From 64dffc5d144d74bbb8b0484c51c9195ff5cbdb0e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Manuel=20P=C3=A9gouri=C3=A9-Gonnard?= <mpg@elzevir.fr>
Date: Tue, 2 Sep 2014 13:39:16 +0200
Subject: [PATCH] Make handshake reassembly work with openssl

---
 include/polarssl/ssl.h |  4 ++--
 library/ssl_tls.c      | 29 ++++++++++++++++++++++++++++-
 tests/ssl-opt.sh       | 41 ++++++++++++++++++++---------------------
 3 files changed, 50 insertions(+), 24 deletions(-)

diff --git a/include/polarssl/ssl.h b/include/polarssl/ssl.h
index bf20c37ac..7474c14ab 100644
--- a/include/polarssl/ssl.h
+++ b/include/polarssl/ssl.h
@@ -779,8 +779,8 @@ struct _ssl_context
     size_t in_msglen;           /*!< record header: message length    */
     size_t in_left;             /*!< amount of data read so far       */
 #if defined(POLARSSL_SSL_PROTO_DTLS)
-    size_t next_record_offset;  /*!< offset of the next record in datagram,
-                                     or 0 if none */
+    size_t next_record_offset;  /*!< offset of the next record in datagram
+                                     (equal to in_left if none)       */
 #endif
 
     size_t in_hslen;            /*!< current handshake message length */
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 95fcdfbef..39d93f9c3 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -1832,7 +1832,7 @@ static int ssl_decompress_buf( ssl_context *ssl )
  * with datagram transport (DTLS) on success ssl->in_left >= nb_want,
  * since we always read a whole datagram at once.
  *
- * For DTLS, It is up to the caller to set ssl->next_record_offset when
+ * For DTLS, it is up to the caller to set ssl->next_record_offset when
  * they're done reading a record.
  */
 int ssl_fetch_input( ssl_context *ssl, size_t nb_want )
@@ -2289,6 +2289,31 @@ static int ssl_reassemble_dtls_handshake( ssl_context *ssl )
 
     SSL_DEBUG_MSG( 2, ( "handshake message completed" ) );
 
+    if( ssl->in_left > ssl->next_record_offset )
+    {
+        /*
+         * We've got more data in the buffer after the current record,
+         * that we don't want to overwrite. Move it before writing the
+         * reassembled message, and adjust in_left and next_record_offset.
+         */
+        unsigned char *cur_remain = ssl->in_hdr + ssl->next_record_offset;
+        unsigned char *new_remain = ssl->in_msg + ssl->in_hslen;
+        size_t remain_len = ssl->in_left - ssl->next_record_offset;
+
+        /* First compute and check new lengths */
+        ssl->next_record_offset = new_remain - ssl->in_hdr;
+        ssl->in_left = ssl->next_record_offset + remain_len;
+
+        if( ssl->in_left > SSL_BUFFER_LEN -
+                           (size_t)( ssl->in_hdr - ssl->in_buf ) )
+        {
+            SSL_DEBUG_MSG( 1, ( "reassembled message too large for buffer" ) );
+            return( POLARSSL_ERR_SSL_BUFFER_TOO_SMALL );
+        }
+
+        memmove( new_remain, cur_remain, remain_len );
+    }
+
     memcpy( ssl->in_msg, ssl->handshake->hs_msg, ssl->in_hslen );
 
     polarssl_free( ssl->handshake->hs_msg );
@@ -2409,6 +2434,8 @@ int ssl_read_record( ssl_context *ssl )
         return( ret );
     }
 
+    SSL_DEBUG_BUF( 4, "input record header", ssl->in_hdr, ssl_hdr_len( ssl ) );
+
     ssl->in_msgtype =  ssl->in_hdr[0];
     ssl->in_msglen = ( ssl->in_len[0] << 8 ) | ssl->in_len[1];
     ssl_read_version( &major_ver, &minor_ver, ssl->transport, ssl->in_hdr + 1 );
diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index d5b1a296d..13847dd9b 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -1988,27 +1988,26 @@ run_test    "DTLS reassembly: no fragmentation (openssl server)" \
             -C "found fragmented DTLS handshake message" \
             -C "error"
 
-# Not working yet
-#run_test    "DTLS reassembly: fragmentation (openssl server)" \
-#            "$O_SRV -dtls1 -mtu 256" \
-#            "$P_CLI dtls=1 debug_level=2" \
-#            0 \
-#            -c "found fragmented DTLS handshake message" \
-#            -C "error"
-#
-#run_test    "DTLS reassembly: fragmentation (openssl server)" \
-#            "$O_SRV -dtls1 -mtu 256" \
-#            "$P_CLI dtls=1 debug_level=2" \
-#            0 \
-#            -c "found fragmented DTLS handshake message" \
-#            -C "error"
-#
-#run_test    "DTLS reassembly: fragmentation, nbio (openssl server)" \
-#            "$O_SRV -dtls1 -mtu 256" \
-#            "$P_CLI dtls=1 nbio=2 debug_level=2" \
-#            0 \
-#            -c "found fragmented DTLS handshake message" \
-#            -C "error"
+run_test    "DTLS reassembly: fragmentation (openssl server)" \
+            "$O_SRV -dtls1 -mtu 256" \
+            "$P_CLI dtls=1 debug_level=2" \
+            0 \
+            -c "found fragmented DTLS handshake message" \
+            -C "error"
+
+run_test    "DTLS reassembly: fragmentation (openssl server)" \
+            "$O_SRV -dtls1 -mtu 256" \
+            "$P_CLI dtls=1 debug_level=2" \
+            0 \
+            -c "found fragmented DTLS handshake message" \
+            -C "error"
+
+run_test    "DTLS reassembly: fragmentation, nbio (openssl server)" \
+            "$O_SRV -dtls1 -mtu 256" \
+            "$P_CLI dtls=1 nbio=2 debug_level=2" \
+            0 \
+            -c "found fragmented DTLS handshake message" \
+            -C "error"
 
 # TODO: fragmentation with renegotiation, openssl + gnutls