabled with SSL_OP_ALL. As of 0.9.7 it is no longer included in SSL_OP_ALL
+and must be explicitely set.
=cut
diff --git a/ssl/ssl.h b/ssl/ssl.h
index dc80ae9e43..8f5d0a4d47 100644
--- a/ssl/ssl.h
+++ b/ssl/ssl.h
@@ -332,7 +332,6 @@ typedef struct ssl_session_st
#define SSL_OP_SSLEAY_080_CLIENT_DH_BUG 0x00000080L
#define SSL_OP_TLS_D5_BUG 0x00000100L
#define SSL_OP_TLS_BLOCK_PADDING_BUG 0x00000200L
-#define SSL_OP_TLS_ROLLBACK_BUG 0x00000400L
/* If set, always create a new key when using tmp_dh parameters */
#define SSL_OP_SINGLE_DH_USE 0x00100000L
@@ -341,6 +340,11 @@ typedef struct ssl_session_st
/* Set on servers to choose the cipher according to the server's
* preferences */
#define SSL_OP_CIPHER_SERVER_PREFERENCE 0x00400000L
+/* If set, a server will allow a client to issue a SSLv3.0 version number
+ * as latest version supported in the premaster secret, even when TLSv1.0
+ * (version 3.1) was announced in the client hello. Normally this is
+ * forbidden to prevent version rollback attacks. */
+#define SSL_OP_TLS_ROLLBACK_BUG 0x00800000L
/* The next flag deliberately changes the ciphertest, this is a check
* for the PKCS#1 attack */
--
2.40.0