peass-ng/PEASS-ng · error · ArgumentException

encoding error in GetInstance:

Error message

encoding error in GetInstance: 

What it means

DerGraphicString.GetInstance() attempts to cast/decode the supplied object into a DerGraphicString. When the object is a byte[] but the ASN.1 decoding inside FromByteArray fails, the library wraps the original exception in an ArgumentException with the 'encoding error in GetInstance' prefix. This signals the bytes are not a valid DER-encoded GraphicString.

Source

Thrown at winPEAS/winPEASexe/winPEAS/3rdParty/BouncyCastle/asn1/DerGraphicString.cs:34

         * @exception IllegalArgumentException if the object cannot be converted.
         * @return a DerGraphicString instance, or null.
         */
        public static DerGraphicString GetInstance(object obj)
        {
            if (obj == null || obj is DerGraphicString)
            {
                return (DerGraphicString)obj;
            }

            if (obj is byte[])
            {
                try
                {
                    return (DerGraphicString)FromByteArray((byte[])obj);
                }
                catch (Exception e)
                {
                    throw new ArgumentException("encoding error in GetInstance: " + e.ToString(), "obj");
                }
            }

            throw new ArgumentException("illegal object in GetInstance: " + Platform.GetTypeName(obj), "obj");
        }

        /**
         * return a Graphic String from a tagged object.
         *
         * @param obj the tagged object holding the object we want
         * @param explicit true if the object is meant to be explicitly
         *              tagged false otherwise.
         * @exception IllegalArgumentException if the tagged object cannot
         *               be converted.
         * @return a DerGraphicString instance, or null.
         */
        public static DerGraphicString GetInstance(Asn1TaggedObject obj, bool isExplicit)
        {

View on GitHub (pinned to 53fb989abc)

Solutions

1. Verify the byte[] contains a valid DER-encoded value for tag GraphicString before calling GetInstance
2. Use Asn1Object.FromByteArray first and check the resulting object type before casting
3. Confirm the byte slice boundaries (offset/length) are correct and the buffer is not truncated
4. Catch ArgumentException and log the inner exception's ToString() for the underlying decode failure

Example fix

// before
var s = DerGraphicString.GetInstance(rawBytes);
// after
Asn1Object o;
if (!Asn1Object.TryGetFromByteArray(rawBytes, out o) || !(o is DerGraphicString))
    throw new InvalidDataException("not a DER GraphicString");
var s = (DerGraphicString)o;

bool IsValidDerGraphicString(byte[] data) {
    if (data == null || data.Length == 0) return false;
    try { return Asn1Object.FromByteArray(data) is DerGraphicString; }
    catch { return false; }
}

bool IsDerGraphicString(object o) => o is byte[] || o is DerGraphicString || o is Asn1TaggedObject;

try { var s = DerGraphicString.GetInstance(obj); }
catch (ArgumentException ex) { logger.Warn(ex, "GraphicString decode failed"); }

When it happens

Trigger: Calling DerGraphicString.GetInstance(object) with a byte[] whose contents fail ASN.1 parsing in FromByteArray (malformed DER, truncated data, wrong tag).

Common situations: Decoding raw bytes pulled from certificates, CRLs, or protocol fields where the buffer is corrupted, truncated, or not actually a DER GraphicString; off-by-one slicing of ASN.1 streams.

Related errors

• data
• must be in the range 0 to 7
• if 'data' is empty, 'padBits' must be 0
• attempt to get non-octet aligned data from BIT STRING
• truncated BIT STRING detected

AI-assisted analysis of peass-ng/PEASS-ng@53fb989abc (2026-09-02). Data as JSON: /api/errors/6a82e7719dde6e7b. Report an issue: GitHub.