Support GnuPG AEAD password entries

crates/storage/src/crypto.rs

@@ -11,8 +11,9 @@ use std::{
 use cap_std::{ambient_authority, fs::Dir};
 use pgp::{
     composed::{
-        ArmorOptions, Deserializable, DetachedSignature, Esk, Message, MessageBuilder,
-        PublicOrSecret, SignedPublicKey, SignedPublicSubKey, SignedSecretKey, SubpacketConfig,
+        ArmorOptions, DecryptionOptions, Deserializable, DetachedSignature, Esk, Message,
+        MessageBuilder, PublicOrSecret, SignedPublicKey, SignedPublicSubKey, SignedSecretKey,
+        SubpacketConfig, TheRing,
     },
     crypto::{hash::HashAlgorithm, sym::SymmetricKeyAlgorithm},
     packet::{SignatureType, Subpacket, SubpacketData},
@@ -460,7 +461,13 @@ impl KeyStore {
             let password = Password::from(supplied.expose());
             let message = Message::from_bytes(Cursor::new(ciphertext.as_bytes()))
                 .map_err(|_| CryptoError::CorruptMessage)?;
-            if let Ok(mut decrypted) = message.decrypt(&password, secret)
+            let ring = TheRing {
+                secret_keys: vec![secret],
+                key_passwords: vec![&password],
+                decrypt_options: DecryptionOptions::new().enable_gnupg_aead(),
+                ..Default::default()
+            };
+            if let Ok((mut decrypted, _)) = message.decrypt_the_ring(ring, true)
                 && let Ok(plaintext) = decrypted.as_data_vec()
             {
                 if let Some(info) = key.as_ref() {

crates/storage/tests/crypto_compatibility.rs

@@ -8,15 +8,22 @@ use ironstorage::{
     crypto::{
         CryptoError, DetachedSignatureBytes, KeyInfo, KeyStore, SecretProvider, SecretProviderError,
     },
-    repository::{EncryptedEntry, SecretBytes},
+    read::{ShowResult, VaultReader},
+    repository::{EncryptedEntry, Repository, SecretBytes},
 };
 use pgp::{
-    composed::{EncryptionCaps, KeyType, Message, SecretKeyParamsBuilder, SubkeyParamsBuilder},
-    crypto::{ecc_curve::ECCCurve, hash::HashAlgorithm, sym::SymmetricKeyAlgorithm},
+    composed::{
+        Edata, EncryptionCaps, Esk, KeyType, Message, SecretKeyParamsBuilder, SubkeyParamsBuilder,
+    },
+    crypto::{
+        aead::AeadAlgorithm, ecc_curve::ECCCurve, hash::HashAlgorithm, sym::SymmetricKeyAlgorithm,
+    },
+    packet::{ProtectedDataConfig, SymEncryptedProtectedDataConfig},
     ser::Serialize as _,
     types::{Password, Timestamp},
 };
 use rand_chacha::{ChaCha20Rng, rand_core::SeedableRng};
+use sha2::{Digest as _, Sha256};
 use smallvec::smallvec;
 use support::compatibility::{FixtureSet, TestResult};
 
@@ -24,6 +31,8 @@ use support::compatibility::{FixtureSet, TestResult};
 struct FixtureSecrets {
     values: BTreeMap<String, Vec<u8>>,
     requests: Vec<String>,
+    accepted: Vec<String>,
+    rejected: Vec<String>,
 }
 
 impl FixtureSecrets {
@@ -41,6 +50,8 @@ impl FixtureSecrets {
                 })
                 .collect(),
             requests: Vec::new(),
+            accepted: Vec::new(),
+            rejected: Vec::new(),
         }
     }
 
