safety check to ensure we dont send out beyond the users buffer

diff --git a/ssl/s3_pkt.c b/ssl/s3_pkt.c
index d601a1817182f88108a3ef34017c37e8027df97b..41193bb7d162a42cd46dd6deca97de55ab175e57 100644 (file)
--- a/ssl/s3_pkt.c
+++ b/ssl/s3_pkt.c
@@ -816,6 +816,21 @@ int ssl3_write_bytes(SSL *s, int type, const void *buf_, int len)
                return tot;
                }
 
+       /* ensure that if we end up with a smaller value of data to write 
+        * out than the the original len from a write which didn't complete 
+        * for non-blocking I/O and also somehow ended up avoiding 
+        * the check for this in ssl3_write_pending/SSL_R_BAD_WRITE_RETRY as
+        * it must never be possible to end up with (len-tot) as a large
+        * number that will then promptly send beyond the end of the users
+        * buffer ... so we trap and report the error in a way the user
+        * will notice
+        */
+       if ( len < tot)
+               {
+               SSLerr(SSL_F_SSL3_WRITE_BYTES,SSL_R_BAD_LENGTH);
+               return(-1);
+               }
+
        n=(len-tot);
        for (;;)
                {