feat(android): keep the decrypted vault locally under an Android Keystore key
Opening a container costs ~4 s and the iteration count belongs to the desktop format, so the fix is to stop repeating it: derive once per snapshot, then read a local AES file which the hardware accelerates. The key is generated inside the Keystore and never leaves it - the file alone is useless, even rooted. ETag and vault are encrypted together on purpose: an ETag outliving an unreadable vault would make the server answer 304 with nothing to show. A failed read wipes the cache rather than guessing. Also normalises every Delphi source to pure ASCII: Delphi reads a BOM-less file as ANSI, so accented comments came back as mojibake, and each PowerShell rewrite added another layer.
This commit is contained in:
r-zakarya
@@ -14,14 +14,14 @@ unit PMA.Crypto;
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- AES-GCM goes through JNI to javax.crypto. One call, no loop, and the
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platform implementation is hardware-accelerated. Java's Cipher expects the
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tag appended to the ciphertext, which is exactly what WebCrypto produces —
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tag appended to the ciphertext, which is exactly what WebCrypto produces -
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the buffers are byte-identical, nothing to reshape.
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- PBKDF2 is implemented HERE rather than via SecretKeyFactory, because
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javax.crypto.spec.PBEKeySpec takes a char[] and the provider decides how
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those chars become bytes: UTF-8 on some, low-byte on others. For a
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non-ASCII sync password the derived key would differ from the browser's,
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and the failure is silent — "wrong password" on a correct password. Doing
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and the failure is silent - "wrong password" on a correct password. Doing
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it here fixes the encoding at UTF-8 and makes the match exact by
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construction. The cost is 600k HMAC-SHA256 rounds in Pascal; measure it on
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a real device (see DeriveKeyPBKDF2's note) before considering the JNI
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@@ -41,13 +41,13 @@ type
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function DeriveKeyPBKDF2(const APassword: string; const ASalt: TBytes;
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AIterations, AKeyLenBytes: Integer): TBytes;
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/// Same derivation, delegated to Android's SecretKeyFactory — natively
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/// Same derivation, delegated to Android's SecretKeyFactory - natively
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/// implemented, so roughly an order of magnitude faster than the Pascal loop.
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///
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/// NOT used by DecryptContainer, and deliberately so: PBEKeySpec takes a
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/// char[] and the provider decides how those chars become bytes. If Android
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/// encodes them as anything other than UTF-8, this returns a DIFFERENT key for
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/// a non-ASCII password — silently, reported later as a wrong password.
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/// a non-ASCII password - silently, reported later as a wrong password.
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/// The self-test compares it against the known vector on a real device; adopt
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/// it only if they match there. Returns nil on any failure.
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function DeriveKeyPBKDF2Native(const APassword: string; const ASalt: TBytes;
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@@ -57,11 +57,11 @@ function DeriveKeyPBKDF2Native(const APassword: string; const ASalt: TBytes;
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function LastNativeError: string;
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/// AES-256-GCM decrypt. ACipherText carries the 16-byte tag at the end, as
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/// produced by WebCrypto. Raises EPMACrypto when the tag does not verify —
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/// produced by WebCrypto. Raises EPMACrypto when the tag does not verify -
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/// which is what a wrong password looks like.
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function AesGcmDecrypt(const AKey, AIv, ACipherText: TBytes): TBytes;
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/// Full container → plaintext JSON payload. Validates the format marker so a
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/// Full container -> plaintext JSON payload. Validates the format marker so a
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/// truncated download or an HTML error page fails with a clear message rather
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/// than as "wrong password".
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function DecryptContainer(const AContainerJson, APassword: string): string;
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@@ -101,7 +101,7 @@ function DeriveKeyPBKDF2(const APassword: string; const ASalt: TBytes;
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//
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// PERFORMANCE: 600k HMAC rounds. Budget a few seconds on a mid-range phone and
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// run it OFF the UI thread. If it proves unacceptable, the answer is to cache
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// the derived key in the Android Keystore behind biometrics — NOT to lower the
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// the derived key in the Android Keystore behind biometrics - NOT to lower the
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// iteration count, which is shared with the desktop and defines the format.
