Merge pull request #10 from highmtworks/fix-high-tag-number

Fix high tag number decoding
atesgoral · Jan 16, 2021 · 5943f8d · 5943f8d
2 parents 2688b0a + 987c1f9
commit 5943f8d
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Showing 2 changed files with 13 additions and 1 deletion.
diff --git a/index.js b/index.js
@@ -17,7 +17,7 @@ function decode(buffer) {
     do {
       byte = buffer.readUInt8(bytesRead);
       bytesRead += 1;
-      tagCode = (tagCode << 8) | (byte & 0x7f);
+      tagCode = (tagCode << 7) | (byte & 0x7f);
     } while (byte & 0x80);
   }
 

diff --git a/test/index.js b/test/index.js
@@ -50,6 +50,18 @@ test('decode: tagCode 50 (extended tag / aka high tag)', (t) => {
   );
 });
 
+test('decode: tagCode 257 (extended tag / aka high tag with three octets)', (t) => {
+  t.deepEqual(
+    asn1Tree.decode(b(tag(CLS_CONTEXT_SPECIFIC, FORM_PRIMITIVE, 31), 130, 1, 3, f(3))),
+    {
+      cls: CLS_CONTEXT_SPECIFIC,
+      form: FORM_PRIMITIVE,
+      tagCode: 257,
+      value: f(3)
+    }
+  );
+});
+
 test('decode: primitive: element with length 0', (t) => {
   t.deepEqual(
     asn1Tree.decode(b(tag(CLS_UNIVERSAL, FORM_PRIMITIVE, TAG_NULL), 0)),