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Don't prefer ECDHE-ECDSA ciphers when the client appears to be Safari…

… on OS X.

OS X 10.8..10.8.3 has broken support for ECDHE-ECDSA ciphers.
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1 parent c3eb337 commit dece3209f299ebcd82414868ee39b2c6feb3be0a @robstradling robstradling committed Sep 5, 2013
Showing with 114 additions and 6 deletions.
  1. +3 −2 doc/ssl/SSL_CTX_set_options.pod
  2. +13 −3 ssl/s3_lib.c
  3. +1 −1 ssl/ssl.h
  4. +8 −0 ssl/ssl3.h
  5. +89 −0 ssl/t1_lib.c
@@ -88,9 +88,10 @@ As of OpenSSL 0.9.8q and 1.0.0c, this option has no effect.
...
-=item SSL_OP_MSIE_SSLV2_RSA_PADDING
+=item SSL_OP_SAFARI_ECDHE_ECDSA_BUG
-As of OpenSSL 0.9.7h and 0.9.8a, this option has no effect.
+Don't prefer ECDHE-ECDSA ciphers when the client appears to be Safari on OS X.
+OS X 10.8..10.8.3 has broken support for ECDHE-ECDSA ciphers.
=item SSL_OP_SSLEAY_080_CLIENT_DH_BUG
View
@@ -3089,7 +3089,10 @@ void ssl3_clear(SSL *s)
s->s3->tlsext_custom_types = NULL;
}
s->s3->tlsext_custom_types_count = 0;
-#endif
+#ifndef OPENSSL_NO_EC
+ s->s3->is_probably_safari = 0;
+#endif /* OPENSSL_NO_EC */
+#endif /* OPENSSL_NO_TLSEXT */
rp = s->s3->rbuf.buf;
wp = s->s3->wbuf.buf;
@@ -4170,8 +4173,15 @@ SSL_CIPHER *ssl3_choose_cipher(SSL *s, STACK_OF(SSL_CIPHER) *clnt,
ii=sk_SSL_CIPHER_find(allow,c);
if (ii >= 0)
{
- ret=sk_SSL_CIPHER_value(allow,ii);
- break;
+ if ((alg_k & SSL_kEECDH) && (alg_a & SSL_aECDSA) && s->s3->is_probably_safari)
+ {
+ if (!ret) ret=sk_SSL_CIPHER_value(allow,ii);
+ }
+ else
+ {
+ ret=sk_SSL_CIPHER_value(allow,ii);
+ break;
+ }
}
}
return(ret);
View
@@ -615,7 +615,7 @@ struct ssl_session_st
#define SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG 0x00000008L
#define SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG 0x00000010L
#define SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER 0x00000020L
-#define SSL_OP_MSIE_SSLV2_RSA_PADDING 0x00000040L /* no effect since 0.9.7h and 0.9.8b */
+#define SSL_OP_SAFARI_ECDHE_ECDSA_BUG 0x00000040L
#define SSL_OP_SSLEAY_080_CLIENT_DH_BUG 0x00000080L
#define SSL_OP_TLS_D5_BUG 0x00000100L
#define SSL_OP_TLS_BLOCK_PADDING_BUG 0x00000200L
View
@@ -596,6 +596,14 @@ typedef struct ssl3_state_st
* processed. */
unsigned char *alpn_selected;
unsigned alpn_selected_len;
+
+#ifndef OPENSSL_NO_EC
+ /* This is set to true if we believe that this is a version of Safari
+ * running on OS X 10.6 or newer. We wish to know this because Safari
+ * on 10.8 .. 10.8.3 has broken ECDHE-ECDSA support. */
+ char is_probably_safari;
+#endif /* OPENSSL_NO_EC */
+
#endif /* OPENSSL_NO_TLSEXT */
} SSL3_STATE;
View
@@ -1899,6 +1899,89 @@ static int tls1_alpn_handle_client_hello(SSL *s, const unsigned char *data,
return -1;
}
+#ifndef OPENSSL_NO_EC
