Yearly Archives: 2018

Using environment secrets as build arguments in Google Cloud Build

December 27, 2018 » Geek

Google Cloud Build is a pretty nice tool for building your docker images continually, and cloud-build-local is pretty great for working on your images in dev. All around, a nice piece of kit to have in a Kubernetes shop.

The docs are pretty good, but one thing that I’ve recently dealt with did not show up in my searching; how to use an environment secret as a build argument to Docker. So here’s how I found to do it.

First, we will follow the encrypted secrets guide to get a secret wrapped up by KMS.

$ # Create a keyring and encryption key
$ gcloud kms keyrings create tinkering --location=global
$ gcloud  kms keys create cloud-build-demo \
  --keyring=tinkering \
  --purpose=encryption \
  --location=global
$ Now encrypt our secret string
$ echo -n "This is the super secret secret." | gcloud kms encrypt \
  --plaintext-file=- \
  --ciphertext-file=- \
  --location=global \
  --keyring=tinkering \
  --key=cloud-build-demo | base64
CiQATajs0GI7M6ZFM68Qu+GbJTfJ/d3tqqLcHz69RY1AaHkzV20SSQDt7E4V65imqbOnq8DvieiaglxjEztxWQCwrr2Mtu+xwT6tko6FHB+NNauyos6X1nnh5x217Cwx5QbX3h0YtjOJ15I4dnHDM+I=

Next, we will create a super simple Dockerfile to show how it is used.

FROM busybox
ARG THE_SECRET
RUN echo "::${THE_SECRET}::"

Last, we set up the cloudbuild.yaml. In the documentation demo files they use a shell entrypoint to access the environment variable.

# Note: You need a shell to resolve environment variables with $$
- name: 'gcr.io/cloud-builders/docker'
  entrypoint: 'bash'
  args: ['-c', 'docker login --username=[MY-USER] --password=$$PASSWORD']
  secretEnv: ['PASSWORD']

However, it would be nicer to not have to stringify our whole Docker build command.

Luckily, using --build-arg without a value falls through to the environment variable of the same name.

$ export HTTP_PROXY=http://10.20.30.2:1234
$ docker build --build-arg HTTP_PROXY .

So, we can just use it directly:

steps:
- id: docker
  name: 'gcr.io/cloud-builders/docker'
  args: ['build', '--build-arg', 'THE_SECRET', '.']
  secretEnv: ['THE_SECRET']
secrets:
- kmsKeyName: projects/hobbs-tinkering/locations/global/keyRings/tinkering/cryptoKeys/cloud-build-demo
  secretEnv:
    THE_SECRET: CiQATajs0GI7M6ZFM68Qu+GbJTfJ/d3tqqLcHz69RY1AaHkzV20SSQDt7E4V65imqbOnq8DvieiaglxjEztxWQCwrr2Mtu+xwT6tko6FHB+NNauyos6X1nnh5x217Cwx5QbX3h0YtjOJ15I4dnHDM+I=

Testing locally, it happily runs:

$ cloud-build-local --dryrun=false .
Using default tag: latest
latest: Pulling from cloud-builders/metadata
Digest: sha256:bcdb85e67ab9719c6441cb80fe9e8badc6d5ab0ab8bc73ee67adc0112233d20c
Status: Image is up to date for gcr.io/cloud-builders/metadata:latest
2018/12/23 13:18:29 Started spoofed metadata server
2018/12/23 13:18:29 Build id = localbuild_9cef1240-3a68-4ec3-a273-f49cd018316d
2018/12/23 13:18:29 status changed to "BUILD"
BUILD
Starting Step #0 - "docker"
Step #0 - "docker": Already have image (with digest): gcr.io/cloud-builders/docker
Step #0 - "docker": Sending build context to Docker daemon   5.12kB
Step #0 - "docker": Step 1/3 : FROM busybox
Step #0 - "docker":  ---> 59788edf1f3e
Step #0 - "docker": Step 2/3 : ARG THE_SECRET
Step #0 - "docker":  ---> Using cache
Step #0 - "docker":  ---> f289a756b157
Step #0 - "docker": Step 3/3 : RUN echo "::${THE_SECRET}::"
Step #0 - "docker":  ---> Running in 0e90f8f4f349
Step #0 - "docker": ::This is the super secret secret.::
Step #0 - "docker": Removing intermediate container 0e90f8f4f349
Step #0 - "docker":  ---> 75d19dee1d47
Step #0 - "docker": Successfully built 75d19dee1d47
Finished Step #0 - "docker"
2018/12/23 13:18:35 status changed to "DONE"
DONE

It is worth noting that using build args for secrets is not recommended. Anyone with the image can see what the argument passed in was.

$ docker history 75d19dee1d47
IMAGE               CREATED             CREATED BY                                      SIZE                COMMENT
75d19dee1d47        4 days ago          |1 THE_SECRET=This is the super secret secre…   0B
f289a756b157        4 days ago          /bin/sh -c #(nop)  ARG THE_SECRET               0B
59788edf1f3e        2 months ago        /bin/sh -c #(nop)  CMD ["sh"]                   0B
           2 months ago        /bin/sh -c #(nop) ADD file:63eebd629a5f7558c…   1.15MB

Docker 18.09, added build secrets for a better solution, but GCB is still running Docker 17.12, so we will have to wait for that update.

A gist of the code is available at: https://gist.github.com/jmhobbs/a572b47048eb42803bcb2102ac57a8df

Party Gopher!

June 13, 2018 » Geek

The Go slack has a cute little dancing Gopher that appears to have come from Egon Elbre. I love it!

Dancing Gopher

This little dancing Gopher made me think of Party Parrot, so I wanted to parrot-ize him. Normally I might just open up Gimp and start editing, but this is the Go Gopher, we can do better than that!

My plan was to use Go’s image packages to edit each frame and replace the blue with the correct parrot color for that frame by walking over the pixels in each frame.

Once I got into the package docs however, I realized that since gif’s are paletted, I can just tweak the palette on each frame and be done. Much simpler. Let’s get into then, shall we?

