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Support for fetching extra global security state via the extension of SecurityStateManager#getGlobalSecurityState() API downstream #282

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Support for fetching extra global security state via the extension of SecurityStateManager#getGlobalSecurityState() API downstream #282

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d9e396a
Cleanup unused import
quh4gko8 Oct 1, 2024
44b57a8
Refactor brace placements for empty record classes in AttestationProt…
quh4gko8 Jan 7, 2025
dfc295c
Method to check for having pogo pins in record classes with device name
quh4gko8 Jan 7, 2025
b0e3b7e
Store auto reboot timeout field in seconds for attestation protocol v6+
quh4gko8 Jan 6, 2025
bfc1c9d
Record class for extended security state extension for protocol v6+
quh4gko8 Oct 1, 2024
d8f29f9
Fetch extended security states from global security state
quh4gko8 Oct 1, 2024
34a16bd
Support overriding OS enforced flags based on extended security states
quh4gko8 Oct 1, 2024
a79c3b8
Override OEM unlock check with extended security state flag if present
quh4gko8 Oct 1, 2024
54331f3
Include extended security state values for serialization
quh4gko8 Sep 30, 2024
69bea16
Deserialize extended security state for attestation protocol v6+
quh4gko8 Jan 7, 2025
1a7e607
Display extended security state extensions from attestation protocol v6+
quh4gko8 Jan 7, 2025
66cf9bc
Add separate manifest for merging in release build variant
quh4gko8 Sep 29, 2024
30bacab
Increment protocol version to 6
quh4gko8 Oct 1, 2024
b1206b7
Revert "Override OEM unlock check with downstream security state flag…
quh4gko8 Oct 1, 2024
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217 changes: 200 additions & 17 deletions app/src/main/java/app/attestation/auditor/AttestationProtocol.java
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,8 @@
import android.content.pm.ApplicationInfo;
import android.content.pm.PackageManager;
import android.os.Build;
import android.os.Bundle;
import android.os.SecurityStateManager;
import android.os.UserManager;
import android.provider.Settings;
import android.security.keystore.KeyGenParameterSpec;
Expand Down Expand Up @@ -52,19 +54,19 @@
import java.security.cert.CertificateFactory;
import java.security.cert.X509Certificate;
import java.security.spec.ECGenParameterSpec;
import java.time.Duration;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Date;
import java.util.Enumeration;
import java.util.List;
import java.util.Locale;
import java.util.concurrent.TimeUnit;
import java.util.zip.DataFormatException;
import java.util.zip.Deflater;
import java.util.zip.DeflaterOutputStream;
import java.util.zip.Inflater;

import javax.security.auth.x500.X500Principal;

import app.attestation.auditor.attestation.AttestationApplicationId;
import app.attestation.auditor.attestation.AttestationApplicationId.AttestationPackageInfo;
import app.attestation.auditor.attestation.AuthorizationList;
Expand Down Expand Up @@ -147,15 +149,15 @@ class AttestationProtocol {
// byte[] compressedChain { [short encodedCertificateLength, byte[] encodedCertificate] }
// byte[] fingerprint (length: FINGERPRINT_LENGTH)
// int osEnforcedFlags
// short autoRebootMinutes (-1 for unknown)
// int autoRebootSeconds (-1 for unknown)
// byte portSecurityMode (-1 for unknown)
// byte userCount (-1 for unknown)
// }
// byte[] signature (rest of message)
//
// Protocol version changes:
//
// 6: autoRebootMinutes added
// 6: autoRebootSeconds added
// 6: portSecurityMode added
// 6: userCount added
//
Expand Down Expand Up @@ -197,7 +199,7 @@ class AttestationProtocol {
// the outer signature and the rest of the chain for pinning the expected chain. It enforces
// downgrade protection for the OS version/patch (bootloader/TEE enforced) and app version (OS
// enforced) by keeping them updated.
private static final byte PROTOCOL_VERSION = 5;
private static final byte PROTOCOL_VERSION = 6;
private static final byte PROTOCOL_VERSION_MINIMUM = 5;
// can become longer in the future, but this is the minimum length
static final byte CHALLENGE_MESSAGE_LENGTH = 1 + RANDOM_TOKEN_LENGTH * 2;
Expand Down Expand Up @@ -252,7 +254,12 @@ class AttestationProtocol {
public record DeviceInfo(int name, int attestationVersion, int keymasterVersion,
// API for detecting this was replaced in keymaster v3 but the new one isn't used yet
boolean rollbackResistant,
boolean enforceStrongBox, int osName) {}
boolean enforceStrongBox, int osName) {