@@ -48,6 +59,8 @@ impl FixtureSecrets {
         Self {
             values: BTreeMap::from([(fingerprint.to_owned(), passphrase.as_ref().to_vec())]),
             requests: Vec::new(),
+            accepted: Vec::new(),
+            rejected: Vec::new(),
         }
     }
 }
@@ -62,6 +75,15 @@ impl SecretProvider for FixtureSecrets {
             .map(SecretBytes::new)
             .ok_or(SecretProviderError::Unavailable)
     }
+
+    fn secret_accepted(&mut self, key: &KeyInfo) -> Result<(), SecretProviderError> {
+        self.accepted.push(key.fingerprint().as_str().to_owned());
+        Ok(())
+    }
+
+    fn secret_rejected(&mut self, key: &KeyInfo) {
+        self.rejected.push(key.fingerprint().as_str().to_owned());
+    }
 }
 
 struct CancelledProvider;
@@ -186,6 +208,127 @@ fn decrypts_every_gnupg_audited_pass_fixture() -> TestResult {
     Ok(())
 }
 
+#[test]
+fn decrypts_gnupg_packet_20_aes256_ocb_through_the_vault_reader() -> TestResult {
+    let fixture = FixtureSet::load()?;
+    let aead = &fixture.gnupg_aead;
+    let alice = fixture.key("alice")?;
+    assert_eq!(aead.format, 1);
+    assert_eq!(aead.producer, "GnuPG 2.4.8");
+    assert!(aead.command_profile.contains("--force-ocb"));
+    assert_eq!(aead.packet_tag, 20);
+    assert_eq!(aead.cipher, "AES256");
+    assert_eq!(aead.aead_mode, "OCB");
+    assert_eq!(
+        aead.recipient_primary_fingerprint,
+        alice.primary_fingerprint
+    );
+    assert_eq!(
+        aead.recipient_encryption_subkey_fingerprint,
+        alice.encryption_subkey_fingerprint
+    );
+
+    let ciphertext = fixture.read(&aead.entry)?;
+    assert_eq!(
+        hex::encode(Sha256::digest(&ciphertext)),
+        aead.ciphertext_sha256
+    );
+    let message = Message::from_bytes(Cursor::new(&ciphertext))?;
+    let Message::Encrypted { esk, edata, .. } = &message else {
+        panic!("GnuPG AEAD fixture must be encrypted");
+    };
+    let [Esk::PublicKeyEncryptedSessionKey(pkesk)] = esk.as_slice() else {
+        panic!("GnuPG AEAD fixture must have one public-key recipient");
+    };
+    let secret = fixture.parse_secret_key(alice)?;
+    assert!(pkesk.match_identity(&secret.secret_subkeys[0].key));
+    assert!(!pkesk.match_identity(&secret.primary_key));
+    let Edata::GnupgAeadData { reader } = edata else {
+        panic!("GnuPG fixture must use packet type 20");
+    };
+    let ProtectedDataConfig::GnupgAead(config) = reader.config() else {
+        panic!("packet type 20 must carry GnuPG AEAD configuration");
+    };
+    assert_eq!(config.sym_alg, SymmetricKeyAlgorithm::AES256);
+    assert_eq!(config.aead, AeadAlgorithm::Ocb);
+
+    let repository = Repository::open(fixture.path(format!("gnupg-aead/{}", aead.store)))?;
+    let keys = KeyStore::load(fixture.path("keys"))?;
+    let reader = VaultReader::new(&repository, &keys);
+    let mut provider = FixtureSecrets::one(&alice.primary_fingerprint, &alice.passphrase);
