Docker 启动监听端口后，使用的是 http，可以远程来管理 Docker 主机。
这样的场景存在弊端，API 层面是没有提供用户验证、Token 之类身份验证功能，任何人都可以通过地址加端口来控制 Docker 主机，为了避免这样的情况发生，Docker 官方也支持 https 方式，不过需要我们自己来生成证书。
通过 OpenSSL 命令来生成 CA 证书、服务器私钥、客户端证书、签名，openssl 命令比较复杂，我用脚本直接生成：
# cat certgen.sh
set -ex
[ -e certs ] || mkdir certs
cd certs
echo "Creating ca keys..."
echo 01 > ca.srl
openssl genrsa -des3 -out ca-key.pem
openssl rsa -in ca-key.pem -out ca-key.pem
openssl req -subj "/CN=$(hostname -f)/" -new -x509 -days 365 -key ca-key.pem -out ca.pem
echo "Creating server keys..."
openssl genrsa -des3 -out server-key.pem
openssl rsa -in server-key.pem -out server-key.pem
openssl req -subj "/CN=$(hostname -f)/" -new -key server-key.pem -out server.csr
openssl x509 -req -days 365 -in server.csr -CA ca.pem -CAkey ca-key.pem -out server-cert.pem
echo "Creating client keys..."
openssl genrsa -des3 -out key.pem
openssl rsa -in key.pem -out key.pem
openssl req -subj '/CN=*/' -new -key key.pem -out client.csr
echo extendedKeyUsage = clientAuth > extfile.cnf
openssl x509 -req -days 365 -in client.csr -CA ca.pem -CAkey ca-key.pem -out cert.pem -extfile extfile.cnf
需要注意，在执行脚本之前，确保你的主机名符合 FQDN 并能正常解析，不推荐修改脚本内容 $(hostname -f) 为 IP 地址，无需修改脚本，在脚本执行过程中会反复需要输入密码，统一输入一个密码就 ok：
sh certgen.sh
执行完后，会在当前目录下生成一个 certs 目录，里面有生成的所有的证书文件。
为了避免混淆，现在拷贝 CA 和服务器私钥到其它目录：
mkdir -p /etc/docker/certs
cd certs/
cp ca.pem server-cert.pem server-key.pem /etc/docker/certs/
服务器私钥有了，我们也知道在哪里，现在只需要让 Docker 知道：
vim /etc/default/docker
DOCKER_OPTS='-H unix:///var/run/docker.sock -H docker01.thstack.com:6732 --tlsverify --tlscacert=/etc/docker/certs/ca.pem --tlscert=/etc/docker/certs/server-cert.pem --tlskey=/etc/docker/certs/server-key.pem'
重启 docker 服务：
service docker restart
添加 DOCKER_HOST 环境变量，地址为 Docker 主机的主机名，同样如果设置 IP 地址会有问题：
# vim /etc/profile
export DOCKER_HOST=tcp://docker01.thstack.com:6732
# source /etc/profile
现在 Docker 已经开启了 https 认证，在命令行里敲 docker 命令会报错，需要在每个 docker 命令加 –tlsverify 参数，docker 命令作为一个客户端工具来操作 Docker 主机同样依赖客户端证书：
root@docker01:~/certs# docker info
2014/09/14 16:19:26 Get http://docker01.thstack.com:6732/v1.14/info: malformed HTTP response "x15x03x01x00x02x02"
root@docker01:~# docker --tlsverify images
2014/09/14 16:25:53 Couldn't read ca cert /root/.docker/ca.pem: open /root/.docker/ca.pem: no such file or directory
从 docker –tlsverify images 结果输出中了解到，加了 –tlsverify 参数后，就会默认去 ~/.docker 文件中找客户端证书，现在为 docker 客户端命令添加证书：
mkdir ~/.docker
cd certs/
cp ca.pem cert.pem key.pem ~/.docker
再次尝试执行命令：
root@docker01:~# docker ps
2014/09/14 16:28:42 Get http://docker01.thstack.com:6732/v1.14/containers/json: malformed HTTP response "x15x03x01x00x02x02"
root@docker01:~# docker --tlsverify images
REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE
ubuntu 14.04.1 826544226fdc 9 days ago 194.2 MB
ubuntu 14.04 826544226fdc 9 days ago 194.2 MB
ubuntu trusty 826544226fdc 9 days ago 194.2 MB
ubuntu latest 826544226fdc 9 days ago 194.2 MB
ubuntu 14.10 245ce11c1f25 9 days ago 202.5 MB
ubuntu utopic 245ce11c1f25 9 days ago 202.5 MB
ubuntu precise c17f3f519388 9 days ago 106.7 MB
ubuntu 12.04.5 c17f3f519388 9 days ago 106.7 MB
ubuntu 12.04 c17f3f519388 9 days ago 106.7 MB
ubuntu 12.10 c5881f11ded9 12 weeks ago 172.2 MB
ubuntu quantal c5881f11ded9 12 weeks ago 172.2 MB