Colors!

First things first, I needed to declare the party parrot frame colors, and the light and dark blue that the dancing gopher uses. I grabbed the blues with Sip and I already had the parrot colors on hand. Sure, I could precompute these and declare, but let’s keep it interesting.

Note that I have a DarkParrotColors slice as well, this is for the corresponding dark blue replacements. I generate these with darken which I’ll show in a moment.

var (
	ParrotColors     []color.Color
	DarkParrotColors []color.Color
	LightGopherBlue  color.Color
	DarkGopherBlue   color.Color
)

func init() {
	var err error

	for _, s := range []string{
		"FF6B6B",
		"FF6BB5",
		"FF81FF",
		"FF81FF",
		"D081FF",
		"81ACFF",
		"81FFFF",
		"81FF81",
		"FFD081",
		"FF8181",
	} {
		c, err := hexToColor(s)
		if err != nil {
			log.Fatal(err)
		}
		ParrotColors = append(ParrotColors, c)
		DarkParrotColors = append(DarkParrotColors, darken(c))
	}

	LightGopherBlue, err = hexToColor("8BD0FF")
	if err != nil {
		log.Fatal(err)
	}
	DarkGopherBlue, err = hexToColor("82C2EE")
	if err != nil {
		log.Fatal(err)
	}
}

Also notable is the hexToColor which just unpacks an HTML hex RGB representation into a color.Color.

func hexToColor(hex string) (color.Color, error) {
	c := color.RGBA{0, 0, 0, 255}

	r, err := strconv.ParseInt(hex[0:2], 16, 16)
	if err != nil {
		return c, err
	}

	g, err := strconv.ParseInt(hex[2:4], 16, 16)
	if err != nil {
		return c, err
	}

	b, err := strconv.ParseInt(hex[4:6], 16, 16)
	if err != nil {
		return c, err
	}

	c.R = uint8(r)
	c.G = uint8(g)
	c.B = uint8(b)

	return c, nil
}

Here is the darken function, pretty simple.

func darken(c color.Color) color.Color {
	r, g, b, a := c.RGBA()
	r = r - 15
	g = g - 15
	b = b - 15
	return color.RGBA{uint8(r), uint8(g), uint8(b), uint8(a)}
}

Now I need to pull in the gif and decode it, all very boilerplate.

	// Open the dancing gopher gif
	f, err := os.Open("dancing-gopher.gif")
	if err != nil {
		log.Fatal(err)
	}
	defer f.Close()

	// Decode the gif so we can edit it
	gopher, err := gif.DecodeAll(f)
	if err != nil {
		log.Fatal(err)
	}

After that, I iterate over the frames and edit the palettes.

	for i, frame := range gopher.Image {
		lbi = frame.Palette.Index(LightGopherBlue)
		dbi = frame.Palette.Index(DarkGopherBlue)

		frame.Palette[lbi] = ParrotColors[i%len(ParrotColors)]
		frame.Palette[dbi] = DarkParrotColors[i%len(DarkParrotColors)]
	}

Lastly, more boilerplate to write it out to disk.

	o, _ := os.OpenFile("party-gopher.gif", os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
	defer o.Close()
	gif.EncodeAll(o, gopher)

Party Gopher

You can grab the code on Github, and thanks again to Egon Elbre for the excellent original gif!

A New GPG Key

May 30, 2018 » Geek

It’s been 12 years since I created my first GPG key and 11 since I’ve created the one I actually use. That is far too long, so I decided to create a new pair and deprecate the old. In 2013 I started this process, but I didn’t follow through and I’ve since lost access to those keys. I know where they are, but the machine died so I need to hook up it’s HDD and pull the keys out.

Regardless, it is time for new ones, and I did some reading to get a real plan for this. I would generate a new, strong key offline, with a subkey for each capability. The subkeys would go onto a smart card, in my case a Yubikey 4. The primary key material would go to offline backup to keep it safe.

Disclaimer

Nothing in this post is new or novel, but rather collected from many other posts. I’ve tried to link to any relevant posts below each section, and I encourage you to read these sources. Any mistakes I’ve made I would be glad if you send me an email (GPG encrypted of course ;) to point it out.

Yubikey Configuration

After I ordered my Yubikey, I had to configure it. The Yubikey docs expect a fair amount of knowledge before you start, but the steps are pretty simple when you understand it. Basically, it boils down to:

  1. Change the Admin PIN
  2. Change the PIN
  3. Set a Reset Code
  4. Fill in optional metadata

Plug in your card and proceed as follows:

$ gpg --card-edit

Reader ...........: Yubico Yubikey 4 OTP U2F CCID
Application ID ...: D2760001240102010006075857980000
Version ..........: 2.1
Manufacturer .....: Yubico
Serial number ....: 07------
Name of cardholder: [not set]
Language prefs ...: [not set]
Sex ..............: unspecified
URL of public key : [not set]
Login data .......: [not set
Signature PIN ....: not forced
Key attributes ...: rsa4096 rsa4096 rsa2048
Max. PIN lengths .: 127 127 127
PIN retry counter : 3 0 3
Signature counter : 0
Signature key ....: [none]
Encryption key....: [none]
Authentication key: [none]
General key info..: [none]

gpg/card> admin
Admin commands are allowed

gpg/card> passwd
gpg: OpenPGP card no. D2760001240102010006075857980000 detected

1 - change PIN
2 - unblock PIN
3 - change Admin PIN
4 - set the Reset Code
Q - quit

Your selection? 3
PIN changed.

1 - change PIN
2 - unblock PIN
3 - change Admin PIN
4 - set the Reset Code
Q - quit

Your selection? 1
PIN changed.

1 - change PIN
2 - unblock PIN
3 - change Admin PIN
4 - set the Reset Code
Q - quit

Your selection? 4
Reset Code set.