+    let ShowResult::Entry(plaintext) = reader.show(Some("paypal"), &mut provider)? else {
+        panic!("paypal must resolve as an entry");
+    };
+    assert_eq!(plaintext.expose(), fixture.read(&aead.plaintext)?);
+    assert_eq!(
+        provider.requests,
+        std::slice::from_ref(&alice.primary_fingerprint)
+    );
+    assert_eq!(
+        provider.accepted,
+        std::slice::from_ref(&alice.primary_fingerprint)
+    );
+    assert!(provider.rejected.is_empty());
+    Ok(())
+}
+
+#[test]
+fn rejects_invalid_gnupg_packet_20_inputs_without_accepting_secrets() -> TestResult {
+    let fixture = FixtureSet::load()?;
+    let aead = &fixture.gnupg_aead;
+    let alice = fixture.key("alice")?;
+    let ciphertext = fixture.read(&aead.entry)?;
+    let keys = KeyStore::load(fixture.path(&alice.secret_armor))?;
+
+    let mut wrong = FixtureSecrets::one(&alice.primary_fingerprint, b"wrong-aead-passphrase");
+    assert!(matches!(
+        keys.decrypt(&EncryptedEntry::new(ciphertext.clone()), &mut wrong),
+        Err(CryptoError::DecryptionFailed)
+    ));
+    assert!(wrong.accepted.is_empty());
+    assert_eq!(
+        wrong.rejected,
+        std::slice::from_ref(&alice.primary_fingerprint)
+    );
+
+    let mut tampered = ciphertext.clone();
+    *tampered.last_mut().expect("non-empty AEAD fixture") ^= 0x01;
+    let mut correct = FixtureSecrets::one(&alice.primary_fingerprint, &alice.passphrase);
+    assert!(matches!(
+        keys.decrypt(&EncryptedEntry::new(tampered), &mut correct),
+        Err(CryptoError::DecryptionFailed)
+    ));
+    assert!(correct.accepted.is_empty());
+    assert_eq!(
+        correct.rejected,
+        std::slice::from_ref(&alice.primary_fingerprint)
+    );
+
+    let public_only = KeyStore::load(fixture.path(&alice.public_armor))?;
+    let mut unavailable = FixtureSecrets::default();
+    assert!(matches!(
+        public_only.decrypt(&EncryptedEntry::new(ciphertext.clone()), &mut unavailable),
+        Err(CryptoError::MissingSecretKey)
+    ));
+    assert!(unavailable.requests.is_empty());
+
+    let mut unsupported = ciphertext;
+    let config = unsupported
+        .windows(3)
+        .position(|window| window == [1, 9, 2])
+        .expect("packet-20 version, AES-256, and OCB configuration");
+    unsupported[config + 2] = 1;
+    let mut unused = FixtureSecrets::one(&alice.primary_fingerprint, &alice.passphrase);
+    assert!(matches!(
+        keys.decrypt(&EncryptedEntry::new(unsupported), &mut unused),
+        Err(CryptoError::CorruptMessage)
+    ));
+    assert!(unused.requests.is_empty());
+    assert!(unused.accepted.is_empty());
+    assert!(unused.rejected.is_empty());
+    Ok(())
+}
+
 #[test]
 fn encrypts_for_one_or_many_recipients_without_compression() -> TestResult {
     let fixture = FixtureSet::load()?;
@@ -203,7 +346,16 @@ fn encrypts_for_one_or_many_recipients_without_compression() -> TestResult {
     let ciphertext = keys.encrypt(SecretBytes::new(expected.to_vec()), &recipients)?;
 