boolean hasPogoPins() {
return name == R.string.device_pixel_tablet;
}
}

private static final boolean isStrongBoxSupported = ImmutableSet.of(
"Pixel 3",
Expand Down Expand Up @@ -553,7 +560,12 @@ private static byte[] getFingerprint(final Certificate certificate)

private record Verified(int device, String verifiedBootKey, byte[] verifiedBootHash,
int osName, int osVersion, int osPatchLevel, int vendorPatchLevel, int bootPatchLevel,
int appVersion, int appVariant, int securityLevel, boolean attestKey) {}
int appVersion, int appVariant, int securityLevel, boolean attestKey) {

boolean hasPogoPins() {
return device == R.string.device_pixel_tablet;
}
}

private static X509Certificate generateCertificate(final InputStream in)
throws CertificateException {
Expand Down Expand Up @@ -939,19 +951,28 @@ private static void verifySignature(final PublicKey key, final ByteBuffer messag
}
}

record VerificationResult(boolean strong, String teeEnforced, String osEnforced, String history) {}
record VerificationResult(boolean strong, String teeEnforced, String osEnforced, String history) {
}

private static String toYesNoString(final Context context, final boolean value) {
return value ? context.getString(R.string.yes) : context.getString(R.string.no);
}

record SecurityStateExt(int autoRebootSeconds, byte portSecurityMode, byte userCount) {
static int UNKNOWN_VALUE = -1;
static int INVALID_VALUE = -2;
static SecurityStateExt UNKNOWN = new SecurityStateExt(
UNKNOWN_VALUE, (byte) UNKNOWN_VALUE, (byte) UNKNOWN_VALUE);
}

private static VerificationResult verify(final Context context, final byte[] fingerprint,
final byte[] challenge, final ByteBuffer signedMessage, final byte[] signature,
final Certificate[] attestationCertificates, final boolean userProfileSecure,
final boolean accessibility, final boolean deviceAdmin,
final boolean deviceAdminNonSystem, final boolean adbEnabled,
final boolean addUsersWhenLocked, final boolean enrolledBiometrics,
final boolean oemUnlockAllowed, final boolean systemUser)
final boolean oemUnlockAllowed, final boolean systemUser,
SecurityStateExt securityStateExt)
throws GeneralSecurityException {
final String fingerprintHex = BaseEncoding.base16().encode(fingerprint);
final byte[] currentFingerprint = getFingerprint(attestationCertificates[0]);
Expand Down Expand Up @@ -1127,6 +1148,103 @@ private static VerificationResult verify(final Context context, final byte[] fin
osEnforced.append(context.getString(R.string.system_user,
toYesNoString(context, systemUser)));

final int usbcPortSecurityModePrefix;
if (verified.hasPogoPins()) {
usbcPortSecurityModePrefix = R.string.usbc_port_and_pogo_pins;
} else {
usbcPortSecurityModePrefix = R.string.usbc_port_security_mode;
}

final int usbcPortSecurityModeOffRes;
if (verified.hasPogoPins()) {
usbcPortSecurityModeOffRes = R.string.usbc_port_and_pogo_pins_security_mode_off;
} else {
usbcPortSecurityModeOffRes = R.string.usbc_port_security_mode_off;
}

