Cannot decrypt GnuPG message with "partial continue" structure

[kaie]

I'm trying to decrypt a message with the command line tool, using the decrypt-pka command. It fails inside Message::meaningful. In Message::match p->get_tag() returns 254.

The message was sent using GnuPG. I've built with gpg-debug to enable compatibility.

"OpenPGP show" reports:

Old: Public-Key Encrypted Session Key (Tag 1)
Version: 3
KeyID: ...
Public Key Algorithm: RSA (Encrypt or Sign) (pka 1)
RSA me mod n (3072 bits): ...
Old: Public-Key Encrypted Session Key (Tag 1)
Version: 3
KeyID: ...
Public Key Algorithm: RSA (Encrypt or Sign) (pka 1)
RSA me mod n (4090 bits): ...
New: Symmetrically (Conventional) Encrypted Data (Tag 9) (partial start)
Encrypted Data (2048 octets): ...
Old: (partial end)
...

"pgpdump" reports:

Old: Public-Key Encrypted Session Key Packet(tag 1)(396 bytes)
New version(3)
Key ID - ...
Pub alg - RSA Encrypt or Sign(pub 1)
RSA m^e mod n(3072 bits) - ...
-> m = sym alg(1 byte) + checksum(2 bytes) + PKCS-1 block type 02
Old: Public-Key Encrypted Session Key Packet(tag 1)(524 bytes)
New version(3)
Key ID - ...
Pub alg - RSA Encrypt or Sign(pub 1)
RSA m^e mod n(4090 bits) - ...
-> m = sym alg(1 byte) + checksum(2 bytes) + PKCS-1 block type 02
New: Symmetrically Encrypted Data Packet(tag 9)(2048 bytes) partial start
Encrypted data [sym alg is specified in pub-key encrypted session key]
New: (1024 bytes) partial continue
New: (475 bytes) partial end

[calccrypto]

Can you please post the message, so that I can trace what it is doing in the code?

[calccrypto]

Please pull to c21916a master and give it a try

[kaie]

encrypted.txt

This is the encrypted file, I hope it is helpful.

[calccrypto]

Please give the latest master another try.

[calccrypto]

@kaie Have the most recent updates fixed this?

[kaie]

Hello Jason, sorry for the delay. It's not yet working for me, maybe I'm doing something wrong. I get an error:

./cli/OpenPGP decrypt-pka testmail-0227.private passphrase enc.pgp
terminate called after throwing an instance of 'std::runtime_error'
what(): Error: Data does not form a meaningful PGP Key
Aborted (core dumped)

The key pair was generated using:
./cli/OpenPGP generate-keypair --phash SHA256 --pkeysize 3072 --psig SHA256 --shash SHA256 --skeysize 3072 --ssig SHA256 -e idonttellyou@kuix.de -u "Test Mail" -o testmail-0227 -p passphrase

The public key was copied to a different VM, imported into gpg, and a 5 K test message was sent encrypted-only from Thunderbird with Enigmail/GnuPG.

Build flags were
cmake -DCMAKE_INSTALL_PREFIX=/home/user/local/openpgp -DGPG_COMPATIBLE=True ..

I built revision 80e5790 from Feb 25.

[kaie]

File enc.pgp contains just the
-----BEGIN PGP MESSAGE-----
...
-----END PGP MESSAGE-----
part of the email message.

File testmail-0227.private contains the unmodified private key as generated by the above key generation command.

[kaie]

Jason, if you point me to your private key, I can send you an equivalent test message. That way you'd be enabled to test it yourself. Thanks.

[calccrypto]

You can use the Alicepub key:

-----BEGIN PGP PUBLIC KEY BLOCK-----
Version: GnuPG v1
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=xJuO
-----END PGP PUBLIC KEY BLOCK-----

[kaie]

encrypted-for-tests_testvectors_gpg_Alicepub.txt

$ ./cli/OpenPGP decrypt-pka tests/testvectors/gpg/Alicepri test encrypted-for-tests_testvectors_gpg_Alicepub.txt
terminate called after throwing an instance of 'std::runtime_error'
what(): Error: Data contains message section. Use CleartextSignature to parse this data.
Aborted (core dumped)

Using this key results in a different error.

[calccrypto]

I think I fixed it with 272e079. The main issues were:

• The file you provided has CRLF line endings, which weren't handled before
• There were some usage errors with Compressed Data Packets (Tag 8)
• There were some logic errors in OpenPGP::Message

Please let me know if you are still having issues.

[kaie]

Thanks. I confirm the issue is fixed when using the message encrypted for the Alicepub key.

However, it still fails to process the message that I had encrypted with the key I had generated.
terminate called after throwing an instance of 'std::runtime_error'
what(): Error: Data does not form a meaningful PGP Key

If you're interested to analyze further, feel free to generate a key for yourself with this command, and send me your public key:
./cli/OpenPGP generate-keypair --phash SHA256 --pkeysize 3072 --psig SHA256 --shash SHA256 --skeysize 3072 --ssig SHA256 -e idonttellyou@kuix.de -u "Test Mail" -o testmail-0227 -p passphrase

[calccrypto]

Apparently the error reading the key was caused by using the wrong formula to get a 2 octet length.

[calccrypto]

@kaie Am I able to close this issue?

[kaie]

Jason, I confirm you've fixed the issue, I'm able to decrypt my test message, thanks a lot!