1 - change PIN
2 - unblock PIN
3 - change Admin PIN
4 - set the Reset Code
Q - quit

Your selection? Q


gpg/card> name
Cardholder's surname: Hobbs
Cardholder's given name: John

gpg/card> lang
Language preferences: en

gpg/card> url
URL to retrieve public key: http://static.velvetcache.org/John-Hobbs-Public-Key.asc

gpg/card> login
Login data (account name): [email protected]

gpg/card>

Reader ...........: Yubico Yubikey 4 OTP U2F CCID
Application ID ...: D2760001240102010006075857980000
Version ..........: 2.1
Manufacturer .....: Yubico
Serial number ....: 07------
Name of cardholder: John Hobbs
Language prefs ...: en
Sex ..............: unspecified
URL of public key : http://static.velvetcache.org/John-Hobbs-Public-Key.asc
Login data .......: [email protected]
Signature PIN ....: not forced
Key attributes ...: rsa4096 rsa4096 rsa2048
Max. PIN lengths .: 127 127 127
PIN retry counter : 3 3 3
Signature counter : 0
Signature key ....: [none]
Encryption key....: [none]
Authentication key: [none]
General key info..: [none]

gpg/card> quit
Links

Generating Keys

Next, I created my keys. Be sure you set up a clean environment for this, ideally a random directory in /tmp, better still on a ramfs of an offline, live CD machine. But that’s a bit drastic for my use case.

$ export GNUPGHOME="/tmp/$(pwgen 30 1)/gnupg"
$ echo $GNUPGHOME
/tmp/mah1zakioboo1Caipa3ORu5ielohga/gnupg
$ mkdir -p "$GNUPGHOME"
$ cd "$GNUPGHOME/.."
$ chmod 0700 gnupg
$ ls -l
total 0
drwx------  2 johnhobbs  wheel  64 May 30 14:23 gnupg

You’ll want a good base config file in there too.

$ cat < gnupg/gpg.conf
# Show long key IDs, not short: https://gwolf.org/node/4070
keyid-format 0xlong

# Display the calculated validity of user IDs during key listings
list-options show-uid-validity
verify-options show-uid-validity

# List keys with their fingerprints
with-fingerprint

# Default preferences used for creating new keys
default-preference-list SHA512 SHA384 SHA256 SHA224 AES256 AES192 AES CAST5 ZLIB BZIP2 ZIP Uncompressed

# Digest used to sign keys
cert-digest-algo SHA512

# Cipher to use for encrypting private keys
s2k-cipher-algo AES256

# Digest to use for mangling passphrases on private keys
s2k-digest-algo SHA512

# Refuse to run if GnuPG cannot get secure memory.
require-secmem
EOF

With the directory in place, I can create a primary key, option 4. 4096-bits is as strong as GPG allows right now, and I set it not to expire because I will be keeping offline and it should be ok to revoke manually if needed.

$ gpg --full-gen-key
gpg (GnuPG/MacGPG2) 2.2.3; Copyright (C) 2017 Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

gpg: keybox '/tmp/mah1zakioboo1Caipa3ORu5ielohga/gnupg/pubring.kbx' created
Please select what kind of key you want:
   (1) RSA and RSA (default)
   (2) DSA and Elgamal
   (3) DSA (sign only)
   (4) RSA (sign only)
Your selection? 4
RSA keys may be between 1024 and 4096 bits long.
What keysize do you want? (2048) 4096
Requested keysize is 4096 bits
Please specify how long the key should be valid.
         0 = key does not expire
        = key expires in n days
      w = key expires in n weeks
      m = key expires in n months
      y = key expires in n years
Key is valid for? (0) 0
Key does not expire at all
Is this correct? (y/N) y

GnuPG needs to construct a user ID to identify your key.

Real name: John Hobbs
Email address: [email protected]
Comment:
You selected this USER-ID:
    "John Hobbs "

Change (N)ame, (C)omment, (E)mail or (O)kay/(Q)uit? O
We need to generate a lot of random bytes. It is a good idea to perform
some other action (type on the keyboard, move the mouse, utilize the
disks) during the prime generation; this gives the random number
generator a better chance to gain enough entropy.
gpg: /tmp/mah1zakioboo1Caipa3ORu5ielohga/gnupg/trustdb.gpg: trustdb created
gpg: key 0xCF469E79A0A20E10 marked as ultimately trusted
gpg: directory '/tmp/mah1zakioboo1Caipa3ORu5ielohga/gnupg/openpgp-revocs.d' created
gpg: revocation certificate stored as '/tmp/mah1zakioboo1Caipa3ORu5ielohga/gnupg/openpgp-revocs.d/5A4B39AA4C644429718D6EAACF469E79A0A20E10.rev'
public and secret key created and signed.

Note that this key cannot be used for encryption.  You may want to use
the command "--edit-key" to generate a subkey for this purpose.
pub   rsa4096/0xCF469E79A0A20E10 2018-05-30 [SC]
      Key fingerprint = 5A4B 39AA 4C64 4429 718D  6EAA CF46 9E79 A0A2 0E10
uid                              John Hobbs 

$ gpg --list-secret-keys
gpg: checking the trustdb
gpg: marginals needed: 3  completes needed: 1  trust model: pgp
gpg: depth: 0  valid:   1  signed:   0  trust: 0-, 0q, 0n, 0m, 0f, 1u
/tmp/mah1zakioboo1Caipa3ORu5ielohga/gnupg/pubring.kbx
-----------------------------------------------------
sec   rsa4096/0xCF469E79A0A20E10 2018-05-30 [SC]
      Key fingerprint = 5A4B 39AA 4C64 4429 718D  6EAA CF46 9E79 A0A2 0E10
uid                   [ultimate] John Hobbs 

Now it’s time to create subkeys. There are four capabilities that a PGP key can have.

C is for Certify

Your primary key will have the capability of Certification. Certify is essentially the ability to sign other keys. A key with Certify can be “parent” to subkeys, create new subkeys, and edit existing ones. You also need this capability to sign another users public key.

S is for Sign

A key with the Sign capability can sign files and messages, allowing others to verify their integrity.

E is for Encrypt

A key with the Encrypt capability is used for encrypting files. Simple.