final byte usbcPortSecurityMode = securityStateExt.portSecurityMode();
final int usbcPortSecurityModeValueRes;
if (usbcPortSecurityMode == SecurityStateExt.UNKNOWN_VALUE) {
usbcPortSecurityModeValueRes = R.string.unknown_value;
} else if (usbcPortSecurityMode == SecurityStateExt.INVALID_VALUE) {
usbcPortSecurityModeValueRes = R.string.invalid_value;
} else {
usbcPortSecurityModeValueRes = switch (usbcPortSecurityMode) {
case 0 -> usbcPortSecurityModeOffRes;
case 1 -> R.string.usbc_port_security_mode_charging_only;
case 2 -> R.string.usbc_port_security_mode_charging_only_when_locked;
case 3 -> R.string.usbc_port_security_mode_charging_only_when_locked_afu;
case 4 -> R.string.usbc_port_security_mode_on;
default -> throw new IllegalArgumentException();
};
}
osEnforced.append(context.getString(usbcPortSecurityModePrefix,
context.getString(usbcPortSecurityModeValueRes)));

final int autoRebootSeconds = securityStateExt.autoRebootSeconds();
final String autoRebootValueString;
if (autoRebootSeconds == SecurityStateExt.UNKNOWN_VALUE) {
autoRebootValueString = context.getString(R.string.unknown_value);
} else if (autoRebootSeconds == SecurityStateExt.INVALID_VALUE) {
autoRebootValueString = context.getString(R.string.invalid_value);
} else {
final Duration duration = Duration.ofSeconds(autoRebootSeconds);
StringBuilder autoRebootValueStrBuilder = new StringBuilder();

long hoursDuration = duration.toHours();
if (hoursDuration > 1) {
autoRebootValueStrBuilder.append(
context.getString(R.string.auto_reboot_hours_plural_value, hoursDuration));
} else if (hoursDuration == 1) {
autoRebootValueStrBuilder.append(
context.getString(R.string.auto_reboot_hours_singular_value));
}

int minutesPart = duration.toMinutesPart();
if (minutesPart > 1) {
if (autoRebootValueStrBuilder.length() != 0) {
autoRebootValueStrBuilder.append(", ");
}
autoRebootValueStrBuilder.append(
context.getString(R.string.auto_reboot_minutes_plural_value, minutesPart));
} else if (minutesPart == 1) {
if (autoRebootValueStrBuilder.length() != 0) {
autoRebootValueStrBuilder.append(", ");
}
autoRebootValueStrBuilder.append(
context.getString(R.string.auto_reboot_minutes_singular_value));
}

int secondsPart = duration.toSecondsPart();
if (secondsPart > 1) {
if (autoRebootValueStrBuilder.length() != 0) {
autoRebootValueStrBuilder.append(", ");
}
autoRebootValueStrBuilder.append(
context.getString(R.string.auto_reboot_seconds_plural_value, secondsPart));
} else if (secondsPart == 1) {
if (autoRebootValueStrBuilder.length() != 0) {
autoRebootValueStrBuilder.append(", ");
}
autoRebootValueStrBuilder.append(
context.getString(R.string.auto_reboot_seconds_singular_value));
}

autoRebootValueString = autoRebootValueStrBuilder.toString();
}
osEnforced.append(context.getString(R.string.auto_reboot_timeout, autoRebootValueString));

final byte userCount = securityStateExt.userCount();
final String userCountValueString;
if (userCount == SecurityStateExt.UNKNOWN_VALUE) {
userCountValueString = context.getString(R.string.unknown_value);
} else if (userCount == SecurityStateExt.INVALID_VALUE) {
userCountValueString = context.getString(R.string.invalid_value);
} else {
userCountValueString = String.valueOf(securityStateExt.userCount());
}
osEnforced.append(context.getString(R.string.user_count, userCountValueString));

return new VerificationResult(hasPersistentKey, teeEnforced.toString(), osEnforced.toString(), history.toString());
}

