1 files changed, 61 insertions, 0 deletions
diff --git a/ext/crypto/00_crypto.js b/ext/crypto/00_crypto.js
index 1f49d1849..81c475ad7 100644
--- a/ext/crypto/00_crypto.js
+++ b/ext/crypto/00_crypto.js
@@ -133,6 +133,7 @@
     "decrypt": {
       "RSA-OAEP": "RsaOaepParams",
       "AES-CBC": "AesCbcParams",
+      "AES-GCM": "AesGcmParams",
       "AES-CTR": "AesCtrParams",
     },
     "get key length": {
@@ -631,6 +632,66 @@
           // 4.
           return cipherText.buffer;
         }
+        case "AES-GCM": {
+          normalizedAlgorithm.iv = copyBuffer(normalizedAlgorithm.iv);
+
+          // 1.
+          if (normalizedAlgorithm.tagLength === undefined) {
+            normalizedAlgorithm.tagLength = 128;
+          } else if (
+            !ArrayPrototypeIncludes(
+              [32, 64, 96, 104, 112, 120, 128],
+              normalizedAlgorithm.tagLength,
+            )
+          ) {
+            throw new DOMException(
+              "Invalid tag length",
+              "OperationError",
+            );
+          }
+
+          // 2.
+          if (data.byteLength < normalizedAlgorithm.tagLength / 8) {
+            throw new DOMException(
+              "Tag length overflows ciphertext",
+              "OperationError",
+            );
+          }
+
+          // 3. We only support 96-bit nonce for now.
+          if (normalizedAlgorithm.iv.byteLength !== 12) {
+            throw new DOMException(
+              "Initialization vector length not supported",
+              "NotSupportedError",
+            );
+          }
+
+          // 4.
+          if (normalizedAlgorithm.additionalData !== undefined) {
+            if (normalizedAlgorithm.additionalData.byteLength > (2 ** 64) - 1) {
+              throw new DOMException(
+                "Additional data too large",
+                "OperationError",
+              );
+            }
+            normalizedAlgorithm.additionalData = copyBuffer(
+              normalizedAlgorithm.additionalData,
+            );
+          }
+
+          // 5-8.
+          const plaintext = await core.opAsync("op_crypto_decrypt", {
+            key: keyData,
+            algorithm: "AES-GCM",
+            length: key[_algorithm].length,
+            iv: normalizedAlgorithm.iv,
+            additionalData: normalizedAlgorithm.additionalData,
+            tagLength: normalizedAlgorithm.tagLength,
+          }, data);
+
+          // 9.
+          return plaintext.buffer;
+        }
         default:
           throw new DOMException("Not implemented", "NotSupportedError");
       }