OpenNHP/opennhp · error

unsupported key type, expect RSA

Error message

unsupported key type, expect RSA

What it means

parseTeePubkey only supports RSA keys when converting a TEE attestation's COSE/CBOR public key into an *rsa.PublicKey. If the key type (kty) field of the attested TEE pubkey is anything other than "RSA" (e.g. EC2/EC, OKP), attestation is rejected.

Solutions

1. Configure the TEE/attester to generate RSA keys for its attestation public key
2. Extend parseTeePubkey to handle the kty you actually use (e.g. EC2 -> ecdsa.PublicKey)
3. Verify the pubkey JSON/N/E fields come from the expected attestation format
4. Check the attestation SDK version didn't change the default key type

Example fix

// before
if pubkey.Kty != "RSA" {
    return nil, errors.New("unsupported key type, expect RSA")
}
// after
switch pubkey.Kty {
case "RSA":
    return parseRSAPubkey(pubkey)
case "EC2":
    return parseECPubkey(pubkey)
default:
    return nil, fmt.Errorf("unsupported key type: %s", pubkey.Kty)
}

pubkey, err := extractTeePubkey(evidence)
if err != nil { return err }
if pubkey.Kty != "RSA" {
    return fmt.Errorf("TEE produced %q key; configure RSA or extend parser", pubkey.Kty)
}

func isRSATeePubkey(k TeePubkey) bool { return k.Kty == "RSA" && k.N != "" && k.E != "" }

pk, err := parseTeePubkey(tp)
if err != nil {
    if strings.Contains(err.Error(), "unsupported key type") {
        log.Errorf("attester must emit RSA keys: %v", err)
    }
    return err
}

When it happens

Trigger: Attest() receives a TEE evidence token whose pubkey.kty is not "RSA" — e.g. the TEE (or its signing attester) was configured to produce EC keys, or a malformed/forged token supplies a different kty.

Common situations: Migrating confidential-computing workloads (SEV-SNP/TDX guests) that emit EC P-256 keys, upgrading attestation SDKs that changed the default key algorithm, or testing with keys generated by a crypto library defaulting to elliptic curves.

Related errors

• TEE public key is not found for specified token
• JWT signing key is not initialized
• invalid n
• invalid e
• invalid public key length: got

AI-assisted analysis of OpenNHP/opennhp@6e04ca5ff0 (2026-09-07). Data as JSON: /api/errors/a690b43fec8f5813. Report an issue: GitHub.

Appendix: source

Thrown at endpoints/server/kbs/attest/attest.go:103

	teePubKeys.Lock()
	teePubKeys.data[token] = teePubKey
	teePubKeys.Unlock()

	c.SetCookie(
		"kbs-session-id",
		sessionID,
		3600,
		"/", "", true, true, // Secure: only send over HTTPS
	)

	c.JSON(http.StatusOK, gin.H{
		"token": token,
	})
}

func parseTeePubkey(pubkey TeePubkey) (*rsa.PublicKey, error) {
	if pubkey.Kty != "RSA" {
		return nil, errors.New("unsupported key type, expect RSA")
	}

	nBytes, err := base64.RawURLEncoding.DecodeString(pubkey.N)
	if err != nil {
		return nil, fmt.Errorf("invalid n: %w", err)
	}

	eBytes, err := base64.RawURLEncoding.DecodeString(pubkey.E)
	if err != nil {
		return nil, fmt.Errorf("invalid e: %w", err)
	}

	e := 0
	for _, b := range eBytes {
		e = e<<8 | int(b)
	}

	return &rsa.PublicKey{

View on GitHub (pinned to 6e04ca5ff0)