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var
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LPwd, LBlock, LU, LT: TBytes;
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@@ -139,7 +139,7 @@ end;
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{$IF DEFINED(ANDROID)}
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type
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// Minimal JNI imports. Delphi ships no headers for javax.crypto, and the
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// bridge builds its method signatures from these declarations — hence the
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// bridge builds its method signatures from these declarations - hence the
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// real Java types (Key, AlgorithmParameterSpec) rather than JObject, which
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// would generate a signature no method matches.
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JKey = interface;
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@@ -193,7 +193,7 @@ type
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// generateSecret takes a KeySpec, not an Object. Declaring the real
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// interface is what makes the bridge emit
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// (Ljava/security/spec/KeySpec;)Ljavax/crypto/SecretKey; — with JObject it
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// (Ljava/security/spec/KeySpec;)Ljavax/crypto/SecretKey; - with JObject it
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// emitted a signature no method matches, and the call failed at runtime.
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JKeySpecClass = interface(IJavaClass)
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['{0A1B2C3D-4E5F-6071-8293-A4B5C6D7E8F9}']
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@@ -280,7 +280,7 @@ var
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begin
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Result := nil;
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try
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// The password goes in as chars — the whole point of the doubt. Delphi
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// The password goes in as chars - the whole point of the doubt. Delphi
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// strings are UTF-16, so this hands the provider the code units and lets
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// it apply whatever encoding it wants. That is exactly what the test
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// measures against the vector.
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@@ -328,7 +328,7 @@ begin
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Result := FromJavaBytes(LCipher.doFinal(ToJavaBytes(ACipherText)));
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except
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// AEADBadTagException surfaces here: wrong password, or altered bytes.
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// Both are indistinguishable by design — that is what authentication means.
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// Both are indistinguishable by design - that is what authentication means.
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on E: Exception do
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// Message en pur ASCII : un tiret cadratin dans une source lue en ANSI
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// par Delphi ressort en mojibake sur l'appareil.
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@@ -376,7 +376,7 @@ begin
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if (Length(LSalt) = 0) or (Length(LIv) = 0) or (Length(LCt) = 0) then
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raise EPMACrypto.Create('Container is missing salt, iv or ciphertext');
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// Android's provider first — measured identical to WebCrypto on a
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// Android's provider first - measured identical to WebCrypto on a
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// non-ASCII password (so it does encode as UTF-8), and it is platform
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// code rather than ours. Barely faster though: 3869 ms against 4139 ms,
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// PBKDF2 gets no hardware acceleration. The Pascal path stays as the
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@@ -0,0 +1,341 @@
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unit PMA.Store;
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{
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Coffre garde localement, chiffre sous une cle du Android Keystore.
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POURQUOI : ouvrir un conteneur coute ~4 s (PBKDF2 600k, incompressible - le
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nombre d'iterations appartient au format ecrit par le poste Windows). Payer
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ce prix a chaque ouverture de l'application serait absurde alors que le
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contenu n'a pas change. On ne le paie donc qu'a l'arrivee d'un instantane
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NOUVEAU, et on relit ensuite un fichier local chiffre en AES - accelere
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materiellement, donc instantane.
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LA CLE NE QUITTE JAMAIS LE MATERIEL. Elle est generee dans le Keystore et
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n'en sort pas : on envoie des donnees a chiffrer, on recoit le resultat. Un
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vol du fichier seul est donc inexploitable, meme root - il faut la puce.
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CE QUE CE FICHIER CONTIENT : tous les mots de passe en clair, une fois
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dechiffre. D'ou trois regles tenues ici :
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- jamais hors du repertoire prive de l'application ;
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- jamais de copie en clair sur le disque, meme temporaire ;
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- la sauvegarde automatique Android doit etre desactivee pour l'app
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(android:allowBackup="false"), sinon Google en recupere une copie.
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PAS ENCORE FAIT : exiger la biometrie a chaque lecture
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(setUserAuthenticationRequired). La cle est deja liee au materiel ; la
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biometrie ajouterait une barriere si le telephone est deverrouille et qu'un
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tiers ouvre l'application. A faire dans un second temps, avec BiometricPrompt.
