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Option to disable padding extension.

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Add TLS padding extension to SSL_OP_ALL so it is used with other
"bugs" options and can be turned off.

This replaces SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG which is an ancient
option referring to SSLv2 and SSLREF.

PR#3336
This commit is contained in:
Dr. Stephen Henson 2014-06-01 16:36:24 +01:00
parent 49270d0431
commit aaed77c55e
3 changed files with 29 additions and 22 deletions
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6
doc/ssl/SSL_CTX_set_options.pod
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@ -112,6 +112,12 @@ vulnerability affecting CBC ciphers, which cannot be handled by some
broken SSL implementations. This option has no effect for connections broken SSL implementations. This option has no effect for connections
using other ciphers. using other ciphers.
=item SSL_OP_TLSEXT_PADDING
Adds a padding extension to ensure the ClientHello size is never between
256 and 511 bytes in length. This is needed as a workaround for some
implementations.
=item SSL_OP_ALL =item SSL_OP_ALL
All of the above bug workarounds. All of the above bug workarounds.

4
ssl/ssl.h
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@ -553,7 +553,7 @@ struct ssl_session_st
/* Allow initial connection to servers that don't support RI */ /* Allow initial connection to servers that don't support RI */
#define SSL_OP_LEGACY_SERVER_CONNECT 0x00000004L #define SSL_OP_LEGACY_SERVER_CONNECT 0x00000004L
#define SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG 0x00000008L #define SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG 0x00000008L
#define SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG 0x00000010L #define SSL_OP_TLSEXT_PADDING 0x00000010L
#define SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER 0x00000020L #define SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER 0x00000020L
#define SSL_OP_SAFARI_ECDHE_ECDSA_BUG 0x00000040L #define SSL_OP_SAFARI_ECDHE_ECDSA_BUG 0x00000040L
#define SSL_OP_SSLEAY_080_CLIENT_DH_BUG 0x00000080L #define SSL_OP_SSLEAY_080_CLIENT_DH_BUG 0x00000080L
@ -562,6 +562,8 @@ struct ssl_session_st
/* Hasn't done anything since OpenSSL 0.9.7h, retained for compatibility */ /* Hasn't done anything since OpenSSL 0.9.7h, retained for compatibility */
#define SSL_OP_MSIE_SSLV2_RSA_PADDING 0x0 #define SSL_OP_MSIE_SSLV2_RSA_PADDING 0x0
/* Refers to ancient SSLREF and SSLv2, retained for compatibility */
#define SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG 0x0
/* Disable SSL 3.0/TLS 1.0 CBC vulnerability workaround that was added /* Disable SSL 3.0/TLS 1.0 CBC vulnerability workaround that was added
* in OpenSSL 0.9.6d. Usually (depending on the application protocol) * in OpenSSL 0.9.6d. Usually (depending on the application protocol)

41
ssl/t1_lib.c
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@ -661,36 +661,35 @@ unsigned char *ssl_add_clienthello_tlsext(SSL *s, unsigned char *p, unsigned cha
ret += el; ret += el;
} }
#endif #endif
#ifdef TLSEXT_TYPE_padding
/* Add padding to workaround bugs in F5 terminators. /* Add padding to workaround bugs in F5 terminators.
* See https://tools.ietf.org/html/draft-agl-tls-padding-03 * See https://tools.ietf.org/html/draft-agl-tls-padding-03
* *
* NB: because this code works out the length of all existing * NB: because this code works out the length of all existing
* extensions it MUST always appear last. * extensions it MUST always appear last.
*/ */
{ if (s->options & SSL_OP_TLSEXT_PADDING)
int hlen = ret - (unsigned char *)s->init_buf->data;
/* The code in s23_clnt.c to build ClientHello messages includes the
* 5-byte record header in the buffer, while the code in s3_clnt.c does
* not. */
if (s->state == SSL23_ST_CW_CLNT_HELLO_A)
hlen -= 5;
if (hlen > 0xff && hlen < 0x200)
{ {
hlen = 0x200 - hlen; int hlen = ret - (unsigned char *)s->init_buf->data;
if (hlen >= 4) /* The code in s23_clnt.c to build ClientHello messages
hlen -= 4; * includes the 5-byte record header in the buffer, while
else * the code in s3_clnt.c does not.
hlen = 0; */
if (s->state == SSL23_ST_CW_CLNT_HELLO_A)
hlen -= 5;
if (hlen > 0xff && hlen < 0x200)
{
hlen = 0x200 - hlen;
if (hlen >= 4)
hlen -= 4;
else
hlen = 0;
s2n(TLSEXT_TYPE_padding, ret); s2n(TLSEXT_TYPE_padding, ret);
s2n(hlen, ret); s2n(hlen, ret);
memset(ret, 0, hlen); memset(ret, 0, hlen);
ret += hlen; ret += hlen;
}
} }
}
#endif
if ((extdatalen = ret-p-2)== 0) if ((extdatalen = ret-p-2)== 0)
return p; return p;