types: Add getMechanismParam

Fixes build error triggered by miekg/pkcs11
40e115a85e0196984e45b254c509d74900738bb4

types.go

@@ -21,6 +21,11 @@ static inline CK_VOID_PTR getAttributePval(CK_ATTRIBUTE_PTR a)
 	return a->pValue;
 }
 
+static inline CK_VOID_PTR getMechanismParam(CK_MECHANISM_PTR m)
+{
+	return m->pParameter;
+}
+
 */
 import "C"
 
@@ -148,19 +153,19 @@ func toMechanism(pMechanism C.CK_MECHANISM_PTR) *pkcs11.Mechanism {
 		C.CKM_SHA384_RSA_PKCS_PSS, C.CKM_SHA512_RSA_PKCS_PSS,
 		C.CKM_SHA3_256_RSA_PKCS_PSS, C.CKM_SHA3_384_RSA_PKCS_PSS,
 		C.CKM_SHA3_512_RSA_PKCS_PSS, C.CKM_SHA3_224_RSA_PKCS_PSS:
-		pssParam := C.CK_RSA_PKCS_PSS_PARAMS_PTR(pMechanism.pParameter)
+		pssParam := C.CK_RSA_PKCS_PSS_PARAMS_PTR(C.getMechanismParam(pMechanism))
 		goHashAlg := uint(pssParam.hashAlg)
 		goMgf := uint(pssParam.mgf)
 		goSLen := uint(pssParam.sLen)
 		return pkcs11.NewMechanism(uint(pMechanism.mechanism), pkcs11.NewPSSParams(goHashAlg, goMgf, goSLen))
 	case C.CKM_AES_GCM:
-		gcmParam := C.CK_GCM_PARAMS_PTR(pMechanism.pParameter)
+		gcmParam := C.CK_GCM_PARAMS_PTR(C.getMechanismParam(pMechanism))
 		goIV := C.GoBytes(unsafe.Pointer(gcmParam.pIv), C.int(gcmParam.ulIvLen))
 		goAad := C.GoBytes(unsafe.Pointer(gcmParam.pAAD), C.int(gcmParam.ulAADLen))
 		goTag := int(gcmParam.ulTagBits)
 		return pkcs11.NewMechanism(uint(pMechanism.mechanism), pkcs11.NewGCMParams(goIV, goAad, goTag))
 	case C.CKM_RSA_PKCS_OAEP:
-		oaepParams := C.CK_RSA_PKCS_OAEP_PARAMS_PTR(pMechanism.pParameter)
+		oaepParams := C.CK_RSA_PKCS_OAEP_PARAMS_PTR(C.getMechanismParam(pMechanism))
 		goHashAlg := uint(oaepParams.hashAlg)
 		goMgf := uint(oaepParams.mgf)
 		goSourceType := uint(oaepParams.source)