fix: KMS Bad Key error when using existing Blob context to overwrite object

google-cloud-storage/src/main/java/com/google/cloud/storage/BlobInfo.java

@@ -323,9 +323,11 @@ public Builder setTimeStorageClassUpdated(Long timeStorageClassUpdated) {
     abstract Builder setCustomerEncryption(CustomerEncryption customerEncryption);
 
     /**
-     * Sets a customer-managed key for server-side encryption of the blob. Note that the kmsKeyName
-     * must be without resource id ("/cryptoKeyVersions/..") otherwise the requests will fail with a
-     * 400 Bad Request response.
+     * Sets a customer-managed key for server-side encryption of the blob.
+     *
+     * <p>Note that only KMS key name will be considered (for
+     * instance,"projects/project-id/locations/us/keyRings/lab1/cryptoKeys/test-key"), if the
+     * cryptoKeyVersions is specified it will be truncated.
      */
     abstract Builder setKmsKeyName(String kmsKeyName);
 
@@ -625,7 +627,12 @@ Builder setCustomerEncryption(CustomerEncryption customerEncryption) {
 
     @Override
     Builder setKmsKeyName(String kmsKeyName) {
-      this.kmsKeyName = kmsKeyName;
+      String cryptoKeyVersions = "/cryptoKeyVersions/";
+      if (kmsKeyName != null && kmsKeyName.contains(cryptoKeyVersions)) {
+        this.kmsKeyName = kmsKeyName.substring(0, kmsKeyName.indexOf(cryptoKeyVersions));
+      } else {
+        this.kmsKeyName = kmsKeyName;
+      }
       return this;
     }
 

google-cloud-storage/src/test/java/com/google/cloud/storage/it/ITStorageTest.java

@@ -3605,4 +3605,23 @@ public void testBlobTimeStorageClassUpdated() {
         .isEqualTo(updatedBlob1.getTimeStorageClassUpdated());
     assertThat(updatedBlob2.delete()).isTrue();
   }
+
+  @Test
+  public void testWriterWithKmsKeyName() throws IOException {
+    // Write an empty object with a kmsKeyName.
+    String blobName = "test-empty-blob";
+    BlobInfo blobInfo = BlobInfo.newBuilder(BUCKET, blobName).build();
+    Blob blob =
+        storage.create(blobInfo, Storage.BlobTargetOption.kmsKeyName(kmsKeyOneResourcePath));
+
+    // Create a writer using blob that already has metadata received from Storage API.
+    int numberOfBytes;
+    try (WriteChannel writer = blob.writer()) {
+      byte[] content = BLOB_STRING_CONTENT.getBytes(UTF_8);
+      numberOfBytes = writer.write(ByteBuffer.wrap(content, 0, content.length));
+    }
+    assertThat(numberOfBytes).isEqualTo(27);
+    assertThat(blob.getKmsKeyName()).isNotNull();
+    assertThat(storage.delete(BUCKET, blobName)).isTrue();
+  }
 }