[Swan-dev] large numbers in libreswan conf files

[Andrew Cagney]

On Tue, 30 Aug 2022 at 22:31, D. Hugh Redelmeier <hugh at mimosa.com> wrote:
>
> All numbers in conf files are whole numbers (that's all the parser
> will accept).

Let's say all byte counts.
(I've a long standing wish list item for accepting things like
timeout=0.5s which would mean a separate parser)

>
> How large should we allow them to be?

>= 64-bit.  Even my ancient 1Gibit hub could overflow a 32-bit byte counter in under 1 minute..

> Slightly easier question; What are the largest numbers used now?  I
> cannot answer that because I can't see everyones conf files.
>
> ===> People: could you tell me the large numbers appearing in your
> conf files?  It would also be nice to know which parameters are being
> set to these large numbers.
>
> I found all the large decimal numbers in pluto conf files in our test
> suite.  I defined "large" as five or more digits.
>
>         grep -n '\<[0-9][0-9][0-9][0-9][0-9][0-9]*\>'
>
> All but one were milliseconds for retransmit-interval, all 10-25
> seconds -- 5 digit numbers.
>
> The one exception:
> pluto/pfkeyv2-replay-window-freebsd/ipsec.conf:37:      replay-window=4294967294 # UINT32_MAX - 1
> This seems pretty arbitrary.
>
> How large are the numbers you use (or imagine using)?
>
> Numerical parameters are currently stored as uintmax_t.  I've already
> posted why this type should not be used.  This sample suggests that
> 32-bit numbers should be enough.  So "unsigned long" should be fine.  (C
> guarantees the unsigned long is 32 bits or more.)

While uintmax_t has limitations (a C committee snafu means it will
never be bigger than 64-bit) I think it is fit for purpose:

- it's "generic"
- it's >= 64-bits for the systems we care about
- it's fast on the systems we care about (our bottleneck is crypto
which uses bignum)
- it's easy to print using 'j'
- it's a marker for the poor soul (we'll all be long gone) who gets to
deal with 128-bit ints; I suspect it will use bignums

I think we're better off limiting uint64_t to code that must use a
64-bit value (for instance, in payloads).

> If 32 bits is considered too limiting, 64 should be used.  The
> portable way of specifying this is uint64_t.
>
> (I don't really like C unsigned types because overflow is well-defined
> to be a surprisinig result.  But that's C for you.  Using unsigned
> puts a burden on the program to detect overflow.  There is evidence
> that we're not perfect at that.)
>
> Complete collection:
>
> pluto/ikev2-x509-26-criticalflag/east.conf:28:  retransmit-interval=15000
> pluto/ikev2-x509-26-criticalflag/west.conf:28:  retransmit-interval=15000
> pluto/ikev2-labeled-ipsec-06-reauth-ike-acquire/west.conf:15:   retransmit-interval=10000 # 10s
> pluto/ikev2-x509-27-criticalflag-clientAuth/east.conf:28:       retransmit-interval=15000
> pluto/ikev2-x509-27-criticalflag-clientAuth/west.conf:28:       retransmit-interval=15000
> pluto/ikev2-labeled-ipsec-06-rekey-ike-acquire/west.conf:15:    retransmit-interval=10000 # 10s
> pluto/pfkeyv2-replay-window-freebsd/ipsec.conf:37:      replay-window=4294967294 # UINT32_MAX - 1
> pluto/xauth-pluto-20-pam-timeout/road.conf:17:  retransmit-interval=25000
> pluto/ikev2-60-pam/road.conf:14:        retransmit-interval=25000
> pluto/ikev2-60-pam/road.conf:18:        retransmit-interval=25000
> pluto/ikev2-frag-03-retrans/east.conf:20:       retransmit-interval=15000
> pluto/ikev2-frag-03-retrans/west.conf:21:       retransmit-interval=15000
> pluto/ikev2-child-rekey-08-deadlock/ipsec.conf:32:      retransmit-interval=14000
> pluto/interop-ikev1-strongswan-x509-aggr-13-san-dn-match-responder/west.conf:28:        retransmit-interval=20000 #strongswan may take time to fetch the crl
> pluto/interop-ikev2-strongswan-39-fragmentation-aes-gcm/west.conf:23:   retransmit-interval=15000
> pluto/ikev2-x509-02-eku/east.conf:28:   retransmit-interval=15000
> pluto/ikev2-x509-02-eku/west.conf:28:   retransmit-interval=15000
> pluto/nss-cert-ocsp-03-bogus-uri-strict-ikev1/east.conf:33:     retransmit-interval=15000 # slow retransmits
> pluto/nss-cert-ocsp-03-bogus-uri-strict-ikev1/west.conf:28:     retransmit-interval=15000 # slow retransmits
> w
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