A is for Authenticate

An Authentication key is generally used for SSH authentication.


Generating the subkeys is a bit tedious, but so it goes.

$ gpg --edit-key 0xCF469E79A0A20E10
gpg (GnuPG/MacGPG2) 2.2.3; Copyright (C) 2017 Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Secret key is available.

sec  rsa4096/0xCF469E79A0A20E10
     created: 2018-05-30  expires: never       usage: SC
     trust: ultimate      validity: ultimate
[ultimate] (1). John Hobbs 

gpg> addkey
Please select what kind of key you want:
   (3) DSA (sign only)
   (4) RSA (sign only)
   (5) Elgamal (encrypt only)
   (6) RSA (encrypt only)
Your selection? 4
RSA keys may be between 1024 and 4096 bits long.
What keysize do you want? (2048) 4096
Requested keysize is 4096 bits
Please specify how long the key should be valid.
         0 = key does not expire
        = key expires in n days
      w = key expires in n weeks
      m = key expires in n months
      y = key expires in n years
Key is valid for? (0) 4y
Key expires at Sun May 29 14:16:18 2022 CDT
Is this correct? (y/N) y
Really create? (y/N) y
We need to generate a lot of random bytes. It is a good idea to perform
some other action (type on the keyboard, move the mouse, utilize the
disks) during the prime generation; this gives the random number
generator a better chance to gain enough entropy.

sec  rsa4096/0xCF469E79A0A20E10
     created: 2018-05-30  expires: never       usage: SC
     trust: ultimate      validity: ultimate
ssb  rsa4096/0xA93E031FD5AB0841
     created: 2018-05-30  expires: 2022-05-29  usage: S
[ultimate] (1). John Hobbs 

gpg> addkey
Please select what kind of key you want:
   (3) DSA (sign only)
   (4) RSA (sign only)
   (5) Elgamal (encrypt only)
   (6) RSA (encrypt only)
Your selection? 6
RSA keys may be between 1024 and 4096 bits long.
What keysize do you want? (2048) 4096
Requested keysize is 4096 bits
Please specify how long the key should be valid.
         0 = key does not expire
        = key expires in n days
      w = key expires in n weeks
      m = key expires in n months
      y = key expires in n years
Key is valid for? (0) 4y
Key expires at Sun May 29 14:16:48 2022 CDT
Is this correct? (y/N) y
Really create? (y/N) y
We need to generate a lot of random bytes. It is a good idea to perform
some other action (type on the keyboard, move the mouse, utilize the
disks) during the prime generation; this gives the random number
generator a better chance to gain enough entropy.

sec  rsa4096/0xCF469E79A0A20E10
     created: 2018-05-30  expires: never       usage: SC
     trust: ultimate      validity: ultimate
ssb  rsa4096/0xA93E031FD5AB0841
     created: 2018-05-30  expires: 2022-05-29  usage: S
ssb  rsa4096/0xC8A284D483920085
     created: 2018-05-30  expires: 2022-05-29  usage: E
[ultimate] (1). John Hobbs 

gpg> save

The authentication key requires E X P E R T M O D E. Git gud.

$ gpg --expert --edit-key 0xCF469E79A0A20E10
gpg (GnuPG/MacGPG2) 2.2.3; Copyright (C) 2017 Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Secret key is available.

sec  rsa4096/0xCF469E79A0A20E10
     created: 2018-05-30  expires: never       usage: SC
     trust: ultimate      validity: ultimate
ssb  rsa4096/0xA93E031FD5AB0841
     created: 2018-05-30  expires: 2022-05-29  usage: S
ssb  rsa4096/0xC8A284D483920085
     created: 2018-05-30  expires: 2022-05-29  usage: E
[ultimate] (1). John Hobbs 

gpg> addkey
Please select what kind of key you want:
   (3) DSA (sign only)
   (4) RSA (sign only)
   (5) Elgamal (encrypt only)
   (6) RSA (encrypt only)
   (7) DSA (set your own capabilities)
   (8) RSA (set your own capabilities)
  (10) ECC (sign only)
  (11) ECC (set your own capabilities)
  (12) ECC (encrypt only)
  (13) Existing key
Your selection? 8

Possible actions for a RSA key: Sign Encrypt Authenticate
Current allowed actions: Sign Encrypt

   (S) Toggle the sign capability
   (E) Toggle the encrypt capability
   (A) Toggle the authenticate capability
   (Q) Finished

Your selection? S

Possible actions for a RSA key: Sign Encrypt Authenticate
Current allowed actions: Encrypt

   (S) Toggle the sign capability
   (E) Toggle the encrypt capability
   (A) Toggle the authenticate capability
   (Q) Finished

Your selection? A

Possible actions for a RSA key: Sign Encrypt Authenticate
Current allowed actions: Encrypt Authenticate

   (S) Toggle the sign capability
   (E) Toggle the encrypt capability
   (A) Toggle the authenticate capability
   (Q) Finished

Your selection? E

Possible actions for a RSA key: Sign Encrypt Authenticate
Current allowed actions: Authenticate

   (S) Toggle the sign capability
   (E) Toggle the encrypt capability
   (A) Toggle the authenticate capability
   (Q) Finished

Your selection? Q
RSA keys may be between 1024 and 4096 bits long.
What keysize do you want? (2048) 4096
Requested keysize is 4096 bits
Please specify how long the key should be valid.
         0 = key does not expire
        = key expires in n days
      w = key expires in n weeks
      m = key expires in n months
      y = key expires in n years
Key is valid for? (0) 4y
Key expires at Sun May 29 14:20:03 2022 CDT
Is this correct? (y/N) y
Really create? (y/N) y
We need to generate a lot of random bytes. It is a good idea to perform
some other action (type on the keyboard, move the mouse, utilize the
disks) during the prime generation; this gives the random number
generator a better chance to gain enough entropy.

sec  rsa4096/0xCF469E79A0A20E10
     created: 2018-05-30  expires: never       usage: SC
     trust: ultimate      validity: ultimate
ssb  rsa4096/0xA93E031FD5AB0841
     created: 2018-05-30  expires: 2022-05-29  usage: S
ssb  rsa4096/0xC8A284D483920085
     created: 2018-05-30  expires: 2022-05-29  usage: E
ssb  rsa4096/0xED7858737F087831
     created: 2018-05-30  expires: 2022-05-29  usage: A
[ultimate] (1). John Hobbs 

gpg> save

That’s it! We’re in business.

