From c21506ba024adb6d5655a92d61c1d3824e5dedcf Mon Sep 17 00:00:00 2001 From: =?utf8?q?Bodo=20M=C3=B6ller?= Date: Fri, 14 Jun 2002 12:21:11 +0000 Subject: [PATCH] New option SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS for disabling CBC vulnerability workaround (included in SSL_OP_ALL). PR: #90 --- CHANGES | 17 +++++++++++++++++ doc/ssl/SSL_CTX_set_options.pod | 17 +++++++++++++++-- ssl/s3_enc.c | 15 ++++++++++----- ssl/ssl.h | 25 +++++++++++++++++++------ ssl/t1_enc.c | 15 ++++++++++----- 5 files changed, 71 insertions(+), 18 deletions(-) diff --git a/CHANGES b/CHANGES index e1c8a75028..869ee64e74 100644 --- a/CHANGES +++ b/CHANGES @@ -421,6 +421,10 @@ By default, clients may request session resumption even during renegotiation (if session ID contexts permit); with this option, session resumption is possible only in the first handshake. + + SSL_OP_ALL is now 0x00000FFFL instead of 0x000FFFFFL. This makes + more bits available for options that should not be part of + SSL_OP_ALL (such as SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION). [Bodo Moeller] *) Add some demos for certificate and certificate request creation. @@ -1708,6 +1712,19 @@ des-cbc 3624.96k 5258.21k 5530.91k 5624.30k 5628.26k *) Fix EVP_dsa_sha macro. [Nils Larsch] + *) New option + SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS + for disabling the SSL 3.0/TLS 1.0 CBC vulnerability countermeasure + that was added in OpenSSL 0.9.6d. + + As the countermeasure turned out to be incompatible with some + broken SSL implementations, the new option is part of SSL_OP_ALL. + SSL_OP_ALL is usually employed when compatibility with weird SSL + implementations is desired (e.g. '-bugs' option to 's_client' and + 's_server'), so the new option is automatically set in many + applications. + [Bodo Moeller] + Changes between 0.9.6c and 0.9.6d [9 May 2002] *) Fix crypto/asn1/a_sign.c so that 'parameters' is omitted (not diff --git a/doc/ssl/SSL_CTX_set_options.pod b/doc/ssl/SSL_CTX_set_options.pod index c10055c6e7..3b918178fd 100644 --- a/doc/ssl/SSL_CTX_set_options.pod +++ b/doc/ssl/SSL_CTX_set_options.pod @@ -100,14 +100,22 @@ doing a re-connect, always takes the first cipher in the cipher list. ... +=item SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS + +Disables a countermeasure against a SSL 3.0/TLS 1.0 protocol +vulnerability affecting CBC ciphers, which cannot be handled by some +broken SSL implementations. This option has no effect for connections +using other ciphers. + =item SSL_OP_ALL All of the above bug workarounds. =back -It is safe and recommended to use B to enable the bug workaround -options. +It is usually safe to use B to enable the bug workaround +options if compatibility with somewhat broken implementations is +desired. The following B options are available: @@ -219,4 +227,9 @@ B has been added in OpenSSL 0.9.6 and was automatically enabled with B. As of 0.9.7, it is no longer included in B and must be explicitly set. +B has been added in OpenSSL 0.9.6e. +Versions up to OpenSSL 0.9.6c do not include the countermeasure that +can be disabled with this option (in OpenSSL 0.9.6d, it was always +enabled). + =cut diff --git a/ssl/s3_enc.c b/ssl/s3_enc.c index 6dfef5caaf..72ac8b6913 100644 --- a/ssl/s3_enc.c +++ b/ssl/s3_enc.c @@ -378,13 +378,18 @@ int ssl3_setup_key_block(SSL *s) ret = ssl3_generate_key_block(s,p,num); - /* enable vulnerability countermeasure for CBC ciphers with - * known-IV problem (http://www.openssl.org/~bodo/tls-cbc.txt) */ - s->s3->need_empty_fragments = 1; + if (!