Check structural validity of prekeys at upload time

service/src/main/java/org/whispersystems/textsecuregcm/util/ValidPreKey.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2023 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.whispersystems.textsecuregcm.util;
+
+import static java.lang.annotation.ElementType.FIELD;
+import static java.lang.annotation.ElementType.PARAMETER;
+import static java.lang.annotation.ElementType.TYPE_USE;
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+import java.lang.annotation.Documented;
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+import javax.validation.Constraint;
+import javax.validation.Payload;
+
+@Target({FIELD, PARAMETER, TYPE_USE})
+@Retention(RUNTIME)
+@Constraint(validatedBy = {ValidPreKeyValidator.class})
+@Documented
+public @interface ValidPreKey {
+
+  public enum PreKeyType {
+      ECC,
+      KYBER
+  }
+
+  PreKeyType type();
+
+  String message() default "{org.whispersystems.textsecuregcm.util.ValidPreKey.message}";
+
+  Class<?>[] groups() default { };
+
+  Class<? extends Payload>[] payload() default { };
+
+}

service/src/main/java/org/whispersystems/textsecuregcm/util/ValidPreKeyValidator.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2013-2020 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.whispersystems.textsecuregcm.util;
+
+import javax.validation.ConstraintValidator;
+import javax.validation.ConstraintValidatorContext;
+import org.signal.libsignal.protocol.InvalidKeyException;
+import org.signal.libsignal.protocol.ecc.Curve;
+import org.signal.libsignal.protocol.kem.KEMPublicKey;
+import org.whispersystems.textsecuregcm.entities.PreKey;
+
+public class ValidPreKeyValidator implements ConstraintValidator<ValidPreKey, PreKey> {
+  private ValidPreKey.PreKeyType type;
+
+  @Override
+  public void initialize(ValidPreKey annotation) {
+    type = annotation.type();
+  }
+
+  @Override
+  public boolean isValid(PreKey value, ConstraintValidatorContext context) {
+    if (value == null) {
+      return true;
+    }
+    try {
+      switch (type) {
+        case ECC -> Curve.decodePoint(value.getPublicKey(), 0);
+        case KYBER -> new KEMPublicKey(value.getPublicKey());
+      }
+    } catch (IllegalArgumentException | InvalidKeyException e) {
+      return false;
+    }
+    return true;
+  }
+}