Skip to content

Use constant-time comparison for output prefix verification in MAC #73

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
JACKURUVI99 wants to merge 1 commit into
base: main
Choose a base branch
from
Open

Use constant-time comparison for output prefix verification in MAC #73

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
7 changes: 5 additions & 2 deletions src/main/java/com/google/crypto/tink/mac/internal/ChunkedAesCmacImpl.java
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -22,10 +22,11 @@
import com.google.crypto.tink.mac.ChunkedMac;
import com.google.crypto.tink.mac.ChunkedMacComputation;
import com.google.crypto.tink.mac.ChunkedMacVerification;
import com.google.crypto.tink.util.Bytes;
import com.google.errorprone.annotations.Immutable;
import java.security.GeneralSecurityException;
import java.security.MessageDigest;
import java.security.Provider;
import java.util.Arrays;

/** AES-CMAC implementation of the ChunkedMac interface. */
@Immutable
Expand All @@ -52,7 +53,9 @@ public ChunkedMacVerification createVerification(final byte[] tag)
if (tag.length < key.getOutputPrefix().size()) {
throw new GeneralSecurityException("Tag too short");
}
if (!key.getOutputPrefix().equals(Bytes.copyFrom(tag, 0, key.getOutputPrefix().size()))) {
if (!MessageDigest.isEqual(
key.getOutputPrefix().toByteArray(),
Arrays.copyOf(tag, key.getOutputPrefix().size()))) {
throw new GeneralSecurityException("Wrong tag prefix");
}
return ChunkedMacVerificationFromComputation.create(new ChunkedAesCmacComputation(key), tag);
Expand Down
7 changes: 5 additions & 2 deletions src/main/java/com/google/crypto/tink/mac/internal/ChunkedHmacImpl.java
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -21,9 +21,10 @@
import com.google.crypto.tink.mac.ChunkedMacComputation;
import com.google.crypto.tink.mac.ChunkedMacVerification;
import com.google.crypto.tink.mac.HmacKey;
import com.google.crypto.tink.util.Bytes;
import com.google.errorprone.annotations.Immutable;
import java.security.GeneralSecurityException;
import java.security.MessageDigest;
import java.util.Arrays;

/** Class that provides the functionality expressed by the ChunkedMac interface with HMAC. */
@Immutable
Expand Down Expand Up @@ -53,7 +54,9 @@ public ChunkedMacVerification createVerification(final byte[] tag)
if (tag.length < key.getOutputPrefix().size()) {
throw new GeneralSecurityException("Tag too short");
}
if (!key.getOutputPrefix().equals(Bytes.copyFrom(tag, 0, key.getOutputPrefix().size()))) {
if (!MessageDigest.isEqual(
key.getOutputPrefix().toByteArray(),
Arrays.copyOf(tag, key.getOutputPrefix().size()))) {
throw new GeneralSecurityException("Wrong tag prefix");
}
return ChunkedMacVerificationFromComputation.create(new ChunkedHmacComputation(key), tag);
Expand Down
3 changes: 2 additions & 1 deletion src/main/java/com/google/crypto/tink/mac/internal/LegacyFullMac.java
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,7 @@
import com.google.crypto.tink.proto.OutputPrefixType;
import com.google.crypto.tink.subtle.Bytes;
import java.security.GeneralSecurityException;
import java.security.MessageDigest;
import java.util.Arrays;

/**
Expand Down Expand Up @@ -97,7 +98,7 @@ public void verifyMac(byte[] mac, byte[] data) throws GeneralSecurityException {
macNoPrefix = Arrays.copyOfRange(mac, CryptoFormat.NON_RAW_PREFIX_SIZE, mac.length);
}

if (!Arrays.equals(identifier, prefix)) {
if (!MessageDigest.isEqual(identifier, prefix)) {
throw new GeneralSecurityException("wrong prefix");
}

Expand Down