     let parsed = Message::from_bytes(Cursor::new(ciphertext.as_bytes()))?;
-    assert!(parsed.is_encrypted());
+    let Message::Encrypted { edata, .. } = &parsed else {
+        panic!("IronStorage output must be encrypted");
+    };
+    let Edata::SymEncryptedProtectedData { reader } = edata else {
+        panic!("IronStorage output must remain packet type 18");
+    };
+    assert_eq!(
+        reader.config(),
+        &ProtectedDataConfig::Seipd(SymEncryptedProtectedDataConfig::V1)
+    );
     for key in [alice, bob] {
         let mut provider = FixtureSecrets::one(&key.primary_fingerprint, &key.passphrase);
         let plaintext = keys.decrypt(&ciphertext, &mut provider)?;

crates/storage/tests/fixtures/compatibility/README.md

@@ -22,6 +22,14 @@ secrets. The generator reuses the checked-in identities and produces:
 - valid loose-object Git repository templates, including an automatic-commit
   history and nested-repository boundaries.
 
+`gnupg-aead/` is a separate, non-generated compatibility case. Its synthetic
+Alice entry was encrypted by GnuPG 2.4.8 with AES-256 and `--force-ocb`, yielding
+GnuPG AEAD packet type 20 addressed to Alice's encryption subkey. The directory
+contains the exact producer profile and ciphertext digest, a normal
+password-store tree, and the expected plaintext. It deliberately lives outside
+the reproducible generator's `stores/`, `expected/`, and `repositories/`
+directories so a refresh cannot silently replace genuine GnuPG producer output.
+
 Rust tests parse keys, verify signatures, decrypt every entry, compare exact
 plaintext bytes, validate ciphertext digests, validate Git objects and refs,
 and materialize isolated stores and repositories. They never invoke `pass`,
@@ -43,6 +51,11 @@ then make that rotation intentionally non-reproducible. Review all binary
 changes and the generated fingerprints, digests, and Git object IDs before
 committing them.
 
+When rotating the checked-in synthetic identities, regenerate the packet-20
+case explicitly with the producer profile in `gnupg-aead/fixture.toml`, update
+both recorded fingerprints and the digest, and independently inspect it with
+GnuPG's packet listing before review.
+
 An optional developer interoperability audit may import the generated keys
 into a disposable GnuPG home, decrypt the `.gpg` entries, and point an
 upstream `pass` 1.7.4 checkout at a materialized store. That audit is never a

crates/storage/tests/fixtures/compatibility/gnupg-aead/expected/paypal.txt

@@ -0,0 +1,3 @@
+synthetic-aead-password
+login: alice@example.test
+url: https://paypal.example.test

crates/storage/tests/fixtures/compatibility/gnupg-aead/fixture.toml

@@ -0,0 +1,12 @@
+format = 1
+producer = "GnuPG 2.4.8"
+command_profile = "--batch --trust-model always --compress-algo none --cipher-algo AES256 --force-ocb --set-filename '' --encrypt"
+packet_tag = 20
+cipher = "AES256"
+aead_mode = "OCB"
+recipient_primary_fingerprint = "7E5C5241B25F6FFAAD717EBFA132DCB2DC23AE30"
+recipient_encryption_subkey_fingerprint = "10208D0B84AD13D2157795D5EB55885EC93C0A26"
+store = "store"
+entry = "gnupg-aead/store/paypal.gpg"
+plaintext = "gnupg-aead/expected/paypal.txt"
+ciphertext_sha256 = "4dc0eae06afa822739f41a296cd61a9bd1af91057c2ab1d61e4441874250eaf7"

crates/storage/tests/fixtures/compatibility/gnupg-aead/store/.gpg-id

@@ -0,0 +1 @@
+7E5C5241B25F6FFAAD717EBFA132DCB2DC23AE30

crates/storage/tests/secret_store.rs

@@ -504,6 +504,69 @@ fn missing_openpgp_passphrases_are_prompted_verified_and_only_then_persisted() -
     Ok(())
 }
 
