Re: [TLS] Length of a variable-length vector: Could it be an odd multiple?

"Hodges, Jeff" <jeff.hodges@paypal.com> Wed, 20 January 2016 18:47 UTC

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From: "Hodges, Jeff" <jeff.hodges@paypal.com>
To: Benjamin Kaduk <bkaduk@akamai.com>, Jong-Shian Wu <js@crypto.tw>, "tls@ietf.org" <tls@ietf.org>
Thread-Topic: [TLS] Length of a variable-length vector: Could it be an odd multiple?
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Date: Wed, 20 Jan 2016 18:47:12 +0000
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Subject: Re: [TLS] Length of a variable-length vector: Could it be an odd multiple?
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On 1/13/16, 12:53 PM, "Benjamin Kaduk" <bkaduk@akamai.com>; wrote:
>On 01/13/2016 02:44 PM, Jong-Shian Wu wrote:
>> I have a question about the even-vs-odd restrictions on the length of
>> a valid variable-length vector defined in TLS specification after
>> reading the section 4.3 of RFC 5246 [1] which states that:

>>"The length of an encoded vector must be an even multiple of the length
>>of a single element (for example, a 17-byte vector of uint16 would be
>> illegal)."
>>
>
>It means "whole-number" as opposed to fractional, i.e., there should not
>be unused "junk bytes" at the end.

In case it's helpful, here's a suggested re-write of that quoted sentence
above..

  The length of an encoded variable-length vector must be an
  exact multiple of the length of a single element. For example,
  an encoded 17-byte vector of uint16 would be illegal, and an
  encoded variable-length vector of four 32 byte elements,
  having a ceiling of 2^16-1, will be 130 bytes long overall
  (2 byte length field followed by 128 bytes of data).

..assuming I'm correctly understanding variable-length vectors :)

HTH,

=JeffH