Pull out (and largely rewrite) the code that determines the enabled

protocol version range.

This also fixes a bug whereby if all protocols were disabled, the client
would still use TLSv1.2 in the client hello, only to have if fail with
unsupported version when it received and processed the server hello.

ok doug@

3 files changed, 54 insertions, 40 deletions

diff --git a/src/lib/libssl/s23_clnt.c b/src/lib/libssl/s23_clnt.c
index 8674cdf627..2511a94b28 100644
--- a/src/lib/libssl/s23_clnt.c
+++ b/src/lib/libssl/s23_clnt.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: s23_clnt.c,v 1.47 2016/12/04 14:32:30 jsing Exp $ */
+/* $OpenBSD: s23_clnt.c,v 1.48 2016/12/30 16:57:01 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -231,43 +231,15 @@ ssl23_client_hello(SSL *s)
         unsigned char *buf;
         unsigned char *p, *d;
         unsigned long l;
-        int version = 0, version_major, version_minor;
-        int ret;
-        unsigned long mask, options = s->options;
+        uint16_t version;
         size_t outlen;
-
-        /*
-         * SSL_OP_NO_X disables all protocols above X *if* there are
-         * some protocols below X enabled. This is required in order
-         * to maintain "version capability" vector contiguous. So
-         * that if application wants to disable TLS1.0 in favour of
-         * TLS1>=1, it would be insufficient to pass SSL_NO_TLSv1, the
-         * answer is SSL_OP_NO_TLSv1|SSL_OP_NO_SSLv3|SSL_OP_NO_SSLv2.
-         */
-        mask = SSL_OP_NO_TLSv1_1|SSL_OP_NO_TLSv1;
-        version = TLS1_2_VERSION;
-
-        if ((options & SSL_OP_NO_TLSv1_2) && (options & mask) != mask)
-                version = TLS1_1_VERSION;
-        mask &= ~SSL_OP_NO_TLSv1_1;
-        if ((options & SSL_OP_NO_TLSv1_1) && (options & mask) != mask)
-                version = TLS1_VERSION;
-        mask &= ~SSL_OP_NO_TLSv1;
+        int ret;
 
         buf = (unsigned char *)s->init_buf->data;
         if (s->state == SSL23_ST_CW_CLNT_HELLO_A) {
                 arc4random_buf(s->s3->client_random, SSL3_RANDOM_SIZE);
 
-                if (version == TLS1_2_VERSION) {
-                        version_major = TLS1_2_VERSION_MAJOR;
-                        version_minor = TLS1_2_VERSION_MINOR;
-                } else if (version == TLS1_1_VERSION) {
-                        version_major = TLS1_1_VERSION_MAJOR;
-                        version_minor = TLS1_1_VERSION_MINOR;
-                } else if (version == TLS1_VERSION) {
-                        version_major = TLS1_VERSION_MAJOR;
-                        version_minor = TLS1_VERSION_MINOR;
-                } else {
+                if (ssl_enabled_version_range(s, NULL, &version) == -1) {
                         SSLerr(SSL_F_SSL23_CLIENT_HELLO,
                             SSL_R_NO_PROTOCOLS_AVAILABLE);
                         return (-1);
@@ -283,8 +255,8 @@ ssl23_client_hello(SSL *s)
                  */
                 d = p = &(buf[SSL3_RT_HEADER_LENGTH + SSL3_HM_HEADER_LENGTH]);
 
-                *(p++) = version_major;
-                *(p++) = version_minor;
+                *(p++) = version >> 8;
+                *(p++) = version & 0xff;
 
                 /* Random stuff */
                 memcpy(p, s->s3->client_random, SSL3_RANDOM_SIZE);
@@ -334,7 +306,7 @@ ssl23_client_hello(SSL *s)
                 /* fill in 5-byte record header */
                 d = buf;
                 *(d++) = SSL3_RT_HANDSHAKE;
-                *(d++) = version_major;
+                *(d++) = version >> 8;
 
