PR: 2089

Submitted by: Robin Seggelmann <seggelmann@fh-muenster.de>
Approved by: steve@openssl.org

DTLS Fragment size bug fix.

diff --git a/ssl/d1_both.c b/ssl/d1_both.c
index de96622f864a850c91d5600fbe166219763f39ad..b7ead8ad228eb18f363c61d8a19c081a67432b42 100644 (file)
--- a/ssl/d1_both.c
+++ b/ssl/d1_both.c
@@ -177,7 +177,7 @@ int dtls1_do_write(SSL *s, int type)
        {
        int ret;
        int curr_mtu;
-       unsigned int len, frag_off;
+       unsigned int len, frag_off, mac_size, blocksize;
 
        /* AHA!  Figure out the MTU, and stick to the right size */
        if ( ! (SSL_get_options(s) & SSL_OP_NO_QUERY_MTU))
@@ -225,11 +225,22 @@ int dtls1_do_write(SSL *s, int type)
                OPENSSL_assert(s->init_num == 
                        (int)s->d1->w_msg_hdr.msg_len + DTLS1_HM_HEADER_LENGTH);
 
+       if (s->write_hash)
+               mac_size = EVP_MD_CTX_size(s->write_hash);
+       else
+               mac_size = 0;
+
+       if (s->enc_write_ctx && 
+               (EVP_CIPHER_mode( s->enc_write_ctx->cipher) & EVP_CIPH_CBC_MODE))
+               blocksize = 2 * EVP_CIPHER_block_size(s->enc_write_ctx->cipher);
+       else
+               blocksize = 0;
+
        frag_off = 0;
        while( s->init_num)
                {
                curr_mtu = s->d1->mtu - BIO_wpending(SSL_get_wbio(s)) - 
-                       DTLS1_RT_HEADER_LENGTH;
+                       DTLS1_RT_HEADER_LENGTH - mac_size - blocksize;
 
                if ( curr_mtu <= DTLS1_HM_HEADER_LENGTH)
                        {
@@ -237,7 +248,8 @@ int dtls1_do_write(SSL *s, int type)
                        ret = BIO_flush(SSL_get_wbio(s));
                        if ( ret <= 0)
                                return ret;
-                       curr_mtu = s->d1->mtu - DTLS1_RT_HEADER_LENGTH;
+                       curr_mtu = s->d1->mtu - DTLS1_RT_HEADER_LENGTH -
+                               mac_size - blocksize;
                        }
 
                if ( s->init_num > curr_mtu)