view mercurial/dummycert.pem @ 32697:19b9fc40cc51

revlog: skeleton support for version 2 revlogs

There are a number of improvements we want to make to revlogs
that will require a new version - version 2. It is unclear what the
full set of improvements will be or when we'll be done with them.
What I do know is that the process will likely take longer than a
single release, will require input from various stakeholders to
evaluate changes, and will have many contentious debates and
bikeshedding.

It is unrealistic to develop revlog version 2 up front: there
are just too many uncertainties that we won't know until things
are implemented and experiments are run. Some changes will also
be invasive and prone to bit rot, so sitting on dozens of patches
is not practical.

This commit introduces skeleton support for version 2 revlogs in
a way that is flexible and not bound by backwards compatibility
concerns.

An experimental repo requirement for denoting revlog v2 has been
added. The requirement string has a sub-version component to it.
This will allow us to declare multiple requirements in the course
of developing revlog v2. Whenever we change the in-development
revlog v2 format, we can tweak the string, creating a new
requirement and locking out old clients. This will allow us to
make as many backwards incompatible changes and experiments to
revlog v2 as we want. In other words, we can land code and make
meaningful progress towards revlog v2 while still maintaining
extreme format flexibility up until the point we freeze the
format and remove the experimental labels.

To enable the new repo requirement, you must supply an experimental
and undocumented config option. But not just any boolean flag
will do: you need to explicitly use a value that no sane person
should ever type. This is an additional guard against enabling
revlog v2 on an installation it shouldn't be enabled on. The
specific scenario I'm trying to prevent is say a user with a
4.4 client with a frozen format enabling the option but then
downgrading to 4.3 and accidentally creating repos with an
outdated and unsupported repo format. Requiring a "challenge"
string should prevent this.

Because the format is not yet finalized and I don't want to take
any chances, revlog v2's version is currently 0xDEAD. I figure
squatting on a value we're likely never to use as an actual revlog
version to mean "internal testing only" is acceptable. And
"dead" is easily recognized as something meaningful.

There is a bunch of cleanup that is needed before work on revlog
v2 begins in earnest. I plan on doing that work once this patch
is accepted and we're comfortable with the idea of starting down
this path.

A dummy certificate that will make OS X 10.6+ Python use the system CA
certificate store:

-----BEGIN CERTIFICATE-----
MIIBIzCBzgIJANjmj39sb3FmMA0GCSqGSIb3DQEBBQUAMBkxFzAVBgNVBAMTDmhn
LmV4YW1wbGUuY29tMB4XDTE0MDgzMDA4NDU1OVoXDTE0MDgyOTA4NDU1OVowGTEX
MBUGA1UEAxMOaGcuZXhhbXBsZS5jb20wXDANBgkqhkiG9w0BAQEFAANLADBIAkEA
mh/ZySGlcq0ALNLmA1gZqt61HruywPrRk6WyrLJRgt+X7OP9FFlEfl2tzHfzqvmK
CtSQoPINWOdAJMekBYFgKQIDAQABMA0GCSqGSIb3DQEBBQUAA0EAF9h49LkSqJ6a
IlpogZuUHtihXeKZBsiktVIDlDccYsNy0RSh9XxUfhk+XMLw8jBlYvcltSXdJ7We
aKdQRekuMQ==
-----END CERTIFICATE-----

This certificate was generated to be syntactically valid but never be usable;
it expired before it became valid.

Created as:

  $ cat > cn.conf << EOT
  > [req]
  > distinguished_name = req_distinguished_name
  > [req_distinguished_name]
  > commonName = Common Name
  > commonName_default = no.example.com
  > EOT
  $ openssl req -nodes -new -x509 -keyout /dev/null \
  >   -out dummycert.pem -days -1 -config cn.conf -subj '/CN=hg.example.com'

To verify the content of this certificate:

  $ openssl x509 -in dummycert.pem -noout -text
  Certificate:
      Data:
          Version: 1 (0x0)
          Serial Number: 15629337334278746470 (0xd8e68f7f6c6f7166)
      Signature Algorithm: sha1WithRSAEncryption
          Issuer: CN=hg.example.com
          Validity
              Not Before: Aug 30 08:45:59 2014 GMT
              Not After : Aug 29 08:45:59 2014 GMT
          Subject: CN=hg.example.com
          Subject Public Key Info:
              Public Key Algorithm: rsaEncryption
                  Public-Key: (512 bit)
                  Modulus:
                      00:9a:1f:d9:c9:21:a5:72:ad:00:2c:d2:e6:03:58:
                      19:aa:de:b5:1e:bb:b2:c0:fa:d1:93:a5:b2:ac:b2:
                      51:82:df:97:ec:e3:fd:14:59:44:7e:5d:ad:cc:77:
                      f3:aa:f9:8a:0a:d4:90:a0:f2:0d:58:e7:40:24:c7:
                      a4:05:81:60:29
                  Exponent: 65537 (0x10001)
      Signature Algorithm: sha1WithRSAEncryption
           17:d8:78:f4:b9:12:a8:9e:9a:22:5a:68:81:9b:94:1e:d8:a1:
           5d:e2:99:06:c8:a4:b5:52:03:94:37:1c:62:c3:72:d1:14:a1:
           f5:7c:54:7e:19:3e:5c:c2:f0:f2:30:65:62:f7:25:b5:25:dd:
           27:b5:9e:68:a7:50:45:e9:2e:31