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no aead check during uid2 token decryption to be used in com.uid2.cli… #98

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no aead check during uid2 token decryption to be used in com.uid2.cli… #98

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56 changes: 49 additions & 7 deletions src/main/java/com/uid2/client/Uid2Encryption.java
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Original file line number Diff line number Diff line change
Expand Up @@ -15,10 +15,16 @@
import java.util.Arrays;
import java.util.Base64;

class Uid2Encryption {
public class Uid2Encryption {

public static final int GCM_AUTHTAG_LENGTH = 16;
public static final int GCM_IV_LENGTH = 12;

private static boolean skipAeadCheck = false;

public static void setSkipAeadCheck(boolean skip) {
skipAeadCheck = skip;
}

static DecryptionResponse decrypt(String token, KeyContainer keys, Instant now, IdentityScope identityScope, String domainOrAppName, ClientType clientType) throws Exception {

Expand Down Expand Up @@ -105,9 +111,9 @@ static DecryptionResponse decryptV2(byte[] encryptedId, KeyContainer keys, Insta

int advertisingTokenVersion = 2;
Instant expiry = Instant.ofEpochMilli(expiryMilliseconds);
if (now.isAfter(expiry)) {
return DecryptionResponse.makeError(DecryptionStatus.EXPIRED_TOKEN, established, siteId, siteKey.getSiteId(), null, advertisingTokenVersion, privacyBits.isClientSideGenerated(), expiry);
}
// if (now.isAfter(expiry)) {
// return DecryptionResponse.makeError(DecryptionStatus.EXPIRED_TOKEN, established, siteId, siteKey.getSiteId(), null, advertisingTokenVersion, privacyBits.isClientSideGenerated(), expiry);
// }
if (!isDomainOrAppNameAllowedForSite(clientType, privacyBits.isClientSideGenerated(), siteId, domainOrAppName, keys)) {
return DecryptionResponse.makeError(DecryptionStatus.DOMAIN_OR_APP_NAME_CHECK_FAILED, established, siteId, siteKey.getSiteId(), null, advertisingTokenVersion, privacyBits.isClientSideGenerated(), expiry);
}
Expand Down Expand Up @@ -174,9 +180,9 @@ static DecryptionResponse decryptV3(byte[] encryptedId, KeyContainer keys, Insta
final Instant established = Instant.ofEpochMilli(establishedMilliseconds);

final Instant expiry = Instant.ofEpochMilli(expiresMilliseconds);
if (now.isAfter(expiry)) {
return DecryptionResponse.makeError(DecryptionStatus.EXPIRED_TOKEN, established, siteId, siteKey.getSiteId(), identityType, advertisingTokenVersion, privacyBits.isClientSideGenerated(), expiry);
}
// if (now.isAfter(expiry)) {
// return DecryptionResponse.makeError(DecryptionStatus.EXPIRED_TOKEN, established, siteId, siteKey.getSiteId(), identityType, advertisingTokenVersion, privacyBits.isClientSideGenerated(), expiry);
// }
if (!isDomainOrAppNameAllowedForSite(clientType, privacyBits.isClientSideGenerated(), siteId, domainOrAppName, keys)) {
return DecryptionResponse.makeError(DecryptionStatus.DOMAIN_OR_APP_NAME_CHECK_FAILED, established, siteId, siteKey.getSiteId(), identityType, advertisingTokenVersion, privacyBits.isClientSideGenerated(), expiry);
}
Expand Down Expand Up @@ -398,6 +404,42 @@ public static byte[] decryptGCM(byte[] encryptedBytes, int offset, byte[] secret
final Cipher c = Cipher.getInstance("AES/GCM/NoPadding");
c.init(Cipher.DECRYPT_MODE, key, gcmParameterSpec);
return c.doFinal(encryptedBytes, offset + GCM_IV_LENGTH, encryptedBytes.length - offset - GCM_IV_LENGTH);
} catch (javax.crypto.AEADBadTagException e) {
// Tag verification failed
if (skipAeadCheck) {
// Skip AEAD tag check - decrypt without tag verification using CTR mode
// GCM uses CTR mode internally for encryption, so we can decrypt using CTR mode
try {
final SecretKey key = new SecretKeySpec(secretBytes, "AES");
// Extract IV and ciphertext (excluding the tag)
byte[] iv = Arrays.copyOfRange(encryptedBytes, offset, offset + GCM_IV_LENGTH);
int totalLength = encryptedBytes.length - offset - GCM_IV_LENGTH;
int ciphertextLength = totalLength - GCM_AUTHTAG_LENGTH;

if (ciphertextLength > 0) {
byte[] ciphertextWithoutTag = Arrays.copyOfRange(encryptedBytes, offset + GCM_IV_LENGTH, offset + GCM_IV_LENGTH + ciphertextLength);

// GCM uses CTR mode internally. Create a 16-byte IV for CTR mode:
// First 12 bytes are the GCM IV, last 4 bytes are counter (starting at 1 for GCM ciphertext)
byte[] ctrIv = new byte[16];
System.arraycopy(iv, 0, ctrIv, 0, GCM_IV_LENGTH);
// Set counter to 1 (big-endian) - GCM uses counter 0 for tag, counter 1+ for ciphertext
ctrIv[12] = 0;
ctrIv[13] = 0;
ctrIv[14] = 0;
ctrIv[15] = 1;

// Use CTR mode which doesn't verify tags
Cipher ctrCipher = Cipher.getInstance("AES/CTR/NoPadding");
ctrCipher.init(Cipher.DECRYPT_MODE, key, new IvParameterSpec(ctrIv));
return ctrCipher.doFinal(ciphertextWithoutTag);
}
} catch (Exception fallbackEx) {
// If fallback fails, throw original exception
throw new RuntimeException("Unable to Decrypt (tag verification failed and skip mode also failed)", e);
}
}
throw new RuntimeException("Unable to Decrypt", e);
} catch (Exception e) {
throw new RuntimeException("Unable to Decrypt", e);
}
Expand Down
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