                 /*
                  * Some servers hang if we use long client hellos
@@ -343,7 +315,7 @@ ssl23_client_hello(SSL *s)
                 if (TLS1_get_client_version(s) > TLS1_VERSION)
                         *(d++) = 1;
                 else
-                        *(d++) = version_minor;
+                        *(d++) = version & 0xff;
                 s2n((int)l, d);
 
                 /* number of bytes to write */
@@ -362,8 +334,7 @@ ssl23_client_hello(SSL *s)
 
         if ((ret >= 2) && s->msg_callback) {
                 /* Client Hello has been sent; tell msg_callback */
-
-                s->msg_callback(1, version, SSL3_RT_HANDSHAKE,
+                s->msg_callback(1, s->client_version, SSL3_RT_HANDSHAKE,
                     s->init_buf->data + 5, ret - 5, s, s->msg_callback_arg);
         }
 
diff --git a/src/lib/libssl/ssl_lib.c b/src/lib/libssl/ssl_lib.c
index 5d93a3bc13..11f46161a9 100644
--- a/src/lib/libssl/ssl_lib.c
+++ b/src/lib/libssl/ssl_lib.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssl_lib.c,v 1.122 2016/12/04 14:32:30 jsing Exp $ */
+/* $OpenBSD: ssl_lib.c,v 1.123 2016/12/30 16:57:01 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -2484,6 +2484,48 @@ SSL_get_version(const SSL *s)
         return ssl_version_string(s->version);
 }
 
+int
+ssl_enabled_version_range(SSL *s, uint16_t *min_ver, uint16_t *max_ver)
+{
+        uint16_t min_version, max_version;
+
+        /*
+         * The enabled versions have to be a contiguous range, which means we
+         * cannot enable and disable single versions at our whim, even though
+         * this is what the OpenSSL flags allow. The historical way this has
+         * been handled is by making a flag mean that all higher versions
+         * are disabled, if any version lower than the flag is enabled.
+         */
+
+        min_version = 0;
+        max_version = TLS1_2_VERSION;
+
+        if ((s->options & SSL_OP_NO_TLSv1) == 0)
+                min_version = TLS1_VERSION;
+        else if ((s->options & SSL_OP_NO_TLSv1_1) == 0)
+                min_version = TLS1_1_VERSION;
+        else if ((s->options & SSL_OP_NO_TLSv1_2) == 0)
+                min_version = TLS1_2_VERSION;
+
+        if ((s->options & SSL_OP_NO_TLSv1_2) && min_version < TLS1_2_VERSION)
+                max_version = TLS1_1_VERSION;
+        if ((s->options & SSL_OP_NO_TLSv1_1) && min_version < TLS1_1_VERSION)
+                max_version = TLS1_VERSION;
+        if ((s->options & SSL_OP_NO_TLSv1) && min_version < TLS1_VERSION)
+                max_version = 0;
+
+        /* Everything has been disabled... */
+        if (min_version == 0 || max_version == 0)
+                return -1;
+
+        if (min_ver != NULL)
+                *min_ver = min_version;
+        if (max_ver != NULL)
+                *max_ver = max_version;
+
+        return 0;
+}
+
 uint16_t
 ssl_max_server_version(SSL *s)
 {
diff --git a/src/lib/libssl/ssl_locl.h b/src/lib/libssl/ssl_locl.h
index de977846a4..e8fbd23572 100644
--- a/src/lib/libssl/ssl_locl.h
+++ b/src/lib/libssl/ssl_locl.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssl_locl.h,v 1.142 2016/12/30 15:12:45 jsing Exp $ */
+/* $OpenBSD: ssl_locl.h,v 1.143 2016/12/30 16:57:01 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -497,6 +497,7 @@ extern SSL3_ENC_METHOD ssl3_undef_enc_method;
 extern SSL_CIPHER ssl3_ciphers[];
 
 const char *ssl_version_string(int ver);
+int ssl_enabled_version_range(SSL *s, uint16_t *min_ver, uint16_t *max_ver);
 uint16_t ssl_max_server_version(SSL *s);
 
 extern SSL3_ENC_METHOD DTLSv1_enc_data;