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}
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interface
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uses
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System.SysUtils, System.Classes, System.JSON, System.IOUtils;
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type
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EPMAStore = class(Exception);
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/// Le coffre local existe-t-il ?
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function HasVault: Boolean;
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/// Ecrit le coffre et l'ETag qui l'accompagne, chiffres ensemble.
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procedure SaveVault(const APlainJson, AETag: string);
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/// Relit le coffre. False si absent ou illisible (cle perdue apres une
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/// reinstallation, fichier altere) - dans ce cas il faut retelecharger.
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function LoadVault(out APlainJson, AETag: string): Boolean;
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/// Efface le coffre local. A appeler au moindre doute : il se retelecharge.
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procedure ClearVault;
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/// Chemin du fichier, pour le journal et les tests.
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function VaultPath: string;
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implementation
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{$IF DEFINED(ANDROID)}
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uses
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Androidapi.JNIBridge, Androidapi.JNI.JavaTypes, Androidapi.Helpers;
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{$ENDIF}
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const
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VAULT_FILE = 'vault.bin';
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KEY_ALIAS = 'pm_vault_key';
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// Constantes d'android.security.keystore.KeyProperties, reprises en dur
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// plutot qu'importees : elles sont figees par la plateforme, et cela evite
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// une declaration JNI de plus.
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PURPOSE_ENCRYPT = 1;
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PURPOSE_DECRYPT = 2;
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IV_LEN = 12; // GCM : 12 octets, la longueur recommandee
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function VaultPath: string;
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begin
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// GetHomePath sur Android = /data/data/<paquet>/files, prive a l'app.
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Result := TPath.Combine(TPath.GetHomePath, VAULT_FILE);
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end;
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function HasVault: Boolean;
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begin
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Result := TFile.Exists(VaultPath);
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end;
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procedure ClearVault;
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begin
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if TFile.Exists(VaultPath) then
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TFile.Delete(VaultPath);
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end;
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{$IF DEFINED(ANDROID)}
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type
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JKeyStoreX = interface;
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JSecretKeyX = interface;
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JKeyGenerator = interface;
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JKeyGenParameterSpec = interface;
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JKeyGenParameterSpec_Builder = interface;
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JCipherX = interface;
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JGCMParameterSpecX = interface;
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JAlgorithmParameterSpecX = interface;
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JKeyX = interface;
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JKeyXClass = interface(IJavaClass)
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['{2C1A0B3D-4E5F-6A7B-8C9D-0E1F2A3B4C5D}']
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end;
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[JavaSignature('java/security/Key')]
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JKeyX = interface(IJavaInstance)
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['{3D2B1C4E-5F60-7B8C-9DAE-1F2A3B4C5D6E}']
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end;
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TJKeyX = class(TJavaGenericImport<JKeyXClass, JKeyX>) end;
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JSecretKeyXClass = interface(JKeyXClass)
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['{4E3C2D5F-6071-8C9D-AEBF-2A3B4C5D6E7F}']
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end;
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[JavaSignature('javax/crypto/SecretKey')]
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JSecretKeyX = interface(JKeyX)
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['{5F4D3E60-7182-9DAE-BFC0-3B4C5D6E7F80}']
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end;
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TJSecretKeyX = class(TJavaGenericImport<JSecretKeyXClass, JSecretKeyX>) end;
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JAlgorithmParameterSpecXClass = interface(IJavaClass)
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['{605E4F71-8293-AEBF-C0D1-4C5D6E7F8091}']
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end;
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[JavaSignature('java/security/spec/AlgorithmParameterSpec')]
