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Re: [TLS] I-D Action:draft-ietf-tls-dtls-heartbeat-01.txt

Simon Josefsson <simon@josefsson.org> Thu, 27 January 2011 12:35 UTC

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From: Simon Josefsson <simon@josefsson.org>
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Date: Thu, 27 Jan 2011 13:38:43 +0100
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Subject: Re: [TLS] I-D Action:draft-ietf-tls-dtls-heartbeat-01.txt
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This looks like a useful extension, it is similar to the unfortunately
non-standard keepalive feature in SSH (that I happened to implement for
libssh2 not long ago).

I have one mild concern with permitting arbitrary payload.  What is the
rationale for this?  It opens up for a side channel in TLS.  It could
also be abused to send non-standardized data.  Further, is there any
reason to allow arbitrary sized payload?  In my opinion, the
payload_length, payload and padding fields seems unnecessary to me.

/Simon

   struct {
      HeartbeatMessageType type;
      uint16 payload_length;
      opaque payload[HeartbeatMessage.payload_length];
      opaque padding[padding_length];
   } HeartbeatMessage;

   The length of a HeartbeatMessage in total MUST NOT exceed 2^14 or
   max_fragment_length when negotiated as defined in [RFC6066].

   type  The message type, either heartbeat_request or
      heartbeat_response.

   payload_length  The length of the payload.

   payload  The payload consists of arbitrary content.

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