ubuntu 13.04 463ff6be4238 12 weeks ago 169.4 MB
ubuntu raring 463ff6be4238 12 weeks ago 169.4 MB
ubuntu 13.10 195eb90b5349 12 weeks ago 184.7 MB
ubuntu saucy 195eb90b5349 12 weeks ago 184.7 MB
ubuntu lucid 3db9c44f4520 4 months ago 183 MB
ubuntu 10.04 3db9c44f4520 4 months ago 183 MB
只要开启 https 认证后，docker 命令就必须加 –tlsverify 参数。
上面所有的操作都是在 Docker 主机上操作，找另外一台机器来验证 https 是否生效：
root@ubuntu:~# curl -v -s https://docker01.thstack.com:6732/info
* About to connect() to docker01.thstack.com port 6732 (#0)
* Trying 192.168.3.23... connected
* successfully set certificate verify locations:
* CAfile: none
CApath: /etc/ssl/certs
* SSLv3, TLS handshake, Client hello (1):
* SSLv3, TLS handshake, Server hello (2):
* SSLv3, TLS handshake, CERT (11):
* SSLv3, TLS alert, Server hello (2):
* SSL certificate problem, verify that the CA cert is OK. Details:
error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed
* Closing connection #0
上面提示，证书验证失败，在 Docker 主机上 scp 客户端证书到这台机器上：
root@docker01:~# cd certs/
root@docker01:~/certs# scp ca.pem cert.pem key.pem root@ubuntu:/tmp
指明证书位置来验证，可以看到验证过程和结果：
root@ubuntu:~# curl -v -s -k --key /tmp/key.pem --cert /tmp/cert.pem https://docker01.thstack.com:6732/info
* About to connect() to docker01.thstack.com port 6732 (#0)
* Trying 192.168.3.23... connected
* successfully set certificate verify locations:
* CAfile: none
CApath: /etc/ssl/certs
* SSLv3, TLS handshake, Client hello (1):
* SSLv3, TLS handshake, Server hello (2):
* SSLv3, TLS handshake, CERT (11):
* SSLv3, TLS handshake, Server key exchange (12):
* SSLv3, TLS handshake, Request CERT (13):
* SSLv3, TLS handshake, Server finished (14):
* SSLv3, TLS handshake, CERT (11):
* SSLv3, TLS handshake, Client key exchange (16):
* SSLv3, TLS handshake, CERT verify (15):
* SSLv3, TLS change cipher, Client hello (1):
* SSLv3, TLS handshake, Finished (20):
* SSLv3, TLS change cipher, Client hello (1):
* SSLv3, TLS handshake, Finished (20):
* SSL connection using ECDHE-RSA-AES256-SHA
* Server certificate:
* subject: CN=docker01.thstack.com
* start date: 2014-09-14 03:27:16 GMT
* expire date: 2015-09-14 03:27:16 GMT
* common name: docker01.thstack.com (matched)
* issuer: CN=docker01.thstack.com
* SSL certificate verify result: self signed certificate (18), continuing anyway.
> GET /info HTTP/1.1
> User-Agent: curl/7.22.0 (x86_64-pc-linux-gnu) libcurl/7.22.0 OpenSSL/1.0.1 zlib/1.2.3.4 libidn/1.23 librtmp/2.3
> Host: docker01.thstack.com:6732
> Accept: */*
>
< HTTP/1.1 200 OK
< Content-Type: application/json
< Job-Name: info
< Date: Sun, 14 Sep 2014 08:43:26 GMT
< Content-Length: 417
<
{"Containers":1,"Debug":0,"Driver":"aufs","DriverStatus":[["Root Dir","/var/lib/docker/aufs"],["Dirs","36"]],"ExecutionDriver":"native-0.2","IPv4Forwarding":1,"Images":34,"IndexServerAddress":"https://index.docker.io/v1/","InitPath":"/usr/bin/docker","InitSha1":"","KernelVersion":"3.13.0-24-generic","MemoryLimit":1,"NEventsListener":0,"NFd":11,"NGoroutines":11,"OperatingSystem":"Ubuntu 14.04.1 LTS","SwapLimit":0}
* Connection #0 to host docker01.thstack.com left intact
* Closing connection #0
* SSLv3, TLS alert, Client hello (1):
也可以在其它机器上安装 lxc-docker，来用 docker 命令远程管理 Docker 主机，同样设置环境变量，添加证书。
如果在配置过程中出错，查看 /var/log/upstart/docker.log 日志，或重新生成证书