Error: Unknown S2K function - Issue caused by exported to card gpg keys

[gaoyichuan]

I have my PGP key moved to my yubikey. However I have the backup of my secret key.

When I use that key to get the airdrop, hs-airdrop gave an error:

Error: Unknown S2K function.
    at S2K.read (/home/gaoyichuan/workspace/hs-airdrop/node_modules/bcrypto/lib/pgp.js:1557:15)
    at CipherParams.read (/home/gaoyichuan/workspace/hs-airdrop/node_modules/bcrypto/lib/pgp.js:1363:18)
    at PGPPrivateKey.read (/home/gaoyichuan/workspace/hs-airdrop/node_modules/bcrypto/lib/pgp.js:1126:17)
    at Function.read (/home/gaoyichuan/workspace/hs-airdrop/node_modules/bufio/lib/struct.js:139:23)
    at PGPPacket.read (/home/gaoyichuan/workspace/hs-airdrop/node_modules/bcrypto/lib/pgp.js:439:35)
    at Function.read (/home/gaoyichuan/workspace/hs-airdrop/node_modules/bufio/lib/struct.js:139:23)
    at PGPMessage.read (/home/gaoyichuan/workspace/hs-airdrop/node_modules/bcrypto/lib/pgp.js:278:29)
    at PGPMessage.decode (/home/gaoyichuan/workspace/hs-airdrop/node_modules/bufio/lib/struct.js:91:10)
    at Function.decode (/home/gaoyichuan/workspace/hs-airdrop/node_modules/bufio/lib/struct.js:143:23)
    at readKey (/home/gaoyichuan/workspace/hs-airdrop/bin/hs-airdrop:529:30)

After some quick search, I use cat secring.gpg | gpg --list-packets | grep S2K to check my key info, it gave:

        iter+salt S2K, algo: 7, SHA1 protection, hash: 2, salt: D658CFAB39FED1A0
        iter+salt S2K, algo: 7, SHA1 protection, hash: 2, salt: 97D1A2FFC1F66F34
        gnu-divert-to-card S2K, algo: 0, simple checksum, hash: 0
        gnu-divert-to-card S2K, algo: 0, simple checksum, hash: 0
        gnu-divert-to-card S2K, algo: 0, simple checksum, hash: 0
        gnu-divert-to-card S2K, algo: 0, simple checksum, hash: 0
        iter+salt S2K, algo: 7, SHA1 protection, hash: 2, salt: AE573B264082AC56

And after patching the code, I found out the S2K algo number is 101

Any help please?

[gaoyichuan]

I have figure it out! For somebody who has the same issue:

1. BACKUP YOUR SECRET KEY
2. Use gpg --edit-key command, add a new subkey to your main key, and set the usage to 'Sign'
3. Use delkey in key editor to remove all your subkeys which are in your smartcard
4. Export your secret key again, and get the airdrop

I believe this is a bug in this tool, so some fix is welcomed!

[pinheadmz]

Thank you @gaoyichuan !

I'm going to close this issue for now, and change the title so future users with the same issue can find it easily.

[pinheadmz]

Sorry @gaoyichuan - are you saying there is a bug here? Are we using the wrong algo number for something?

[shankerwangmiao]

@pinheadmz For those who have one or more of their subkeys exported to smart cards, those subkeys will have a S2K algo number of 101, and at https://github.com/bcoin-org/bcrypto/blob/76266c9e3b8119f99eb5d69a196e9163de5c332d/lib/pgp.js#L1504 getSize() will fail since 101 falls out of those three cases.

[shankerwangmiao]

My suggestion is to skip that pgp packet when it cannot be processed, at https://github.com/bcoin-org/bcrypto/blob/76266c9e3b8119f99eb5d69a196e9163de5c332d/lib/pgp.js#L277

[pinheadmz]

Ah ok thanks. Gonna ping @chjj here to see if this is a viable solution.

[chjj]

I'd prefer not to skip it (I think that may break other things). I'm trying to find some information on this now. It looks like 101 a GNU extension for key derivation. I'll try to push a fix soon.

[metaspartan]

I have figure it out! For somebody who has the same issue:

1. BACKUP YOUR SECRET KEY
2. Use gpg --edit-key command, add a new subkey to your main key, and set the usage to 'Sign'
3. Use delkey in key editor to remove all your subkeys which are in your smartcard
4. Export your secret key again, and get the airdrop

I believe this is a bug in this tool, so some fix is welcomed!

I still get the S2K error even after removing all subkeys, creating a new DSA Sign subkey and then re-exporting the secret key, still gives a "Unknown S2K function" error.

[chjj]

The current master branch of bcrypto has the fix, but I unfortunately don't have a test vector. I might have to dig around the gnupg repo a bit.

[metaspartan]

@chjj I updated to your latest bcrypto code, it does get rid of the S2K function error, but now I am getting this error:

Error: Unknown cipher type.