Links
  1. https://spin.atomicobject.com/2013/11/24/secure-gpg-keys-guide/
  2. https://www.linode.com/docs/security/authentication/gpg-key-for-ssh-authentication/
  3. https://gist.github.com/abeluck/3383449
  4. https://alexcabal.com/creating-the-perfect-gpg-keypair/
  5. https://gist.github.com/graffen/37eaa2332ee7e584bfda

Backups

Before we do anything else, we need to back that thang up.

I’m choosing two methods: backup to a USB key that will live in a fire safe (who has a safety deposit box these days?), and a printed backup in case the USB key fails. Ideally these two articles would not be co-located.

First we export the keys and move them to the USB stick. The export-secret-subkeys output is less important than the export-secret-key output as it doesn’t contain a viable certification key, but would be useful as a “middle tier” of backup that wouldn’t expose your primary key to risk.

$ # Dump the public key, for giggles.
$ gpg --armor --export 0xCF469E79A0A20E10 > 0xCF469E79A0A20E10.public.asc
$ # This is the all the secret keys together.
$ gpg --armor --export-secret-key 0xCF469E79A0A20E10 > 0xCF469E79A0A20E10.master.asc
$ # This is just the subkeys.
$ gpg --armor --export-secret-subkeys 0xCF469E79A0A20E10 > 0xCF469E79A0A20E10.subkeys.asc
$ ls -l
total 64
-rw-r--r--   1 johnhobbs  wheel  14134 May 30 14:50 0xCF469E79A0A20E10.master.asc
-rw-r--r--   1 johnhobbs  wheel  14134 May 30 14:50 0xCF469E79A0A20E10.public.asc
-rw-r--r--   1 johnhobbs  wheel  12338 May 30 14:50 0xCF469E79A0A20E10.subkeys.asc
drwx------  13 johnhobbs  wheel    416 May 30 14:20 gnupg

Now, we could take these ascii armored keys and just print them, but that’s a lot of bytes to pray for OCR to recognize. Instead, we can use a piece of software called Paperkey which strips out everything but the most secret parts of the key and gives you something much shorter to type in.

 
$ gpg --export-secret-key | paperkey --output 0xCF469E79A0A20E10.master.paper
$ cat 0xCF469E79A0A20E10.master.paper
# Secret portions of key 5A4B39AA4C644429718D6EAACF469E79A0A20E10
# Base16 data extracted Wed May 30 14:53:56 2018
# Created with paperkey 1.5 by David Shaw
#
# File format:
# a) 1 octet:  Version of the paperkey format (currently 0).
# b) 1 octet:  OpenPGP key or subkey version (currently 4)
# c) n octets: Key fingerprint (20 octets for a version 4 key or subkey)
# d) 2 octets: 16-bit big endian length of the following secret data
# e) n octets: Secret data: a partial OpenPGP secret key or subkey packet as
#              specified in RFC 4880, starting with the string-to-key usage
#              octet and continuing until the end of the packet.
# Repeat fields b through e as needed to cover all subkeys.
#
# To recover a secret key without using the paperkey program, use the
# key fingerprint to match an existing public key packet with the
# corresponding secret data from the paper key.  Next, append this secret
# data to the public key packet.  Finally, switch the public key packet tag
# from 6 to 5 (14 to 7 for subkeys).  This will recreate the original secret
# key or secret subkey packet.  Repeat as needed for all public key or subkey
# packets in the public key.  All other packets (user IDs, signatures, etc.)
# may simply be copied from the public key.
#
# Each base16 line ends with a CRC-24 of that line.
# The entire block of data ends with a CRC-24 of the entire block of data.

  1: 00 04 5A 4E 39 AA 4C 64 44 29 71 8D 6E AA CF 46 9E 79 A0 A2 0E 10 745BFD
  ...
  248: 36 96 66 39 EE 0B36C4
  249: D3A56B

Still not fun to type it all in, but it’s better and this is a last ditch sort of thing anyway.

Recovery

Backups you don’t test aren’t backups, they are hopes and dreams. So let’s try recovering from our paperkey output!

$ mkdir recovery/
$ # Paperkey wants the public component to be raw.
$ gpg --dearmor 0xCF469E79A0A20E10.public.asc
$ # You can't specify output filename on dearmor so let's move it.
$ mv 0xCF469E79A0A20E10.public.asc.gpg recovery/
$ # Combine the public with the secret to get a GPG compatible keyring.
$ paperkey --pubring recovery/0xCF469E79A0A20E10.public.asc.gpg --secrets 0xCF469E79A0A20E10.master.paper --output recovery/0xCF469E79A0A20E10.master.gpg
$ # Check it out, without importing it.
$ gpg --import --import-options show-only recovery/0xCF469E79A0A20E10.master.gpg
sec   rsa4096/0xCF469E79A0A20E10 2018-05-30 [SC]
      Key fingerprint = 5A4B 39AA 4C64 4429 718D  6EAA CF46 9E79 A0A2 0E10
uid                              John Hobbs 
ssb   rsa4096/0xA93E031FD5AB0841 2018-05-30 [S] [expires: 2022-05-29]
ssb   rsa4096/0xC8A284D483920085 2018-05-30 [E] [expires: 2022-05-29]
ssb   rsa4096/0xED7858737F087831 2018-05-30 [A] [expires: 2022-05-29]

gpg: Total number processed: 1
gpg:       secret keys read: 1

Links
  1. http://www.jabberwocky.com/software/paperkey/

The certificate revoke you, secret key!

While not required, we can generate a revocation certificate while we still have the primary key on this machine.