Expand Down Expand Up @@ -1224,10 +1342,14 @@ static VerificationResult verifySerialized(final Context context, final byte[] a
throw new GeneralSecurityException("invalid device administrator state");
}

final SecurityStateExt securityStateExt;
if (version >= 6) {
final short autoRebootMinutes = deserializer.getShort();
final int autoRebootSeconds = deserializer.getInt();
final byte portSecurityMode = deserializer.get();
final byte userCount = deserializer.get();
securityStateExt = new SecurityStateExt(autoRebootSeconds, portSecurityMode, userCount);
} else {
securityStateExt = SecurityStateExt.UNKNOWN;
}

final int signatureLength = deserializer.remaining();
Expand All @@ -1240,10 +1362,12 @@ static VerificationResult verifySerialized(final Context context, final byte[] a
final byte[] challenge = Arrays.copyOfRange(challengeMessage, 1 + RANDOM_TOKEN_LENGTH, 1 + RANDOM_TOKEN_LENGTH * 2);
return verify(context, fingerprint, challenge, deserializer.asReadOnlyBuffer(), signature,
certificates, userProfileSecure, accessibility, deviceAdmin, deviceAdminNonSystem,
adbEnabled, addUsersWhenLocked, enrolledBiometrics, oemUnlockAllowed, systemUser);
adbEnabled, addUsersWhenLocked, enrolledBiometrics, oemUnlockAllowed, systemUser,
securityStateExt);
}

record AttestationResult(boolean pairing, byte[] serialized) {}
record AttestationResult(boolean pairing, byte[] serialized) {
}

static KeyGenParameterSpec.Builder getKeyBuilder(final String alias, final int purposes,
final boolean useStrongBox, final byte[] challenge, final boolean temporary) {
Expand Down Expand Up @@ -1433,6 +1557,35 @@ static AttestationResult generateSerialized(final Context context, final byte[]
final UserManager userManager = context.getSystemService(UserManager.class);
final boolean systemUser = userManager.isSystemUser();

final Bundle extraSecurityState;
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.VANILLA_ICE_CREAM) {
SecurityStateManager securityStateManager =
context.getSystemService(SecurityStateManager.class);

if (securityStateManager != null) {
Bundle extraSecurityStateTmp = Bundle.EMPTY;
try {
Bundle globalSecurityState = securityStateManager.getGlobalSecurityState();
String securityStateExtKey = "android.ext.SECURITY_STATE_EXT";
extraSecurityStateTmp = globalSecurityState.getBundle(securityStateExtKey);
} catch (SecurityException e) {
Log.e(TAG, "", e);
String message = e.getMessage();
if (message == null || !message.startsWith("get package info")
|| !message.endsWith("requires "
+ "android.permission.INTERACT_ACROSS_USERS_FULL or "
+ "android.permission.INTERACT_ACROSS_USERS to access user 0.")) {
throw new GeneralSecurityException(e);
}
}
extraSecurityState = extraSecurityStateTmp != null ? extraSecurityStateTmp : Bundle.EMPTY;
} else {
extraSecurityState = Bundle.EMPTY;
}
} else {
extraSecurityState = Bundle.EMPTY;
}

// Serialization

final ByteBuffer serializer = ByteBuffer.allocate(MAX_MESSAGE_SIZE);
Expand Down Expand Up @@ -1483,16 +1636,46 @@ static AttestationResult generateSerialized(final Context context, final byte[]
if (systemUser) {
osEnforcedFlags |= OS_ENFORCED_FLAGS_SYSTEM_USER;
}
if (extraSecurityState != Bundle.EMPTY) {
}
serializer.putInt(osEnforcedFlags);

if (version >= 6) {
final short autoRebootMinutes = 0;
serializer.putShort(autoRebootMinutes);

final byte portSecurityMode = 0;
String autoRebootTimeoutKey = "android.ext.AUTO_REBOOT_TIMEOUT";
final int autoRebootMilliseconds =
extraSecurityState.getInt(autoRebootTimeoutKey, SecurityStateExt.UNKNOWN_VALUE);
final int autoRebootSeconds;
if (autoRebootMilliseconds == SecurityStateExt.UNKNOWN_VALUE) {
autoRebootSeconds = SecurityStateExt.UNKNOWN_VALUE;
} else if (autoRebootMilliseconds < TimeUnit.SECONDS.toMillis(20)) {
autoRebootSeconds = SecurityStateExt.INVALID_VALUE;
} else {
autoRebootSeconds = (int) (Math.ceil((double) autoRebootMilliseconds / TimeUnit.SECONDS.toMillis(1)));
}
serializer.putInt(autoRebootSeconds);

