peass-ng/PEASS-ng · error · InvalidOperationException

invalid encoding value

Error message

invalid encoding value

What it means

The DER External encoding field's tag number selects the encoding type: 0 = single-ASN1-type, 1 = octet-aligned, 2 = arbitrary. The constructor validates TagNo after reading it, and throws InvalidOperationException if it falls outside 0-2, meaning the tagged object uses a tag number undefined for External encodings.

Source

Thrown at winPEAS/winPEASexe/winPEAS/3rdParty/BouncyCastle/asn1/DerExternal.cs:55

			{
				dataValueDescriptor = enc;
				offset++;
				enc = GetObjFromVector(vector, offset);
			}

			if (vector.Count != offset + 1)
				throw new ArgumentException("input vector too large", "vector");

			if (!(enc is Asn1TaggedObject))
				throw new ArgumentException("No tagged object found in vector. Structure doesn't seem to be of type External", "vector");

			Asn1TaggedObject obj = (Asn1TaggedObject)enc;

			// Use property accessor to include check on value
			Encoding = obj.TagNo;

			if (encoding < 0 || encoding > 2)
				throw new InvalidOperationException("invalid encoding value");

			externalContent = obj.GetObject();
		}

		/**
		* Creates a new instance of DerExternal
		* See X.690 for more informations about the meaning of these parameters
		* @param directReference The direct reference or <code>null</code> if not set.
		* @param indirectReference The indirect reference or <code>null</code> if not set.
		* @param dataValueDescriptor The data value descriptor or <code>null</code> if not set.
		* @param externalData The external data in its encoded form.
		*/
		public DerExternal(DerObjectIdentifier directReference, DerInteger indirectReference, Asn1Object dataValueDescriptor, DerTaggedObject externalData)
			: this(directReference, indirectReference, dataValueDescriptor, externalData.TagNo, externalData.ToAsn1Object())
		{
		}

		/**

View on GitHub (pinned to 53fb989abc)

Solutions

1. Use TagNo 0, 1, or 2 on the tagged encoding object (explicit tagging) before constructing DerExternal
2. If parsing input data, treat this as malformed BER and reject/re-fetch the data
3. For custom content, wrap it correctly: new DerTaggedObject(true, 0, content) rather than an arbitrary tag

Example fix

// before
var bad = new DerTaggedObject(true, 5, content); // TagNo 5
var ext = new DerExternal(vector);
// after
var good = new DerTaggedObject(true, 0, content); // valid encoding tag
var ext = new DerExternal(vector);

var tag = ((Asn1TaggedObject)vector[vector.Count - 1]).TagNo;
if (tag < 0 || tag > 2)
    throw new FormatException($"External encoding tag {tag} out of range 0-2");
var ext = new DerExternal(vector);

static bool IsValidEncodingTag(Asn1TaggedObject o) => o.TagNo >= 0 && o.TagNo <= 2;

try { var ext = new DerExternal(vector); }
catch (InvalidOperationException ex) when (ex.Message == "invalid encoding value") {
    // tagged encoding uses an unsupported tag number
}

When it happens

Trigger: Constructing DerExternal from a vector whose final Asn1TaggedObject has TagNo < 0 or > 2.

Common situations: Decoding BER data with a non-standard or application-specific tag used where an External encoding tag is expected; hand-built tagged objects with the wrong tag number; protocol implementations that mis-encode the External content.

Related errors

• malformed object
• must be in the range 0 to 7
• if 'data' is empty, 'padBits' must be 0
• ENUMERATED has zero length
• input vector too large

AI-assisted analysis of peass-ng/PEASS-ng@53fb989abc (2026-09-02). Data as JSON: /api/errors/ce6511a2aa874d0f. Report an issue: GitHub.