+#[test]
+fn gnupg_aead_passphrases_are_persisted_only_after_authenticated_decryption() -> TestResult {
+    let fixture = FixtureSet::load()?;
+    let key = fixture.key("alice")?;
+    let keys = KeyStore::load(fixture.path(&key.secret_armor))?;
+    let ciphertext = fixture.read(&fixture.gnupg_aead.entry)?;
+    let expected = fixture.read(&fixture.gnupg_aead.plaintext)?;
+    let reference = SecretReference::openpgp_passphrase(&key.primary_fingerprint)?;
+
+    let prompt = MemoryPrompt::responding(Ok(key.passphrase.as_bytes()));
+    let mut provisioned =
+        store(MemoryBackend::default()).with_openpgp_passphrase_prompt(prompt.clone());
+    provisioned.unlock()?;
+    assert_eq!(
+        keys.decrypt(&EncryptedEntry::new(ciphertext.clone()), &mut provisioned)?
+            .expose(),
+        expected
+    );
+    assert_eq!(
+        provisioned.retrieve(&reference)?.expose(),
+        key.passphrase.as_bytes()
+    );
+    assert_eq!(
+        prompt.requested(),
+        std::slice::from_ref(&key.primary_fingerprint)
+    );
+
+    let wrong_prompt = MemoryPrompt::responding(Ok(b"incorrect AEAD passphrase"));
+    let mut wrong =
+        store(MemoryBackend::default()).with_openpgp_passphrase_prompt(wrong_prompt.clone());
+    wrong.unlock()?;
+    assert!(matches!(
+        keys.decrypt(&EncryptedEntry::new(ciphertext.clone()), &mut wrong),
+        Err(CryptoError::DecryptionFailed)
+    ));
+    assert!(matches!(
+        wrong.retrieve(&reference),
+        Err(SecretStoreError::Missing)
+    ));
+    assert_eq!(
+        wrong_prompt.requested(),
+        std::slice::from_ref(&key.primary_fingerprint)
+    );
+
+    let mut tampered_ciphertext = ciphertext;
+    *tampered_ciphertext
+        .last_mut()
+        .expect("non-empty AEAD fixture") ^= 0x01;
+    let tampered_prompt = MemoryPrompt::responding(Ok(key.passphrase.as_bytes()));
+    let mut tampered =
+        store(MemoryBackend::default()).with_openpgp_passphrase_prompt(tampered_prompt);
+    tampered.unlock()?;
+    assert!(matches!(
+        keys.decrypt(&EncryptedEntry::new(tampered_ciphertext), &mut tampered),
+        Err(CryptoError::DecryptionFailed)
+    ));
+    assert!(matches!(
+        tampered.retrieve(&reference),
+        Err(SecretStoreError::Missing)
+    ));
+    Ok(())
+}
+
 fn fs_config(temporary: &tempfile::TempDir) -> TestResult {
     std::fs::create_dir_all(temporary.path().join("keys"))?;
     std::fs::create_dir_all(temporary.path().join("vault"))?;

crates/storage/tests/support/compatibility.rs

@@ -99,11 +99,28 @@ pub struct RepositoryRecord {
     pub commits: Vec<String>,
 }
 
+#[derive(Debug, Deserialize)]
+pub struct GnuPgAeadFixture {
+    pub format: u8,
+    pub producer: String,
+    pub command_profile: String,
+    pub packet_tag: u8,
+    pub cipher: String,
+    pub aead_mode: String,
+    pub recipient_primary_fingerprint: String,
+    pub recipient_encryption_subkey_fingerprint: String,
+    pub store: String,
+    pub entry: String,
+    pub plaintext: String,
+    pub ciphertext_sha256: String,
+}
+
 pub struct FixtureSet {
     root: PathBuf,
     pub upstream: UpstreamManifest,
     pub behavior: BehaviorManifest,
     pub generated: GeneratedManifest,
+    pub gnupg_aead: GnuPgAeadFixture,
     pub layouts: toml::Value,
 }
 
@@ -113,12 +130,14 @@ impl FixtureSet {
         let upstream = parse_toml(root.join("upstream.toml"))?;
         let behavior = parse_toml(root.join("behavior.toml"))?;
         let generated = parse_toml(root.join("generated.toml"))?;
+        let gnupg_aead = parse_toml(root.join("gnupg-aead/fixture.toml"))?;
         let layouts = parse_toml(root.join("layouts.toml"))?;
         Ok(Self {
             root,
             upstream,
             behavior,
             generated,
+            gnupg_aead,
             layouts,
         })
     }

docs/cryptography.md

@@ -38,6 +38,8 @@ encryption-capable primary key. Output uses AES-256 in a version 1
 symmetrically-encrypted integrity-protected data packet and deliberately does
 not add a compression packet, matching upstream `pass --compress-algo=none`.
 Every resolved recipient receives a public-key encrypted session-key packet.
+IronStorage continues to produce this packet-type-18 SEIPDv1/MDC profile so
+existing output remains unchanged.
 
