Add support for client certificates for registries

This lets you specify custom client TLS certificates and CA root for a
specific registry hostname. Docker will then verify the registry
against the CA and present the client cert when talking to that
registry.  This allows the registry to verify that the client has a
proper key, indicating that the client is allowed to access the
images.

A custom cert is configured by creating a directory in
/etc/docker/certs.d with the same name as the registry hostname. Inside
this directory all *.crt files are added as CA Roots (if none exists,
the system default is used) and pair of files <filename>.key and
<filename>.cert indicate a custom certificate to present to the registry.

If there are multiple certificates each one will be tried in
alphabetical order, proceeding to the next if we get a 403 of 5xx
response.

So, an example setup would be:
/etc/docker/certs.d/
└── localhost
    ├── client.cert
    ├── client.key
    └── localhost.crt

A simple way to test this setup is to use an apache server to host a
registry. Just copy a registry tree into the apache root, here is an
example one containing the busybox image:
  http://people.gnome.org/~alexl/v1.tar.gz

Then add this conf file as /etc/httpd/conf.d/registry.conf:

 # This must be in the root context, otherwise it causes a re-negotiation
 # which is not supported by the tls implementation in go
 SSLVerifyClient optional_no_ca

 <Location /v1>
 Action cert-protected /cgi-bin/cert.cgi
 SetHandler cert-protected

 Header set x-docker-registry-version "0.6.2"
 SetEnvIf Host (.*) custom_host=$1
 Header set X-Docker-Endpoints "%{custom_host}e"
 </Location>

And this as /var/www/cgi-bin/cert.cgi

 #!/bin/bash
 if [ "$HTTPS" != "on" ]; then
     echo "Status: 403 Not using SSL"
     echo "x-docker-registry-version: 0.6.2"
     echo
     exit 0
 fi
 if [ "$SSL_CLIENT_VERIFY" == "NONE" ]; then
     echo "Status: 403 Client certificate invalid"
     echo "x-docker-registry-version: 0.6.2"
     echo
     exit 0
 fi
 echo "Content-length: $(stat --printf='%s' $PATH_TRANSLATED)"
 echo "x-docker-registry-version: 0.6.2"
 echo "X-Docker-Endpoints: $SERVER_NAME"
 echo "X-Docker-Size: 0"
 echo

 cat $PATH_TRANSLATED

This will return 403 for all accessed to /v1 unless *any* client cert
is presented. Obviously a real implementation would verify more details
about the certificate.

Example client certs can be generated with:

openssl genrsa -out client.key 1024
openssl req -new -x509 -text -key client.key -out client.cert

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
Revert "removed expect from mkimage-arch since it was not working"

This reverts commit 962e1186f9a0a43344e19dcf70bac159f0eafb4e.

Conflicts:
	contrib/mkimage-arch.sh

Docker-DCO-1.1-Signed-off-by: Zoltan Tombol <zoltan.tombol@gmail.com> (github: ztombol)
Fix expect script in mkimage-arch

Docker-DCO-1.1-Signed-off-by: Zoltan Tombol <zoltan.tombol@gmail.com> (github: ztombol)
Closes 6937. Allows setting of docker config dir.

Can now dynamically set the docker config directory through an
environment variable.

export DOCKER_CONFIG=/path/to/docker_config/

Default behavior remains the same, e.g. ~/.docker

Documentation for change added to the https.md docs.

Docker-DCO-1.1-Signed-off-by: James A. Kyle <james@jameskyle.org> (github: jameskyle)
Change HTTP code: 404 to a more user friendly Image Not found msg

Docker-DCO-1.1-Signed-off-by: William Henry <whenry@redhat.com> (github: ipbabble)
Added info re: image[:tag] to make docs consistent. Fixed a markdown issue.

Closes issue #6833

Docker-DCO-1.1-Signed-off-by: Fred Lifton <fred.lifton@docker.com> (github: fredlf)
Update libcontainer to be85764f109c3f0f62cd2a5c8be
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@docker.com> (github: crosbymichael)
Don't create pty slave in the daemon for native driver
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@docker.com> (github: crosbymichael)
Make tty term exec driver specific

lxc is special in that we cannot create the master outside of the
container without opening the slave because we have nothing to provide to the
cmd.  We have to open both then do the crazy setup on command right now instead of
passing the console path to lxc and telling it to open up that console.  we save a couple of
openfiles in the native driver because we can do this.
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@docker.com> (github: crosbymichael)
Fix cross compile non cgo and linux systems
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@docker.com> (github: crosbymichael)
Fix hack/make/ubuntu to install both docker.service and docker.socket

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Update usingdocker.md

Change --help example command to match output in docs
Bugfix: only use io.Copy in hijack if attaching both stdout and stderr

Add regression tests to ensure issue is fixed.

Docker-DCO-1.1-Signed-off-by: Matt Heon <mheon@redhat.com> (github: mheon)
integcli: add JSON utils for testing

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
integcli: fix map randomization failures

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
New screenshots and a few small edits.

Docker-DCO-1.1-Signed-off-by: Fred Lifton <fred.lifton@docker.com> (github: fredlf)
Merge pull request #7068 from fredlf/add_image-tag

Added info re: image[:tag] to make docs consistent.
Merge pull request #7082 from bdevloed/patch-1

Update usingdocker.md
Merge pull request #7083 from mheon/6983_bugfix

Fix Panic with -t and -a stderr
Merge pull request #7094 from fredlf/update_docker-hub

New screenshots and a few small edits.