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feat(applet): StepUpApplet derives session keys on SELECT when armed

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After AUTH1 parks StepUpSK in SessionContext, the reader issues SELECT
to the Step-Up AID per spec §10.2. StepUpApplet.select() now picks up
the parked SK, derives StepUpSKDevice / StepUpSKReader via the
§8.4.3 HKDF (already implemented in AliroCrypto.deriveStepUpSessionKeys),
and stages both in transient CLEAR_ON_DESELECT fields for the ENVELOPE
(M1C.1) and EXCHANGE (M1B.1) handlers.

Introduces CryptoSingletons -- a lazy package-private holder for the
single AliroCrypto instance shared between AliroApplet and StepUpApplet.
Saves ~352 B of transient (kdfWorkbuf + hkdfPrevT + expandScratch)
versus a per-applet duplicate. Java Card forbids new in <clinit> so
the singleton uses lazy null-check init. Opt 1 prelude per
docs/plans/2026-06-11-step-up-implementation-v2.md.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
This commit is contained in:
michael
2026-06-11 10:33:46 -07:00
parent cedefef70e
commit 8e999b770d
4 changed files with 207 additions and 5 deletions
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17
applet/src/main/java/com/dangerousthings/aliro/AliroApplet.java
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@@ -142,8 +142,10 @@ public class AliroApplet extends Applet {
* needs a separate {@code expeditedSKDeviceKey} field. */
private AliroGcm gcm;
/** Low-level crypto primitives (ECDH, HKDF, Kdh, expedited key derivation). */
private AliroCrypto crypto;
// Low-level crypto primitives (ECDH, HKDF, Kdh, expedited key derivation)
// are pulled from CryptoSingletons.getAliroCrypto() so both AliroApplet
// and StepUpApplet share one instance — saves ~352 B transient versus a
// per-applet duplicate. Local refs in deriveSessionKeys / processDiag.
/** Persistent (1B EEPROM) — set after {@link #ensureCryptoInitialized()} runs. */
private byte cryptoInitialized;
@@ -293,7 +295,9 @@ public class AliroApplet extends Applet {
} catch (ISOException e) { throw e; // preserve inner diagnostic SW
} catch (Throwable t) { ISOException.throwIt((short) 0x6FA8); }
try {
crypto = new AliroCrypto();
// Force lazy alloc of the shared AliroCrypto so the same install-
// time failure ladder applies if the constructor throws.
CryptoSingletons.getAliroCrypto();
} catch (ISOException e) { throw e; // preserve inner diagnostic SW (0x6FC1-C5)
} catch (Throwable t) { ISOException.throwIt((short) 0x6FA6); }
// Seed P-256 curve params on every keypair before any genKeyPair / setS /
@@ -416,8 +420,9 @@ public class AliroApplet extends Applet {
switch (ins) {
case INS_DIAG_HMAC: {
AliroCrypto cryptoHmac = CryptoSingletons.getAliroCrypto();
for (short i = 0; i < n; i++) {
crypto.diagHmac(
cryptoHmac.diagHmac(
DIAG_KEY_32, (short) 0, (short) DIAG_KEY_32.length,
DIAG_MSG_64, (short) 0, (short) DIAG_MSG_64.length,
buf, DIAG_OUT_OFF);
@@ -427,8 +432,9 @@ public class AliroApplet extends Applet {
case INS_DIAG_ECDH: {
javacard.security.ECPrivateKey priv =
(javacard.security.ECPrivateKey) diagKeyPair.getPrivate();
AliroCrypto cryptoEcdh = CryptoSingletons.getAliroCrypto();
for (short i = 0; i < n; i++) {
crypto.computeEcdhSharedX(priv,
cryptoEcdh.computeEcdhSharedX(priv,
SECP256R1_G, (short) 0,
buf, DIAG_OUT_OFF);
}
@@ -652,6 +658,7 @@ public class AliroApplet extends Applet {
short saltLen = buildSaltVolatile(store, saltVolatile, (short) 0);
short infoLen = buildInfo(scratch, SCRATCH_READER_PUB_UNCOMP_OFF);
AliroCrypto crypto = CryptoSingletons.getAliroCrypto();
crypto.deriveKdh(
(ECPrivateKey) credentialEphemeralKeyPair.getPrivate(),
sessionState, OFF_READER_EPUBK,