 Decryption first examines those recipient packets. A secret is requested only
 for imported protected keys that can match the message; unavailable identities
@@ -45,6 +47,37 @@ are skipped so any one recipient of a multi-recipient entry can decrypt it.
 Cancellation stops immediately. Wrong secrets, malformed messages, and a lack
 of matching secret keys remain distinct failures.
 
+For compatibility with password stores written by modern GnuPG, decryption
+also accepts GnuPG's packet-type-20 OCB AEAD extension; the checked-in
+GnuPG 2.4.8 compatibility case uses AES-256.
+This is an explicit read-compatibility profile: it does not enable historical
+unauthenticated encrypted-data packets, accept unsupported packet-20 modes, or
+change the format IronStorage writes. AEAD authentication must succeed before
+the provider is told that an interactively supplied passphrase was accepted;
+wrong passphrases and tampered ciphertext therefore cannot be persisted.
+
+### Upstream `pass` format boundary
+
+The format boundary was re-audited against the current upstream tools on
+2026-08-10. [`pass` 1.7.4 delegates reads and writes directly to
+GnuPG](https://git.zx2c4.com/password-store/plain/src/password-store.sh): reads
+use `gpg -d`, while writes use `gpg -e` with `--compress-algo=none`; `pass`
+does not select or parse an encrypted-data packet itself. The current
+[Homebrew `pass` formula](https://formulae.brew.sh/formula/pass) packages that
+same release with GnuPG 2.5.21. GnuPG's
+[OpenPGP options](https://www.gnupg.org/documentation/manuals/gnupg/OpenPGP-Options.html)
+state that public-key encryption selects CFB+MDC or OCB from recipient key
+preferences, which explains why an ordinary current `pass` installation can
+write packet type 20 without a `pass` option requesting it.
+
+Default `pass` does not opt into unauthenticated legacy decryption. GnuPG made
+missing-MDC messages a hard failure in 2.2.8 and requires the explicit,
+dangerous `--ignore-mdc-error` override to recover plaintext from them. The
+[GnuPG 2.2.8 security release](https://lists.gnupg.org/pipermail/gnupg-users/2018-June/060644.html)
+warns against using that override unconditionally. IronStorage therefore keeps
+legacy packet-type-9 decryption disabled: its default behavior matches default
+`pass` while preserving the authenticated-decryption guarantee.
+
 ## Secret lifetime and recipient signatures
 
 Decrypted data and provider-returned unlock secrets use `SecretBytes`. Its
@@ -65,12 +98,15 @@ from another imported key is rejected.
 ## Compatibility evidence
 
 `crates/storage/tests/fixtures/compatibility` contains protected public and
-secret exports, single- and multi-recipient `.gpg` entries, and signed
-recipient files. The fixture audit established that GnuPG decrypts the packet
-profile used by the generator. Production tests then exercise that same
-uncompressed `MessageBuilder` profile through `KeyStore::encrypt`, independently
-parse and decrypt its output, decrypt every checked-in GnuPG-audited entry, and
-verify both checked-in and newly generated recipient signatures.
+secret exports, single- and multi-recipient `.gpg` entries, signed recipient
+files, and a GnuPG 2.4.8-produced packet-type-20 AES-256/OCB entry. The fixture
+audit established that GnuPG decrypts the packet profile used by the generator.
+Production tests then exercise that same uncompressed `MessageBuilder` profile
+through `KeyStore::encrypt`, independently parse and decrypt its output, decrypt
+every checked-in GnuPG-audited entry through the storage API, and verify both
+checked-in and newly generated recipient signatures. Packet-type-20 tests also
+cover the exact encryption subkey, wrong passphrases, authentication failure,
+missing secret keys, unsupported modes, and deferred secret persistence.
 
 Tests never use a real user keyring and application runtime never executes an
 external cryptographic tool.