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JAlgorithmParameterSpecX = interface(IJavaInstance)
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['{716F5082-93A4-BFC0-D1E2-5D6E7F8091A2}']
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end;
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TJAlgorithmParameterSpecX = class(TJavaGenericImport<JAlgorithmParameterSpecXClass, JAlgorithmParameterSpecX>) end;
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JGCMParameterSpecXClass = interface(JAlgorithmParameterSpecXClass)
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['{82706193-A4B5-C0D1-E2F3-6E7F8091A2B3}']
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function init(tLen: Integer; src: TJavaArray<Byte>): JGCMParameterSpecX; cdecl;
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end;
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[JavaSignature('javax/crypto/spec/GCMParameterSpec')]
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JGCMParameterSpecX = interface(JAlgorithmParameterSpecX)
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['{938172A4-B5C6-D1E2-F304-7F8091A2B3C4}']
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end;
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TJGCMParameterSpecX = class(TJavaGenericImport<JGCMParameterSpecXClass, JGCMParameterSpecX>) end;
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JKeyStoreXClass = interface(JObjectClass)
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['{A49283B5-C6D7-E2F3-0415-8091A2B3C4D5}']
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function getInstance(&type: JString): JKeyStoreX; cdecl;
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end;
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[JavaSignature('java/security/KeyStore')]
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JKeyStoreX = interface(JObject)
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['{B5A394C6-D7E8-F304-1526-91A2B3C4D5E6}']
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procedure load(param: JObject); cdecl;
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function getKey(alias: JString; password: TJavaArray<Char>): JKeyX; cdecl;
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function containsAlias(alias: JString): Boolean; cdecl;
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end;
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TJKeyStoreX = class(TJavaGenericImport<JKeyStoreXClass, JKeyStoreX>) end;
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JKeyGenParameterSpec_BuilderClass = interface(JObjectClass)
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['{C6B4A5D7-E8F9-0415-2637-A2B3C4D5E6F7}']
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function init(keystoreAlias: JString; purposes: Integer): JKeyGenParameterSpec_Builder; cdecl;
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end;
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[JavaSignature('android/security/keystore/KeyGenParameterSpec$Builder')]
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JKeyGenParameterSpec_Builder = interface(JObject)
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['{D7C5B6E8-F90A-1526-3748-B3C4D5E6F708}']
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function setBlockModes(blockModes: TJavaObjectArray<JString>): JKeyGenParameterSpec_Builder; cdecl;
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function setEncryptionPaddings(paddings: TJavaObjectArray<JString>): JKeyGenParameterSpec_Builder; cdecl;
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function setKeySize(keySize: Integer): JKeyGenParameterSpec_Builder; cdecl;
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function build: JKeyGenParameterSpec; cdecl;
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end;
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TJKeyGenParameterSpec_Builder = class(TJavaGenericImport<JKeyGenParameterSpec_BuilderClass, JKeyGenParameterSpec_Builder>) end;
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JKeyGenParameterSpecClass = interface(JAlgorithmParameterSpecXClass)
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['{E8D6C7F9-0A1B-2637-4859-C4D5E6F70819}']
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end;
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[JavaSignature('android/security/keystore/KeyGenParameterSpec')]
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JKeyGenParameterSpec = interface(JAlgorithmParameterSpecX)
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['{F9E7D80A-1B2C-3748-5960-D5E6F7081920}']
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end;
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TJKeyGenParameterSpec = class(TJavaGenericImport<JKeyGenParameterSpecClass, JKeyGenParameterSpec>) end;
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JKeyGeneratorClass = interface(JObjectClass)
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['{0AF8E91B-2C3D-4859-6A71-E6F708192031}']
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function getInstance(algorithm: JString; provider: JString): JKeyGenerator; cdecl;
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end;
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[JavaSignature('javax/crypto/KeyGenerator')]
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JKeyGenerator = interface(JObject)
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['{1B09FA2C-3D4E-5960-7B82-F70819203142}']
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procedure init(params: JAlgorithmParameterSpecX); cdecl;
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function generateKey: JSecretKeyX; cdecl;
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end;
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TJKeyGenerator = class(TJavaGenericImport<JKeyGeneratorClass, JKeyGenerator>) end;
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JCipherXClass = interface(JObjectClass)
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['{2C1A0B3D-4E5F-6A71-8C93-081920314253}']
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function _GetENCRYPT_MODE: Integer; cdecl;
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function _GetDECRYPT_MODE: Integer; cdecl;
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function getInstance(transformation: JString): JCipherX; cdecl;
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property ENCRYPT_MODE: Integer read _GetENCRYPT_MODE;
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property DECRYPT_MODE: Integer read _GetDECRYPT_MODE;
