[fix] respect @unused_bits in BitString (#323)

kares · kares · commit ea0625384dd9 · 2025-01-09T14:17:23.000+01:00
diff --git a/src/main/java/org/jruby/ext/openssl/ASN1.java b/src/main/java/org/jruby/ext/openssl/ASN1.java
@@ -1678,13 +1678,10 @@ private ASN1Encodable toASN1Primitive(final ThreadContext context) {
             }
             if ( type == DERBitString.class ) {
                 final byte[] data = val.asString().getBytes();
-                int padBits = 0; // padBits < 8 && padBits >= 0
-                for (int i = (data.length - 1); i > -1; i--) {
-                    int b = Byte.toUnsignedInt(data[i]);
-                    if (b != 0) {
-                        padBits = Integer.numberOfTrailingZeros(b);
-                        break;
-                    }
+                int padBits = 0;
+                IRubyObject unused_bits = getInstanceVariable("@unused_bits");
+                if (unused_bits != null) {
+                    padBits = unused_bits.convertToInteger("to_i").getIntValue();
                 }
                 return new DERBitString(data, padBits);
             }
diff --git a/src/test/ruby/test_asn1.rb b/src/test/ruby/test_asn1.rb
@@ -1189,6 +1189,16 @@ def test_bitstring
     #}
   end
 
+  def test_bit_string_unused_length
+    asn = "\x00\x04".b
+    asn.prepend "\x03#{asn.bytesize.chr}"
+    bs = OpenSSL::ASN1.decode(asn)
+    assert_equal asn, bs.to_der
+
+    bs.unused_bits = 6
+    assert_equal "\x03\x02\x06\x00", bs.to_der
+  end
+
   def test_bit_string_infinite_length
     begin
       content = [ OpenSSL::ASN1::BitString.new("\x01"), OpenSSL::ASN1::EndOfContent.new() ]

Original file line number	Diff line number	Diff line change
`@@ -1678,13 +1678,10 @@ private ASN1Encodable toASN1Primitive(final ThreadContext context) {`
`1678`	`1678`	`}`
`1679`	`1679`	`if ( type == DERBitString.class ) {`
`1680`	`1680`	`final byte[] data = val.asString().getBytes();`
`1681`		`- int padBits = 0; // padBits < 8 && padBits >= 0`
`1682`		`- for (int i = (data.length - 1); i > -1; i--) {`
`1683`		`- int b = Byte.toUnsignedInt(data[i]);`
`1684`		`- if (b != 0) {`
`1685`		`- padBits = Integer.numberOfTrailingZeros(b);`
`1686`		`- break;`
`1687`		`- }`
	`1681`	`+ int padBits = 0;`
	`1682`	`+ IRubyObject unused_bits = getInstanceVariable("@unused_bits");`
	`1683`	`+ if (unused_bits != null) {`
	`1684`	`+ padBits = unused_bits.convertToInteger("to_i").getIntValue();`
`1688`	`1685`	`}`
`1689`	`1686`	`return new DERBitString(data, padBits);`
`1690`	`1687`	`}`