docs(README): update instructions

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Felix Schröter 2024-03-27 17:45:12 +01:00
parent 3c97a34ec4
commit b2bce8e5a7
Signed by: felschr
GPG key ID: 671E39E6744C807D

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@ -1,11 +1,8 @@
1. I have a GPG keypair in the same format as the one provided in `test-key.asc`. It is `ed25519`.
2. That key was used to encrypt a file with [age encryption](https://github.com/FiloSottile/age) as shown below
3. I want to decrypt that file, but only have a GPG secret key, as I couldn't
find out how to derive a SSH or age key from it.
# gpg2age
**GOAL**: Derive an age key from the provided GPG key that decrypt the file as
shown below. A SSH key is also enough, since it can be used with `ssh-to-age` to
derive the age key.
Derive private ed25519 SSH key from private PGP key.
GPG itself only supports exporting _public_ SSH keys and other tools don't work for ed25519 keys.
##### Notes:
@ -13,60 +10,39 @@ derive the age key.
- Work on `gnupg` was started for this feature, but never finished see this
issue and commit: https://dev.gnupg.org/T6647
## Example
## Instructions
Example key provided in `test-key.asc` to be imported. Use `--homedir` with
`gpg` to set a temporary `.gnupg` directory
First you need to export your PGP key from GPG:
```sh
gpg --homedir ./gnupg --import test-key.asc impure ❄ ssh-to-age age
gpg: WARNING: unsafe permissions on homedir '/home/pinpox/code/github.com/pinpox/gpg2age/./gnupg'
gpg: key 76188CF30717B54E: public key "test (test) <test@test.com>" imported
gpg: key 76188CF30717B54E: secret key imported
gpg: Total number processed: 1
gpg: imported: 1
gpg: secret keys read: 1
gpg: secret keys imported: 1
gpg --homedir ./gnupg_testkey/ -K
/home/pinpox/code/github.com/pinpox/gpg2age/./gnupg_testkey/pubring.kbx
-----------------------------------------------------------------------
sec ed25519 2024-03-25 [C]
9FE4D484B69DB9F5C7AA208E76188CF30717B54E
uid [ultimate] test (test) <test@test.com>
ssb ed25519 2024-03-25 [S]
ssb cv25519 2024-03-25 [E]
ssb ed25519 2024-03-25 [A]
gpg2 --export-secret-keys --armor test@test.test >priv-gpg
```
### Get age key and encrypt test file
Then identify the public SSH key that was used to encrypt your secret.
You can search for your GitHub username in: https://fluence-dao.s3.eu-west-1.amazonaws.com/metadata.json
If you have multiple subkeys, usually it is the authenticate key highlighted with `[A]` in the output of:
```sh
gpg --homedir ./gnupg --export-ssh-key 9FE4D484B69DB9F5C7AA208E76188CF30717B54E
ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAICYvKXGcG4a19tTT0Rycbn+D0r/YlKltLJ9dY2gR/Fjx openpgp:0x47C9F3FF
gpg --list-secret-keys --with-keygrip
```
### Derive private SSH key
```sh
gpg --homedir ./gnupg --export-ssh-key 9FE4D484B69DB9F5C7AA208E76188CF30717B54E | ssh-to-age impure ❄ ssh-to-age
age18s8m9hvlrwvltgys4lafyyqe356ntc7e06t4kd2nccqm5amsaa2s878mju # saved as age-public-key
go run main.go
```
It'll ask you for the path to your private PGP key, followed by choosing the key/subkey and if your PGP key is encrypted it'll ask for the passphrase.
In the output, verify that the public SSH key printed matches the one in `metadata.json`.
If it matches, the last part of the output it will print the matching private SSH key.
You can save the key to a file and use how you want.
### Example: Decrypt age files
If you want to decrypt a file that was encryptd by `age` with your public SSH key, you can just use `age` as normal to decrypt the file using the SSH private key that we've got in the previous step:
```sh
age --encrypt -R age-public-key testfile.txt > testfile.txt.age
```
### Get secret age key
```sh
go run main.go impure ❄ ssh-to-age age
AGE-SECRET-KEY-165W948VSG5QEM0RPEUX8T3K4YXJT2WF83C2GXQH8Q3Q0ZHCTH44SSV0H34 # saved as age-secret-key
```
### Try to decrypt
```sh
age --decrypt --identity age-secret-key --output decrypted testfile.txt.age impure ❄ ssh-to-age age
age: error: no identity matched any of the recipients
age: report unexpected or unhelpful errors at https://filippo.io/age/report
```
FAIL :(
age --decrypt --identity ./ssh-secret-key --output decrypted ./testfile.txt.age
```