+/* ssl_check_for_safari attempts to fingerprint Safari using OS X
+ * SecureTransport using the TLS extension block in |d|, of length |n|.
+ * Safari, since 10.6, sends exactly these extensions, in this order:
+ * SNI,
+ * elliptic_curves
+ * ec_point_formats
+ *
+ * We wish to fingerprint Safari because they broke ECDHE-ECDSA support in 10.8,
+ * but they advertise support. So enabling ECDHE-ECDSA ciphers breaks them.
+ * Sadly we cannot differentiate 10.6, 10.7 and 10.8.4 (which work), from
+ * 10.8..10.8.3 (which don't work).
+ */
+static void ssl_check_for_safari(SSL *s, const unsigned char *data, const unsigned char *d, int n) {
+ unsigned short type, size;
+ static const unsigned char kSafariExtensionsBlock[] = {
+ 0x00, 0x0a, /* elliptic_curves extension */
+ 0x00, 0x08, /* 8 bytes */
+ 0x00, 0x06, /* 6 bytes of curve ids */
+ 0x00, 0x17, /* P-256 */
+ 0x00, 0x18, /* P-384 */
+ 0x00, 0x19, /* P-521 */
+
+ 0x00, 0x0b, /* ec_point_formats */
+ 0x00, 0x02, /* 2 bytes */
+ 0x01, /* 1 point format */
+ 0x00, /* uncompressed */
+ };
+
+ /* The following is only present in TLS 1.2 */
+ static const unsigned char kSafariTLS12ExtensionsBlock[] = {
+ 0x00, 0x0d, /* signature_algorithms */
+ 0x00, 0x0c, /* 12 bytes */
+ 0x00, 0x0a, /* 10 bytes */
+ 0x05, 0x01, /* SHA-384/RSA */
+ 0x04, 0x01, /* SHA-256/RSA */
+ 0x02, 0x01, /* SHA-1/RSA */
+ 0x04, 0x03, /* SHA-256/ECDSA */
+ 0x02, 0x03, /* SHA-1/ECDSA */
+ };
+
+ if (data >= (d+n-2))
+ return;
+ data += 2;
+
+ if (data > (d+n-4))
+ return;
+ n2s(data,type);
+ n2s(data,size);
+
+ if (type != TLSEXT_TYPE_server_name)
+ return;
+
+ if (data+size > d+n)
+ return;
+ data += size;
+
+ if (TLS1_get_version(s) >= TLS1_2_VERSION)
+ {
+ const size_t len1 = sizeof(kSafariExtensionsBlock);
+ const size_t len2 = sizeof(kSafariTLS12ExtensionsBlock);
+
+ if (data + len1 + len2 != d+n)
+ return;
+ if (memcmp(data, kSafariExtensionsBlock, len1) != 0)
+ return;
+ if (memcmp(data + len1, kSafariTLS12ExtensionsBlock, len2) != 0)
+ return;
+ }
+ else
+ {
+ const size_t len = sizeof(kSafariExtensionsBlock);
+
+ if (data + len != d+n)
+ return;
+ if (memcmp(data, kSafariExtensionsBlock, len) != 0)
+ return;
+ }
+
+ s->s3->is_probably_safari = 1;
+}
+#endif /* OPENSSL_NO_EC */
+
static int ssl_scan_clienthello_tlsext(SSL *s, unsigned char **p, unsigned char *d, int n, int *al)
{
unsigned short type;
@@ -1932,6 +2015,12 @@ static int ssl_scan_clienthello_tlsext(SSL *s, unsigned char **p, unsigned char
s->tlsext_heartbeat &= ~(SSL_TLSEXT_HB_ENABLED |
SSL_TLSEXT_HB_DONT_SEND_REQUESTS);
#endif
+
+#ifndef OPENSSL_NO_EC
+ if (s->options & SSL_OP_SAFARI_ECDHE_ECDSA_BUG)
+ ssl_check_for_safari(s, data, d, n);
+#endif /* OPENSSL_NO_EC */
+
/* Clear any signature algorithms extension received */
if (s->cert->peer_sigalgs)
{

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