$ gpg --output 0xCF469E79A0A20E10.revocation-certificate.asc --gen-revoke 0xCF469E79A0A20E10

sec  rsa4096/0xCF469E79A0A20E10 2018-05-30 John Hobbs 

Create a revocation certificate for this key? (y/N) y
Please select the reason for the revocation:
  0 = No reason specified
  1 = Key has been compromised
  2 = Key is superseded
  3 = Key is no longer used
  Q = Cancel
(Probably you want to select 1 here)
Your decision? 0
Enter an optional description; end it with an empty line:
>
Reason for revocation: No reason specified
(No description given)
Is this okay? (y/N) y
ASCII armored output forced.
Revocation certificate created.

Please move it to a medium which you can hide away; if Mallory gets
access to this certificate he can use it to make your key unusable.
It is smart to print this certificate and store it away, just in case
your media become unreadable.  But have some caution:  The print system of
your machine might store the data and make it available to others!

Throw that onto your backup drive too while you’re at it.

Links
  1. https://www.hackdiary.com/2004/01/18/revoking-a-gpg-key/

Sign!

Ok. Everything is generated, we have a good backup, we are ready to transition. To indicate that this key is your new key, you can sign it with your old one, then send it up to the keyservers in the sky (if you’re into that)

$ # --local-user lets us specify which key we want to sign with.
$ gpg --local-user 0x2580c0be34eb9490 --sign-key 0xCF469E79A0A20E10
$ gpg --list-sigs 0xCF469E79A0A20E10
pub   rsa4096/0xCF469E79A0A20E10 2018-05-30 [SC]
      Key fingerprint = 5A4B 39AA 4C64 4429 718D  6EAA CF46 9E79 A0A2 0E10
uid                   [ unknown] John Hobbs 
sig 3        0xCF469E79A0A20E10 2018-05-30  John Hobbs 
sig 3        0x2580C0BE34EB9490 2018-05-30  John Hobbs 
sub   rsa4096/0xC8A284D483920085 2018-05-30 [E] [expires: 2022-05-29]
sig          0xCF469E79A0A20E10 2018-05-30  John Hobbs 
sub   rsa2048/0xED7858737F087831 2018-05-30 [A] [expires: 2022-05-29]
sig          0xCF469E79A0A20E10 2018-05-30  John Hobbs 
sub   rsa4096/0xA93E031FD5AB0841 2018-05-30 [S] [expires: 2022-05-29]
sig          0xCF469E79A0A20E10 2018-05-30  John Hobbs 
$ # Send it all off to the keyservers!
$ gpg --send-keys 0xCF469E79A0A20E10
gpg: sending key 0xCF469E79A0A20E10 to hkps://hkps.pool.sks-keyservers.net

Links
  1. https://www.apache.org/dev/key-transition.html

To The Smart Card Robin!

I'm Batman

Moving the keys onto a smart card helps protect them. They won’t exist on your filesystem anymore, only on the card. That means they can’t be read out and stolen by a malicious process, but you can still use them by providing your smart card pin and key password.

Keep in mind, this is a one way trip. Make sure your backups are really, truly in place. We want to move our Signing, Encryption and Authentication keys onto the card. The Certification key we will only store offline, as mentioned before.

$ gpg --list-secret-keys
/tmp/mah1zakioboo1Caipa3ORu5ielohga/gnupg/pubring.kbx
-----------------------------------------------------
sec   rsa4096/0xCF469E79A0A20E10 2018-05-30 [SC]
      Key fingerprint = 5A4B 39AA 4C64 4429 718D  6EAA CF46 9E79 A0A2 0E10
uid                   [ultimate] John Hobbs 
ssb   rsa4096/0xA93E031FD5AB0841 2018-05-30 [S] [expires: 2022-05-29]
ssb   rsa4096/0xC8A284D483920085 2018-05-30 [E] [expires: 2022-05-29]
ssb   rsa4096/0xED7858737F087831 2018-05-30 [A] [expires: 2022-05-29]
$ gpg --edit-key 0xCF469E79A0A20E10
gpg (GnuPG/MacGPG2) 2.2.3; Copyright (C) 2017 Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Secret key is available.

sec  rsa4096/0xCF469E79A0A20E10
     created: 2018-05-30  expires: never       usage: SC
     trust: ultimate      validity: ultimate
ssb  rsa4096/0xA93E031FD5AB0841
     created: 2018-05-30  expires: 2022-05-29  usage: S
ssb  rsa4096/0xC8A284D483920085
     created: 2018-05-30  expires: 2022-05-29  usage: E
ssb  rsa4096/0xED7858737F087831
     created: 2018-05-30  expires: 2022-05-29  usage: A
[ultimate] (1). John Hobbs 

gpg> key 1

sec  rsa4096/0xCF469E79A0A20E10
     created: 2018-05-30  expires: never       usage: SC
     trust: ultimate      validity: ultimate
ssb* rsa4096/0xA93E031FD5AB0841
     created: 2018-05-30  expires: 2022-05-29  usage: S
ssb  rsa4096/0xC8A284D483920085
     created: 2018-05-30  expires: 2022-05-29  usage: E
ssb  rsa4096/0xED7858737F087831
     created: 2018-05-30  expires: 2022-05-29  usage: A
[ultimate] (1). John Hobbs 

gpg> keytocard
Please select where to store the key:
   (1) Signature key
   (3) Authentication key
Your selection? 1

sec  rsa4096/0xCF469E79A0A20E10
     created: 2018-05-30  expires: never       usage: SC
     trust: ultimate      validity: ultimate
ssb* rsa4096/0xA93E031FD5AB0841
     created: 2018-05-30  expires: 2022-05-29  usage: S
ssb  rsa4096/0xC8A284D483920085
     created: 2018-05-30  expires: 2022-05-29  usage: E
ssb  rsa4096/0xED7858737F087831
     created: 2018-05-30  expires: 2022-05-29  usage: A
[ultimate] (1). John Hobbs 