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end;
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[JavaSignature('javax/crypto/Cipher')]
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JCipherX = interface(JObject)
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['{3D2B1C4E-5F60-7B82-9DA4-192031425364}']
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procedure init(opmode: Integer; key: JKeyX); cdecl;
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procedure init(opmode: Integer; key: JKeyX; params: JAlgorithmParameterSpecX); cdecl; overload;
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function doFinal(input: TJavaArray<Byte>): TJavaArray<Byte>; cdecl;
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function getIV: TJavaArray<Byte>; cdecl;
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end;
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TJCipherX = class(TJavaGenericImport<JCipherXClass, JCipherX>) end;
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function ToJava(const B: TBytes): TJavaArray<Byte>;
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var I: Integer;
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begin
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Result := TJavaArray<Byte>.Create(Length(B));
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for I := 0 to High(B) do Result.Items[I] := B[I];
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end;
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function FromJava(const A: TJavaArray<Byte>): TBytes;
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var I: Integer;
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begin
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SetLength(Result, A.Length);
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for I := 0 to A.Length - 1 do Result[I] := A.Items[I];
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end;
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/// La cle du Keystore, creee a la premiere utilisation. Elle n'est jamais
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/// lue : on obtient une poignee vers un objet que seul le materiel peut
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/// utiliser.
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function EnsureKey: JKeyX;
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var
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LStore: JKeyStoreX;
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LGen: JKeyGenerator;
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LBuilder: JKeyGenParameterSpec_Builder;
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LModes, LPaddings: TJavaObjectArray<JString>;
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begin
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LStore := TJKeyStoreX.JavaClass.getInstance(StringToJString('AndroidKeyStore'));
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LStore.load(nil); // le magasin Android ne prend pas de flux
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if LStore.containsAlias(StringToJString(KEY_ALIAS)) then
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Exit(LStore.getKey(StringToJString(KEY_ALIAS), nil));
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LModes := TJavaObjectArray<JString>.Create(1);
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LModes.Items[0] := StringToJString('GCM');
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LPaddings := TJavaObjectArray<JString>.Create(1);
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LPaddings.Items[0] := StringToJString('NoPadding');
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LBuilder := TJKeyGenParameterSpec_Builder.JavaClass.init(
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StringToJString(KEY_ALIAS), PURPOSE_ENCRYPT or PURPOSE_DECRYPT);
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LBuilder := LBuilder.setBlockModes(LModes);
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LBuilder := LBuilder.setEncryptionPaddings(LPaddings);
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LBuilder := LBuilder.setKeySize(256);
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LGen := TJKeyGenerator.JavaClass.getInstance(
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StringToJString('AES'), StringToJString('AndroidKeyStore'));
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LGen.init(LBuilder.build);
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Result := LGen.generateKey; // stockee sous l'alias, pas retournee en clair
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end;
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{$ENDIF}
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procedure SaveVault(const APlainJson, AETag: string);
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{$IF DEFINED(ANDROID)}
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var
|
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LWrap: TJSONObject;
|
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LPlain, LIv, LCt, LOut: TBytes;
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LCipher: JCipherX;
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begin
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// ETag et coffre chiffres ENSEMBLE : ils doivent rester coherents. Un ETag
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// qui survivrait a un coffre illisible ferait repondre 304 au serveur alors
|
||||
// que l'application n'a rien a afficher.
|
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LWrap := TJSONObject.Create;
|
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try
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LWrap.AddPair('etag', AETag);
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LWrap.AddPair('vault', APlainJson);
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LPlain := TEncoding.UTF8.GetBytes(LWrap.ToJSON);
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finally
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||||
LWrap.Free;
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end;
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||||
|
||||
LCipher := TJCipherX.JavaClass.getInstance(StringToJString('AES/GCM/NoPadding'));
|
||||
LCipher.init(TJCipherX.JavaClass.ENCRYPT_MODE, EnsureKey);
|
||||
// L'IV est GENERE par le Keystore, jamais choisi par nous : le reutiliser
|
||||
// avec la meme cle romprait GCM.
