Vulnerability Development mailing list archives

Re: Red Hat 7.1 rpc.statd problem


From: Valdis.Kletnieks () vt edu
Date: Thu, 06 Dec 2001 11:49:43 -0500

On Thu, 06 Dec 2001 03:49:08 +0700, Fyodor said:

I guess 63(?) characters is the hostname max length according to RFC. So
it is probably statd messup/overlook not to chop it. (although I doubt
it would make much harm in this case).. 

RFC1123, section 2.1:

   2.1  Host Names and Numbers

      The syntax of a legal Internet host name was specified in RFC-952
      [DNS:4].  One aspect of host name syntax is hereby changed: the
      restriction on the first character is relaxed to allow either a
      letter or a digit.  Host software MUST support this more liberal
      syntax.

      Host software MUST handle host names of up to 63 characters and
      SHOULD handle host names of up to 255 characters.

      Whenever a user inputs the identity of an Internet host, it SHOULD
      be possible to enter either (1) a host domain name or (2) an IP
      address in dotted-decimal ("#.#.#.#") form.  The host SHOULD check
      the string syntactically for a dotted-decimal number before
      looking it up in the Domain Name System.

RFC1035, section 2.3.4:

2.3.4. Size limits

Various objects and parameters in the DNS have size limits.  They are
listed below.  Some could be easily changed, others are more
fundamental.

labels          63 octets or less

names           255 octets or less

TTL             positive values of a signed 32 bit number.

UDP messages    512 octets or less


So it's a hostname of 255 chars or less, with no more than 63 characters
per each level of domain name.

I mention this because I've seen too many 'char hostname[64];' in my life ;)
-- 
                                Valdis Kletnieks
                                Operating Systems Analyst
                                Virginia Tech

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