(s->options & SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS)) + { + /* enable vulnerability countermeasure for CBC ciphers with + * known-IV problem (http://www.openssl.org/~bodo/tls-cbc.txt) + */ + s->s3->need_empty_fragments = 1; + #ifndef OPENSSL_NO_RC4 - if ((s->session->cipher != NULL) && ((s->session->cipher->algorithms & SSL_ENC_MASK) == SSL_RC4)) - s->s3->need_empty_fragments = 0; + if ((s->session->cipher != NULL) && ((s->session->cipher->algorithms & SSL_ENC_MASK) == SSL_RC4)) + s->s3->need_empty_fragments = 0; #endif + } return ret; diff --git a/ssl/ssl.h b/ssl/ssl.h index 833f761690..474e5a76ef 100644 --- a/ssl/ssl.h +++ b/ssl/ssl.h @@ -429,6 +429,7 @@ typedef struct ssl_session_st struct ssl_session_st *prev,*next; } SSL_SESSION; + #define SSL_OP_MICROSOFT_SESS_ID_BUG 0x00000001L #define SSL_OP_NETSCAPE_CHALLENGE_BUG 0x00000002L #define SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG 0x00000008L @@ -439,6 +440,19 @@ typedef struct ssl_session_st #define SSL_OP_TLS_D5_BUG 0x00000100L #define SSL_OP_TLS_BLOCK_PADDING_BUG 0x00000200L +/* Disable SSL 3.0/TLS 1.0 CBC vulnerability workaround that was added + * in OpenSSL 0.9.6d. Usually (depending on the application protocol) + * the workaround is not needed. Unfortunately some broken SSL/TLS + * implementations cannot handle it at all, which is why we include + * it in SSL_OP_ALL. */ +#define SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS 0x00000800L /* added in 0.9.6e */ + +/* SSL_OP_ALL: various bug workarounds that should be rather harmless. + * This used to be 0x000FFFFFL before 0.9.7. */ +#define SSL_OP_ALL 0x00000FFFL + +/* As server, disallow session resumption on renegotiation */ +#define SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION 0x00010000L /* If set, always create a new key when using tmp_dh parameters */ #define SSL_OP_SINGLE_DH_USE 0x00100000L /* Set to always use the tmp_rsa key when doing RSA operations, @@ -452,8 +466,10 @@ typedef struct ssl_session_st * (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 -/* As server, disallow session resumption on renegotiation */ -#define SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION 0x01000000L + +#define SSL_OP_NO_SSLv2 0x01000000L +#define SSL_OP_NO_SSLv3 0x02000000L +#define SSL_OP_NO_TLSv1 0x04000000L /* The next flag deliberately changes the ciphertest, this is a check * for the PKCS#1 attack */ @@ -461,11 +477,7 @@ typedef struct ssl_session_st #define SSL_OP_PKCS1_CHECK_2 0x10000000L #define SSL_OP_NETSCAPE_CA_DN_BUG 0x20000000L #define SSL_OP_NETSCAPE_DEMO_CIPHER_CHANGE_BUG 0x40000000L -#define SSL_OP_ALL 0x000FFFFFL -#define SSL_OP_NO_SSLv2 0x01000000L -#define SSL_OP_NO_SSLv3 0x02000000L -#define SSL_OP_NO_TLSv1 0x04000000L /* Allow SSL_write(..., n) to return r with 0 < r < n (i.e. report success * when just a single record has been written): */ @@ -479,6 +491,7 @@ typedef struct ssl_session_st * is blocking: */ #define SSL_MODE_AUTO_RETRY 0x00000004L + /* Note: SSL[_CTX]_set_{options,mode} use |= op on the previous value, * they cannot be used to clear bits. */ diff --git a/ssl/t1_enc.c b/ssl/t1_enc.c index b80525f3ba..ecd2d6cbb5 100644 --- a/ssl/t1_enc.c +++ b/ssl/t1_enc.c @@ -483,13 +483,18 @@ printf("\nkey block\n"); { int z; for (z=0; zs3->need_empty_fragments = 1; + if (!(s->options & SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS)) + { + /* enable vulnerability countermeasure for CBC ciphers with + * known-IV problem (http://www.openssl.org/~bodo/tls-cbc.txt) + */ + s->s3->need_empty_fragments = 1; + #ifndef NO_RC4 - if ((s->session->cipher != NULL) && ((s->session->cipher->algorithms & SSL_ENC_MASK) == SSL_RC4)) - s->s3->need_empty_fragments = 0; + if ((s->session->cipher != NULL) && ((s->session->cipher->algorithms & SSL_ENC_MASK) == SSL_RC4)) + s->s3->need_empty_fragments = 0; #endif + } return(1); err: -- 2.25.1