Server side version negotiation rewrite

This commit changes the way that we do server side protocol version
negotiation. Previously we had a whole set of code that had an "up front"
state machine dedicated to the negotiating the protocol version. This adds
significant complexity to the state machine. Historically the justification
for doing this was the support of SSLv2 which works quite differently to
SSLv3+. However, we have now removed support for SSLv2 so there is little
reason to maintain this complexity.

The one slight difficulty is that, although we no longer support SSLv2, we
do still support an SSLv3+ ClientHello in an SSLv2 backward compatible
ClientHello format. This is generally only used by legacy clients. This
commit adds support within the SSLv3 code for these legacy format
ClientHellos.

Server side version negotiation now works in much the same was as DTLS,
i.e. we introduce the concept of TLS_ANY_VERSION. If s->version is set to
that then when a ClientHello is received it will work out the most
appropriate version to respond with. Also, SSLv23_method and
SSLv23_server_method have been replaced with TLS_method and
TLS_server_method respectively. The old SSLv23* names still exist as
macros pointing at the new name, although they are deprecated.

Subsequent commits will look at client side version negotiation, as well of
removal of the old s23* code.

Reviewed-by: Kurt Roeckx <kurt@openssl.org>

1 files changed, 91 insertions, 40 deletions

diff --git a/ssl/record/ssl3_record.c b/ssl/record/ssl3_record.c
index 0328127..190abd2 100644
--- a/ssl/record/ssl3_record.c
+++ b/ssl/record/ssl3_record.c
@@ -166,6 +166,7 @@ void SSL3_RECORD_set_seq_num(SSL3_RECORD *r, const unsigned char *seq_num)
  */
 #define MAX_EMPTY_RECORDS 32
 
+#define SSL2_RT_HEADER_LENGTH   2
 /*-
  * Call this to get a new input record.
  * It will return <= 0 if more data is needed, normally due to an error
@@ -216,71 +217,121 @@ int ssl3_get_record(SSL *s)
         RECORD_LAYER_set_rstate(&s->rlayer, SSL_ST_READ_BODY);
 
         p = RECORD_LAYER_get_packet(&s->rlayer);
-        if (s->msg_callback)
-            s->msg_callback(0, 0, SSL3_RT_HEADER, p, 5, s,
-                            s->msg_callback_arg);
 
-        /* Pull apart the header into the SSL3_RECORD */
-        rr->type = *(p++);
-        ssl_major = *(p++);
-        ssl_minor = *(p++);
-        version = (ssl_major << 8) | ssl_minor;
-        n2s(p, rr->length);
+        /*
+         * Check whether this is a regular record or an SSLv2 style record. The
+         * latter is only used in an initial ClientHello for old clients.
+         */
+        if (s->first_packet && s->server && !s->read_hash && !s->enc_read_ctx
+                && (p[0] & 0x80) && (p[2] == SSL2_MT_CLIENT_HELLO)) {
+            /* SSLv2 style record */
+            if (s->msg_callback)
+                s->msg_callback(0, SSL2_VERSION, 0,  p + 2,
+                                RECORD_LAYER_get_packet_length(&s->rlayer) - 2,
+                                s, s->msg_callback_arg);
+
+            rr->type = SSL3_RT_HANDSHAKE;
+            rr->rec_version = SSL2_VERSION;
+
+            rr->length = ((p[0] & 0x7f) << 8) | p[1];
+
+            if (rr->length > SSL3_BUFFER_get_len(&s->rlayer.rbuf)
+                                    - SSL2_RT_HEADER_LENGTH) {
+                al = SSL_AD_RECORD_OVERFLOW;
+                SSLerr(SSL_F_SSL3_GET_RECORD, SSL_R_PACKET_LENGTH_TOO_LONG);
+                goto f_err;
+            }
 
-        /* Lets check version */
-        if (!s->first_packet) {
-            if (version != s->version) {
-                SSLerr(SSL_F_SSL3_GET_RECORD, SSL_R_WRONG_VERSION_NUMBER);
-                if ((s->version & 0xFF00) == (version & 0xFF00)
-                    && !s->enc_write_ctx && !s->write_hash)
-                    /*
-                     * Send back error using their minor version number :-)
-                     */
-                    s->version = (unsigned short)version;
-                al = SSL_AD_PROTOCOL_VERSION;
+            if (rr->length < MIN_SSL2_RECORD_LEN) {
+                al = SSL_AD_HANDSHAKE_FAILURE;
+                SSLerr(SSL_F_SSL3_GET_RECORD, SSL_R_LENGTH_TOO_SHORT);
                 goto f_err;
             }
-        }
+        } else {
+            /* SSLv3+ style record */
+            if (s->msg_callback)
+                s->msg_callback(0, 0, SSL3_RT_HEADER, p, 5, s,
+                                s->msg_callback_arg);
+
+            /* Pull apart the header into the SSL3_RECORD */
+            rr->type = *(p++);
+            ssl_major = *(p++);
+            ssl_minor = *(p++);
+            version = (ssl_major << 8) | ssl_minor;
+            rr->rec_version = version;
+            n2s(p, rr->length);
+
+            /* Lets check version */
+            if (!s->first_packet) {
+                if (version != s->version) {
+                    SSLerr(SSL_F_SSL3_GET_RECORD, SSL_R_WRONG_VERSION_NUMBER);
+                    if ((s->version & 0xFF00) == (version & 0xFF00)
+                        && !s->enc_write_ctx && !s->write_hash)
+                        /*
+                         * Send back error using their minor version number :-)
+                         */
+                        s->version = (unsigned short)version;
+                    al = SSL_AD_PROTOCOL_VERSION;
+                    goto f_err;
+                }
+            }
 