gpg> key 2

sec  rsa4096/0xCF469E79A0A20E10
     created: 2018-05-30  expires: never       usage: SC
     trust: ultimate      validity: ultimate
ssb* rsa4096/0xA93E031FD5AB0841
     created: 2018-05-30  expires: 2022-05-29  usage: S
ssb* rsa4096/0xC8A284D483920085
     created: 2018-05-30  expires: 2022-05-29  usage: E
ssb  rsa4096/0xED7858737F087831
     created: 2018-05-30  expires: 2022-05-29  usage: A
[ultimate] (1). John Hobbs 

gpg> key 1

sec  rsa4096/0xCF469E79A0A20E10
     created: 2018-05-30  expires: never       usage: SC
     trust: ultimate      validity: ultimate
ssb  rsa4096/0xA93E031FD5AB0841
     created: 2018-05-30  expires: 2022-05-29  usage: S
ssb* rsa4096/0xC8A284D483920085
     created: 2018-05-30  expires: 2022-05-29  usage: E
ssb  rsa4096/0xED7858737F087831
     created: 2018-05-30  expires: 2022-05-29  usage: A
[ultimate] (1). John Hobbs 

gpg> keytocard
Please select where to store the key:
   (2) Encryption key
Your selection? 2

sec  rsa4096/0xCF469E79A0A20E10
     created: 2018-05-30  expires: never       usage: SC
     trust: ultimate      validity: ultimate
ssb  rsa4096/0xA93E031FD5AB0841
     created: 2018-05-30  expires: 2022-05-29  usage: S
ssb* rsa4096/0xC8A284D483920085
     created: 2018-05-30  expires: 2022-05-29  usage: E
ssb  rsa4096/0xED7858737F087831
     created: 2018-05-30  expires: 2022-05-29  usage: A
[ultimate] (1). John Hobbs 

gpg> key 3

sec  rsa4096/0xCF469E79A0A20E10
     created: 2018-05-30  expires: never       usage: SC
     trust: ultimate      validity: ultimate
ssb  rsa4096/0xA93E031FD5AB0841
     created: 2018-05-30  expires: 2022-05-29  usage: S
ssb* rsa4096/0xC8A284D483920085
     created: 2018-05-30  expires: 2022-05-29  usage: E
ssb* rsa4096/0xED7858737F087831
     created: 2018-05-30  expires: 2022-05-29  usage: A
[ultimate] (1). John Hobbs 

gpg> key 2

sec  rsa4096/0xCF469E79A0A20E10
     created: 2018-05-30  expires: never       usage: SC
     trust: ultimate      validity: ultimate
ssb   rsa4096/0xA93E031FD5AB0841
     created: 2018-05-30  expires: 2022-05-29  usage: S
ssb  rsa4096/0xC8A284D483920085
     created: 2018-05-30  expires: 2022-05-29  usage: E
ssb* rsa4096/0xED7858737F087831
     created: 2018-05-30  expires: 2022-05-29  usage: A
[ultimate] (1). John Hobbs 

gpg> keytocard
Please select where to store the key:
   (3) Authentication key
Your selection? 3

sec  rsa4096/0xCF469E79A0A20E10
     created: 2018-05-30  expires: never       usage: SC
     trust: ultimate      validity: ultimate
ssb   rsa4096/0xA93E031FD5AB0841
     created: 2018-05-30  expires: 2022-05-29  usage: S
ssb  rsa4096/0xC8A284D483920085
     created: 2018-05-30  expires: 2022-05-29  usage: E
ssb* rsa4096/0xED7858737F087831
     created: 2018-05-30  expires: 2022-05-29  usage: A
[ultimate] (1). John Hobbs 

gpg> save

HOYB

Hold onto your butts.

This is it. The big moment. Take out that smart card, secure your backups, and let’s delete our primary key material.

$ gpg --delete-secret-key 0xCF469E79A0A20E10
gpg (GnuPG/MacGPG2) 2.2.3; Copyright (C) 2017 Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.


sec  rsa4096/0xCF469E79A0A20E10 2018-05-30 John Hobbs 

Delete this key from the keyring? (y/N) y
This is a secret key! - really delete? (y/N) y
$ gpg --list-secret-keys

Now you can have gpg create key stubs for all the keys on your smart card.

$ gpg --card-status
Reader ...........: Yubico Yubikey 4 OTP U2F CCID
Application ID ...: D2760001240102010006075857980000
Version ..........: 2.1
Manufacturer .....: Yubico
Serial number ....: 07------
Name of cardholder: John Hobbs
Language prefs ...: en
...
General key info..: sub  rsa4096/0xCF469E79A0A20E10 2018-05-30 John Hobbs 
sec#  rsa4096/0xCF469E79A0A20E10  created: 2018-05-30  expires: never
ssb>  rsa4096/0xA93E031FD5AB0841  created: 2018-05-30  expires: 2022-05-29
                                  card-no: 0006 07------
ssb>  rsa2048/0xC8A284D483920085  created: 2018-05-30  expires: 2022-05-29
                                  card-no: 0006 07------
ssb>  rsa4096/0xED7858737F087831  created: 2018-05-30  expires: 2022-05-29
                                  card-no: 0006 07------

Now when we list keys, we see that our primary key has a # next to it, showing we don’t have access to that secret key. The subkeys have a > next to them showing they are stubs for the keys on the smart card. Success!

$ gpg --list-secret-keys
/tmp/mah1zakioboo1Caipa3ORu5ielohga/gnupg/pubring.kbx
-----------------------------------------------------
sec#   rsa4096/0xCF469E79A0A20E10 2018-05-30 [SC]
      Key fingerprint = 5A4B 39AA 4C64 4429 718D  6EAA CF46 9E79 A0A2 0E10
uid                   [ultimate] John Hobbs 
ssb>  rsa4096/0xA93E031FD5AB0841 2018-05-30 [S] [expires: 2022-05-29]
ssb>  rsa4096/0xC8A284D483920085 2018-05-30 [E] [expires: 2022-05-29]
ssb>  rsa4096/0xED7858737F087831 2018-05-30 [A] [expires: 2022-05-29]

Fin!

