[issue42937] 192.0.0.8 (IPv4 dummy address) considered globally reachable

[Wayne Johnston]

Wayne Johnston  added the comment:

I completely agree with comments about .is_global and special_use.  Private IPs 
are just a subset of special use.  For some part Private means the Private use 
networks reserved by IANA and specified in IETF RFC1918.  

For this PR "IPv4 dummy address" is for sure not global.  Technically, it is 
not a private use IP either.  Just following what others have done.  I really 
like the apporoach of removing the routable special IPs.  Let me know if I 
should create a PR to do this.  This would include adding specific special use 
constant plus a whole bunch of very specific constants.  A constant like 
is_dummy will be added.

I pretty much have the code ready to go for IPV4.

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[issue42937] 192.0.0.8 (IPv4 dummy address) considered globally reachable

[Martijn Pieters]

Martijn Pieters  added the comment:

> Private is a subset of special use.  Should a "_special_use" constant be 
> created.  This would include multicast, link_local, private_use, and a few 
> more.

There are already dedicated tests for those other special use networks in 
ipaddress. 192.0.0.0/24 is the block reserved for "IETF Protocol Assignments", 
which really means: private use. 
https://datatracker.ietf.org/doc/html/rfc6890#section-2.2.2 marks the block as 
"Not usable unless by virtue of a more specific reservation.".

The registry at 
https://www.iana.org/assignments/iana-ipv4-special-registry/iana-ipv4-special-registry.xhtml
 lists those specific reservations, and only 2 to date are *globally 
reachable*, which means they are probably not private:

- 192.0.0.9/32, Port Control Protocol Anycast, RFC 7723
- 192.0.0.10/32, Traversal Using Relays around NAT Anycast, RFC 8155

I strongly feel that _any other IP address in the reserved range_ should be 
treated as private unless marked, by IANA, as globally reachable, at some 
future date.

That would require the list of networks for IPv4Address / IPv4Network 
is_private to include all of 192.0.0.0/24 _minus those two exceptions_; 
calculating the network masks for these:

>>> def exclude_all(network, *excluded):
... try:
... for sub in network.address_exclude(excluded[0]):
... yield from exclude_all(sub, *excluded[1:])
... except (IndexError, ValueError):
... yield network
...
>>> iana_reserved = IPv4Network("192.0.0.0/24")
>>> to_remove = IPv4Network("192.0.0.9/32"), IPv4Network("192.0.0.10/32")

>>> for sub in exclude_all(iana_reserved, *to_remove):
... print(sub)
...
192.0.0.128/25
192.0.0.64/26
192.0.0.32/27
192.0.0.16/28
192.0.0.0/29
192.0.0.12/30
192.0.0.11/32
192.0.0.8/32

The module could trivially do this on import, or we could hard-code the above 
list.

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[issue42937] 192.0.0.8 (IPv4 dummy address) considered globally reachable

[Martijn Pieters]

Martijn Pieters  added the comment:

Oops, I got my issue numbers mixed up. This is related to #44167, I meant.

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[issue42937] 192.0.0.8 (IPv4 dummy address) considered globally reachable

[Martijn Pieters]

Martijn Pieters  added the comment:

This is related to #42937, the IPv4 private network list is not considering the 
whole of 192.0.0.0/24 to be private.

RFC 5736 / 6890 reserved 192.0.0.0/24 for special purposes (private networks) 
and to date a few subnets of that network have received assignments. The 
ipaddress modules should use that subnet for any `is_private` test, and not 
just the subnets of that network that have received specific assignments.

E.g. the list currently contains just 192.0.0.0/29 and 192.0.0.170/31, but as 
this bug report points out, 192.0.0.8/32 has since been added, as have 
192.0.0.9/32 and 192.0.0.10/32.

The IPv6 implementation *does* cover the whole reserved subnet (although it 
also includes 2 specific registrations, see the aforementioned #42937), it is 
just IPv4 that is inconsistent and incomplete here.

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[issue42937] 192.0.0.8 (IPv4 dummy address) considered globally reachable

[Wayne Johnston]

Change by Wayne Johnston :


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[issue42937] 192.0.0.8 (IPv4 dummy address) considered globally reachable

[Wayne Johnston]

Wayne Johnston  added the comment:

This a simple matter of adding the address to the _private_networks constant.   
I will add it and issue a pull request today/tomorrow.  I could add some of the 
others too for completeness.   However, these are really special use versus 
private.   Private is a subset of special use.  Should a "_special_use" 
constant be created.  This would include multicast, link_local, private_use, 
and a few more.

There are many others included in  
https://www.iana.org/assignments/iana-ipv4-special-registry/iana-ipv4-special-registry.xhtml.

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[issue42937] 192.0.0.8 (IPv4 dummy address) considered globally reachable

[CDirkx]

New submission from CDirkx :

Currently the method `ipaddress.is_global` returns true for the IPv4 address 
192.0.0.8. This was correct when `is_global` was initially implemented, but in 
2015 192.0.0.8 got designated as the "IPv4 dummy address" and not globally 
reachable, see the IANA special purpose address registry: 
https://www.iana.org/assignments/iana-ipv4-special-registry/iana-ipv4-special-registry.xhtml.

The correct behaviour now, according to the documentation of `is_global` which 
refers to the IANA registry, would be to return false for 192.0.0.8.

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messages: 385127
nosy: cdirkx
priority: normal
severity: normal
status: open
title: 192.0.0.8 (IPv4 dummy address) considered globally reachable
type: behavior
versions: Python 3.9

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