|
||||
LIv := FromJava(LCipher.getIV);
|
||||
LCt := FromJava(LCipher.doFinal(ToJava(LPlain)));
|
||||
|
||||
SetLength(LOut, 1 + Length(LIv) + Length(LCt));
|
||||
LOut[0] := 1; // version de format
|
||||
Move(LIv[0], LOut[1], Length(LIv));
|
||||
Move(LCt[0], LOut[1 + Length(LIv)], Length(LCt));
|
||||
TFile.WriteAllBytes(VaultPath, LOut);
|
||||
end;
|
||||
{$ELSE}
|
||||
begin
|
||||
raise EPMAStore.Create('Le stockage Keystore est propre a Android');
|
||||
end;
|
||||
{$ENDIF}
|
||||
|
||||
function LoadVault(out APlainJson, AETag: string): Boolean;
|
||||
{$IF DEFINED(ANDROID)}
|
||||
var
|
||||
LRaw, LIv, LCt, LPlain: TBytes;
|
||||
LCipher: JCipherX;
|
||||
LWrap: TJSONObject;
|
||||
begin
|
||||
Result := False;
|
||||
APlainJson := '';
|
||||
AETag := '';
|
||||
if not TFile.Exists(VaultPath) then Exit;
|
||||
|
||||
try
|
||||
LRaw := TFile.ReadAllBytes(VaultPath);
|
||||
if (Length(LRaw) < 1 + IV_LEN + 16) or (LRaw[0] <> 1) then Exit;
|
||||
|
||||
SetLength(LIv, IV_LEN);
|
||||
Move(LRaw[1], LIv[0], IV_LEN);
|
||||
SetLength(LCt, Length(LRaw) - 1 - IV_LEN);
|
||||
Move(LRaw[1 + IV_LEN], LCt[0], Length(LCt));
|
||||
|
||||
LCipher := TJCipherX.JavaClass.getInstance(StringToJString('AES/GCM/NoPadding'));
|
||||
LCipher.init(TJCipherX.JavaClass.DECRYPT_MODE, EnsureKey,
|
||||
TJGCMParameterSpecX.JavaClass.init(128, ToJava(LIv)));
|
||||
LPlain := FromJava(LCipher.doFinal(ToJava(LCt)));
|
||||
|
||||
LWrap := TJSONObject.ParseJSONValue(TEncoding.UTF8.GetString(LPlain)) as TJSONObject;
|
||||
if LWrap = nil then Exit;
|
||||
try
|
||||
AETag := LWrap.GetValue<string>('etag', '');
|
||||
APlainJson := LWrap.GetValue<string>('vault', '');
|
||||
Result := APlainJson <> '';
|
||||
finally
|
||||
LWrap.Free;
|
||||
end;
|
||||
except
|
||||
// Cle disparue (reinstallation, effacement du Keystore) ou fichier
|
||||
// altere : on ne tente rien, l'appelant retelechargera.
|
||||
on E: Exception do
|
||||
begin
|
||||
Result := False;
|
||||
ClearVault;
|
||||
end;
|
||||
end;
|
||||
end;
|
||||
{$ELSE}
|
||||
begin
|
||||
Result := False;
|
||||
APlainJson := '';
|
||||
AETag := '';
|
||||
end;
|
||||
{$ENDIF}
|
||||
|
||||
end.
|
||||
@@ -3,7 +3,7 @@ unit PMA.SyncClient;
|
||||
Lecture de l'instantane chiffre depuis l'endpoint PHP (server-php/sync.php).
|
||||
|
||||
Ne dechiffre rien : il ramene des octets opaques et l'ETag qui les identifie.
|
||||
Le dechiffrement est le travail de PMA.Crypto, et il coute 4 secondes — d'ou
|
||||
Le dechiffrement est le travail de PMA.Crypto, et il coute 4 secondes - d'ou
|
||||
l'importance de l'ETag, qui evite de le refaire quand rien n'a change.
|
||||
|
||||
Le serveur repond 404 aussi bien pour un jeton invalide que pour un
|
||||
|
||||
Reference in New Issue
Block a user