That’s it. There is, of course, more to do, like setting up git signing, SSH access, etc. But the new keypair is created, and it’s on the Yubikey, so that’s all for now.


Update: Git Signing

Turns out git signing is a cinch. Just throw a couple items into your git config and it’s automatic and transparent.

[user]
	signingKey = 0xF79C72E6EDC70E38
[commit]
	gpgSign = true
[log]
	showSignature = true
[merge]
	verifySignatures = true

user.signingKey

Tells git which key to use for signing, unset it just uses the default key.

commit.gpgSign

Makes it sign all commits by default, instead of passing -S to every git commit.

log.showSignature

By default, git won’t show you if a commit is GPG signed. You can see it with gpg log --show-signature, or you can set it as default with this config option.

It makes signed commits much chunkier, so be aware of the reduced screen real estate.

commit 6f02c4df4fac400841bf3970c1022c7358298333 (HEAD -> gpg-demo)
gpg: Signature made Wed Jun  6 11:52:40 2018 CDT
gpg:                using RSA key 44DC4F5A950F24A65D3F305801FC8AE9E5070C1D
gpg: Good signature from "John Hobbs " [ultimate]
Primary key fingerprint: 5616 12FF A10D 9D7A 7FFB  75F4 F79C 72E6 EDC7 0E38
     Subkey fingerprint: 44DC 4F5A 950F 24A6 5D3F  3058 01FC 8AE9 E507 0C1D
Author: John Hobbs 
Date:   Wed Jun 6 11:49:33 2018 -0500

merge.verifySignatures

This is the only one I am not setting by default. If you have it enabled, all merges that include unsigned commits will be rejected. This really only works if everyone in your organization is signing all their commits.

Links
  1. https://git-scm.com/book/en/v2/Git-Tools-Signing-Your-Work
  2. https://git-scm.com/docs/git-config

Update: One-Touch Actions

By default, with the smart card in, GPG will happily sign and decrypt things after you enter your PIN the first time, with no further interaction from you. The Yubikey offers a mode where these actions require a touch on the key to complete, which I like because it makes the action more explicit without requiring me to remove the key between operations.

To enable this, you need a special script, `yubitouch.sh`. To make it work with my GPG Tools install, I had to hard code the path to `gpg-connect-agent` (`/usr/local/MacGPG2/bin/gpg-connect-agent`) and my admin PIN, since pinentry wasn’t working and I didn’t want it in my bash history.

$ ./yubitouch.sh sig on
All done!
$ ./yubitouch.sh aut on
All done!
$ ./yubitouch.sh dec on
All done!

Now, when GPG needs to sign something, my Yubikey flashes at me until I touch it and give my permission. Neat.

Links
  1. https://developers.yubico.com/PGP/Card_edit.html
  2. https://github.com/a-dma/yubitouch
Tags: , ,

Chicken Cam: Incubator Edition

March 4, 2018 » Geek, Life

It’s been over a year since we’ve had chickens and we’ve missed them, so this Christmas we got Lizzy and Charlotte an incubator so that we could try hatching some this spring.

When we went to purchase eggs, we found that you could most easily get them 10 at a time from the hatchery we have used in the past, Murray McMurray. Since the incubator we got the girls could only hold seven, we would need something for the other three. Some searching found that you could use a styrofoam cooler and a lamp to create a makeshift incubator, so I planned on that.

Once I had a plan to create an incubator, I knew I would have to overcomplicate things. Four years ago I built a webcam for our chicks so I figured I would do that this time too. Also, just setting a lamp and thermometer in and hoping for the best seemed like a potential waste of good eggs, so I wanted to monitor the temperature and humidity, and regulate them.

My initial design was a Raspberry Pi connected to a cheap DHT11 temperature and humidity sensor, controlling a relay that could turn the light on and off. All of it would be hooked up through a PID controller to keep the temperatures right where we want them. Eventually, I added a thermocouple with a MAX6675 for more accurate temperature readings.

Raspberry Pi, Relay and a mess of wires.

The server side would be designed similarly to the previous chicken cam, except written in Go. The stats would be tracked in InfluxDB and Grafana would be used for viewing them.

After I got all the parts I did a little testing, then soldered things up and tested it to see how it ran.

Initially I wrote everything in Go, but the DHT11 reading was very spotty. Sometimes it would respond once every few seconds, and sometimes it would go a minute or more failing to read. I wired on a second DHT11 and tried reading from both, but I didn’t get that much better performance.

Eventually I tried them from the Adafruit Python library and had much better luck, so I decided to just read those from Python and send them to my main Go application for consumption. I still have trouble with the DHT11’s, but I suspect it’s my fault more than the sensors fault.

My next issue was that it was extremely jittery, the readings would vary by degrees one second to another, so I collected readings in batches of 5 seconds then averaged them. That smoothed it out enough that graphs looked reasonable.

On. Off. On. Off. On. Off.

Temperature was now well regulated, but the air wasn’t humid enough. I switched to a sponge and found I could manage it much easier that way. I briefly tried a 40W bulb thinking I could spend more time with the lamp off, but temperatures still plunged at the same rate when the light was off, so I mostly just created quicker cycles.

After putting the 25W bulb back in, I still wanted a longer, smoother cycle, so I wrapped up a brick (for cleanliness) and stuck that in there. That got me longer cycles with better recovery at the bottom, it didn’t get too cold before the lamp came back on. Some slight improvements to the seal of my lid helped as well. I had trouble with condensation and too much humidity, but some vent holes and better water management took care of that.

Before the brick.

After the brick.

For the server side, I mostly duplicated the code from the previous Chicken cam, but in Go. Then I used the InfluxDB library to get the most recent temperature and humidity readings for display.

At this point, I felt ready for the eggs, which was good because they had arrived! We placed them in the incubator and we’re just waiting now. On day 8 we candled them with a homebuilt lamp i.e. a cardboard box with a hole cut in it.

Candling

Things seem to be progressing well so far, so here’s hoping something hatches!