-        if ((version >> 8) != SSL3_VERSION_MAJOR) {
-            SSLerr(SSL_F_SSL3_GET_RECORD, SSL_R_WRONG_VERSION_NUMBER);
-            goto err;
-        }
+            if ((version >> 8) != SSL3_VERSION_MAJOR) {
+                SSLerr(SSL_F_SSL3_GET_RECORD, SSL_R_WRONG_VERSION_NUMBER);
+                goto err;
+            }
 
-        if (rr->length >
-                SSL3_BUFFER_get_len(&s->rlayer.rbuf)
-                - SSL3_RT_HEADER_LENGTH) {
-            al = SSL_AD_RECORD_OVERFLOW;
-            SSLerr(SSL_F_SSL3_GET_RECORD, SSL_R_PACKET_LENGTH_TOO_LONG);
-            goto f_err;
+            if (rr->length >
+                    SSL3_BUFFER_get_len(&s->rlayer.rbuf)
+                    - SSL3_RT_HEADER_LENGTH) {
+                al = SSL_AD_RECORD_OVERFLOW;
+                SSLerr(SSL_F_SSL3_GET_RECORD, SSL_R_PACKET_LENGTH_TOO_LONG);
+                goto f_err;
+            }
         }
 
         /* now s->rlayer.rstate == SSL_ST_READ_BODY */
     }
 
-    /* s->rlayer.rstate == SSL_ST_READ_BODY, get and decode the data */
-
-    if (rr->length >
-        RECORD_LAYER_get_packet_length(&s->rlayer) - SSL3_RT_HEADER_LENGTH) {
-        /* now s->packet_length == SSL3_RT_HEADER_LENGTH */
+    /*
+     * s->rlayer.rstate == SSL_ST_READ_BODY, get and decode the data.
+     * Calculate how much more data we need to read for the rest of the record
+     */
+    if (rr->rec_version == SSL2_VERSION) {
+        i = rr->length + SSL2_RT_HEADER_LENGTH - SSL3_RT_HEADER_LENGTH;
+    } else {
         i = rr->length;
+    }
+    if (i > 0) {
+        /* now s->packet_length == SSL3_RT_HEADER_LENGTH */
+
         n = ssl3_read_n(s, i, i, 1);
         if (n <= 0)
             return (n);         /* error or non-blocking io */
         /*
-         * now n == rr->length, and s->packet_length == SSL3_RT_HEADER_LENGTH
-         * + rr->length
+         * now n == rr->length, and
+         * s->packet_length == SSL3_RT_HEADER_LENGTH + rr->length
+         * or
+         * s->packet_length == SSL2_RT_HEADER_LENGTH + rr->length
+         * (if SSLv2 packet)
          */
+    } else {
+        n = 0;
     }
 
     /* set state for later operations */
     RECORD_LAYER_set_rstate(&s->rlayer, SSL_ST_READ_HEADER);
 
     /*
-     * At this point, s->packet_length == SSL3_RT_HEADER_LNGTH + rr->length,
+     * At this point, s->packet_length == SSL3_RT_HEADER_LENGTH + rr->length,
+     * or s->packet_length == SSL2_RT_HEADER_LENGTH + rr->length
      * and we have that many bytes in s->packet
      */
-    rr->input = &(RECORD_LAYER_get_packet(&s->rlayer)[SSL3_RT_HEADER_LENGTH]);
+    if(rr->rec_version == SSL2_VERSION) {
+        rr->input = &(RECORD_LAYER_get_packet(&s->rlayer)[SSL2_RT_HEADER_LENGTH]);
+    } else {
+        rr->input = &(RECORD_LAYER_get_packet(&s->rlayer)[SSL3_RT_HEADER_LENGTH]);
+    }
 
     /*
      * ok, we can now read from 's->packet' data into 'rr' rr->input points