String portSecurityModeKey = "android.ext.USB_PORT_SECURITY_MODE";
final int portSecurityModeRaw = extraSecurityState.getInt(portSecurityModeKey, SecurityStateExt.UNKNOWN_VALUE);
final byte portSecurityMode;
if (portSecurityModeRaw == SecurityStateExt.UNKNOWN_VALUE) {
portSecurityMode = (byte) SecurityStateExt.UNKNOWN_VALUE;
} else if (portSecurityModeRaw > Byte.MAX_VALUE || portSecurityModeRaw < 0) {
portSecurityMode = (byte) SecurityStateExt.INVALID_VALUE;
} else {
portSecurityMode = (byte) portSecurityModeRaw;
}
serializer.put(portSecurityMode);

final byte userCount = 0;
String userCountKey = "android.ext.USER_COUNT";
final int userCountRaw = extraSecurityState.getInt(userCountKey, SecurityStateExt.UNKNOWN_VALUE);
final byte userCount;
if (userCountRaw == SecurityStateExt.UNKNOWN_VALUE) {
userCount = (byte) SecurityStateExt.UNKNOWN_VALUE;
} else if (userCountRaw > Byte.MAX_VALUE || userCountRaw < 0) {
userCount = (byte) SecurityStateExt.INVALID_VALUE;
} else {
userCount = (byte) userCountRaw;
}
serializer.put(userCount);
}

Expand Down
22 changes: 22 additions & 0 deletions app/src/main/res/values/strings.xml
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Original file line number Diff line number Diff line change
Expand Up @@ -86,6 +86,28 @@
<string name="add_users_when_locked">Add users from lock screen: %s\n</string>
<string name="oem_unlock_allowed">OEM unlocking allowed: %s\n</string>
<string name="system_user">Main user account: %s\n</string>
<string name="auto_reboot_timeout">Auto reboot timeout: %s\n</string>
<string name="auto_reboot_seconds_plural_value">%d seconds</string>
<string name="auto_reboot_minutes_plural_value">%d minutes</string>
<string name="auto_reboot_hours_plural_value">%d hours</string>
<string name="auto_reboot_seconds_singular_value">1 second</string>
<string name="auto_reboot_minutes_singular_value">1 minute</string>
<string name="auto_reboot_hours_singular_value">1 hour</string>

<string name="usbc_port_security_mode">USB-C port security mode: %s\n</string>
<string name="usbc_port_and_pogo_pins">USB-C port and pogo pins security mode: %s\n</string>

<string name="usbc_port_security_mode_off">Off</string>
<string name="usbc_port_and_pogo_pins_security_mode_off">USB-C port off, pogo pins used only for charging</string>
<string name="usbc_port_security_mode_charging_only">Charging-only</string>
<string name="usbc_port_security_mode_charging_only_when_locked">Charging-only when locked</string>
<string name="usbc_port_security_mode_charging_only_when_locked_afu">Charging-only when locked, except before first unlock</string>
<string name="usbc_port_security_mode_on">On</string>

<string name="user_count">User count: %s\n</string>

<string name="unknown_value">Unknown</string>
<string name="invalid_value">Invalid</string>

<string name="history">\n<b>Attestation history:</b>\n\n</string>
<string name="first_verified">First verified: %s\n</string>
Expand Down
9 changes: 9 additions & 0 deletions app/src/release/AndroidManifest.xml
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Original file line number Diff line number Diff line change
@@ -0,0 +1,9 @@
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools">

<uses-permission android:name="android.permission.READ_ADDITIONAL_SECURITY_STATE"
android:minSdkVersion="35"
tools:node="merge"/>

</manifest>
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